There are mounting questions about whether vitamin D has a role to play in the fight against coronavirus.
The Scientific Advisory Commission on Nutrition and the health watchdog the National Institute of Health and Care Excellence (NICE) have done a rapid review of the evidence.
What is the advice?
With more people staying indoors during the pandemic, some people may have been deprived of vitamin D.
Normally, many of us get it by spending time outside. Our skin makes it when exposed to the sun.
The NHS says people should consider taking 10 micrograms of vitamin D a day during this time – particularly if they spend most of their time inside.
Before the pandemic people in the UK were already advised to consider taking supplements during the winter months (from October to March).
Meanwhile Public Health England recommends vitamin D throughout the year if:
- you are not often outdoors
- you live in a care home
- you usually wear clothes that cover up most of your skin when outside
People with dark skin may also not be getting enough, even if they spend time outdoors, and should consider an all-year-round supplement.
Why do we need vitamin D?
It is well known that vitamin D is important for healthy bones, teeth and muscles. A lack of it can lead to a bone deformity illness called rickets in children, and a similar bone weakness condition called osteomalacia in adults.
There are also suggestions that vitamin D boosts the immune system and helps fight off infections.
Some studies suggest ensuring adequate vitamin D levels help when we have common colds and flu, for example. But evidence from research is inconsistent.
The Scientific Advisory Committee on Nutrition (SACN) has reviewed studies on vitamin D for treating or preventing chest infections and say there is insufficient evidence to recommend the vitamin for this.
Can it stop coronavirus?
A review of research by the National Institute for Health and Care Excellence suggests there is no evidence to support taking vitamin D supplements to specifically prevent or treat COVID-19.
But experts do think that it may have some broader health benefits during the pandemic.
According to a report in BMJ Nutrition, Prevention and Health, “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.”
Some researchers have suggested that vitamin D deficiency might be linked with poorer outcomes if someone catches coronavirus. But other underlying risk factors, such as heart disease, are common in these patients too, making it hard to draw conclusions.
Prof Jon Rhodes, Emeritus Professor of Medicine at the University of Liverpool, says vitamin D has anti-inflammatory effects, and there is some research that suggests it may dampen down the body’s immune response to viruses.
This could be relevant in very ill coronavirus patients where severe lung damage can result from an inflammatory “cytokine storm” in response to the virus, he says, although much more research is needed to explore this.
Should I take lots of it?
No. Although vitamin D supplements are very safe, taking more than the recommended amount every day can be dangerous in the long run.
If you choose to take vitamin D supplements:
- Children aged one to 10 should not have more than 50 micrograms a day
- Infants (under 12 months) should not have more than 25 micrograms a day
- Adults should not have more than 100 micrograms a day, with the recommended amount 10 micrograms a day
Higher doses may sometimes be recommended by a doctor for patients with proven vitamin D deficiency.
Some people with certain medical conditions, such as kidney problems, cannot safely take vitamin D.
Where can I buy it?
Vitamin D supplements are widely available from supermarkets and chemists. They may be just vitamin D or part of a multivitamin tablet.
Do not buy more than you need to help keep supplies of supplements available for everyone, say experts.
The ingredient listed on the label of most Vitamin D supplements is D3.
Vitamin D2 is produced by plants, and Vitamin D3 is the one made by your skin.
Vitamin drops are available for babies.
What about diet?
Although eating a well-balanced diet can help ensure the normal functioning of the immune system, no individual nutrient, food or supplement is going to “boost” it beyond normal levels.
It’s difficult to get enough vitamin D from food alone.
Eating a well-balanced diet is important for good health and is advisable even when people aren’t facing a pandemic disease outbreak.
It can include vitamin D rich foods such as oily fish and eggs. Some breakfast cereals, margarines and yoghurts are fortified with vitamin D.
Should I sunbathe?
Although you cannot overdose on vitamin D through exposure to sunlight, strong sun burns skin so you need to balance making vitamin D with being safe in the sun. Take care to cover up or protect your skin with sunscreen to prevent burning and damage.
What about children, babies and pregnant women?
The advice is:
- breastfed babies from birth to one year of age should be given a daily supplement of 8.5 to 10 micrograms of vitamin D to make sure they get enough
- formula-fed babies should not be given a supplement until they are having less than 500ml (about a pint) of infant formula a day because formula contains vitamin D
- children aged one to four should be given a daily supplement of 10 micrograms
The dose for adults (10 micrograms a day) applies to pregnant and breastfeeding women.