The importance of vitamin D for children has usually been considered in relation to building healthy bones, but the coronavirus pandemic is now highlighting its potential significance for lung function and fighting infection as well.
We know that vitamin D is needed to keep bones, teeth and muscles healthy. A lack of vitamin D can lead to bone deformities such as rickets in children, and bone pain and muscle weakness, caused by a condition called osteomalacia, in children and adults.
SOURCES AND SUPPLEMENTS
During the summer, most people should be able to get all the vitamin D they need from sunlight. However, during autumn and winter, the sun is not strong enough for the body to make vitamin D, so diet becomes more important.
Vitamin D can be found in foods including:
- oily fish such as salmon, sardines, herring and mackerel
- red meat
- liver
- egg yolks
- fortified foods such as some fat spreads and breakfast cereals.
The Government’s Healthy Start scheme, which provides vouchers for basic foods and formula to disadvantaged families, also provides coupons for vitamin supplements, including up to 10 micrograms of vitamin D. Some local authorities also run schemes providing pregnant women, new mothers and young children with supplements.
Suma Uday, consultant paediatric endocrinologist at Birmingham Women’s and Children’s Hospital and research fellow at the University of Birmingham, says schemes to ensure uptake are vital. ‘Vitamin D deficiency remains widely prevalent in the UK, with children being the most vulnerable,’ she explains.
‘Strategies to improve uptake of supplements in pregnant women and infants are critical. One way to ensure supplementation is by recommending and monitoring its uptake at each healthcare visit or contact. Long-term strategies such as mandatory food fortification should also be considered.’
OFFICIAL GUIDANCE
Official guidance for vitamin D consumption in babies and young children is:
- Breastfed babies from birth to one year of age should be given a daily supplement containing 8.5 to 10 micrograms of vitamin D.
- Children aged between one and four should be given a daily supplement containing 10 micrograms of vitamin D.
- Formula-fed babies should not be given a vitamin D supplement until they are having less than 500ml of infant formula a day, as formula is fortified with vitamin D.
However, Dr Uday says UK advice for breastfed and formula-fed babies is out of step with thinking in several other countries. ‘The UK policy differs from policies in most European countries where both breast- and formula-fed infants are supplemented from birth, giving a simple public health message,’ she explains.
‘Moreover, formula-fed infants are also reported to suffer from the consequences of vitamin D deficiency, and formula feed is not entirely protective.’
VITAMIN D DEFICIENCY AND COVID-19
The importance of vitamin D has hit headlines in recent months, as research which has found it may help boost immune function, particularly in relation to respiratory health, has been used to suggest its anti-infective and anti-inflammatory properties may help in the fight against coronavirus.
Adrian Martineau, professor of respiratory infection and immunity at Queen Mary University of London, says groups that are more likely to have lower levels of vitamin D have also been found to be more at risk from Covid-19.
‘BAME [Black, Asian and minority ethnic] groups, the obese and the elderly are well known to have higher rates of Covid-19. This shows a striking overlap between vitamin D deficiency and bad Covid,’ he explains.
Professor Martineau has been involved in clinical trials which have shown the protective effect of vitamin D against acute respiratory infections, from a cold to pneumonia. ‘Covid-19 is one of these infections, so people are thinking that sauce for the goose could be sauce for the gander,’ he says.
Now Professor Martineau, who has also worked on studies linking vitamin D deficiency to ADHD, and investigating its benefits in treating severe acute malnutrition, is carrying out research to identify risk factors for Covid-19, of which vitamin D deficiency may be one.
‘Vitamin D is more important to general health than we appreciated,’ he says. ‘Originally, up to 20 or 30 years ago, it was just thought to be important for bones, and avoiding rickets and osteomalacia. But since the turn of this century, we have seen the vitamin D receptor distribute not just to bones and kidneys to regulate calcium, but to 32 other tissues, including the brain, immune cells and lungs.
‘The enzyme which converts vitamin D into its active form is also found in all these places, so vitamin D can be activated in all these tissues.’
However, he acknowledges the evidence on vitamin D is ‘mixed’ and adds, ‘There is suggestive evidence that vitamin D may correlate with Covid-19, but we need a full study to really nail it down, and then a large clinical trial, ideally over winter.’
GOVERNMENT RESPONSE
Despite the pandemic, at this stage the Government’s advice remains that from late March or early April until the end of September, most people should be able to get all the vitamin D they need from sunlight.
A ‘rapid’ evidence review on vitamin D ‘in the context of Covid-19’ carried out by the National Institute for Health and Care Excellence (NICE), with support from Public Health England, found no evidence to support taking vitamin D supplements to specifically prevent or treat Covid-19.
However, Public Health England did reissue its advice early in April 2020, emphasising that while lockdown measures were in place, everyone, including children and pregnant and breastfeeding women, should take a daily vitamin D supplement.
A spokesperson for Public Health England says, ‘This advice is not about preventing coronavirus or mitigating its effects. There is no robust evidence to support this. Vitamin D is needed to keep bones and muscles healthy.’
MORE INFORMATION
Groups most at risk of vitamin D deficiency include: under-fives;pregnant and breastfeeding women; people with low or no exposure to the sun; and people with darker skin – for example, those of African, African-Caribbean and South Asian origin –because their bodies need longer in the sun to make sufficient vitamin D. For more on vitamin D, risk groups, children’s diets and enjoying sunshine safely, see: https://bit.ly/3fo4a06
- www.healthystart.nhs.uk/for-health-professionals/vitamins
- www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d
- https://bit.ly/3067Xsw
- Professor Martineau’s study is at: www.qmul.ac.uk/covidence
