Harvard Health Letter

The not-soy-good results

Soy protein and isoflavones haven't held up well in clinical trials, but there's still a place for soy in our diets.

Once the belle of the health-food ball, soy is looking a little forlorn these days. Claims that soy protein would protect us from heart disease now seem a little inflated. Studies have shown its effect on "bad" LDL cholesterol is pretty small, averaging less than a 5% decrease in most studies. Large amounts of soy protein — 50 grams a day, which is about half the amount of protein that Americans typically eat in a day — have had the same modest effect as smaller amounts.

Researchers have looked — but haven't found — much in the way of benefit for other cardiovascular risk factors, such as "good" HDL cholesterol, triglycerides, and blood pressure.

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