Introduction: The invisible transition and the role of Vitamin D

Perimenopause represents a profound biological transition in a woman's life, characterized by erratic fluctuations in estrogen and progesterone levels. While traditional clinical focus has been on managing hot flashes and preventing osteoporosis, modern scientific research is revealing that vitamin D—technically a prohormone rather than a vitamin—plays a central role in mitigating a wide range of symptoms and risks associated with this period.

Vitamin D is often described as the "glue" that maintains bone health through calcium homeostasis. However, the presence of Vitamin D Receptors (VDRs) in nearly all tissues of the human body, including the brain, cardiovascular system, adipose tissue, and immune cells, suggests that its influence is pleiotropic. For perimenopausal women, optimizing 25-hydroxyvitamin D [25(OH)D] levels is not only a strategy against future fractures but also a first-rate metabolic, immunological, and neuropsychiatric intervention.

Beyond calcium: Vitamin D as a pleiotropic prohormone

The vitamin D endocrine system interacts in a complex way with the hypothalamic-pituitary-gonadal axis. During perimenopause, the drop in estrogen levels reduces the expression of VDR receptors in the intestine, decreasing the efficiency of calcium absorption, even with adequate dietary intake. But the impact goes far beyond that.

Genomic studies have shown that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], the active form of the vitamin, regulates the expression of more than 200 genes. In mature women, this gene regulation is critical for maintaining endothelial barrier integrity and insulin sensitivity. Therefore, we must stop viewing it as simply a nutrient for bones and begin considering it a systemic modulator of women's health.

Impact on Metabolic Health and Body Composition

One of the most frustrating changes for women in perimenopause is the redistribution of body fat to the abdominal area and the increased difficulty in maintaining lean muscle mass. This is where Vitamin D emerges as an unexpected ally.

Insulin resistance and risk of type 2 diabetes

Perimenopause is frequently associated with decreased insulin sensitivity. Research published in journals such as The Journal of Clinical Endocrinology & Metabolism It indicates that Vitamin D improves the function of pancreatic beta cells and reduces systemic inflammation, a key factor in the pathogenesis of insulin resistance.

Vitamin D acts directly on insulin secretion by binding to pancreatic VDRs and facilitating the conversion of proinsulin to insulin. In perimenopausal women, low levels of 25(OH)D have been significantly correlated with a higher HOMA-IR index, suggesting that deficiency may accelerate the transition to metabolic syndrome (Chacko et al., 2016).

Prevention of sarcopenia and maintenance of muscle strength

Sarcopenia, or the loss of muscle mass and strength, begins to accelerate with the decline in estradiol. Vitamin D is essential for muscle protein synthesis and the growth of type II (fast-twitch) muscle fibers, which are the first to atrophy with age.

A meta-analysis of randomized controlled trials showed that vitamin D supplementation in middle-aged women improves not only handgrip strength but also balance, thus reducing the risk of falls even before bone mineral density is severely compromised. The interaction between vitamin D and mitochondrial function in muscle tissue is a vibrant area of study that underscores its metabolic importance.

Cardiovascular Health: Protecting the Heart in Old Age

Before menopause, women enjoy relative cardiovascular protection thanks to estrogen. However, during perimenopause, the lipid profile tends to worsen, and blood pressure may begin to rise. Vitamin D plays a crucial role in regulating the renin-angiotensin-aldosterone system (RAAS).

Vitamin D deficiency has been associated with activation of the renin-angiotensin-aldosterone system (RAAS), which can lead to hypertension and arterial stiffness. Furthermore, vitamin D has potent anti-inflammatory effects on the vascular endothelium, reducing the expression of pro-inflammatory cytokines such as IL-6 and TNF-alpha, which are silent drivers of atherosclerosis (Holick, 2017). Maintaining optimal vitamin D levels is therefore a fundamental component of primary prevention of cardiovascular disease in mature women.

Neurosteroids and Emotional Wellbeing

Brain fog, anxiety, and depressive symptoms are common during the menopausal transition. Vitamin D acts in the brain as a neurosteroid.

The connection between serotonin and mood

Vitamin D activates the expression of the enzyme tryptophan hydroxylase 2 (TPH2), which converts the amino acid tryptophan into serotonin in the brain. Since serotonin is the primary neurotransmitter for well-being and mood regulation, low levels of vitamin D can exacerbate emotional vulnerability induced by hormonal fluctuations (Patrick & Ames, 2014).

Many observational studies have linked vitamin D deficiency to a higher incidence of depression in midlife. Although supplementation does not replace psychological or pharmacological treatment when necessary, ensuring sufficient levels is a biological prerequisite for emotional stability.

Sleep quality and circadian rhythms

Insomnia is one of the most common complaints during perimenopause. Vitamin D receptors are located in brain areas involved in sleep regulation, such as the hypothalamus. Recent research suggests that vitamin D is involved in melatonin signaling pathways and in regulating the sleep-wake cycle. Correcting low vitamin D levels has been associated with improved sleep latency and reduced sleep fragmentation, which is vital for cognitive and physical recovery.

Immune Function and Autoimmunity in the Menopausal Transition

A woman's immune system is particularly sensitive to hormonal changes. There is an increased incidence of autoimmune diseases and low-grade inflammation during perimenopause. Vitamin D is an immunomodulator that promotes the differentiation of regulatory T cells (Tregs), which are responsible for preventing excessive immune responses.

In a context where "inflammaging" (inflammatory aging) is becoming increasingly relevant, vitamin D acts as a natural brake against the release of pro-inflammatory cytokines, helping to maintain a resilient and balanced immune system.

Risk factors and level optimization

Not all women process vitamin D in the same way. Factors such as geographic latitude, skin pigmentation, body mass index (BMI), and sunscreen use drastically influence endogenous synthesis.

How to measure and what levels to look for?

The only accurate way to know your vitamin D status is through a 25-hydroxyvitamin D blood test. Although laboratories often consider any value above 20-30 ng/mL to be "normal," many integrative medicine and endocrinology societies suggest that for extra-skeletal benefits (metabolism, immunity, mood), the optimal range should be between 40 and 60 ng/mL.

Sources: Sun, diet and smart supplementation

Skin synthesis through sun exposure remains the primary source, but in many regions and with modern lifestyles, it is insufficient for much of the year. Dietary sources are limited (fatty fish, egg yolk, UV-exposed mushrooms), so supplementation often becomes necessary.

It is essential that supplementation be personalized and, preferably, accompanied by Vitamin K2 and Magnesium. Vitamin K2 directs calcium to the bones and prevents its deposition in the arteries, while magnesium is an essential cofactor for the enzymes that activate vitamin D in the liver and kidneys.

Conclusion: An integrative approach for the modern woman

Perimenopause should not be viewed as a decline, but rather as a phase of recalibration. In this new stage, Vitamin D emerges not only as a protector of bone structure, but also as a guardian of metabolic, mental, and cardiovascular health. A proactive approach, including regular measurements and a solid nutritional strategy, allows women to navigate this stage with greater vitality and a lower risk of chronic diseases.

Optimizing vitamin D intake is a fundamental act of self-care. However, nutrition is a complex puzzle where every piece counts. For accurate monitoring of your micronutrient needs and dietary planning tailored to the changes of perimenopause, we recommend using CalooCaloo offers personalized diets and tracking tools that will help you maintain your vitamin D levels and other key nutrients in optimal ranges, ensuring a healthy and empowered transition to menopause.

Bibliographic References

• Chacko, S.A., et al. (2016). Vitamin D receptor, retinoid X receptor, and vitamin D-binding protein gene polymorphisms in relation to types 2 diabetes and metabolic syndrome. The Journal of Clinical Endocrinology & Metabolism.
• Holick, M.F. (2017). The vitamin D deficiency pandemic: Approaches for diagnosis, treatment and prevention. Reviews in Endocrine and Metabolic Disorders.
• Patrick, R.P., & Ames, B.N. (2014). Vitamin D hormone regulates serotonin synthesis. Part 1: relevance to autism. FASEB Journal.
• Santoro, N., et al. (2015). The Menopausal Transition: Role of Adiposity and Weight Change. Obstetrics and Gynecology Clinics of North America.
• Vitamin D and Menopause. (2021). The North American Menopause Society (NAMS).
• Gielen, E., et al. (2011). Musculoskeletal effects of vitamin D in the elderly. Journal of Bone and Mineral Research.
• Manson, J.E., et al. (2019). Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease (VITAL study). New England Journal of Medicine.