Category: Nutrition

Meat has a bad reputation. Most people think of meat, especially red meat, as dangerously unhealthy. However, meat has unique properties that make it more nutritious, easier to digest, and less likely to irritate your body than vegetables. Does the science behind meat-phobia hold up under the microscope?

Is red meat less healthy than other kinds of meat?

Meat is made of animal muscle fibers, which come in two major types: fast and slow. Dark muscle fibers (“slow” fibers) are designed for endurance activities, whereas light muscle fibers (“quick” fibers) are designed for rapid bursts of activity and tire easily. Therefore, dark muscle fibers have greater energy needs. For muscles to make energy, they need an energy source (fat), oxygen to burn the fat, and vitamins and minerals to run the reactions that release the energy from the fat. Therefore, dark meats usually contain more more fat, vitamins and minerals than light/white meats.

To hold the oxygen, dark (slow) muscle fibers need larger amounts of an oxygen carrier protein called myoglobin. Myoglobin is red, which is why red meat is red. Myoglobin is rich in iron, the mineral that binds oxygen, so red meats contain more iron than white meats. Because most dark meats contain more fat than light meats, they can be higher in calories. However, because dark meats also contain more minerals and B vitamins, they are actually more nutritious than light meats.

Did you know that all types of meat—red, light, and white—whether from mammals, birds, or fish—contain about the same amount of cholesterol? There is no more cholesterol in a pound of steak than in a pound of chicken.

But doesn’t red meat increase risk of death?

A study conducted at the Harvard School of Public Health [Pan 2012] claimed that eating red meat increases our risk of death from all kinds of diseases, including heart disease and cancer. This was an epidemiological study, which, by its very nature, is incapable of proving cause and effect; therefore, even if it were the best epidemiological study ever done on the planet, it would be impossible for the authors to conclude that red meat causes death.

Below are just two of the problems I noticed in this study:

1. There were two huge groups of people in this study: the Nurses’ Health Study (over 120,000 women) and the Health Professionals Follow-up study (over 50,000 men). Every 2 years, the nurses were asked how often they had eaten red meat over the past 2 years. Every 4 years, the male health professionals were asked how often they had eaten red meat over the previous 12 months. Can you imagine? Even though I keep track of what I eat in a daily food record, if you asked me what I ate LAST WEEK (never mind 1 to 2 years ago), I honestly couldn’t tell you. Naturally, these questionnaires can’t tell us how often people forget, underestimate, or perhaps even lie about what they were actually eating.
2. It just so happened that the people who reported eating the most red meat per day, also happened to be more likely to:

• smoke cigarettes
• be sedentary
• weigh more
• have diabetes
• take aspirin
• eat more calories per day
• drink more alcohol
• eat more dairy products

These are all excellent examples of what researchers call “confounding variables.” Confounding—translation? Confusing. Even if all of the data are accurate, how can we really know whether the people who ate more red meat were more likely to die because of the red meat, or because of one or more of these other issues?

For a more detailed critique of this study, please see Gary Taubes’ excellent blogpost, entitled “Science, Pseudoscience, Nutritional Epidemiology, and Meat.”

Are saturated fat and cholesterol bad for my heart?

Numerous studies by cardiology researchers have finally disproved the myths that dietary fat, meat, and cholesterol cause heart disease. In fact, some of the healthiest diets in human history have been very high in meat and animal fat. To read more about this topic, please see my post “The History of All-Meat Diets.” We have been eating animal meats, animal fat, and cholesterol for about two million years, but heart disease has only been a major problem for us for about 50 years. The major culprit is therefore much more likely to be something that is NEW in our diets; the current evidence points most strongly to refined and high glycemic index carbohydrates, not fat, meat, or cholesterol. To read more about how sugar raises “bad” cholesterol levels and why dietary cholesterol is not bad for you, please see my cholesterol page. To read more about the connection between sugar, insulin resistance, and heart disease, please see my post “Why Sugar is Bad For You: A Summary of the Research.” To see an example of how researchers desperately twist logic in an effort to connect red meat to heart disease, please see my post “Does Carnitine From Red Meat Cause Heart Disease?“

Does red meat cause cancer?

If meat is so carcinogenic, why was cancer so uncommon until the last century or so? We are not eating any more meat now than we did a hundred years ago, yet cancer incidence is skyrocketing. So, why do we believe that meat causes cancer?

There have been numerous research studies claiming to tie red meat to cancer (particularly colon cancer), however, these were weak epidemiological studies, and are not representative of results in the field as a whole. The fact is that studies of meat and cancer yield very mixed results. Many studies show no connection at all between meat and cancer, and some studies even show a protective benefit. There is simply no solid scientific evidence to support the belief that red meat increases cancer risk.

This did not stop the World Health Organization (WHO) from proclaiming to the planet in October 2015 that red and processed meats cause cancer. Unfortunately, the WHO report is all smoke and mirrors. To see what I mean, please read my detailed analysis of the WHO report: “WHO Says Meat Causes Cancer?“

Charred meats and cancer

Charred meats and wood-smoked meats contain “PAHs” (polycyclic aromatic hydrocarbons) and “HCAs” (heterocyclic amines). PAHs and HCAs have been shown to cause cancer in lab animals. Studies in humans are limited to epidemiological studies, and even these have been inconclusive.

PAHs are present not just in charred meats, but also in anything organic (plant/animal matter) that has been burned–from cigarettes to forest fire smoke to automobile exhaust. PAHs are also present in many other foods, such as cereals, vegetable oils, cheese, and coffee. In fact, cereal products, not meats, are the biggest sources of PAHs in the typical diet.

HCAs, on the other hand, can only be formed from protein-rich foods, such as meat, fish, and poultry.

Grilled and fried chicken can contain even higher amounts of PAHs and HCAs than grilled red meats, yet studies have shown no connection between poultry intake and cancer.

Nitrates and nitrites in processed meats

Nitrates and nitrites are used in the production of processed meats like bacon, salami, and ham. However, they are also found naturally in many plant foods, often in very high amounts. For example, pound for pound, spinach contains at least 30 times more of these compounds than hot dogs do (see table to the left1). In fact, some manufacturers of processed meats boast that they use celery powder (very high in nitrate), instead of the more commonly used sodium nitrite to preserve their meats.

What is the difference between nitrates and nitrites? It can be confusing because these terms are often used interchangeably by food manufacturers, physicians, and nutritionists. The reason why people lump them together so often is because nitrates easily turn into nitrites in foods and in the body. Nitrates and nitrites are very similar chemical salts with very similar properties, and mixtures of nitrates and nitrites are often used in food processing. Nitrites are about three times more potent than nitrates as preservatives.

In combination with salt, nitrates and nitrites prevent the growth of the bacteria that causes botulism (a type of food poisoning). They also act as antioxidants, keeping the fat in the meat from turning rancid, and giving the meat an unnatural pink color. Nitrates and nitrites themselves have not been shown to cause cancer; however, they can react with proteins in the meat to form nitrosamines, which are known to cause cancer in laboratory animals. The addition of special antioxidants during processing cuts down on this chemical reaction and reduces the amount of nitrosamine formed, but doesn’t eliminate it completely. Therefore it is best to choose fresh, unprocessed meats when possible.

It may also be wise to limit intake of vegetables that are very high in nitrates, such as spinach and celery. Bacteria in our saliva convert vegetable nitrates into nitrites, which we swallow. These nitrites can then react with proteins in our stomach to form nitrosamines, exactly the same way they do during meat processing. These nitrosamines are potential carcinogens; this is why some researchers believe that diets high in nitrates are associated with increasing rates of stomach cancer.

Will animal protein damage my kidneys?

To the best of my knowledge, there’s no clinical trial evidence for it so far. The human kidney is designed to be able to handle large quantities of animal protein, perhaps because our ancestors would have sometimes needed to eat large amounts of meat at one sitting, instead of eating smaller portions several times per day every day, the way we modern people do.

The vast majority of studies suggesting a connection between high protein intake and kidney damage have been conducted on laboratory animals or have been epidemiological studies. A 2011 review of the research [Odermatt] examining the connection between diet and kidney disease cited only a single human clinical trial designed to explore this question, and the results were very reassuring:

“Serum creatinine levels and estimated glomerular filtration rate did not change in individuals with normal renal function after 1 yr of a low-carbohydrate diet with higher protein (35% kcal from protein compared with 24%) and fat intake (61% compared with 30%).”

A study done in 1930 of two men who ate a 100% meat diet for a full year revealed no signs of kidney problems whatsoever. [McLellan]

Meat is the only nutritionally complete food

Animal foods (particularly when organ meats are included) contain all of the protein, fat, vitamins and minerals that humans need to function. They contain absolutely everything we need in just the right proportions. That makes sense, because for most of human history, these would have been the only foods available just about everywhere on the planet in all seasons.

Below you can see that animal products are superior sources of most essential vitamins and minerals, including 4 that do not exist in plant foods at all:

Meat nutrients are ready-to-use.

In contrast to vegetables, meat does not contain any “anti-nutrients”, like cellulose, phytates and tannins that interfere with digestion or absorption of vital compounds such as vitamins and minerals.

