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.