Michael Greger MD

Michael Greger MD

Posted September 15, 2011

Published in Health

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Eating chicken may lead to a smaller penis

Read More: chicken, eggs, genitalia, phthalates, poultry, pregnancy, sexual health

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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 studywas 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. The women who had the most phthalate exposure had up to 10 times the odds of giving birth to sons with one or both testicles incompletely descended, their scrotum categorized as small and/or "not distinct from surrounding tissue," and a significantly smaller penile volume, a measure of penis size taking into account both length and girth. In other words, the more phthalates pregnant women are exposed to, the "increased likelihood of testicular maldescent, a small and indistinct scrotum, and smaller penis size."

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 studypublished 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 significant result in their analysis was poultry consumption. The data suggested "that an increase of one ounce of poultry per day is associated with an increase in [phthalate] DHEP levels of approximately 5.7 percent." A single chicken breast can be half a dozen ounces or more.

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 MHEP [phthalates] 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.

-Michael Greger, M.D.

This was a loose transcript of today's video-of-the-day "Chicken consumption and the feminization of male genitalia," reposted from