Doctor's Note

What about some other nutritional surprises? Check out these videos:
Does Coconut Oil Cure Alzheimer’s?
Does Coconut Oil Clog Arteries?

Be sure to check out the prequel video: Are Avocados Good for You?

To follow-up, see: Any update on the scary in vitro avocado data?

For more context, also check out my associated blog post: Tarragon Toxicity?

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  • Michael Greger M.D.

    Please feel free to post any ask-the-doctor type questions here in the comments section and I’d be happy to try to answer them. Be sure to check out Are avocados good for you? Also, there are 1,449 subjects covered in my other videos–please feel free to explore them!

  • It seems odd to me that they would include avocado leaves with the fruit. Perhaps that threw off their findings. I’ve never even seen an avocado leaf, much less put them in my guacamole!

    • Michael Greger M.D.

      They did separate experiments and found similar findings with both leaves and just the fruit alone, unfortunately.

  • I think I’ll just go with your insight that digestion may make this a moot issue and keep eating avocado. Thx.

    • Cant cure stupid.

      • Sailor Sharkey

        You could try changing your name. That might help.

  • Tim

    How common are “in vitro” studies like this? Is it fairly common? And if so, do you know of any other food which has caused such stunning genetic disruption?

  • Louis

    Michael Greger :”and then they took some avocado fruits, mashed it up”
    “concentrations of 50% methanolic extracts of Persea americana fruit and leaves”

    And what was the concentration of the extract ?
    “The mean percentage total aberrant metaphases at 100 mg/kg, 200 mg/kg, and 300 mg/kg concentrations of leaf extract”

    Is this the typical concentration we find in a fruit ? No, it is not !

    Michael Greger : “They did separate experiments and found similar findings with both leaves and just the fruit alone, unfortunately”

    Indeed, but the fruit extract at doses of 100 mg/kg, 200 mg/kg, and 300 mg/kg produced less genotoxicity :”The group exposed to leaf extract showed higher frequency of all types of aberrations at equal concentrations as compared to the group exposed to fruit extract”

    It is the fruit that we eat and this does not contain the extracts/concentrations used in this study. What is the concentration of the so called dangerous persin in an avocado ? Plant food we eat on daily basis contains a myriad of toxins. If you concentrate them and do the exact in vitro test, there would be nothing left to eat … except for meat …

    • BPCveg

      Louis asks: “Is this the typical concentration we find in a fruit ?”

      Reproduced from the cited article (snipping out only relevant details on the avocado fruit preparation):

      “fruits of Persea americana were collected … shade-dried at room temperature … fruit pulp was macerated with 50% methanol and extracted once with 300 ml of 50% methanol at room temperature for one week with occasional shaking … methanolic extracts of fruit … [were] concentrated to dryness at 60 ± 1°C in a rotary evaporator … fruit extract after concentration gave a light-brown, oily, viscous extract … crude extracts were used for further study as solutions/suspensions in double distilled water after removing the particulate matter by centrifugation and sterilization using syringe filters … blood cultures were set up with three different concentrations (100, 200, and 300 mg/kg culture medium) [of] fruit extracts”

      Please note: the unit of measure is milligrams of dried extract per kilogram of “culture medium”

      My interpretation: The methodology presented in the cited article provides no basis to infer that the so-called dangerous persin was actually concentrated… since the methanolic extracts were expressed in arbitrary units (with no relation to concentration of toxins specified), it could be that the persin was 1 billion times more concentrated than the normal state after eating avocado or 1 billion times less concentrated than normal or even equivalent to normal. We simply don’t know!

      Conclusion: This is bad science and meaningless from the point of view of making health-related choices!

      • I agree with this conclusion. This study also shows (or rather, ignores) that whole foods mostly act differently than their separated individual parts.

      • Ben Williams

        I agree with this. The study and this article are totally bogus. I am beginning to see a trend in Dr. Greger’s articles.


    • Simon

      ‘you can’t poison a goat’ refers to the way goats tend to eat a wide range of things rather than having a large amount of one thing, toxins in small amounts can be tonic

  • Veguyan

    I gave up meat, foul, fish, eggs, cheese, milk, sugar and white flour. I’m not giving up avocado!

  • OnestaOrganics

    How were the extracts made? Some solvents used for extractions are toxic by themselves…

    There is a big difference between dumping something directly onto cells as opposed to having something (esp. something non extracted) digested before food fragments come into contact with immune or any other kind of cells.

    As somebody remarked above, it is curious that leaves were also extracted. Why did they study this at all, do food companies include leaves in their products?

    Were the used avocados raised ‘conventionally’ which may explain some of the pesticides found?

  • DrSteve

    My question is: Does the “fruit” of the avocado in this study include the meat plus peel, or just the meat? If the peel was included, then this is an unnecessary scare story, as we do not eat the peel. As mentioned, these in vitro assays are not reliable enough to reject a fruit that is such an important source of vitamin E and essential fatty acids – not to mention delicious!

    • Michael Greger M.D.

      They just used the fruit pulp (no peel or pit).

  • yurple

    This is very disheartening. Avocado has been touted (in some of your videos, I believe? — not sure) as a superfood. How does a person reconcile all the conflicting info? I love this site and the invaluable info it provides, but it gets difficult knowing how to contextualize all the tidbits from isolated tests – often conflicting and/or focusing on different aspects of health – into an overall approach to eating. Clues?

    • DrDons

      Bringing together all the studies into workable “models” or beliefs can be challenging. Scientists wrestle with this problem as well. Some shifts are easy such as the journey many have gone through from “dairy milk does the body good” to “dairy milk doesn’t do the body good” to “dairy milk does the body harm” to “dairy milk contains toxins”. Once on a essentially whole plant based diet with B12 supplementation the confusion is still there but you have made tremendous strides. For me I use moderation as the keystone when studies like the one cited here come out. You have to decide. Keep tuned however as the science keeps changing.

