Soy What

There is increasing evidence that isoflavones, plant estrogens found in soy foods, may have some of the same effects as estrogen. Beneficial effects may include:

  • Lower blood lipid levels—Soy may decrease total cholesterol, low-density lipoprotein cholesterol, and triglycerides.
  • Decreased cancer risk—Cancer population studies show a decreased risk for hormone-related cancers of the breast, ovary, endometrium, and prostate in countries where plant-based diets with a high content of phytoestrogens are consumed.
  • Diminished menopausal symptoms—Population studies show that women who eat soy as their main protein source may have far fewer distressing menopausal symptoms.

responsible (along with the known vitamins, minerals, and fiber found in plant foods) for the health-promoting effects, is just beginning to be understood.

The antioxidant beta-carotene is one of a group of phy-tochemicals known as carotenoids. Beta-carotene, the substance that gives carrots their orange color and their name, is converted to vitamin A (retinol) in our body. Other carotenoids include lutein and zeaxanthin (from green vegetables) and lycopene (from tomatoes). Diets rich in foods containing carotenoids have been associated with a reduced risk of cancer and heart disease. Researchers are also investigating whether lutein-rich diets may be linked to a lower risk for macular degeneration, a disease of the retina that may lead to blindness.

The isoflavones found in soybeans are associated with lower blood cholesterol and a decreased risk for coronary artery disease. In addition, isoflavones, which are also referred to as phytoestrogens (estrogen-like molecules isolated from plants), appear to reduce some of the symptoms of menopause and may confer a lower risk for breast and other cancers (see sidebar: Soy What? this page). For health benefits, 20 to 25 grams of soy protein per day is recommended. For some of the other phytochemicals that have been identified, see the sidebar Phytochemicals: A Food Pharmacy That May Fight Disease, page 35.

Although some phytochemicals are now available in pill form, we do not yet know enough about how they function to assume that any one, on its own, will promote health and prevent disease without the presence of the vitamins, minerals, fiber, and other, as yet unidentified, substances in plant foods. Scientists are making progress in determining how phytochemicals work, but the best way to ensure an adequate intake of all potentially health-promoting substances in foods of plant origin is to eat the foods themselves—fruits, vegetables, beans, nuts, seeds, and whole grains. See the Appendix: Phytochemical Contents of Selected Foods, page 484.

Common Soy Foods Protein Calories _(grams)_

1/3 cup roasted soy nuts

23

260

1/2 cup soybeans, mature, cooked

14

150

1/2 cup soybeans, green, cooked

11

126

1 cup soy milk

7

80

3 ounces tofu, silken, firm

6

50

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