Does Soy Affect Fertility, Endometriosis, and Cancer?
Soy is a confusing category of food, one which frequently sparks passionate inquiry. In the past week, a friend revealed she’d had hormonally driven breast cancer. She came to me confused and wondering if she should be eating soy. Yet a client, also with breast cancer, has eliminated soy from her diet understanding that in small amounts, soy could, in fact, be beneficial to her diet and condition. Sometimes she wonders if she is doing the right thing. Another friend battles endometriosis and though she loves tofu, she eats it minimally because she fears it could exacerbate her condition.
While many believe soy foods to be associated with estrogen-related illnesses (infertility endometriosis, and some cancers), scientific research does not wholly support these claims. Some studies even point to soy as being preventative against these hormonally driven diseases. Although soy contains phytoestrogens (substances that can act like estrogen), which could elevate the estrogen environment in one’s body, these compounds can also do the opposite. For instance, if phytoestrogens bind to estrogen receptors first, then estrogen can’t bind to them. Because phytoestrogens are weaker than estrogen, estrogen levels would thus be lower. In addition, when phytoestrogens are in the body, they send signals to the brain indicating that estrogen is high, which the body then responds to by shutting down the production of estrogen, creating a negative feedback loop. This means that for any individual with estrogen-related issues from fertility to endometriosis and cancer, while soy could affect these conditions, it’s rare that it in fact does.
Does Soy Affect Fertility?
The answer is probably not. Studies show that you’d have to consume more than 100mg of isoflavones before you need to worry about infertility. That translates to over four cups of soy a day and that’s a lot! Consider the following: In Asian countries, where soy has been shown to have little or no effect on hormones and fertility, people consume on average ten times more soy than the most Americans, which is only about one cup of soy a day.
Soy and Endometriosis
Women who suffer from endometriosis often overproduce estrogen to begin with; since phytoestrogens can bind to estrogen receptors, the assumption is that they could signal the body to elevate estrogen levels even further, which in turn could thicken the uterus, thereby exacerbating the condition. However, while an association between phytoestrogens and endometriosis is not yet conclusive, many studies, in fact, already indicate the opposite effect of phytoestrogens on endometriosis. These studies show that because phytoestrogens can prevent actual estrogen from binding to receptors in high-estrogen environments (recall phytoestrogens bind first), they could in fact have anti-estrogenic effects, thereby reducing the risk of endometriosis. The evidence of soy’s effect on endometriosis is inconclusive and highly dependent on individual genetics, age, metabolism, gut microflora, antibiotic use, underlying conditions, environment (variety, harvest, food processing, cooking, and growth locations of foods), and how much soy one consumes.
Soy and Cancer
According to Dana-Farber Cancer Institute, it is safe to consume soy foods even if you have breast, prostate, or colon cancer. Though any cancer treatment plan will be personalized for the patient in consultation with his or her doctors, the evidence to date suggests that moderate intake of soy does not promote cancer growth.
So, Should You Eat Soy?
Bottom line: Soy is extremely nutritious and has many health benefits, so while the research in inconclusive for its overall effect in people with certain medical conditions, those without those underlying health concerns can and should enjoy it in all forms. It’s high in protein, fiber, polyunsaturated fat, and many vitamins and minerals including B vitamins, calcium, iron, and zinc. It is also cholesterol-free and low in saturated fat. I love soy and eat it many times a week in the form of tofu, tempeh, and edamame.