Diet and breast cancer.

It is a general opinion that the Western diet plays a significant role in increasing the risk of breast cancer in the Western World. Recently some likely mechanisms involved in increasing the risk have been disclosed. It has been found that a Western-type diet elevates plasma levels of sex hormones and decreases the sex hormone binding globulin concentration, increasing the availability of these steroids for peripheral tissues. The same diet results in low formation by intestinal bacteria of mammalian lignans and isoflavonoid phyotestrogens from plant precursors. These diphenolic compounds seem to affect hormone metabolism and production and cancer cell growth by many different mechanisms making them strong candidates for a role as cancer protective substances. The sex hormone pattern found in connection with a Western-type diet combined with low lignan and isoflavonoid excretion was found particularly in postmenopausal breast cancer patients and omnivores living in high-risk areas, and to a lesser degree in areas with less risk. However, the pattern observed was not entirely due to diet.