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Nightshades have a reputation as bad actors in a variety of chronic conditions, such as arthritis, fibromyalgia, and IBS. But what do we really know about how these foods affect our health?

Meet the nightshade (solanaceae) family

• Tomatoes
• Tomatillos
• Eggplant
• Potatoes
• Goji Berries
• Tobacco
• Peppers (bell peppers, chili peppers, paprika, tamales, tomatillos, pimentos, cayenne, etc)

At first glance, the nightshades may look like a random collection of foods that couldn’t possibly be related. However, every nightshade plant produces fruits that all sport that same adorable little green elfish hat. Of the foods above, only tomatoes, eggplants, goji berries and peppers are “fruits” (the potato is a tuber and tobacco is a leaf). The fruits of potato and tobacco plants wear the same telltale hat, but we don’t eat the fruits of those plants.

Glycoalkaloids

Glycoalkaloids are natural pesticides produced by nightshade plants. Glycoalkaloids are bitter compounds which are found throughout the plant, but their concentrations are especially high in leaves, flowers, and unripe fruits. They are there to defend plants against bacteria, fungi, viruses, and insects.

Cherries, apples, and sugar beets also contain small amounts of glycoalkaloid even though they are not nightshades.

Vegetable violence

Glycoalkaloids act as invisible hand grenades. They bind strongly to the cholesterol in the cell membranes of predators, and in so doing, they disrupt the structure of those membranes, causing cells to leak or burst open upon contact.

Glycoalkaloids are neurotoxins. They block the enzyme cholinesterase. This enzyme is responsible for breaking down acetylcholine, a vital neurotransmitter that carries signals between nerve cells and muscle cells. When this important enzyme is blocked, acetylcholine can accumulate and electrically overstimulate the predator’s muscle cells. This can lead to paralysis, convulsions, respiratory arrest, and death. Military “nerve gases” work exactly the same way.

Ok, so glycoalkaloids are clearly nightmarish compounds for the cells of tiny creatures daring to munch upon nightshade plants, but what do we know about their effects on human health?

Nightshade glycoalkaloid health “benefits”

Health benefits? From a pesticide? Hmmm . . .

Since most people believe plant compounds are good for humans, when scientists conduct experiments with plant extracts, they are more likely to look for health benefits than health risks.

Glycoalkaloids are anti-inflammatory. Glycoalkaloids have been shown to reduce inflammation in laboratory animals. This is likely due to the fact that glycoalkaloids are structurally similar to compounds called glucocorticoids, which have well-known anti-inflammatory properties. Familiar examples of glucocorticoids include cortisol (our body’s natural stress hormone), and Prednisone, a commonly-prescribed anti-inflammatory medicine. It should be noted, however, that just because glycoalkaloids or glucocorticoids can reduce inflammation doesn’t mean they are always good for you. Prednisone is not something most of us should be taking every day, because it has numerous damaging side effects, and elevated levels of natural cortisol in our bodies weaken our immune system and slow our metabolism.

Glycoalkaloids kill bacteria and viruses. It should also not be surprising that glycoalkaloids have been shown in laboratory studies to possess antibiotic and antiviral properties, since this is what nature designed them for.

Glycoalkaloids have anti-cancer properties. In laboratory (in vitro) studies, glycoalkaloids can trigger cancer cells to self-destruct. This process is called “apoptosis.” Unfortunately, they can also cause healthy non-cancerous cells to do the same thing. Cancer studies in live animals and humans (in vivo) have not yet been conducted. The problem with so many anti-cancer plant compounds is that they are double-edged swords, killing both cancer cells and healthy cells alike:

“The undifferentiating destruction of both cancer and noncancerous cell lines . . . leads to questions of therapeutic uses of glycoalkaloids due to safety considerations. However, it is difficult to translate the results of an in vivo trial in vitro. Therefore, both animal and human experiments are essential to confirm or disprove the in vivo data observed in these studies.” [Milner 2011].

Health risks of nightshade glycoalkaloids

• Glycoalkaloids destroy cell membranes. Research has shown that glycoalkaloids can burst open the membranes of red blood cells and mitochondria (our cells’ energy generators). Some scientists have wondered whether glycoalkaloids could be one potential cause for ‘leaky gut’ syndromes due to their ability to poke holes in cells:

“Glycoalkaloids, normally available while eating potatoes, embed themselves and disrupt epithelial barrier integrity in a dose-dependent fashion in both cell culture models and in sheets of mammalian intestine. . . . [A]nimals with the genetic predisposition to develop IBD, demonstrated a greater degree of small intestinal epithelial barrier disruption and inflammation when their epithelium was exposed to the potato glycoalkaloids chaconine and solanine.” [Patel 2002]

• Glycoalkaloids cause birth defects in laboratory animals.

Nightshades and mental health

Due to widespread pro-plant food bias, the vast majority of scientific studies of nightshades explore their potential benefits rather than their downsides, so we do not have the studies we wish to have about how these interesting foods actually affect our well-being.

However, there have been plenty of documented cases of nightshade toxicity that demonstrate to us how poisonous they can be to our central nervous system—capable of causing severe neuropsychiatric side effects in human beings:

“In cases of mild glycoalkaloid poisoning symptoms include headache, vomiting, and diarrhea. Neurological symptoms were also reported, including apathy, restlessness, drowsiness, mental confusion, rambling, incoherence, stupor, hallucinations, dizziness, trembling, and visual disturbances.” [Milner 2011]

In a group of children who suffered from solanine poisoning as a result of eating potatoes that had been in storage for too long, severe psychiatric side effects were observed:

“The largest series of solanine poisoning involved an English day school where 78 schoolboys developed diarrhea and vomiting after eating potatoes stored since the summer term. Symptoms began 7-19 hours after ingestion with vomiting, diarrhea, anorexia, and malaise. Of the 78 boys, 17 were admitted to the hospital. Other symptoms included fever (88%), altered mental status (drowsiness, confusion, delirium) (82%), restlessness (47%), headache (29%), and hallucinations (23%). Three boys were seriously ill with hypotension, tachycardia [rapid heart rate], and stupor out of proportion to fluid and electrolyte imbalance. These boys were discharged 6-11 days after admission, and they had nonspecific symptoms and visual blurring for several weeks after release from the hospital.” [Barceloux 2009]

Keep in mind that these reactions just happened to be recorded due to their severity. We have no documented information about how everyday consumption of nightshades affects sensitive individuals, only numerous on-line personal accounts of mental health problems such as anxiety, panic, and insomnia that were alleviated by removal of nightshades from the diet. I personally experience profound insomnia and mild panic symptoms when I eat nightshades, which makes sense because glycoalkaloids overstimulate the nervous system.

If you experience anxiety or insomnia and are curious to know more about nightshades and the other foods most likely to be contributing to your symptoms, I recommend you read my Psychology Today article “5 Foods Proven to Cause Anxiety and Insomnia.”

Fruits vs vegetables: here we go again!

Those of you who are familiar with my philosophy about plant foods know that I believe that when it comes to our health, vegetables are far less trustworthy than edible fruits. Nightshades make this point nicely. [Watch my Ancestral Health Symposium video about vegetables vs. fruits if you are curious about my vegetable philosophy.]

As you will see below, even though nightshade fruits contain glycoalkaloids, they either contain lower amounts of these potentially toxic compounds or contain gentler versions of them.

Luckily, most of the edible nightshades—eggplant, tomatoes, goji and peppers—are fruits (fruits by definition contain seeds). Tobacco is a nightshade vegetable, but it is typically smoked, not eaten, so the only nightshade vegetable humans consume is the beloved potato.

Potato glycoalkaloids

All potatoes are nightshades except for sweet potatoes and yams.

Potato plants make two glycoalkaloids: alpha-chaconine and alpha-solanine. These are the most toxic glycoalkaloids found in the edible nightshade family. Alpha-chaconine is actually more potent than alpha-solanine, but solanine has been studied much more thoroughly.

There are numerous cases of livestock deaths from eating raw potatoes, potato berries, and potato leaves, but people don’t eat these things. However, there are well-documented reports of people getting glycoalkaloid poisoning from potatoes, typically from eating improperly stored, green, or sprouting potatoes. At low doses, humans can experience gastrointestinal symptoms, such as vomiting and diarrhea. At higher doses, much more serious symptoms can occur, including fever, low blood pressure, confusion, and other neurological problems. At very high doses, glycoalkaloids are fatal.

Another reason why many people may not be bothered by potatoes is that glycoalkaloids are very poorly absorbed by the gastrointestinal tract, so, if you have a healthy digestive tract, most of the glycoalkaloid won’t make it into your bloodstream. However, if you eat potatoes every day, levels can build up over time and accumulate in the body’s tissues and organs, because it takes many days for them to be cleared. Also, since glycoalkaloids have the ability to burst cells open, they can theoretically cause damage to the cells that line your digestive system as they are passing through (this has been proven in animal studies but there are no human studies, to my knowledge).

Due to known toxicity, the FDA limits the glycoalkaloid content in potatoes to a maximum of 200 mg/kg potatoes (91 mg/lb). Human studies show that doses as low as 1 mg glycoalkaloid per kg body weight can be toxic, and that doses as low as 3 mg/kg can be fatal. This means that, if you weigh 150 lbs, doses as low as 68 mg could be toxic, and doses as low as 202 mg could be fatal.

Glycoalkaloid levels of a few prepared potato products are available [Milner 2006]:

• Potato chips, 1 oz bag: 0.36 to 0.88 mg chaconine and 0.29 to 1.4 mg solanine. Total glycoalkaloid concentrations range from 2.7 to 12.4 mg per bag.
• Fried potato skins, 4 oz: 4.4 to 13.6 mg chaconine and 2.0 to 9.5 mg solanine. Total glycoalkaloid concentrations range from 6.4 to 23.1 mg per 4 oz serving.

Potato processing 101 

The vast majority of glycoalkaloid is in the potato skin, so peeling will remove virtually all of it. Glycoalkaloid levels can be dangerously high in unripe and sprouting potatoes; any greenish areas or “eyes” should be removed or avoided.

Glycoalkaloids survive most types of cooking and processing. In fact, deep frying will increase levels if the oil isn’t changed frequently, so fried products such as potato skins and french fries can contain relatively high amounts:

“Mechanical damage to potato tissue increases the concentration of glycoalkaloids available for consumption. In addition, frying potatoes at high temperatures does not inactivate but instead serves to preserve and concentrate glycoalkaloids within the potato, leaving them available for ingestion and delivery to the intestine.” [Patel 2002]

• Boiling—reduces glycoalkaloids by a few percentage points
• Microwaving—reduces glycoalkaloids by 15%
• Deep frying at 150C (300F)—no effect (McDonald’s uses 340F oil)
• Deep frying at 210C (410F)—reduces glycoalkaloid content by 40%

Tomato glycoalkaloids

Tomato nightshades include all types of tomatoes: cherry tomatoes, green tomatoes, yellow tomatoes and ripe red tomatoes.

