How does soy affect fertility?
Soy and Estrogen
Soy is an excellent source of protein and the female reproductive hormone estrogen. Soy foods contain phytoestrogens, literally meaning plant-derived estrogen. The type of phytoestrogen in soy is known as isoflavones. These isoflavones come in different forms and have different effects. Some may function similarly to estrogens in the body, producing a very weak effect compared to the real hormone. And others act as antiestrogens, to reduce the activity of estrogen. Evidence is growing that these phytoestrogens may help with menopausal symptoms, as well as inhibits cancer cell growth.
Soy and its Effect on Fertility
There are not many studies done in this field, however some reports suggest 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.
A few studies suggest that high levels of soy protein may decrease fertility. According to a report in The American Journal of Clinical Nutrition a small number of studies have shown that high levels of soy can increase menstrual cycle length, decrease FSH (follicle-stimulating hormone) and decrease LH (leutinizing hormone). But we must note that the high levels of soy generating this effect are equivalent to drinking three 12-ounce glasses of soy milk (60 g soy protein equivalent to 45 mg of isoflavones) a day for a month. However, normally most people do not consume this much soy.
The American Family Physician magazine stated that up to one-quarter of women with fertility problems may be helped by dietary changes. The researchers state 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. But they also add here that women with multiple risk factors for infertility may be more sensitive to soy than others.
Some studies on various animal species have also indicated that eating high levels of phytoestrogens from soy can have adverse effects on fertility. But there is no current data to suggest that consumption of phytoestrogens at the levels normally encountered in the diet of animals in these tests or humans in general are likely to be harmful.
A more recent review reported in The American Journal of Clinical Nutrition sates that reproductive and developmental toxicity studies did not find significant variations in fertility from soy phytoestrogens consumption in healthy couples, indicating that normal intake of soy is basically harmless to your fertility and hence your chances of becoming pregnant or maintaining a pregnancy.
If for any reason you are experiencing fertility problems, it certainly is a good idea to limit soy in your diet to rule out any possibilities of its effect on your fertility. Since it’s the protein portion of soy that contains the phytoestrogens, you should try to avoid tofu, soy milk, tempeh, TVP and soy nuts. Soy sauce does not contain phytoestrogens, and so you can continue using this to flavor foods. As with any food, it is wise not to overconsume. Eating soy in moderation allows you to avoid any potential harm due to overconsumption, as well as leaves more scope for a variety in your diet which helps you are to get all the important nutrients that your body needs.