Soy is a member of the pea family, is a versatile bean native to southeastern Asia. This tropical plant grows up to five feet and forms clusters of three to five pods, containing two to four beans per pod each. Soy is also found in more easily digestible forms such as, soy milk, tamari soy sauce, tofu, miso (soybean paste) and tempeh (kind of soycake). Soy is especially important source of proteins for vegetarians or vegans as soy protein supply all the essential amino acids that are required by the body. Also soy and components of soy contains isoflavones (such as genistein) believed to have estrogen like effects in the body, this is the reason they are called ‘phytoestrogens’.
Health and soy
Soy protein when added to the diet may decrease blood cholesterol (total) and low density lipoprotein moderately. It may also lower triglycerides to smaller extent.
Soy formula when given to infants or children with diarrhea may experience fewer days of diarrhea and fewer bowel movements. Addition of soy fiber may increase the effectiveness.
Soy products may have a role in decreasing menopausal symptoms such as hot flashes.
An isoflavone found in soy (genistein) may pose anti-cancer effects by blocking new blood cell growth, causing cancer cell death and acting as tyrosine kinase inhibitor. Including soy protein in diet is also associated with low incidences of breast cancer; however this effect can be due to other lifestyle changes.
Phytoestrogens may be beneficial for cyclic breast pain in post menopausal women, may have favorable effects on cognitive function and may increase bone mineral density, thus decreasing the risk of fractures.
Soy may be beneficial for patients with diabetes as it may decrease blood sugar levels.
These health benefits of soy are based on unclear scientific evidences, for safe and effective use of soy and its products in these areas, more conclusive results are required.
Side effects and soy
Soy and its products are staple for many people and may have no significant long term toxicity. However soy protein may be associated with intestinal and gastric difficulties.
Infants on soy formula may experience growth failure, damage to the intestinal wall, diarrhea and vomiting. Some may experience decreased thyroid hormone and increased thyroid stimulating hormone.
Regular intake of raw soybean and its products made from unroasted or unfermented beans can cause damage to the pancreas.
Soy and its products are often restricted in patients with hormone sensitive malignancies like breast, uterine or ovarian cancer due to its estrogen like effects on the body.
Soy protein is well tolerated in pregnant and lactating women when given in diet. However high doses of soy and its products are not recommended in these conditions as it may cause abnormality in infant growth.
Soy and soy products must be taken in recommended allowances. Consult a health care professional if is used in special conditions like cancer, diabetes or for lowering blood cholesterol.