Many soy food products carry health claims stating that they reduce the risk of heart disease. A review of the evidence, however, suggests that soy's cardiovascular benefits may have been overestimated by the early studies that formed the basis for its health claim.
According to the Nutrition Committee of the American Heart Association (AHA), recent clinical trials have failed to confirm that soy protein has clinically important favorable effects on cardiovascular health. Committee Chair Alice H. Lichtenstein, DSc, who is also Stanley N. Gershoff Professor of Nutrition Science and Policy at the Friedman School of Nutrition Science and Policy at Tufts University, co-authored the updated scientific advisory report just published in Circulation.
"A very large amount of soy protein, more than half the daily protein intake, may lower [bad] LDL cholesterol by a few percentage points when it replaces dairy protein or a mixture of animal proteins. However, this is not the normal level that people in this country consume. The evidence is less favorable for soy isoflavones as the responsible component," said Lichtenstein. In addition, "no benefit is evident on [good] HDL cholesterol, triglycerides, lipoprotein(a), or blood pressure."
"The efficacy and safety of soy isoflavones for preventing or treating cancer of the breast, endometrium, and prostate are not established; evidence from clinical trials is meager and cautionary with regard to a possible adverse effect. For this reason, use of isoflavone supplements in food or pills is not recommended," the authors say.