Tomatoes produce two glycoalkaloids: alpha-tomatine and dehydrotomatine. The majority is in the form of alpha-tomatine, so we’ll focus on that one here.

As tomatoes ripen, alpha-tomatine levels drop dramatically, from about 500 mg/kg in green tomatoes to about 5 mg/kg in ripe red tomatoes, or 2.3 mg/lb. [For those of you keeping score at home—that’s Fruits: 1, Veggies: 0.] Artificially ripened fruits may contain higher amounts than sun-ripened fruits.

Tomato glycoalkaloids are about 20 times less toxic than potato glycoalkaloids. (Fruits: 2, Veggies: 0). There are no dosage studies of tomatine in humans, but studies in mice tell us that 500 mg tomatine per 1 kg body weight (or 227 mg per pound) is the median lethal dose (LD50). This doesn’t tell us how much it would take to kill a 150 lb person; it only tells us that it would take 34 grams of tomatine to kill a 150-pound mouse. Since ripe tomatoes contain 5 mg/kg or 2.3 mg/lb of tomatine, it would take nearly 15,000 pounds of tomatoes to kill this Mighty Mouse (probably many fewer pounds if you were to simply hurl them in his general direction from across the room). Since green tomatoes contain 100 times more tomatine, it would only take 150 pounds of green tomatoes to kill the overgrown rodent. We do not understand the effect of low doses of tomatine over time on any type of animal, including humans.

Eggplant glycoalkaloids

Centuries ago, the common eggplant was referred to as “mad apple” due to belief that eating it regularly would cause mental illness. Eggplants produce two glycoalkaloids: alpha-solamargine and alpha-solasonine. Solamargine is more potent than solasonine.

Whereas potato glycoalkaloids are located mainly in the skin, in eggplants, glycoalkaloids are found primarily within the seeds and flesh; the peel contains negligible amounts.

The common eggplant (solanum melongena) contains 10-20 mg/kg (or 4.5 to 9 mg/lb of eggplant). Eggplant glycoalkaloids are considered relatively nontoxic compared to potato glycoalkaloids (Fruits: 3, Veggies: 0).

The median lethal dose (LD50) in rodents is 1.75 mg/kg. This means that it would take at least 13 pounds of eggplant to kill a 150 lb monster mouse. [Note to self—when facing a giant rodent in a dark alley, go for the eggplants, not the tomatoes].

Peppers

Red and green bell peppers contain less than 10 mg of glycoalkaloid per kg. This is a very small amount, so if you react badly to peppers, you are either very sensitive, or you are responding to other compounds within the peppers, such as the notoriously hot and spicy capsaicinoids.

What about goji berries?

Your guess is as good as mine . . . I could not locate any scientific information about glycoalkaloids in these foods.

Nightshades and nicotine

Nightshade foods also contain small amounts of nicotine, especially when unripe. Nicotine is much higher in tobacco leaves, of course. Scientists think that nicotine is a natural plant pesticide, although it is unclear exactly how it works to protect plants from invaders. The amount of nicotine in ripe nightshade foods ranges from 2 to 7 micrograms per kg of food. Nicotine is heat-stable, therefore it is found in prepared foods such as ketchup and French fries. The health effects of these small doses are not known, but some scientists wonder whether the nicotine content of these foods is why some people describe feeling addicted to them. In my opinion, it is more likely that the high carbohydrate content of those foods is responsible for their addictive properties.

Do you have nightshade sensitivity? 

As with any food sensitivity, the only way to find out is to remove nightshades from your diet for a couple of weeks or so to see if you feel better. There are ZERO scientific articles about nightshade sensitivity, chronic pain, or arthritis in the literature, however, the internet is full of anecdotal reports of people who have found that nightshades aggravate arthritis, fibromyalgia, or other chronic pain syndromes. I am personally very sensitive to nightshades; they cause me a variety of symptoms, most notably heartburn, difficulty concentrating, pounding heart, muscle/nerve/joint pain, and profound insomnia. Everyone is different, so as always, you’ll need to discover for yourself whether these foods may pose problems for your individual chemistry. However, given what we know about nightshade chemicals, common sense tells us that these foods are well worth exploring as potential culprits in pain syndromes, gastrointestinal syndromes, and neurologic/psychiatric symptoms.

If you experience anxiety or insomnia and are curious to know more about nightshades and the other foods most likely to be contributing to your symptoms, I recommend you read my Psychology Today article “5 Foods Proven to Cause Anxiety and Insomnia.”

Other food sensitivity syndromes

If nightshades aren’t your problem, you may be interested to know that there are many other foods which can cause real health issues for people.

• To read about foods that interfere with proper thyroid function, see my post “Foods that Cause Hypothyroidism.”
• To learn how aged, cured, fermented, smoked and processed foods can cause or worsen allergies, migraines, PMS/peri-menopausal symptoms, IBS, anxiety, or insomnia, read “Freshness Counts: Histamine Intolerance.”
• To learn which foods are most likely to cause acne, check out my post “The Secret to Outsmarting Your Acne.”
• To understand the risks of eating broccoli, kale, and other cruciferous vegetables, see my post “Is Broccoli Good For You?“
• To learn which foods are most likely to cause IBS check out “Common Constipation Culprits” and “Is Fructose Malabsorption Causing Your IBS?“

Nightshades have a reputation as bad actors in a variety of chronic conditions, such as arthritis, fibromyalgia, and IBS. But what do we really know about how these foods affect our health?

Meet the nightshade (solanaceae) family

• Tomatoes
• Tomatillos
• Eggplant
• Potatoes
• Goji Berries
• Tobacco
• Peppers (bell peppers, chili peppers, paprika, tamales, tomatillos, pimentos, cayenne, etc)

At first glance, the nightshades may look like a random collection of foods that couldn’t possibly be related. However, every nightshade plant produces fruits that all sport that same adorable little green elfish hat. Of the foods above, only tomatoes, eggplants, goji berries and peppers are “fruits” (the potato is a tuber and tobacco is a leaf). The fruits of potato and tobacco plants wear the same telltale hat, but we don’t eat the fruits of those plants.

Glycoalkaloids

Glycoalkaloids are natural pesticides produced by nightshade plants. Glycoalkaloids are bitter compounds which are found throughout the plant, but their concentrations are especially high in leaves, flowers, and unripe fruits. They are there to defend plants against bacteria, fungi, viruses, and insects.

Cherries, apples, and sugar beets also contain small amounts of glycoalkaloid even though they are not nightshades.

Vegetable violence

Glycoalkaloids act as invisible hand grenades. They bind strongly to the cholesterol in the cell membranes of predators, and in so doing, they disrupt the structure of those membranes, causing cells to leak or burst open upon contact.

Glycoalkaloids are neurotoxins. They block the enzyme cholinesterase. This enzyme is responsible for breaking down acetylcholine, a vital neurotransmitter that carries signals between nerve cells and muscle cells. When this important enzyme is blocked, acetylcholine can accumulate and electrically overstimulate the predator’s muscle cells. This can lead to paralysis, convulsions, respiratory arrest, and death. Military “nerve gases” work exactly the same way.

Ok, so glycoalkaloids are clearly nightmarish compounds for the cells of tiny creatures daring to munch upon nightshade plants, but what do we know about their effects on human health?

Nightshade glycoalkaloid health “benefits”

Health benefits? From a pesticide? Hmmm . . .

Since most people believe plant compounds are good for humans, when scientists conduct experiments with plant extracts, they are more likely to look for health benefits than health risks.

Glycoalkaloids are anti-inflammatory. Glycoalkaloids have been shown to reduce inflammation in laboratory animals. This is likely due to the fact that glycoalkaloids are structurally similar to compounds called glucocorticoids, which have well-known anti-inflammatory properties. Familiar examples of glucocorticoids include cortisol (our body’s natural stress hormone), and Prednisone, a commonly-prescribed anti-inflammatory medicine. It should be noted, however, that just because glycoalkaloids or glucocorticoids can reduce inflammation doesn’t mean they are always good for you. Prednisone is not something most of us should be taking every day, because it has numerous damaging side effects, and elevated levels of natural cortisol in our bodies weaken our immune system and slow our metabolism.

Glycoalkaloids kill bacteria and viruses. It should also not be surprising that glycoalkaloids have been shown in laboratory studies to possess antibiotic and antiviral properties, since this is what nature designed them for.

Glycoalkaloids have anti-cancer properties. In laboratory (in vitro) studies, glycoalkaloids can trigger cancer cells to self-destruct. This process is called “apoptosis.” Unfortunately, they can also cause healthy non-cancerous cells to do the same thing. Cancer studies in live animals and humans (in vivo) have not yet been conducted. The problem with so many anti-cancer plant compounds is that they are double-edged swords, killing both cancer cells and healthy cells alike:

“The undifferentiating destruction of both cancer and noncancerous cell lines . . . leads to questions of therapeutic uses of glycoalkaloids due to safety considerations. However, it is difficult to translate the results of an in vivo trial in vitro. Therefore, both animal and human experiments are essential to confirm or disprove the in vivo data observed in these studies.” [Milner 2011].

Health risks of nightshade glycoalkaloids

• Glycoalkaloids destroy cell membranes. Research has shown that glycoalkaloids can burst open the membranes of red blood cells and mitochondria (our cells’ energy generators). Some scientists have wondered whether glycoalkaloids could be one potential cause for ‘leaky gut’ syndromes due to their ability to poke holes in cells:

“Glycoalkaloids, normally available while eating potatoes, embed themselves and disrupt epithelial barrier integrity in a dose-dependent fashion in both cell culture models and in sheets of mammalian intestine. . . . [A]nimals with the genetic predisposition to develop IBD, demonstrated a greater degree of small intestinal epithelial barrier disruption and inflammation when their epithelium was exposed to the potato glycoalkaloids chaconine and solanine.” [Patel 2002]

• Glycoalkaloids cause birth defects in laboratory animals.

Nightshades and mental health

Due to widespread pro-plant food bias, the vast majority of scientific studies of nightshades explore their potential benefits rather than their downsides, so we do not have the studies we wish to have about how these interesting foods actually affect our well-being.

