Changes in serum enterolactone, genistein, and daidzein in a dietary intervention study in Finland.

Phytoestrogens are plant-derived compounds that may have cancer-protective properties. The purpose of the study was to see how enterolactone, daidzein, and genistein serum concentrations reflect major changes in the diet of Finnish subjects. Phytoestrogen concentrations were measured by time-resolved fluoroimmunoassay after hydrolysis and extraction in samples from 85 middle-aged subjects who were part of a 12-week dietary intervention study carried out in North Karelia, Finland. In the baseline and the switchback periods, the subjects consumed their habitual Finnish diet, which is high in saturated fat and low in polyunsaturated fat and vegetables. During the 12-week intervention period, the proportion of dietary energy derived from fat was reduced from approximately 39% to 23%, and the consumption of vegetables, fruit, and berries was markedly increased. Enterolactone concentrations were measured during the baseline, intervention, and switchback periods. The median concentration of enterolactone rose from 12.2 to 19.5 nmol/l (P = 0.002) during the low-fat, high-vegetable diet. Daidzein and genistein concentrations were very low and did not change during the intervention. At baseline, 65% of the population had a low serum enterolactone concentration of <15 nmol/l. During the intervention period, this proportion fell to 34%. These major differences in serum enterolactone concentrations suggest that enterolactone may be used as a biomarker of a healthy diet containing plenty of vegetables, fruit, and berries.