Soy: The New Superfood?
The Great Diet Debate
Soy is a lean plant protein that's packed with vitamins and fiber and has zero cholesterol and minimal saturated fat. However, our understanding about what it is about soy that makes it so healthy is still evolving. At first, some scientists suspected soy's cholesterol-lowering effect was in part due to its high levels of isoflavones, a collection of plant chemicals with weak estrogen-like characteristics. But now, scientists believe that isoflavones do not play a role in lowering LDL and triglycerides. Instead, it seems that the soy protein by itself may play a small role in lowering cholesterol.
Small, however, may be the operative word. Now some scientists are questioning whether soy reduces cholesterol to any significant degree, or whether people who eat a diet rich in soy foods simply eat less of other cholesterol-laden foods that would otherwise raise LDL cholesterol and contribute to cardiovascular disease. Several important studies in the past two years have shown only a very tenuous link between soy and cholesterol reduction. "The bottom line is that there's really no proof that soy protein lowers LDL cholesterol significantly enough to be therapeutic," says Robert H. Eckel, MD, professor of medicine at the University of Colorado Health Sciences Center, in Denver, and chair of the American Heart Association's Council on Nutrition, Physical Activity, and Metabolism. A spokesperson for the FDA said the agency is evaluating the new research but so far has not altered its soy health claim.
Some research shows that eating soy seems to lower cholesterol significantly -- some 5 to 10 percent -- only in people who have very high cholesterol to start with. But ultimately, if your cholesterol is in the danger range, whether soy reduces it by 5 percent or 10 percent hardly matters. "You can't get from an LDL concentration of 200 mg/dl to 100 mg/dl with an agent that lowers cholesterol that little," says John Crouse, MD, professor of medicine and public health sciences at Wake Forest University School of Medicine, in Winston-Salem, North Carolina. "If you have high cholesterol, eating soy is not the answer. You probably need statin drugs. But soy can still be part of a heart-healthy diet."