The forms of vitamins and minerals in meat are the easiest forms to absorb:

• “Heme” iron, the form of iron found in meat, is at least 3 times more available to our bodies than “non-heme” (vegetable) iron.
• Vitamin A from animal sources is 12 to 24 times more available to us than vegetarian sources.
• Vitamins B12 and K2 are only found in animal foods.

Meat is naturally low in carbohydrate

This means that it is impossible to eat meat and generate a significant insulin spike. Insulin spikes are to be avoided as much as possible, as they seriously destabilize our brain and body chemistry and can lead to inflammation, cell damage, disruption of cholesterol and fat metabolism, and numerous chronic diseases.

Meat is gentle on your delicate system.

While vegetables protect themselves with chemicals that are potentially harmful to our cells, animals protect their meat with claws and fangs, so meat itself does not contain any irritating substances. Meat is an especially friendly choice if you tend to be chemically sensitive.

Is meat hard to digest?

Quite the opposite. Meat is efficiently broken down by our own natural enzymes, so we do not need to rely on intestinal bacteria to help us digest it. This means that there are virtually no intestinal gases produced in the process. Meat is efficiently absorbed by our intestines, so there is very little wasted. The belief that meat contributes to constipation is a myth. Unless you have a specific sensitivity to a certain type of meat, you will have no trouble digesting it. Meat can, however, become “trapped” in your digestive tract behind sluggish high-fiber plant foods and dairy products, which are very difficult to digest.

What about meat and gout?

Please see my blog article: “Got Gout but Love Meat?“

Can eating meat cause iron overload?

I find no evidence in the scientific or medical literature linking meat consumption to iron overload. It is true that too much iron can be toxic to cells, and it is true that the body has no way to get rid of excess iron other than through the shedding of skin and intestinal cells or through bleeding. However, the body is very smart and knows not to absorb too much iron. The liver releases a hormone called hepcidin which monitors our iron status and tells our intestinal cells exactly how much iron to absorb. On average, we lose 1 to 3 mg of iron per day, so this is approximately how much we absorb.

Every article I found about iron overload in humans, including an excellent 2012 review in the New England Journal of Medicine, had to do with health conditions that disrupt normal iron metabolism, not with simple overindulgence in red meat. These include hemochromatosis and other genetic disorders of iron metabolism, certain enzyme deficiency disorders, liver disease (alcohol-induced liver damage, viral hepatitis), multiple blood transfusions, and iron supplement overdose (as opposed to red meat overdose). There is also a common non-genetic health problem that can disrupt normal iron processing in the liver called “dysmetabolic hyperferritinemia.” DH is seen in some individuals who have severe metabolic syndrome, usually with fatty liver. While iron deficiency is a very common diet-related condition, diet-induced iron overload does not seem to exist in otherwise healthy people.

What types of meat are healthiest to eat?

Healthy, naturally-raised animals fed their natural diets produce meats with healthier fat profiles, including higher levels of essential omega-3 fatty acids than grain-fed animals.

Avoid factory-farmed, grain-fed animals when you can. Whenever possible and affordable, choose meat products from naturally-raised animals. This means animals that have been fed a diet most similar to what they would eat if they were living in the wild:

• Cows/Lambs/Sheep—grasses
• Chickens—grasses, insects, worms
• Turkeys—grasses, insects, seeds, small animals
• Ducks/geese—fish, grass, algae, insects, fruits
• Pigs— grasses, root vegetables, fruits, nuts, insects, worms, small animals
• Fish—wild, not farmed. Food varies depending on species.

Poultry sellers often boast that their birds are fed an all-vegetarian diet, but if you notice above, birds are naturally omnivores and eat small creatures for protein and fat (worms and insects, for example). This is why backyard birds enjoy suet (animal fat) in the wintertime—insects and worms are scarce in winter and they need the fat and protein for energy.

Does Meat Quality Matter?

It is best for human health, environmental health and animal health and welfare reasons to choose meats raised humanely and sustainably from healthy animals being fed a species-appropriate diet: pasture-raised land animals, wild-caught seafood and wild game. However, not everyone can afford or consistently access animal foods that meet all of these criteria.

Purchasing meat, poultry, and eggs from local community supported agriculture organizations or from responsible online seafood, poultry and red meat distributors can be a reasonably cost-effective way to access high quality, nutritious animal foods. Ask your local butcher or grocery store which of their animal foods are raised in the most ethical, healthy ways. It may be helpful to know that some of the most nutritious cuts of meat are often also the least expensive: bone-in/skin-on chicken thighs, chicken wings/legs, pork butt and pork shoulder, whole chickens, liver and organ meats of all kinds, full-fat ground beef or ground pork, and dark ground turkey meat are good examples. If you live on a coast, consider highly nutritious and affordable fresh shellfish such as mussels and clams.

Don’t let the perfect be the enemy of the good. If you can’t afford or consistently access best choices, know that eating conventionally raised animal foods is still far healthier for you than eating processed and sweetened foods. Eggs, canned tuna/sardines/mackerel, rotisserie chicken, and even many simple deli meats are good options when you’re too busy to cook or on the run.

You can learn more about how to choose and support sustainable animal foods by visiting the Ethical Omnivore resources page.

Bottom line about meat and health:

• Healthy animal foods are wholesome and nutritionally complete.
• Meat is easy to digest and absorb, and contains no anti-nutrients or irritating substances.
• There is no evidence that meat, saturated fat, or cholesterol are harmful to human health. In fact, there is plenty of evidence that meat, saturated fat and cholesterol are vital to health.
• Whenever possible, choose healthy meats from naturally-raised animals.
• Limit processed meats.
• When eating grilled meats, you may want to trim away any burned or blackened edges.

Poor cholesterol—so misunderstood. All animal cells require cholesterol for proper structure and function. The vast majority of cholesterol in the body does not come directly from foods like eggs and meat, but from the liver, which can make cholesterol out of anything we eat. So, if cholesterol-rich foods don’t cause high cholesterol, what does?

What is cholesterol?

Most people have no idea what cholesterol actually is.

Life without cholesterol would be impossible. Cell membranes, which wrap around and protect the inner contents of all cells, must contain cholesterol in order to function properly. Cholesterol contributes firmness to membranes and keeps them from falling apart. But wait, there’s more!

All of the following critical body components are made from cholesterol:

• Estrogen
• Testosterone
• Progesterone
• Cortisol (anti-inflammatory stress hormone)
• Aldosterone (regulates salt balance)
• Vitamin D
• Bile (required for fat and vitamin absorption)
• Brain synapses (neurotransmitter exchange)
• Myelin sheath (insulates nerve cells)

What is the difference between fat and cholesterol?

Cholesterol is made of carbon, hydrogen, and oxygen, just like fat is, but it is not fatty; it is a hard, waxy substance that contains no fat. A molecule of fat looks like this:

whereas a molecule of cholesterol looks like this:

As you may be able to appreciate just by looking at them, they are very different from each other.

Fat is a simple long chain, whereas cholesterol is mainly a complicated combination of rings—3 hexagons plus a pentagon; in medical school we affectionately called it “three rooms and a bath.” Fat is relatively easy to build (11 chemical steps from acetyl-coA to triacylglycerol), whereas cholesterol is hard to construct—more than 30 chemical steps are required to build one molecule of cholesterol (from acetyl-coA to cholesterol). The body would not go to the trouble of making it for no reason. Especially since, as it turns out, once it’s built, it’s impossible for the body to break it down—we do not have any way to take apart its complex ringed structure.

Cholesterol in foods

How much cholesterol do we need to eat?

None. Cholesterol is so important that the body can make cholesterol out of anything—fats, carbohydrates, or proteins. You don’t have to eat cholesterol to make cholesterol. Even if you eat a completely cholesterol-free diet, as vegans do, your body will still make cholesterol. Type “vegans with high cholesterol” into your search engine and you will find plenty of accounts of vegans whose cholesterol is too high—despite the fact that they eat ZERO grams of cholesterol.

Which foods contain cholesterol?

Since every single animal cell contains cholesterol, all animal foods contain cholesterol.

Many people don’t realize that all muscle meats (chicken, fish, beef, pork, etc.) contain about the same amount of cholesterol per serving.

Certain animal foods—liver, egg yolk, dairy fats, glandular organ meats, and brain— are especially high in cholesterol. Why is that? Liver is where the body manufactures cholesterol. Egg yolks contain concentrated cholesterol because the growing baby chick needs it to build new cells. Milk fat contains lots of cholesterol because the growing baby calf needs it to build new cells. Glandular organ meats (pancreas, kidney, etc.) contain more cholesterol because glands make hormones, and hormones are made from cholesterol. Brain contains very high amounts of cholesterol in its myelin sheaths, which insulate its electrical circuits.

All plant foods are considered “cholesterol-free.” Well, it would be more accurate to say that plant foods do not contain any animal cholesterol. Plants contain their own special forms of cholesterol called “phytosterols”, but phytosterols are toxic to human cells, so our intestines wisely refuse to absorb them.

So, in most cases, animal foods contain some cholesterol that the body can absorb and use, and all plant foods contain cholesterol that our body cannot absorb. The only exceptions I know of to these rules are shellfish.

