soyThat is a question I get almost weekly in my practice. The confusion is understandable, partly because the media keeps feeding us mixed messages, and because soy has a very interesting effect on the body that takes a little bit of time to understand.

Several years ago foods containing soy were all the rage as a healthy way to reduce cholesterol and improve overall diet. A few years after that, soy got a bad reputation because we found out that soy contains estrogen and many people became concerned about the potential risk of breast cancer from consuming too much estrogen from soy. Much of this concern was extrapolated from the knowledge we gained from the Women’s Health Initiative study which suggested that estrogen replacement therapy in menopause was associated with higher rates of breast cancer. Many parents of young boys in my practice even became concerned about giving their sons tofu and soy milk, and lots of grown men in my practice completely refuse to eat foods like tofu for fear that the estrogen in soy will make them more feminine.

So lets clear up the confusion once and for all! Soy based foods like firm tofu, tempeh, soy milk, and edamame are a great source of nutrients like calcium, protein, and in some cases fiber. The less processed the food, the higher the nutrient content will be. For example, edamame, which is just unprocessed soy beans, is extremely high in fiber, while soy milk has almost no fiber in it. As a rule, it is important to emphasize whole, unprocessed foods in the diet and limit intake of processed foods. When people ask me whether they should eat tofu or not, I generally say, “Yes, but be sure to buy firm tofu which has more valuable nutrients in it, buy organic tofu, and make sure you are eating other, less processed soy based foods as well, like tempeh and edamame.”

Soy does indeed contain plant estrogens or phytoestrogens which, when consumed, illicit a weak estrogenic effect on the body. Phytoestrogens tend to have an effect that is up to 1000 times weaker than that of the estrogen found in harmful synthetic chemicals and of the estrogen produced in our own bodies – and yes, normal healthy males also produce a certain amount of estrogen. Phytoestrogens, our body’s own estrogen, and other synthetic estrogens we’ve been exposed to all compete for the same estrogen receptor sites on and in our cells. When estrogen binds to a receptor, whether it is a weak or a strong acting form of estrogen, it creates an effect on the body. The more phytoestrogens in our system, the weaker overall estrogenic effect we have on the body, because less of the “strong” estrogens are able to bind to their receptors. So, for individuals who have symptoms related to estrogen dominance like painful periods, fibroids, and prostate enlargement; consuming foods high in phytoestrogens can be beneficial.

Here’s where things get even more complicated. Women in menopause are actually experiencing an estrogen deficiency – the opposite of estrogen dominance. These women have estrogen receptors with not enough estrogen to bind to them – their estrogen receptors are wide open. For these patients, consuming phytoestrogens, like soy-based foods, actually improves their symptoms by increasing their body’s overall estrogenic effect. The weak phytoestrogens bind to estrogen receptors that would have been left empty. Because soy does contain estrogen, and we know that estrogen can sometimes stimulate certain types of cancer cells, it is important for women with estrogen receptor positive breast cancer to talk to a knowledgeable professional about whether or not to consume soy – the answer will depend on the exact type of breast cancer they have, the current medication they are taking, and their stage of treatment.

Women looking to prevent breast cancer and promote overall hormone balance will actually benefit from consuming unprocessed soy based foods on a regular basis. Consumption of soy has been shown to have a positive effect on cardiovascular health, bone density, and menopausal symptoms.