A new global collaborative study has confirmed that vitamin D supplementation can help protect against acute respiratory infections. The study, a participant data meta-analysis of 25 randomized controlled trials including more than 11,000 participants, has been published online in The BMJ. Most people understand that vitamin D is critical for bone and muscle health, said Carlos Camargo of the Department of Emergency Medicine at Massachusetts General Hospital (MGH), the studys senior author. Our analysis has also found that it helps the body fight acute respiratory infection, which is responsible for millions of deaths globally each year.