Is vitamin D effective for mild to moderate asthma? It appears not!

The Bottom Line

  • In contrast with previous research, current evidence shows that vitamin D supplements do not reduce the risk of severe asthma attacks or improve the control of asthma symptoms in children and adults with mostly mild to moderate asthma.
  • More research is needed for different populations, such as those with severe asthma and very low vitamin D levels.
  • Stay up to date on where the current evidence-base stands for strategies you are already using or would like to use. Your healthcare team is a good source of information to consult. 

Take a deep breath in and a deep breath out. Simple enough, right? Unfortunately, this task may not come easy to all of us. Millions of people are affected by lung conditions such as asthma, pneumonia, chronic obstructive pulmonary disease (COPD), influenza, and lung cancer.  

In 2019, asthma alone impacted over 260 million people worldwide (1). Asthma is a long-term lung disease caused by inflammation and narrowing of the airways (1;2). It is marked by repeat attacks that consist of tightness in the chest, coughing, wheezing, and difficulty breathing (2). In addition to the need for medication (such as steroid inhalers), severe asthma attacks can lead to visits to the emergency room, admission to a hospital for treatment, and even death (2;3). In fact, asthma was responsible for the deaths of more than 450 thousand people around the world in 2019 (1).

Researchers have highlighted that there is a lot of interest and debate around whether vitamin D has the potential to be used as a treatment for asthma and more specifically the prevention of asthma attacks and/or improvement of symptoms (2;4). Just 7 years ago, the best available evidence at the time suggested that vitamin D supplementation had a role to play in reducing the risk of severe asthma attacks in adults with mild to moderate asthma, while noting where additional research was needed (4). However, a more recent update of that systematic review, which considers new studies that have been released since 2016, has come out (2).

The question then becomes: does the update support or contradict earlier results?

What the research tells us

In what may come as a surprise to some, the new review contradicts some of the previous positive findings (2;4). Current evidence suggests that in children and adults with mostly mild to moderate asthma, vitamin D supplements do not reduce the risk of severe asthma attacks or improve the control of asthma symptoms compared to placebo (2).

On the other hand, the older and newer reviews do agree that vitamin D supplementation does not appear to increase the risk of serious harmful side effects (2;4).

More research is still needed in people who live with severe asthma and those with really low baseline vitamin D levels. As of right now, we cannot comment on whether vitamin D has benefits related to severe asthma attacks and symptom control for these specific populations. Additionally, calcidiol—an alternate form of vitamin D—requires a closer look because one study did find some positive results for asthma control (2).

Staying in the know about where the current evidence lies on any strategy you are implementing or interested in is important. Like we saw here, as new evidence emerges, we gain a better understanding of the effectiveness and safety of different strategies. Sometimes the new evidence supports what we already know and other times it changes it, which has implications for use and practice. Discuss any questions you may have about your current treatment plan or options you are interested in with your healthcare team.

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Author Details


  1. World Health Organization. Asthma. [Internet] 2023. [cited June 2023]. Available from
  2. Williamson A, Martineau AR, Sheikh A, et al. Vitamin D for the management of asthma. Cochrane Database Syst Rev. 2023; 2:CD011511. doi: 10.1002/14651858.CD011511.pub3.
  3. Reddel HK, Taylor DR, Bateman ED, et al. An official American Thoracic Society/European Respiratory Society statement: Asthma control and exacerbations: Standardizing endpoints for clinical asthma trials and clinical practice. Am J Respir Crit Care Med. 2009;180(1):59-99.
  4. Martineau AR, Cates CJ, Urashima M, et al. Vitamin D for the management of asthma. Cochrane Database Syst Rev. 2016; 9:CD011511. doi: 10.1002/14651858.CD011511.pub2. 

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