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Health See other Health Articles Title: Vitamin D Ineffective for Respiratory Tract Infections October 2, 2012 — Adding vitamin D supplements to your diet with will not prevent upper respiratory tract infections (URTIs) or hasten your recovery from them, according to the results of a randomized, placebo-controlled trial published online October 3 in the Journal of the American Medical Association. "The main finding from this study is that a monthly dose of 100,000 IU of vitamin D3 in healthy adults did not significantly reduce the incidence or severity of URTIs," the authors write. "This result remained unchanged when the analysis included winter season or baseline 25-OHD [25-hydroxyvitamin D] levels." Before this study, it was unclear whether taking vitamin D played a role in preventing or mitigating URTIs, according to David Murdoch, MD, and coauthors. Dr. Murdoch is a professor and the head of the Pathology Department at the University of Otago in Christchurch, New Zealand. Several observational studies have shown an inverse association between 25-hydroxyvitamin D levels and the presence of URTIs. Basic research has also suggested that vitamin D can help boost the body's defenses by helping clear bacteria, build up epithelial barriers to infection, and enhance antigen-presenting cells, Jeffrey Linder, MD, MPH, writes in an accompanying editorial. Dr. Linder is an internal medicine physician at Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts. "Despite this biological evidence and the associations reported in observational studies, a definitive trial to determine whether vitamin D therapy reduces rates of upper respiratory tract infections in adults has been absent," Dr. Linder writes. The current trial enrolled 322 adults older than age 18 years who were in good health. The trial took place between February 2010 and November 2011 in Christchurch, New Zealand. Participants randomly assigned to the active intervention group received an initial oral vitamin D3 dose of 200,000 IU, followed by a second dose of 200,000 IU the following month, then 100,000 IU monthly for 16 months. Participants in the placebo group (n = 161) received matched placebo on the same dosing schedule. Researchers measured the total number of URTIs, how long the episodes lasted, how severe they were, and how much they affected a person's productivity at work (days missed because of URTIs). At baseline, participants had an average 25-OHD level of 29 ng/mL (standard deviation, 9). With vitamin D supplementation, the levels in the intervention group increased to 48 ng/mL and stayed at that level throughout the study. There were no significant differences between the vitamin D and placebo groups in terms of total number of URTIs (593 events occurred in the intervention group vs 611 in the placebo group), number of URTIs per person (mean, 3.7 per person in the intervention group and 3.8 per person in the placebo group; risk ratio, 0.97; 95% confidence interval [CI], 0.85 - 1.11), symptom duration per episode (mean, 12 days in each group; risk ratio, 0.96; 95% CI, 0.73 - 1.25), severity of URTIs, and number of days missed from work because of URTIs (mean, 0.76 days in each group; risk ratio, 1.03; 95% CI, 0.81 - 1.30). "Randomization was successful and the study was well-powered to detect meaningful differences," Dr. Linder, the editorialist, writes. Although the authors did not find a benefit of vitamin D supplementation in their study, they note that other populations might benefit from vitamin D supplementation. "The mean baseline 25-OHD level was 29 ng/mL, and the mean level decreased to about 20 ng/mL during the winter in the placebo group; only 5 participants (1.6%) had baseline levels less than 10 ng/mL. It is possible that an effect may be observed in a population with a higher prevalence of vitamin D deficiency," the authors write. They note that the strengths of the study are its large sample size, its duration (18 months), and the high dose of vitamin D used (including a loading dose). As a result, the study avoided limitations of earlier studies in adults. In 2011, the Institute of Medicine conducted a report on the dietary intake of vitamin D, Dr. Linder notes in his editorial. The conclusion was that "clear evidence of the benefit of vitamin D exists only for bone health, measured by increased bone density and reduced fracture rates." The Institute noted that how vitamin D intake might be related to improving immune function and preventing infection, such as URTI, "was an important area for future research," Dr. Linder writes. The study was funded by the Health Research Council of New Zealand. The study authors and Dr. Linder have disclosed no relevant financial relationships. JAMA. Published online October 3, 2012. Poster Comment: Could be bacteria/virus not particularly active during this particular study period. Post Comment Private Reply Ignore Thread Top • Page Up • Full Thread • Page Down • Bottom/Latest
#1. To: Tatarewicz (#0)
That's why God made vitamin C.
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