Effect of daily fiber intake on luteinizing hormone levels in reproductive-aged women

To evaluate whether the association between fiber intake and LH levels is driven by the association between fiber and estradiol, or whether there is an independent association. A prospective cohort of 259 premenopausal women were followed for up to 2 menstrual cycles. Estrogen and LH were measured a parts per thousand currency sign8 times per cycle at visits scheduled using fertility monitors. Diet was assessed a parts per thousand currency sign4 times per cycle by 24-h recall. Linear mixed models on the log scale of hormones were utilized to evaluate the total effects of fiber intake. Inverse probability weights were utilized to estimate the independent effect of fiber on LH levels. In unweighted analyses, we observed a significant, inverse association between fiber intake (in 5 g/day increments) and log LH levels (beta, -0.051, 95% confidence interval (CI), -0.100, -0.002). No association was observed in the weighted analyses, after estradiol levels were taken into account (beta, -0.016, 95% CI, -0.060, 0.027). The decreased levels of LH associated with high fiber intake were attenuated after taking estradiol levels into account, suggesting that the association between fiber and LH is most likely a consequence of fiber's impact on estradiol and not due to an independent mechanism.