Soy unfairly gets a bad rap, for the following reasons:
• People hear that it contains phytoestrogens (phyto comes from the Greek word for plant, phyton), and assume that — like estrogen pills — these phytoestrogens can cause harm.
• Some soy is genetically modified to be “Roundup ready.” We’re not sure that genetically modified food itself is safe for human consumption, plus it is more apt to contain pesticides and other environmental toxins that have been proven to cause health problems.
• A large percentage of soy is grown as feed for livestock, resulting in deforestation and other environmental degradation.
• Fake meat is often soy-based. Although it is better for the environment to eat fake meat than real meat, it often contains high levels of salt and other unhealthy ingredients.
We know from the Women’s Health Initiative Study that post-menopausal estrogen replacement medications relieve menopausal symptoms and improve bone health, but are associated with an increased risk of heart attacks, strokes, cancer of the uterus and ovary, and blood clots. Soy contains phytoestrogens called isoflavones, with chemical structure close to — although not exactly like — human estrogen. People who eat soy regularly, such as those in Asian countries, have a lower risk of menopausal symptoms, bone loss, fractures, breast cancer, and cancer of the uterus and ovary.
How can soy phytoestrogens cause the beneficial effects of estrogen without causing the harmful effects? The answer is rather complicated but has to do with the following:
• Phytoestrogens are relatively weak estrogens, and when they attach to estrogen receptors in, say, breast tissue, they displace the stronger, harmful human estrogens, resulting in a lower risk of breast cancer.
• There are two types of human estrogen receptors: 1) alpha receptors, for which human and pharmaceutical estrogens have an affinity and which are the main receptors in the liver and uterus; and 2) beta receptors, for which phytoestrogens have an affinity, and are the main receptors in bone tissue.
Following are examples of how this works in the human body:
• Estrogen pills increase the risk of blood clots because they attach to alpha estrogen receptors in the liver, causing the liver to produce extra clotting factors, increasing the risk of blood clots, heart attacks and strokes. Soy phytoestrogens don’t do this because they only attach to beta receptors, which are not present in our livers.
• The uterus contains only alpha receptors — human and pharmaceutical estrogens attach to these, raising the risk of cancer of the uterus. Soy doesn’t adversely affect the uterus because it doesn’t attach to alpha receptors.
• Bone contains primarily beta receptors, to which human, pharmaceutical and soy phytoestrogens attach, so all three improve bone health.
Part of eating an optimal diet is to avoid processed food. When it comes to soy, soybeans (edamame) and tempeh (fermented soybeans) are unprocessed. Miso and tofu are minimally processed, soymilk somewhat more so.
In conclusion, don’t be afraid to eat non-GMO, minimally processed or unprocessed soy products in moderation, but avoid soy products sold as “fake meat.” What is considered moderation? In his book “How Not to Die,” legumes (beans, lentils, chick peas, split peas) are one of his daily dozen — things we should be eating every day. If soy is your chosen legume for the day, Dr. Greger would recommend three servings a day, one serving being ½ cup of edamame or tempeh or tofu.
What if you’re a woman with a history of breast cancer? Dr. Greger writes that “overall, researchers have found that women diagnosed with breast cancer who ate the most soy lived significantly longer and had a significantly lower risk of breast cancer recurrence than those who ate less.” This applied to women with estrogen-receptor positive and estrogen-receptor negative breast cancer, as well as women with the BRACA 1 or BRACA 2 mutation. Men who eat soy have a lower risk of prostate cancer.
Greg Feinsinger, M.D. is a retired family physician who has a nonprofit: Prevention and Treatment of Disease Through Nutrition. He gives a free presentation at 7 p.m. the first Monday of the month at the Third Street Center in Carbondale; is available by appointment for free consultations (379-5718); and conducts a shop-with-a-doc session at 10 a.m. the first Saturday of the month at Carbondale City Market.