There are two types of shellfish: crustaceans (lobsters, shrimp, crabs, etc.) and mollusks (clams, oysters, mussels, etc.). Crustaceans—giant sea insects who hunt for their food—contain animal cholesterols that can be absorbed by the body, but mollusks—who gather nutrients by filtering seawater—contain a different type of cholesterol that we can’t absorb.

In fact, plant cholesterols and mollusk cholesterols are not only rejected by our intestinal cells, they actually interfere with the absorption of animal cholesterols. This is how margarines such as Benecol® work. The manufacturer has added a chemically altered form of plant cholesterol to the spread, which interferes with the absorption of animal cholesterol.

Will eating cholesterol raise my cholesterol?

Yes, but only if your body needs more cholesterol.

The cells lining the small intestine each contain transporter molecules (NPC1L1) that absorb cholesterol. [The cholesterol-lowering drug Zetia® works by blocking NPC1L1 yet does not reduce risk of heart disease]. However, if the body doesn’t need any more cholesterol, there are other molecules (ABCG5/8 transporters) that pump the cholesterol right back out into the intestines to be eliminated from the body. This is one reason why it is virtually impossible for cholesterol from food to cause “high cholesterol.” The intestinal cells know exactly how much is needed and will not allow extra to be absorbed.

This is brilliant when you think about it (the body is so smart)—it is impossible for the body to break down the complex structure of the cholesterol molecule, so it would make no sense to absorb too much—once it’s inside the body there’s only one way to get rid of it, and that is to excrete it in the bile. Why take in more than necessary, if it’s just going to have to be eliminated?

However, if your body cholesterol levels are low, the intestinal cells will not kick it out, and it will make it into your bloodstream—because you need it.

What’s more, cholesterol is recycled very efficiently by our bodies, because it is so hard to make. Why make more from scratch if you don’t have to? Remember that it’s also impossible for the body to break down cholesterol, so the only way to get rid of it is to excrete it. The liver gets rid of any excess by excreting free cholesterol into the intestines along with bile. This free form of cholesterol is the only form that intestinal cells are able to absorb. Most of the cholesterol molecules in food (85 to 90% of them) are not free; they are in the form of “cholesterol esters.” [Cholesterol esters are just cholesterol molecules with a fatty acid attached]. Intestinal cells are incapable of absorbing cholesterol ester, which is the major form of cholesterol in food. Therefore, if the intestinal cells sense that the body needs more cholesterol, it will typically reabsorb most of what the body needs from the bile, not from food.

To summarize the relationship between food cholesterol and blood cholesterol:

1. Most cholesterol from food does not get absorbed unless body levels are low.
2. The amount of cholesterol you eat has almost no effect on your cholesterol levels.
3. The vast majority of cholesterol in your body is made by your body’s own cells. Remember that creepy line from the movie When a Stranger Calls? “The call is coming from inside the house.” The excess cholesterol is coming from inside your body, not from the food you eat.

How does the body make cholesterol?

All cells can make their own cholesterol, but liver cells are especially good at it. Only liver cells are capable of making more than they need for themselves—and shipping it out to other parts of the body.

Remember how it takes more than 30 chemical reactions to build one molecule of cholesterol? The most important of all of these steps is step #3. In this step, a critical enzyme called “HMG-CoA reductase” converts a molecule called HMG-CoA into another molecule called mevalonate. Once this step occurs, there’s no turning back, so it’s a big commitment. This reaction is the one that determines whether or not cholesterol gets made. Therefore, the enzyme that runs this reaction, HMG-CoA reductase, is very important—it’s like the foreman in charge of the cholesterol assembly line. This enzyme needs to be carefully controlled, because we don’t want cells wasting their time and energy building expensive cholesterol molecules willy-nilly.

The activity of this critical enzyme HMG-CoA reductase is controlled primarily by two things:

1. cholesterol levels inside the cell
2. insulin levels in the blood.

This is where things get really interesting. It makes sense that HMG-CoA reductase would respond to the cell’s cholesterol levels—if the cell’s levels are low, you want to turn that enzyme on, so you can make more cholesterol, and if the cell has enough cholesterol, you want to turn that enzyme off and stop making cholesterol. But what is insulin doing in the mix?

We think of insulin as a blood sugar regulator, but its real job is to be a growth hormone. Insulin is supposed to turn on when we need to grow. What do we need to make in order to grow? More cells. What do we need to form new cells? Cholesterol. So, at times when we need to grow (babies, teenagers, pregnant women), insulin turns the enzyme HMG-CoA reductase ON, which tells cells to make more cholesterol, so we can build new cells.

What causes high cholesterol?

Why would the body make more cholesterol than it needs?

Now here’s the problem: when people eat too many sugars and starches, especially refined and high glycemic index foods, blood insulin levels can spike. When insulin spikes, it turns on HMG–CoA reductase, which tells all of the body’s cells to make more cholesterol, even if they don’t need any more. This is probably the most important reason why some people have too much cholesterol in their bloodstream. Sugars and starches can raise insulin levels, which fools the body into thinking it should grow when it doesn’t need to. This is how low glycemic index diets and low-carbohydrate diets normalize cholesterol patterns—these diets reduce insulin levels, which in turn lower HMG-CoA reductase activity.

“Statin” drugs, such as Lipitor®, which are prescribed to lower cholesterol levels, work partly by interfering with the activity of HMG-CoA reductase. If your cells happen to need more cholesterol under certain circumstances, but the statin drug is blocking this critical enzyme, your cells may not be able to make cholesterol when needed. And what’s worse is that the cholesterol synthesis pathway doesn’t just make cholesterol; branches of this same pathway are responsible for synthesizing a wide variety of other important molecules, including: Vitamin A, Vitamin E, Vitamin K, and Coenzyme Q. So, you may want to think twice before you artificially interfere with this pathway by taking a statin drug.

When you eat less carbohydrate, you are not artificially blocking the pathway; you are simply allowing HMG-CoA reductase to listen to other more important signals (such as cholesterol levels and growth requirements) and decide naturally when it should turn on and when it should turn off.

So, to recap: refined carbohydrates speed up the cholesterol assembly line and statins slow it down. Which approach would you rather take to manage your “cholesterol problem”—taking a drug that artificially slows down this assembly line, or changing your diet so that the assembly line only runs when it’s supposed to? [Hint: Dietary changes require no monthly co-pays, and have no potentially dangerous side effects. I write about the dangerous brain side effects of statins in my Psychology Today post: “Low Brain Cholesterol—Separating Fact from Fiction.”]

Chances are: if you have “high cholesterol” you do not have a cholesterol problem—you have a carbohydrate problem.

Good cholesterol and bad cholesterol

This gets into the very complicated relationship between cholesterol blood tests and heart disease risk. This is an enormous topic, but I’ll summarize some basic points.

When you get your cholesterol levels checked, you will see numbers for HDL and LDL, as well as triglycerides. Triglycerides are fats, so we’ll set them aside and just focus on HDL and LDL.

HDL particles collect extra cholesterol from around the body and carry it back to the liver to be eliminated from the body if we don’t need it. It is typically thought of as “good cholesterol” so higher HDL levels are considered a good sign.

LDL particles carry extra cholesterol made in the liver out to the rest of the cells in the body. We used to think of LDL as “bad cholesterol” so lower levels of LDL were considered a good sign.

The cholesterol inside of HDL and LDL particles is exactly the same, it’s just that, for the most part, HDL is carrying it in one direction and LDL is carrying it in the opposite direction. The reason why LDL had been dubbed “bad” and HDL has been dubbed “good” is that numerous epidemiological studies (most famously, the Framingham Heart Study) told us that high LDL levels were associated with a higher risk of heart attack, and that high HDL levels were associated with a lower risk of heart attack.

We used to think that HDL was good because it acted like a garbage truck, clearing evil cholesterol out of our bodies, and we used to think that LDL was bad because it burrowed its way into our coronary arteries, depositing evil cholesterol there—forming plaques and causing heart attacks.

Cholesterol, carbohydrates and heart disease

However, this simplistic way of thinking about cholesterol and heart disease is changing before our very eyes. It turns out that it is more complicated than this. LDL, for example, exists in a variety of forms. It can be big and buoyant and “fluffy” or small and dense and oxidized (damaged). The new thinking is that small, dense, oxidized LDL may be the only type of LDL that is associated with heart disease. Therefore, instead of thinking of all LDL as “bad”, it would be more accurate to say that all LDL is not created equal—big fluffy LDL is “good” and small, dense, oxidized LDL is “bad.”

Unfortunately, standard blood tests can’t tell you which type of LDL you have because it lumps all types of LDL particles together. Standard tests can only estimate how much of your cholesterol is travelling inside of LDL particles. They can’t tell you how many LDL particles you have, how big they are, how dense they are, or how oxidized they are. [For a detailed explanation of the complexities involved in interpreting cholesterol blood test results, I recommend Dr. Peter Attia’s blog at www.eatingacademy.com.]

What we do know from research studies is that people who eat a diet high in refined carbohydrates tend to have a higher number of “bad” (smaller, denser, oxidized) LDL particles. This makes sense, because we know that carbohydrates are “pro-oxidants”—meaning they can cause oxidation.

