Soy

Soy is the seed of the soybean, a legume cultivated for thousands of years in East Asia and now grown in many parts of the world. Its seeds develop inside pods, usually containing two or three beans. Soybeans are rich in protein and provide all nine essential amino acids, although some are present in lower amounts than in many animal proteins.

They also contain unsaturated fats, carbohydrates, fiber, minerals and plant compounds called isoflavones. These can interact with estrogen receptors, but their effects are not identical to human estrogen. Soybeans may be eaten whole or fermented, or processed into tofu, tempeh, miso, soy sauce and soy milk.

Their nutritional composition varies with the variety and preparation. Soybeans are also important in agriculture. They form a partnership with certain soil bacteria that fix atmospheric nitrogen in nodules on their roots. This supplies nitrogen to the plant and can reduce its need for nitrogen fertilizer, although soil fertility still needs management.

Soy is widely used for human food and animal feed, and the seeds are processed to produce soybean oil and other ingredients. Processing can change texture, digestibility and nutrient availability. For people who tolerate it, soy foods can be a useful protein source in a varied diet. People with a soy allergy need to avoid products containing soy.