    • Simon

      plants protect themselves with toxins, don’t eat too much of any one kind,
      and you can probably mitigate one class of toxins, lectins, by eating chicken skin to provide sacrificial glucosamine for the lectins to bind to,

  • DaySleeper

    For many years, I used four pounds of organically grown avocados daily, all year round, many varieties, purchased in 40 pound boxes direct from the farmer in San Diego County, Southern California. Eventually, whenever I ate avocados, twitching occurred in my fingers and sometimes my forearms, not much, but enough to scare me. The farmer’s widow, after the framer died, said that the farmer died of Parkinson’s disease, & she also said that another avocado farmer had also died of Parkinson’s disease. I’ve tried many times to resume eating avocados, but, after a short time, frequently the same day after just one avocado, the same twitching symptoms recurred. I’ve read that animals, such as goats, are poisoned by eating avocado leaves or pits. I ate only the pulp, always organically grown avocados. Perhaps the persin destroys some brain cells when excessive quantities are consumed, & over long periods of time, the damage becomes noticeable. In my opinion, all foods are potentially damaging in various ways so a varied diet is necessary, usually. Balance of nutrients & freshness are essential. Thank you.

    • BPCveg

      Hi DaySleeper,

      I’m sorry to hear about your bad experience with avocado…clearly this fruit is not for you!

      I was a bit confused by your hypothesis on what causes the symptoms. Your symptoms seem to occur “after a short time” and yet your hypothesis that “persin destroys some brain cells when excessive quantities are consumed” is, as noted by you, a process that would occur “over long periods of time”. I was confused by the mismatch of the time-scales for your symptoms and explanatory process.

      Have you considered an alternate hypothesis that you are having an alegergic reaction to avocado. There is data to support this possibility…the following link provides details:

      • OmTigressDoingGood

         You did not read closely enough.  He said that he consumed 4 pounds of avocado daily for many years….and after he first started noticing symptoms, only 1 avocado in a day would quickly bring back the symptoms.

        • BPCveg

          Good point. I now realize that I failed to notice the extreme consumption.

  • BPCveg

    It is unfortunate that the researchers who performed this study did not measure the concentration of persin in the avocado fruit extract that they prepared. In the article, so many arguments are given about deleterious effects of persin and yet the researchers never report the actual concentration of persin in the culture!

    As the researchers reported in the discussion section: “There is also a possibility of certain component/components causing the genotoxicity being scanty or absent in the fruit while being present in higher amounts in the leaves. This can only be resolved by isolation and characterization of the active constituents responsible for the observed genotoxicity.”

    It remains to be proven that avocado is harmful to humans. The present paper, though provocative, presents a weak argument for rejecting avocado consumption!

  • bgrune

    Thanks for the info. Glad to see that most viewers are able to put this study in perspective. Many phytochemicals in fruit an vegetables are undoubtedly toxic when studied in isolation. This type of reductionist science is interesting but not very helpful in my opinion. I will continue to eat avocados in moderation as a small part of a diverse whole food plant based diet.

    • robwilly

      As someone who has eaten at least an average of 1 avocado per day for many years, I think a petri dish study is alarmist at best, and the good doctors who throw this at the public without good human studies are not doing anyone a favor.  The gentleman who ate 4# per day could have had a lymphatic flow impairment, a B6 deficiency, or a gall bladder issue.  The persin is probably neutralized in the intestinal tract in most healthy individuals is my guess as to why the world has not been destroyed by the millions of pounds of avocadoes consumed.

  • Harel B

    Thanks for the info MG and for reminding us about in vitro vs invivo..I’d like to know what the results are if they do the same (in vitro) to the top 100 most common foods…and classify the results from 0 (no damage) to low, medium, high, and compare where those foods effects are versus of avocado. I assume it’s not *common* for this to happen when you do this in vitro and put food on the cells…but is it unheard of? OR are there foods where similar things have been seen, and, those foods are (nevertheless) from epidemiological studies seem not to dangerous after all.

    I mean if even just one single other food does this *and* that other food from population studies seems harmless after all, then that suggests that the in vivo is maybe more benign  (but does not prove it, after all it could be that avocado digestion does not save the day but digestion of that other food does)

    Another idea/question – population studies directly comparing avocado consumption with effects years alter either in disease, or give people a blodo test years later and see if they can detect problems in the blood (or DNA found elsewhere)

    Seems to me like either of the above could give us additional clues making avocado consumption (in moderation) seem either more “guilty” or less “guilty”  depending on the results.

  • Barbara

    I had 3/4 of a Hass avocado this evening and reacted to it. I don;’t always react, but often enough to decide there is something wrong. My search identified persin as the toxin. I wonder if the thin-skin varieties of avocado might have much less toxin in them. Any thoughts on this?

  • Toxins

    any updates on Avacadoes in vivo?

    • I’m happy to report that a new study this year found avocado consumption associated with significantly reduced prostate cancer risk (a third cup of avocado a day or more associated with 60% decreased odds of prostate cancer compared to men eating less than a daily tablespoon). Holy guacamole!

      • Madiha M.K

        Dr. Greger, how does that invalidate the conclusions of this in vitro study? Just like cassia cinnamon is toxic, it also has a positive effect on blood sugar. So how does avocadoes preventing prostate cancer erase any potential negative effects of consuming it? What if it’s both? A future video elaborating more on this would be appreciated.

