BIRMINGHAM, Ala.—Soy supplementation reduced abdominal fat in obese postmenopausal women, but the effects were different for Caucasians and African Americans, according to a study published in the online version of American Journal of Obstetrics & Gynecology (2010 Apr 30). Caucasian women primarily lost subcutaneous (around the middle section) and total abdominal fat, and African American women primarily lost total body fat.
Researchers at the Department of Obstetrics and Gynecology at the University of Alabama School of Medicine sought to determine the effect of daily soy supplementation on abdominal fat, glucose metabolism, and circulating inflammatory markers and adipokines in obese, postmenopausal Caucasian and African American women.
In a double blind, controlled trial, 39 postmenopausal women were randomized to soy supplementation or to a casein placebo without isoflavones. A Reuters article reported 16 African-American women and 17 white women received either soy-stuffed shakes, which included 20 g of soy protein and 160 mg of soy isoflavones, or placebo shakes containing a milk protein called casein. In all, 33 completed the study and were analyzed. At baseline and at 3 months, glucose disposal and insulin secretion were measured using hyperglycemic clamps; body composition and body fat distribution were measured by computed tomographic scan and dual energy x-ray absorptiometry; and serum levels of C-reactive protein, interleukin-6, tumor necrosis factor-α, leptin and adiponectin were measured by immunoassay.
Soy supplementation reduced total and subcutaneous abdominal fat and interleukin-6. No difference between groups was noted for glucose metabolism, C-reactive protein, tumor necrosis factor-α, leptin, or adiponectin. Reuters reported X-rays found no difference in total body fat percentage between the soy and placebo groups, but computerized tomography (CT) scans found a 7.5-percent less abdominal fat in women given soy, compared to 9-percent more of such fat in the placebo group.
Reuters also noted Black women taking soy lost an average of 1.8 kilograms, or 4 pounds, but gained visceral fat (fat surrounding the organs) in the abdominal cavity. The article said whites given soy put on 0.8 kilograms, but lost visceral fat in the abdomen.
