Eating chicken may lead to a smaller penis

Eating chicken may lead to a smaller penis

According to the best available science, three quarters of women find both penis length and girth “somewhat important” or “very important.”

What does this have to do with diet?


Phthalates are chemical compounds used in a wide range of consumer products, including pesticides, paints, and PVC plastic. The contribution of dietary intake to phthalate exposure, however, was not well defined until a landmark study was published last year in the journal of the U.S. National Institute of Environmental Health Sciences.

Phthalates had been known to affect the genital development of lab rats, but recent human studies have also shown adverse effects on sexual health and development. The most important findings to date have come from the Study for Future Families, a multicenter study of prenatal clinics in California, Minnesota, and Missouri.

It was a simple study. Researchers measured the levels of phthalates flowing through the bodies of pregnant women, and then later measured the size and characteristics of their infant sons’ genitalia between ages 2 months to 3 years. There was one phthalate particularly associated with a smaller penis, mono 2-ethylhexyl phthalate, MEHP. The team of researchers conclude: “These changes in male infants, associated with prenatal exposure to some of the same phthalate metabolites that cause similar alterations in male rodents, suggest that commonly used phthalates may undervirilize humans as well….”

So what foods should pregnant women stay away from to avoid the “phthalate-related syndrome of incomplete virilization” in their sons? In the study published last year, the urine phthalate levels of thousands of Americans all across the country were measured, along with their diets, to find out which food was most significantly associated with phthalate body burden. They looked at dairy, eggs, fish, fruit, poultry, potatoes, tomatoes, vegetables in general, and red meat.

The most statistically significant finding in their analysis was the link between poultry consumption and MEHP.

Those that reported on the Study for Future Families data implied that having a small penis size made boys “less masculine” (see video), but the link between masculine behavior and the types of phthalates found in chicken wasn’t established until last year. Researchers found that boys who were exposed did indeed exhibit less male-typical play (such as preferring trucks over dolls). In the video I also show the studies associated the contaminants found in chicken to increased odds of cesarean section, diminished child intelligence, male breast growth, and  attention-deficit and hyperactivity disorder symptoms.

Maybe the phthalates were just leaching into the meat from the plastic wrap packaging? Probably not, conclude the researchers: “the finding that egg consumption is significantly associated with levels of MEHP too, suggests that chickens themselves may be contaminated with phthalates and that food is not being contaminated just through packaging and processing.”

So to protect their sons’ normal development, pregnant women may be wise to avoid poultry. To watch this in video form, click on Chicken consumption and the feminization of male genitalia“.

-Michael Greger, M.D.

Image credit: nathanmac87 / Flickr

  • Michael Greger M.D.

    Please feel free to leave any questions you may have about this entry below, and be sure to check out today’s video-of-the-day, Chicken consumption and the feminization of male genitalia. I am indebted to Stephen Walsh (author of the fabulous Plant Based Nutrition and Health), for his time, effort, and patience working with me to improve this blog and the associated video.

  • Lachicavegana Comefrutas

    OMG. Will you please marry by beautiful Vegan Persian Girlfriend??
    I am slightly pissing my pants at this one.
    Surely a “Selling Point” of vegan men, well, if their mum’s were vegan!!

    • proudmum

      I don’t think it’s funny at all! My guess is that you don’t have children. My son had to have an operation for an undescended testical. I ate pretty healthy during my pregnancy, or at least I thought I was. This site is certainly opening my eyes, but don’t make judgements about other people. Most people just don’t know any better. Everyone always tries to blame the mothers but you should be blaming KFC and other chicken sellers.

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  • mainlinebooker

    Please don’t post items like discredits your reliablity and factual solid science

    • Michael Greger M.D.

      I don’t understand, mainlinebooker. Did you read the papers? They were both published in the prestigious peer-reviewed journal of the U.S. National Institute of Environmental Health Sciences and available free, full-text linked under “Sources” beneath the video (Chicken consumption and the feminization of male genitalia).

  • Ricki

    I just had to share this one on twitter and Facebook! A few readers are asking whether the chicken was organic or not–I couldn’t find any mention of that. Do you happen to know? Thanks!

    • Michael Greger M.D.

      Excellent question Ricki. And if it is something in the feed, that might indeed make a difference. Unfortunately the researchers lumped conventional chicken and organic poultry together so we can’t differentiate the two. I’ll make sure to update everyone if there is follow-up work done in this area, so stay tuned! You can subscribe to the combined blog and video feed by clicking this link: and follow the conversation on facebook ( or twitter ( Thank you for helping me to get this important information out there. Pregnancy is a vulnerable time for toxicant exposures and we need to protect the next generation the best we can.

