Vitamin D does not prevent colds

The Los Angeles Times “Booster Shots” blog reports, “If you’re trying to ward off the sniffles, you can take vitamin D supplements out of your shopping cart: A new study” published in the Journal of the American Medical Association “reports that dosing with the vitamin does nothing to prevent colds or other forms of upper respiratory tract infections (URTI).”

The NBC News “Vitals” blog reports, “In the study, participants who took high doses of vitamin D supplements every month for more than a year were just as likely to catch colds as those who took a placebo.” In addition, “taking vitamin D supplements … did not reduce the length of time participants were sick, the severity of their illness or the number of workdays they missed.”

HealthDay reports that “to test this association,” New Zealand researchers “recruited more than 300 healthy adults from Christchurch. All had normal vitamin D levels at the start of the study. Half the group was randomly assigned to receive oral vitamin D, while the other half received a placebo tablet.”

WebMD reports, “For the first two months, those assigned to vitamin D took 200,000 IU (international units) once per month. For the rest of the study, they took 100,000 IU once per month.” These dosages were in excess of recommendations by the Institute of Medicine that say that “people 1-70 years old take in 600 IU of vitamin D daily, and that people over 70 years take in 800 IU daily.”

Medscape (10/3, Broder) quotes the study authors, who wrote, “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” upper respiratory tract infections. “This result remained unchanged when the analysis included winter season or baseline 25-OHD [25-hydroxyvitamin D] levels,” they added.

According to MedPage Today, an accompanying editorial observed, “Results suggest that vitamin D should join the therapies listed in the Cochrane reviews as being ineffective for preventing or treating upper respiratory tract infections in healthy adults.”

The editorial further pointed out, “That list with no or questionable benefit or significant side effects includes vitamin C, garlic, Echinacea, zinc, saline nasal irrigation, steam inhalation, increased fluid intake, and other popular strategies.”

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