The soy plant Glycine max has a long history of consumption in Asiatic societies. According to the Mayo Clinic, soy products have been a dietary staple in Asia for at least 5,000 years. The Linus Pauling Institute notes that breast cancer incidence and hip fracture in postmenopausal women are lower in Asiatic women who eat a traditional diet with regular soy consumption.
What are Phytoestrogens?
Soy belongs to a class of plants known for phytoestrogen effects, meaning plants that behave like estrogen in the human body. The isoflavones in soy are the primary substances that have been found to have weak estrogen-like activity. The hormone estrogen, one of the primary female hormones, is actually present in both men and women. In addition to its effects on reproduction, the body has estrogen effects in bone, liver, heart and brain. Soy isoflavones are able to bind with these receptors, mimicking the effects or natural estrogen in some cases, and antagonizing or blocking the effects in other situations.
Soy Food Products
Soy is used in a wide array of food products. In addition to the actual soybean, known as edamame and eaten in the green phase, soy products in Western countries may include meat substitutes, soy milk, soy cheese and yogurt. Tofu, a product made from soy beans, was invented in China. High in protein and calcium, tofu is found in many processed foods like veggie burgers, energy bars, and desserts like soy ice creams. Traditional Asian foods made from soybeans also include tempeh, miso, and natto.
Research on Soy and Estrogen
The Linus Pauling institute notes there is considerable scientific research focused on soy isoflavones and their effect on estrogens and estrogen receptors, because the soy may help reduce the risk of hormone-associated cancers like breast cancers. However, the estrogen-blocking effects of soy could also help maintain bone density and improve cholesterol. One study on prostate cancer, reported by C. Nagata, et. al. in the December 2000 "Cancer Epidemiology, Biomarkers and Prevention", compared men who had been assigned to a group drinking soy milk and one that did not. The authors noted that serum estrone, one of the hormones measured, did increase in the group drinking soy milk, and that in a previous study they had conducted, premenopausal women who drank soy milk decreased another estrogen-related hormone called estradiol.
Considerations and Warnings
In Asian societies soy is most often consumed in fermented products such as tempeh, miso and tamari soy sauce. However, Walter C. Willett, M.D., Dr.P.H., of the Harvard School of Public Health notes that while people have been consuming soy for many centuries, where soy milk is concerned, even though the risk involved in seems low, children should limit soy milk to one or two glasses a day.
References
- "Cancer Epidemiology, Biomarkers and Prevention"; Effect of Soymilk Consumption on Serum Estrogen and Androgen Concentrations in Japanese Men; C. Nagata, et. al.; December 2000
- Harvard Medical School; Harvard Health Newsletter; By the Way, Doctor: Children and Soy Milk; Walter C. Willett, M.D., Dr.P.H.; May 2009
- Mayo Clinic.com;Soy (Glycine max); April 2011
- Linus Pauling Institute; Micronutrient Information Center; Soy Isoflavones; Jane Higdon, Ph.D., et. al.; December 2009
Member Comments