Nutrition
Does soy harm your hormones?
Short answer
Studies in humans do not show that normal portions of soy harm hormones. Soy isoflavones are much weaker than human oestrogen, and in large population studies soy has a neutral or beneficial effect, including on breast cancer risk. The worries come mainly from animal studies and high doses of isolated extracts.
Tofu, soy drink and edamame are food, not medicine. Isoflavones are counted in milligrams: a portion of tofu (about 85 g) has about 20 mg, and women in Asian countries eat about 46 mg a day on average. According to the Harvard T.H. Chan School of Public Health, soy can safely be eaten several times a week, and probably more often.
Two caveats: if you take levothyroxine for an underactive thyroid, agree with your doctor on a gap between the medicine and soy meals (soy can reduce absorption of the drug) and look after iodine. If you are allergic to soy, avoid it, of course. Plant protein is covered in “Where do vegans get protein?”.