Isoflavones are natural plant substances found mainly in soy and soy products (such as tofu, soybean oil or soy beverages). They’re also called phytoestrogens, because their chemical structure resembles that of the female sex hormone estrogen. There’s been much discussion about the value of isoflavones: they’re rich in protein, essentiel fatty acids, vitamins and minerals, as well as dietary fibre. Because of this, many doctors and nutritionists agree that they’re an important component of a healthy diet. While Asian people consume a large amount of isoflavones, the typical Western diet still contains far less. Total dietary intake should be around 50 g a day (see Foods that Fight Cancer. Preventing Cancer through Diet by R. Béliveau and D. Gingras. Montreal: McClelland & Stewart, 2006), but there is still some controversy around their effect in cases of cancer.
Isoflavones act like hormones, and have been identified as playing a role in the growth of some cancer cells. On the other hand, it appears they may have some potential to lower the risk of cancer developing. Contradictory findings from research limit their safe use. For example, a recent study among Japanese men who regularly consumed isoflavones showed a decrease in the risk of localized prostate cancer, but a rise in the risk of advanced cancer.
At present, we just don’t have enough solid evidence on which to base a recommendation of soy supplements for prostate cancer prevention.
