PCOS risk is reduced with higher levels of vitamin D in the blood

PCOS, also known as polycystic ovary syndrome, is one of the most common hormonal disorders and can lead to infertility, male-pattern hair growth, weight gain, impaired blood sugar regulation, and an increased risk of cardiovascular disease, type 2 diabetes, and autoimmune diseases. Evidence suggests that higher blood levels of vitamin D reduce the risk of developing PCOS. This is shown in a large population-based study published in Frontiers in Nutrition, in which the authors also examine the role of vitamin D in hormonal balance, blood sugar regulation, circulation, and fertility.

PCOS is characterized by polycystic ovaries, where the ovaries contain many small follicles. The symptoms are caused by hormonal imbalances, leading to irregular or absent menstruation, infertility, unstable blood sugar, weight gain, and fatigue. Elevated levels of male sex hormones can cause acne and male-pattern hair growth (hirsutism).
One of the underlying causes of PCOS is that cells become resistant to the hormone insulin, which reduces glucose uptake and leads to elevated insulin levels. These hormonal disturbances are also accompanied by oxidative stress and chronic inflammation, increasing the risk of cardiovascular disease, type 2 diabetes, and autoimmune diseases.
PCOS affects an increasing number of women. Since diet and lifestyle play a crucial role, the researchers behind the new study wanted to examine whether widespread vitamin D deficiency increases the risk, and what role vitamin D plays in sex hormone balance, blood sugar regulation, and inflammation, among other factors.

• PCOS is associated with many symptoms and reduced quality of life
• PCOS is estimated to account for infertility in 30% of cases

The higher the vitamin D level in the blood, the lower the risk of PCOS

The new study included 1,397 women. Subgroup analyses were used to examine how age, BMI, and marital status influence the relationship between vitamin D levels and the risk of developing PCOS. The study found that blood levels of vitamin D were inversely associated with the risk of PCOS. In other words, the lower the vitamin D level in the blood, the higher the risk of developing the condition. This association was also stronger in women over 40 and in overweight women with a BMI over 30. There was also a stronger association among women who were divorced or widowed.
The researchers therefore conclude that higher blood levels of vitamin D can be considered an independent factor associated with a lower risk of developing PCOS. This applies to all women, and especially to overweight women over 40 and women without a spouse or partner.

How does vitamin D protect against PCOS?

Most of the body’s cells have receptors for the active form of vitamin D, which is considered a steroid hormone. It is well known that vitamin D plays a role in calcium absorption and bone health. Vitamin D’s protective mechanisms against PCOS include:

• Activation and regulation of genes
• Insulin secretion and insulin sensitivity
• Immune function and regulation of inflammation
• Regulation of enzymes that influence sex hormones

Why is vitamin D deficiency so widespread?

Sun exposure is the most important source of vitamin D, which the body produces from a cholesterol precursor in the skin. However, limited sun exposure during the winter months, sun avoidance, sunscreen use, darker skin, and cholesterol-lowering statins all contribute to reduced vitamin D production. Overweight individuals and people with diabetes also appear to have an increased need due to metabolic disturbances, making it more difficult for them to utilize or activate vitamin D from sunlight or supplements. In addition, genetic factors may increase the need.

How much vitamin D do women of reproductive age need?

Official recommendations for women of reproductive age are 5–10 micrograms per day. However, there is no guarantee that these recommendations optimize blood levels, which should ideally be above 75 nmol/L.
It may therefore be beneficial to have your blood levels of vitamin D measured, to get safe and responsible sun exposure during the summer without burning, and to take appropriate supplements during the winter months - or year-round - if one wants to help prevent PCOS or support treatment.
As shown, vitamin D needs can vary significantly between individuals. According to EFSA, the upper safe limit for supplementation is 100 micrograms per day. This is not more than what most people with light skin can produce from sun exposure on a summer day while wearing light clothing.

Complementary treatment and blood sugar regulation

In the following article, you can read more about the importance of regulating blood sugar in the prevention and treatment of PCOS. It may therefore be relevant to limit carbohydrates (especially refined carbohydrates) and to focus more on getting enough protein and healthy, unprocessed fats at each main meal. Supplementation with chromium may also be considered, as it improves insulin sensitivity, helps promote satiety, and may make it easier to lose excess weight.

• Chromium supplementation has therapeutic effects in PCOS

References:

Yuling Liu et al. Association between serum vitamin D levels and polycystic ovary syndrome: a cross-sectional study. Frontiers in Nutrition 2026

Mohammed Hamsho et al. Therapeutic effects of chromium supplementation on women with polycystic ovarian syndrome: A systematic review and meta-analysis. Endocrinology, Diabetes y Nutrition 2025.