There is also lots of evidence telling us that refined carbohydrates can cause inflammation. Just because doctors find cholesterol inside artery-clogging plaques does not mean that cholesterol causes plaques. It is now well established that heart disease is a disease of inflammation. It is not simply that an innocent, smooth, buoyant sphere of fat and cholesterol traveling through the bloodstream decides to somehow randomly dig its way into a healthy coronary artery. The first step in the development of a vessel-clogging plaque is inflammation within the lining of the artery itself. When doctors cut into plaques they don’t just find cholesterol—they find many signs of inflammation (such as macrophages, calcium, and T cells). Wherever there is inflammation in the body, cholesterol is rushed to the scene to repair the damage—because we need cholesterol to build healthy new cells. Jumping to the conclusion that coronary artery plaques are caused by the cholesterol found inside of them is like assuming that all car accidents are caused by the ambulances that are found on the scene.

The latest research suggests that diets high in refined and high glycemic index carbohydrates increase the risk of inflammation throughout the body, especially in blood vessels. Diabetes, a disease which is intimately associated with high blood sugar levels, is infamous for causing damage to blood vessels in the retina, kidneys, and tiny vessels that feed nerve endings in the feet. It is well established that people with diabetes are also at higher risk for heart disease. It should therefore not be a stretch for us to imagine that all people with high blood sugar and/or insulin levels due to diets rich in refined carbohydrates may also be at increased risk for cardiovascular disease.

Cardiology researchers are now turning away from the notion that saturated fat and cholesterol cause heart disease. After all, how could saturated fat and cholesterol, which we have been eating for hundreds of thousands of years, be at the root of heart disease, which is a relatively new phenomenon? Cardiologists are finding instead that refined carbohydrate (such as sugar and flour), which we have only been eating in significant quantities for about a hundred years, is the single most important dietary risk factor for heart attacks:

“Strong evidence supports . . . associations of harmful factors, including intake of trans-fatty acids and foods with a high glycemic index or load.”

“Insufficient evidence of association is present for intake of . . . saturated and polyunsaturated fatty acids; total fat, . . . meat, eggs, and milk.” [Mente 2009].

Sweetheart?

There are several plausible mechanisms for how refined carbohydrate could increase risk for heart disease and change cholesterol profiles:

• Diets high in refined carbohydrate lower HDL levels and set the stage for high insulin levels, oxidation, and inflammation throughout the body, including in the coronary arteries.
• High blood sugar and insulin levels turn big, fluffy, innocent LDL particles into small, dense, oxidized LDL particles, which are associated with increased risk for heart disease.
• High insulin levels turn on the cholesterol building enzyme HMG-CoA reductase, forcing the body to make more cholesterol than it needs.

It is becoming increasingly obvious that cholesterol is innocent until corrupted by refined carbohydrate.

Poor cholesterol—so misunderstood. All animal cells require cholesterol for proper structure and function. The vast majority of cholesterol in the body does not come directly from foods like eggs and meat, but from the liver, which can make cholesterol out of anything we eat. So, if cholesterol-rich foods don’t cause high cholesterol, what does?

What is cholesterol?

Most people have no idea what cholesterol actually is.

Life without cholesterol would be impossible. Cell membranes, which wrap around and protect the inner contents of all cells, must contain cholesterol in order to function properly. Cholesterol contributes firmness to membranes and keeps them from falling apart. But wait, there’s more!

All of the following critical body components are made from cholesterol:

• Estrogen
• Testosterone
• Progesterone
• Cortisol (anti-inflammatory stress hormone)
• Aldosterone (regulates salt balance)
• Vitamin D
• Bile (required for fat and vitamin absorption)
• Brain synapses (neurotransmitter exchange)
• Myelin sheath (insulates nerve cells)

What is the difference between fat and cholesterol?

Cholesterol is made of carbon, hydrogen, and oxygen, just like fat is, but it is not fatty; it is a hard, waxy substance that contains no fat. A molecule of fat looks like this:

whereas a molecule of cholesterol looks like this:

As you may be able to appreciate just by looking at them, they are very different from each other.

Fat is a simple long chain, whereas cholesterol is mainly a complicated combination of rings—3 hexagons plus a pentagon; in medical school we affectionately called it “three rooms and a bath.” Fat is relatively easy to build (11 chemical steps from acetyl-coA to triacylglycerol), whereas cholesterol is hard to construct—more than 30 chemical steps are required to build one molecule of cholesterol (from acetyl-coA to cholesterol). The body would not go to the trouble of making it for no reason. Especially since, as it turns out, once it’s built, it’s impossible for the body to break it down—we do not have any way to take apart its complex ringed structure.

Cholesterol in foods

How much cholesterol do we need to eat?

None. Cholesterol is so important that the body can make cholesterol out of anything—fats, carbohydrates, or proteins. You don’t have to eat cholesterol to make cholesterol. Even if you eat a completely cholesterol-free diet, as vegans do, your body will still make cholesterol. Type “vegans with high cholesterol” into your search engine and you will find plenty of accounts of vegans whose cholesterol is too high—despite the fact that they eat ZERO grams of cholesterol.

Which foods contain cholesterol?

Since every single animal cell contains cholesterol, all animal foods contain cholesterol.

Many people don’t realize that all muscle meats (chicken, fish, beef, pork, etc.) contain about the same amount of cholesterol per serving.

Certain animal foods—liver, egg yolk, dairy fats, glandular organ meats, and brain— are especially high in cholesterol. Why is that? Liver is where the body manufactures cholesterol. Egg yolks contain concentrated cholesterol because the growing baby chick needs it to build new cells. Milk fat contains lots of cholesterol because the growing baby calf needs it to build new cells. Glandular organ meats (pancreas, kidney, etc.) contain more cholesterol because glands make hormones, and hormones are made from cholesterol. Brain contains very high amounts of cholesterol in its myelin sheaths, which insulate its electrical circuits.

All plant foods are considered “cholesterol-free.” Well, it would be more accurate to say that plant foods do not contain any animal cholesterol. Plants contain their own special forms of cholesterol called “phytosterols”, but phytosterols are toxic to human cells, so our intestines wisely refuse to absorb them.

So, in most cases, animal foods contain some cholesterol that the body can absorb and use, and all plant foods contain cholesterol that our body cannot absorb. The only exceptions I know of to these rules are shellfish.

There are two types of shellfish: crustaceans (lobsters, shrimp, crabs, etc.) and mollusks (clams, oysters, mussels, etc.). Crustaceans—giant sea insects who hunt for their food—contain animal cholesterols that can be absorbed by the body, but mollusks—who gather nutrients by filtering seawater—contain a different type of cholesterol that we can’t absorb.

In fact, plant cholesterols and mollusk cholesterols are not only rejected by our intestinal cells, they actually interfere with the absorption of animal cholesterols. This is how margarines such as Benecol® work. The manufacturer has added a chemically altered form of plant cholesterol to the spread, which interferes with the absorption of animal cholesterol.

Will eating cholesterol raise my cholesterol?

Yes, but only if your body needs more cholesterol.

The cells lining the small intestine each contain transporter molecules (NPC1L1) that absorb cholesterol. [The cholesterol-lowering drug Zetia® works by blocking NPC1L1 yet does not reduce risk of heart disease]. However, if the body doesn’t need any more cholesterol, there are other molecules (ABCG5/8 transporters) that pump the cholesterol right back out into the intestines to be eliminated from the body. This is one reason why it is virtually impossible for cholesterol from food to cause “high cholesterol.” The intestinal cells know exactly how much is needed and will not allow extra to be absorbed.

This is brilliant when you think about it (the body is so smart)—it is impossible for the body to break down the complex structure of the cholesterol molecule, so it would make no sense to absorb too much—once it’s inside the body there’s only one way to get rid of it, and that is to excrete it in the bile. Why take in more than necessary, if it’s just going to have to be eliminated?

However, if your body cholesterol levels are low, the intestinal cells will not kick it out, and it will make it into your bloodstream—because you need it.

What’s more, cholesterol is recycled very efficiently by our bodies, because it is so hard to make. Why make more from scratch if you don’t have to? Remember that it’s also impossible for the body to break down cholesterol, so the only way to get rid of it is to excrete it. The liver gets rid of any excess by excreting free cholesterol into the intestines along with bile. This free form of cholesterol is the only form that intestinal cells are able to absorb. Most of the cholesterol molecules in food (85 to 90% of them) are not free; they are in the form of “cholesterol esters.” [Cholesterol esters are just cholesterol molecules with a fatty acid attached]. Intestinal cells are incapable of absorbing cholesterol ester, which is the major form of cholesterol in food. Therefore, if the intestinal cells sense that the body needs more cholesterol, it will typically reabsorb most of what the body needs from the bile, not from food.

To summarize the relationship between food cholesterol and blood cholesterol:

1. Most cholesterol from food does not get absorbed unless body levels are low.
2. The amount of cholesterol you eat has almost no effect on your cholesterol levels.
3. The vast majority of cholesterol in your body is made by your body’s own cells. Remember that creepy line from the movie When a Stranger Calls? “The call is coming from inside the house.” The excess cholesterol is coming from inside your body, not from the food you eat.

How does the body make cholesterol?

All cells can make their own cholesterol, but liver cells are especially good at it. Only liver cells are capable of making more than they need for themselves—and shipping it out to other parts of the body.

