The effect of vitamin D supplementation on acute respiratory tract infection in older Australian adults: an analysis of data from the D-Health Trial

SPS commentary:

A related commentary discusses this study as well as other recent research on vitamin D supplementation in respiratory infection, so of which suggesting supplementation provides positive effects. It states that, overall, important questions about vitamin D remain. The new study shows that bolus doses of vitamin D are not effective in preventing acute respiratory infections in older people, but there is a possibility that bolus dosing might have an adverse effect for reasons we do not understand, as shown in a large fracture study during which a single bolus dose of 500,000 units annually unexpectedly increased the incidence of falls and fractures by 30%. Data from the latest meta-analysis showed that daily dosing and small doses 400–1,000 units vitamin D reduced respiratory infections by 25%.  Therefore, contrary to popular opinion, vitamin D supplementation might be more effective at lower doses than higher doses.  It concludes that a large definitive placebo-controlled trial of vitamin D using daily oral small doses (800–1,000 units), investigating the incidence of acute respiratory tract infections, should be a priority for the future.

An editorial on this topic has also been published. It highlights that the issue of vitamin D supplementation for prevention of respiratory infection has been extensively debated, with strong arguments in favour and against.  The COVID-19 pandemic has further escalated the discussion. It has long been clear that groups that traditionally exhibit vitamin D deficiency or insufficiency, such as older adults and nursing home residents, and Black, Asian, and minority ethnic populations, are the same groups that have also been disproportionately impacted by COVID-19. Additionally, increased time spent indoors due to strict lockdowns and shielding triggered concerns that some people might not obtain the necessary physiological levels of vitamin D from sunlight.  It highlights the recent NICE guidance on vitamin D in COVID 19 which support PHE advice  for everyone to take vitamin D supplements to maintain bone and muscle health during the autumn and winter months.  However, the rapid review by NICE concluded that sufficient evidence to support vitamin D supplementation with the aim of preventing or treating COVID-19 was still lacking and that the topic should be further investigated.  It concludes that NICE should continue to monitor new evidence as it is peer-reviewed and published, including results from several clinical trials on vitamin D and COVID-19 outcomes that are currently underway.