DALLAS – Veggie burgers and tofu might not be so great at warding off heart disease after all.
An American Heart Association committee reviewed a decade of studies on soy's benefits and came up with results that are now casting doubt on the health claim that soy-based foods and supplements significantly lower cholesterol.
The findings could lead the Food and Drug Administration to re-evaluate rules that currently allow companies to tout a cholestorol-lowering benefit on the labels of soy-based food.
The panel also found that neither soy nor the soy component isoflavone reduced symptoms of menopause, such as "hot flashes," and that isoflavones don't help prevent breast, uterine or prostate cancer. Results were mixed on whether soy prevented postmenopausal bone loss.
Based on its findings, the committee said it would not recommend using isoflavone supplements in food or pills. It concluded that soy-containing foods and supplements did not significantly lower cholesterol, and it said so in a statement recently published in the journal Circulation.
Nutrition experts say soy-based foods still are good because they often are eaten in place of less healthy fare like burgers and hot dogs. But they don't have as much direct benefit as had been hoped on cholesterol, one of the top risk factors for heart disease.
"We don't want to lull people into a false sense of security that by eating soy they can solve the problem (with cholesterol)," said Dr. Michael Crawford, chief of clinical cardiology at University of California San Francisco Medical Center.
"If they are radically altering their diet where they're only eating soy in the hopes that this is going to bring their cholesterol down, they're deluding themselves," said Crawford, who was not on the panel that issued the new statement.
The FDA in 1999 started allowing manufacturers to claim that soy products might cut the risk of heart disease after studies showed at least 25 grams of soy protein a day lowered cholesterol. A year later, the Heart Association recommended soy be included in a diet low in saturated fat and cholesterol.
But as more research emerged, the Heart Association decided to revisit the issue. 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.
They did a separate analysis of isoflavones. The review of 19 studies suggested that soy isoflavones also had no effect on lowering LDL cholesterol or other lipid risk factors.
"Soy proteins and isoflavones don't have any major health benefits other than soy protein products are generally good foods," said Dr. Frank Sacks, a professor of nutrition at the Harvard School of Public Health in Boston who led the committee. "They're good to replace other foods that are high in cholesterol."
Still, the Heart Association statement notes that soy products like tofu, soy butter, soy nuts and some soy burgers should be heart-healthy because they contain a lot of polyunsaturated fats, fiber, vitamins and minerals and are low in saturated fat.
"Soy isn't a magic bullet, but it can be a valuable contributor to a heart-healthy diet," said Jo Ann Carson, a professor of clinical nutrition at the University of Texas Southwestern Medical Center at Dallas who was not part of the panel.
It's important not to think about foods in black-and-white terms, said Dr. Michael Lim, director of the cardiac catheterization lab at Saint Louis University School of Medicine.
"There's no quick fix," he said. "Our bad cholesterol numbers would certainly get worse if instead of eating tofu burgers we went out and had hamburgers each night of the week."