To determine the effect of cinnamon on menstrual cyclicity and metabolic dysfunction in women with polycystic ovary syndrome (PCOS).

In a prospective, placebo controlled, double-blinded randomized trial, 45 women with PCOS were randomized (1:1) to receive cinnamon supplements (1.5 g/d) or placebo for 6 months. Menstrual cyclicity (average cycles/month) during the 6 months study period was compared between the 2 groups using the Mann-Whitney U test. Changes in menstrual cyclicity and insulin resistance between baseline and the 6 month study period were compared between the 2 groups using Wilcoxon signed rank tests.

The 45 women were randomized, 26 women completed 3 months of the study, and 17 women completed the entire 6 months of the study. During the 6 month intervention, menstrual cycles were more frequent in patients taking cinnamon compared with patients taking placebo (median, 0.75; interquartile range, 0.5−0.83 vs median, 0.25; interquartile range, 0−0.54; P = .0085; Mann Whitney U). In patients taking cinnamon, menstrual cyclicity improved from baseline (+ 0.23 cycles/month 95% confidence interval, 0.099−0.36), yet did not improve for women taking placebo. (P = .0076, Wilcoxon signed rank). Samples (n = 5) of serum from the luteal phase in different patients within the cinnamon group were thawed and ovulatory progesterone levels (>3 ng/mL) confirmed. Luteal phase progesterone levels (>3 ng/mL, n = 5) confirmed ovulatory menses. Measures of insulin resistance or serum androgen levels did not change for either group.

These preliminary data suggest that cinnamon supplementation improves menstrual cyclicity and may be an effective treatment option for some women with PCOS.