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.