PHYTO-ESTROGEN EXCRETION AND RATE OF BONE LOSS IN POSTMENOPAUSAL WOMEN

Objective: The hypothesis was tested that the rare of postmenopausal b one loss is inversely associated with longterm urinary excretion of ph yto-oestrogens, as a marker of habitual dietary intake. Design: Second ary analysis of a 10-year follow-up study (1979-1989) among postmenopa usal women in the Netherlands. Subjects: From the original population of 154 women, 32 women were selected with an annual rate of radial bon e loss of less than or equal to 0.5% over the first 5 years of the stu dy and 35 women with a rate of less than or equal to 2.5% per year. Me thods: The isoflavonoids genistein, daidzein and equol, and the lignan enterolactone were determined by gas chromatography-mass spectrometry in aggregate samples from annually collected urine samples. Cortical bone density of the radius had previously been measured annually by si ngle-photon absorptiometry. Results: Excretion of isoflavonoids did no t differ between both groups, although in multivariate analysis equol excretion was weakly positively associated with rate of bone loss in t he 5 years after the menopause. Enterolactone excretion was significan tly higher in the group with high rate of bone loss. This positive ass ociation remained in multivariate linear regression analysis after adj ustment for age, years since menopause, body mass index and intake of calcium, vegetable protein and dietary fibre. Conclusions: Enterolacto ne excretion is likely to be an indicator of consumption of grains and legumes; it is not clear whether the observed positive association wi th rate of bone loss is a causal one. Our results do not support a pre ventive effect of low, unsupplemented dietary intake of phyto-oestroge ns on postmenopausal cortical bone loss. However, no conclusions can b e drawn about effects of higher doses of phyto-oestrogens.