  • James Thompson

    A year later the same authors wrote: Avocado fruit (Persea americana Mill) exhibits chemo-protective potentiality against cyclophosphamide induced genotoxicity in human lymphocyte culture. that concluded: These studies suggest that phytochemicals from the avocado fruit can be utilized for making active chemoprotective ingredient for lowering the side effect of chemotherapy like cyclophosphamide in cancer therapy.

  • brux

    Dr. Greger, I discovered your videos on You-Tube about a week ago and have been watching them as well as exploring your website here. Most of what I have been hearing has been very interesting and informative however when I hear studies like this it makes me a little crazy – I don’t know how to evaluate it. You read it in the same straight voice you use in all your other videos, and the source and nature of the study has no really differentiation from any of the other videos, but I do not know how serious to take the procedure used in this study?

    Would one not get the same kind of results dripping water on blood cells … they would explode or implode wouldn’t they? Or virtually any other liquid no matter how benign it seems to us on the macro level it seems like would cause a problem if dripped on blood cells directly.

    Is this a recognized and validated method of research? As I have been moving towards veganism for a little over a month now it is difficult to think that I have to start calling some fruits and vegetables friends and others enemies because of things like this. I am tempted by what I think is my better judgement to just ignore studies like this … but then again my bad judgement in eating the average American diet for over 40 years makes my own judgement a little suspect! What am I supposed to make of this please?

    • If you look under the “Doctor’s Note” above, there is an update posted, which should help put your mind at ease (certainly did for me!).

      • brux

        I was more concerned with the whole methodology of this study and then others that are cited where they drip juice on cells and things like that. Thanks for the reply, I appreciate what you are doing here, and in such a fact-baed and entertaining style as well!

  • Michael

    Has there ever been a study of the affects of persin (amounts typically found in a serving of Avocado) on the human body when digested by humans? It seems this study doesn’t give us the full picture of how persin affects the body after it is digested, frankly it scares people. Your follow-up is comforting, however still leaves a cliffhanger as to whether it’s better to consume or avoid Avocado’s!

    Who funded the avocado study and it’s affects on our blood?
    Could it have been the meat industry trying to scare vegans and the like?
    Do you consume avocado and if so in what quantity?

    Thanks Dr. Greger, excellent site and presentation of the information.

  • Russell Dee

    Dr. Esselstyn, one of the few doctors out there successfully treating heart disease without surgery, says oils are very bad for the heart. check out what he says about oils in this interview:

    I’ve personally spoken with him on the telephone and he says that avocado oil is the same as olive oil and other oils which are very bad for the heart. He says that they play a role in causing arteriosclerosis which leads to heart attacks. In his book “how to prevent and reverse heart disease” I think he specifically says to stay away from avocados and he says that the lower incidence of heat disease and heart attacks among the people who digest olive oil and avocados is a mirage. He says that while those people do have lower rates of heart disease and heart attacks than the people who eat the western diet, they still have higher rates of heart disease and heart attacks than the people who stick to a plant-based diet and also stay away from olive oil and avocado oil. He says the people with the lowest rates of heart disease/heart attacks are the people who eat a plant-based diet except for the plants with oils. He adds that the people who eat a plant-based diet including the plant food that have oils (avocados and olives) have lower rates of heart disease and heart attacks than the people who have a meat-based diet but they could lower their heart disease/heart attack rates even more if they stopped eating olive oil, avocado oil, and other plant based food with oil.

    • brux

      People have their different sources they believe, but what make Dr. Esselstyn’s word gospel, and isn’t it most likely that no one has all the answers as well as realizing people’s message do not just freeze, they evolve and hopefully get smarter. A freezing message is an example of a product sold for a profit, and low and behold we see Esselstyn’s name on supermarket products now. How can I be sure that any time I see his name it’s not just some guerilla marketing … that that guerilla marketing is always bad, but convincing people of things in order to sell them things is a pretty big racket.

      > He says the people with the lowest rates of heart disease/heart attacks are the people who eat a plant-based diet except for the plants with oils.

      This sounds like something that makes sense, but I really doubt there is enough obejctive data to prove that because there are so many variables and and reporting them is often just subjective.

      • Russell Dee

        Brux, either the evidence backs Esselstyn up or it doesn’t. That’s what it gets down to.

        Does Esselstyn make a profit off of his ideas? I think he does. Is Esslestyn allowed to make a profit off of his position? Of course. It’s still a capitalistic world. If you came up with an idea of how to cure a disease that lots of people have and is killing lots of people I bet you would give it away for free and not try to make one penny in the process. Right!!!!!

        The thing is that they did studies that show that the Mediterranean diet is way better than the American diet but there are other studies that show that the Mediterranean diet can be improved. Even better results can be achieved.

        In his book Esselstyn talks about how some sections of the Asian population were not seeing any hear attacks or heart disease. The people living on a plant based diet even avoiding the oils were free of heart disease and free from heart attacks. Then western culture started encroaching into hose populations and all of a sudden they are seeing heart disease and heart attacks. The older generations in those sections of the Asian population are still seeing little or no heart problems because they live by the old ways and the old diets and the younger generations ridicule the older people in those parts of Asia calling them jungle people and the like. But the older people eating a plant based diet and staying away from oils are still staying free of heart disease and heart attacks while the younger generation that is more and more adopting western culture is seeing more and more heart problems.

        • brux

          I’ve heard the evidence, and seen videos from Essylstyn and others, as well as the summaries of studies here. I think there is room for disagreement, and no one has real proof. Yes, there is data to support Essylstyn’s hypotheses, but they do not know what all is going on here. I am working on keeping vegan, but I don’t want to be a fanatic about anything – no one understands this completely, so while I eat mostly veggies, I will occasionally eat oil, or cheese, meat or dairy, I just try to keep it way down. One of the most interesting videos I’ve seen is the one about intestinal flora and how it reacts to meat. Everything now has chemicals in it, pesticides, antibiotics, metals … it is disgusting how we have treated the planet and industrialized our food supply. I think organic, fresh and vegetarian mostly is a good way to be … past that, I don’t know for sure and I am not sure I buy Essylstyn’s views, logical as they sound.