Remember how it takes more than 30 chemical reactions to build one molecule of cholesterol? The most important of all of these steps is step #3. In this step, a critical enzyme called “HMG-CoA reductase” converts a molecule called HMG-CoA into another molecule called mevalonate. Once this step occurs, there’s no turning back, so it’s a big commitment. This reaction is the one that determines whether or not cholesterol gets made. Therefore, the enzyme that runs this reaction, HMG-CoA reductase, is very important—it’s like the foreman in charge of the cholesterol assembly line. This enzyme needs to be carefully controlled, because we don’t want cells wasting their time and energy building expensive cholesterol molecules willy-nilly.

The activity of this critical enzyme HMG-CoA reductase is controlled primarily by two things:

1. cholesterol levels inside the cell
2. insulin levels in the blood.

This is where things get really interesting. It makes sense that HMG-CoA reductase would respond to the cell’s cholesterol levels—if the cell’s levels are low, you want to turn that enzyme on, so you can make more cholesterol, and if the cell has enough cholesterol, you want to turn that enzyme off and stop making cholesterol. But what is insulin doing in the mix?

We think of insulin as a blood sugar regulator, but its real job is to be a growth hormone. Insulin is supposed to turn on when we need to grow. What do we need to make in order to grow? More cells. What do we need to form new cells? Cholesterol. So, at times when we need to grow (babies, teenagers, pregnant women), insulin turns the enzyme HMG-CoA reductase ON, which tells cells to make more cholesterol, so we can build new cells.

What causes high cholesterol?

Why would the body make more cholesterol than it needs?

Now here’s the problem: when people eat too many sugars and starches, especially refined and high glycemic index foods, blood insulin levels can spike. When insulin spikes, it turns on HMG–CoA reductase, which tells all of the body’s cells to make more cholesterol, even if they don’t need any more. This is probably the most important reason why some people have too much cholesterol in their bloodstream. Sugars and starches can raise insulin levels, which fools the body into thinking it should grow when it doesn’t need to. This is how low glycemic index diets and low-carbohydrate diets normalize cholesterol patterns—these diets reduce insulin levels, which in turn lower HMG-CoA reductase activity.

“Statin” drugs, such as Lipitor®, which are prescribed to lower cholesterol levels, work partly by interfering with the activity of HMG-CoA reductase. If your cells happen to need more cholesterol under certain circumstances, but the statin drug is blocking this critical enzyme, your cells may not be able to make cholesterol when needed. And what’s worse is that the cholesterol synthesis pathway doesn’t just make cholesterol; branches of this same pathway are responsible for synthesizing a wide variety of other important molecules, including: Vitamin A, Vitamin E, Vitamin K, and Coenzyme Q. So, you may want to think twice before you artificially interfere with this pathway by taking a statin drug.

When you eat less carbohydrate, you are not artificially blocking the pathway; you are simply allowing HMG-CoA reductase to listen to other more important signals (such as cholesterol levels and growth requirements) and decide naturally when it should turn on and when it should turn off.

So, to recap: refined carbohydrates speed up the cholesterol assembly line and statins slow it down. Which approach would you rather take to manage your “cholesterol problem”—taking a drug that artificially slows down this assembly line, or changing your diet so that the assembly line only runs when it’s supposed to? [Hint: Dietary changes require no monthly co-pays, and have no potentially dangerous side effects. I write about the dangerous brain side effects of statins in my Psychology Today post: “Low Brain Cholesterol—Separating Fact from Fiction.”]

Chances are: if you have “high cholesterol” you do not have a cholesterol problem—you have a carbohydrate problem.

Good cholesterol and bad cholesterol

This gets into the very complicated relationship between cholesterol blood tests and heart disease risk. This is an enormous topic, but I’ll summarize some basic points.

When you get your cholesterol levels checked, you will see numbers for HDL and LDL, as well as triglycerides. Triglycerides are fats, so we’ll set them aside and just focus on HDL and LDL.

HDL particles collect extra cholesterol from around the body and carry it back to the liver to be eliminated from the body if we don’t need it. It is typically thought of as “good cholesterol” so higher HDL levels are considered a good sign.

LDL particles carry extra cholesterol made in the liver out to the rest of the cells in the body. We used to think of LDL as “bad cholesterol” so lower levels of LDL were considered a good sign.

The cholesterol inside of HDL and LDL particles is exactly the same, it’s just that, for the most part, HDL is carrying it in one direction and LDL is carrying it in the opposite direction. The reason why LDL had been dubbed “bad” and HDL has been dubbed “good” is that numerous epidemiological studies (most famously, the Framingham Heart Study) told us that high LDL levels were associated with a higher risk of heart attack, and that high HDL levels were associated with a lower risk of heart attack.

We used to think that HDL was good because it acted like a garbage truck, clearing evil cholesterol out of our bodies, and we used to think that LDL was bad because it burrowed its way into our coronary arteries, depositing evil cholesterol there—forming plaques and causing heart attacks.

Cholesterol, carbohydrates and heart disease

However, this simplistic way of thinking about cholesterol and heart disease is changing before our very eyes. It turns out that it is more complicated than this. LDL, for example, exists in a variety of forms. It can be big and buoyant and “fluffy” or small and dense and oxidized (damaged). The new thinking is that small, dense, oxidized LDL may be the only type of LDL that is associated with heart disease. Therefore, instead of thinking of all LDL as “bad”, it would be more accurate to say that all LDL is not created equal—big fluffy LDL is “good” and small, dense, oxidized LDL is “bad.”

Unfortunately, standard blood tests can’t tell you which type of LDL you have because it lumps all types of LDL particles together. Standard tests can only estimate how much of your cholesterol is travelling inside of LDL particles. They can’t tell you how many LDL particles you have, how big they are, how dense they are, or how oxidized they are. [For a detailed explanation of the complexities involved in interpreting cholesterol blood test results, I recommend Dr. Peter Attia’s blog at www.eatingacademy.com.]

What we do know from research studies is that people who eat a diet high in refined carbohydrates tend to have a higher number of “bad” (smaller, denser, oxidized) LDL particles. This makes sense, because we know that carbohydrates are “pro-oxidants”—meaning they can cause oxidation.

There is also lots of evidence telling us that refined carbohydrates can cause inflammation. Just because doctors find cholesterol inside artery-clogging plaques does not mean that cholesterol causes plaques. It is now well established that heart disease is a disease of inflammation. It is not simply that an innocent, smooth, buoyant sphere of fat and cholesterol traveling through the bloodstream decides to somehow randomly dig its way into a healthy coronary artery. The first step in the development of a vessel-clogging plaque is inflammation within the lining of the artery itself. When doctors cut into plaques they don’t just find cholesterol—they find many signs of inflammation (such as macrophages, calcium, and T cells). Wherever there is inflammation in the body, cholesterol is rushed to the scene to repair the damage—because we need cholesterol to build healthy new cells. Jumping to the conclusion that coronary artery plaques are caused by the cholesterol found inside of them is like assuming that all car accidents are caused by the ambulances that are found on the scene.

The latest research suggests that diets high in refined and high glycemic index carbohydrates increase the risk of inflammation throughout the body, especially in blood vessels. Diabetes, a disease which is intimately associated with high blood sugar levels, is infamous for causing damage to blood vessels in the retina, kidneys, and tiny vessels that feed nerve endings in the feet. It is well established that people with diabetes are also at higher risk for heart disease. It should therefore not be a stretch for us to imagine that all people with high blood sugar and/or insulin levels due to diets rich in refined carbohydrates may also be at increased risk for cardiovascular disease.

Cardiology researchers are now turning away from the notion that saturated fat and cholesterol cause heart disease. After all, how could saturated fat and cholesterol, which we have been eating for hundreds of thousands of years, be at the root of heart disease, which is a relatively new phenomenon? Cardiologists are finding instead that refined carbohydrate (such as sugar and flour), which we have only been eating in significant quantities for about a hundred years, is the single most important dietary risk factor for heart attacks:

“Strong evidence supports . . . associations of harmful factors, including intake of trans-fatty acids and foods with a high glycemic index or load.”

“Insufficient evidence of association is present for intake of . . . saturated and polyunsaturated fatty acids; total fat, . . . meat, eggs, and milk.” [Mente 2009].

Sweetheart?

There are several plausible mechanisms for how refined carbohydrate could increase risk for heart disease and change cholesterol profiles:

• Diets high in refined carbohydrate lower HDL levels and set the stage for high insulin levels, oxidation, and inflammation throughout the body, including in the coronary arteries.
• High blood sugar and insulin levels turn big, fluffy, innocent LDL particles into small, dense, oxidized LDL particles, which are associated with increased risk for heart disease.
• High insulin levels turn on the cholesterol building enzyme HMG-CoA reductase, forcing the body to make more cholesterol than it needs.

It is becoming increasingly obvious that cholesterol is innocent until corrupted by refined carbohydrate.

Controversial carbohydrates! How can some carbohydrates—fruits, sweet potatoes, whole grains, and beans— be considered “good” and other carbohydrates—flour, sugar, and corn syrup—be considered “bad?” Doesn’t our brain need daily carbohydrate for energy? If so, how do people eating low-carb diets get by?

Let’s start with the basics . . .

What are carbohydrates?

Carbohydrates are sugars and starches. They are very simple molecules made out of carbon, hydrogen, and oxygen. All plants and animals can use carbohydrates for energy (and for building body parts and body chemicals).

