The scientists from the UK, Europe and USA, including experts from the University of Birmingham, have published a consensus paper in the journal 'BMJ, Nutrition, Prevention and Health' warning against the use of 'mega doses' of vitamin D for preventing or treating the virus.
Several studies published over the passed couple of months have noted a link between vitamin D deficiency and COVID-19 mortality, with several concluding that daily supplementation could help reduce virus severity.
But the current paper takes issue with reports concluding that doses higher than the safe upper limit of 4,000IU/d could reduce the risk of contracting the virus and be used to successfully treat it.
The report states: "Popular information channels, such as social media platforms, have been rife with misinformation that has been perpetuated by fear and uncertainty. This has been the case particularly for diet and lifestyle advice."
It notes a number of reports including one named 'Evidence that Vitamin D Supplementation Could Reduce Risk of Influenza and COVID-19 Infections and Deaths' published in 'Nutrients' which concludes: "To reduce the risk of infection, it is recommended that people at risk of influenza and/or COVID-19 consider taking 10,000 IU/d of vitamin D3 for a few weeks to rapidly raise 25(OH)D concentrations, followed by 5,000 IU/d.
"The goal should be to raise 25(OH)D concentrations above 40–60 ng/mL (100–150 nmol/L). For treatment of people who become infected with COVID-19, higher vitamin D3 doses might be useful. Randomised controlled trials and large population studies should be conducted to evaluate these recommendations..."
The current study warns that calls to use high-dose supplementation to treat or prevent the virus are 'without support from pertinent studies in humans at this time, but rather based on speculations about presumed mechanisms'.
"As a key micronutrient, vitamin D should be given particular focus—not as a ‘magic bullet’ to beat COVID-19, as the scientific evidence base is severely lacking at this time—but rather as part of a healthy lifestyle strategy to ensure that populations are nutritionally in the best possible place," the report states.
"Anyone who is self-isolating with limited access to sunlight is advised to take a vitamin D supplement according to their government’s recommendations for the general population (ie, 400 IU/day for the UK and 600 IU/day for the USA (800 IU for >70 years)) and the European Union (EU).
"There is no strong scientific evidence to show that very high intakes of vitamin D will be beneficial in preventing or treating COVID-19. There are evidenced health risks with excessive vitamin D intakes especially for those with other health issues such as a reduced kidney function."
Study co-author Professor Carolyn Greig, from the University of Birmingham, adds: “Although there is some evidence that low vitamin D is associated with acute respiratory tract infections, there is currently insufficient evidence for vitamin D as a treatment for COVID-19 and over-supplementing must be avoided.”
The report states that findings from the majority of studies looking into vitamin D's efficacy for respiratory infections have been based on data gathered from population groups in developing countries and cannot be extrapolated to populations from more developed countries due to external factors.
Professor Sue Lanham-New, Head of the Department of Nutritional Sciences at the University of Surrey and lead author of the study, warns that over supplementation can be very harmful.
“An adequate level of vitamin D in the body is crucial to our overall health, too little can lead to rickets or the development of osteoporosis but too much can lead to an increase in calcium levels in the blood which could be particularly harmful.”
Professor Judy Buttriss, Director General British Nutrition Foundation and also a co-author of the paper adds: “In line with the latest Public Health England guidance on vitamin D, we recommend that people consider taking a vitamin D supplement of 10 micrograms a day during the winter months (from October to March), and all year round if their time outside is limited.
“Levels of the vitamin in the body can also be supplemented through a nutritionally balanced diet including foods that provide the vitamin, such as oily fish, red meat, egg yolk and fortified foods such as breakfast cereals, and safe sunlight exposure to boost vitamin D status.”
Dr William Grant, the lead author of the aforementioned study recommending high doses of vitamin D, has argued in a pre-print follow-up article sent to NutraIngredients, that the study's recommendations were based on reaching a serum 25(OH)D concentration between 40 and 60 ng/ml in advance of the winter viral respiratory tract infection (RTI) season. He argues that evidence has shown that, when starting near 20 ng/ml, it takes about 35 days to reach 60 ng/ml with 10,000 IU/d and 85 days with 4000 IU/d.
"We strongly disagree that vitamin D supplementation should be held in abeyance for prevention until such RCTs are completed and reported. Those at highest risk of infection due to having chronic disease, low 25(OH)D status, and/or being in frequent contact with others likely to be infected should be taking vitamin D," he says.
"As noted, there is mounting evidence that vitamin D can reduce risk and severity of RTIs including that the mechanisms are known, that there are many health benefits of higher 25(OH)D concentrations, and that there are very few adverse effects of vitamin D3 supplementation... Thus, there is much to gain and little to lose by taking vitamin D supplements now for COVID-19 prevention."
A number of reports on this subject picked up by NutraIngredients include that by researchers from Trinity College in Dublin, Ireland, which concluded that vitamin D deficiency may increase virus severity after studying the prevalence of Vitamin D deficiency across the globe. The study concludes that Vitamin D is important in regulation and suppression of the inflammatory cytokine response, which plays a role in ‘acute respiratory distress syndrome’ associated with ventilation and mortality in COVID-19 patients.
Another report from an international team of scientists concluded that supplementation above RDA with certain micronutrients including vitamin D, but within recommended upper safety limits, may help combat lung infections.
It concludes: "Supplementation with the above micronutrients and omega-3 fatty acids is a safe, effective, and low-cost strategy to help support optimal immune function; Supplementation above the Recommended Dietary Allowance (RDA), but within recommended upper safety limits, for specific nutrients such as vitamins C and D is warranted; and public health officials are encouraged to include nutritional strategies in their recommendations to improve public health."
Source: BMJ Nutrition, Prevention and Health
Kohlmeier. M., et al
"Vitamin D and SARS-CoV-2 virus/COVID-19 disease"