  • Mike Quinoa

    Hi Dr. Greger,

    Thanks for providing the links to the pertinent studies in all your blogs. It really allows all of your readers to study the quoted research themselves. But, one question. When I click on the “three quarters” link in the article it takes me to PubMed. I’m not very familiar with the PubMed site. Is it necessary to click on a link there to get more info? Thanks.

    • Michael Greger M.D.

      Unfortunately, many academic publishers refuse to allow open public access to their journals, but one of fans posted a link to that particular article on our facebook page for your reading pleasure.

    • nosaelg

      I have found that journal articles such as this can be accessed at a public library using a library card! I can access these articles through my university’s library web page with my alumni login too. It’s a bit of a work-around, but sure beats paying.

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  • Bix

    Hi there Dr. Greger. I was wondering, in the Colacino study it says, “Vegetable consumption was also significantly associated with MEP levels, which was one of the strongest effects measured.”

    I don’t mean to detract from your message about poultry, which I think is an important one. I do wonder though about the presence of phthalate metabolites in vegetables, and how much of an impact they have. The study said they were lower molecular weight metabolites and are more water soluble. But I don’t understand the implication of that. Can you shed some light? Thank you.

    • Michael Greger M.D.

      Bix–I love you! Thank you so much actually taking the time to read the primary sources. Always linking to the primary sources is one of the many things I’m proud to say sets apart from other nutrition sites on the web.

      As you noted, it you look at the breakdown (here’s the direct link to the table) you can see that like other industrial pollutants (dioxins, PCBs, etc) there can be widespread contamination of the food supply. For example this year there were studies published measuring phthalate concentrations in both wastewater and dust. The best consumers can do is try to minimize their exposure (see for example my Industrial Pollutants in Vegans and Flame Retardant Chemical Contamination videos). And so although there are fewer such toxins in the bloodstream, fatty tissues, and breast milk of, for example, vegetarians and vegans, it doesn’t mean they’re not exposed at all. Just like there can be trace pesticide residues even on organic produce, the reason one might choose organic is to reduce one’s risk. Similarly, if one wanted to stay away from the most concentrated sources of the riskiest phthalates one would be wise to stay away from the most contaminated foods, such as chicken. I’ll address the monoethyl phthalate versus diethylhexyl phthalate issue below in Dan’s question.

      And just as a sidenote, the study didn’t actually measure what was in the foods; it went the step further and measured urine levels in people eating various foods (just because something is in a food doesn’t mean it’s absorbed, so that’s one of the reasons this was such a great study–the fact that it found its way to the kidneys means it was necessarily absorbed into the human bloodstream). And the most statistically significant association between food intake and the most concerning phthalate levels in the urine was with poultry (but as I noted in the video it’s possible this could result from the chicken plastic wrap packaging or something, but that wouldn’t explain the extraordinarily high level associated with eggs). The “p“-value <0.0001 means that the association between poultry consumption and mono-2-ethylhexyl phthalate was found to be so strong that there’s less than a 1 in 10,000 chance that it could have happened just by coincidence.

      • Bix

        Thank you for response, Dr. Greger. It does make sense to me that fat-soluble chemicals would be found in higher quantities in the fatty tissue of livestock where they bioaccumulate. I was concerned about their findings on vegetables. But, right now, I’m looking at non-animal products as, if not a non-contaminated food, at least a less-contaminated food.

        People I mention this to don’t believe it. I can’t help but think … Why wouldn’t chemicals that act as endocrine disruptors result in poor endocrine function? And that 10-fold increase in risk isn’t something to sneeze at. Smoking increases the risk for lung cancer by that much, although I know there are those who still say smoking doesn’t cause lung cancer.

  • Dan Holbert

    Bix, I see where you are coming from.

    I also had a look at the study results, as I find it important to be critical of interpretations by people who aren’t the authors of the study.

    Looking at table 6, I don’t see poultry singled out as being more strongly associated with phthalates, in general, than any of the other foods listed. The strongest correlations are for vegetables (particularly tomatoes and potatoes…too bad other veggies aren’t listed separately) and eggs.

    This article,, mentions DEHP and DBP specifically as the ones being associated with demasculinization. DBP is not listed in the table, and increased DEHP metabolite levels are associated only with poultry.

