Health Guide


What is it?

Soy is a dietary supplement that may be used to prevent heart disease. It may also be used to treat different types of cancer. Other uses include the treatment of menopause ("change of life") symptoms, like hot flashes. Soy may also be used to treat osteoporosis (os-te-o-po-RO-sis) ("brittle bones"), high cholesterol (ko-LES-ter-ol) (fat in blood), kidney disease, and arthritis. It may be used to treat prostate problems in men. Some babies drink soy formula if they are allergic (uh-LER-jik) to other formulas.

Other names for soy include: Soya, Soybean, Genistein, and Daidzein.

Ask your doctor, nurse, or pharmacist if you need more information about this medicine or if any information in this leaflet concerns you.

Before Using:

Tell your doctor if you

  • are taking medicine or are allergic to any medicine (prescription or over-the-counter (OTC) or dietary supplement)
  • are pregnant or plan to become pregnant while using this medicine
  • are breast feeding
  • have other health problems, such as high blood pressure or heart or blood vessel disease


Talk with your doctor, pharmacist, or nurse about how much soy you should take. The amount depends on the strength of the medicine and the reason you are taking soy. If you are using this medicine without instructions from your caregiver, follow the directions on the label. Do not take more soy or take it more often than what is written on the directions.

To store this medicine:

Keep all medicine locked up and away from children. Store medicine away from heat and direct light. Do not store your medicine in the bathroom, near the kitchen sink, or in other damp places. Heat or moisture may cause the medicine to break down and not work the way it should work. Throw away medicine that is out of date or that you do not need. Never share your medicine with others.

Drug and Food Interactions:

Do not take soy without talking to your doctor first if you are taking:

  • Levothyroxine (Synthroid(R), Levothroid(R))
  • Warfarin (Coumadin(R))
  • Iron (soy may reduce the amount of iron used by your body)

Side Effects:

Stop taking your medicine right away and talk to your doctor if you have any of the following side effects.

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing, or rash.

Other Side Effects:

You may have the following side effects, but this medicine may also cause other side effects. Tell your doctor if you have side effects that you think are caused by this medicine.

  • Longer or late monthly periods if you eat a diet high in soy (1)
  • Diarrhea (long term) in babies who drink soy formula (2)


1. Cassidy A, Bingham S & Setchell KDR: Biological effects of a diet of soy protein rich in isoflavones on the menstrual cycle of premenopausal women. Am J Clin Nutr 1994; 60(3):333-340.

2. Donovan GK & Torres-Pinedo R: Chronic diarrhea and soy formulas. Am J Dis Child 1987; 141(10):1069-1071.

Last Updated: 7/4/2018
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