Vitamin D Can’t Stop the Common Cold
Donít count on vitamin D to protect you from the sniffles. New Zealand researchers report in JAMA that mega-doses of the vitamin proved no better than placebo in reducing incidences of upper respiratory infection, shortening symptom duration or cutting the number of missed workdays among 322 healthy adults. The randomized controlled trial administered 200,000 IU of vitamin D initially, followed by 100,000 IU monthly for 18 months, including two "cold and flu seasons." Researchers found no significant difference between the vitamin D and placebo groups in any measure of upper respiratory infections. They noted, however, that study participants had relatively normal vitamin D levels to begin with; people with deficient levels of vitamin D might see more positive results.