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Are Avocados Bad for You?

The insecticide and fungicide compound found naturally in avocadoes (persin) may damage the DNA of normal cells as well as cancer cells.

October 10, 2011 |
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Supplementary Info

Are Avocados Bad for You?, 4.1 out of 5 based on 10 ratings

Sources Cited

Kulkarni P, Paul R, Ganesh N. In vitro evaluation of genotoxicity of avocado (Persea americana) fruit and leaf extracts in human peripheral lymphocytes. J Environ Sci Health C Environ Carcinog Ecotoxicol Rev. 2010 Jul;28(3):172-87.

Acknowledgements

Image thanks to YinYang.

Transcript

Published just last year, an in vitro evaluation of the genotoxicity of avocado fruit in human white blood cells. This study was not funded by the avocado commission; maybe its Big Salsa trying to muscle in on the guac market.

A simple experiment. They took normal human cells. And the easiest way to get human cells is to just take a blood sample. It's kind of the easy way out—that's what I did for my research work at Cornell.

Then they took some avocado fruit, smooshed it up, dripped a tiny bit on some healthy human white blood cells, and looked to see if they could detect any DNA damage.  It was not subtle. This is what normal healthy human chromosomes look like. This is your DNA; this is DNA on guacamole. Chromosomes literally broken in half, terminal deletions, dysjunctions, translocation, all sorts of weird chromosomal abnormalities.  This is the kind of thing carcinogens do.

 Conclusion: Their study suggests that extracts of avocado fruit can potentially indusce significant genomic instability and some genetic damage in human white blood cells.

Why do they say potentially—we could see it with our own eyes. Because it was an in vitro evaluation. These were human cells, but they were outside the body. Even people that love guacamole don’t shoot it up like heroin, you eat it. So before it can affect our blood cells it hits stomach acid. Then digestive enzymes. Then our liver is a carcinogen detoxifying machine! And only then, do food compounds get to circulate throughout our body.

So, we don’t know what happens when when we eat it,  but if the same effect occurs on body cells in vivo, meaning inside the body, then it could result in loss of function, cell death or transformation into cancer.  And if it did the same thing to our sperm or eggs, it could lead to infertility, abortions, miscarriages, or birth defects.

The  bottom line we don’t know what avocado consumption can do inside the body, but until the jury is in,  I think it’s reasonable, given these new data, for people to consider  reducing their intake.

To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Dianne Moore.

To help out on the site please email volunteer@nutritionfacts.org

Dr. Michael Greger

Doctor's Note

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!

See also yesterday's "prequel" Are Avocados Good for You?

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

  • http://nutritionfacts.org/members/mgreger/ 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!

  • http://nutritionfacts.org/members/SuzanneGoldberg/ Suzanne Goldberg

    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!

    • http://nutritionfacts.org/members/mgreger/ Michael Greger M.D.

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

  • http://nutritionfacts.org/members/SuzanneGoldberg/ Suzanne Goldberg

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

  • http://nutritionfacts.org/members/tim/ 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?

  • http://nutritionfacts.org/members/louis/ Louis

    Michael Greger :”and then they took some avocado fruits, mashed it up”

    http://www.ncbi.nlm.nih.gov/pubmed/20859823
    “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 …

    • http://nutritionfacts.org/members/bpcveg/ BPC

      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!

      • http://nutritionfacts.org/members/onestaorganics/ OnestaOrganics

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

  • http://nutritionfacts.org/members/veguyan/ Veguyan

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

  • http://nutritionfacts.org/members/onestaorganics/ 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?

  • http://nutritionfacts.org/members/drsteve/ 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!

    • http://nutritionfacts.org/members/mgreger/ Michael Greger M.D.

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

  • http://nutritionfacts.org/members/yurple/ 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?

    • http://nutritionfacts.org/members/drdons/ 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.

  • http://nutritionfacts.org/members/daysleeper/ 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.

    • http://nutritionfacts.org/members/bpcveg/ BPC

      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: http://foodallergens.ifr.ac.uk/food.lasso?selected_food=4

      • 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.

  • http://nutritionfacts.org/members/bpcveg/ BPC

    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!

  • http://nutritionfacts.org/members/bgrune/ 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?

    • http://nutritionfacts.org/ Michael Greger M.D.

      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!

  • 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?

    • http://nutritionfacts.org/ Michael Greger M.D.

      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!

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