The 3 Vitamins that Prevent Brain Loss

Image Credit: Thomas Hawk / Flickr. This image has been modified.

The 3 Vitamins that Prevent Brain Loss

By our seventies, one in five of us will suffer from cognitive impairment. Within five years, half of those cognitively impaired will progress to dementia and death. The earlier we can slow or stop this process, the better.

Although an effective treatment for Alzheimer’s disease is unavailable, interventions just to control risk factors could prevent millions of cases. An immense effort has been spent on identifying such risk factors for Alzheimer’s and developing treatments to reduce them.

In 1990, a small study of 22 Alzheimer’s patients reported high concentrations of homocysteine in their blood. The homocysteine story goes back to 1969 when a Harvard pathologist reported two cases of children, one dating back to 1933, whose brains had turned to mush. They both suffered from extremely rare genetic mutations that led to abnormally high levels of homocysteine in their bodies. Is it possible, he asked, that homocysteine could cause brain damage even in people without genetic defects?

Here we are in the 21st century, and homocysteine is considered “a strong, independent risk factor for the development of dementia and Alzheimer’s disease.” Having a blood level over 14 (µmol/L) may double our risk. In the Framingham Study, researchers estimate that as many as one in six Alzheimer’s cases may be attributable to elevated homocysteine in the blood, which is now thought to play a role in brain damage and cognitive and memory decline. Our body can detoxify homocysteine, though, using three vitamins: folate, vitamin B12, and vitamin B6. So why don’t we put them to the test? No matter how many studies find an association between high homocysteinea and cognitive decline, dementia, or Alzheimer’s disease, a cause-and-effect role can only be confirmed by interventional studies.

Initially, the results were disappointing. Vitamin supplementation did not seem to work, but the studies were tracking neuropsychological assessments, which are more subjective compared to structural neuroimaging—that is, actually seeing what’s happening to the brain. A double-blind randomized controlled trial found that homocysteine-lowering by B vitamins can slow the rate of accelerated brain atrophy in people with mild cognitive impairment. As we age, our brains slowly atrophy, but the shrinking is much accelerated in patients suffering from Alzheimer’s disease. An intermediate rate of shrinkage is found in people with mild cognitive impairment. The thinking is if we could slow the rate of brain loss, we may be able to slow the conversion to Alzheimer’s disease. Researchers tried giving people B vitamins for two years and found it markedly slowed the rate of brain shrinkage. The rate of atrophy in those with high homocysteine levels was cut in half. A simple, safe treatment can slow the accelerated rate of brain loss.

A follow-up study went further by demonstrating that B-vitamin treatment reduces, by as much as seven-fold, the brain atrophy in the regions specifically vulnerable to the Alzheimer’s disease process. You can see the amount of brain atrophy over a two-year period in the placebo group versus the B-vitamin group in my Preventing Brain Loss with B Vitamins? video.

The beneficial effect of B vitamins was confined to those with high homocysteine, indicating a relative deficiency in one of those three vitamins. Wouldn’t it be better to not become deficient in the first place? Most people get enough B12 and B6. The reason these folks were stuck at a homocysteine of 11 µmoles per liter is that they probably weren’t getting enough folate, which is found concentrated in beans and greens. Ninety-six percent of Americans don’t even make the minimum recommended amount of dark green leafy vegetables, which is the same pitiful number who don’t eat the minimum recommendation for beans.

If we put people on a healthy diet—a plant-based diet—we can drop their homocysteine levels by 20% in just one week, from around 11 mmoles per liter down to 9 mmoles per liter. The fact that they showed rapid and significant homocysteine lowering without any pills or supplements implies that multiple mechanisms may have been at work. The researchers suggest it may be because of the fiber. Every gram of daily fiber consumption may increase folate levels in the blood nearly 2%, perhaps by boosting vitamin production in the colon by all our friendly gut bacteria. It also could be from the decreased methionine intake.

Methionine is where homocysteine comes from. Homocysteine is a breakdown product of methionine, which comes mostly from animal protein. If we give someone bacon and eggs for breakfast and a steak for dinner, we can get spikes of homocysteine levels in the blood. Thus, decreased methionine intake on a plant-based diet may be another factor contributing to lower, safer homocysteine levels.

The irony is that those who eat plant-based diets long-term, not just at a health spa for a week, have terrible homocysteine levels. Meat-eaters are up at 11 µmoles per liter, but vegetarians at nearly 14 µmoles per liter and vegans at 16 µmoles per liter. Why? The vegetarians and vegans were getting more fiber and folate, but not enough vitamin B12. Most vegans were at risk for suffering from hyperhomocysteinaemia (too much homocysteine in the blood) because most vegans in the study were not supplementing with vitamin B12 or eating vitamin B12-fortified foods, which is critical for anyone eating a plant-based diet. If you take vegans and give them B12, their homocysteine levels can drop down below 5. Why not down to just 11? The reason meat-eaters were stuck up at 11 is presumably because they weren’t getting enough folate. Once vegans got enough B12, they could finally fully exploit the benefits of their plant-based diets and come out with the lowest levels of all.

This is very similar to the findings in my video Vitamin B12 Necessary for Arterial Health.

For more details on ensuring a regular reliable source of vitamin B12:

There are more benefits to lowering your methionine intake. Check out Methionine Restriction as a Life Extension Strategy and Starving Cancer with Methionine Restriction.

For more on brain health in general, see these videos:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

171 responses to “The 3 Vitamins that Prevent Brain Loss

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  1. Any evidence that B12 supplements can disturb the macrobiome? They seem
    to have done this to me.