However, there have been plenty of documented cases of nightshade toxicity that demonstrate to us how poisonous they can be to our central nervous system—capable of causing severe neuropsychiatric side effects in human beings:

“In cases of mild glycoalkaloid poisoning symptoms include headache, vomiting, and diarrhea. Neurological symptoms were also reported, including apathy, restlessness, drowsiness, mental confusion, rambling, incoherence, stupor, hallucinations, dizziness, trembling, and visual disturbances.” [Milner 2011]

In a group of children who suffered from solanine poisoning as a result of eating potatoes that had been in storage for too long, severe psychiatric side effects were observed:

“The largest series of solanine poisoning involved an English day school where 78 schoolboys developed diarrhea and vomiting after eating potatoes stored since the summer term. Symptoms began 7-19 hours after ingestion with vomiting, diarrhea, anorexia, and malaise. Of the 78 boys, 17 were admitted to the hospital. Other symptoms included fever (88%), altered mental status (drowsiness, confusion, delirium) (82%), restlessness (47%), headache (29%), and hallucinations (23%). Three boys were seriously ill with hypotension, tachycardia [rapid heart rate], and stupor out of proportion to fluid and electrolyte imbalance. These boys were discharged 6-11 days after admission, and they had nonspecific symptoms and visual blurring for several weeks after release from the hospital.” [Barceloux 2009]

Keep in mind that these reactions just happened to be recorded due to their severity. We have no documented information about how everyday consumption of nightshades affects sensitive individuals, only numerous on-line personal accounts of mental health problems such as anxiety, panic, and insomnia that were alleviated by removal of nightshades from the diet. I personally experience profound insomnia and mild panic symptoms when I eat nightshades, which makes sense because glycoalkaloids overstimulate the nervous system.

If you experience anxiety or insomnia and are curious to know more about nightshades and the other foods most likely to be contributing to your symptoms, I recommend you read my Psychology Today article “5 Foods Proven to Cause Anxiety and Insomnia.”

Fruits vs vegetables: here we go again!

Those of you who are familiar with my philosophy about plant foods know that I believe that when it comes to our health, vegetables are far less trustworthy than edible fruits. Nightshades make this point nicely. [Watch my Ancestral Health Symposium video about vegetables vs. fruits if you are curious about my vegetable philosophy.]

As you will see below, even though nightshade fruits contain glycoalkaloids, they either contain lower amounts of these potentially toxic compounds or contain gentler versions of them.

Luckily, most of the edible nightshades—eggplant, tomatoes, goji and peppers—are fruits (fruits by definition contain seeds). Tobacco is a nightshade vegetable, but it is typically smoked, not eaten, so the only nightshade vegetable humans consume is the beloved potato.

Potato glycoalkaloids

All potatoes are nightshades except for sweet potatoes and yams.

Potato plants make two glycoalkaloids: alpha-chaconine and alpha-solanine. These are the most toxic glycoalkaloids found in the edible nightshade family. Alpha-chaconine is actually more potent than alpha-solanine, but solanine has been studied much more thoroughly.

There are numerous cases of livestock deaths from eating raw potatoes, potato berries, and potato leaves, but people don’t eat these things. However, there are well-documented reports of people getting glycoalkaloid poisoning from potatoes, typically from eating improperly stored, green, or sprouting potatoes. At low doses, humans can experience gastrointestinal symptoms, such as vomiting and diarrhea. At higher doses, much more serious symptoms can occur, including fever, low blood pressure, confusion, and other neurological problems. At very high doses, glycoalkaloids are fatal.

Another reason why many people may not be bothered by potatoes is that glycoalkaloids are very poorly absorbed by the gastrointestinal tract, so, if you have a healthy digestive tract, most of the glycoalkaloid won’t make it into your bloodstream. However, if you eat potatoes every day, levels can build up over time and accumulate in the body’s tissues and organs, because it takes many days for them to be cleared. Also, since glycoalkaloids have the ability to burst cells open, they can theoretically cause damage to the cells that line your digestive system as they are passing through (this has been proven in animal studies but there are no human studies, to my knowledge).

Due to known toxicity, the FDA limits the glycoalkaloid content in potatoes to a maximum of 200 mg/kg potatoes (91 mg/lb). Human studies show that doses as low as 1 mg glycoalkaloid per kg body weight can be toxic, and that doses as low as 3 mg/kg can be fatal. This means that, if you weigh 150 lbs, doses as low as 68 mg could be toxic, and doses as low as 202 mg could be fatal.

Glycoalkaloid levels of a few prepared potato products are available [Milner 2006]:

• Potato chips, 1 oz bag: 0.36 to 0.88 mg chaconine and 0.29 to 1.4 mg solanine. Total glycoalkaloid concentrations range from 2.7 to 12.4 mg per bag.
• Fried potato skins, 4 oz: 4.4 to 13.6 mg chaconine and 2.0 to 9.5 mg solanine. Total glycoalkaloid concentrations range from 6.4 to 23.1 mg per 4 oz serving.

Potato processing 101 

The vast majority of glycoalkaloid is in the potato skin, so peeling will remove virtually all of it. Glycoalkaloid levels can be dangerously high in unripe and sprouting potatoes; any greenish areas or “eyes” should be removed or avoided.

Glycoalkaloids survive most types of cooking and processing. In fact, deep frying will increase levels if the oil isn’t changed frequently, so fried products such as potato skins and french fries can contain relatively high amounts:

“Mechanical damage to potato tissue increases the concentration of glycoalkaloids available for consumption. In addition, frying potatoes at high temperatures does not inactivate but instead serves to preserve and concentrate glycoalkaloids within the potato, leaving them available for ingestion and delivery to the intestine.” [Patel 2002]

• Boiling—reduces glycoalkaloids by a few percentage points
• Microwaving—reduces glycoalkaloids by 15%
• Deep frying at 150C (300F)—no effect (McDonald’s uses 340F oil)
• Deep frying at 210C (410F)—reduces glycoalkaloid content by 40%

Tomato glycoalkaloids

Tomato nightshades include all types of tomatoes: cherry tomatoes, green tomatoes, yellow tomatoes and ripe red tomatoes.

Tomatoes produce two glycoalkaloids: alpha-tomatine and dehydrotomatine. The majority is in the form of alpha-tomatine, so we’ll focus on that one here.

As tomatoes ripen, alpha-tomatine levels drop dramatically, from about 500 mg/kg in green tomatoes to about 5 mg/kg in ripe red tomatoes, or 2.3 mg/lb. [For those of you keeping score at home—that’s Fruits: 1, Veggies: 0.] Artificially ripened fruits may contain higher amounts than sun-ripened fruits.

Tomato glycoalkaloids are about 20 times less toxic than potato glycoalkaloids. (Fruits: 2, Veggies: 0). There are no dosage studies of tomatine in humans, but studies in mice tell us that 500 mg tomatine per 1 kg body weight (or 227 mg per pound) is the median lethal dose (LD50). This doesn’t tell us how much it would take to kill a 150 lb person; it only tells us that it would take 34 grams of tomatine to kill a 150-pound mouse. Since ripe tomatoes contain 5 mg/kg or 2.3 mg/lb of tomatine, it would take nearly 15,000 pounds of tomatoes to kill this Mighty Mouse (probably many fewer pounds if you were to simply hurl them in his general direction from across the room). Since green tomatoes contain 100 times more tomatine, it would only take 150 pounds of green tomatoes to kill the overgrown rodent. We do not understand the effect of low doses of tomatine over time on any type of animal, including humans.

Eggplant glycoalkaloids

Centuries ago, the common eggplant was referred to as “mad apple” due to belief that eating it regularly would cause mental illness. Eggplants produce two glycoalkaloids: alpha-solamargine and alpha-solasonine. Solamargine is more potent than solasonine.

Whereas potato glycoalkaloids are located mainly in the skin, in eggplants, glycoalkaloids are found primarily within the seeds and flesh; the peel contains negligible amounts.

The common eggplant (solanum melongena) contains 10-20 mg/kg (or 4.5 to 9 mg/lb of eggplant). Eggplant glycoalkaloids are considered relatively nontoxic compared to potato glycoalkaloids (Fruits: 3, Veggies: 0).

The median lethal dose (LD50) in rodents is 1.75 mg/kg. This means that it would take at least 13 pounds of eggplant to kill a 150 lb monster mouse. [Note to self—when facing a giant rodent in a dark alley, go for the eggplants, not the tomatoes].

Peppers

Red and green bell peppers contain less than 10 mg of glycoalkaloid per kg. This is a very small amount, so if you react badly to peppers, you are either very sensitive, or you are responding to other compounds within the peppers, such as the notoriously hot and spicy capsaicinoids.

What about goji berries?

Your guess is as good as mine . . . I could not locate any scientific information about glycoalkaloids in these foods.

Nightshades and nicotine

Nightshade foods also contain small amounts of nicotine, especially when unripe. Nicotine is much higher in tobacco leaves, of course. Scientists think that nicotine is a natural plant pesticide, although it is unclear exactly how it works to protect plants from invaders. The amount of nicotine in ripe nightshade foods ranges from 2 to 7 micrograms per kg of food. Nicotine is heat-stable, therefore it is found in prepared foods such as ketchup and French fries. The health effects of these small doses are not known, but some scientists wonder whether the nicotine content of these foods is why some people describe feeling addicted to them. In my opinion, it is more likely that the high carbohydrate content of those foods is responsible for their addictive properties.

Do you have nightshade sensitivity? 

As with any food sensitivity, the only way to find out is to remove nightshades from your diet for a couple of weeks or so to see if you feel better. There are ZERO scientific articles about nightshade sensitivity, chronic pain, or arthritis in the literature, however, the internet is full of anecdotal reports of people who have found that nightshades aggravate arthritis, fibromyalgia, or other chronic pain syndromes. I am personally very sensitive to nightshades; they cause me a variety of symptoms, most notably heartburn, difficulty concentrating, pounding heart, muscle/nerve/joint pain, and profound insomnia. Everyone is different, so as always, you’ll need to discover for yourself whether these foods may pose problems for your individual chemistry. However, given what we know about nightshade chemicals, common sense tells us that these foods are well worth exploring as potential culprits in pain syndromes, gastrointestinal syndromes, and neurologic/psychiatric symptoms.

If you experience anxiety or insomnia and are curious to know more about nightshades and the other foods most likely to be contributing to your symptoms, I recommend you read my Psychology Today article “5 Foods Proven to Cause Anxiety and Insomnia.”

Other food sensitivity syndromes

If nightshades aren’t your problem, you may be interested to know that there are many other foods which can cause real health issues for people.

• To read about foods that interfere with proper thyroid function, see my post “Foods that Cause Hypothyroidism.”
• To learn how aged, cured, fermented, smoked and processed foods can cause or worsen allergies, migraines, PMS/peri-menopausal symptoms, IBS, anxiety, or insomnia, read “Freshness Counts: Histamine Intolerance.”
• To learn which foods are most likely to cause acne, check out my post “The Secret to Outsmarting Your Acne.”
• To understand the risks of eating broccoli, kale, and other cruciferous vegetables, see my post “Is Broccoli Good For You?“
• To learn which foods are most likely to cause IBS check out “Common Constipation Culprits” and “Is Fructose Malabsorption Causing Your IBS?“

Nectresse is a new sweetener marketed by McNeil Nutritionals, the manufacturers of Splenda. Unlike Splenda, Nectresse is made from all-natural ingredients and therefore may appeal to those who wish to cut calories and exposure to the damaging effects of sugar without having to resort to artificial sweeteners.

