A new meta-analysis of randomized controlled trials (RCTs) published in the journal Complementary Therapies in Clinical Practice found vitamin D supplementation helped regulate menstrual cycle and improve follicular development among women with polycystic ovary syndrome (PCOS).
PCOS develops when a hormonal imbalance prevents the follicles from releasing the egg during ovulation. Individuals with PCOS may experience a variety of symptoms including infertility, irregular periods, ovarian cysts, pelvic discomfort, weight gain and abnormal hair growth on the body.
PCOS is the most prevalent endocrine disorder affecting women of reproductive age, with over 5 million individuals diagnosed in the US alone. Additionally, those with PCOS are at a significantly increased risk for developing high blood pressure, cardiovascular disease, sleep apnea and diabetes.
Research suggests vitamin D may play an important role in reproductive health. Due to the presence of vitamin D receptors throughout the ovaries and endometrium, researchers theorize that vitamin D may act locally to regulate the function of these organs. Vitamin D deficiency is highly prevalent in women with PCOS, with 67% – 85% of patients below 20 ng/ml.
Researchers have evaluated the role of vitamin D supplementation for the treatment of PCOS symptoms. However, due to the small sample sizes and variable markers used to evaluate the health outcome, this relationship remains unclear. Therefore, researchers recently conducted a meta-analysis of RCTs to determine whether vitamin D supplementation may provide a treatment effect among women with PCOS.
The researchers included studies in the analysis if they met the following criteria:
- The study must be a RCT.
- The women enrolled in the study received a strict diagnosis of PCOS based off the Rotterdam European Society of Human Reproduction and Embryology (ESHRE)/American Society of Reproductive Medicine (ASRM) or National Institute of Child Health and Human Development (NICHD) criteria.
- The study compared vitamin D supplementation to placebo or metformin, a commonly used PCOS medication.
- The study did not report on other diseases related to the condition.
Of the 463 studies on this topic, 9 studies met this criteria and thus were included in the analysis. A total of 6 studies compared the effects of vitamin D supplementation to placebo, while the remaining 3 compared vitamin D to metformin. The vitamin D dosage varied widely between the studies, ranging from 400 IU – 12,000 IU/day. The frequency of regular menstrual cycles and dominant follicles at baseline were similar among all studies. A dominant follicle grows faster than other follicles in preparation for ovulation. The researchers considered the follicle dominant if it were more than 14mm in diameter. Menstrual cycles were considered regular if they appeared every 25-35 days.
The researchers found that vitamin D supplementation was associated with a 2.34 increased odds of developing dominant follicles (p = 0.001). Patients who received the combination of metformin and vitamin D experienced a 1.85 increased odds of experiencing improved regularity of menstrual cycles (p = 0.05).
The researchers concluded,
“Evidence from available RCTs suggests vitamin D supplementation may be beneficial for follicular development and menstrual cycle regulation in patients with PCOS.”
They went on to state,
“Additional high quality RCTs are required to confirm the effectiveness of of vitamin D on PCOS.”
Sturges, M. & Cannell, JJ. Meta-analysis finds vitamin D supplementation may improve the severity of polycystic ovary syndrome. The Vitamin D Council Blog & Newsletter. 2/2/2017
Fang, F. et al. Effect of vitamin D supplementation on polycystic ovary syndrome: A systematic review and meta-analysis of randomized controlled trials. Complementary Therapies in Clinical Practice, 2017.