    Dr. G, i have seen your B12 videos, but am wondering, are you sublingually taking it these
    days or are you simply swallowing it? With or without food? Thank you.

    1. <Dr. Greger, 27% of people suffer from 1298 and / or 677 HTMFR mutations. This means that they have difficulty metabolizing folic acid and need it in the ester form. Was this taken into account when these studies were done?

      1. Donald,
        I assume that you know that ‘Folic Acid’ is a man made synthetic form of folate.
        Folate and Folic Acid are not identical although they are used interchangeably
        by the supplement industry because Folic Acid is cheap and shelf stable. Most people have difficulty metabolizing Folic Acid into usable Folate form. Dr. Joel Fuhrman as written about this issue extensively.

    2. Heather I am curious about that too. I have read that B12 is best taken on an empty stomach but not everyone is in agreement on this (as usual!). Hope someone clarifies if they have substantive information.


    3. I am not aware and could not find any evidence of microbiome disruption.

      You can take B12 with or without food. Swallowing depends on the product.


  2. What is the source for your assertion that:”By our seventies, one in five of us will suffer from cognitive impairment. Within five years, half of those cognitively impaired will progress to dementia and death.”, as stated in the first paragraph of this article?

    1. From the statistics, it is shown that Alzheimer’s increases exponentially as we age, in particular after 80 or 90, I forgot, but it is an astronomical number like 1 in 3 or 1 in 2. And we are expected to live long with all this healthy eating.

    2. Eliz: The source documents are linked via the words in blue lettering within the article. In this case, you would click on “one in five” hyperlink to see the source.

      In the case of videos, Dr Greger provides a listing of sources under the sources heading beneath each video.

    3. Granting the statistics, this does not imply that significant brain shrinkage, cognitive impairment or dementia is a consequence of aging per se. Many people lead an unhealthy lifestyle, including poor diet, health-destroying habits, physical and mental inactivity.

      “Use it or lose it!” “Abuse it, you’ll lose it!”

      I’m a 70 y.o. WFPB vegan who lives by those mottos. It’s worked so far.

  3. Vitamin “fat” is one that you need for your brain.

    Besides the B vitamins, you also need vitamin D and vitamin A for your brain. Note that carrot and sweet potato contain Beta carotene that has to be converted to vitamin A, albeit very inefficiently, especially when you grow old or you have certain metabolism problem that prevents the conversion. Real Vitamin A only exists in animal foods, and I am talking from a nutritional and scientific point of view and not ethical.

      1. The real vitamin A is the retinol that does not need to be converted by the body. Plant foods contain Beta Carotene that has to be converted to retinol. Retinol is the useful form.

          1. Whenever there is a conversion in the body from a pre-form, you have 3 things that can happen, the inefficiency of the conversion and sometime inability to convert due to metabolism issue, did you eat enough of the pre-form to allow the conversion, and aging which slows down or stops the conversion.



            Of course I based my conclusion on scientific researches and not personal opinion.

        1. @Jerry Lewis

          In the United States, vitamin A deficiency is rarely an issue, so much so the newly proposed FDA Nutrition Facts label will not require the listing of vitamin A. Please don’t use vitamin A as a boogeyman to scare people into eating meat.

            1. Oops! posted the above link before noting that Vitamin A is being recognized as a very important player among the vitamins. The title of the article in the above link is “Vitamin A deficiency is detrimental to blood stem cells.”

              1. Lonie, now you know why we have to eat a certain amount of animal foods on top of WFPB. Note that carotenoid is not vitamin A and has to be converted by the body, albeit very inefficiently.

                  1. Lonie, I just replied to Liisa above. Vitamin A is not safe from supplement as I read. I think it’s because it cannot be produced in organic form, but only in synthetic form. The only vitamins that I supplement is Vitamin D and K, both in organic form. They are equally important as vitamin A and we cannot get enough through food. You can look up for those 2 vitamins from Dr Google. When I said vitamin K, I means MK2 and MK7 and not pure vitamin K that you find in kale that I eat plenty.

                    1. Lida, for vitamin D, I use the Garden of Life brand, For vitamin K2 (MK7) I use a brand by Life Extension but it is synthetic. So I look up on Amazon and find the following brand that has good reviews (I may switch to this brand myself):



                      P.S. If you ask me a question then make sure you reply to one of my post or otherwise I may not see it. Also ask several times if I don’t answer, simply because your post does not go to my mailbox for those reason, like this one. Despite people saying that I spread misinformation, I do try to help people and so if I don’t answer, it is simply because I don’t see the question.

            1. We should not jump to conclusions that supplements are where we should obtain our Vitamin A. Plants contain the phytonutrients that help the Vitamin A be used whereas pills generally contain isolated nutrients without the accompanying nutrients available in a WFPB diet. Unfortunately, the mice were fed a Vitamin A DEFICIENT diet. The article SPECIFICALLY MENTIONS carrots and broccoli as being good sources in the diet for Vitamin A. “This shows how vitally important it is to have a sufficient intake of vitamin A from a balanced diet,” Cabezas-Wallscheid emphasized. Studies have shown that isolated Vitamin A intakes can result in cancer. It is important to get Vitamin A from food; a WFPB diet is a great start, making sure to get high Vitamin A foods.

              1. We should not jump to conclusions that supplements are where we should obtain our Vitamin A. Plants contain the phytonutrients that help the Vitamin A be used whereas pills generally contain isolated nutrients without the accompanying nutrients available in a WFPB diet.

                Completely agree with what you are saying. On the other hand, one sometimes cannot, or will not, make the effort to craft our intake to accommodate a broad spectrum of necessary nutrients to act symbiotically.