As you can see, the vast majority of Nectresse (2 grams or 83%) is actually erythritol, not Mogroside V. The erythritol, sugar, and molasses act as sweet fillers. Mogroside V is so intensely sweet you wouldn’t want a whole packet of it. [It is for this same reason that the main ingredient in Splenda is not super-sweet sucralose, but dextrose, which is added as a bulking agent.] In the U.S., foods can be labeled as zero-calorie if they contain fewer than 5 calories per serving, so we don’t know exactly how many calories are in a 2.4 gram packet of Nectresse, only that it has fewer than 5 calories. Below is a quote taken directly from the manufacturer’s website:

“Like other no-calorie sweeteners, NECTRESSE Sweetener contains a small amount of carbohydrate (1-2 grams per serving) from other food ingredients to provide needed volume and texture. These food ingredients, which include small amounts of erythritol, sugar, and molasses, contribute so few calories per serving that NECTRESSE Natural No Calorie Sweetener Products meet the FDA’s criteria for no-calorie foods (<5 calories/serving).”

What is erythritol?

Erythritol is produced by adding yeast to glucose (a simple sugar) and letting it ferment. [Erythritol does exist in small amounts in nature, as well; however it would be expensive and impractical to collect it in large quantities for mass consumption.] Compared to sugar, sugar alcohols are poorly absorbed into our bloodstream, which is why they tend to be lower in calories. Most sugar alcohols make it all the way to the large intestine, where they may be fermented by bacteria, which can cause gases, bloating, and diarrhea. Sugar alcohols are notorious for causing embarrassing gastrointestinal side effects, especially if eaten in large quantities; however erythritol is the sugar alcohol least likely to cause these problems.

What is Mogroside V? 

While it sounds like a great name for, say, a big ugly orc, Mogroside V is an intensely sweet compound, 300 to 400 times sweeter than sugar. It is isolated from the monkfruit, a round, green fruit which grows in southwestern China—it is called monkfruit because it was eaten by Chinese monks as early as the 13th century. It also goes by many other names, such as luo han guo (aka “lo han”), rakanka, and Siraitia Grosvenori Swingle. The monkfruit belongs to the Cucurbita family of fruits, which includes cucumbers, melons, pumpkins, squashes, and gourds.

Monkfruit itself is described as having an unpleasant, cloying flavor, inspiring mouth-watering adjectives such as “licorice-like” and “vegetable-like.” Fresh monkfruit goes bad very quickly, so it is typically sold dried. In Asia, monkfruit has long been thought of as a medicinal fruit, being used to treat common symptoms such as coughs, sore throats, and constipation. Mogroside V makes up 1% of the weight of a dried monkfruit. Mogroside V dissolves easily in water, is heat-stable (so it can be used for cooking), and has a shelf life of approximately three years at room temperature.

Monkfruit extracts have been used in sugar substitutes for more than 30 years. Other brand name sweeteners which contain monkfruit extract include:

• Fruit-Sweetness™ (BioVittoria)
• Lakanto® (Saraya)
• PureFruit™ (Tate and Lyle)
• PureLo® (BioVittoria)
• SweetLife (Renew Life®)
• Symple™ (Naturewise)

I personally do not like the taste of Nectresse—I find it intolerably bitter, just as I do Stevia extract. However, everyone’s taste buds are different, and I understand that many people like it.

How does the human body handle Mogroside V?

Your guess is as good as mine.

To my surprise, I was unable to locate a single scientific study of Mogroside V metabolism in humans. There are just a handful of studies of this compound, some of which are published only in Chinese. All studies available were either conducted in laboratory animals or under test tube conditions (in vitro) using isolated cells. Nevertheless, in July 2009, the FDA declared Mogroside V “GRAS” (generally recognized as safe) in response to an application by the New Zealand company BioVittoria [BioVittoria supplies the monkfruit extract used in Nectresse]. So, I wrote to the BioVittoria company requesting scientific information, and was delighted to receive very helpful information from a kind representative, including a detailed research report, complete with dozens of references.

Is Mogroside V safe for human consumption?

Probably.

The FDA did not conduct its own safety studies of Mogroside V, but rather relied on BioVittoria to conduct studies. BioVittoria convinced the FDA of the safety of Mogroside V based on:

• 2 unpublished studies in humans to determine blood glucose and liver enzymes
• Several feeding studies in laboratory animals (rats, dogs, mice)
• 2 in-vitro genotoxicity studies (both found Mogroside V to be noncarcinogenic)

The unpublished studies reportedly demonstrated that Mogroside V does not raise blood sugar in humans. Published animal studies conclude that Mogroside V actually has “anti-diabetic effects.” The following is an example of an animal study showcasing the “anti-diabetic” effects of Mogroside V.

Researchers compared two diets in rats with type II diabetes—one diet contained Mogroside V (4 g/kg) and one diet contained cellulose (4 g/kg) as a control. Rats that ate Mogroside V demonstrated increased insulin production and secretion, which improved blood sugar regulation. The researchers concluded that this was a good thing because it was proof of “anti-diabetic” effects of Mogroside V. But let’s think about this for a moment.

1. A dose of 4 g/kg is extremely high. The average human would have to eat about 250 grams of pure Mogroside V extract to match this dose—that is the equivalent of more than 250 packets of Nectresse per day. [Toxicity studies in mice suggest that, on average, it would take about 10 g/kg to kill a human being.]
2. Increased insulin production is not necessarily a good thing. In fact, hyperinsulinemia (high insulin level) is exactly what we want to avoid, as it is a well-established risk factor for numerous diseases of civilization. Insulin tells the body to make fat. Please see my Carbohydrates page for more information.
3. Both of the rat diets were unbelievably junky—loaded with refined carbohydrate:

• 53% corn starch
• 20% casein (milk protein)
• 10% sucrose
• 7% soybean oil
• 5% cellulose
• 5% vitamins and minerals

Poor rats. I doubt you could design a menu that is farther from the natural diet of a rat if your life depended on it. Changing anything about this diet was bound to be an improvement. These animals did not gain weight or eat more food on the Mogroside diet compared to the regular diet. However, given their atrocious diet, I’m not sure it would have been possible for them to experience more weight gain or higher appetites than they must have been experiencing already.

4. Studies in rats tell us that Mogroside V itself is not even absorbed into the bloodstream (we don’t know if it is absorbed by humans). Instead, a by-product called “Mogrol” was found in trace amounts in the bloodstream. It is thought that Mogrol may be responsible for the metabolic effects of monkfruit extract.

In short, these studies tell us nothing about the effects of typical doses of Mogroside V on the blood sugar and insulin levels of human beings.

Why even bother to question the safety of a natural fruit extract? Because there can be important differences in health effects between eating a whole food in its natural state and consuming unnaturally concentrated extracts from that same food. Fruit extracts are, by and large, far less likely to be harmful to humans than vegetable extracts, so that is reassuring. (For more information about fruits vs. vegetables, see my pages about fruits and/or vegetables.)

Bottom line about Nectresse and Mogroside V:

1. Most of Nectresse consists of erythritol, not Mogroside V, so if erythritol doesn’t agree with you, neither will Nectresse.
2. Taste a bit of Nectresse before purchasing large quantities to be sure you like it.
3. I find no evidence that Nectresse is harmful to humans—however this is only because there are no published studies of the effects of Nectresse on humans.
4. If we trust the unpublished human studies, which reportedly found that Mogroside V did not raise blood sugar levels, then that is a good thing. However, as with all sweeteners, what is true in a study may not be true for you, so the only way to know if Nectresse raises your blood sugar is to test your own blood sugar readings before and after eating it.
5. There are no studies of Mogroside V on the insulin levels of human beings. High doses of Mogroside V in animals causes insulin spikes, which is not necessarily a good thing. High insulin levels are a risk factor for increased appetite and weight gain. Those of you who eat a ketogenic diet should be aware that Nectresse may cause insulin spikes which could temporarily reduce your serum ketone levels, so you’ll need to monitor your ketones carefully when first trying Nectresse.
6. Overall, I doubt that Mogroside V poses significant problems for the average human, but there isn’t enough evidence to be sure. As with any substance, the only way to know how it affects your metabolism—including your appetite, weight, and blood sugar, is to do your own experiments. Is it safer than sugar? Probably.

What about you? Have you tried Nectresse? Do you like it? Do you respond well to it? I’d love to read about your experience in the comments below.

If you are interested in reducing the sugar in your diet, you may also want to check out my insulin resistance post that includes an infographic about how to identify hidden sugars in your diet as well as my refined carbohydrates list.

Acknowledgments:

I am very grateful to Mr. Paul Paslaski of BioVittoria for providing such helpful scientific information regarding Mogroside V.

Nectresse is a new sweetener marketed by McNeil Nutritionals, the manufacturers of Splenda. Unlike Splenda, Nectresse is made from all-natural ingredients and therefore may appeal to those who wish to cut calories and exposure to the damaging effects of sugar without having to resort to artificial sweeteners.

As you can see, the vast majority of Nectresse (2 grams or 83%) is actually erythritol, not Mogroside V. The erythritol, sugar, and molasses act as sweet fillers. Mogroside V is so intensely sweet you wouldn’t want a whole packet of it. [It is for this same reason that the main ingredient in Splenda is not super-sweet sucralose, but dextrose, which is added as a bulking agent.] In the U.S., foods can be labeled as zero-calorie if they contain fewer than 5 calories per serving, so we don’t know exactly how many calories are in a 2.4 gram packet of Nectresse, only that it has fewer than 5 calories. Below is a quote taken directly from the manufacturer’s website:

“Like other no-calorie sweeteners, NECTRESSE Sweetener contains a small amount of carbohydrate (1-2 grams per serving) from other food ingredients to provide needed volume and texture. These food ingredients, which include small amounts of erythritol, sugar, and molasses, contribute so few calories per serving that NECTRESSE Natural No Calorie Sweetener Products meet the FDA’s criteria for no-calorie foods (<5 calories/serving).”

What is erythritol?

Erythritol is produced by adding yeast to glucose (a simple sugar) and letting it ferment. [Erythritol does exist in small amounts in nature, as well; however it would be expensive and impractical to collect it in large quantities for mass consumption.] Compared to sugar, sugar alcohols are poorly absorbed into our bloodstream, which is why they tend to be lower in calories. Most sugar alcohols make it all the way to the large intestine, where they may be fermented by bacteria, which can cause gases, bloating, and diarrhea. Sugar alcohols are notorious for causing embarrassing gastrointestinal side effects, especially if eaten in large quantities; however erythritol is the sugar alcohol least likely to cause these problems.