          • H Barzilai

            Even though I use olive oil, I suspect oils (not whole foods) are iffy…but whole foods? He makes a stronger claim that whole foods (avocados, in moderation for example) are bad, ok, please post some links, or just one link, to a study that did the comparison.

            (personally I have about 10+ blood readings of my trigl. levels, about 7 before, when I had a super low fat vegan diet, and about 3 after…my readings got much better, lower, after I made the change to moderate-low from super-low fat vegan diet)

            And even if there was 100 studies showing better heart health for super low fat versus medium-low fat vegan whole-foods diet, that’s still not the end, because heart health isn’t the only component of health…and for other components of health the results might be the opposite..but even for the narrow question of heart health, I have read or skimmed all this exchange and still not seen a link to a study peer reviewed, double blind etc, comparing the two. (then I’d like to see Greger’s analysis of such study/studies)

          • brux

            A lot of the media stuff we see are linear extrapolations from some fact that someone digs out data mining some big study. I just do not think we know the perfect answers to these questions, and like you said heart health is not everything. I wish I could stick to a strict vegan diet, and I do try for the most part, but it’s just almost impossible. I feel I know the general parameters, and low fat, and especially as little animal fat as possible is better … but I am not sure some, such as fish oil is not good for you. To define rules based on who shouts the loudest of give the best video talk doesn’t make sense to be me. I just try to keep taking in information, it could be hundreds of years before we really understand everything – if we, human beings, are still here.

          • I don’t think we will ever understand everything. Colin Campbell’s recent book, Whole, discusses the limitations of reductionistic approaches to understanding complex systems. They are useful but the limitations must be understood. I also believe most people would benefit from a better understanding of statistics and risk/benefit. It does boil down to biochemistry. Given our current food environment sticking to a plant based diet is a challenge. Current studies don’t show any value in consuming fish oil. It is a journey… stay tuned as the science keeps coming.

          • brux

            Reductionistic, ie linear modeling only works in certain situations, and is usually good to demonstrate the effects a certain variable has one a complex system, not as a way to measure, quantify or control that system. Somehow we have allowed all life in Western civilization to be reduced to this industrial machine input and output … well, that is, except if you are rich enough to be able to escape that system and rise above it. But then … what’s Western about that the way that system, our system, is now?

          • H Barzilai

            Just to clarify, when I said ” I made the change to moderate-low from super-low fat vegan diet” I meant “change to moderate-low VEGAN from super-low fat vegan..” Just adding more nuts, adding some avocado, and wise or unwise, adding more olive oil…lower triglyc, was strongly correlated with this diet change.

            I don’t use fish or other animal products but as Greger put so well in a cooking video he did a long time ago, don’t guilt trip yourself, if you can be 90% or x% vegan, you’re still doing a huge amount for your health, for the environment, and for the animals.

            I personally think dairy is more iffy than fish, but if you’re using fish, I’d research real carefully about heavy metals, then I’d research if there are any other chemicals, or hormones, then I’d reserach it is GMO fish, and if officially not, is it near another population that is that in 5 years they’ll tell you “oops, there was GMO contamination with fish interbreeding” as we know happens with plants, etc, just more to worry about to avoid, and research

            “If you want others to be happy, practice compassion. If you want to
            be happy, practice compassion” -The Dalai Lama

      • Lola

        I think you are seeing products connected with Dr. Esselstyn’s son, Rip.

  • brux

    > See also yesterday’s “prequel” Are Avocados Good for You?

    And today it is “Are Avocados Bad For You” … at least there is somewhere in the media where the Fairness Doctrine still applies! If avocados are bad, or contain substances that are toxic or carcinogenic, doesn’t that mean that virtually everything does to some extent?

    Are we supposed to somehow classify all plants as to whether they are above some good v. bad level and only eat certain fruits and vegetables?

    I never used to eat many avocados … usually only in guacamole, or on turkey sandwiches, but since I started to eat more vegan fair I buy avocados pretty regularly, sometimes eating them for breakfast, or on a veggie burger sandwich.

    Since so many plants have so many different chemicals, and the body can never guess what chemicals plants will evolve, isn’t it reasonable to hypothesize that the human body has some mechanism to filter out or ignore most of these insecticide and fungicidal compounds? Is science crazy or are we on the step of a new understanding of how the human body and nutrition work?

  • Gio

    Tiny problem: were the avocados in question ripe? Unripe avocado is what the vast majority of people (including scientists) consider ripe when it’s not. A ripe avocado is soft, something like spreadable cheese. Ripe avocado are chemically different from unripe ones as it happens with most fruit. Usually unripe fruit contain toxic chemicals not present or much less present in ripe fruit.

    Thank You.

    • I think this is very, very important!

  • Avocados!!!

    I bet the persin is the reason it is toxic to all animals except humans. I am so curious why that is.

    Considering how destructive it is (given the video above), if our digestive system didn’t neutralize the persin, I’m sure we would have the same reactions as other animals (diarrhea, death, or death by diarrhea!)

  • EP_2012

    What about avocado oil on the skin? Seems to be a popular ingredient in many natural products. Since an external application is similar to data mentioned in the above video, could it cause the same DNA damage?

  • Ruby

    I can only hope that this ridiculous report is not being passed off as “scientific”. I won’t harp on the lack of cause and effect scenarios, proper scientific procedure to test a hypothesis and so on. A first year grad student wouldn’t be allowed to publish this tripe, assuming such a poorly designed project even got approval.