What is the difference between sugars and starches?

“Sugars” are by definition very small. Glucose is a single-molecule sugar, or “monosaccharide.” Sucrose (table sugar) is a “disaccharide”, made of two molecules: one molecule of glucose plus one molecule of fructose (fruit sugar) linked together. Lactose (milk sugar) is also a disaccharide, made of one molecule of glucose plus one molecule of galactose linked together. These small sugars are sometimes referred to as “simple sugars.” Fruits are high in simple sugars.

“Starches” are big—they are made up of lots of simple sugars stuck together. Potato starch and corn starch are good examples. Starches are often referred to as “complex carbohydrates.” Most people are aware that grains, beans, nuts, seeds, and root vegetables are high in starches. However, animals also contain a small amount of starch that most people are less familiar with, called glycogen. This is a special starch designed especially for animals; plants do not contain any glycogen.

Storing sugar as starch

Humans store glycogen as an emergency source of carbohydrate. Glycogen is made of lots of glucose molecules linked together in short branches. If your blood sugar drops, or if you’re in an emergency situation and need fast energy, glycogen from the liver can be rapidly broken down into glucose and released immediately into the bloodstream.

The liver can only store somewhere between 250 and 400 calories worth of glycogen. (Glycogen is also stored in the muscles, but this glycogen is reserved exclusively for the muscles to use while exercising; it cannot be used to maintain blood sugar levels.) So, what does your liver do to make blood sugar if it runs out of glycogen between meals? It will turn to the protein in your muscles. The liver can turn muscle protein into glucose via a process called gluconeogenesis, which essentially means “making glucose from scratch.”

Why we store energy as fat

Starches are very dense and heavy. This is why we don’t store very much energy as glycogen—it would take up too much room and weigh too much. We store less than a day’s worth of energy as glycogen; the rest we store as fat.

Plants store their energy as starch, in thick, heavy roots and tubers and bulbs. That’s ok for them, because they don’t have to move, but imagine if we had to store all of our energy as starch—we’d have to carry around enormous lumps of carbohydrate—like gigantic potatoes growing underneath our skin—everywhere we went. And, if we overate and gained weight, the lumps would get so big and heavy that it would be impossible for us to move.

This is why animals like us, who need to move around, store energy as fat. Fat is much lighter and it is flexible, so it moves with us (ever try to bend a potato?). Plus, we can store lots and lots of it. There is a very low limit to the amount of glycogen we can store, but the amount of fat we can store is practically unlimited. (Just another clue that humans are designed to burn fat, not carbohydrate . . .)

Blood sugar regulation

All animals, including humans, have a simple sugar in their blood called glucose, which is also known as “blood sugar.” Glucose is used for fast energy by our cells. Because glucose is a monosaccharide (it exists as single molecules), it doesn’t have to be broken down—it is ready to burn.

It is critical that our blood sugar be kept in a very tight range for us to feel well and function properly. If blood sugar goes too high, we feel logey and foggy. Over long periods of time, high blood sugar (such as in untreated type 2 diabetes) can cause a variety of serious chronic health problems. However, if blood sugar drops too low, we are in immediate danger of serious consequences, such as seizure, coma, and death, because under normal circumstances, the brain requires some glucose to function.

Because tight blood sugar control is so important, we have a very sophisticated system for regulating it. If you eat a low-carbohydrate diet, your blood sugar levels tend to stay fairly even, but if you are like most people and eat carbohydrate throughout the day, your blood sugar will rise after you eat. It will rise even faster and higher if you eat refined or high glycemic index carbohydrates, such as sugar, flour, or fruit juice, because these types of carbohydrates are digested and absorbed very rapidly. How does the body manage these blood sugar surges?

How carbohydrates can make us fat

Let’s say you eat a popsicle. The simple sugars in the sweet popsicle are rapidly absorbed into your bloodstream, and your blood sugar quickly starts to rise. Since the body wants to harness that energy and prevent high blood sugar, your pancreas releases the hormone insulin into your bloodstream. Insulin lowers your blood sugar putting the body into sugar-burning, fat-storing mode. It literally turns off your body’s ability to burn fat so that excess sugar will be burned instead of fat. If your body has enough energy already and your cells don’t need to burn any more sugar, insulin tells the liver to turn the extra sugar into fat (lipogenesis), and then squirrels that fat away in your fat cells. That’s how sugar can make you fat.

Now, if you are not particularly carbohydrate sensitive, that may be the end of the story. You ate the popsicle, your blood sugar rose briefly, but insulin quickly took care of it, and now you’re fine. But what if you are carbohydrate sensitive? [To find out how carbohydrate-sensitive you are, take my free carbohydrate sensitivity quiz.]

Hypoglycemia and the invisible hormonal roller coaster

If you are carbohydrate sensitive (or have insulin resistance), you may have an exaggerated response to eating that popsicle. Not only does this mean that your blood sugar will rise more than usual, and stay higher for longer, it also means that your insulin level will rise more than usual, and stay higher for longer, causing your blood sugar to then drop too low or too fast. The body perceives this as a crisis, because it is very dangerous for blood sugar to drop too low.

So, there are other hormones that rush in to work against insulin and raise blood sugar. One of these is epinephrine, better known as adrenaline. Epinephrine raises your blood sugar by turning off insulin release and telling your liver to break down some of its emergency glycogen supply into glucose and release it into the bloodstream. Epinephrine is an ancient “fight or flight” hormone—it’s produced when we are in danger, such as when a saber-toothed tiger wanders into our cave. It is designed to give our bodies a surge of energy to help prepare us to fight or run away, but if we don’t use that energy to fight or flee, it just tends to make us feel panicky, shaky, agitated, and irritable.

The epinephrine reaction is responsible for most symptoms of “hypoglycemia”, which can occur within a couple of hours of eating sweet or starchy foods. Other hormones that are released to counteract insulin include glucagon (which may cause hunger sensations, headaches, and stomach upset), cortisol (our “stress hormone”), and growth hormone. These hormones work together to turn off your insulin response and return your blood sugar to normal.

For some people, this unstable pattern of rising and falling blood sugar is happening to some degree several times per day. Because most people eat refined and high glycemic index carbohydrates every day, they may not be aware that their daily cycles of moodiness, hunger, and physical discomfort are tied to this invisible hormonal roller coaster.

Why do carbohydrates make some people sleepy?

Many people feel sleepy after they eat or drink carbohydrates. It is not unusual to look around the dinner table and find people nodding off after dessert, or wanting to take a nap after a big starchy holiday meal. Why would that be if sugar carbohydrates are supposed to give us energy?

Relatively new research (conducted in mice) suggests that this effect may be due to a specialized group of brain cells called “orexin/hypocretin” neurons. These cells are responsible for alertness, and they appear to be turned on by proteins and turned off by carbohydrates.1

How much carbohydrate do we need to eat?

NONE.

Once we are weaned from breast milk, we can live a whole lifetime without eating a single molecule of carbohydrate:

“The lower limit of dietary carbohydrate compatible with life apparently is ZERO [my emphasis], provided that adequate amounts of protein and fat are consumed.”

“There are traditional populations that ingested a high fat, high protein diet containing only a minimal amount of carbohydrate for extended periods of time (Masai), and in some cases for a lifetime after infancy (Alaska and Greenland Natives, Inuits, and Pampas indigenous people). There was no apparent effect on health or longevity. Caucasians eating an essentially carbohydrate-free diet, resembling that of Greenland natives, for a year tolerated the diet quite well. However, a detailed modern comparison with populations ingesting the majority of food energy as carbohydrate has never been done.”

—Institute of Medicine and the Food and Nutrition Board 2005. Dietary Reference Intakes for Macronutrients. National Academics Press

Doesn’t the brain require glucose to function?

Well, yes . . . but:

1. The brain doesn’t need very much glucose. Depending on circumstances, the brain needs between 30 and 130 grams (1/8 cup to 1/2 cup) per 24 hours.
2. The brain can burn other fuels besides glucose—it can burn ketones (which are made from fat) and lactate (which is created by working muscles).
3. Your liver can make all the glucose your brain needs out of protein. This process is called “gluconeogenesis,” which means “making sugar from scratch.” You don’t have to eat sugar to make blood sugar.

How might carbohydrates cause common diseases?

There is growing interest in and scientific momentum behind what is called “the carbohydrate hypothesis of disease.” This is the idea that most diseases of civilization are caused by our so-called “Western” diet, and that the ingredient in the Western diet that is most dangerous is refined carbohydrate. The diseases on this list1 include:

• Type 2 diabetes
• Obesity
• Coronary artery disease
• Cancer of certain kinds
• Hypertension (high blood pressure)
• Alzheimer’s disease
• Peripheral vascular disease
• Osteoporosis
• Acne
• Diverticulitis
• Appendicitis

As a psychiatrist, I strongly suspect that the modern diet is a major culprit in many common mental health disorders, as well. I encourage you to read my blog posts about low-carbohydrate diets and bipolar disorder and the role of sugar in ADHD.