What is Mogroside V? 

While it sounds like a great name for, say, a big ugly orc, Mogroside V is an intensely sweet compound, 300 to 400 times sweeter than sugar. It is isolated from the monkfruit, a round, green fruit which grows in southwestern China—it is called monkfruit because it was eaten by Chinese monks as early as the 13th century. It also goes by many other names, such as luo han guo (aka “lo han”), rakanka, and Siraitia Grosvenori Swingle. The monkfruit belongs to the Cucurbita family of fruits, which includes cucumbers, melons, pumpkins, squashes, and gourds.

Monkfruit itself is described as having an unpleasant, cloying flavor, inspiring mouth-watering adjectives such as “licorice-like” and “vegetable-like.” Fresh monkfruit goes bad very quickly, so it is typically sold dried. In Asia, monkfruit has long been thought of as a medicinal fruit, being used to treat common symptoms such as coughs, sore throats, and constipation. Mogroside V makes up 1% of the weight of a dried monkfruit. Mogroside V dissolves easily in water, is heat-stable (so it can be used for cooking), and has a shelf life of approximately three years at room temperature.

Monkfruit extracts have been used in sugar substitutes for more than 30 years. Other brand name sweeteners which contain monkfruit extract include:

• Fruit-Sweetness™ (BioVittoria)
• Lakanto® (Saraya)
• PureFruit™ (Tate and Lyle)
• PureLo® (BioVittoria)
• SweetLife (Renew Life®)
• Symple™ (Naturewise)

I personally do not like the taste of Nectresse—I find it intolerably bitter, just as I do Stevia extract. However, everyone’s taste buds are different, and I understand that many people like it.

How does the human body handle Mogroside V?

Your guess is as good as mine.

To my surprise, I was unable to locate a single scientific study of Mogroside V metabolism in humans. There are just a handful of studies of this compound, some of which are published only in Chinese. All studies available were either conducted in laboratory animals or under test tube conditions (in vitro) using isolated cells. Nevertheless, in July 2009, the FDA declared Mogroside V “GRAS” (generally recognized as safe) in response to an application by the New Zealand company BioVittoria [BioVittoria supplies the monkfruit extract used in Nectresse]. So, I wrote to the BioVittoria company requesting scientific information, and was delighted to receive very helpful information from a kind representative, including a detailed research report, complete with dozens of references.

Is Mogroside V safe for human consumption?

Probably.

The FDA did not conduct its own safety studies of Mogroside V, but rather relied on BioVittoria to conduct studies. BioVittoria convinced the FDA of the safety of Mogroside V based on:

• 2 unpublished studies in humans to determine blood glucose and liver enzymes
• Several feeding studies in laboratory animals (rats, dogs, mice)
• 2 in-vitro genotoxicity studies (both found Mogroside V to be noncarcinogenic)

The unpublished studies reportedly demonstrated that Mogroside V does not raise blood sugar in humans. Published animal studies conclude that Mogroside V actually has “anti-diabetic effects.” The following is an example of an animal study showcasing the “anti-diabetic” effects of Mogroside V.

Researchers compared two diets in rats with type II diabetes—one diet contained Mogroside V (4 g/kg) and one diet contained cellulose (4 g/kg) as a control. Rats that ate Mogroside V demonstrated increased insulin production and secretion, which improved blood sugar regulation. The researchers concluded that this was a good thing because it was proof of “anti-diabetic” effects of Mogroside V. But let’s think about this for a moment.

1. A dose of 4 g/kg is extremely high. The average human would have to eat about 250 grams of pure Mogroside V extract to match this dose—that is the equivalent of more than 250 packets of Nectresse per day. [Toxicity studies in mice suggest that, on average, it would take about 10 g/kg to kill a human being.]
2. Increased insulin production is not necessarily a good thing. In fact, hyperinsulinemia (high insulin level) is exactly what we want to avoid, as it is a well-established risk factor for numerous diseases of civilization. Insulin tells the body to make fat. Please see my Carbohydrates page for more information.
3. Both of the rat diets were unbelievably junky—loaded with refined carbohydrate:

• 53% corn starch
• 20% casein (milk protein)
• 10% sucrose
• 7% soybean oil
• 5% cellulose
• 5% vitamins and minerals

Poor rats. I doubt you could design a menu that is farther from the natural diet of a rat if your life depended on it. Changing anything about this diet was bound to be an improvement. These animals did not gain weight or eat more food on the Mogroside diet compared to the regular diet. However, given their atrocious diet, I’m not sure it would have been possible for them to experience more weight gain or higher appetites than they must have been experiencing already.

4. Studies in rats tell us that Mogroside V itself is not even absorbed into the bloodstream (we don’t know if it is absorbed by humans). Instead, a by-product called “Mogrol” was found in trace amounts in the bloodstream. It is thought that Mogrol may be responsible for the metabolic effects of monkfruit extract.

In short, these studies tell us nothing about the effects of typical doses of Mogroside V on the blood sugar and insulin levels of human beings.

Why even bother to question the safety of a natural fruit extract? Because there can be important differences in health effects between eating a whole food in its natural state and consuming unnaturally concentrated extracts from that same food. Fruit extracts are, by and large, far less likely to be harmful to humans than vegetable extracts, so that is reassuring. (For more information about fruits vs. vegetables, see my pages about fruits and/or vegetables.)

Bottom line about Nectresse and Mogroside V:

1. Most of Nectresse consists of erythritol, not Mogroside V, so if erythritol doesn’t agree with you, neither will Nectresse.
2. Taste a bit of Nectresse before purchasing large quantities to be sure you like it.
3. I find no evidence that Nectresse is harmful to humans—however this is only because there are no published studies of the effects of Nectresse on humans.
4. If we trust the unpublished human studies, which reportedly found that Mogroside V did not raise blood sugar levels, then that is a good thing. However, as with all sweeteners, what is true in a study may not be true for you, so the only way to know if Nectresse raises your blood sugar is to test your own blood sugar readings before and after eating it.
5. There are no studies of Mogroside V on the insulin levels of human beings. High doses of Mogroside V in animals causes insulin spikes, which is not necessarily a good thing. High insulin levels are a risk factor for increased appetite and weight gain. Those of you who eat a ketogenic diet should be aware that Nectresse may cause insulin spikes which could temporarily reduce your serum ketone levels, so you’ll need to monitor your ketones carefully when first trying Nectresse.
6. Overall, I doubt that Mogroside V poses significant problems for the average human, but there isn’t enough evidence to be sure. As with any substance, the only way to know how it affects your metabolism—including your appetite, weight, and blood sugar, is to do your own experiments. Is it safer than sugar? Probably.

What about you? Have you tried Nectresse? Do you like it? Do you respond well to it? I’d love to read about your experience in the comments below.

If you are interested in reducing the sugar in your diet, you may also want to check out my insulin resistance post that includes an infographic about how to identify hidden sugars in your diet as well as my refined carbohydrates list.

Acknowledgments:

I am very grateful to Mr. Paul Paslaski of BioVittoria for providing such helpful scientific information regarding Mogroside V.

So, what if you already avoid refined carbs, eat the right kinds of fats, and still have ADHD symptoms? Perhaps you eat a Paleo diet, or a low-carb Paleo diet, or even a ketogenic diet, and are still troubled by ADHD . . . what then?

Food sensitivities can cause ADHD symptoms

In my work with children and adults with ADHD, I have seen some patients reduce or even cure their ADHD symptoms simply by removing certain foods from their diet. People are often completely unaware that they have a food sensitivity, especially if the food that bothers them is something they eat every day, like wheat or dairy products. Everybody is different, so food that is the culprit for one person may not bother another person at all. While any food can be problematic, the ones that have been shown by researchers to be the most commonly associated with ADHD symptoms are:

• Gluten (from wheat and related grains)*
• Dairy products (usually due to casein, a dairy protein)
• Soy
• Corn
• Legumes
• Oats
• Eggs
• Nuts and peanuts
• Citrus
• Chocolate
• Tomato
• Yeast
• Fish
• Shellfish

*People with Celiac Disease (an autoimmune disease associated with gluten) are more likely to have ADHD symptoms, and these symptoms usually improve on a gluten-free diet. However, people with ADHD are at no higher risk for Celiac Disease than people without ADHD.

Simplified diets shown to cure ADHD

Dietary studies have found a strong connection between food and ADHD symptoms. These studies are small and have their limitations, as most nutrition studies do, but they all produce remarkable results. These studies compared a standard diet to a special limited diet and found that the special diet resulted in a dramatic reduction in ADHD symptoms. Most people with ADHD are not aware of these studies (notice that all of them were conducted in Europe):

Egger 1985 (London)

Carter 1993 (London)

Schmidt 1997 (Germany)

Pelsser 2002 (Netherlands)

Pelsser 2009 (Netherlands)

What was so magical about these diets? These simple diets removed all of the common food culprits listed above, as well as sugar and processed foods. These diets have a lot in common with whole-foods, hunter-gatherer diets of meats, fruits, and vegetables. I personally believe the studies may have worked even better if researchers had also removed the fruit juice (high in sugars), margarine (high in omega-6 and trans fats), and white rice (high glycemic index), but nevertheless, these diets worked very well. 62% to 82% response rates in outpatients and a 24% response rate in inpatients—pretty impressive.

The Feingold Diet?

Ben Feingold, MD was a pediatric allergy specialist who wrote a book in 1975 called Why Your Child Is Hyperactive. He recommended a diet free of artificial flavors and colors, and advised avoiding foods containing salicylate, a naturally occurring plant chemical found in a wide variety of fruits, vegetables, and spices. He claimed that his special diet was effective for 50% of children with ADHD. This diet is referred to as the Feingold Diet, or as the “K-P Diet” (K-P for Kaiser-Permanente, the name of the medical center where he worked).

Plants use salicylates as signaling compounds and to protect themselves from infection and insects. Aspirin is a famous salicylate originally extracted from willow bark. Below are the foods Dr. Feingold thought to be high in salicylates, and therefore advised eliminating from the diet:

Improved food testing methods have since determined that the following foods contain the highest amounts of salicylates [Wood 2011]:

• Fruits: red grapes, lemons, peaches, pears, cherries. dried fruits typically much higher.
• Vegetables: asparagus, eggplant, broccoli, mushrooms, onions, green peppers
• Beverages: coffee, tea, beer, pineapple juice, tomato juice
• Herbs/Spices: All tested were extremely high, with exception of garlic which was extremely low

Legumes and grains are very low in salicylates. All animal foods, including meats, organ meats, and dairy products, contain little to no salicylate.

