CHAMPAIGN, Ill. — People with total cholesterol levels exceeding 240 could benefit substantially by eating 25 to 50 grams of soy protein daily, according to a scientific advisory directed to health-care professionals across the United States.
"There is increasing evidence that consumption of soy protein may help lower blood cholesterol levels in some people with elevated cholesterol levels, and it may provide other cardiovascular benefits," said John Erdman, a University of Illinois professor of nutrition who wrote the advisory for the American Heart Association Nutrition Committee.
The advisory appeared in the medical journal Circulation, which is published by the association. The Food and Drug Administration allows producers to claim health benefits on foods containing 6.5 grams of soy protein and suggests four servings, or 25 grams, daily. The journal cited 38 clinical studies and concluded that consuming between 25 to 50 grams per day is both safe and effective in reducing low-density lipoprotein (LDL) cholesterol by up to 8 percent. LDL is considered the "bad" cholesterol in blood.
"When foods containing intact soy protein were substituted in these studies for animal protein," Erdman said, "they significantly lowered blood levels of total cholesterol as well as LDL cholesterol and triglycerides, and they actually increased the levels of the good HDL [high-density lipoprotein] cholesterol by 2.4 percent or more."
People with total cholesterol profiles of under 200, a count considered "normal," will gain little in terms of lowering cholesterol, the advisory noted. However, Erdman said, they may receive cardiovascular benefits that appear to come from the isoflavones in soy. Such consumption, in place of some animal or milk protein, also would reduce a person’s intake of cholesterol and fat.
Consumers with high cholesterol, Erdman said, should look for products that provide 10 grams of soy protein per serving and eat two to three servings per day. Studies at the UI have consistently shown that 20 grams of soy protein a day can significantly lower total cholesterol levels.
Soy protein, an edible component of the soybean, is different from many other proteins derived from vegetable sources because it is complete. Like animal protein, it contains all the essential amino acids in sufficient quantities to support human life.
Among the components of soy protein that may contribute to its cholesterol-lowering ability are trypsin inhibitors, phytic acid, sapopins, isoflavones and fiber. Soy protein is available as a liquid, flour or concentrated powder.
"It’s important that all of these components be left intact during processing," Erdman said. "Otherwise, the benefits may be diminished or lost."