Vitamin D protects against Colds and Flu

Vitamin D Protects Against Colds & Flu

It has long been observed that incidence of colds and influenza rises in the fall and winter months and wanes in the spring and summer. This is the opposite of serum levels of 25-hydroxyvitamin D, which increase in the summer and decrease dramatically as the amount of daylight diminishes. Research has shown adequate blood levels of vitamin D stimulate the genetic expression of antimicrobial peptides in human monocytes. These peptides demonstrate a broad spectrum of antimicrobial activity against viruses, bacteria, and fungi. Vitamin D also has other immune-modulating and anti-inflammatory activity.

An article published in the journal Epidemiology and Infection reports on a three-year study of 208 African-American postmenopausal women (who are at great risk of vitamin D deficiency) who were supplemented with vitamin D or placebo. For the first two years the active group received 800 IU daily, which was increased to 2,000 IU daily in the last year of the study. In the three years of the study 34 patients reported cold and flu symptoms, eight in the supplemented group and 26 in the placebo group (p<0.002). This showed that participants who got a placebo had a 300-percent greater risk of having a cold or flu, and that vitamin D supplementation provided a highly significant protective effect.

Aloia JF. Epidemic influenza and vitamin D. Epidemiol Infect 2007;135:1095-1096.

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