After reviewing a decade of studies on the health benefits of soy, an American Heart Association committee's findings cast doubt on the health claim that soy-based foods and supplements significantly lower cholesterol.

Because of the review results, the AHA committee said it would not recommend using isoflavone supplements in food or pills. In a statement recently published in the AHA journal Circulation, the committee concluded that foods and supplements containing soy did not significantly lower cholesterol. (See PDF of full article, scheduled for print publication on Feb. 21, 2006.)

The article gives the following background and rationale for the research review:

In October 1999, the U.S. Food and Drug Administration approved labeling for foods containing soy protein as protective against coronary heart disease. The FDA based this decision on clinical studies showing that at least 25 grams of soy protein per day lowered total and LDL cholesterol. The FDA also stated that "the evidence did not support a significant role for soy isoflavones in holesterol-lowering effects of soy protein."

In 2000, the AHA Nutrition Committee released a scientific advisory on soy protein. At that time, the conclusion was that "it is prudent to recommend including soy protein foods in a diet low in saturated fat and cholesterol."

Since then, many well-controlled studies on soy protein and soy-derived isoflavones substantially added to the knowledge base. For this reason, the AHA Nutrition Committee decided to reevaluate the evidence on soy protein and cardiovascular disease and update its scientific advisory. Thus, this scientific advisory assesses the more
recent work published on soy protein and its component

Review of studies reveals few true benefits

The committee members reviewed 22 studies and found that large amounts of dietary soy protein only reduced LDL, or "bad" cholesterol, about 3 percent and had no effect on HDL, or "good" cholesterol, or on blood pressure.

In a separate analysis of isoflavones, a review of 19 studies suggested that soy isoflavones also had no effect on lowering LDL cholesterol or other lipid risk factors.

In terms of effects on menopause symptoms and on various cancers, the article abstract said: "Soy protein and isoflavones have not been shown to lessen vasomotor symptoms of menopause, and results are mixed with regard to soy's ability to slow postmenopausal bone loss. 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."

Those reasons were cited for not recommending isoflavone supplements.

"Soy proteins and isoflavones don't have any major health benefits other than soy protein products are generally good foods," Frank Sacks, a professor of nutrition at the Harvard School of Public Health in Boston who led the AHA committee and was lead author of the review article, told the AP. "They're good to replace other foods that are high in cholesterol."

The Heart Association statement notes that many soy products should be beneficial to cardiovascular and overall health because of their high content of polyunsaturated fats, fiber, vitamins and minerals, and low content of saturated fat.

SOURCE: American Heart Association.