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What is it? Overview Usage Side Effects and Warnings

What is Soy?

The soybean has been prized for centuries in Asia as a nutritious, high-protein food with a myriad of uses, and today it's popular in the United States not only in Asian food, but also as a cholesterol-free meat and dairy substitute in traditional American foods. Soy burgers, soy yogurt, tofu hot dogs, and tofu cheese can be found in a growing number of grocery stores alongside the traditional white blocks of tofu, and soy is increasingly used as a protein filler in many prepared foods, including fast-food “hamburger.”

Soy appears to reduce blood cholesterol levels, and the US Food and Drug Administration has authorized allowing foods containing soy to carry a "heart-healthy" label.

Soybeans contain isoflavones, chemicals that are similar to estrogen. These are widely thought to be the...

According to the combined evidence of numerous controlled studies, soy can reduce blood cholesterol levels and improve the ratio of LDL ("bad") versus HDL ("good") cholesterol. 1 At an average dosage of 47 g daily, total cholesterol falls by about 9%, LDL cholesterol by 13%, and triglycerides by 10%. Soy's effects on HDL cholesterol itself are less impressive. There is inconsistent evidence regarding whether soy might help reduce high blood pressure . 2 Indeed, a comprehensive and careful review of studies investigating the influence of phytoestrogens (including soy meals) on blood pressure found no meaningful effect. 3 However, another review found that soy protein (as opposed to other soy products) could significantly reduce blood pressure. 4 Soy may...

Safety Issues

Studies in animals have found soy essentially nontoxic. 5 And it is reassuring to note that researchers found no evidence of ill effects when they gave healthy postmenopausal women 900 mg of soy isoflavones a day for 84 consecutive days. 6 However, soy or its isoflavones could conceivably have some potentially harmful effects in certain specific situations.

Soy appears to have numerous potential effects involving the thyroid gland. When given to individuals with impaired thyroid function , soy products have been observed to reduce absorption of thyroid medication. 7 8 9 10 11 12 13 14 15 16 17 18 19 20 In addition, some evidence hints that soy isoflavones may directly inhibit the function of the thyroid gland,...