Substance display

When taken by mouth: It is LIKELY SAFE to eat foods or products containing soy protein. Dietary supplements containing soy extracts are POSSIBLY SAFE when used for 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, itching, and anaphylaxis 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 supplements containing soy extract is POSSIBLY UNSAFE. There is some concern that this might cause abnormal tissue growth in the uterus. However, eating large amounts of soy does not seem to have this effect.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Consuming soy protein in amounts normally found in food is LIKELY SAFE when pregnant or breast-feeding. However, soy is POSSIBLY UNSAFE when used in the larger amounts found in medicine when pregnant. Higher doses during pregnancy might harm development of the baby. There isn't enough reliable information to know if soy is safe to use in the larger amounts found in medicine when breast-feeding. Stay on the safe side and stick to food amounts.

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.

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 supplements 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). *