Vitamin D Lowers the Risk of Getting Influenza A and Asthma Attacks?

Is it possible that vitamin D supplementation could reduce children’s risk of coming down with Influenza A by 58%, and of having an asthma attack by 83%?

Amazing as these claims might seem, this is what was reported in the March 2010 issue of the American Journal of Clinical Nutrition.

The students in this study – which was performed in Japan – ranged in age from 6-15 years of age, and they were given Vitamin D3 (cholecalciferol) at a daily dose of 1200 IU (International Units).

Although these improvements were observed for Influenza A and asthma attacks, there didn’t seem to be any effect on the occurence of Influenza B.

I first ran across this study in a article published in Reuters that was titled ‘Vitamin D helps fend off flu, asthma attacks: study’.

You can see a copy of it at this web address – , and you can find a copy of the article they’re referencing at this web address – .

If you want to read it you’ll have to buy a copy from the journal, but I’ve posted an excerpt from their abstract here for your review:

Results: Influenza A occurred in 18 of 167 (10.8%) children in the vitamin D3 group compared with 31 of 167 (18.6%) children in the placebo group [relative risk (RR), 0.58; 95% CI: 0.34, 0.99; P = 0.04]. The reduction in influenza A was more prominent in children who had not been taking other vitamin D supplements (RR: 0.36; 95% CI: 0.17, 0.79; P = 0.006) and who started nursery school after age 3 y (RR: 0.36; 95% CI: 0.17, 0.78; P = 0.005). In children with a previous diagnosis of asthma, asthma attacks as a secondary outcome occurred in 2 children receiving vitamin D3 compared with 12 children receiving placebo (RR: 0.17; 95% CI: 0.04, 0.73; P = 0.006).

Conclusion: This study suggests that vitamin D3 supplementation during the winter may reduce the incidence of influenza A, especially in specific subgroups of schoolchildren. This trial was registered at as UMIN000001373.

The reference for the article is:

Mitsuyoshi Urashima, Takaaki Segawa, Minoru Okazaki, Mana Kurihara, Yasuyuki Wada, and Hiroyuki Ida. Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. Am J Clin Nutr May 2010 vol. 91 no. 5 1255-1260.

Two thoughts come to mind. 1. I wonder if the influenza vaccine can match these results for Influenza A?, and 2. I suppose it should improve adults odds also.

So, I’m going to keep on taking my 2000 IU of Vitamin D3 every day. Just in case.

Remember, I’m a pharmacist – not a doctor. Check with your doctor before changing your medication regimens or adding any supplements to your daily routine.

Doctors Doctor. Pharmacists Pharmacist. That’s how it’s supposed to be.

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