The researchers said several good studies are under way that may show whether some products work, but they are years away from reporting any results.

Leading botanical researchers, meeting under the auspices of the National Heart, Lung and Blood Institute, said products vary greatly in what they contain and some may not even be in a form that the body can use.

"The available clinical trial results are not adequate to answer important questions about the potential cardiovascular benefits of garlic,'' said Christopher Gardner, director of nutrition studies at the Stanford Center for Research in Disease Prevention. .

For instance, said Eric Block of the State University of New York in Albany, stomach acid and heat may destroy some of the active ingredients in garlic. Like all plants, garlic varies greatly from crop to crop in its makeup.

As for soy, some studies suggest that it can lower blood pressure and perhaps cholesterol as well. But the products also vary, and studies have not consistently compared the same products.