                Supplementation is definitely a short cut, but assuming one knows enough to ensure the shortcut consists of nutrient symbiosis, it is a good work-around.

                I know I do not take anything in isolation, therefore the nutrient short cuts + food works well for me.

              2. Liisa, you got me wrong, I never advocated supplementation when it is available through foods. I eat plenty of WFPB, more than certain vegans. As for Vitamin A, I obtain it from eating cow liver. I know it is not vegan but you can look up for the nutrients packed in cow liver, especially vitamin A. That is the pure form of Vitamin A. Plant foods contains beta carotene that has to be converted to Vitamin A, albeit very inefficiently, especially as we age. Please look it up. So in summary, I eat WFPB + WFAB.

                P.S. your intuition would think that liver is the place where all the toxins in the body get deposited which is not true. Liver is only a kind of toxins processing plant. It retains nothing but just throws out the toxins through waste. Eating liver or organ meat in general; is not only nutritious but also ethical since you eat every parts of the animal that you eat out of necessity. Just remember when you eat plant foods, you also torture the bees and kill the insects.

                  1. I respect your opinion but I disagree with you. It’s a little bit complicated to explain and I don’t want to keep talking about meat on a vegan forum. But in a nutshell, meat eating cancer theory is overblown and it also depends on a great deal on which parts you eat.

                    1. The longest living groups in history only ate meat like once every few weeks. To say the theory is overblown is just following your tastebuds and eating what you have been used to. I would follow long term vegan body builders….not vegan body builders who turned vegan last week….not vegans who look anorexic and lifeless

  4. This article harkens me back to one of Dr. Greger’s early videos, probably in 2004 or 2005, in which he commented that vegetarians and vegans have all sorts of healthy biomarkers, but die just as young as omnivores, and the reason was B-12 and omega 3 deficiency. Great information and advice. Take it seriously.

  5. Wow, what great news that I can optimize the effect of my WFPBD with B12- I have been taking it all along and pass on the information to other vegetarians and vegans. Thanks Dr. Greger!

  6. Most posters here aren’t ready to hear it, but oils and fats are associated with healthy brain function. The most healthful are hemp and flax seed, and most nut oils.

    Get your torches and pitch-forks out, but coconut oil is also beneficial, and it can be used for cooking since it doesn’t convert to trans-fat when heated.

    Animal fat is to be avoided because it is converted into endo-toxin and contains animal hormones as well as pesticide from its feed.

    1. Why not just eat the seeds and nuts and get the whole package including the lignans? Dr. Fuhrman has been a consistent advocate for this approach to consuming healthy fats. These “slow” fats also include fiber that slows their absorption.

      1. I will look into Dr. Fuhrman’s work, thank you for the advice.

        Dr. David Perlmutter (Grain Brain et al) is also an advocate of consuming healthy oils and fats, but the topic seems to be forbidden on this site.

        Hey, do you know the difference between doctors and God?

        God doesn’t think he is a doctor!

      1. Coconut oil is the best phytolipid for cooking since it does not convert into trans-fat.

        If you don’t want to consume coconut oil, eat some lard then. Some people make the perfect the enemy of the practical.

        1. No studies proving such benefits of coconut oil have been posted here so far. Lard is ridiculous. I use broth for cooking, not believing that oil has any redeeming value. Oil is like sugar in that it provides calories and nothing else.

          1. Your comment that oil has no redeeming value is making an uninformed generality about oils.
            Some oils do have value. They are not sugars, nor do they act like sugars. The research of Dr. Johanna Budwig, for example, has proven that Omega 3 fatty acids (found in some plant oils, such as flaxseeds) are not only good for humans, but necessary. I would encourage folks who are interested in this topic to do some research about the studies done by Dr. Budwig.

            1. If the oil is found in flaxseeds, eat the seeds–not the oil. I eat flax SEEDS daily. Extracted oil from flax would miss all the fiber and subtle nutrients in the seed but extracted from the seed to make the oil.

    2. You can drink all the oils you want, but only essential fatty acids pass through the blood brain barrier. Everything is synthesized in the brain.

      1. Panchito – Neuroscientist here. . . . No, “everything is” NOT “synthesized in the brain.” Irresponsible posting on your part.
        thank you.

        1. Martha – you also get it in every vegetable. Green leafy vegetables have approximately 10% fat. And I’m just guessing but I would wager that it is just exactly the kind of fat that Mother Nature would like us to eat.
          Our next of kin, the chimpanzees, who eat mostly leaves, get all the protein, fat, carbohydrate they need from their natural diet. We don’t need to add fat other than what comes in natural foods like green leafy vegg, squash, broccoli, etc, . . and yes, avocados and nuts. But it’s not like we need to go out of our way to eat nuts “for fat” because other vegetables don’t have fat. Other vegetables have plenty of fat.
          Here is kale so you can see that it has 12% fat – 121 mgs of Omega 3 and 92mgs of Omega 6 fats.

          Here’s corn, 11% fat

          Here’s squash:
          3% fat, 40mgs Omega 3, . . .25mgs Omega 6

          No one who eats a WFPB diet needs to worry about whether or not they are getting enough fat. They are. Mother Nature built it in for us.

          1. That was a fascinating and SO helpful bit of information, Dear “Guest”. Thank you so much for bothering to explain it all! I try to share this kind of information with new or prospective vegans.

