Soy's Power to Lower Cholesterol Downgraded


FROM VEGGIE burgers to soy milk, a number of soy products claim they can help reduce the risk of heart disease. It's a promise allowed by the government because of some evidence that soy can lower blood cholesterol. To make the claim, the food must contain at least 6.25 grams of soy protein per serving. And the label has to specify that you need to eat at least 25 grams of soy protein every day--or four such servings--in order to see any benefit.

But researchers from Tufts's Cardiovascular Nutrition Laboratory have found that even people who eat double the health claim level lower their cholesterol only modestly--and then, only if it's quite high to begin with. The Tufts scientists provided different diets for 6 weeks each to several dozen men and women with high cholesterol, comparing a high soy protein regimen of at least 50 grams per day with a diet high in protein from animal foods.

The group's average LDL, or "bad," cholesterol levels were elevated at the outset--more than 130 (milligrams per tenth of a liter of blood). But only those with particularly high LDL, over 160, saw any benefit from soy. And that effect was a small one: decreases of 4 percent for total cholesterol and 5 percent for LDL.

Earlier research that provided much of the original support for the health claim found LDL reductions from 7 to 24 percent. But the new numbers jibe with results of recent studies that have come out in the years since then, the researchers point out.

Because of the new findings, the Tufts scientists caution people against relying on "casual" soy food use to control cholesterol levels. To get even the modest benefit conferred by soy protein in the study, people with high blood cholesterol would have to commit to a consistent, high intake of soy foods every single day.

None of this is to say that you should dump soy from your diet. Granted, the effects of soy on its own are negligible. But researchers at Tufts and elsewhere have consistently shown that the best way to lower cholesterol with diet is to decrease animal protein, which tends to come coupled with heart-unhealthy saturated fat. And one of the most convenient ways to do that is to replace animal foods with foods of plant origin, which contain very little saturated fat. Soy-based items such as tofu, certain veggie burgers, and soy milk are among those foods.

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