Increasing serum 25-hydroxyvitamin D is associated with reduced odds of long menstrual cycles in a cross-sectional study of African American women

Increasing serum 25-hydroxyvitamin D is associated with reduced odds of long menstrual cycles in African American women. A growing body of evidence suggests that vitamin D is important for ovarian function.


Anne Marie Z. Jukic, Ph.D.correspondenceemail, Kristen Upson, Ph.D., Quaker E. Harmon, M.D., Ph.D., Donna D. Baird, Ph.D.



To examine the association between serum 25-hydroxyvitamin D [25(OH)D] and menstrual cycle length and regularity.


Community-based, cross-sectional study of serum 25(OH)D (adjusted for seasonal differences in timing of blood draw) and menstrual cycle length. Women aged 23–34 years reported their gynecologic history. Menstrual cycles were described with four independent categories (normal, short, long, irregular). We used polytomous logistic regression to estimate the association between a doubling of seasonally adjusted 25(OH)D and the odds of each cycle category.


Not applicable.


A total of 1,102 African American women.


Not applicable.

Main Outcome Measure(s)

Self-reported menstrual cycle length over the previous 12 months, excluding women who were using cycle-regulating medications over the entire year. Women who reported that their cycles were “too irregular to estimate” were classified as having irregular cycles. A typical cycle length of <27 days was considered “short,” >34 days was “long,” and 27–34 days was “normal.”


The median 25(OH)D level was 14.7 ng/mL (interquartile range, 10.9–19.6 ng/mL). A doubling of 25(OH)D was associated with half the odds of having long menstrual cycles: adjusted odds ratio (aOR) 0.54, 95% confidence interval (CI) 0.32–0.89. 25-Hydroxyvitamin D was not associated with the occurrence of short (aOR 1.03, 95% CI 0.82–1.29) or irregular (aOR 1.46, 95% CI 0.88–2.41) menstrual cycles. Results were robust to several sensitivity analyses.


These findings suggest that vitamin D status may influence the menstrual cycle and play a role in ovarian function. Further investigation of 25(OH)D and ovarian hormones, and prospective studies of 25(OH)D and cycle length, are needed.

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