Vitamin D and PCOS: The Essential Nutrient

Vitamin D has traditionally been recognized for its role in calcium metabolism. In more recent years, however, our appreciation for this vitamin has definitely evolved, and we now know that vitamin D does so much more than keep our bones strong.

From the prevention of type 2 diabetes, cardiovascular disease, hypertension, autoimmune conditions (such as type 1 diabetes and Hashimoto’s thyroiditis), and even cancer (1, 2), the sunshine vitamin shines through. An emerging theme in the vitamin D research is its effect on numerous gynecological conditions.

In particular, vitamin D has documented effects in PCOS, infertility, endometriosis (1), thyroid disorders (2), as well as breast and ovarian cancer (1). In this article, evidence for the role of vitamin D in PCOS will be explored.

Being Deficient in Vitamin D Makes PCOS Symptoms Worse

Vitamin D deficiency is often found in the general public, and women with PCOS may be even more affected (1, 5, 6, 8). In one study from Scotland, 11% of the control group of women, versus 44% of the women with PCOS were found to be severely vitamin D deficient (6). It is thought that vitamin D deficiency may exacerbate the symptoms of PCOS – particularly menstrual irregularity, insulin resistance and obesity (7).

Observational research has suggested that vitamin D status in women with PCOS may correlate with multiple metabolic risk factors (6, 8). A deficiency of vitamin D was found to correlate with poor scores for insulin sensitivity, HDL-C and the inflammatory marker CRP (6). In a different study, vitamin D levels were found to be the lowest in PCOS women with excess abdominal weight (8), again reinforcing a link between vitamin D and metabolic inflammation.

Studies Show That Supplementing Vitamin D Improves PCOS

Interventional studies have furthered this link. In one such intervention, women with PCOS were treated with a dose corresponding to just under 3, 000 IU of vitamin D per day for 6 months. By the 3-month mark, 30% of the women who had previously reported irregular cycles, noted improvements in menstrual frequency, and by the 6-month mark, 50% of the women had reported such improvements (5). In addition, triglyceride levels and fasting and post-challenge glucose levels were found to significantly improve by the end of the study (5), offering a potential mechanism for the improvement in menstrual regularity.

Another interventional study was conducted with overweight and obese women with vitamin D deficiency and PCOS (9). The women were divided into 4 groups and were given vitamin D (50, 000 IU per week), calcium (1000 mg per day), both vitamin D + calcium, or placebo for 8 weeks. Again a benefit to metabolic risk factors was found. In particular, it was the group who received co-supplementation of vitamin D plus calcium, which benefited the most – insulin scores and triglyceride levels were significantly improved in the co-supplementation group as compared to the other 3 groups (9).

Optimal Blood Levels of Vitamin D for Women With PCOS

Women with PCOS face a vast array of challenges ranging from inconsistent periods to weight loss resistance and inflammation. In North America where vitamin D deficiency is very prevalent, it is essential for women with PCOS to have their vitamin D levels checked and corrected when necessary.

Daily supplementation at 1,000 – 2, 000 IU per day is generally accepted, however a blood test to determine 25-OH vitamin D levels is the best way to establish sufficiency. Ideal 25-OH vitamin D levels should be maintained in the range of 100-200 nmol/L, through safe sun exposure and/or supplementation, where appropriate.


  1. Colonese F, Laganà AS, Colonese E, Sofo V, Salmeri FM, Granese R, Triolo O. The Pleiotropic Effects of Vitamin D in Gynaecological and Obstetric Diseases: An Overview on a Hot Topic. Biomed Res Int. 2015;2015:986281.
  2. Wang J, Lv S, Chen G, Gao C, He J, Zhong H & Xu Y. Meta-analysis of the association between vitamin D and autoimmune thyroid disease. Nutrients. 2015;7:2485-98.
  3. Krul-Poel YHM, Snackey C, Louwers Y, Lips P, Lambalk CB, Laven JSE and Simsek S. The role of vitamin D in metabolic disturbances in polycystic ovary syndrome: a systematic review. Eur J Endocrinol 2013;169:853-65.
  4. Wehr E, Trummer O, Giuliani A, Gruber HJ, Pieber TR & Obermayer-Pietsch. Vitamin D-associated polymorphisms are related to insulin resistance and vitamin D deficiency in polycystic ovary syndrome. Eur J Endocrinol 2011;164:741-9.
  5. Wehr E, Pieber TR & Obermayer-Pietsche B. Effect of vitamin D3 treatment on glucose metabolism and menstrual frequency in polycystic ovary syndrome women: A pilot study. J Endocrinol Invest 2011;34:757-63.
  6. Li HWR, Brereton RE, Anderson RA, Wallace AM & Ho CKM. Vitamin D deficiency is common and associated with metabolic risk factors in patients with polycystic ovary syndrome. Metabolism 2011;60:1475-81.
  7. Thomson RL, Spedding S, Buckley JD. Vitamin D in the aetiology and management of polycystic ovary syndrome. Clin Endocrinol 2012;77:343-50.
  8. Kozakowski J, Kapuścińska R, Zgliczyński W. Associations of vitamin D concentration with metabolic and hormonal indices in women with polycystic ovary syndrome presenting abdominal and gynoidal type of obesity. Ginekol Pol 2014;85:765-70.
  9. Asemi Z, Foroozanfard F, Hashemi T, Bahmani F, Jamilian M, Esmaillzadeh A. Calcium plus vitamin D supplementation affects glucose metabolism and lipid concentrations in overweight and obese vitamin D deficient women with polycystic ovary syndrome. Clin Nutr. 2014; S0261-5614(14)00243-X.