          2. There is a fallacy in your argument. You are looking at percent of calories. Health is based on the amount of a nutrient in the diet, both for healthful nutrients and for unhealthful nutrients. While kale indeed has 12% of its calories coming from healthy fats, kale has so few calories that the amount of these healthful fats is negligible, 0.5 gram. Another manifestation of this phenomenon is the unhealthiness of a pure fruit and vegetable diet. Even though some vegetables (spinach and broccoli) have a high percentage of calories coming from protein (fruit has very little protein), there are so few calories the actual amount of protein is well below what is needed.

            1. Steve Billings: Micheal Bluejay has a wonderful protein 101 article (here: ) where he addresses your point–among many others. Here is the answer applied to protein, but the same logic applies to fat:

              “Those who would object that we can’t eat enough lettuce to satisfy our protein needs are wildly missing the point. The point of using a day’s worth of calories for a single food is simply to show mathematically how the food measures up, not to suggest that anyone could or should eat only a single food. These plant foods are complete no matter how much or how little of them you eat. That is, if only 1% of your diet is lettuce, then lettuce supplies more than 1% of your protein and amino acid requirements.”

              The assumption is that people will eat enough calories to meet their needs – typically some combination of intact grains, beans, veggies and fruit (and maybe some nuts and seeds) for a healthy diet. But even a diet of pure fruit and veg (not something I’m recommending-I’m just making a point) would still meet X% of one’s fat and protein needs if one ate enough calories. (Don’t think it can be done? If you are interested, the following amusing video shows a small woman making it work: )

              The point of talking about the percent of nutrients in various plants is to show that if you eat enough calories, then you get enough of the nutrients. Using the example of the post from ‘Guest’: If you eat a variety of kale, corn, squash, *etc* until you meet your calorie needs, then you will have consumed a good percentage of your nutrients from fat–something that surprises a lot of people.

              To continue the game, intact grains have a fair amount of fat too and are more calorie-dense than the kale you pointed out. Quinoa, for example, has over 14% fat.

              It’s easy to see how one could fill up one’s belly over the day with plenty of calories from whole plant foods — AND have gotten a lot of fat, protein and (very importantly!) carbohydrates.

              1. Exactly, it’s the diet, not an individual food that is important. If one’s diet includes “adequate” amounts of all the vegan food groups: grains (typically 10 – 15% of calories from protein), nuts/seeds (typically 10 – 20% protein), legumes (typically 20 – 30% protein), vegetables (range between 5 and 50% protein) and fruit (negligible amounts of protein), a person is pretty much guaranteed to get adequate amounts of protein, and by the way, cumulatively adding up to complete proteins even though most individual foods will not have complete proteins. Fruits and vegetables alone will not do it. But all the food groups will do it easily.

                1. Stephen Billing: You wrote: “…most individual foods will not have complete proteins. Fruits and vegetables alone will not do it.”

                  I highly recommend that you take a look at that link I gave in the previous post. It uses solid data to dispute your claim, especially for vegetables. Here it is again:

      1. It’s true that the brain is composed of a large amount of fat, but that doesn’t mean that eating more fat will cause your brain to grow. Actually, a high fat diet causes the brain to shrink. This is well-known in the scientific literature. See this reference or this one.

          1. I have one – wrong! His and Davis’ ( ) have been debunked many times e.g.


            sports medicience and nutrition doctor:


            “We don’t have to look further than the most recent issue of the American Journal of Clinical Nutrition to find a paper contradicting Dr. Perlmutter’s claims. The study addresses the associations between The DASH diet and Mediterranean-style dietary patterns and age-related cognitive change in a prospective, population-based study. Higher levels of accordance with both the DASH and Mediterranean dietary patterns were associated with consistently higher levels of cognitive function in elderly men and women over an eleven year period. Whole grains and nuts and legumes were positively associated with higher cognitive functions.”



            Perlmutter misrepresents/misinterprets studies to support his wild claims. Recently I visited his website, where I found an article by him claiming carbs are bad, citing a Mayo Clinic research article. So I read the article. Sure enough the title of the article declared older people who ate more carbs had more cognitive problems than those who ate more fat. But near the end, the authors admitted the result could be because they included simple and processed carbs in with whole grains. They did not try to factor out the crucial difference. It is hardly new news that simple carbs are bad for one’s health and can be worse than saturated fat! Bottom line: the study did not actually show that whole grains are bad for health. In fact, many studies show the opposite. But no one promotes eating simple carbs, do they?

            It is hard for me to imagine Perlmutter was not aware of the critical limitation to the study. Unless he did not read the article, that is.

            1. David Johnson: You have SO many excellent and really helpful posts. I have a referred people to the article many times before. Your post here is a lot more comprehensive, and I really liked how you looked up some source research yourself. I’m sure I will be quoting you (with your name) in the future!

    3. To further punctuate what you are saying, this research suggests that a combination of dark chocolate and virgin olive oil can improve a cardiovascular risk profile.

      It is done by an Italian Dr and one would expect that she would have a friendly bias toward olive oil as Italy is one of the main producers of it, but still, if the evidence is there it should not be discounted due to origin.

      1. The above comment was supposed to be in answer to Rick Bergles’s statement: don’t know how it ended up way down here.

        Most posters here aren’t ready to hear it, but oils and fats are associated with healthy brain function. The most healthful are hemp and flax seed, and most nut oils.

  7. I’ve been tracking my nutrients with Cronometer, and I am getting methionine apparently from black beans. It’s not a lot, but it would be helpful if we could get a number we should be using as our upper limit. I doubt I’m getting anywhere near as much as I would get from meat, but a benchmark would help.

