https://www.mskcc.org/cancer-care/integrative-medicine/herbs/soy
Soy may reduce risk of prostate (21) (22) (23), lung (24) (80), and endometrial (25) (26) cancers, but can increase the risk of bladder cancer (27) and endometrial hyperplasia (28). It was also shown to prevent breast cancer(29) (30) but conflicting data suggest that soy supplementation may have adverse effects (31) (32). A study done in mice suggests that consumption of soy products may increase metastasis (33).
Reference
29. Cline JM, Hughes CL, Jr. Phytochemicals for the prevention of breast and endometrial cancer. Cancer Treat Res. 1998;94:107-134.
30. Butler LM, Wu AH, Wang R, et al. A vegetable-fruit-soy dietary pattern protects against breast cancer among postmenopausal Singapore Chinese women. Am J Clin Nutr. Apr 2010;91(4):1013-1019.
31. Trock BJ, Hilakivi-Clarke L, Clarke R. Meta-analysis of soy intake and breast cancer risk. J Natl Cancer Inst. Apr 5 2006;98(7):459-471.
32. Steinberg FM, Murray MJ, Lewis RD, et al. Clinical outcomes of a 2-y soy isoflavone supplementation in menopausal women. Am J Clin Nutr. Feb 2011;93(2):356-367.
33. Martinez-Montemayor MM, Otero-Franqui E, Martinez J, et al. Individual and combined soy isoflavones exert differential effects on metastatic cancer progression. Clin Exp Metastasis. Oct 2010;27(7):465-480.
