Scientific Evidence Suggests Vitamin D Supports Immune Functions

Research led by Professor Philip Calder from the University of Southampton England published in Nutrients listed vitamin D as one of the several nutrients flagged in the study for a well functioning immune system as an important factor to help protect against viral infections; vitamin C, zinc, and DHA omega-3 were also cited. 

Research from Trinity College Dublin suggested that vitamin D deficiency plays an important role in the severity of COVID-19 infections, statements in Alimentary Pharmacology and Therapeutics reads as follows: 

“... the evidence supporting a protective effect of vitamin D against severe COVID-19 disease is very suggestive, a substantial proportion of the population in the Northern Hemisphere will currently be vitamin D deficient, and supplements, for example, 1000 internationsl units (25 micrograms) per day are very safe.” “It is time for governments to strengthen recommendations for vitamin D intake and supplementation particularly when under lock-down.”

A new review authored by scientists from the Katholieke Universiteit Leuven Belgium published in Nutrients analyzed data from human studies as well as from in vitro to find that many in vitro studies used “ supra-physiological concentrations of 1,25-(OH)D2D3”, and that such doses are “probably not achievable with regular vitamin D supplements in humans, as these concentrations risk hypercalcemia and soft tissue calcifications.” 

According to the scientists the observed benefits of the in vitro studies have not translated well to human interventional studies for a variety of possibilities such as the doses used, timing of the supplements, and the duration of the interventions:

“... the timing of vitamin D intervention will be crucial. In animal models, vitamin D metabolites work best in a preventive setting, a time window that is often missed in human trials. Therefore, future randomized and controlled trials will be needed to investigate whether supplementation with regular vitamin D can indeed prevent or modify the course of inflammatory or autoimmune disease in at-risk subjects.” “For now, the botto, line on the effect of vitamin D in the immune system is that avoidance of severe vitamin D deficiency improves immune health and decreases susceptibility to autoimmune diseases.” 

Vitamin D refers to 2 biologically inactive precursors, D3 and D2 which are both transformed in the liver and kidneys into 25-hydroxyvitamin D (25(OH)D) which is the non-active storage form and the active form 1,25-dihydroxyvitamin D (1,25(OH)2D). 

The human body does manufacture vitamin D naturally with exposure to the sunshine on the skin, however, levels in some northern countries are very weak during winter months resulting in the body making no vitamin D at all; thus meaning that dietary supplements and fortified foods may be seen as an appropriate way in which to boost intake of vitamin D to support immune functions. 

Nutrients has published a good number of reports on vitamin D, including research from the University of Eastern Finland investigating which immune health related genes are regulated by 1,25(OH)2D3; findings from in vitro testing suggests that vitamin D targets genes with different immune supporting effects, most notably for acute response to infection, infection in general, and autoimmunity. 

“[W]e suggest that the highlighted 15 genes are the most relevant targets of vitamin D in the context of immunity and may be selected as biomarkers in clinical practice for the personalized diagnosis of the connection between vitamin D deficiency and immune related diseases.”