Pooling data from 41 clinical trials conducted between 1982 and 2004, researchers found that people who were given isolated soy protein tended to see a decline in their "bad" LDL cholesterol and triglycerides, another type of blood fat.

In a majority of the studies, however, the benefit was not statistically significant, meaning the finding could have been due to chance.

Across the studies, soy protein lowered LDL cholesterol by about 4 points, on average, the researchers report in the American Journal of Cardiology.

The findings echo those of a recent research analysis by the American Heart Association. That study concluded that isolated soy protein lowers LDL cholesterol by only a few points, and that supplements containing isoflavones -- estrogen-like compounds found in soybeans -- are ineffective.

These latest findings are generally consistent with that report, according to lead study author Dr. Kristi Reynolds of the Tulane University School of Public Health and Tropical Medicine in New Orleans.

Still, she said, while the cholesterol benefits of soy may be small, they are not insignificant.

"Even if we see just a small decline (in cholesterol)," Reynolds told Reuters Health, "that actually could have an important effect on the prevalence of high cholesterol in the general population."

The key, according to Reynolds, is to eat soy products -- like tofu, tempeh or soy nuts -- in place of foods high in cholesterol-raising saturated fat or "trans" fats.

Saturated fat is found in animal products, so replacing a hamburger with a soy burger could be a heart-healthy move. Trans fats are found in a range of processed foods, including shortening, margarine, cookies, crackers and other snack foods.

Soybeans, on the other hand, contain heart-healthy unsaturated fat, as well as fiber and other nutrients that may help lower cholesterol, Reynolds and her colleagues point out.

There's no good evidence, however, that soy isoflavone supplements help lower cholesterol, Reynolds said. It's better to save the money you'd spend on pills and use it on some tofu hot dogs, according to the researcher.

SOURCE: American Journal of Cardiology, September 2006.