There have been numerous traditional human societies, which have eaten diets high in carbohydrate and have been healthy; however the types of carbohydrates in these diets were unrefined and tended to be low in glycemic index. Therefore, we will focus on the role of refined and high glycemic index carbohydrates in disease. For the sake of efficiency, let’s refer to them as “fast carbs.” I will be writing more about the potential dangers of fast carbs in the future, but for now, here are just a few important ways that they could raise our risk for serious diseases.

Advanced glycation end products (AGE’s)

Fast carbs raise blood sugar levels, and excess blood sugar can bind to vital proteins, DNA, RNA, and fats in the body and damage them, sometimes beyond repair. This process is called “glycation”. Think of it this way: sugars make proteins sticky. Proteins are supposed to be able to fold and move in special ways to perform their various special functions, but they can’t do that if sugar is gumming up the works. When sugars bind permanently to proteins, they turn the proteins into nuisance compounds called “Advanced Glycation End Products” or AGE’s. AGE’s have been linked to a wide variety of chronic diseases, including heart disease, kidney failure, diabetic retinopathy, Alzheimer’s disease, and aging.1

Carbohydrates and oxidative damage

Fast carbs are “pro-oxidants.” This means that they have the power to damage important body molecules, such as DNA, by stealing their electrons away from them. Pro-oxidants are the opposite of anti-oxidants; they fight against each other. In a healthy body, pro-oxidants and the antioxidants are in balance. However, most of us are out of balance, most likely due to our Western diet, which is very high in pro-oxidants, such as refined carbohydrates. We are told all the time that we need to eat foods high in antioxidants but we are never told that we are supposed to avoid foods that are high in pro-oxidants! Perhaps if we weren’t eating so many pro-oxidants, scientists wouldn’t think we needed to add anti-oxidants to our bodies. [Read my post on Psychology Today, “The Antioxidant Myth” to learn more about this.]

Oxidative damage caused by pro-oxidants such as sugars can be the first step towards serious problems, such as cancer (by damaging DNA) and heart disease (by oxidizing cholesterol).

Carbohydrates and inflammation

Both glycation and oxidation trigger inflammation in the body. Physicians and scientists have come to understand that most common chronic diseases are rooted in inflammation. This is not necessarily the kind of inflammation we can see or feel—it is usually on a much smaller scale that we may not be aware of. For example, the cholesterol plaques that block arteries to the heart and cause heart attacks are found to contain all the mini-markers of inflammation when you look at them under a microscope. Even diseases such as depression are associated with mini-markers of inflammation. [You can learn more about inflammation and mental illness in my Psychology Today post]

Bottom line about carbohydrates

It is completely unnecessary to eat any carbohydrate once you are old enough to eat solid food.

Rapidly digested carbohydrates such as sugar and flour have the potential to disrupt our hormonal rhythms, our appetite regulation mechanism, and our internal pro-oxidant/anti-oxidant balance. They put us at risk for chronic inflammatory diseases, mood instability, and obesity.

Because carbohydrates are completely unnecessary, it would be wise to consider substantially reducing the amount of carbohydrate in your diet, especially refined and high glycemic index carbohydrate.

Next steps

I’ve given you a lot of information about carbohydrates to digest guilt-free, but don’t want to leave you hanging. The following suggestions include both further reading and practical help to implement changes in your diet if you choose to reduce your carbohydrate intake.

I recently wrote a series about fructose and glucose metabolism and insulin resistance that further explores some of the information mentioned above.

• “Has Fructose Been Framed” takes a more detailed look at how the liver processes glucose and fructose.
• “Why Sugar Is Bad for You: A Summary of the Research” more closely examines how insulin resistance contributes to major chronic illnesses such as diabetes type 2, cancer, high cholesterol, heart disease, fatty liver disease, gout, and obesity.
• “How to Diagnose, Prevent, and Treat Insulin Resistance” provides valuable tips on how to determine if you are insulin resistant (including a downloadable pdf with medical tests that you can discuss with your health care provider), guidelines for how many carbs are safe to eat based on your health status, and an infographic with tips for increasing insulin sensitivity.
• I wrote an entire post about carbohydrates and the hormonal roller coaster for Psychology Today: “Stabilize Your Mood with Food.“

You may also want to take the carbohydrate sensitivity quiz to get a sense of your personal level of carb sensitivity and if you are considering trying a low-carb or ketogenic diet, my “Ketogenic Diet 101” post is full of practical tips and resources that you may find helpful.

If you have questions or stories about your personal journey, please share them in the comments section. And if you know others who would benefit from this information, please share this page on your favorite social media site. Hope to see you in the comments!

Controversial carbohydrates! How can some carbohydrates—fruits, sweet potatoes, whole grains, and beans— be considered “good” and other carbohydrates—flour, sugar, and corn syrup—be considered “bad?” Doesn’t our brain need daily carbohydrate for energy? If so, how do people eating low-carb diets get by?

Let’s start with the basics . . .

What are carbohydrates?

Carbohydrates are sugars and starches. They are very simple molecules made out of carbon, hydrogen, and oxygen. All plants and animals can use carbohydrates for energy (and for building body parts and body chemicals).

What is the difference between sugars and starches?

“Sugars” are by definition very small. Glucose is a single-molecule sugar, or “monosaccharide.” Sucrose (table sugar) is a “disaccharide”, made of two molecules: one molecule of glucose plus one molecule of fructose (fruit sugar) linked together. Lactose (milk sugar) is also a disaccharide, made of one molecule of glucose plus one molecule of galactose linked together. These small sugars are sometimes referred to as “simple sugars.” Fruits are high in simple sugars.

“Starches” are big—they are made up of lots of simple sugars stuck together. Potato starch and corn starch are good examples. Starches are often referred to as “complex carbohydrates.” Most people are aware that grains, beans, nuts, seeds, and root vegetables are high in starches. However, animals also contain a small amount of starch that most people are less familiar with, called glycogen. This is a special starch designed especially for animals; plants do not contain any glycogen.

Storing sugar as starch

Humans store glycogen as an emergency source of carbohydrate. Glycogen is made of lots of glucose molecules linked together in short branches. If your blood sugar drops, or if you’re in an emergency situation and need fast energy, glycogen from the liver can be rapidly broken down into glucose and released immediately into the bloodstream.

The liver can only store somewhere between 250 and 400 calories worth of glycogen. (Glycogen is also stored in the muscles, but this glycogen is reserved exclusively for the muscles to use while exercising; it cannot be used to maintain blood sugar levels.) So, what does your liver do to make blood sugar if it runs out of glycogen between meals? It will turn to the protein in your muscles. The liver can turn muscle protein into glucose via a process called gluconeogenesis, which essentially means “making glucose from scratch.”

Why we store energy as fat

Starches are very dense and heavy. This is why we don’t store very much energy as glycogen—it would take up too much room and weigh too much. We store less than a day’s worth of energy as glycogen; the rest we store as fat.

Plants store their energy as starch, in thick, heavy roots and tubers and bulbs. That’s ok for them, because they don’t have to move, but imagine if we had to store all of our energy as starch—we’d have to carry around enormous lumps of carbohydrate—like gigantic potatoes growing underneath our skin—everywhere we went. And, if we overate and gained weight, the lumps would get so big and heavy that it would be impossible for us to move.

This is why animals like us, who need to move around, store energy as fat. Fat is much lighter and it is flexible, so it moves with us (ever try to bend a potato?). Plus, we can store lots and lots of it. There is a very low limit to the amount of glycogen we can store, but the amount of fat we can store is practically unlimited. (Just another clue that humans are designed to burn fat, not carbohydrate . . .)

Blood sugar regulation

All animals, including humans, have a simple sugar in their blood called glucose, which is also known as “blood sugar.” Glucose is used for fast energy by our cells. Because glucose is a monosaccharide (it exists as single molecules), it doesn’t have to be broken down—it is ready to burn.

It is critical that our blood sugar be kept in a very tight range for us to feel well and function properly. If blood sugar goes too high, we feel logey and foggy. Over long periods of time, high blood sugar (such as in untreated type 2 diabetes) can cause a variety of serious chronic health problems. However, if blood sugar drops too low, we are in immediate danger of serious consequences, such as seizure, coma, and death, because under normal circumstances, the brain requires some glucose to function.

Because tight blood sugar control is so important, we have a very sophisticated system for regulating it. If you eat a low-carbohydrate diet, your blood sugar levels tend to stay fairly even, but if you are like most people and eat carbohydrate throughout the day, your blood sugar will rise after you eat. It will rise even faster and higher if you eat refined or high glycemic index carbohydrates, such as sugar, flour, or fruit juice, because these types of carbohydrates are digested and absorbed very rapidly. How does the body manage these blood sugar surges?

How carbohydrates can make us fat

Let’s say you eat a popsicle. The simple sugars in the sweet popsicle are rapidly absorbed into your bloodstream, and your blood sugar quickly starts to rise. Since the body wants to harness that energy and prevent high blood sugar, your pancreas releases the hormone insulin into your bloodstream. Insulin lowers your blood sugar putting the body into sugar-burning, fat-storing mode. It literally turns off your body’s ability to burn fat so that excess sugar will be burned instead of fat. If your body has enough energy already and your cells don’t need to burn any more sugar, insulin tells the liver to turn the extra sugar into fat (lipogenesis), and then squirrels that fat away in your fat cells. That’s how sugar can make you fat.

