We all grew up learning that a “regular” menstrual cycle was considered to be 28 days. Then, we all likely lived a very different experience. Some menstrual cycles may be shorter (less than 21 days), longer (anything 35 days or over), or just straight up sporadic.
Women who have polyendocrine metabolic ovarian syndrome or PMOS (the very recently updated name for PCOS) tend to have irregular cycles. PMOS affects an estimated 6% to 12% of women of reproductive age. It’s primarily characterized by hormonal imbalances, irregular ovulation, and yes, prolonged or unpredictable cycles. While there’s no single fix, new research suggests that vitamin D status may play a more significant role in menstrual regularity than previously understood.
Here’s what a new study reveals.
About the study
Researchers set out to examine whether vitamin D levels are associated with menstrual cycle patterns in women with PMOS. The cross-sectional study included 449 women diagnosed with the condition and analyzed their serum vitamin D concentrations alongside menstrual cycle data. Vitamin D deficiency is notably more prevalent in women with PMOS, which prompted researchers to investigate whether there’s a meaningful connection between the two.
Women with higher vitamin D levels had more regular cycles
The findings revealed that women with vitamin D deficiency (levels below 20 ng/mL) had significantly higher rates of prolonged menstrual cycles compared to those with sufficient levels (87.2% versus 70%).
The data also showed a dose-response relationship. For every 1 ng/mL increase in vitamin D, there was a 9% reduction in the risk of prolonged cycles. This association held even after adjusting for factors like age, BMI, and other metabolic markers.
Notably, the researchers identified a threshold effect. The benefits appeared to plateau once vitamin D levels reached approximately 28 ng/mL, suggesting that reaching this level may be enough to see benefits. This doesn’t mean that 28 ng/mL should be the goal level. After all, 30 ng/mL is considered the minimum adequate level for the vitamin and 50 ng/mL is considered optimal. It just means that correcting a vitamin D deficiency or insufficiency may be most important for this specific vitamin D benefit.
Why vitamin D matters for reproductive health
Vitamin D receptors are found throughout reproductive tissues, including the ovaries and uterus. The nutrient plays a role in hormone regulation, including the production and sensitivity of hormones involved in ovulation.
Women with PMOS tend to have higher rates of vitamin D deficiency, which may compound existing hormonal imbalances. Correcting a deficiency may support the body’s ability to regulate cycles more effectively.
RELATED READ: These Are The Best Vitamin D Supplements For Stubbornly Low Levels
How to optimize your vitamin D for cycle health
If you have PMOS and experience irregular periods, checking your vitamin D levels is a reasonable first step. A simple blood test (25-hydroxyvitamin D) can tell you where you stand. Ask your healthcare provider to add a vitamin D test to your next blood draw or opt for one of these at-home options.
The most effective way to increase vitamin D levels is with the help of a high-quality supplement. This one provides 5,000 IU of vitamin D in one serving (along with healthy fats like flaxseed oil, avocado oil, and extra virgin olive oil to enhance absorption).
The takeaway
New research on 449 women with PMOS found that higher vitamin D levels were associated with more regular menstrual cycles, with benefits plateauing around 28 ng/mL. If you’re managing this condition, testing your vitamin D and optimizing your levels may be a simple, evidence-based step to support cycle health.