Human breast cancer: concerted role of diet, prolactin and adrenal C19-delta 5-steroids in tumorigenesis.

The low incidence of breast cancer in Japan disappears within 2 generations in migrant Japanese in the USA. This is of fundamental importance if we are to understand, and perhaps reverse, the high rate seen in Western countries. Diet is the most likely factor involved, and a review of the topic of diet, body mass index, and gain in adult body mass, supports a relationship between these factors and breast-cancer risk in post-menopausal, but not pre-menopausal, women. A direct link between nutritional factors and secretion of the hormones prolactin and dehydroepiandrosterone sulfate is proposed. An estrogen 5-androstene-3 beta, 17 beta-diol is formed peripherally from the latter steroid, and in Western women attains a blood concentration at which it is biologically active. Thus diet/fat provides factors, viz., fatty acids, prolactin and estrogen, which in concerted fashion provide a milieu conducive to mammary tumorigenesis.