What Do We Know About Vitamin D and Women’s Health?

Vitamin D, often referred to as the "sunshine vitamin," is a fat-soluble prohormone with vital roles in calcium metabolism and bone health. Originally discovered over a century ago during the study of rickets, vitamin D has since been recognized for its influence on both skeletal and nonskeletal functions. It is synthesized in the skin upon exposure to the ultraviolet B (UVB) rays in sunlight and can also be obtained through dietary sources including fatty fish, fortified foods and supplements. Despite its accessibility from natural sources, vitamin D deficiency remains widespread, affecting nearly 1 billion people globally.

The recommended daily intake of vitamin D varies depending on age and life stage, with adult women requiring 600–800 International Units (IU) per day (approx. 15-20 micrograms) to maintain optimal health. Risk factors for vitamin D deficiency include limited sun exposure, darker skin pigmentation, obesity and certain medical conditions such as chronic kidney disease or malabsorption disorders.

Vitamin D levels are increasingly being recognized as an important factor in women’s health, with emerging evidence showing correlations with hormonal balance, immune function and cellular health. Despite being underrepresented in medical research, the unique physiological demands of the female body – particularly during key life stages such as menstruation, pregnancy and menopause – highlight the need for adequate nutrient support. By influencing hormone regulation and supporting physiological adaptations, vitamin D acts as a lifelong ally throughout a woman’s life.

Vitamin D’s role in menstrual health

The menstrual cycle is driven by a complex balance of hormones that work together to support the female reproductive system. Estrogen and progesterone play leading roles, ensuring the cycle progresses smoothly and preparing the body for potential pregnancy. When this hormonal balance is disrupted, it can lead to irregular periods, painful symptoms or conditions such as polycystic ovary syndrome (PCOS). Recent research suggests that vitamin D may help maintain this balance, thereby reducing inflammation, supporting hormone regulation and improving the symptoms of certain menstrual disorders.

Maintaining hormonal balance

Vitamin D deficiency has been consistently linked to menstrual irregularities and hormonal imbalances. It is suggested this mechanism works due to vitamin D’s interaction with the vitamin D receptor present in ovarian and uterine tissues, which are key players in reproductive health. By modulating the hypothalamic-pituitary-ovarian axis (HPO), vitamin D helps regulate the production and activity of hormones like estrogen and progesterone, which are essential for maintaining regular menstrual cycles.  

A study from the Poznań University of Life Sciences, published in Nutrients, looked at the relationship between vitamin D status and the menstrual cycle in young women. The study measured blood serum vitamin D levels in a cohort of 77 participants, who also completed detailed medical questionnaires about their menstrual cycles. Those with low serum vitamin D levels (<30 ng/mL) were nearly 5 times more likely to experience menstrual disorders, including long cycles, oligomenorrhea (infrequent periods) and amenorrhea (absence of periods), compared to women with normal levels. Specifically, 40% of participants in the low vitamin D group reported long cycles, while only 12% in the normal group experienced such menstrual disturbances.

A cross-sectional study from the All India Institute of Medical Sciences, published in the International Journal of Reproductive BioMedicine, also investigated blood serum vitamin D levels with regard to menstrual cycle length and regularity in 166 women. They found a strong association between low vitamin D levels and irregular menstrual cycles. Vitamin D deficiency was also associated with a 13.3 times higher likelihood of experiencing cycle irregularities.

Alleviating period pain

Dysmenorrhea – or painful menstruation – is a common issue for women of reproductive age. Research suggests that vitamin D may alleviate menstrual pain through its anti-inflammatory effects by modulating prostaglandin levels – key mediators of inflammation and uterine contractions during menstruation. High levels of prostaglandins are associated with increased uterine muscle activity and pain in dysmenorrhea. Vitamin D is thought to reduce the synthesis of prostaglandins by inhibiting the expression of cyclooxygenase-2, the enzyme responsible for their production.

A randomized, double-blind trial investigated the impact of high-dose vitamin D supplementation (300,000 IU over 5 days) in women with vitamin D deficiency and primary dysmenorrhea. The study was published in BMC Women’s Health. The results showed a significant reduction in pain severity during two successive menstrual cycles. Additionally, women in the experimental group used less mefenamic acid, a pain-relief medication, compared to the control group. However, the supplementation had no effect on menstrual blood loss.

Vitamin D’s role in pregnancy

Vitamin D supports both maternal well-being and fetal development during pregnancy. It regulates calcium and phosphate metabolism, which is essential for building the baby’s skeleton, and influences maternal muscle health, reducing complications during delivery.

Improved delivery outcomes with vitamin D supplementation

In 2022, a study published in The Journal of Public Health, using results from the Maternal gestational vitamin D supplementation and offspring bone health (MAVIDOS) trial, explored the impact of daily vitamin D supplementation (1,000 IU) on pregnancy outcomes in 965 women.

