Profiles of phytoestrogens in human urine from several Asian countries

Intake of a diet rich in phytoestrogens has been associated with a decreased risk for hormone-dependent cancers in humans. Biomonitoring of phytoestrogens in human urine has been used to assess the intake of phytoestrogens. Although studies have reported phytoestrogen levels in urine specimens from the United States and Japan, little is known of human intake of phytoestrogens in other Asian countries. In this study we determined the concentrations of seven phytoestrogens, namely, enterolactone, enterodiol, daidzein, equol, O-desmethylangolensin (O-DMA), genistein, and coumestrol, in 199 human urine samples from three Asian countries, Vietnam (Hanoi and Ho Chi Minh), Cambodia (Phnom Penh), and India (Chennai and Kolkata), using a simple, sensitive, and reliable liquid chromatography (LC)-tandem mass spectrometry (MS/MS) method. The residue levels of phytoestrogens in urine samples from the three Asian countries were compared with the concentrations in 26 urine samples from Japan (Ehime) and 16 urine samples from the United States (Albany), analyzed in this study. Among the phytoestrogens analyzed, isoflavones such as daidzein and genistein were predominant in urine samples from Vietnam; samples from Cambodia and India contained higher concentrations of enterolactone than isoflavones. Urinary concentrations of isoflavones in samples from Hanoi, Vietnam, were notably higher than the concentrations in samples from Cambodia, India, and the United States and similar to the concentrations in samples from Japan. The lowest concentrations of daidzein and the highest concentrations of enterolactone were found in urine samples from India. Concentrations of equol and O-DMA, which are microbial transformation products of daidzein (produced by gut microflora), were notably high in urine samples from Hanoi, Vietnam. The ratios of the concentration of equol or O-DMA to that of daidzein were significantly higher in samples from Hanoi than from Japan, indicating high biotransformation efficiency of daidzein by the population in Hanoi. High concentrations of equol, in addition to isoflavones, in urine have been linked to reduced breast cancer risk in previous studies, and, thus, the Vietnamese population may have potential protective effect against breast cancer. This study suggests that the dietary intake and profiles of phytoestrogens vary considerably, even among Asian countries.