    • Ruby

      As an aside, I will advise my DNA not to expose itself to anything while residing in a test tube without first obtaining my permission.

  • Yan Yee

    Hi Dr Greger, have you got any input on premature infertility and diet?

  • Bret Iron

    Hi! I can’t find anything online thats consistent about testing and effects or treatment about candidiasis. Would be greatly interested in your findings! Thanks for all you do!

  • Doug

    A VERY engaging discussion on avocados. I am a loyal subscriber to the site and have been reading this avocado debate with enthusiasm. In reading all of the valuable and thoughtful input from past input, one comment jumped out at me. Gio made the point that properly ripened avocado is quite different in chemical structure than the partially ripened fruit. This is true for any plant product as an enormous part of the maturation process takes is responsible for changing the basic chemical structure of the end product. Personally, I followed a somewhat typical western diet for most of my life, making a few attempts at a vegetarian or vegan diet several times in the past; however, travelling significantly in my work, I found the lifestyle virtually impossible. Now, being faced with a very high PSA level, I have devoted to a nearly vegan lifestyle, having sworn off of ALL dairy, sugars, animal proteins (with VERY limited and infrequent exceptions of fish). I seldom cook vegetables other than the obvious, such as dried beans. The avocado toxicity paradox has me reeling and not knowing how to take these conflicting study results. I am; however, quite relieved and pleased by the positive avocado/prostate health study results. The individual who consumed pounds of the fruit daily, it seems to me, was begging for overreaction, simply by overindulgence. In my present diet, the few portions of ANY fat that I receive, I receive from avocado, nuts and olive oil. We know that fats are essential for brain function and development and goodness knows, I need all the brain function that I can get. My diet of the past two years is composed mainly of varied raw cruciferous vegetables, small but frequent asparagus portions, beans, raw spinach and nuts with olive oil and one avocado daily, all organic when possible. Being raised on a cattle and rice farm, this would seem to be a major departure; however, it is a departure in diet only. I question if any studies have been conducted on populations that have consumed high portions of avocados in their traditional geography and culture. These folks would be excellent subjects, rather than studies based upon westerners who have tainted their DNA, traditions, dietary makeup and general chemistry with the toxins, additives, GMOs and impurities that they have encountered in our typical environment. Any word or opinion on this would be welcomed.

    • Thea

      Doug: Nice post! I like your analysis.

      I’m afraid I don’t have much to add to your discussion. (Hopefully others will jump in.) But I wanted to say that I also appreciate a good avocado!

      Also, I’m curious if your diet changes have helped your PSA levels. Or is it too early to tell? I’ll think good thoughts for you.

      Finally, I wanted to say: There are plenty of people who would rather die than change their diet. So, it means something significant that you were able to make this change that was difficult for your. Congratulations. I hope it leads to a long healthy life. Best of luck.

  • joe

    Hi Dr. Greger,

    This video is now has now prompted me to write you, I really hope you can find the time to respond … For years I’ve been trying to live by a plant based diet, but failed several times. As a runner I need good protein to recover and keep a healthy weight. On plant sources alone I simply lose too much weight (dropping to 130). As it is with chicken 2-3 times a week and avocados (walnuts too for the fats). Im 140 at 6’2. I was recently determined to be slightly anemic and my doctor also wants me to gain weight saying I have too low BMI. Main sources of many meals is oat meal, berries, walnuts (breakfast) and beans (black, red, kidney, pinto, lentils, pearly barley) , perhaps black beans and a vegetable at lunch and lentils at dinner. My doctor has also warned me about the high level of oxalates with my diet and the risk of kidney stones. Perhaps the oxalates also caused the anemia to begin with? So I kindly ask of you could you point me in the right direction? perhaps a sample weekly meal plan you follow? Is eating 3 times a day ok or should I be eating more frequently? Please this would be greatly appreciated. Thank you for reading and thank you for your time.


    • Thea

      joe: I hope Dr. Greger is able to respond to you, but I know that he rarely has the time now a days to respond to indvidual people. So, I thought I would reply in case I can help. I’m not a doctor or an expert, but I have some ideas that relate to your situation.

      There is a frequent commenter on NutritionFact named “VeganRunner”. I’m hoping she will see your post and comment. But if not, maybe you could find one of her posts and ask her how she thrives on a plant based diet while being a serious runner.

      One of my favorite reference books is the revised express edition of a book called “Becoming Vegan” by Brenda Davis and Vesanto Melina. Based on past posts, I know that Dr. Greger also has a lot of respect for Brenda Davis. I think he would approve of my recommendation that you get the book one way or another so that you can read the chapter on gaining weight. It is really excellent and will tell you how to gain or maintain your weight in a healthy way. The book includes meal plan examples for various calorie levels.

      Another idea is to look for some of the vegan athlete websites out there. I know that there is at least one that feature vegan athletes in general and another one that focuses on vegan body builders. You could gain information from those sites and might be able to ask questions. Similarly, I believe that there are some good vegan athlete books out there which also include meal plans.

      Dr. Greger has some videos and articles about kidney stones and oxalates that might make you feel better:

      I’m no expert, but based on what you describe, your diet sounds pretty on track! – minus the chicken. (2 to 3 times a week. yikes!) If you have time to look around on this site, you will see how great berries, walnuts and beans are for you. I’m thinking that it will just take some tweaking of your diet to meet your needs. Assuming no underlying medical condition, if you are losing weight, you are not eating enough. As you can see in Brenda’s book, there are some pretty easy ways to fix that.

      I think it is really great that you are trying to be as healthy as you can. I wish you luck on your journey and hope this post ends up helping you.

