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Soy Hormones & Male Infertility

The phytoestrogens in soy appear to protect against cancer, but might they reduce male fertility?

November 27, 2009 |
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Supplementary Info

Sources Cited


Image thanks to brownpau.


What about soybeans, though? The phytoestrogens in soy protect against cancer, but might they decrease male fertility? Fox News thinks so.
Fact, or fiction? Are you sure—they say they’re fair and balanced.
Fiction, and it’s interesting why. The study did find that soy decreased sperm concentration, but did not significantly affect sperm count. How can you have the same number of sperm, but a lower concentration? Because of larger ejaculate volume. Soy appears to stimulate the prostate gland to produce a larger load of ejaculate fluid, but the actual overall sperm count remains the same.

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 veganmontreal.

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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. Also, there are 1,449 other subjects covered in the rest of my videos--please feel free to explore them as well!

  • Adam Rodriguez

    I want to ask if it’s true that soy makes men more feminine because of the phytoestrogen?

  • Eric Needs

    Seems like a win-win to me! However I’ve heard that soy can supress the thyroid. Is there an upper limit?

    • Michael Greger M.D.

      Excellent question! Soy does indeed have so-called “goitrogenic” compounds (as does broccoli-family vegetables and flax seeds), which can interfere with thyroid function in people with marginal iodine intake. The answer is not to avoid these super healthy foods but to just make sure you get enough iodine. See my video Avoiding Iodine Deficiency.

  • tmehta

    Dear Michael!

    I love this website and want to congratulate you on the amazing work you do!

    Quick comment – the paper by Chavarro states that there was lower sperm concentration among men who consumed soy, but that the ejaculate volume was the SAME. The paper suggests that those eating soy had lower sperm counts.

    The abstract of the article that you referenced suggests that there was no effect on ejaculate volume. Also, in the video, the table you show does suggest a trend of decreasing sperm counts. I wonder if it is clinically relevant though?

    Cheers and Thanks!

    • Michael Greger M.D.

      If you look at table II (I love open access articles! :) you can see although they find an significant difference in sperm concentration (middle column down at the bottom), since there’s a trend towards larger ejaculate volume (second column down at the bottom) you can see that the statistically significant correlation between soy and sperm vanishes (P for trend = 0.65; bottom of first column in table). Thanks so much for leaving a comment!

  • Sean_Conley

    Hi Dr. Greger,

    I have a question along this topic.  Can you summarize any available information on how plant-based diets may affect one’s libido?  Does libido generally increase, decrease, or stay the same on a plant-based diet and do certain foods swing it either way?  Thanks for all the great info here and keep up the good work!

  • Belle

    Dr. Gregson…what about soy protein isolate and gmo soy?

  • Karen

    so eating soy gives sperm more wiggle room!

  • Amit

    I have Acute lymphoblastic Leukamia , can I drink soya milk? is it bacteria free?

  • Jack

    please, (Q. 1)does soy milk or soy products consumption significantly reduces the chances of a wife becoming pregnant? or should a woman expecting to become pregnant avoid soy milk / soy products?
    (Q.2) Does intake of soy milk or its products reduces sperm count?

  • Jack

    can the daily intake of soy milk or its products lead to miscarriage and at what stage of the pregnancy

  • Jack

    Please, are there some food / processed food that can promote miscarriage during pregnancy that one has to avoid? If yes please kindly list them. thanks.