Cochrane UK’s Senior Fellow in General Practice Lynda Ware looks at a Cochrane ReviewCochrane Reviews are systematic reviews. In systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. on Vitamin D for the management of asthma.
Page updated 31 December 2021
Take-home points
A Cochrane Review Vitamin D for the management of asthma (September 2016) looked at precisely this question and found high- certainty evidence suggesting that it does!
What’s the story?
It seems to me that vitamin D – also known as the ‘sunshine vitamin’ – is very much in the limelight (or should that be sunlight?) right now. Its role in maintaining a healthy skeleton is well known but it may have other important actions. Low levels of vitamin D have been linked to an increased riskA way of expressing the chance of an event taking place, expressed as the number of events divided by the total number of observations or people. It can be stated as ‘the chance of falling were one in four’ (1/4 = 25%). This measure is good no matter the incidence of events i.e. common or infrequent. of asthma attacks in children and adults with asthma. It is thought that vitamin D has anti-inflammatory and antimicrobial functions in the lungs, which may explain why it could be beneficial.
What is Vitamin D?
Vitamin D is a fat-soluble vitamin. It’s present in a small number of foods such as oily fish, liver, red meat and egg yolks. In the UK, certain foods have vitamin D added to them, for example most margarines, some breakfast cereals and infant formula milk. There are also oral supplements which can be bought over the counter or prescribed by a doctor.
Our main source of vitamin D is from the action of sunlight (the UVB component) on our skin. Certain groups of people are at particular risk of not making enough vitamin D in this way e.g. the frail and housebound, residents of nursing homes, and people who wear clothes that cover up most of their skin. It has been suggested that in the UK it might make sense to take a vitamin D supplement from October to March, when there is insufficient UVB beaming down on us to optimally maintain our levels.
What did the Cochrane Review find with regard to vitamin D and asthma?
The recent systematic review from Cochrane Airways found nine double-blind randomizedRandomization is the process of randomly dividing into groups the people taking part in a trial. One group (the intervention group) will be given the intervention being tested (for example a drug, surgery, or exercise) and compared with a group which does not receive the intervention (the control group). placebo-controlled trialsClinical trials are research studies involving people who use healthcare services. They often compare a new or different treatment with the best treatment currently available. This is to test whether the new or different treatment is safe, effective and any better than what is currently used. No matter how promising a new treatment may appear during tests in a laboratory, it must go through clinical trials before its benefits and risks can really be known. of vitamin D in children and adults with asthma, which evaluated the risk of having an asthma attack and/or the level of symptom control. Two studies were in adults and involved 658 participants; seven studies were in children with 435 participants. The studies were conducted in Canada, India, Japan, Poland, UK and USA. Most of the participants had mild to moderate asthma and continued their regular asthma medication for the duration of the trial. The studies lasted from six to twelve months.
High quality evidence showed that giving vitamin D reduced the average number of asthma attacks and the risk of Emergency Department attendances and hospital admissions. These results can be represented diagrammatically :
There was no evidence to indicate that vitamin D brought about an improvement in lung function tests or in day-to-day symptoms. It was safe at the doses given.
So far so good…..
But why does Adrian Martineau, lead author of the review, advise caution before acting on these results?
Well, a few things remain unanswered…..
It is not clear whether giving vitamin D helps all patients with asthma – or just those who have low vitamin D levels. The majority of participants in the trials had mild to moderate asthma. It’s not certain whether those with more severe disease, and therefore at greater risk of asthma attack, are likely to benefit.
Further research
Individual patient dataData is the information collected through research. from the trials included in this review are being extracted to see whether benefits are restricted to those with lower vitamin D levels. New trials in children and adults who are prone to frequent asthma attacks are needed to determine whether vitamin D can prevent asthma attacks in these groups.
The bottom line
Asthma is a common chronicA health condition marked by long duration, by frequent recurrence over a long time, and often by slowly progressing seriousness. For example, rheumatoid arthritis. disease affecting about 300 million people worldwide. Despite greater understanding of the disease and its treatmentSomething done with the aim of improving health or relieving suffering. For example, medicines, surgery, psychological and physical therapies, diet and exercise changes., asthma was responsible for 1216 deaths in UK in 2014 – that’s about 3 people per day.
This systematic review highlights a possible role for vitamin D in preventing severe asthma attacks – cause, I believe, for cautious optimism….
Join in the conversation on Twitter with @CochraneUK or leave a comment on the blog.
Please note, we cannot give specific medical advice and do not publish comments that link to individual pages requesting donations or to commercial sites, or appear to endorse commercial products. We welcome diverse views and encourage discussion but we ask that comments are respectful and reserve the right to not publish any we consider offensive. Cochrane UK does not fact check – or endorse – readers’ comments, including any treatments mentioned.
Lynda Ware has nothing to disclose.
Links:
Martineau AR, Cates CJ, Urashima M, Jensen M, Griffiths AP, Nurmatov U, Sheikh A, Griffiths CJ. Vitamin D for the management of asthma. Cochrane Database of Systematic ReviewsIn systematic reviews we search for and summarize studies that answer a specific research question (e.g. is paracetamol effective and safe for treating back pain?). The studies are identified, assessed, and summarized by using a systematic and predefined approach. They inform recommendations for healthcare and research. 2016, Issue 9. Art. No.: CD011511.pub2.
The Cochrane Library, Wiley Press Room [online]. 2016. High quality evidence suggests Vitamin D can reduce asthma attacks [press release]. 05 September 2016. Available from: http://eu.wiley.com/WileyCDA/PressRelease/pressReleaseId-127902.html