Now, if you are not particularly carbohydrate sensitive, that may be the end of the story. You ate the popsicle, your blood sugar rose briefly, but insulin quickly took care of it, and now you’re fine. But what if you are carbohydrate sensitive? [To find out how carbohydrate-sensitive you are, take my free carbohydrate sensitivity quiz.]

Hypoglycemia and the invisible hormonal roller coaster

If you are carbohydrate sensitive (or have insulin resistance), you may have an exaggerated response to eating that popsicle. Not only does this mean that your blood sugar will rise more than usual, and stay higher for longer, it also means that your insulin level will rise more than usual, and stay higher for longer, causing your blood sugar to then drop too low or too fast. The body perceives this as a crisis, because it is very dangerous for blood sugar to drop too low.

So, there are other hormones that rush in to work against insulin and raise blood sugar. One of these is epinephrine, better known as adrenaline. Epinephrine raises your blood sugar by turning off insulin release and telling your liver to break down some of its emergency glycogen supply into glucose and release it into the bloodstream. Epinephrine is an ancient “fight or flight” hormone—it’s produced when we are in danger, such as when a saber-toothed tiger wanders into our cave. It is designed to give our bodies a surge of energy to help prepare us to fight or run away, but if we don’t use that energy to fight or flee, it just tends to make us feel panicky, shaky, agitated, and irritable.

The epinephrine reaction is responsible for most symptoms of “hypoglycemia”, which can occur within a couple of hours of eating sweet or starchy foods. Other hormones that are released to counteract insulin include glucagon (which may cause hunger sensations, headaches, and stomach upset), cortisol (our “stress hormone”), and growth hormone. These hormones work together to turn off your insulin response and return your blood sugar to normal.

For some people, this unstable pattern of rising and falling blood sugar is happening to some degree several times per day. Because most people eat refined and high glycemic index carbohydrates every day, they may not be aware that their daily cycles of moodiness, hunger, and physical discomfort are tied to this invisible hormonal roller coaster.

Why do carbohydrates make some people sleepy?

Many people feel sleepy after they eat or drink carbohydrates. It is not unusual to look around the dinner table and find people nodding off after dessert, or wanting to take a nap after a big starchy holiday meal. Why would that be if sugar carbohydrates are supposed to give us energy?

Relatively new research (conducted in mice) suggests that this effect may be due to a specialized group of brain cells called “orexin/hypocretin” neurons. These cells are responsible for alertness, and they appear to be turned on by proteins and turned off by carbohydrates.1

How much carbohydrate do we need to eat?

NONE.

Once we are weaned from breast milk, we can live a whole lifetime without eating a single molecule of carbohydrate:

“The lower limit of dietary carbohydrate compatible with life apparently is ZERO [my emphasis], provided that adequate amounts of protein and fat are consumed.”

“There are traditional populations that ingested a high fat, high protein diet containing only a minimal amount of carbohydrate for extended periods of time (Masai), and in some cases for a lifetime after infancy (Alaska and Greenland Natives, Inuits, and Pampas indigenous people). There was no apparent effect on health or longevity. Caucasians eating an essentially carbohydrate-free diet, resembling that of Greenland natives, for a year tolerated the diet quite well. However, a detailed modern comparison with populations ingesting the majority of food energy as carbohydrate has never been done.”

—Institute of Medicine and the Food and Nutrition Board 2005. Dietary Reference Intakes for Macronutrients. National Academics Press

Doesn’t the brain require glucose to function?

Well, yes . . . but:

1. The brain doesn’t need very much glucose. Depending on circumstances, the brain needs between 30 and 130 grams (1/8 cup to 1/2 cup) per 24 hours.
2. The brain can burn other fuels besides glucose—it can burn ketones (which are made from fat) and lactate (which is created by working muscles).
3. Your liver can make all the glucose your brain needs out of protein. This process is called “gluconeogenesis,” which means “making sugar from scratch.” You don’t have to eat sugar to make blood sugar.

How might carbohydrates cause common diseases?

There is growing interest in and scientific momentum behind what is called “the carbohydrate hypothesis of disease.” This is the idea that most diseases of civilization are caused by our so-called “Western” diet, and that the ingredient in the Western diet that is most dangerous is refined carbohydrate. The diseases on this list1 include:

• Type 2 diabetes
• Obesity
• Coronary artery disease
• Cancer of certain kinds
• Hypertension (high blood pressure)
• Alzheimer’s disease
• Peripheral vascular disease
• Osteoporosis
• Acne
• Diverticulitis
• Appendicitis

As a psychiatrist, I strongly suspect that the modern diet is a major culprit in many common mental health disorders, as well. I encourage you to read my blog posts about low-carbohydrate diets and bipolar disorder and the role of sugar in ADHD.

There have been numerous traditional human societies, which have eaten diets high in carbohydrate and have been healthy; however the types of carbohydrates in these diets were unrefined and tended to be low in glycemic index. Therefore, we will focus on the role of refined and high glycemic index carbohydrates in disease. For the sake of efficiency, let’s refer to them as “fast carbs.” I will be writing more about the potential dangers of fast carbs in the future, but for now, here are just a few important ways that they could raise our risk for serious diseases.

Advanced glycation end products (AGE’s)

Fast carbs raise blood sugar levels, and excess blood sugar can bind to vital proteins, DNA, RNA, and fats in the body and damage them, sometimes beyond repair. This process is called “glycation”. Think of it this way: sugars make proteins sticky. Proteins are supposed to be able to fold and move in special ways to perform their various special functions, but they can’t do that if sugar is gumming up the works. When sugars bind permanently to proteins, they turn the proteins into nuisance compounds called “Advanced Glycation End Products” or AGE’s. AGE’s have been linked to a wide variety of chronic diseases, including heart disease, kidney failure, diabetic retinopathy, Alzheimer’s disease, and aging.1

Carbohydrates and oxidative damage

Fast carbs are “pro-oxidants.” This means that they have the power to damage important body molecules, such as DNA, by stealing their electrons away from them. Pro-oxidants are the opposite of anti-oxidants; they fight against each other. In a healthy body, pro-oxidants and the antioxidants are in balance. However, most of us are out of balance, most likely due to our Western diet, which is very high in pro-oxidants, such as refined carbohydrates. We are told all the time that we need to eat foods high in antioxidants but we are never told that we are supposed to avoid foods that are high in pro-oxidants! Perhaps if we weren’t eating so many pro-oxidants, scientists wouldn’t think we needed to add anti-oxidants to our bodies. [Read my post on Psychology Today, “The Antioxidant Myth” to learn more about this.]

Oxidative damage caused by pro-oxidants such as sugars can be the first step towards serious problems, such as cancer (by damaging DNA) and heart disease (by oxidizing cholesterol).

Carbohydrates and inflammation

Both glycation and oxidation trigger inflammation in the body. Physicians and scientists have come to understand that most common chronic diseases are rooted in inflammation. This is not necessarily the kind of inflammation we can see or feel—it is usually on a much smaller scale that we may not be aware of. For example, the cholesterol plaques that block arteries to the heart and cause heart attacks are found to contain all the mini-markers of inflammation when you look at them under a microscope. Even diseases such as depression are associated with mini-markers of inflammation. [You can learn more about inflammation and mental illness in my Psychology Today post]

Bottom line about carbohydrates

It is completely unnecessary to eat any carbohydrate once you are old enough to eat solid food.

Rapidly digested carbohydrates such as sugar and flour have the potential to disrupt our hormonal rhythms, our appetite regulation mechanism, and our internal pro-oxidant/anti-oxidant balance. They put us at risk for chronic inflammatory diseases, mood instability, and obesity.

Because carbohydrates are completely unnecessary, it would be wise to consider substantially reducing the amount of carbohydrate in your diet, especially refined and high glycemic index carbohydrate.

Next steps

I’ve given you a lot of information about carbohydrates to digest guilt-free, but don’t want to leave you hanging. The following suggestions include both further reading and practical help to implement changes in your diet if you choose to reduce your carbohydrate intake.

I recently wrote a series about fructose and glucose metabolism and insulin resistance that further explores some of the information mentioned above.

• “Has Fructose Been Framed” takes a more detailed look at how the liver processes glucose and fructose.
• “Why Sugar Is Bad for You: A Summary of the Research” more closely examines how insulin resistance contributes to major chronic illnesses such as diabetes type 2, cancer, high cholesterol, heart disease, fatty liver disease, gout, and obesity.
• “How to Diagnose, Prevent, and Treat Insulin Resistance” provides valuable tips on how to determine if you are insulin resistant (including a downloadable pdf with medical tests that you can discuss with your health care provider), guidelines for how many carbs are safe to eat based on your health status, and an infographic with tips for increasing insulin sensitivity.
• I wrote an entire post about carbohydrates and the hormonal roller coaster for Psychology Today: “Stabilize Your Mood with Food.“

You may also want to take the carbohydrate sensitivity quiz to get a sense of your personal level of carb sensitivity and if you are considering trying a low-carb or ketogenic diet, my “Ketogenic Diet 101” post is full of practical tips and resources that you may find helpful.

If you have questions or stories about your personal journey, please share them in the comments section. And if you know others who would benefit from this information, please share this page on your favorite social media site. Hope to see you in the comments!