  • kevin

    Don’t avoid avocados. These scientists get bored and do these nonsense studies to confuse folks. Greger even says “we don’t know what happens when we eat avocados” This petrie dish stuff is a waste of time – much like studies on rats – We are humans, NOT rats ! I find it so hard to believe that a food from Nature can be bad for our health. Misinformation is bad for our health.

  • Tom Lang

    This is truly weird science and of zero practical use. Why not study people in Southern California or Mexico who actually eat avocados and salsa virtually every day of their lives versus dripping avocado extract onto human cells in a petri dish. This is perfect example of how to waste money on weird research.

  • Kenny Mong

    Aww shucks just bought avocado fruits last week and I still have 3 more to go….

  • KES1983

    Those of us that raise chickens know that all parts of avocados are toxic to them. Perhaps it is the same toxin that affects them, but to a greater extent.
    I think this is a great example of “Everything in moderation!” and we should strive for variety in our primarily plant-based diets or whatever diet we consume.

  • Skip

    Can Avocado seeds really be so wonderful?

  • Linda

    I wonder if avocado is a choice for someone with liver disease per the reference to it detoxifying role in the avocado. Does the generous doctor have an opinion?

  • Kondratowitch

    Is this information valid:

    Home » Health » Health Tips » Avocado Seeds – Super Food for Super Health

    Avocado Seeds – Super Food for Super Health

    April 4, 2015
    Avocado Seeds – Super Food for Super Health2015-04-05T03:37:27+00:00
    Health, Health Tips

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    The Avocado is also known as a super food that can give our bodies
    some of the healthiest nutrients. Worldwide , the avocado is considered
    to have the most soluble fibers.

    Eating one avocado provides our body with the entire daily needed
    fiber dose. Compared with other vegetables and fruits, it contains
    various types of antioxidants.

    The Benefits of Consuming The Avocado Seed

    One astonishing thing is that the skin and the flesh of the avocado
    contain only 30 % of the antioxidants and 70% of them are present in the

    These antioxidants lower the cholesterol
    and prevent different kinds of diseases especially heart diseases.
    They also reduce inflammatory diseases and calm soreness in
    gastrointestinal tract.

    Since the avocado is rich in fibers it can prevent constipation and
    ease diarrhea. Phenolic compound is an antioxidant present in the seed

    It helps relieve gastric ulcer pain which is caused by antibacterial and sometimes anti-viral properties.

    Looking for more reasons why you should eat avocado?

    Another important antioxidant known as flavonol is also contained in
    the seed. This antioxidant can help in fighting cancer. So, avocado seed is the perfect food for people suffering from cancer since they are adviced to eat foods rich in flavonol.

    If you have a weak immune system and often get colds during the flu
    season, including avocado seeds in your diet is the perfect solution for
    you. Consuming avocado seed will help you strengthen your immune system.

    The fundamental reasons why people get sick , get cancer and get
    older rapidly are the free radicals. The avocado seed can help you in
    preventing all of these by fighting free radicals. Having the ability to
    build up the collagen below the skin, it can help you get a young and
    fresh look.

    And that’s not all you get from avocado! It will make you become more
    active by cutting down body aches, joint pains and bone diseases.

    Losing weight and
    lowering blood glucose level are another two benefits you get from
    consuming avocado. It can help with exercise-induced asthma and if you
    feel food cravings it will make you feel fuller.

    How to Extract the Avocado Seed

    If the avocado is ripe it will open easily . Just take a knife and
    cut it vertically from both sides. When you have taken out the seed you
    can make a smoothie: Put it in a plastic bag and smash it with a hammer.
    Then put it in a blender along with other ingredients like spinach,
    bananas dates etc.

    If you have a more powerful blender, put the avocado seed with the
    other ingredients without crushing it before. Don’t forget to add some
    water. After the preparation make sure you enjoy drinking it!


  • joshua

    ahm sir can i ask? is it possible that an avocado leaves(persin) may be used as pesticide?

  • joshua

    ahm sir can i ask? is it possible that an avocado leaves(persin) may be used as pesticide?

  • Sinclair

    The insecticide and fungicide should not be found in organic avocados, should you only be concerned about non-organic or does the DNA cell damage occur naturally in all types? Are there harmful properties within an organic avocado, even if it does not have these toxic chemical fertilizers? Has there been any evidence completed on organic avocados or is there only a concern on non-organic?

    • Shaylen Snarski

      You know what, studies should ABSOLUTELY be done separately for organic produce. That is such a great point. Also in his book “How Not to Die” he says he consumes avocados for baking apparently and talks about the healthy fats in them. Too much contradiction! It’s so frustrating… My philosophy always seems to be proven right in the end though… trust in plants.

  • Joe Caner

    Oh! Great sadness.
    Oh, woeful day!
    I have recently purchased five beautifully ripe avocados, and have so far eaten one of them. I was curious to discover all of the wonder benefits that the research had to say about avocados only to discover that they have been shown to destroy chromosomal material in vitro.

    Holy Un-Guacamole indeed Dr. Greger!
    I guess from now on, no more creamy guac-goodness.
    It looks as if I am back to only using creamy peanut butter as my smear of choice.

    • Thea

      Joe Caner: All is not lost! This is one of Dr. Greger’s early videos. I did not find it all that compelling, and it turns out that this one is not all that compelling to Dr. Greger either. After seeing your post, I checked the index of Dr. Greger’s new book, “How Not To Die” for ‘avocado’.

      Avocado is mentioned in two places. The first place Dr. Greger mentions avocados in the context of discussing a “good fat”. In the second place, Dr. Greger says that he currently uses avocados as one of the ways to bake without oils.

      So, while I would say that you wouldn’t want to make avocados the center of your diet, I don’t think you have to look upon them as a terribly rare treat either. Enjoy them!

