Soy Isoflavones

Soy comes from soybeans. The beans can be processed into soy protein, which is a powder; soymilk, which is a beverage that may or may not be fortified with extra calcium from the soybeans; or soy fiber, which contains some of the fibrous parts of the bean.

Soy is taken by mouth for high cholesterol, high blood pressure, and preventing diseases of the heart and blood vessels. It is also used for type 2 diabetes and kidney disease associated with diabetes, asthma, as well as preventing weak bones (osteoporosis), preventing joint pain and stiffness in people with arthritis, and slowing the progression of kidney disease. Soy is also taken by mouth to prevent different kinds of cancer.

Soy is also taken by mouth for treating constipation, diarrhea, Crohn's disease, hepatitis C, metabolic syndrome, fibromyalgia, weight loss, enlarged prostate, as well as decreasing protein in the urine of people with kidney disease, improving memory and mental function, improving muscle strength, and treating muscle soreness caused by exercise.

Women take soy by mouth for breast pain, preventing hot flashes after breast cancer, menopausal symptoms, premenstrual syndrome (PMS), and migraine headaches during menstruation.

Soy is used as a milk substitute in infant feeding formulas, and as an alternative to cow's milk. It is fed to infants who are unable to process the sugar galactose, who are lactose intolerance, who have a condition called hereditary lactase deficiency, or who have infant colic.

Soy is applied to the skin to improve photo-aged skin or wrinkled skin.

Soy is applied inside the vagina to treat vaginal swelling due to decreased lubrication and thinning vaginal tissue (vaginal atrophy).

In foods, soybeans are eaten boiled or roasted. Soy flour is used as an ingredient in foods, beverages, and condiments.

The active ingredients in soy are called isoflavones. A study of the quality of commercially available soy supplements suggests that less than 25% of products contain within 90% of labeled isoflavone content. Paying more for a product doesn't necessarily guarantee that the content shown on the label is accurate.

How does it work?

Soy contains "isoflavones" which are changed in the body to "phytoestrogens." Phytoestrogen molecules are similar in chemical structure to the hormone estrogen. In some cases, these phytoestrogens can mimic the effects of estrogen. In other cases, these phytoestrogens can block the effects of estrogen.

Breast cancer.
Diabetes.
Kidney disease in people with diabetes.
Diarrhea.
Trouble digesting the sugar galactose (galactosemia).
Trouble digesting the sugar lactose (hereditary lactase deficiency).
High cholesterol.
Kidney disease.
Trouble digesting the sugar lactose (lactose intolerance).
Menopausal symptoms
Osteoporosis.

Adults

By Mouth:

For type 2 diabetes: Touchi extract 300 mg three times daily for 3-6 months. Touchi is a traditional Chinese food prepared from soybeans. Fibrous soy hulls 26 grams daily for 4 weeks. Single doses of soy fiber 7-10 grams have also been used. 30 grams of soy protein, containing 132 mg of phytoestrogens, daily for up to 12 weeks.

For high cholesterol: 20-50 grams per day of soy protein.
For protein in the urine of people with kidney disease: a diet limited to 700-800 mg/kg soy protein daily has been used.

For menopausal symptoms such as hot flashes:
20-60 grams per day of soy protein providing 34-80 mg isoflavones. Concentrated soy isoflavone extracts providing 35-200 mg/day of isoflavones. Genistein, a soy isoflavone: 54 mg per day.

For menopausal symptoms such as depression: 100 mg of soy containing 50 mg of isoflavones has been used along with sertraline 50 mg daily.

To reduce body weight during menopause: Soy isoflavones <100 mg daily for up to 6 months have been used.

For preventing weak bones (osteoporosis): 40 grams per day soy protein containing 2-2.25 mg isoflavones per gram has been used for 3-6 months. Soy extract 1 gram containing 80 mg of isoflavones has been used for one year.

Children

by Mouth:

For diarrhea in infants: Soy fiber-fortified formula containing 18-20 grams of soy protein per liter.

Consuming foods containing soy protein or taking soy protein products is SAFE. Taking dietary supplements with soy extracts is SAFE when used short-term (up to 6 months). Soy can cause some mild stomach and intestinal side effects such as constipation, bloating, and nausea. It can also cause allergic reactions involving rash and itching in some people. Some people might experience tiredness. Soy might also affect thyroid function. However, this seems to occur primarily in people who are iodine deficient.

Long-term use of high doses of soy extract is POSSIBLY UNSAFE. There is some concern that taking high doses might cause abnormal tissue growth in the uterus. However, eating large amounts of soy does not seem to have this effect.

Pregnancy and breast-feeding: Soy protein is SAFE to be used during pregnancy and breast-feeding when consumed in amounts normally found in food. However, soy may be POSSIBLY UNSAFE when used during pregnancy in medicinal amounts. Higher doses during pregnancy might harm development of the baby. Not enough is known about the safety of higher doses during breast-feeding. Stay on the safe side and avoid larger doses.

Children: Soy is SAFE for children when used in amounts commonly found in food or infant formula. Using soy formula does not seem to cause health or reproductive problems later in life. However, soymilk that is not designed for infants should not be used as a substitute for infant formula. Regular soymilk could lead to nutrient deficiencies.

Soy is POSSIBLY UNSAFE when used as an alternative to cow's milk in children who are allergic to cow's milk. Although soy protein-based infant formulas are often promoted for children with milk allergy, these children are often allergic to soy as well.

Don't give children soy in amounts larger than what is found in food or formula. Researchers don't know whether soy is safe for children at higher doses.

Hay fever (allergic rhinitis): People with hay fever are more likely to be allergic to soy hulls.

Asthma: People with asthma are more likely to be allergic to soy hulls. Avoid using soy products.

Breast cancer: The effects of soy in people with breast cancer are unclear. Some research finds that soy might "feed" certain breast cancers because it can act like estrogen. Other studies have found that soy seems to protect against breast cancer. The difference in effects might have something to do with the amount taken. Because there isn't enough reliable information about the effects of soy in women with breast cancer, a history of breast cancer, or a family history of breast cancer, it's best to avoid using soy until more is known.

Cystic fibrosis: Soymilk can interfere with the way children with cystic fibrosis process protein. Don't give these children soy products.

Diabetes: Soy might increase the risk of blood sugar levels becoming too low in people with diabetes who are taking medication to control blood sugar.

Endometrial cancer: Long-term use of concentrated soy isoflavone tablets might increase the occurrence of precancerous changes in the tissue lining the uterus. However, conflicting evidence exists. Use supplements containing soy isoflavones cautiously if you are at risk for endometrial cancer. Soy foods are likely safe.

Under-active thyroid (hypothyroidism): There is a concern that taking soy might make this condition worse.

Kidney stones: There is some concern that soy products might increase the risk of kidney stones because they contain large amounts of a group of chemicals called oxalates. Oxalates are the main ingredient in kidney stones. Another concern is that people with serious kidney disease aren't able to process some of the chemicals in soy. This could lead to dangerously high levels of these chemicals. If you have a history of kidney stones, avoid taking large amounts of soy.

Milk allergy: Children who are very allergic to cow's milk might also be sensitive to soy products. Use soy products with caution.

Kidney failure: Soy contains a chemical called phytoestrogens. Very high levels of phytoestrogens can be toxic. People with kidney failure who use soy products might be at risk for blood levels of phytoestrogens becoming too high. If you have kidney failure, avoid taking large amounts of soy.

Urinary bladder cancer: Soy products might increase the chance of getting bladder cancer. Avoid soy foods if you have bladder cancer or a high risk of getting it (family history of bladder cancer).