Food sources of phyto-oestrogens and their precursors in Europe.

Phyto-oestrogens are dietary components found in some plants, which act in vivo like weak oestrogens. They may reduce the risk of some degenerative diseases moderated by oestrogen, including breast cancer and osteoporosis. The most widely studied are the isoflavones genistein and daidzein from soyabeans, but lignans may be more prevalent in the European diet. Soya foods have traditionally been consumed in the Orient for millennia, and are now widely available to European consumers. Levels of isoflavone in soyabeans from published literature vary between 560 and 3810 mg/kg, depending on variety and growing conditions. Soya protein concentrates and isolates derived from soyabeans contain 466-615 mg isoflavones/kg. Traditional soya milk, bean curds, bean sprouts, etc. contain 13 to 2030 mg isoflavone/kg, depending on the starting raw material and final water content. Fermented foods have a different isoflavone conjugate profile, which may be important in absorption and metabolism. Soya analogues of European foods include dairy and meat products, which contain 38 to 3000 mg total isoflavones/kg, depending the source of soya and dilution with other ingredients. A wide range of foods contain low levels of soya-derived isoflavones, but such foods do not make a significant contribution to mean intakes in Europe. Flaxseed is by far the richest source of lignan precursors. However, foods such as cereal brans, legumes and some vegetables are a more important source in the diets of Europeans because they are more widely consumed. For similar reasons, compared with soya isoflavones, lignans may be a more important source of phyto-oestrogens in the diets of Europeans.