Medically reviewed on June 7, 2018
What is Soy?
The soybean is an annual plant, with bean pods containing up to 4 oval, yellow to brown seeds.
Glycine max (L.) Merr.
Soybean, soya, and soy isoflavones.
What is it used for?
In 2,838 BC, Chinese emperor Shung Nang described soybeans as China's most important crop. The plant was introduced to Japan, Europe, and eventually to the US by the early 1800s. The US now produces 49% of the world's soybeans. Soy foods have become increasingly popular among health-conscious individuals since the early 1990s. In 2000, approximately 27% of US consumers reported using soy products at least once a week, nearly double the 1998 figure. As a food source, soy has been used in Asian cultures for thousands of years, with Asian populations consuming 60 to 90 g/day of soy, compared with Western diets that contain approximately one-tenth of that amount. Soybean products include milk, flour, curd, sufu, tofu, tempeh (Indonesian fermented product), miso (Japanese fermented soybean paste), sprouts, soy sauce, soybean oil, textured soy proteins (in meat extenders), soy protein drinks, and livestock feeds. Because of its low cost, good nutritional value, and versatility, soy protein is used as part of food programs in less developed countries.
Soy is commonly used as a source of fiber, protein, and minerals. A number of studies of the medical effects of soy are now available; however, evidence is lacking to support soy for menopausal symptoms, osteoporosis, diabetes, or heart disease. Disease control data suggest an association with a lower incidence of certain cancers with higher intake of soy.
What is the recommended dosage?
A large number of clinical trials have been conducted for conditions (eg, menopause, osteoporosis, breast cancer, heart/blood vessel diseases) using daily doses of soy isoflavones from 40 to 120 mg.
Contraindications have not been identified.
Generally recognized as safe (GRAS) when used as food. Avoid dosages above those found in food because safety and efficacy are unproven.
None well documented. A decrease in the blood thinning effect of warfarin has been reported in 1 patient.
Soybeans and their products are generally well tolerated. Minor GI disturbances have been reported. The National Toxicology Program (US Department of Health and Human Services) has concluded that there is minimal concern for developmental effects in infants fed soy infant formula.
Animal studies have shown adverse effects of the isoflavone genistein on the developing female reproductive tract.