Does the Feingold Diet really work?

None of the studies of this diet were able to generate the impressive 50% cure rate that Feingold reported. However, some of the studies did find that a small number of children (11% to 33%) were significantly less hyperactive on his diet.

ADHD and artificial colors

An analysis [Schab 2004] of the 15 best studies done on food coloring and ADHD found a clear connection between artificial food colorings and hyperactivity in children with ADHD. A review of all studies [Stevens 2011] concluded that artificial food colorings can result in significant changes in behavior in people with ADHD, and two studies found that artificial colorings can even cause hyperactivity in people who do not have a history of ADHD. The vast majority of studies tested complicated mixtures of artificial colors rather than single additives, often in combination with sodium benzoate, a popular preservative. The artificial colors used in experiments are listed below. Those in italics are no longer approved for use in foods in the United States:

Tartrazine (Yellow #5)
Sunset Yellow (Yellow #6)
Quinoline Yellow (Yellow #10)
Allura Red (Red #40)
Erythrosine (Red #3)
Carmoisine (Red #10)
Ponceau 4R (a red dye)
Brilliant Blue (Blue #1)
Indigotine (Blue #2)
Fast Green (Green #3)
Orange B

Are people with ADHD more sensitive?

In my clinical experience I have found that many of my ADHD patients are more sensitive in general, not only to foods and medications, but also to other stimuli, such as scents and sounds. They can also be more socially sensitive, particularly to perceived judgment, exclusion, or rejection. The European studies detailed above make it clear that many children have food sensitivities that manifest themselves as ADHD symptoms. Could it be that some people with ADHD are simply reacting badly to certain foods? I know for myself that changing my diet significantly improved my concentration, productivity, motivation and energy, and eliminated my dependence on caffeine to get things done.

Your own body of evidence

While there are good medical tests available for true food allergies, there are no medical tests for food sensitivities. So how do you know if your ADHD symptoms are being caused by food sensitivities? There are many other bodily clues to food issues, such as asthma, eczema, fatigue, fluid retention, frequent headaches, or digestive problems. One possible sign of food sensitivity that is easy to recognize is the presence of dark circles under the eyes, which allergy specialists call “allergic shiners.” People often mistake dark circles for signs of poor sleep or fatigue, but dark circles are most often a sign of allergy or sensitivity.

An example from my own personal experience: I underwent complete food allergy (skin) testing and was found to have no allergies to any of the foods included in the panel, including nuts. However, whenever I ate something that contained small amounts of nuts, the next morning I would see dark circles under my eyes (along with a variety of other unhappy symptoms), which I did not normally have. 24% of people who do not have allergies have allergic shiners—how many of these non-allergic people have food sensitivities?

Unfortunately, the only way for you to discover whether or not your ADHD symptoms are due to a food sensitivity is to do your own dietary experiment. There are many ways to do this, but the two most popular are the all-at-once approach and the one-at-a-time approach. You may prefer to remove all of the most common culprits for two weeks and see if you feel better. If you do, then reintroduce one food at a time for at least three days in a row to try to identify the guilty food (or foods). Others prefer to remove one culprit at a time for two weeks to see if that single food is causing the problem. If it is not, that food can be added back, and the next suspect can be removed for two weeks, and so on. This approach takes much more time, but some people find it easier than removing so many culprits all at once.

The hypo-allergenic Paleo diet

When people ask me what diet I recommend to identify if food sensitivities may be causing ADHD, I recommend what I call a “hypo-allergenic” Paleo diet for two weeks. This diet consists of:

• Chicken, turkey, duck and/or lamb and their organ meats (no sauces or marinades)
• Any fresh/frozen vegetables you like (except for green beans, wax beans, sprouts, beets and white potato)
• Any whole fresh/frozen fruits you like except for citrus and tomato.
• Water, seltzer

No dairy, nuts, soy, grains, legumes, nuts, seeds, beef, pork, chocolate, eggs, yeast, coffee, tea, sugar, juices, processed foods, artificial ingredients, gum, sweeteners (whether natural or artificial), or cold cuts at first. Avoid preserved, fermented, canned, dried, smoked, pickled, and excessively salty foods.

After two weeks if you are feeling better, you can try adding back beef, pork, fish, citrus, tomato, coffee, tea, etc. one at a time for three days each to see if they bother you.

Keep in mind that any food can be a culprit, including any food on my hypo-allergenic Paleo diet, so some people may need to explore further, but the above diet removes all of the most common culprits.

These dietary experiments can be frustrating and difficult, but they can also be very illuminating. Once you have figured out your food sensitivities, it does not mean you can never eat that food again—that’s completely up to you—but at least you’ll have more control over how you feel from day to day if you want to!

What about you?

Have you been able to reduce your ADHD symptoms by making dietary changes? What has or has not worked for you?

If you are want to learn more more about ADHD and diet, you may be interested in my articles “Sugar and ADHD” and “Attention! Is Your Diet Causing ADHD?“

So, what if you already avoid refined carbs, eat the right kinds of fats, and still have ADHD symptoms? Perhaps you eat a Paleo diet, or a low-carb Paleo diet, or even a ketogenic diet, and are still troubled by ADHD . . . what then?

Food sensitivities can cause ADHD symptoms

In my work with children and adults with ADHD, I have seen some patients reduce or even cure their ADHD symptoms simply by removing certain foods from their diet. People are often completely unaware that they have a food sensitivity, especially if the food that bothers them is something they eat every day, like wheat or dairy products. Everybody is different, so food that is the culprit for one person may not bother another person at all. While any food can be problematic, the ones that have been shown by researchers to be the most commonly associated with ADHD symptoms are:

• Gluten (from wheat and related grains)*
• Dairy products (usually due to casein, a dairy protein)
• Soy
• Corn
• Legumes
• Oats
• Eggs
• Nuts and peanuts
• Citrus
• Chocolate
• Tomato
• Yeast
• Fish
• Shellfish

*People with Celiac Disease (an autoimmune disease associated with gluten) are more likely to have ADHD symptoms, and these symptoms usually improve on a gluten-free diet. However, people with ADHD are at no higher risk for Celiac Disease than people without ADHD.

Simplified diets shown to cure ADHD

Dietary studies have found a strong connection between food and ADHD symptoms. These studies are small and have their limitations, as most nutrition studies do, but they all produce remarkable results. These studies compared a standard diet to a special limited diet and found that the special diet resulted in a dramatic reduction in ADHD symptoms. Most people with ADHD are not aware of these studies (notice that all of them were conducted in Europe):

Egger 1985 (London)

Carter 1993 (London)

Schmidt 1997 (Germany)

Pelsser 2002 (Netherlands)

Pelsser 2009 (Netherlands)

What was so magical about these diets? These simple diets removed all of the common food culprits listed above, as well as sugar and processed foods. These diets have a lot in common with whole-foods, hunter-gatherer diets of meats, fruits, and vegetables. I personally believe the studies may have worked even better if researchers had also removed the fruit juice (high in sugars), margarine (high in omega-6 and trans fats), and white rice (high glycemic index), but nevertheless, these diets worked very well. 62% to 82% response rates in outpatients and a 24% response rate in inpatients—pretty impressive.

The Feingold Diet?

Ben Feingold, MD was a pediatric allergy specialist who wrote a book in 1975 called Why Your Child Is Hyperactive. He recommended a diet free of artificial flavors and colors, and advised avoiding foods containing salicylate, a naturally occurring plant chemical found in a wide variety of fruits, vegetables, and spices. He claimed that his special diet was effective for 50% of children with ADHD. This diet is referred to as the Feingold Diet, or as the “K-P Diet” (K-P for Kaiser-Permanente, the name of the medical center where he worked).

Plants use salicylates as signaling compounds and to protect themselves from infection and insects. Aspirin is a famous salicylate originally extracted from willow bark. Below are the foods Dr. Feingold thought to be high in salicylates, and therefore advised eliminating from the diet:

Improved food testing methods have since determined that the following foods contain the highest amounts of salicylates [Wood 2011]:

• Fruits: red grapes, lemons, peaches, pears, cherries. dried fruits typically much higher.
• Vegetables: asparagus, eggplant, broccoli, mushrooms, onions, green peppers
• Beverages: coffee, tea, beer, pineapple juice, tomato juice
• Herbs/Spices: All tested were extremely high, with exception of garlic which was extremely low

Legumes and grains are very low in salicylates. All animal foods, including meats, organ meats, and dairy products, contain little to no salicylate.

Does the Feingold Diet really work?

None of the studies of this diet were able to generate the impressive 50% cure rate that Feingold reported. However, some of the studies did find that a small number of children (11% to 33%) were significantly less hyperactive on his diet.

ADHD and artificial colors

An analysis [Schab 2004] of the 15 best studies done on food coloring and ADHD found a clear connection between artificial food colorings and hyperactivity in children with ADHD. A review of all studies [Stevens 2011] concluded that artificial food colorings can result in significant changes in behavior in people with ADHD, and two studies found that artificial colorings can even cause hyperactivity in people who do not have a history of ADHD. The vast majority of studies tested complicated mixtures of artificial colors rather than single additives, often in combination with sodium benzoate, a popular preservative. The artificial colors used in experiments are listed below. Those in italics are no longer approved for use in foods in the United States:

Tartrazine (Yellow #5)
Sunset Yellow (Yellow #6)
Quinoline Yellow (Yellow #10)
Allura Red (Red #40)
Erythrosine (Red #3)
Carmoisine (Red #10)
Ponceau 4R (a red dye)
Brilliant Blue (Blue #1)
Indigotine (Blue #2)
Fast Green (Green #3)
Orange B

Are people with ADHD more sensitive?

In my clinical experience I have found that many of my ADHD patients are more sensitive in general, not only to foods and medications, but also to other stimuli, such as scents and sounds. They can also be more socially sensitive, particularly to perceived judgment, exclusion, or rejection. The European studies detailed above make it clear that many children have food sensitivities that manifest themselves as ADHD symptoms. Could it be that some people with ADHD are simply reacting badly to certain foods? I know for myself that changing my diet significantly improved my concentration, productivity, motivation and energy, and eliminated my dependence on caffeine to get things done.

Your own body of evidence

While there are good medical tests available for true food allergies, there are no medical tests for food sensitivities. So how do you know if your ADHD symptoms are being caused by food sensitivities? There are many other bodily clues to food issues, such as asthma, eczema, fatigue, fluid retention, frequent headaches, or digestive problems. One possible sign of food sensitivity that is easy to recognize is the presence of dark circles under the eyes, which allergy specialists call “allergic shiners.” People often mistake dark circles for signs of poor sleep or fatigue, but dark circles are most often a sign of allergy or sensitivity.

