Topic Overview

Soy is high in isoflavones. Isoflavones are a type of phytoestrogen. Phytoestrogens are chemicals found in plants that work like estrogens. In some ways, the human body can use them like estrogens.^{footnote 1}

Are soy isoflavones effective?

Menopause symptoms. Soy products may improve menopausal symptoms, such as hot flashes. This is based on mixed evidence. So far, studies have used many different soy sources and different measures of success, which are hard for experts to compare. Soy isoflavone (rather than soy protein) studies have shown the most promise for hot flash treatment.^{footnote 2}

Are soy isoflavones safe?

Eating and drinking soy on a daily basis has no known risks. For some people, it upsets the digestive system.

The long-term effects of a diet high in soy have not been well-studied. High soy intake can’t be considered safe until more research is done.^{footnote 2}

Some experts think that soy phytoestrogen does not lead to cancer like estrogen can. But this has not been proven. Experts do not yet know if a high-soy diet is a risk for women who have had breast cancer.^{footnote 2}

Making soy a part of your daily diet

Isoflavones are short-acting. If you use soy for health reasons, try to eat it throughout the day, rather than all at once. Try to eat 40 mg to 80 mg of isoflavones each day.^{footnote 2, footnote 1}

Remember that soy protein is different than soy isoflavone. A high-protein soy food may or may not have a large amount of isoflavones in it.

Soy comes in many forms, so you have a lot of choices for adding soy isoflavones to your diet.