Description

Annual growing to 6½ ft (2 m). Has leaves with 3 leaflets, white or purple flowers, and pods with 2–4 beans.

Habitat & Cultivation

Soy is native to southwestern Asia, and is cultivated in warm temperate regions. The pods are gathered when ripe.

Parts Used

Beans, sprouts.

Constituents

Soy contains protein (about 30%), fixed oil (about 17%), including lecithin (2% or more), linoleic acid, and alpha-linolenic acid, isoflavones, coumestrol, sterols, saponins, vitamins, and minerals. Coumestrol and the isoflavones closely mimic estrogen within the body.

History & Folklore

A staple food in much of Asia, soy has been used in China for at least 5,000 years. Soy was introduced in the United States in 1804 and has become a major crop in the South and Midwest. It is now one of the world’s most important food crops.

Medicinal Actions & Uses

Although soybeans and soy produce have little direct medicinal value, they are highly important as foods, providing unusually high levels of protein, lecithin, and essential fatty acids. However, the beans may have a protective role against cancer, notably breast cancer.

Their significant estrogenic activity makes them a particularly good medicinal food for women going through menopause, helping to relieve symptoms such as hot flashes, and to protect against osteoporosis. In Chinese medicine, soybean sprouts (also highly nutritious) are thought to help relieve “summer heat” and fever.

Research

Soybean is a remarkable nutrient, rich in protein, fats, and estrogenic substances, all of which make it an excellent food. The isoflavones, sterols, saponins, and fiber contribute to soy’s protective activity against cancer, and countries such as Japan are thought to have lower levels of cancer because of the great quantity of soy produce eaten there.

The isoflavones, coumestrol, and sterols are all phytoestrogens. These appear to inhibit estrogen within the body when estrogen levels are too high (for example, in menstrual disorders), and to compensate when estrogen levels are low (such as during menopause). Unrefined soybean oil contains high levels of lecithin and polyunsaturated essential fatty acids, which support healthy levels of blood fat such as cholesterol.