Soy as food looked safe; high-dose supplements were not endorsed
A review of 131 studies found no sign soy harms women with breast cancer, and called two to three servings a day, about 25 to 50 mg of isoflavones, safe.
What the study found
Soy food cleared, and high-dose supplements left unendorsed
A review of 131 studies found no sign soy harms women with breast cancer, tamoxifen users included, and called two to three servings a day, roughly 25 to 50 mg of isoflavones, safe and possibly protective. It declined to endorse supplements at 100 mg or more, where safety is unconfirmed.
The caveat · A verdict with few numbers behind it
Most outcomes are synthesised narratively rather than pooled, so there are few numbers behind the verdict. The reassurance covers soy as food, not concentrated extracts, which is the distinction the 100 mg line marks. It was conducted at a naturopathic college, which has an interest in the answer.