The randomized, placebo-controlled study, conducted by the University of Southampton, revealed that women who received vitamin D were more likely to have a spontaneous vaginal delivery (65.6% vs. 57.9% in the placebo group). The vitamin D group also experienced less blood loss during delivery and fewer assisted deliveries.

“Most women want to have a ‘natural delivery’ of their baby. Our work suggests that taking extra vitamin D during their pregnancy might help them to achieve this,” said lead author Dr. Rebecca Moon a National Institute for Health and Care Research clinical lecturer in child health at the University of Southampton.

“Vitamin D deficiency is very common in the UK. We have also shown that extra vitamin D in pregnancy can improve the mother’s vitamin D level and has benefits to their child’s skeleton. Importantly, National Institute for Health and Care Excellence guidance recommends that all pregnant women take 400 IU vitamin D per day,” said corresponding author Dr. Nicholas Harvey, deputy director of the MRC Lifecourse Epidemiology Centre at the University of Southampton and lead of MAVIDOS.

Long-lasting benefits for child bone health

In a second follow-up study on the MAVIDOS trial, published in The American Journal of Clinical Nutrition, the researchers assessed the effect of maternal vitamin D supplementation on offspring bone health.

Moon and the team followed 454 children aged 6-7 years and found that those whose mothers received vitamin D during pregnancy had higher bone mineral density compared to children in the placebo group. These benefits persisted from early childhood (age 4) into mid-childhood, indicating a lasting impact on skeletal health.

“Our findings show that the benefits of vitamin D supplementation during pregnancy persist into mid-childhood. This early intervention represents an important public health strategy. It strengthens children’s bones and reduces the risk of conditions like osteoporosis and fractures in later life,” said Moon.

Vitamin D’s role in menopause

Menopause represents a pivotal transition in a woman’s life, characterized by hormonal changes that can impact bone health, cardiovascular function and overall quality of life. These changes are often accompanied by a higher risk of vitamin D deficiency due to reduced dietary intake, limited sun exposure and age-related shifts in metabolism. Vitamin D plays a vital role during menopause by supporting calcium absorption and preserving bone density.

A systematic review published in Nutrients examined 19 randomized clinical trials investigating vitamin D supplementation in postmenopausal women, with participants ranging from 51 to 78 years of age. Key findings from the analysis found vitamin D supplementation was effective in increasing serum 25-hydroxyvitamin D (25[OH]D) levels, which correlated with improvements in bone density and a reduction in osteoporosis-related risks. Higher doses of vitamin D, such as 300,000 IU administered as a single large dose or 1,000 IU taken daily, were found to be particularly effective in raising serum concentrations to optimal levels for bone health. Vitamin D supplementation also demonstrated potential in alleviating symptoms linked to menopause, such as muscle pain and weakness, and contributed to maintaining a better quality of life.

Advancing women’s health research

From menstruation to menopause, vitamin D has emerged as a key nutrient in supporting women’s health at different life stages. Its influence on hormonal regulation, inflammation and its ability to promote bone and muscle health underscores its importance in addressing the unique physiological challenges faced by women. Whether reducing menstrual pain, improving pregnancy outcomes or preserving bone density during menopause, vitamin D provides benefits that extend beyond its traditional role in calcium metabolism. With deficiency remaining prevalent worldwide, ensuring adequate vitamin D intake represents an essential and accessible strategy to enhance women’s overall well-being and quality of life.

References:

1. Łagowska K. The relationship between vitamin D status and the menstrual cycle in young women: A preliminary study. Nutrients. 2018;10(11):1729. doi: 10.3390/nu10111729
2. Singh V, Tamar N, Lone Z, Das E, Sahu R, Majumdar S. Association between serum 25-hydroxy vitamin D level and menstrual cycle length and regularity: A cross-sectional observational study. IJRM. Published online December 13, 2021. doi: 10.18502/ijrm.v19i11.9913
3. Amzajerdi A, Keshavarz M, Ghorbali E, Pezaro S, Sarvi F. The effect of vitamin D on the severity of dysmenorrhea and menstrual blood loss: a randomized clinical trial. BMC Women’s Health. 2023;23(1):138. doi: 10.1186/s12905-023-02284-5
4. Moon RJ, D’Angelo S, Crozier SR, et al. Does antenatal cholecalciferol supplementation affect the mode or timing of delivery? Post hoc analyses of the MAVIDOS randomized controlled trial. J Public Health. 2023;45(3):738-747. doi: 10.1093/pubmed/fdac160
5. Moon RJ, D’ Angelo S, Curtis EM, et al. Pregnancy vitamin D supplementation and offspring bone mineral density in childhood follow-up of a randomized controlled trial. Am J Clin Nutr. 2024;120(5):1134-1142. doi: 10.1016/j.ajcnut.2024.09.014
6. Hassanein MM, Huri HZ, Baig K, Abduelkarem AR. Determinants and effects of vitamin D supplementation in postmenopausal women: A systematic review. Nutrients. 2023;15(3):685. doi: 10.3390/nu15030685