    1. I eat black beans (or red) every morning with my oats. I swear by those things. And I just placed 15th overall, out of 90 in a local 10K trail run. In my mid fifties. And that’s only the second 10K I’ve ever run in my life. They seem to be working. I make up a huge pot every few weeks and then freeze them. Put them in small containers and use them as needed. I save the pot liquor and use it in my other recipes.

        1. Nancy I am looking everywhere for that vegan chocolate cake recipe. When I find it I will post. Might be a year from now! I have to many cookbooks!!!

  8. What is the best way to get b-12? And if a supplement is the way what is a good brand of b-12 supplement and how much should I take?

      1. Hi Adam, do you know if regular garden variety peas are OK on Dr. Greger’s list of foods to eat?  I see that he only mentions English Peas.

  9. Dear Dr. Greger,

    I am an avid reader of this blog. Lot’s of great information that I have used to transform my life. That being said, this subject of hyperhomocysteinemia and related B6 and B12 supplementation is timely and important.

    Dr. McCully is still active as a researcher. For example, he conducted a small epidemiological study of vegetarians in Chad where he concluded: “The low dietary intake of protein and sulfur amino acids by a plant-eating population leads to subclinical protein malnutrition, explaining the origin of hyperhomocysteinemia and the increased vulnerability of these vegetarian subjects to cardiovascular diseases.”
    [Nutrition. 2012 Feb;28(2):148-53. doi: 10.1016/j.nut.2011.04.009. Epub 2011 Aug 27.]

    In short, his research associates homocysteine blood levels with the constellation of inflammatory diseases from arterial plaques to the ravages of Alzheimer’s disease. One of my mentors told me that the homocysteine research at Harvard was repressed at the time that the cholesterol hypothesis had gained ground and the drug industry was investing heavily in statin research. There appears to be fashion in medicine like in everything else.

    I have noted that a blood test for homocysteine is NOT part of the usual preventive medicine panels where I live, whereas, it is routine to test for cholesterol or even C-reactive protein. Yet, homocysteine appears to be a critical marker for inflammatory disease and is easily tested.

    Assuming folate is not an issue, I would be interested to know what level of B6 and B12 supplementation you would recommend to strict vegans, and if you get your homocysteine levels tested. Thank you for consideration of my questions.

  10. hi Arnold Freeman, here’s a link to a summary of Dr Greger’s recommendations . I keep it in my ‘favorites’ section for quick reference. Most of your questions about B12 will be answered there, but if you want to learn more, here is the B12 video collection that this site has put together .. Hope that helps!

  11. Not to divert attention away from the vitamin stuff, but let’s not forget ….. SMOKING. Most campaigns against sucking on butts focus on tar, nicotine, and cancers of all sorts. But there is one element of smoke that rarely gets the attention it needs and that is carbon monoxide (CO). Everyone (at least we hope everyone) knows CO kills. CO is present in all forms of incomplete combustion including cigarette or anything else you smoke. CO builds up in the blood and interrupts normal blood chemistry creating higher levels of homocysteine. And homocysteine as you know turns regular plaque into sticky plaque causing all kinds of cardio vascular problems including strokes.

  12. Where are the answers to these comment questions??
    Seems your org is missing the boat – in that many of these comments are useless to those of us who are here looking for answers to the very same queries.
    If there are answers in other resources you post, why not have your people respond by posting those links??

    1. Hi Dustywind,

      Thank you for your comment. I offer our apologies for not being able to respond to these queries more promptly, if at all. As you might imagine, we get hundreds of comments each day among the 1000+ videos we have, often including complicated medical and nutrition questions that take can take lots of time and effort to address adequately. While we do have a small (but mighty!) Volunteer Moderator Team made up of medical professionals who offer their precious time and resources to help address many of these questions and comments, we currently and unfortunately do not have the resources to adequately respond to the majority of them.

      As you may know, Dr. Greger is currently knee-deep in research for upcoming videos to keep the site going, and while he is able to occasionally pop in and respond to questions here and there, he also doesn’t have an abundance of time to dedicate to most of the questions that come in either. This is also partly where the monthly Q&As he does comes in, but, of course, he is not able to address all the questions that come in during that short period of time either.

      I hope we can do a better job about addressing these important questions and hope you can stick with us in the meantime.

      Thank you.

    1. Dustywind – what I have noticed is that, over time, the team synthesizes many of our questions and seeks to put together a video that addresses the issue. It may not address your particular question, particularly if there is insufficient research to answer it. We are capable of asking more questions than research entities have time and research money to answer. This is not a site where we get to demand answers to our specific questions. For that I would like to suggest that you pay your personal physician for a discussion on the matter. Perhaps s/he or a paid Nutritionist will be willing to give the premier service that some would enjoy.

  13. Am I reading this wrong? Vegetarians and Vegans have HIGHER homocysteine levels and homocysteine is BAD…..folate and B12 supplements bring it down to 5. So what happens if omnivore take B12 and folate, what happens to their levels. I am 99.99 % vegan and advocate such to my patients, but I have to be able to answer their questions.

  14. Does anyone know if there has been any follow-up studies to the Spanish publication that found fungi in th brains of A D patients ?

  15. If we agree that all nutrients are available from our food (or should be) a red flag should be raised for vegans. If one has to supplement with B12 to balance homocysteine ,logically this says that humans need some animal products to provide B12. Vegans had homocysteine levels of 16 micromoles/L. Terrible.My diet consists of many different plant foods ,nuts but some meat.

    1. Only a truly ignorant vegan would not realize B12 needs to be supplemented. Omnivores can also be B12 deficient, so your eating “some meat” does not necessarily put you in the clear. Vitamin D is similar – expose yourself to sufficient UV if possible or take a supplement. Ditto, DHA/EPA and fish-eating. Unfortunately, we live in an imperfect world so, ethical issues aside, you have to weigh the potential health benefits and risks. Being pedantic about getting absolutely everything from food is not rational in our highly polluted world.