    However, MEP, which is associated strongly with several food categories (meat, tomatoes, and potatoes…you know, the “all-american” foods), is associated with increased breast cancer risk.

    The only food category in the study which seems to have any positive effect is fruit, which is correlated with a decrease in DEHP metabolites (the demasculinizing ones).

    • Michael Greger M.D.

      Dan, you are the man! Thank you for taking the time to dive into the subject. In a 4 minute video there’s only so much depth I can cover, which is why I always link to the primary literature so folks can dig as deeply as they’d like. And if you or anyone else has any questions trying to translate the technobabble please don’t hesitate to ask. For example, the alphabet soup of pthalate metabolite acronyms!

      Indeed the most concerning phthalates in terms of anti-androgen (countering male hormone) effects appear to be the DEHP metabolites (such as MECPP, MEHHP, MEHP, MEOHP) associated with poultry consumption. For example, maternal levels of DEHP metabolites were found to be most significantly associated with undermining free testerosterone levels in the umbilical cord blood of their infants. The Swan, et al. study noted by the Science Daily article “Prenatal Phthalate Exposure and Reduced Masculine Play in Boys” can be found here. Again the DEHP metabolites I talked about in the chicken and eggs/penis size video were most significantly associated with a reduction of male-typical play (for example choosing to play with Barbie rather than with toy trucks).

      • Nick

        nice study! but i wonder if turkey and birds are included in poultry, and whether this study has been replicated elsewhere around the world, and finally, which foods contain substances that can inhibit and reveres the action and symptoms of MEP.

  • C.Bill

    Smaller sausages???? NO, BALONEY.

    This problem will popup in a lot of male animals from time to time. I have found it in ponies, cattle, hogs and goats–especially hogs and goats. None of those animals ate chicken nor feeds that contained animal by-products. Neither were the animals fed feeds that were packaged with toxic material wrappings. Again, BALONEY!!!!!

    • Toxins

      It shouldn’t happen as often as it does and we have causal link.

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  • Tavores Tymes

    wooow no wonder men are not holding their own anymore..i mean this meat is eaten everyday by the blinded public

    • Darth Vegan

      yep who will never ever be vegan… go vegan! your gurl loves it.

  • ju6157

    This is plain old stupid. Im sure there are studies out there that will tell you if you eat cow dung your penis will grow ten times. there is a study out there for everything and results are what they want them to be.

    • Toxins

      If you examine the methodology and what the stats were you can come to your own conclusions. There is the classic example of the egg industry concluding that eggs do not negatively affect cholesterol. Taking a look at the study the methodology was improper. Here is a link to the video discussing it.

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  • TheEyeballKid

    Wait until the conspiracy theorists get a hold of this one. We will be seeing blogs about how the government is adding Phthalates to our food as a means of controlling population through reduced breeding capabilities.

    I’d like to see the stats on the penis size. Are we talking poultry leading to a micropenis, or women (God forbid) having to force themselves to make love to a man with an average or slightly less than average penis size?

    What other environmental or social factors were looked at during the study? Was the lifestyle of the participants scrutinized?

  • sciguybm

    I am 2 months late for this discussion however;

    I was the GM for one of the first Embryo Transplant, Artificial Insemination operations in the USA, back in the 1980s. Even though it was cattle, we were first, long before it was done on humans. We wrote the book on hormone impact on adult mammals as well as the impact those hormones had on offspring. We saw, first hand, the amount of deviation from normalcy that occurs when you add extemporaneous hormones into mammalian development.

    Today, our data still predicts what occurs in not just hormone-mimicking scenarios, like phthalates, but with actual hormone usage in humans. Having experience with in vitro with humans, IVF, we can predict, with perfection, exactly what the children will develop into.

    Having 2 cancer clinical trials running, dealing with hormonally driven cancers, we are trying to use the information we have to help those who have been affected by environmental hormones the most. However: the amount of hormone-mimicking compounds in our environment is staggering and explains, perfectly, the increases in hormone-driven cancers and gender-bending in children.

  • Willo Conner

    Well I’m too late for the discussion, though I would like to know your point Dr. Michael Greger. Does penis size really matter to ladies? I read a post here saying that big penis can be really appealing for ladies.

  • Abyss

    Awww, man are you serious? Chicken decreases your penis size now? WTF?

  • Mabeh Al-Zuq Yadeek

    No wonder I have a small penis.

  • Laura Cabrera

    How large was the study conducted with the pregnant women?