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Tag: vitamin A

  • Taking Advantage of Sensory-Specific Satiety  | NutritionFacts.org

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    How can we use sensory-specific satiety to our advantage?

    When we eat the same foods over and over, we become habituated to them and end up liking them less. That’s why the “10th bite of chocolate, for example, is desired less than the first bite.” We have a built-in biological drive to keep changing up our foods so we’ll be more likely to hit all our nutritional requirements. The drive is so powerful that even “imagined consumption reduces actual consumption.” When study participants imagined again and again that they were eating cheese and were then given actual cheese, they ate less of it than those who repeatedly imagined eating that food fewer times, imagined eating a different food (such as candy), or did not imagine eating the food at all.

    Ironically, habituation may be one of the reasons fad “mono diets,” like the cabbage soup diet, the oatmeal diet, or meal replacement shakes, can actually result in better adherence and lower hunger ratings compared to less restrictive diets.

    In the landmark study “A Satiety Index of Common Foods,” in which dozens of foods were put to the test, boiled potatoes were found to be the most satiating food. Two hundred and forty calories of boiled potatoes were found to be more satisfying in terms of quelling hunger than the same number of calories of any other food tested. In fact, no other food even came close, as you can see below and at 1:14 in my video Exploiting Sensory-Specific Satiety for Weight Loss.

    No doubt the low calorie density of potatoes plays a role. In order to consume 240 calories, nearly one pound of potatoes must be eaten, compared to just a few cookies, and even more apples, grapes, and oranges must be consumed. Each fruit was about 40 percent less satiating than potatoes, though, as shown here and at 1:45 in my video. So, an all-potato diet would probably take the gold—the Yukon gold—for the most bland, monotonous, and satiating diet.

    A mono diet, where only one food is eaten, is the poster child for unsustainability—and thank goodness for that. Over time, they can lead to serious nutrient deficiencies, such as blindness from vitamin A deficiency in the case of white potatoes.

    The satiating power of potatoes can still be brought to bear, though. Boiled potatoes beat out rice and pasta in terms of a satiating side dish, cutting as many as about 200 calories of intake off a meal. Compared to boiled and mashed potatoes, fried french fries or even baked fries do not appear to have the same satiating impact.

    To exploit habituation for weight loss while maintaining nutrient abundance, we could limit the variety of unhealthy foods we eat while expanding the variety of healthy foods. In that way, we can simultaneously take advantage of the appetite-suppressing effects of monotony while diversifying our fruit and vegetable portfolio. Studies have shown that a greater variety of calorie-dense foods, like sweets and snacks, is associated with excess body fat, but a greater variety of vegetables appears protective. When presented with a greater variety of fruit, offered a greater variety of vegetables, or given a greater variety of vegetable seasonings, people may consume a greater quantity, crowding out less healthy options.

    The first 20 years of the official Dietary Guidelines for Americans recommended generally eating “a variety of foods.” In the new millennium, they started getting more precise, specifying a diversity of healthier foods, as seen below and at 3:30 in my video. 

    A pair of Harvard and New York University dietitians concluded in their paper “Dietary Variety: An Overlooked Strategy for Obesity and Chronic Disease Control”: “Choose and prepare a greater variety of plant-based foods,” recognizing that a greater variety of less healthy options could be counterproductive.

    So, how can we respond to industry attempts to lure us into temptation by turning our natural biological drives against us? Should we never eat really delicious food? No, but it may help to recognize the effects hyperpalatable foods can have on hijacking our appetites and undermining our body’s better judgment. We can also use some of those same primitive impulses to our advantage by minimizing our choices of the bad and diversifying our choices of the good. In How Not to Diet, I call this “Meatball Monotony and Veggie Variety.” Try picking out a new fruit or vegetable every time you shop.

    In my own family’s home, we always have a wide array of healthy snacks on hand to entice the finickiest of tastes. The contrasting collage of colors and shapes in fruit baskets and vegetable platters beat out boring bowls of a single fruit because they make you want to mix it up and try a little of each. And with different healthy dipping sauces, the possibilities are endless.

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    Michael Greger M.D. FACLM

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  • Is Moringa the Most Nutritious Food?  | NutritionFacts.org

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    Does the so-called miracle tree live up to the hype?

