Latest guidance by the National Institute for Health and Care Excellence (NICE), Public Health England (PHE) and the Scientific Advisory Committee on Nutrition (SACN), could not determine a direct link based on available evidence.
The report goes on to recommend more research be conducted on the subject, stressing the use of high-quality randomised controlled trials in future studies.
“SACN has worked closely with NICE and PHE to consider the available evidence from recent studies on vitamin D in relation to COVID-19,” said Professor Ian Young, Chair of the Scientific Advisory Committee on Nutrition, which advises PHE and other UK government organisations on nutrition-related matters.
“It is recommended that everyone should take a daily 10 microgram (400 international units) vitamin D supplement from October to early March. This dose is safe and effective at maintaining healthy vitamin D blood levels.
“Many people have been indoors more than usual this spring and summer, which means we might not have been making enough vitamin D from sunlight. So, it’s even more important this year to take a vitamin D supplement as we go into the winter months,” he added.
“Clinically vulnerable groups will also be eligible for free vitamin D supplements throughout the winter period, starting in January.”
More research needed
The guidance follows recent action by the UK Government earlier this month in which they began offering free vitamin D supplements to the most vulnerable that includes care home residents.
Secretary of State for Health and Social Care Matt Hancock said the move was designed to support bone and muscle health affected during lockdown rather than directly addressing COVID-19.
Expert reaction to the updated guidance was generally positive, with Dr Emeir McSorley, Senior Lecturer in Human Nutrition at Ulster University, welcoming the call by the Expert Panel for more robust research into vitamin D and its role in immune response.
Referring to a study that pointed to vitamin D’s role in optimal musculoskeletal and bone health, Dr Emeir McSorley highlighted a need to determine the exact supplementation dose to prevent deficiency in older, more vulnerable groups such as those residing in care homes.
“Furthermore, effective monitoring of vitamin D status among community-dwelling older adults and care home residents, is needed as part of a strategy to promote better quality of life and health outcomes in the elderly,” she added.
Building on her comments, Dr Vimal Karani, Associate Professor in Nutrigenetics and Nutrigenomics, at the University of Reading, emphasised the genetic aspect of vitamin D’s effectiveness in addressing the virus.
“Host genetic susceptibility could play a role in this association (vitamin D status and COVID-19) which explains why some individuals respond to high doses of vitamin D supplementation while the rest fail.
“This has been shown through studies in BAME communities where the prevalence of SARS-CoV-2 infection was higher compared to Caucasians, given that the genetic map varies across different ethnic groups.”
Professor Young echoed these thoughts, stating, “Some people are more at risk of not having enough vitamin D even in spring and summer.
“This includes those with dark skin (such as those with African, African-Caribbean or south Asian backgrounds), those who are not outdoors often, those in care homes, and those who cover up most of the skin when outdoors. We advise these people to take a vitamin D supplement all year round.”
Across Europe, official advice regarding the use of vitamin D during this period has generally been similar with France’s French Agency for Food, Environmental and Occupational Health & Safety (ANSES) stressing the importance of vitamin D in ensuring adequate immune support.
“[Along with dietary recommendations], the Agency reiterates that food supplements for offsetting a possible inadequate vitamin D intake should be taken only on dietary or medical advice.
“This is especially as in most cases; you can get all the vitamin D you need through your diet and through exposure to the sun. You just need to make sure that you cover your requirements through these two methods.”
Meanwhile in Germany, The Federal Institute for Risk Assessment (BfR) recommends no more than 20 micrograms (µg) or 800 iE (International Units) of vitamin D per day.
And at the end of October 2020 the Institute made it clear no studies prove taking vitamin D protects against infection of the virus.
The German Nutrition Society recently stated that a good supply of vitamin D is best achieved via the skin's own synthesis and through diet. A safe dosage supplement should only be taken if this proves inadequate.