Estradiol implicated in link between fiber intake and lipoproteins
MedWire News: The beneficial impact of dietary fiber intake on lipid levels may be partly mediated by estradiol, a study of healthy premenopausal women has found.
The study included data on 259 healthy women who were monitored over a 2-year period for serum lipoprotein and hormone levels and dietary fiber intake. The women were participating in the BioCycle Study, a prospective cohort study into the impact of reproductive hormones on oxidative stress.
As expected, high total fiber intake (defined as ≥22 g/day) and high soluble fiber intake (≥4.4 g/day) were associated with decreased levels of total and low-density lipoprotein (LDL) cholesterol, with no significant effect on high-density lipoprotein cholesterol.
By eliminating confounders, the team showed that the effect of fiber intake on lipoprotein levels was direct and causal. However, they also identified an indirect pathway that was mediated by levels of estradiol.
"The observed direct effects of fiber on total and LDL cholesterol provide further insights regarding possible biologic mechanisms of fiber on lipoprotein metabolism, suggesting that fiber has a direct effect on lowering lipoprotein cholesterol levels, in addition to its effect that operates through estradiol," write Sunni Mumford (National Institute of Child Health and Human Development, Rockville, Maryland) and fellow researchers.
The researchers say their study supports current recommendations for a high-fiber diet, but note that very high quantities of fiber were needed to have a beneficial impact. They also suggest that the effects might be slightly diminished among premenopausal women, in view of their higher estradiol levels.
"These findings regarding direct effects provide further insight into possible biologic mechanisms and support the hypothesis of a direct effect that might work through alternative pathways such as bile acid metabolism," they conclude in the American Journal of Epidemiology.
"More research is needed to elucidate these mechanisms among premenopausal women."
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By Joanna Lyford