      1. Food is a very poor source of vitamin D so absolutely we need sensible sun exposure. That’s what nature intended. UVB exposure on the skin synthesises vitamin D. B12 is available from food. 40-80% of vegetarians may be B12 deficient. 80% in vegans. I also supplement with vitamin D3 in winter as at my latitude UVB is very low.

      2. David E. Johnson – you are correct. I had to give my Father 6 weeks of B-12 shots into his muscle for his B-12 deficiency. And he was a big meat eater all of his life. Nursing homes know to test for B-12 deficiency in the elderly and it has nothing to do if they eat meat or not. Anyone can have a deficiency.

        1. Dr. Greger and Dr. Fuhrman recommend and low dose algae-based supplements. I happen to take Ovega 3 (higher does) but my wife takes Dr. Fuhrman’s (more expensive, lower dose but no unwanted added ingredients).

          Check out Dr. Greger’s supplement recommendations.

    2. B12 supplementation should be enough and would be the ethical way. If not meat every few weeks should be good and just get the GP to monitor it in your blood. The real red flag would be the industrialisation of our water…back in the old days b12 vitamin was in our water

  16. I eat my beans religiously and loving them! :P Also lentils and spinach. All really good and tasty stuff. B12 is a bit tricky to get but I hope B12 pills will do.

  17. Hi, I was wondering if Dr. Greger or his team had any advice on helping raise awareness and funding for alzheimers research and prevention. I have been following videos for years and have been particularly interested in alzheimers prevention due to a history of it in my family. I could not have been more shocked by the poor memory and decision making on a fly in fishing trip by a family member last year. The end result was a horrible accident resulting in his death after drowning rescuing me from the float plane he crashed.

    1. There is a doctor that has done talks (same as Dr Greger) in Hawaii, at the VSH (Vegetarian Society of Hawaii). They bring a new MD or PhD out to the islands once a month for a massive talk/conference, often several days on Oahu, and then they will usually do their talk on Maui, too. The Doc who I saw some years ago there talking about Alzheimers prevention is Steve Blake ScD, and you can also watch this which was featured there. “Published on Oct 18, 2011

      A presentation by Steve Blake, Sc.D..
      Alzheimer’s disease is the 6th leading cause of death in the United States. Care for its victims costs more than the expense of heart disease and cancer combined. This class and slide show is based on the latest scientific research from leading journals worldwide. Find out which two nutrients are crucial for lowering the buildup of amyloid plaques. You will learn how to lower your risk by increasing your intake of antioxidant fruits, vegetables, and seeds. Lowering saturated fats in the diet can result in better blood flow to the brain. See studies that show which supplements and medical plants have been shown to be effective in reducing the risk and progression of this common dementia. Dr. Blake has just returned from presenting this information about Alzheimer’s disease to teaching hospitals on the East Coast.
      Steve Blake has a doctorate in holistic health and a doctorate in naturopathic medicine. His area of interest is nutritional biochemistry. He offers classes at the University of Hawaii VITEC program. Dr. Blake is the author of the 2008 McGraw Hill college textbook Vitamins and Minerals Demystified. He has just completed writing Understanding Dietary Fats and Oils: A Scientific Guide to their Health Effects. He is also the author of Healing Medicine. He has a huge database on medicinal plant use around the world. Dr. Blake programmed the Diet Doctor 2011, software for graphing dietary nutrients. He is often heard on radio and seen on television
      Filming and editing by Dr William Harris M.D. on October 15, 2011 at McCoy Pavilion, Ala Moana Beach Park, Honolulu, Hawaii
      Sponsored by: Vegetarian Society of Hawaii

  18. Question: Do you have a chart that is longer than a week for the B12?
    This is my concern–the delta for the statitisric is equal to the reduction in homocysteine. That means it is not provable with the data shown.
    I love your work, but am trying to convince a doubting spouse.

    1. Hi Susan, as a veteran of Dr. Greger’s website and blog, do you recall if he ever addressed the need for a greater dose of B12 for those over 65 and/or with digestive issues?

  19. So I am confused about methionine
    It is bad for cancer so reducing it good if you have cancer, but found in beans so to eat good plant diet need beans.

      1. Thank you Susan, that did answer my question.
        But a further concern, Dr Gregor says to avoid eggs, both for prostate cancer and other cancers. Much of the reason for avoiding eggs has to do with the yolk, are egg whites ok, if trying to stave off cancer growth?

          1. Thank you, answers my question. Just gets hard to figure out what to eat.
            We were avoiding eggs for prostate cancer, but thought it was mainly because choline in the egg yolk.

            1. Mary: On the topic of figuring out what to eat: If you have some questions or can give us a hint at what the trouble is, there are a lot of folks here with some really great ideas. Are you having trouble with breakfast ideas? Knowing what to do about quiche? or pancakes? Worried about getting enough protein? Need convenient breakfast food? Looking for a particular taste and texture?

              Of course, you don’t have to reply. I just thought I would see if there was a way we could help you. As for the egg answer, sorry to disappoint. I know that for some people, giving up eggs is very, very hard. Good luck.

