• 33% of D*action participants experienced a cold and 10% experienced a flu during the 6 months before their most recent test. 
• Participants with vitamin D levels ≥ 40 ng/ml reported 41% fewer cases of the flu and 15% fewer colds than participants with levels <20 ng/ml. 

What has research found?

Randomized trial of vitamin D supplementation and risk of acute respiratory infection in Mongolia
Carlos A. Camargo, Jr., MD Dr PH, et al.
Professor of Nutrition and Epidemiology
Harvard Medical School
September 2012
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Camargo, et al. found that Vitamin D supplementation significantly reduced the risk (by 50%) of acute respiratory infections (ARI) in winter among Mongolian children with vitamin D deficiency. Classrooms of Mongolian schoolchildren were randomly assigned to different treatments in winter (January-March) with 247 assigned to daily ingestion of unfortified milk or milk fortified with 300 IU D3. Parents reported ARI occurrences during these 3 months. At baseline, the median serum 25(OH)D level was 7 ng/mL. At the end of the trial, the median 25(OH)D levels of children in the group who received fortified milk was 19 ng/mL, the control group (with unfortified milk) remained the same. After adjusting for age, gender, and history of wheezing, vitamin D halved the risk of ARI.


Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren
May 2010
M. Urashima, et al.
Division of Molecular Epidemiology
Jikei University School of Medicine
Tokyo, Japan
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This study concluded that vitamin D3 supplementation during the winter resulted in 42% fewer incidences of influenza A, especially in specific subgroups of schoolchildren. In this randomized, double-blind, placebo-controlled trial, 167 schoolchildren received vitamin D3 supplements (1200 IU/day) while another 167 received a placebo from December 2008 through March 2009. Influenza A occurred in 18 children from the treatment group compared to 31 in the placebo group.

Do you know your vitamin D level going into cold and flu season? If not, test today!