Hormonal
Soy Protein Isolate (SPI) and purified soy isoflavones (genistein, daidzein) exhibit weak estrogenic activity that may pose risks for reproductive health, early development, and estrogen-sensitive cancers, despite conflicting evidence from some human studies.
If you are taking soy protein isolate or purified soy isoflavone supplements (not just eating tofu/edamame), be aware they have weak estrogenic effects. Women with a history of endometriosis or estrogen-sensitive cancers should consult a doctor before using these supplements, as they may increase risk. Infants should generally be fed cow milk formula unless soy is medically indicated.
These compounds can reach potentially estrogenic levels after SPI consumption... Concerns have focused on potential estrogenic effects in early development resulting in reproductive toxicity, infertility, demasculinization, and increased promotion of estrogen-responsive cancers... purified isoflavones such as genistein... can achieve far higher plasma levels... There have been case reports of endometriosis in women consuming isoflavone supplements... likelihood of increased risk of estrogen-sensitive cancers
Why this rating
Evidence is mixed; animal studies show clear estrogenic effects, but human data is contradictory with some studies showing no effect and others showing subtle changes (e.g., DNA methylation, age of menarche).
Source
Adverse Effects of Nutraceuticals and Dietary Supplements
Martin J. J. Ronis et al. · The Annual Review of Pharmacology and Toxicology · 2017
DOI 10.1146/annurev-pharmtox-010617-052844
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