                1. Lida: Great question. I’ve tasted some truly fabulous salad dressings that just happened to be oil-free. Dr. Greger has one in his book, How Not To Die, page 319. Other vegan cookbooks have good ideas also. There are also lots of free options on-line. I’m sure you would be able to find some that you like:

                  Healthy Girl’s Kitchen Big List of No-Oil Salad Dressings
                  > Volume 1:
                  > Volume 2:

                  > Fat Free Vegan, Buttermilk Dressing:
                  > 10 Simple Recipes:
                  > Magical Recipe:

                  I’d be surprised if you didn’t find something in all those recipes that appealed to you. Please report back and let us know how it goes. I hope this helps.

    1. I’ve seen the same research and while I take a complete B-vitamin daily, I don’t plan to stop. Reason is, I also take milk thistle which contains silibinin purported to stop cancer from spreading. The link is here.

      Didn’t re-read my link so not sure if it is where I read to also take curcumin and vitamin C with the milk thistle since those two additions assist the milk thistle in working and makes a little go a long way.

      Oh, personally I take turmeric with piperine added instead of straight curcumin. I also take turmeric throughout the day in other forms such as liquid drops, so I should be getting sufficient amounts to go along with the milk thistle, which I also take in liquid form in my tea, at times.

      1. I just heard a lecture today that bioperine (black pepper) is bad for you. What is piperine? I wonder if it is also some form of black pepper.

        1. Hi Robyn,

          Indeed Piperine is an extract of black pepper. I personally punch a hole in the end of a capsule and with a gentle squeeze, it puffs out some of the white powder onto whatever food I want it on.

          My instinct tells me you can discount the lecturer who says black pepper is bad for you. Years ago I read that we shouldn’t eat black pepper because it will cause appendicitis. Caused me to forgo black pepper for years.

          On the other hand, I still do not eat the coarser ground black pepper as an add-on… just in case. I do however, use it generously in cooking as it seems to soften when used this way.

          I started buying and using the bioperine because it is so finely textured. And, I know it is pepper like as just a hint of it in the air causes a throat cough.

          The thing is, it is worth the effort to use as it has been touted to make other nutrients more absorbable. On occasion I will take one of the capsules but I have learned to insure I have taken food or drink beforehand or with it, because taking it alone has resulted in some fire in the belly.

        2. After posting in answer to your question about black pepper, I was puzzled that someone could say black pepper is bad… UNLESS the lecturer was into hip hop where bad is good.

          Like “You bad girl, you bad.” Which of course means “You’re hot!” Which would also describe black pepper as it is also hot.

          This is the only way I can see that a lecturer would call black pepper bad. ‘-)

    2. Interestingly, the results were gender specific: “Use of supplemental vitamins B6, folate, and B12 was not associated with lung cancer risk among women. In contrast, use of vitamin B6 and B12 from individual supplement sources, but not from multivitamins, was associated with a 30% to 40% increase in lung cancer risk among men. ”

      Most worrisome to me since I do not supplement B6 but do B12 is that the B12 dose cutoff point was not actually very high ( > 55 µg/d) compared to what is often recommended, including by Dr. Greger:

      “Vitamin B12 (see also Which type of vitamin B12 is best)

      At least 2,500 mcg (µg) cyanocobalamin once each week, ideally as a chewable, sublingual, or liquid supplement taken on an empty stomach
      or at least 250 mcg daily of supplemental cyanocobalamin (you needn’t worry about taking too much)
      or servings of B12-fortified foods three times a day, each containing at least 25% U.S. “Daily Value” on its label
      Those over 65 years of age should take at least 1,000 mcg (µg) cyanocobalamin every day.”

      On a different note, I’d like to point out that it is possible to have too high a B12 blood serum level from supplementation. I was taking 1000 mcg/d cyanocobalamin , recommended for those over 65 (I’m 70), and also 300 mcg methylcobalamin from a vegan multi (Dr. Fuhrman). My lab test result was so high (over 100 pg/mL00) I did not get a specific number. After dropping the multi (for other reasons) and cutting back to 500 mcg per day, after 3 months my results dropped to 992, still to high as the reference range is 200-931.

      Based on my experience, it’s my opinion that everyone supplementing with relatively high amounts of B12 should have their blood levels checked.

  20. I have eaten a largely (local, organic) plant based diet for decades. I have also supplemented with B12 and folate for decades. So when I had a comprehensive panel drawn (Boston Heart Labs) I was surprised that my homocysteine level was elevated. As it turns out, I am heterozygous for the MTHFR gene mutation. As such, I do not methylate my folate or B12 and so I am less able to metabolize homocysteine properly. Here are the two important take homes:

    1) the gene mutation is NOT rare, with a carrier frequency of 31% to 39% (homozygote frequency 9%-17%) :

    Heterozygous Mutation: This is the most common and less severe of all the mutations. It means you have 1 normal gene and 1 mutated gene. The mutation will either be on the 677 or the 1298 position. The MTHFR enzyme will run at about 55-70% efficiency compared to normal MTHFR enzymes.

    Homozygous Mutation: This means you have 2 affected genes on either the 677 or the 1298 position. In this case, your MTHFR enzyme will only run at about 7-10% efficiency.

    2) if you take methyl folate and methyl B12 you can compensate for your enzymatic deficiency.

    Info from Mayo Clinic and Fresh Idea Mama websites

  21. Dr Gregor,

    My understanding is Vitamin B12 is a bacteria that comes from the ground and animals intake B12 into their systems as they graze. Most animals raised for food are not allowed to graze any longer and are fed soy and corn, etc., so how are they getting B12? How come meat eaters do not have the deficiencies seen in not meat eaters have since most animals come from factory farms?

    1. I know it is a bacteria that cows usually get by eating grass through the soil. Since animals in farms are no longer grazing where are the getting this bacteria from?