      • Joe Caner

        Thank you for the encouraging words Thea. I do love avocados, although, I eat them only when I can get a perfectly ripe ones that are ready to eat.

    • Shaylen Snarski

      I know so many people who use avocados regular lily and have read studies how people who eat them regularly have improved health. I never experienced any adverse effects whatsoever and have read time and time again how amazing avocado is for the skin. So yes, I’m weary of this. Further more, I’ve been reading comments that in his book, “How Not to Die,” Dr. Greger talks about the benefits of avocados and gives them the green light!

  • alot

    I was hesitant to go vegan because I feared the weight loss, I love my weight. Anyway, one month ago I took the plunge and decided to eat an avocado every day, so I would not lose my precious pounds ! It worked, I have not lost any weight but the avocado gives me gas. I asked my doctor and he said I probably no longer possess the enzymes to digest it so I should avoid them. Unsatisfied with that answer I came here hoping to get a solution as to how I would keep my every day avocado habit and holy molly, apparently I should stop eating them. Now where I will get that extra 400 calories from? I already eat nuts for breakfast !

    • Thea

      alot: Some ideas for you: First, Dr. Greger mentions avocado in two places in his new book, How Not To Die, and does so in a positive way both times. The second time, he even lists avocados as a “green light” food. Given how old this video is, I’m thinking Dr. Greger may have a different perspective on avocado now.
      Second, I think that this particular study/evidence is pretty weak. I don’t speak for Dr. Greger nor do I have any special insight into this matter, but my opinion is that I don’t think Dr. Greger would have highlighted this study had he come across it for the first time today.
      Third: I don’t know how much avocado is healthy or not. Too much can be unhealthy, especially if you have cholesterol issues as avocado is especially high in fat – which is why you like it for weight maintenance because it is calorie-dense. My point is that while avocado may be a generally healthy food, like *any* food in the world, there are still going to be amounts that are too much. Is an entire avocado a day a good idea? I don’t know…
      Fourth: As a complete lay person, in an effort to bring balance to the diet, I suggest considering cutting back to maybe 1/2 avocado a day and adding in other higher-calorie dense foods such as dried fruits and tofu or tempeh. And maybe just eating more quantity wise of healthy whole starches like beans and sweet potatoes (if you can get more food into you).
      What do you think?

      • alot

        oh thanks Thea !! I actually cut back to 1/2 an avocado a day and the digestive problems are gone ! However, despite my efforts to eat more, I have lost some weight . My face looks older and my I cannot lift the heavy weights that I used to do easily when I was an omnivore. I try to eat nutrient dense and protein rich foods till I am completely stuffed. But I just have not been able to avoid the weight loss from eating a WFPB diet. Are there any videos here that help vegans gain weight healthfully?

        • Thea

          alot: You are getting out of my area of expertise. But I do know that some very successful body builders have made strides after turning vegan. I can share some examples with you if you are interested. But the bottom line is that it is possible to eat a generally WFPB diet and gain weight, even gain muscle I believe. (One man went on to make a world weight lifting record *after* going vegan.)

          You might check out some vegan bodybuilding and athlete sites. Even if you aren’t interested in being a body builder, I would think you would get ideas on how to meet your personal goals. Good luck.

        • Shaylen Snarski

          I became so much stronger since becoming vegan. Are you getting enough protein? I know there’s lots of vegans who say you don’t need much, but I disagree. I think protein is super important but you can get it in ABUNDANCE from plant foods (and it’s far superior protein at that!). It sounds like you’re not getting enough protein, maybe even calories, maybe even fat. My skin has never looked better, I eat a lot of healthy fat foods and use extra virgin olive oil on my salads and sometimes take algae DHA supplements (omega-Zen pure DHA because it’s the purest and there’s no palm oil added, which is so unethical as well as unhealthy). I like to drink Garden of Life protein shakes sometimes (Beach Body vegan protein shake is very similar and cheaper for the amount you get) and I eat lots of nuts, seeds, beans, etc. Quinoa is a really great source as well.
          Other factors can contribute to the things you’re describing, like not getting enough copper, zinc, iron, selenium, magnesium, etc… I would get your mineral levels checked. Eat as much whole plant foods as possible and learn about all the nutrients you need. I know Dr. Greger suggest getting all your nutrients from whole foods, but in this day and age, I think a multi vitamin is important to take as a back up.
          I love Dr. Greger but some of his videos and such really contradict one of another and it gets frustrating but I think it’s because science is like that… new studies come out all the time and honestly, they’re never going to really know everything. We need to just trust in plant foods because that is what’s proven time and time again to work. I also read where avocados were very beneficial to people who ate them regularly, but I don’t remember the details.
          Anyways, if that was or is your only source of fat, that definitely isn’t good for the skin imo and experience. I notice the more healthy fats I eat, the better my skin looks.

        • Shaylen Snarski

          Your body may also be detoxing. Animal flesh and secretions have so many harmful effects on our bodies and toxins can build up, such as heavy metals. Plant foods rid our bodies of these things but the detox process can make you tired, weak, sick feeling (flu like symptoms can even occur). I’d get your vitamin and mineral levels checked and eat as much healthy whole plant foods as possible and increase your protein intake with things like tempeh, quinoa, beans, lentils, seeds, nuts, etc. I personally find organic whole foods based vegan protein powders to be very convenient. And you should probably be supplementing with B12, I believe 5,000 IU once a week will keep your levels perfect. Vit. D deficiency can also cause some of the things you’re describing. I’d take a vegan vit. D supplement. I take one from mushrooms plus there’s some in my vegan multi in the form of lichen.

        • I agree with the other comments you may not have enough proteins, You have to adjust the portion but also the diversity.

      • Susie

        “Given how old this video is, I’m thinking Dr. Greger may have a different perspective on avocado now.”

