Researchers from the University of Southern California report the outcome of a double-blinded trial of postmenopausal women which found a protective effect for soy protein supplementation against the progression of atherosclerosis if initiated within five years of menopause. The findings appeared online on September 8, 2011 in the American Heart Association journal Stroke.
Howard N. Hodis, MD of USC’s Keck School of Medicine and his associates randomized 350 postmenopausal women aged 45 to 92 who did not have cardiovascular disease or diabetes to receive 25 grams isolated soy protein per day or a placebo for 2.7 years, during which carotid artery intima-media thickness was monitored. Although carotid artery intima-media thickness progression averaged 16 percent less in women who received soy protein compared to those who received a placebo, the effect was not considered significant. However, when the participants were analyzed by age group, a significant protective effect was observed among those who were within five years of menopause, with those who received soy protein having an average rate of progression that was 68 percent lower than those who received a placebo.
This trial is the largest and longest randomized controlled human study so far to evaluate isolated soy protein’s effect on atherosclerosis progression. In addition to retarding atherosclerosis, the researchers also observed a significant increase in high density lipoprotein (HDL) cholesterol among women who received soy protein, which is associated with a protective effect on the cardiovascular system.
“These results are consistent with what we have learned through research conducted over the past decade,” Dr Hodis stated. “The literature demonstrates that there is a ‘window of opportunity’ of a potential beneficial effect on coronary heart disease for products that bind to the estrogen receptor including hormone-replacement therapy, soybean isoflavones or selective estrogen receptor modulators (SERMs) when initiated in women within 5-6 years of menopause.”