Does vitamin D help protect against Covid-19?

Older and darker-skinned people who are likely to have low levels of Vitamin D may benefit from supplementation of the essential vitamin to protect against severe symptoms of the coronavirus disease (Covid-19), according to a paper published in The Lancet. Clinicians, however, say that dosing on the vitamin in hope of being protected from the infection is a fallacy, as the best and only protection against infection remains hand-wash, wearing masks and social isolation.

Vitamin D is made by the skin on exposure to sunlight and is essential for bone growth and strength as it helps in the intestinal absorption of calcium, magnesium, and phosphate. This fat-soluble vitamin also modulates the immune response of white blood cells by preventing them from releasing too many inflammatory cytokines, which is what leads to the cytokine storm — a complication associated with Covid-19 and other disease such as severe acute respiratory syndrome (Sars) and middle-east respiratory syndrome (Mers). Cytokine storm is an acute immune reaction gone awry as the body starts destroying its own cells and tissues along with the virus.

Melanin, which gives skin the dark pigmentation, lowers the skin’s ability to make vitamin D on exposure to sunlight, with several studies showing that older adults with darker skin are more likely to be deficit in this essential vitamin. With social isolation forcing people to spend more time indoors, the deficiency of this vitamin may be increasing, said The Lancet study. Around 50% Indians are deficit in vitamin D, which is now found in some brands of fortified milk, including Mother Dairy. The overall prevalence of vitamin D deficiency in people living in urban Chennai was 55%, found a recent survey of 1,500 people published in the British Journal of Nutrition on March 26.

“Our study found that vitamin D deficiency was 63% in people with diabetes, 58% in people with pre-diabetes, and 80% in obese people, which is worrying because these are risk factors for Covid-19,” says Dr V Mohan, study co-author and chairman and chief of diabetology at Dr Mohan’s Diabetes Specialities Centre, which is a WHO Collaborating Centre for Noncommunicable Diseases Prevention and Control.

“Observational studies in the past have linked low levels of vitamin D and susceptibility to acute respiratory tract infections. Supplementation is inexpensive and the danger of side effects and toxicity are low when taken orally. The risk of toxicity is high for people with kidney and liver diseases as they may not be able to excrete the vitamin, so they should not take supplementation without prescription,” said Dr Mohan.

The Lancet paper cites vitamin D deficiency as one of the possible reasons for varying death rates across countries citing an observational study published in the journal Aging Clinical and Experimental Research that used data from 20 European countries. It noted that average vitamin D levels are low in Italy and Spain, which have experienced high Covid-19 death rates compared to north European countries, which have high average levels of vitamin D from the consumption of cod liver oil and vitamin D supplements, and possibly less sun avoidance.

“Vitamin D might help to reduce the inflammatory response to infection with Sars-CoV-2. Deregulation of this response… is characteristic of COVID-19 and degree of over-activation is associated with poorer prognosis. e,” according to The Lancet paper.

An observational correlation, however, does not mean causation, say experts. “Intervention trials have rarely shown benefits of vitamin D supplementation as treatment, except for muscular-skeletal disorders. Studies linking vitamin D supplementation to lung diseases like tuberculosis and COPD (chronic obstructive lung disease) have demonstrated no difference to clinical outcomes,” said Dr Nikhil Tandon, professor of endocrinology and metabolism at the All India Institute of Medical Sciences.

“Observational studies cannot be used to inform public policy and unless there is clinical data to show that it has a substantial affect on the outcomes of Covid-19, having it in the hope or anticipation that it will protect you against disease is pointless. It may bring you other benefits if you are deficit, but it will not stop you getting Covid-19 the way masks, handwashing and social isolation will,” said Dr Tandon.

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