Clinical question
Is vitamin D effective and safe when used to reduce the risk of severe asthma exacerbations or to improve asthma control?
Bottom line
This systematic review does not find evidence to support a role for vitamin D supplementation in reducing the risk of asthma exacerbations or improving asthma control. The null findings of this review are based on the largest pool of evidence analysed to date, and are consistent for primary and secondary outcomes.
Nonetheless, participants with severe asthma and those with baseline 25-hydroxyvitamin D concentrations <25nmol/L were poorly represented, and a protective effect of the intervention cannot be excluded in these patient groups.
Caveat
This review followed rigorous prespecified selection criteria, restricted to double-blind, placebo-controlled trials. It incorporated evidence across a wide range of patient populations in terms of age, country, baseline vitamin D status, and vitamin D dosing regimens. The evidence produced by this review was graded as high for the primary outcome and high to moderate for the majority of secondary outcomes.
Context
Low blood levels of vitamin D have been linked to an increased risk of severe asthma attacks, defined as those requiring oral (systemic) steroid medications. Vitamin D metabolites can produce antimicrobial and anti-inflammatory activity. This might decrease the risk of asthma exacerbations, which are often precipitated by respiratory infection.
Cochrane Systematic Review
Williamson A, et al. Vitamin D for the management of asthma. Cochrane Database Syst Rev 2023;2:CD011511. This review contains 20 trials with a total of 2225 participants.
![Barbara Fountain, editor of New Zealand Doctor Rata Aotearoa, and Paul Hutchison, GP and senior medical clinician at Tāmaki Health [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/Barbara%20Fountain%2C%20editor%20of%20New%20Zealand%20Doctor%20Rata%20Aotearoa%2C%20and%20Paul%20Hutchison%2C%20GP%20and%20senior%20medical%20clinician%20at%20T%C4%81maki%20Health%20CR%20Simon%20Maude.jpg?itok=-HbQ1EYA)
![Lori Peters, NP and advanced health improvement practitioner at Mahitahi Hauora, and Jasper Nacilla, NP at The Terrace Medical Centre in Wellington [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/2.%20Lori%20Peters%2C%20NP%20and%20advanced%20HIP%20at%20Mahitahi%20Hauora%2C%20and%20Jasper%20Nacilla%2C%20NP%20at%20The%20Terrace%20Medical%20Centre%20in%20Wellington%20CR%20Simon%20Maude.jpg?itok=sUfbsSF1)
![Ministry of Social Development health and disability coordinator Liz Williams, regional health advisors Mary Mojel and Larah Takarangi, and health and disability coordinators Rebecca Staunton and Myint Than Htut [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/3.%20Ministry%20of%20Social%20Development%27s%20Liz%20Williams%2C%20Mary%20Mojel%2C%20Larah%20Takarangi%2C%20Rebecca%20Staunton%20and%20Myint%20Than%20Htut%20CR%20Simon%20Maude.jpg?itok=9ceOujzC)
![Locum GP Helen Fisher, with Te Kuiti Medical Centre NP Bridget Woodney [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/4.%20Locum%20GP%20Helen%20Fisher%2C%20with%20Te%20Kuiti%20Medical%20Centre%20NP%20Bridget%20Woodney%20CR%20Simon%20Maude.jpg?itok=TJeODetm)
![Ruby Faulkner, GPEP2, with David Small, GPEP3 from The Doctors Greenmeadows in Napier [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/5.%20Ruby%20Faulkner%2C%20GPEP2%2C%20with%20David%20Small%2C%20GPEP3%20from%20The%20Doctors%20Greenmeadows%20in%20Napier%20CR%20Simon%20Maude.jpg?itok=B0u4wsIs)
![Rochelle Langton and Libby Thomas, marketing advisors at the Medical Protection Society [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/6.%20Rochelle%20Langton%20and%20Libby%20Thomas%2C%20marketing%20advisors%20at%20the%20Medical%20Protection%20Society%20CR%20Simon%20Maude.jpg?itok=r52_Cf74)
![Specialist GP Lucy Gibberd, medical advisor at MPS, and Zara Bolam, urgent-care specialist at The Nest Health Centre in Inglewood [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/7.%20Specialist%20GP%20Lucy%20Gibberd%2C%20medical%20advisor%20at%20MPS%2C%20and%20Zara%20Bolam%2C%20urgent-care%20specialist%20at%20The%20Nest%20Health%20Centre%20in%20Inglewood%20CR%20Simon%20Maude.jpg?itok=z8eVoBU3)
![Olivia Blackmore and Trudee Sharp, NPs at Gore Health Centre, and Gaylene Hastie, NP at Queenstown Medical Centre [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/8.%20Olivia%20Blackmore%20and%20Trudee%20Sharp%2C%20NPs%20at%20Gore%20Health%20Centre%2C%20and%20Gaylene%20Hastie%2C%20NP%20at%20Queenstown%20Medical%20Centre%20CR%20Simon%20Maude.jpg?itok=Z6u9d0XH)
![Mary Toloa, specialist GP at Porirua and Union Community Health Service in Wellington, Mara Coler, clinical pharmacist at Tū Ora Compass Health, and Bhavna Mistry, specialist GP at Porirua and Union Community Health Service [Image: Simon Maude]](/sites/default/files/styles/thumbnail_cropped_100/public/2025-03/9.%20Mary%20Toloa%2C%20Porirua%20and%20Union%20Community%20Health%20Service%20in%20Wellington%2C%20Mara%20Coler%2C%20T%C5%AB%20Ora%20Compass%20Health%2C%20and%20Bhavna%20Mistry%2C%20PUCHS%20CR%20Simon%20Maude.jpg?itok=kpChr0cc)