News articles since the start of the COVID-19 pandemic have hypothesised that you are more likely to suffer severe COVID-19 if your levels of vitamin D are low. Although more research must still be done, there is a striking overlap between risk factors for severe COVID-19 and vitamin D deficiency, including obesity, older age, and black or Asian ethnic origin.

The Lancet reports that the ‘interest in a potential role for vitamin D in the prevention or treatment of acute respiratory infections dates back to the 1930s, when cod liver oil was investigated as a means to reduce industrial absenteeism due to the common cold. Meta-analyses of randomised controlled trials conducted from 2007–20 reveal protective effects of vitamin D against acute respiratory infections, albeit these effects were of modest size and with substantial heterogeneity.’

Vitamin D is made in the skin with the help of sunlight. It has several important functions, including helping to regulate calcium and phosphate in the body to keep bones and teeth healthy. It is also important for good overall health and is an important factor in making sure your muscles, heart, lungs, brain and immune system work well. Vitamin D is particularly important in children, pregnant and breastfeeding women. In recent years, studies have linked vitamin D deficiency to a growing number of health concerns including heart disease, multiple sclerosis, Parkinson’s disease, stroke, diabetes, osteoporosis, prostate disease, some autoimmune conditions and depression.

Sunlight is our main source of vitamin D and requires bare skin and direct sunlight to work, however from October to April, 90% of the UK lies above the latitude that permits exposure to enough ultraviolet B light necessary for vitamin D synthesis. You can also get vitamin D from supplements and a small number of foods such as liver, oily fish and eggs are also good source of vitamin D, however, you would need to eat an enormous amount to keep your levels in the desired range. The farmed fish typically consumed in the UK may contain less vitamin D content than wild fish and in the UK, cows’ milk is generally not a good source of vitamin D because it isn’t fortified as it is in other countries. However, most people should be able to get all the vitamin D they need by eating a healthy balanced diet and by getting some summer sun. A simple blood test can be used to diagnose vitamin D deficiency and it can be treated with supplements.


The Lancet reports that, ‘A number of hospital-based treatment trials have been registered to date, but it may prove challenging to detect a signal for vitamin D supplementation in severe COVID-19 for two reasons. First, patients tend to present to hospital in the hyperinflammatory stage of the disease, so it might be too late for them to benefit from any antiviral effects induced by vitamin D supplementation. Second, it could be hard to show the effect of a micronutrient over and above dexamethasone, which has potent anti-inflammatory actions and now represents the standard of care in severe disease. Prevention of SARS-CoV-2 infection also represents an ambitious target, given the highly infectious nature of the pathogen.’ More research is certainly needed and official bodes such as the Scientific Advisory Committee on Nutrition and the National Institute for Health Care and Excellence (NICE) are reviewing the role of vitamin D in the context of respiratory infections and coronavirus.

We know from analysis of our blood results at Preventicum that vitamin D deficiency is very common in our clients who often work long hours indoors and many people are severely deficient particularly at this time of the year. Public Health England say, ‘There is no evidence to support taking vitamin D supplements to specifically prevent or treat COVID‑19. However, all people should continue to follow UK Government advice on daily vitamin D supplementation to maintain bone and muscle health during the COVID‑19 pandemic’. To protect bone and muscle health, the UK Government advises that everyone needs vitamin D equivalent to an average daily intake of 10 micrograms (400 international units) during the autumn and winter months. They also advise that people whose skin has little to no exposure to sunlight and ethnic minority groups with dark skin, from African, Afro-Caribbean and South Asian backgrounds, should consider taking a vitamin D supplement all year round. This advice would also apply to people whose skin has little to no exposure to sunlight because they are indoors shielding or self-isolating. At the time of writing this article, scientists at Queen Mary Hospital  have launched a major new trial to discover whether the rrisks from the virus can be reduced by taking vitamin D, they are seeking over 5,000 people to take part in the trial over the winter months. On 15th October 2020, Health Secretary, Matt Hancock also urged people to take vitamin D to help boost their overall health amid mounting evidence it can protect against Covid-19.


The Lancet

Public Health England

The British Heart Foundation