    Moringa (Moringa oleifera) is a plant commonly known as the “miracle” tree due to its purported healing powers across a spectrum of diseases. If “miracle” isn’t hyperbolic enough for you, “on the Internet,” it’s also known as “God’s Gift to Man.” Is moringa a miracle or just a mirage? “The enthusiasm for the health benefits of M. oleifera is in dire contrast with the scarcity of strong experimental and clinical evidence supporting them. Fortunately, the chasm is slowly being filled.” There has been a surge in scientific publications on moringa. In just the last ten years, the number of articles is closer to a thousand, as shown here and at 1:02 in my video The Benefits of Moringa: Is It the Most Nutritious Food?.

    What got my attention was the presence of glucosinolates, compounds that boost our liver’s detoxifying enzymes. I thought they were only found in cruciferous vegetables, such as cabbage, broccoli, kale, collards, and cauliflower. Still, it turns out they’re also present in the moringa family, with a potency comparable to broccoli. But rather than mail-ordering exotic moringa powder, why not just eat broccoli?Is there something special about moringa?

    “Moringa oleifera has been described as the most nutritious tree yet discovered,” but who eats trees? Moringa supposedly “contains higher amounts of elemental nutrients than most conventional vegetable sources,” such as featuring 10 times more vitamin A than carrots, 12 times more vitamin C than oranges, 17 times more calcium than milk, 15 times more potassium than bananas, 25 times more iron than spinach, and 9 times more protein than yogurt, as shown here and at 2:08 in my video. 
    Sounds impressive, but first of all, even if this were true, it is relevant for 100 grams of dry moringa leaf, which is about 14 tablespoons, almost a whole cup of leaf powder. Researchers have had trouble getting people to eat even 20 grams, so anything more would likely “result in excessively unpleasant taste, due to the bitterness of the leaves.”

    Secondly, the nutritional claims in these papers are “adapted from Fuglie,” which is evidently a lay publication. If you go to the nutrient database of the U.S. Department of Agriculture, and enter a more reasonable dose, such as the amount that might be in a smoothie, about a tablespoon, for instance, a serving of moringa powder has as much vitamin A as a quarter of one baby carrot and as much vitamin C as one one-hundredth of an orange. So, an orange has as much vitamin C as a hundred tablespoons of moringa. A serving of moringa powder has the calcium of half a cup of milk, the potassium of not fifteen bananas but a quarter of one banana, the iron of a quarter cup of spinach, and the protein of a third of a container of yogurt, as seen below and at 3:15 in my video. So, it may be nutritious, but not off the charts and certainly not what’s commonly touted. So, again, why not just eat broccoli?

    Moringa does seem to have anticancer activity—in a petri dish—against cell lines of breast cancer, lung cancer, skin cancer, and fibrosarcoma, while tending to leave normal cells relatively alone, but there haven’t been any clinical studies. What’s the point in finding out that “Moringa oleifera extract enhances sexual performance in stressed rats,” as one study was titled?

    Studies like “Effect of supplementation of drumstick (Moringa oleifera) and amaranth (Amaranthus tricolor) leaves powder on antioxidant profile and oxidative status among postmenopausal women” started to make things a little interesting. When researchers were testing the effects of a tablespoon of moringa leaf powder once a day for three months on antioxidant status, they saw a drop in oxidative stress, as one might expect from eating any healthy plant food. However, they also saw a drop in fasting blood sugars from prediabetic levels exceeding 100 to more normal levels. Now, that’s interesting. Should we start recommending a daily tablespoon of moringa powder to people with diabetes, or was it just a fluke? I’ll discuss the study “Moringa oleifera and glycemic [blood sugar] control: A review of the current evidence” next.

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    Michael Greger M.D. FACLM

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  • Vegans and Iodine Deficiency Risk  | NutritionFacts.org

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    Most plant-based milks are not fortified with iodine.

    “Adequate dietary iodine is required for normal thyroid function.” In fact, the two thyroid hormones are named after how many iodine atoms they contain: T3 and T4. “Given that iodine is extensively stored in the thyroid gland itself, it can safely be consumed intermittently,” so we don’t need to consume it every day. However, our overall diet does need a good source of it. Unfortunately, the common sources aren’t particularly health-promoting: iodized salt and dairy foods. (Iodine-based cleansers like betadine are used on cows “to sanitize the udders, resulting in leaching of iodine in the milk.”) Iodine may also be added to cattle feed, and some commercially produced breads contain food additives with iodine.

