For years, women experiencing the unpleasant effects of hot flashes may have felt frustration from conflicting news stories about whether soy may be of benefit. Perhaps due to small sample sizes and inconsistent study methodology, results often varied. However, a new large-scale statistical analysis, published in Menopause: The Journal of the North American Menopause Association, offers clear and compelling evidence from a review of 19 studies examining more than 1,000 women. The conclusion: soy isoflavones reduce menopausal hot flash frequency and severity by approximately 50 percent. The results were highly statistically significant. Soy isoflavones, although different from the hormone estrogen, are plant compounds that exert a mild estrogen-like effect in certain conditions.
Authors – Kyoko Taku, PhD, MD, National Institute of Health and Nutrition, Japan; Melissa K. Melby, PhD, University of Delaware; Fredi Kronenberg, PhD, Stanford University; Mindy S. Kurzer, PhD, University of Minnesota; and Mark Messina, PhD, Loma Linda University – reviewed research that included 1,200 women in studies evaluating frequency and 1,000 women in those evaluating severity. On average, studies provided participants with 54 mg of soy isoflavones daily for six weeks to a year.
In addition, the analysis assessed whether isoflavone products with higher genistein, one of the two primary types of soy isoflavones, are more effective than those with lower amounts. Dr. Melissa Melby commented, "Our analysis found isoflavone supplements containing at least 18.8 mg of genistein were more than twice as effective at reducing frequency than lower amounts."
During menopause, hot flashes can persist for an extended period of time and can interfere with daily activities and sleep. Hormone therapy (HT) containing estrogens or a combination of estrogens and progestins used to be a standard choice for alleviating hot flashes, but safety concerns led to recommendations that HT treatment be taken at the lowest doses for the shortest period of time. The benefits observed in the newly published meta-analysis make isoflavones an effective option for women who don't want to take HT. A small survey also published in Menopause found that 70 percent of women seeking a non-hormonal treatment for hot flashes would be satisfied with an approach that provides at least a 50 percent reduction in symptoms.
Lisa Kelly, a registered dietitian for the United Soybean Board, added, "While this study used soy supplements, many women prefer to eat soyfoods. Traditional options, such as soymilk, tofu and tempeh, are a significant dietary source of isoflavones." Each gram of soy protein in soybeans and traditional soyfoods provides approximately 3.5 mg of isoflavones, so a full serving yields about 25 mg. For more information on soy's health benefits and recipes, visit SoyConnection.com.
As a final note, menopausal women concerned about breast cancer may be relieved to know that clinical evidence indicates soyfoods and soy isoflavones do not harmfully affect breast tissue and epidemiologic evidence indicates soy consumption improves the prognosis of breast cancer patients. And, for their daughters, another meta-analysis found an association between consuming soy starting in the childhood or adolescent years and decreased risk of breast cancer later in life.
The 69 farmer-directors of USB oversee the investments of the soy checkoff to maximize profit opportunities for all U.S. soybean farmers. These volunteers invest and leverage checkoff funds to increase the value of U.S. soy meal and oil, to ensure U.S. soybean farmers and their customers have the freedom and infrastructure to operate, and to meet the needs of U.S. soy's customers. As stipulated in the federal Soybean Promotion, Research and Consumer Information Act, the USDA Agricultural Marketing Service has oversight responsibilities for USB and the soy checkoff. For more information, please visit UnitedSoybean.org and SoyConnection.com.