An example from my own personal experience: I underwent complete food allergy (skin) testing and was found to have no allergies to any of the foods included in the panel, including nuts. However, whenever I ate something that contained small amounts of nuts, the next morning I would see dark circles under my eyes (along with a variety of other unhappy symptoms), which I did not normally have. 24% of people who do not have allergies have allergic shiners—how many of these non-allergic people have food sensitivities?

Unfortunately, the only way for you to discover whether or not your ADHD symptoms are due to a food sensitivity is to do your own dietary experiment. There are many ways to do this, but the two most popular are the all-at-once approach and the one-at-a-time approach. You may prefer to remove all of the most common culprits for two weeks and see if you feel better. If you do, then reintroduce one food at a time for at least three days in a row to try to identify the guilty food (or foods). Others prefer to remove one culprit at a time for two weeks to see if that single food is causing the problem. If it is not, that food can be added back, and the next suspect can be removed for two weeks, and so on. This approach takes much more time, but some people find it easier than removing so many culprits all at once.

The hypo-allergenic Paleo diet

When people ask me what diet I recommend to identify if food sensitivities may be causing ADHD, I recommend what I call a “hypo-allergenic” Paleo diet for two weeks. This diet consists of:

• Chicken, turkey, duck and/or lamb and their organ meats (no sauces or marinades)
• Any fresh/frozen vegetables you like (except for green beans, wax beans, sprouts, beets and white potato)
• Any whole fresh/frozen fruits you like except for citrus and tomato.
• Water, seltzer

No dairy, nuts, soy, grains, legumes, nuts, seeds, beef, pork, chocolate, eggs, yeast, coffee, tea, sugar, juices, processed foods, artificial ingredients, gum, sweeteners (whether natural or artificial), or cold cuts at first. Avoid preserved, fermented, canned, dried, smoked, pickled, and excessively salty foods.

After two weeks if you are feeling better, you can try adding back beef, pork, fish, citrus, tomato, coffee, tea, etc. one at a time for three days each to see if they bother you.

Keep in mind that any food can be a culprit, including any food on my hypo-allergenic Paleo diet, so some people may need to explore further, but the above diet removes all of the most common culprits.

These dietary experiments can be frustrating and difficult, but they can also be very illuminating. Once you have figured out your food sensitivities, it does not mean you can never eat that food again—that’s completely up to you—but at least you’ll have more control over how you feel from day to day if you want to!

What about you?

Have you been able to reduce your ADHD symptoms by making dietary changes? What has or has not worked for you?

If you are want to learn more more about ADHD and diet, you may be interested in my articles “Sugar and ADHD” and “Attention! Is Your Diet Causing ADHD?“

What is ADHD?

Attention deficit/hyperactivity disorder, or ADHD, affects about 4% of children and about 2% of adults. ADHD is a complex condition and poorly named, because it is not really an attention deficit—but rather an inability to regulate attention. People with ADHD have trouble directing attention to what’s most important and sustaining that attention for as long as required. This can cause all kinds of problems in school, at home, on the road, at work, and in relationships.

I would estimate that about a quarter of my students at Harvard University and Smith College present with a chief complaint of “difficulty concentrating.” When I worked at the Hallowell Center, which specializes in the treatment of people with attention-related disorders, 100% of clients came to me because of problems with focus and productivity. Nearly every psychiatric diagnosis—depression, anxiety, bipolar disorder, schizophrenia, substance abuse, and PTSD, just to name a few—can affect the ability to concentrate. Even common issues like stress or lack of sleep can impair attention. Therefore, the majority of people who have attention problems do not turn out to have ADHD after all, which is why a skilled psychiatric evaluation is so important in determining the underlying problem. Whether you are interested in treating ADHD with diet or simply improving your concentration, it is important to understand how diet affects attention regulation.

The chemistry of concentration

We psychiatrists are fond of saying that ADHD is caused by a chemical imbalance in the brain, and that medicines can help to correct the imbalance. There are at least two brain chemicals (or neurotransmitters) that seem to be involved in ADHD: dopamine and norepinephrine. These are tiny messengers that send signals from one brain cell to the next. If levels of dopamine or norepinephrine are too low, or if the system that processes these neurotransmitters is not functioning properly, a stimulant medication (like Ritalin or Adderall) might help by forcing brain cells to release higher amounts of these chemicals. But what causes the chemical imbalance in the first place? Why are the levels of these chemicals too low? And where do these chemicals come from?

Brain chemicals come from food.

After all, where else could they possibly come from? This seems so obvious, but many doctors don’t think about the connection. We are trained to think about which medications might correct the imbalance, not what causes it in the first place. So which foods does your body need to make these important chemicals?

Dopamine and norepinephrine are made from protein.

The body breaks down proteins in foods like fish, chicken, and beef into amino acids, and one of these amino acids is called tyrosine. The body then uses special chemical reactions to turn tyrosine into the dopamine and norepinephrine brain cells need to communicate with each other:

TYROSINE → DOPAMINE → NOREPINEPHRINE

Therefore, those not getting enough protein (especially at breakfast), may have difficulty concentrating. For more information about proteins and amino acids, including daily requirements and best food sources, see my Protein page.

The brain is mostly made of fat.

Yes, even yours. 🙂 About 2/3 of the brain is made of fat, and about 20% of that fat should consist of omega-3 fatty acids. Omega-3 fatty acids keep cell membranes flexible and healthy. Without these special polyunsaturated fats, brain cells become stiff and can’t communicate with each other easily. So even if there is plenty of dopamine and norepinephrine around, brain cells may not be able to pass these chemicals back and forth properly if the right fats aren’t built in to their membranes.

The brain is picky about omega-3s

There are 3 types of omega-3 fatty acids: ALA, DHA, and EPA. The brain’s favorite omega-3 fatty acid is called DHA. ALA is found in both plant and animal foods. Popular vegetarian sources of ALA include flaxseed, walnuts, and chia seeds. ALA is often called the “parent” omega-3 because of this pathway:

ALA → EPA → DHA

Looking at this pathway you might think that if you eat enough ALA, you’re all set. But here’s the problem—the body has a very hard time converting ALA to EPA and DHA, so about 95% of it remains stuck in the form of ALA. However, we convert EPA to DHA very easily. This means that in order to be sure our brain gets enough DHA, we need to eat EPA and DHA themselves. Plant foods do not contain any EPA or DHA. EPA and DHA are hard to find in the typical American diet because the best sources are wild animal foods, such as cold-water, fatty fish (like salmon and mackerel), and naturally-raised animals, such as grass-fed cows and pasture-raised chickens. This is why public health officials sometimes recommend omega-3 supplements. These supplements are typically in the form of fish oil, but there are also new vegan-friendly supplements available which are made from algae.

Omega-3s and ADHD

There have been many studies of omega-3 fatty acids in the treatment of ADHD, but most have shown no benefit or only modest improvement compared to medications. However, many experts seem to agree with this conclusion, quoted from a 2011 (Bloch) review:

“Based on the currently available evidence, using omega-3 fatty acid supplementation in lieu of traditional pharmacologic treatments is not recommended in children with significant ADHD symptoms. However, given the evidence of modest efficacy of omega-3 fatty acid supplementation and its relatively benign side-effect profile, omega-3 fatty acid supplementation, particularly with higher doses of EPA, is a reasonable treatment strategy as augmentation to traditional pharmacotherapy or for those families reticent to use psychopharmacologic agents.”

The bottom line is that medications seemed to work much better than omega-3 supplements. In the studies that did show a modest benefit from omega-3s, the doses of EPA that seemed to work best were between 300 and 600 mg per day. But wait . . . doesn’t the brain prefer DHA? Yes. Even though the brain loves and needs lots of DHA to work properly, researchers find that EPA supplements seem to work much better than DHA supplements. As these were short-term studies, the thinking is that EPA works better because of its fast-acting anti-inflammatory properties.

Is your brain unbalanced?

There’s another kind of essential polyunsaturated fatty acid we need to take into consideration: omega-6. Theoretically, if you eat too much omega-6 it is harder for the omega-3s to work properly because they compete with each other. Many scientists believe that these two types of polyunsaturated fats—the omega-3s and the omega-6s—need to be in balance for our brains and bodies to function at their best. Omega-6 fatty acids are found in a wide variety of plant and animal foods, but certain kinds of plant foods are extremely high in omega-6. Animal fats contain on average 10-20% omega-6, whereas vegetable oils, such as soybean, corn, peanut, and sunflower oils, contain 50-80% omega-6. The average American eats a diet that is far too high in omega-6 and far too low in omega-3. Would the omega-3 ADHD studies have been more impressive if the people in the experiments were also asked to reduce the amount of omega-6 they were eating? Hard to say . . .

For more information about omega-3 fatty acids, the difference between EPA and other omega-3s, best food sources, and how to improve your omega-3 balance, please see my Fats page.

Minerals are mandatory: iron and zinc

Iron is the most prevalent mineral in the body. When we think of iron, we usually think about its role in our red blood cells where it functions to carry oxygen from the lungs out to all of our cells. We don’t usually think of it as a brain mineral, but remember our neurotransmitter pathway from the top of this article? The first step on the road from tyrosine to dopamine and norepinephrine requires an enzyme called tyrosine hydroxylase, and this enzyme needs iron in order to do its job. Iron is also important in regulating dopamine function. Therefore, iron deficiency, which is relatively common, can impair concentration.

The second most common mineral in the body is zinc. Brain cells that release dopamine out into the synapse (space between cells where communication occurs) vacuum it back up using a dopamine transporter. This crucial transporter is regulated by zinc. Zinc binds to the dopamine transporter and slows it down, allowing dopamine to remain active in the synapse for a longer period of time before being pulled back into the cell to be recycled. It is essentially a natural dopamine reuptake inhibitor. Interestingly, this is also one of the ways in which stimulant medications work to improve dopamine activity.

There have been two clinical trials of zinc supplements in the treatment of ADHD, both of which noted some benefit. An Iranian study found that Ritalin + (15 mg of elemental) zinc given for six weeks worked twice as well as Ritalin + a sugar pill. A Turkish study found that (40 mg of elemental) zinc given for 12 weeks worked twice as well as a sugar pill.

Zinc and iron supplements can be hard to stomach. Zinc frequently causes nausea, and iron supplements can cause constipation and other gastrointestinal problems. Are there alternatives to supplements for people who have mineral deficiencies? What is causing these deficiencies in the first place? Are there dietary changes we can make that can improve our mineral status?

Plant foods are very low in zinc, whereas animal foods are excellent sources of zinc.

While both plant and animal foods contain iron, the type of iron found in animal foods (called heme iron) is 8 times more bioavailable (useful) to us than the type found in plant foods.