    If you put people on a paleo-type diet and cut out their dairy and table salt, they can develop an iodine deficiency, even though they double their intake of seafood, which can also be a source of iodine. What about those switching to diets centered around whole plant foods? They also cut down on ice cream and Wonder Bread, and if they aren’t eating anything from the sea, like seaweed or other sea vegetables, they can run into the same problem.

    A three-year-old’s parents reported striving to feed her only the healthiest foods, and her diet included only plant-based, unsalted, and unseasoned foods. She got no unprocessed foods, but she also got no vitamin supplementation, which could be deadly. Without vitamin B12, those on strictly plant-based diets can develop irreversible nerve damage, but in this case, a goiter arose first, due to inadequate iodine intake.

    In another case of “veganism as a cause of iodine-deficient hypothyroidism,” a toddler became ill after weaning. Before weaning, he was fine because his mother kept taking her prenatal vitamins, which fortunately contained iodine.

    Most vegetarians and vegans are apparently unaware of the importance of iodine intake during pregnancy, “for the neurodevelopment of the unborn child, similar to their omnivorous counterparts.” The American Thyroid Association and the American Academy of Pediatrics have recommended that women, even just planning on getting pregnant, should take a daily supplement containing 150 micrograms (mcg) of iodine, yet only 60 percent of prenatal vitamins marketed in the United States contain this essential mineral. So, despite the recommendations, about 40 percent of prenatal vitamins don’t contain it. “Therefore, it is extremely important that women, especially when pregnant, breastfeeding, or planning a pregnancy, read the labels of their multivitamin supplements to ensure that they are receiving an adequate amount of iodine.”

    Women of reproductive age have an average iodine level of 110 mcg/liter, which is fine for nonpregnant individuals, but we’d really like women to get at least 150 mcg/liter during pregnancy. (It’s basically a 24-hour urine test, in which iodine sufficiency is defined as 100 mcg/liter of urine in nonpregnant adults; the average vegan failed to reach this in the largest study done to date, one out of Boston.)

    The recommended average daily intake is 150 mcg per day for most people, which we can get in about a cup and a half of cow’s milk. Regrettably, plant-based milks aren’t typically fortified with iodine and average only about 3 mcg per cup. Although many plant-based milks are fortified with calcium, researchers found in the largest systematic study to date that only 3 out of 47 were fortified with iodine. Those that were fortified had as much as cow’s milk, but those that weren’t fell short, as you can see at 3:30 in my video Are Vegans at Risk for Iodine Deficiency?. 

    Plant-based milk companies brag about enriching their milks with calcium and often vitamins B12, D, and A, but only rarely are attempts made to match iodine content. The only reason cow’s milk has so much is that producers enrich the animals’ feed or it comes dripping off their udders. So, why don’t plant-milk companies add iodine, too? I was told by a food scientist at Silk that my carrageenan video played a role in the company switching to another thickener. Hopefully, Silk will see this video, too, and consider adding iodine, or maybe another company will snatch the opportunity for a market advantage.  

    The researchers conclude that individuals who consume plant-based milks not fortified with iodine may be at risk for iodine deficiency, unless they consume alternative dietary iodine sources, the healthiest of which are sea vegetables, which we’ll cover next.

    Doctor’s Note:

    This is the first in a four-video series on thyroid function. The next three are: 

    For more on iodine, see the related posts below.

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    Michael Greger M.D. FACLM

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  • The Future of GA Treatment

    The Future of GA Treatment

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    There’s new hope for people living with geographic atrophy (GA), an advanced form of the eye disease dry age-related macular degeneration (dry AMD). Scientists hope they’re close to new therapies for the condition that’s proven hard to treat in the past.

    In dry AMD, small yellow lesions called drusen form under your eye’s retina. If they grow larger, drusen can block nutrients from reaching the retina and cause cell death. Your eyesight becomes blurred, and if AMD advances to GA, you may have trouble seeing from the center part of your vision.

    There are two forms of AMD, wet and dry. Dry AMD affects around 90% of all people with AMD and usually gets worse more slowly. Although treatments for wet AMD have evolved quickly in the past few years, innovations in the dry form of the condition have come at a slower pace. 

