Some 5,292 elderly British individuals (mean age 77 years) participating in a study on fracture prevention were randomly assigned to receive 800 IU per day of vitamin D, 1,000 mg per day of calcium, both supplements, or placebo for 24 to 62 months. About two-thirds of the participants responded to a questionnaire at a median of 18 months after randomization. Among the 55% of questionnaire respondents who were still taking their treatment, the incidence of infections was 20% lower in those assigned to received vitamin D than than those assigned not to receive vitamin D (p=0.06).
Comment by Alan Gaby, MD
Vitamin D enhances immune function, and vitamin D deficiency increases the risk of developing infections. Although the results of the present study were only of borderline statistical significance, they suggest that vitamin D supplementation can prevent infections among the general population of elderly individuals. In a previous study conducted among black women in the US, the incidence of cold or influenza symptoms was significantly lower among those who received vitamin D than among those who received a placebo. A dose of 800 IU per day of vitamin D appears to be the minimum amount that improves various clinical outcomes in elderly people.
Avenell A, et. al. Vitamin D supplementation to prevent infections: a sub-study of a randomized placebo-controlled trial in older people (RECORD trial, ISRCTN 51647438). Age Ageing 2007;36:574-577.
Reprinted with exclusive permission of Townsend Letter - July 2009.