Seed foods (which include grains, beans, and nuts) contain phytic acid, which interferes with our ability to absorb essential minerals. For more information, including a surprising study illustrating the degree that phytic acid interferes in zinc absorption, see my “Micronutrients and Mental Health” article.

Some plant foods contain tannins, which interfere with iron absorption. For more information, please see my Fruits page.

Tips for treating ADHD with diet

• Be sure to eat some protein at breakfast
• Include foods rich in omega-3 fatty acids in your diet (healthy animal foods), or take a daily supplement containing at least 300 mg of EPA
• Reduce omega-6 intake by minimizing vegetable oils, nuts, and seeds
• Improve mineral absorption by reducing phytic acid intake (minimize grains, beans, nuts and seeds)
• If you have iron deficiency, increase meat intake and reduce phytic acid intake (grains, beans, nuts, and seeds) and/or take a heme iron supplement.
• Improve zinc status by reducing phytic acid intake (minimize grains, beans, nuts, and seeds), and including animal foods in your diet. Zinc supplements may also be helpful.
• If you eat a vegan or vegetarian diet, please see my see my “Micronutrients and Mental Health” article for information about how to optimize your mineral status.

So, paying more attention to the quality of your diet just might help you pay more attention to . . . everything.

Learn more about how to treat your ADHD with diet in my posts “Sugar and ADHD” and “Food Sensitivities and ADHD.”

What is ADHD?

Attention deficit/hyperactivity disorder, or ADHD, affects about 4% of children and about 2% of adults. ADHD is a complex condition and poorly named, because it is not really an attention deficit—but rather an inability to regulate attention. People with ADHD have trouble directing attention to what’s most important and sustaining that attention for as long as required. This can cause all kinds of problems in school, at home, on the road, at work, and in relationships.

I would estimate that about a quarter of my students at Harvard University and Smith College present with a chief complaint of “difficulty concentrating.” When I worked at the Hallowell Center, which specializes in the treatment of people with attention-related disorders, 100% of clients came to me because of problems with focus and productivity. Nearly every psychiatric diagnosis—depression, anxiety, bipolar disorder, schizophrenia, substance abuse, and PTSD, just to name a few—can affect the ability to concentrate. Even common issues like stress or lack of sleep can impair attention. Therefore, the majority of people who have attention problems do not turn out to have ADHD after all, which is why a skilled psychiatric evaluation is so important in determining the underlying problem. Whether you are interested in treating ADHD with diet or simply improving your concentration, it is important to understand how diet affects attention regulation.

The chemistry of concentration

We psychiatrists are fond of saying that ADHD is caused by a chemical imbalance in the brain, and that medicines can help to correct the imbalance. There are at least two brain chemicals (or neurotransmitters) that seem to be involved in ADHD: dopamine and norepinephrine. These are tiny messengers that send signals from one brain cell to the next. If levels of dopamine or norepinephrine are too low, or if the system that processes these neurotransmitters is not functioning properly, a stimulant medication (like Ritalin or Adderall) might help by forcing brain cells to release higher amounts of these chemicals. But what causes the chemical imbalance in the first place? Why are the levels of these chemicals too low? And where do these chemicals come from?

Brain chemicals come from food.

After all, where else could they possibly come from? This seems so obvious, but many doctors don’t think about the connection. We are trained to think about which medications might correct the imbalance, not what causes it in the first place. So which foods does your body need to make these important chemicals?

Dopamine and norepinephrine are made from protein.

The body breaks down proteins in foods like fish, chicken, and beef into amino acids, and one of these amino acids is called tyrosine. The body then uses special chemical reactions to turn tyrosine into the dopamine and norepinephrine brain cells need to communicate with each other:

TYROSINE → DOPAMINE → NOREPINEPHRINE

Therefore, those not getting enough protein (especially at breakfast), may have difficulty concentrating. For more information about proteins and amino acids, including daily requirements and best food sources, see my Protein page.

The brain is mostly made of fat.

Yes, even yours. 🙂 About 2/3 of the brain is made of fat, and about 20% of that fat should consist of omega-3 fatty acids. Omega-3 fatty acids keep cell membranes flexible and healthy. Without these special polyunsaturated fats, brain cells become stiff and can’t communicate with each other easily. So even if there is plenty of dopamine and norepinephrine around, brain cells may not be able to pass these chemicals back and forth properly if the right fats aren’t built in to their membranes.

The brain is picky about omega-3s

There are 3 types of omega-3 fatty acids: ALA, DHA, and EPA. The brain’s favorite omega-3 fatty acid is called DHA. ALA is found in both plant and animal foods. Popular vegetarian sources of ALA include flaxseed, walnuts, and chia seeds. ALA is often called the “parent” omega-3 because of this pathway:

ALA → EPA → DHA

Looking at this pathway you might think that if you eat enough ALA, you’re all set. But here’s the problem—the body has a very hard time converting ALA to EPA and DHA, so about 95% of it remains stuck in the form of ALA. However, we convert EPA to DHA very easily. This means that in order to be sure our brain gets enough DHA, we need to eat EPA and DHA themselves. Plant foods do not contain any EPA or DHA. EPA and DHA are hard to find in the typical American diet because the best sources are wild animal foods, such as cold-water, fatty fish (like salmon and mackerel), and naturally-raised animals, such as grass-fed cows and pasture-raised chickens. This is why public health officials sometimes recommend omega-3 supplements. These supplements are typically in the form of fish oil, but there are also new vegan-friendly supplements available which are made from algae.

Omega-3s and ADHD

There have been many studies of omega-3 fatty acids in the treatment of ADHD, but most have shown no benefit or only modest improvement compared to medications. However, many experts seem to agree with this conclusion, quoted from a 2011 (Bloch) review:

“Based on the currently available evidence, using omega-3 fatty acid supplementation in lieu of traditional pharmacologic treatments is not recommended in children with significant ADHD symptoms. However, given the evidence of modest efficacy of omega-3 fatty acid supplementation and its relatively benign side-effect profile, omega-3 fatty acid supplementation, particularly with higher doses of EPA, is a reasonable treatment strategy as augmentation to traditional pharmacotherapy or for those families reticent to use psychopharmacologic agents.”

The bottom line is that medications seemed to work much better than omega-3 supplements. In the studies that did show a modest benefit from omega-3s, the doses of EPA that seemed to work best were between 300 and 600 mg per day. But wait . . . doesn’t the brain prefer DHA? Yes. Even though the brain loves and needs lots of DHA to work properly, researchers find that EPA supplements seem to work much better than DHA supplements. As these were short-term studies, the thinking is that EPA works better because of its fast-acting anti-inflammatory properties.

Is your brain unbalanced?

There’s another kind of essential polyunsaturated fatty acid we need to take into consideration: omega-6. Theoretically, if you eat too much omega-6 it is harder for the omega-3s to work properly because they compete with each other. Many scientists believe that these two types of polyunsaturated fats—the omega-3s and the omega-6s—need to be in balance for our brains and bodies to function at their best. Omega-6 fatty acids are found in a wide variety of plant and animal foods, but certain kinds of plant foods are extremely high in omega-6. Animal fats contain on average 10-20% omega-6, whereas vegetable oils, such as soybean, corn, peanut, and sunflower oils, contain 50-80% omega-6. The average American eats a diet that is far too high in omega-6 and far too low in omega-3. Would the omega-3 ADHD studies have been more impressive if the people in the experiments were also asked to reduce the amount of omega-6 they were eating? Hard to say . . .

For more information about omega-3 fatty acids, the difference between EPA and other omega-3s, best food sources, and how to improve your omega-3 balance, please see my Fats page.

Minerals are mandatory: iron and zinc

Iron is the most prevalent mineral in the body. When we think of iron, we usually think about its role in our red blood cells where it functions to carry oxygen from the lungs out to all of our cells. We don’t usually think of it as a brain mineral, but remember our neurotransmitter pathway from the top of this article? The first step on the road from tyrosine to dopamine and norepinephrine requires an enzyme called tyrosine hydroxylase, and this enzyme needs iron in order to do its job. Iron is also important in regulating dopamine function. Therefore, iron deficiency, which is relatively common, can impair concentration.

The second most common mineral in the body is zinc. Brain cells that release dopamine out into the synapse (space between cells where communication occurs) vacuum it back up using a dopamine transporter. This crucial transporter is regulated by zinc. Zinc binds to the dopamine transporter and slows it down, allowing dopamine to remain active in the synapse for a longer period of time before being pulled back into the cell to be recycled. It is essentially a natural dopamine reuptake inhibitor. Interestingly, this is also one of the ways in which stimulant medications work to improve dopamine activity.

There have been two clinical trials of zinc supplements in the treatment of ADHD, both of which noted some benefit. An Iranian study found that Ritalin + (15 mg of elemental) zinc given for six weeks worked twice as well as Ritalin + a sugar pill. A Turkish study found that (40 mg of elemental) zinc given for 12 weeks worked twice as well as a sugar pill.

Zinc and iron supplements can be hard to stomach. Zinc frequently causes nausea, and iron supplements can cause constipation and other gastrointestinal problems. Are there alternatives to supplements for people who have mineral deficiencies? What is causing these deficiencies in the first place? Are there dietary changes we can make that can improve our mineral status?

Plant foods are very low in zinc, whereas animal foods are excellent sources of zinc.

While both plant and animal foods contain iron, the type of iron found in animal foods (called heme iron) is 8 times more bioavailable (useful) to us than the type found in plant foods.

Seed foods (which include grains, beans, and nuts) contain phytic acid, which interferes with our ability to absorb essential minerals. For more information, including a surprising study illustrating the degree that phytic acid interferes in zinc absorption, see my “Micronutrients and Mental Health” article.

Some plant foods contain tannins, which interfere with iron absorption. For more information, please see my Fruits page.

Tips for treating ADHD with diet

• Be sure to eat some protein at breakfast
• Include foods rich in omega-3 fatty acids in your diet (healthy animal foods), or take a daily supplement containing at least 300 mg of EPA
• Reduce omega-6 intake by minimizing vegetable oils, nuts, and seeds
• Improve mineral absorption by reducing phytic acid intake (minimize grains, beans, nuts and seeds)
• If you have iron deficiency, increase meat intake and reduce phytic acid intake (grains, beans, nuts, and seeds) and/or take a heme iron supplement.
• Improve zinc status by reducing phytic acid intake (minimize grains, beans, nuts, and seeds), and including animal foods in your diet. Zinc supplements may also be helpful.
• If you eat a vegan or vegetarian diet, please see my see my “Micronutrients and Mental Health” article for information about how to optimize your mineral status.

So, paying more attention to the quality of your diet just might help you pay more attention to . . . everything.

Learn more about how to treat your ADHD with diet in my posts “Sugar and ADHD” and “Food Sensitivities and ADHD.”