The claim: Soy can lower cholesterol.

The facts: Soy foods have been credited with all sorts of health benefits, but perhaps none so appealing as this assertion.

The notion was cemented in 1999, when the Food and Drug Administration allowed companies to claim that 25 grams of soy protein a day, in a diet low in saturated fat and cholesterol, “may reduce the risk of heart disease.” The agency evaluated studies — including an industry-financed analysis published in The New England Journal of Medicine in 1995 — concluding that soy protein could cut cholesterol.

But studies since have raised doubts. In 2006, an American Heart Association advisory panel reviewed a decade of studies and determined that soy products had no significant effects on HDL (“good” cholesterol) or triglycerides, and little or no ability to lower “bad” cholesterol, or LDL. Another study, published in August in The American Journal of Clinical Nutrition, found that consuming 24 grams of soy protein daily had no “significant effect on plasma LDL” in people with mildly elevated cholesterol.

Another line of research shows that soy seems to help when combined with foods low in fat and high in fiber and the compounds called plant sterols — in other words, an overall healthy diet.

The bottom line: There is evidence that soy can improve cholesterol, but the jury is still out.