    Michael Cooper, OD, an optometrist and director of medical education at Eyes on Eyecare, calls GA “a currently irreversible, visually devastating disease for millions of people.” 

    “We want to help people with GA take back some control and empower them by identifying GA earlier on, so they can live their life the way they want,” he says. And while vision loss from GA is permanent, future treatments may stop or slow the disease from getting worse over time. 

    Right now, the only treatments that might reduce the progression of dry AMD are vitamins and supplements. And once the illness advances to GA, there are no therapies – vision loss in these areas is permanent. Recently though, researchers have made exciting breakthroughs in pursuing treatments for GA, including medicines and surgery. 

    What Is the Role of the Complement System in GA?

    Many of the emerging treatments for GA work to control a part of your immune system called the complement system. These two systems team up to protect you from things that can make you sick such as viruses and bacteria. Your complement system enhances your immune system by switching on proteins that help keep you healthy.

    About 50 tiny proteins in your blood’s plasma make up your complement system. Normally, these proteins are idle until something triggers them, like when you’re injured or fighting off bacteria. This sets off a protective chain reaction called a cascade, where one protein switches on, followed by another and another.   

    Sometimes, proteins in your complement system work too hard, and your body triggers them too often. When this happens, it raises your chances of disease, including AMD, which can lead to GA.

    What Are Some Promising Treatments for GA?

    The most promising treatments for GA target the complement system. Cooper says researchers haven’t had a strong grasp of the science behind GA, but recently, the complement system “has become the marquee area of geographic atrophy research.”

    Researchers have homed in on two types of protein in your blood, the C3 and C5 proteins. Usually, these proteins get rid of germs that make you ill, but they can cause inflammation and also attack healthy cells.

    Researchers think C3 and C5 play a critical role in whether you’ll get AMD and eventually GA. They’ve been studying treatments that work to keep the complement system in check and slow the growth of GA lesions. While early clinical trials weren’t successful, recent studies have shown more potential.

    Complement Inhibitors

    One possible treatment is an eye injection called a complement inhibitor. It works by slowing C3 and the growth of GA lesions in people with dry AMD. A study of the therapy, named pegcetacoplan (Syfovre), found it can help slow lesion growth in those who have monthly shots and those who get shots every other month. 

    Based on the results of three studies, The FDA has fast-tracked the drug. The fast-track process speeds up the development and review of important new treatments so they can get to people sooner. The FDA considers whether the drug will fill an “unmet medical need,” meaning there’s currently no treatment for a specific medical condition, like geographic atrophy.

    Another complement inhibitor, called avacincaptad pegol (Zimura), slows GA from getting worse by targeting the C5 protein. One study found that people who took the drug, given as an eye injection, slowed GA by around 27% over 12 months. 

    In late 2022, the FDA named the treatment a breakthrough therapy. Like fast track, this process also speeds the development and review of certain drugs. A breakthrough therapy aims to treat a serious condition, and early evidence may show that the drug has an advantage over an available treatment. 

    Besides shots, researchers are also studying complement inhibitors in tablet form. These clinical trials are not as far along as the ones for treatments you take as a shot.

    Gene Therapy Surgery

    One possible downside of eye injections is that you may need them once a month or every 2 months for life. But researchers are looking at another option for GA that you would need just one time. 

    It’s a gene therapy designed to help the eye make a protein called complement factor I (CFI). CFI keeps complement in check, and boosting it with a one-time shot delivered beneath the retina can balance out an overactive complement system. 

    Cooper says gene therapy is the next wave of treatments for GA. “As time progresses, we get more sophisticated with our ability to formulate these medications, and I think we’ll see more of this type of delivery.” 

    Early study data found most people who had the treatment showed higher CFI levels. Some saw these results more than a year post-treatment. Researchers continue to study gene therapy for GA in ongoing clinical trials. 

    Modified Vitamin A

    Vitamin A is essential for vision but can turn toxic and form what scientists call “dimers.” Researchers have long thought that dimers play a role in whether you’ll get dry AMD. Now, they’re studying a chemically modified form of vitamin A that could ward off and treat dry AMD. 

    The drug, a capsule called ALK-001, replaces your body’s natural vitamin A with a version that slows the dimer-making process. Scientists are currently investigating how well the drug works to slow GA.   

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