As the days shorten and the nights draw in, everyone should consider taking vitamin D supplements to combat the lack of sunlight during the autumn and winter months, according to NHS guidelines. New research has found that the supplement can also reduce the risk of asthma attacks in those with vitamin D deficiency.
Winter boost
Vitamin D helps to regulate the amount of calcium and phosphate in the body – nutrients 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 caused by a condition called osteomalacia in adults.
During the autumn and winter, you need to get vitamin D from your diet because the sun isn’t strong enough for the body to make vitamin D.
However, it's difficult for people to get enough vitamin D just from food. So the NHS recommends that everyone should consider a daily supplement containing 10mcg of vitamin D from early October to the end of March. And people with dark skin from African, African-Caribbean and South Asian backgrounds should consider taking vitamin D supplements throughout the year. The NHS also recommends that children aged one to four take the supplements all year round.
After the longest day of the year – 21 June, when sun rises at 4:43am and sets at 9:21pm – daylight decreases until the shortest day of the year on 21 December, when the sun rises at 8:03am and sets at 3:53pm.
Vitamin D and asthma attacks
Meanwhile, a study pooling data from seven trials in the UK, USA, Ireland, Poland and Japan, has found that vitamin D supplements can reduce the risk of asthma attacks by a quarter in those with a pre-existing vitamin D deficiency.
The study, published in The Lancet, examined randomised controlled trials that compared vitamin D supplementation with an inactive placebo.
Researchers at Queen Mary University of London examined whether vitamin D reduced the risk of ‘asthma exacerbations’ – severe asthma episodes requiring hospitalisation or treatment with oral steroids. They also examined participants’ hospital attendance and any side effects they had while taking the supplement.
When looking at the data across all seven studies, the researchers found that taking a vitamin D supplement was associated with a 26% reduced risk of asthma exacerbation needing steroid treatment – but noted that this protective effect was only seen in people who were vitamin D deficient to start with.
As only 92 participants had a pre-existing vitamin D deficiency, the researchers have warned that these are relatively low numbers for a research study. There were 764 participants who were not vitamin D deficient.
Inexpensive supplement
Lead researcher, Professor Adrian Martineau, said: “These results add to the ever-growing body of evidence that vitamin D can support immune function as well as bone health. Vitamin D is safe to take and relatively inexpensive so supplementation represents a potentially cost-effective strategy to reduce this problem.”
He added: “In the UK, sunlight only contains enough UVB to stimulate production of vitamin D in the skin between April and October – in winter and early spring, it won’t provide any vitamin D.
“UVB is also a risk factor for skin cancer of course – so from a safety perspective it makes sense to be careful with exposure to sunlight, and keep vitamin D levels up during winter and early spring by taking a regular supplement.”