        In that case, Thea, perhaps Dr Greger could update this video!

        • Thea

          Susie: As of this writing, that’s not how the site is operated. Instead, it is recognized that the science changes over time. New videos will update us on the new information. The old videos are kept, I imagine, for documentation purposes and to save the comments and because some parts of the videos are likely still relevant.

          • Susie

            That could be rather confusing.

      • Thea, avocado has no cholesterol, and is very well documented to lower LDL by competitive inhibition. It is a fat burner used in many weigh loss programs as walnuts citrus etc.

        • Thea

          Claude Martin-Mondiere: Avocado is a very high calorie-dense foods, just like walnuts. For that reason, while I might eat some small amount of avocado, I would highly restrict the amount I eat if I were trying to lose weight.

          • I have coached people to lose weight for medical reasons, because to have a healthy weight is a start to correct many chronic diseases. Avocado has 20 times more fat than any other fruits, but no cholesterol, low in Na and sugar :160 cal/ 100g with 8.53 in carb , when walnuts is 653 Cal/100g. Then avocado fat is only 15% is saturated fat.

    • When I wrote The avocado affair it was to start with the aphrodisiac effect of the fruit for Valentine’s day, My daughter gave the title and the recipes and asked me to correct the nutrition aspect. In fact the main thing I discovered, and I knew as a consumer was to pair it with other food. Avocado is a functional food, see my FB page , I use it as a substitute for egg, butter and dairies, I rarely eat it alone as I eat a tomato.

  • Taras

    Is there any update on avocado?

    • Thea

      Taras: To my knowledge there isn’t a new video on avocado, but in Dr. Greger’s new book How Not To Die, he talks about avocados in generally positive ways. There is even an example in the book, if I remember correctly, where Dr. Greger talks about personally enjoying guacamole.
      I personally would eat avocados in moderation/ with care based on their high calorie density. But I don’t think the issue raised in this video is something to worry about. That’s just my opinion, so take that for what it’s worth.

    • I have published in my Facebook page and my website few things before to publish the Avocado Affair” now in the process to be available in ebook and paper. It took me more time I wanted because I found more information and it may be interesting in preventive medicine, anti aging as well as for brain development for babies..

  • Sarah Tabler

    Hmmm… This information is highly disconcerting. Avocados have always been the one food I could live off of for the rest of my days, I adore them endlessly. I wonder what Nikocado Avocado (fellow Vegan from YouTube) would have to say about this! :(

    • Thea

      Sarah Tabler: From reading Dr. Greger’s new book, How Not To Die, I would say that Dr. Greger’s stance on avocados has changed. Dr. Greger doesn’t spend a lot of time on avocados in the book, but when he does mention them, it is in a positive light and this study is not mentioned. I guess that Dr. Greger no longer considers this study to be so compelling. Dr. Greger even mentions in the book that he eats guacamole at times.
      Are you less disconcerted now? :-)

      • Sarah Tabler

        Thank you for this information Thea! I have been wanting to purchase Dr. Greger’s book since it was released, but I’m waiting on saving up enough money to do so. I cannot wait to dig in and read it. I am grateful Dr. Gregor cares as much as he does to share this vital information with us all. I’m relieved that he is generally positive about this matter now then, perhaps given new information he’s gathered regarding avocado and how it functions once consumed and so on. As a Vegan, I’m always more than happy to abstain from Animal products, but when I hear that there exists a much loved plant that may not be so good for our consumption, it gets rather saddening. All things in moderation, even the good, sometimes rings true :) thanks again for your reply. Take care!

        • Thea

          Happy to help. :-) Thanks for the feedback!

  • I am just finishing to write “the Avocado Affair’ has a MD PhD, I did fact checking, and extended research in the different health benefits we may see everywhere about avocado. I am not pay by the Avocado industry who refused to answer to my questions. There are components, considered as nutraceutical one is Avocatin B that seems to protect the cellular level against the toxic of cancer cells . Epidemiology shows that the populations eating avocado regularly have a lower risk of prostate cancer and cardiac diseases as well as neuro degenerative diseases. I did a work on the modulation of antigenic expression on MS patient lymphocytes with myelin, because I was the first in the world to discuss the change in the balance in the T8 and T4 population of lymphocytes . I did the first publication in the Lancet in 1980 proving my personal observation (Claude Martin). I did more sophisticated studies and published in peer revues as Immunology,.The study described here is just showing an activity in vitro that must be reproduced with a better technology to be a significant warning. I am looking to join foundation for nutrition to explore few element of interest in avocado. It is the only fruit we know from the tertiary era, and we have more to know . India as other poor countries are trying to use the nutritional properties of avocado to correct a number of food deficiencies in low income population. There is the same problem in Africa. I will continue to advice to eat avocado .

  • Sandra Krause

    I have an anecdotal story regarding Avocado toxicity. My husband and I were traveling home (Boise – Seattle) about an 8 hour drive. I had 4 avocados in the trunk in a plastic bag. The temperatures were not exceedingly high – maybe 75 degrees a peak and maybe that temperature for 2 hours. I decided to use 1/2 of one of the avocados for tacos. When I took it out it the skin was a little moist, I thought probably from some heat in the trunk, but we often put avocados in a bag in a warm place to ripen, so I thought just glad they didn’t go bad…Well about an hour after eating, my husband experienced some tightness in his throat and a little difficulty swallowing. He took a couple Benedryl as a precaution. About 20 minutes later I experienced the same symptoms (I ate a little later than he). The Benedryl did the trick, but kind of a scary experience. After reading a bit about avocado toxicity we decided that possibly a large amount of Persin may have leached into the pulp of the avocado from the combination of heat and plastic bag. We’re just curious what your thoughts might be about this.