In a public health study in Japan, researchers found that regular consumption of soy isoflavones could reduce the likelihood of breast cancer. The researchers at the National Cancer Center Research Institute in Tokyo followed a group of 21,852 Japanese women, aged 40 to 59, for one decade. The women documented their reproductive and family history, lifestyle habits and dietary factors, including soy intake. The researchers found that the consumption of miso soup and soy isoflavones, but not of other soy foods, was associated with a reduced risk of breast cancer. They also found this association strongest for postmenopausal women.

At the University of Messina’s School of Medicine in Italy, researchers found that genistein, a phytoestrogen found in soybeans, could benefit heart health for postmenopausal women. In a double-blind, placebo-controlled study, 79 healthy postmenopausal women were either given estrogen/progestin therapy, genestein or a placebo for one year. After the trial period, the genistein therapy improved cardiovascular health in postmenopausal women to a similar extent than the more conventional estrogen/progestin therapy.

From these and many other well-documented studies, it’s clear that people who consume soy isoflavones on a regular basis have a lower risk of breast cancer and heart disease. Nutritionist Leslie Beck, author of Leslie Beck’s 10 Steps to Healthy Eating, recommends one serving of soy per day for healthy people and up to three servings per day for people looking to reduce symptoms of menopause or to lower cholesterol. Supplements containing genestein and other soy isoflavones are an option for those who may not get adequate soy in the diet.

Sources: J Natl Cancer Inst. 2003 Jun 18;95(12);906-13; Am J Med 2003 Apr 15;114(6):470-6; 10 Steps to Healthy Eating by L Beck. Viking:2002