Two reviews were published this week by The Scientific Advisory Commission on Nutrition (SACN) and the National Institute for Health and Care Excellence (NICE) examining evidence on vitamin D's efficacy against acute respiratory tract infections and the prevention and treatment of COVID-19.
The reviews were considered necessary after a number of studies have concluded that supplementation with Vitamin D could help reduce COVID-19 severity and even cut the mortality rate.
In one study reported by NutraIngredients, researchers from Trinity College in Dublin, Ireland, concluded: "A substantial proportion of the population in the Northern Hemisphere will currently be vitamin D deficient, and supplements eg. 1000 units per day are very safe. It is time for governments to strengthen recommendations for vitamin D intake and supplementation, particularly when under lock-down Vitamin D deficiency correlates with poor sunlight exposure, age, hypertension, diabetes, obesity and ethnicity—all features associated with increased risk of severe COVID-19."
NICE researchers carried out a rapid evidence review which evaluated five observational studies (D'Avolio et al. 2020, Hastie et al. 2020, Ilie et al. 2020, Laird et al. 2020 and Fasano et al. 2020) and concluded that all had a high risk of bias because of the very low quality of evidence as no causal relationship was found after adjustment for confounders such as comorbidity, socio-demographics, ethnicity, BMI and other baseline factors. It also pointed out there is currently no data from clinical trials.
It repeated the UK Government's advice that all people should consider taking a daily supplement containing 10 micrograms vitamin D during autumn and winter months. They also advise that people whose skin has little to no exposure to sunlight and ethnic minority groups should consider taking a vitamin D supplement all year round and this applies to anyone indoors shielding or self-isolating due to the pandemic.
Researchers, scientists, nutritionists and industry players have voiced profound disappointment in these findings.
In a LinkedIn discussion on the topic, Dr Reindert Graaff, Senior Assistant Professor at the University Medical Centre Gorningen, Netherlands, sums up the general response by asking: "Shouldn't the best available proof be enough when it is better than doing nothing?"
Max Gowland, retired health researcher and founder of the healthy ageing supplements brand Prime Fifty, argues that studies showing strong associations should be good enough evidence in the midst of a pandemic when there is not the luxury of time.
"It looks like the scientific reviewers have been incredibly picky with respect to the heterogeneity of the data in that famous meta-analysis that we keep talking about...Surely a strong indication at this stage should be good enough to use something as safe and innocuous as vitamin D!
"The problem is it will take months if not years to set up proper vitamin D trials with the actual COVID-19 itself. I personally don’t believe that it is worth waiting for this data, when there is so much other data on general respiratory infections. Waiting for perfection means that we will simply be far too late in terms of recommendations."
Independent Registered Public Health Nutritionist Dr Emma Derbyshire, who described the review as 'abysmal', agreed that new trials of vitamin D supplements on COVID patients would be too time consuming and any results would come too late.
"We should be looking at it from a broader perspective to prepare for winter and any forthcoming waves...
"It was hoped that this review would pull out firmer recommendations for BAEMs and other groups ie. those with a higher BMI that most likely need more vitamin D to correct deficiencies. This, in turn, could have gone some way to help improve outcomes should these individuals contract SARS Cov 2..."
She adds: "Looking at the review methods I think a major flaw was that ‘viral’ was not used in the search terms to identify papers."
Mike Gleeson, professor of exercise biochemistry at Loughborough University, points out the report only recommends supplements of 10 micro grams per day which is 400 IU which he says would not be enough for someone who is deficient to reach adequate levels.
"Recommended intakes for athletes are 1000-4000 IU per day which would also be my recommendation for everyone if you are not getting sunlight on a regular basis.
"It’s cheap and safe and while it might not prevent you from getting infected with COVID-19 there is a good chance it will reduce symptom severity and duration which are the more important outcomes.
"Nothing you consume can prevent you from being infected but some things can affect the outcome."
In an article published on the BMJ website, one of the authors of one of a reviews cited in the SACN report, Adrian Martineau, professor of respiratory infection and immunity at Queen Mary University of London, said that he felt the review had not considered several other seemingly relevant trials.
“My group is in the final stages of an updated meta-analysis, including data from the new trials identified by SACN as well as nine others. We hope to submit our findings next month,” he added.
Paul Chrisp, director for the Centre for Guidelines at NICE, has said: "While there are health benefits associated with vitamin D, our rapid evidence summary did not identify sufficient evidence to support the use of vitamin D supplements for the treatment or prevention of COVID-19.
"We know that the research on this subject is ongoing, and NICE is continuing to monitor new published evidence."
Impact on BAME groups
Existing advice highlights that people who have dark skin, for example with an African, African-Caribbean or south Asian background, may not get enough vitamin D from sunlight and it is recommended that they consider taking a daily supplement containing 10 micrograms of vitamin D throughout the year.
The SACN 2016 review found a lack of available evidence on the role of vitamin D in Black, Asian and Minority Ethnic groups, with the report recommending that further research is undertaken on “whether there are differences in dietary vitamin D requirements of ethnic groups in the UK”.
PHE, SACN and NICE are aware that a systematic review and controlled trials on vitamin D and COVID-19 are underway and will continue to monitor and assess new evidence as it is published.