Dear Lynn:

I have heard that consuming too much soy can affect a woman's fertility. Is this correct? How much is too much? Thanks,
-- Itach

Dear Itach:

This is certainly a new one for me! However, when I started researching your question, I did find one reference which indicated that soy protein may in fact lessen fertility in SOME women. The "American Family Physician" (June 1996) stated that up to one-quarter of women with fertility problems may be helped by dietary changes. The researchers postulate that, since the phytoestrogens in soy products increase the length of the follicular phase and lead to fewer menstrual cycles over a woman's lifetime, it is possible that soy may decrease fertility in some women. They believe that women with multiple risk factors for infertility may be more sensitive to soy than others.

I wasn't able to find any actual studies that looked at this particular problem. It does seem strange that in countries where soy products are consumed in large amounts, the birth rate is no lower than in countries where soy is not routinely consumed. I also haven't seen any reports that vegetarian women, who are more likely to consume soy products, experience disproportionate fertility problems.

At any rate, if you are experiencing fertility problems, it certainly won't hurt to limit soy in your diet. Since it's the protein portion of soy that contains the phytoestrogens, you might want to avoid tofu, soy milk, tempeh, TVP and soy nuts. Soy sauce does not contain phytoestrogens, so you can continue using this to flavor foods.

Sincerely,
Lynn Grieger, R.D., C.D., C.D.E.

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