Soy

How does Soy work?

Soy contains "isoflavones" which are changed in the body to "phytoestrogens," which are similar to the hormone estrogen.

Are there safety concerns?

Consuming foods containing soy protein or taking soy protein products is LIKELY SAFE. Taking dietary supplements with soy extracts is POSSIBLY SAFE when used short-term (up to 6 months). Soy can cause some mild side effects such as constipation, bloating, and nausea. It can also cause allergic reactions involving rash and itching in some people.

Long-term use of high doses of soy dietary supplements is POSSIBLY UNSAFE. There is concern that taking high doses might cause abnormal tissue growth in the uterus.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Soy protein is LIKELY 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 LIKELY 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.

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

Endometrial cancer: Long-term use of concentrated soy isoflavone tablets might increase the occurrence of precancerous changes in the tissue lining the uterus. Don't take concentrated soy isoflavone supplements if you have endometrial cancer.

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.

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.

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).

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

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

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

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.


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