      1. They ingest plenty of bacteria from their environments, some of which would contain B12 producing types. Once ingested bacteria lives comfortably in their stomach. Cf.

        Also as pointed out in a different answer, they are given B12 in their feed because the antibiotics they get kills the B12.

  22. I have a brother who used to get B-12 shots every month or so… seemed to give him an energy boost.

    Anyone have experience of getting the vitamin this way?

    1. Lonie – I gave my Father B-12 shots for 6 weeks straight for his deficiency. It is extremely common for elders and some others to have a natural deficiency. This is just exactly why we get blood tests – so that we can find out before damage is done. My Father ate meat all his life and was never vegan. It is common to find B-12 deficiencies in the elderly and in Nursing homes.

      I’m WFPB vegan. I’m taking my B12.

      1. May I ask what form do you take: methycobalamin or Cyanocobalamin, and do you take it in capsules, liquid, sub-lingual tablet, etc. ? I take B-12 methylcobalamin dry powder in capsules, 2,000 mcg a day. (Need to get tested to see if this is doing the job, however!)

          1. Yes, I know, Mary. With all due respect – and I “did” read everything, including Dr. Greger’s transcript, it was not really clear about which kind of B-12 to use and in what form. Or the dosage per day or per week. And, if you get a shot, does it have to be intramuscular? I had one and I think it was but didn’t even feel it. So, I have a lot of questions. I have also seen, elsewhere, advice that methylcolbalamin is “superior” to the cynocolbalamin. I think that people really need to get these questions answered a bit more completely or with more clarification and advice. At least, I do! :) And, by the way, I am neither a scientist or a medical professional.

  23. Renate,

    If Dr. Greger’s comments plus the many who have posted with links do not meet your requirements for educated comments, I fear you are at the wrong forum.

  24. Dr. Greger, I am a vegan eating a plant-based diet for three years. My doctor recently found me to have a defect of the MTHFR gene, in which my homocysteine is high and I don’t metabolize B vitamins correctly. She is treating this with a supplement but the homocysteine is not coming down. I have not eaten meat in ten years. Any thoughts? Thank you, and see you in Norway. ;-)

    Judi Duncan

    1. Hi Judi,

      I am a volunteer for Dr. Greger. Thank you so much for your question.

      I am sorry to hear about your genetic defect. However, sufficient supplementation with the B vitamins (and usually choline) usually helps. You can also be sure to get adequate folate from the diet by increasing your intake of beans, lentils, and greens.

      And as always, be sure to be in good communication with your doctor, as he/she should lead you in the right direction to get this sorted out.

      1. Thank you for validating what my doctor says. She has chosen a supplement that does provide the bioavailability, but after six months the homocysteine has not come down. Hopefully it still will. I do eat a lot if all the recommended plant foods.

        Judi Duncan

  25. I just saw this article this past week from the Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute about some research that lung cancer seems to be more prevalent in people taking very high doses of B-2 and B-12 supplements over a long term for men who smoked. The doses were well above the recommended daily amount and were taken for 10 or more years.

    It does suggest that we should be careful about over dosing on supplements.

    1. Hey Chelsea, thanks for writing! Dr. G’s focus is on whole foods, plant-based diets and the prevention and treatment of chronic disease, not cannabinoids or their derivatives, which are in the province of pharmacology and herbal medicine.

  26. I am curious about the dosage of Vitamin B12 after reading that too much may cause cancer in menHere is an excerpt from the article :”The research team is quick to note that the doses of B vitamins in question are enormous. The U.S. Recommended Dietary Allowance …. for B12 it’s 2.4 micrograms. The high-risk group in the study was taking around 20 times these amounts.”

    The source is

    So what is the correct dosage for B12?

    1. Bobbie, I am certain that I recall Dr. Greger recommending 2500 mcg per week.  If over 65 he suggested 1000 mcg per day.  You can go to the site and search B-12 and you will find this information there.  As for the type he suggests cyanocobalamin as chewable or sublingual or swallowed.

    1. Dr. Greger has several comments about B-12 and in one he does mention taking 2500 mcg per week and suggesting 1000 mcg per day for those over 65….I do not have the computer skills to copy and paste that to this post but maybe you could do a more thorough search because your information is somewhat incomplete.  He also recommends the cyanocobalamin  form

  27. This article from August 2017 in The Atlantic discusses B6 and B12 in high doses being implicated in increasing lung cancer risk
    I would be grateful if Dr. Greger would comment on this study. I’m particularly concerned because my husband and I are vegans, and he is over 65. I also have a history of certain cancers in my family, and high doses of B12 have also been linked to prostate cancer. We own copies of “How Not To Die” and regularly review Dr. Geger’s videos and articles, so his guidance on this issue would be appreciated. Thank you.

  28. Rachel S,

    Do you have a reference for “high doses of B12 have been linked to prostate cancer”? Prostate cancer is a concern of mine and my B12 level is quite high from supplementation.

  29. Im a 6 year vegan and have recently found out my homocysteine levels were high, 13. I have been taking methylcobalamin 220mcg daily via Dr. Furhman’s women’s daily since I became vegan. I’m perplexed and don’t know how to resolve this and my doc just tells me not to be concerned. I’m concerned! Help! Any suggestions?

  30. Keep in mind that many vegan foods such as french fries and soda do not support health, which is why Dr. G does not recommend veganism. He recommends Whole Food Plant Based. Also, have you had your B12 level checked? Just because you’re supplementing B12, does not mean you’re absorbing it. There are other possible factors at work here that are beyond the scope of this forum. Get professional help from someone well versed in this area of medicine.

    Dr. Ben

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