35 Phytoestrogens in cereal foods: Availability and activity.

Johanna W. Lampe. Cancer Prevention Research Program, Fred Hutchinson Cancer Research Center, Seattle, WA 98109.

Lignans are the primary phytoestrogens identified in cereal grains. These are diphenols localized in the aleurone layer and therefore found in highest concentration in the whole grain or the bran of certain cereals. Matairesinol and secoisolariciresinol, the two major lignans that have been isolated from plant foods, are converted to more biologically active compounds, enterolactone and enterodiol, by bacteria in the intestine. Additional precursors to enterolactone and enterodiol probably exist; these have yet to be identified. Flaxseed is the most abundant source of dietary lignans, containing secoisolariciresinol at concentrations over 3500 µg/g. Wheat, rye, oats, barley, and triticale also contain varying amounts of both matairesinol and secoisolariciresinol. Because of the tight association between lignans and the fiber-portion of the grain, effects of processing on lignan content and availability in a cereal food must be considered carefully. There is significant interest in these compounds because of their weak estrogenic activity and their potential to alter sex hormone metabolism, and therefore influence the risk of hormone-related diseases. Research in the areas of cancer and cardiovascular disease has suggested that lignans may play a role in disease prevention, acting via a number of different mechanisms.