Doctor's Note

Also check out this video on prostate health and plant-based diets: Prostate vs. Plants.

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  • Adam Rodriguez

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

    • Michael Greger M.D.
      • Amo

        what about this study:

        I provide to reintroduce soy (tofu form) in my diet, is a LH /FSH, Free test, total test and oestradiol sufficient to determine if soy is not harmfull for me?

        Thanks in advance

        • Nalani

          That isn’t a study so much as it is a more heavily examined anecdotal case of a single individual. Anecdotes can lead to interesting factors got be investigated in later studies but do not definitively prove anything.

          HOWEVER, its pretty obvious what the issue is here in this specific case- the paper says up front that the patient was eating large amounts of soy, some of it was in the form of junk food (crisps) which doesn’t help. The way they make it sound its as if he was practically eating nothing but soy based products which isn’t the way to be eating anything. Apparently he was eating an upwards of 300 mg of isoflavones a day? A single serving of tofu only contains 22.70 mg

          Soy has a protective effect when consumed because the phytoestrogens not only bind to different estrogen receptors than the ones that are linked to cancers, but also they are weaker than the actual estrogens that the body produces. That protective effect is negated if you eat enough phytoestrogens to basically make up for its ‘weaker effect’.

          Greger himself suggests not to eat more than 3-5 servings daily

          stick to 1-3 servings a day and you’re fine.

  • 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!

    • Andrew Kosta

      Indeed! More wiggle room for sperm is always a great thing

  • 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.

  • Andressa Cordeiro

    Afinal! a soja pode ou não causar algum tipo de dano na fertilidade masculina? Ou ainda pode elevar os níveis de estogênio em homens?

  • Jeremy

    Could you comment on this article? it states that the sperm of vegans has lower motility compared to meat eaters.

  • Kristin

    Hi Dr. Greger. A friend of mine recently turned down edamame at a dinner outing because she’s trying to get pregnant. You have several videos on your site about male fertility and diet but none about female fertility (that I could find). What is the effect of soy on female fertility? How does it compare to the effect of dairy? Thanks!

    • Andrew Kosta


  • Jan

    Hi. Does eating soy have a negative effect on young boys’ development?

    • Cody

      Hi Jan. I am a volunteer for Dr. Greger. Your question is an interesting one, and one that there is a lot of concern about. However, the nutritional literature does not show a negative effect on young children’s development, including boys. See here an answer to your question by Dr. Walter Willett, one of the leading researchers at Harvard University:

    • Andrew Kosta

      No, however cows milk, all meat, dairy products are known to stunt anyone’s growth…

  • Sander Markiet

    Hi there,

    Thank you for this interesting video. Do you have any information on if flaxseeds and there level of Phytoestrogens (18x times higher than tofu) has a negative hormonal effect on men?

    Level of phytoestrogens:
    ¼ cup flaxseeds = 163,133.6 µg

    ¼ cup tofu = 8,688.0 µg

    • Cody

      Hi there Sander, I am a volunteer for Dr. Greger. There is currently no evidence (that I am aware of) suggesting that flaxseeds provide levels of phytoestrogens that would have negative impacts on men (or women). In fact, flaxseeds have been shown to prevent prostate cancer in men, along with other benefits. I encourage you to search “flax” in the search bar on There are quite a few videos regarding the benefits of flaxseeds, with no known drawbacks to date. Here’s just one of the videos, which is on flaxseeds and prostate cancer: