Vitamin D and its significance have been well documented, especially for its impact on bone health. What may be less known is its role outside of our skeletal system. Results from several observational studies have shown that optimal vitamin D status plays a vital role and impacts the extra-skeletal system. It has been associated with a lower risk of heart disease, diabetes, respiratory infections, and lung function, among others.1
Statistics show that the prevalence of vitamin D deficiency ranges from 80-90% and is prevalent across all age-groups and risk-groups alike.2 Current guidelines suggest that vitamin D is an indispensable nutrient. When endogenous synthesis is significantly impaired, the requirements may need to be fulfilled by daily vitamin D supplementation.
Data from various studies suggest that vitamin D is extremely important for the proper functioning of the immune system, the body’s first-line defence against infecons. Besides, vitamin D has both anti-inflammatory and immunoregulatory properties; they are essential to get the defence mechanisms of the body up and running.3
Several studies have confirmed that lower levels of vitamin D are associated with an increased risk of infections, including influenza. In a study conducted in Japan, children supplemented with daily vitamin D for 15 weeks during the winter season showed a significant reduction in the incidence of influenza.4
Vitamin D modulates both innate as well as adaptive immune systems. It enhances immune cell function which also includes T cells and macrophages that protect the body against pathogens. In fact, vitamin D plays a vital role in autoimmunity too. A deficiency of vitamin D is conspicuous in patients suffering from autoimmune diseases, viz., inflammatory bowel disease, rheumatoid arthritis, lupus, etc.5
Several studies have suggested a potential link between vitamin D levels and various respiratory illnesses. Vitamin D prevents, or works, against viral infections in two ways. First, it induces the production of antiviral peptides in the respiratory epithelium that strengthens the mucosal defence. Second, it reduces the cytokine storm by enhancing the innate immune system and suppressing the overactivation of the adaptive immune system that tackles the viral load. Also, vitamin D may block the production of pro-inflammatory cytokines such as TNF-alpha and interleukin-6 that are usually in higher concentrations among patients suffering from Covid-19.6
Vitamin D has been linked to better outcomes in fertility. It plays an essential role in both male and female reproductive functions. Vitamin D improves ovarian stimulation and semen quality. There is evidence that vitamin D exerts certain effects on female reproduction including IVF, PCOS and endometriosis.7 A study of 84 infertile women undergoing IVF showed that women with higher levels of vitamin D in serum and follicular fluid had significantly higher chances of achieving clinical pregnancy following IVF. There is also evidence that vitamin D deficiency may be involved in pathogenesis of insulin resistance and metabolic syndrome associated with PCOS.8
There is an important, yet little known function of vitamin D - the regulation of the function and development of the nervous system. Vitamin D’s neuroprotective effect influences neurotrophin production and release, neuromediator synthesis, protection of nervous issues from oxidative damage and calcium homeostasis.9 Vitamin D ensures calcium homeostasis in the brain and acts as a neuroprotective agent.10 It is reported that vitamin D in brain tissue can modulate calcium-binding proteins that are widely distributed in both adult and foetal brains. Each of these proteins has
a unique action and effect during development and ageing.
Studies have confirmed that low vitamin D levels may play a vital role in coronary artery disease, congestive heart failure, stroke, hypertension, etc. In a study published in Heart and Lung Circulation, vitamin D was able to block the action of cardiac colony-forming fibroblasts (cCFU-Fs), which prevent scar tissue build-up and stop blockage from developing.11
Vitamin D is critical for several functions, including the regulation of the immune system and prevention and management of several disease conditions. There is also enough evidence that vitamin D is vital to extra-skeletal function.
1 Amrein, K., Scherkl, M., et al., 2020. Vitamin D deficiency 2.0: an update on the current status worldwide. European Journal of Clinical Nutrition, 74(11), pp.1498-1513.
2 Aparna, P. and Muthalal, S.,et al., 2018. Vitamin D deficiency in India. Journal of Family Medicine and Primary Care, 7(2),pp.324-330
3 Prietl, B., Treiber, G., Pieber, T. and Amrein, K., 2013. Vitamin D and Immune Function. Nutrients, 5(7), pp.2502-2521.
4 Urashima, M., Segawa, T., Okazaki, M., Kurihara, M., Wada, Y. and Ida, H., 2010. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. The American Journal of Clinical Nutrition, 91(5), pp.1255-1260.
5. Di Rosa, M., Malaguarnera, M., Nicoletti, F. and Malaguarnera, L., 2011. Vitamin D3: a helpful immunomodulator. Immunology, 134(2), pp.123-139.
6. Kaler, J., Hussain, A., Azim, D., Ali, S. and Nasim, S., 2021. Optimising vitamin D levels in patients with COVID-19. Hong Kong Medical Journal,.
7. Fung, J., Hartman, T., Schleicher, R. and Goldman, M., 2017. Association of vitamin D intake and serum levels with fertility:results from the Lifestyle and Fertility Study. Fertility and Sterility, 108(2), pp.302-311.
8. Lerchbaum, E. and Obermayer-Pietsch, B., 2012. MECHANISMS IN ENDOCRINOLOGY: Vitamin D and fertility: a systematic review. European Journal of Endocrinology, 166(5), pp.765-778
9. Wrzosek,M.,Lukaszkiewicz,J.,Wrzosek,M., Jakubczyk, A.,Matsumoto,H.,Piatkiewicz,P.,Radziwon-Zaleska,M.,Wojnar, M. and Nowicka, G., 2013.Vitamin D and the central nervous syetem.Pharmacological Reports, 65(2), pp.271-278.
10. Farghali, M., Ruga, S., Morsanuto, V. and Uberti, F., 2022. Can Brain Health Be Supported by Vitamin D-Based Supplements? A Critical Review.
11. Le, T., Ogawa, M., Kizana, E., Gunton, J. and Chong, J., 2018. Vitamin D Improves Cardiac Function After Myocardial Infarction Through Modulation of Resident Cardiac Progenitor Cells. Heart, Lung and Circulation, 27(8), pp.967-975