Myth: Soy added to packaged foods raises hormone levels
Isoflavone intake for the average U.S. person is only 2.35 mg/day
or about the amount from one ounce of soymilk, calculated using the USDA database and the National Health and Nutrition Examination Survey (NHANES) III 24-h dietary recall. Often the soy ingredients added to many foods are soy oil and lecithin, which do not contain isoflavones.
Whole soybeans provide isoflavones, which are plants’ natural pytoestrogens and different from human estrogen Isoflavones often block the action of estrogen and thus have a positive role in lowering incidence of breast cancer.
Concerns that Americans are exposed to large amounts of isoflavones because soy is added to a number of commonly consumed foods aren’t borne out by the data. The total mean intake of isoflavones in Asian countries ranges from 25 to 50 mg/d, with a small proportion (10%) consuming as much as 100 mg/d.
Bai W, Wang C, Ren C. Intakes of total and individual flavonoids by US adults. Int J Food Sci Nutr. 2013 Sep 11.
Messina M, Nagata C, Wu AH. Estimated Asian adult soy protein and isoflavone intakes. Nutr Cancer. 2006;55:1–12.