Soy foods may offer special benefits for the hearts and bones of premenopausal women, suggest two studies conducted at Wake Forest University Baptist Medical Center and presented at the 2004 annual meeting of the North American Menopause Society, Washington, D.C. The results of these studies indicate a beneficial synergy between isoflavones, the weakly estrogenic compounds in soy, and the body's own estrogen in decreasing cholesterol and increasing bone mass.
In the first study, cholesterol levels in laboratory animals fed a soy-based diet were improved compared to those of monkeys given a diet of milk and animal protein¡ªand the most improvement occurred in those animals at highest risk for heart vessel disease. A low ratio of total cholesterol to HDL (good) cholesterol is considered healthier. In animals at highest risk for heart disease, the cholesterol ratio decreased by 48% in those given soy compared to those receiving milk and animal protein. Even in the animals at low risk for atherosclerosis that ate soy, the cholesterol ratio dropped 33%.
Lead researcher in this study, Jay Kaplan, PhD, noted that a 48% drop in the cholesterol ratio would likely equate to a 50% reduction in the size of plaques in the arteries, which can rupture causing heart attacks and strokes.
In the second study, animals eating soy were found to have an increase in bone mass compared to those not given soy. According to lead researcher in this study, Cynthia Lees, D.V.M., Ph.D., "The increase was small, but this suggests the possibility that if women consumed soy on a regular basis before menopause, it could benefit their health after menopause." Kaplan also noted that because the soy-estrogen combination caused improvements in both cholesterol and bone, it might also positively impact other areas of the body affected by estrogen, including the brain.
Next on the researchers' agenda will be a study using lower levels of isoflavones over a longer period of time to see if this will be as effective-an outcome that appears to already be supported in a human trial published in the American Journal of Clinical Nutrition.
In this study, which included over 1000 pre- and postmenopausal women (meat-eaters, vegetarians, and vegans), eating moderate amounts of soy foods as part of a regular diet was associated with a lower ratio of total to LDL cholesterol, but not with a lowering in the level of beneficial HDL cholesterol. In those women eating 6 or more grams of soy protein daily, blood levels of LDL cholesterol were 12.4% lower than those in women who ate less than 0.5 grams of soy protein daily.