Vitamin D supplementation and risk of respiratory tract infections: a meta-analysis of randomized controlled trials.
['Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.', 'Vitamin D supplementation and risk of respiratory tract infections: a meta-analysis of randomized controlled trials.', 'Iwona Stelmach', 'The BMJ', 'Creative Commons Attribution', 'Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data.']