What are the side effects of taking soy isoflavones?

Side effects of soy isoflavones generally depend on the patient’s specific condition—for example, whether the individual is pregnant, a minor, or has an estrogen-related disorder.

1. Pregnancy

Pregnant women are in a relatively unique physiological state. Taking soy isoflavones during pregnancy may allow active ingredients to cross the placenta and be absorbed by the fetus, potentially exerting adverse effects. In severe cases, this may even lead to fetal developmental abnormalities.

2. Minors

Girls who have not yet reached adulthood are still undergoing physical development; their ovaries and uterus remain immature. Supplementing with soy isoflavones at this stage may cause a significant rise in endogenous estrogen levels, adversely affecting normal development—and possibly triggering precocious puberty.

3. Estrogen-Related Disorders

Patients with pre-existing estrogen-related conditions—such as endometritis or endometrial polyps—may experience excessive estrogen accumulation upon taking soy isoflavones. In severe cases, this could even increase the risk of malignant transformation (cancer).