Vitamin D does not prevent respiratory infection?

Certainly not, according to a study in the Journal of the American Medical Association. What we got out of this study was very positive, even if the results were inconclusive. In addition, there are at least 5 recent studies, two of which the authors mention, that found that vitamin D supplementation did reduce upper respiratory tract infection (URTI). 

Here is what we loved about this study:

• The researchers gave subjects a loading dose of 200,000 IU of Vitamin D3 (that is not a misprint) and then 100,000 IU of Vitamin D3 once per month thereafter for 18 months. You would think the researchers of this study would have heeded the grave concern shown by the Institute of Medicine last year about the potentially fatal effects of overdosing on vitamin D (we disagree with IOM's assessment).
  
  What do you know? There were no adverse effects from this gargantuan dose of vitamin D3. For those of you who constantly argue with us that taking 5000 IU is too much vitamin D3, please take notice. Now, if these subjects were taking vitamin D2 (synthetic, prescription-only), I feel there would have been adverse effects.
  
  
• There were less total URTIs in the vitamin D group (593) than in the placebo group (611). The authors found this to be statistically insignificant. However, if you prorate these numbers to a population study of 50,000, you are talking about a reduction of URTIs in the thousands. The money lost in work hours, productivity, and the thousands more contagious people walking around is no joking matter to public health officials. Hence, any reduction in URTIs with a supplement as cheap as vitamin D seems like a no-brainer. This, of course, does not take into account the myriad other ways in which vitamin D supplementation is vital for optimal health.

Here is what was wrong about the study:

• Subjects' vitamin D levels were considered in the normal range, meaning there were no vitamin D deficient individuals when the study began. Vitamin D deficient individuals have a harder time fighting infection.
• What were the authors thinking recommending that much vitamin D3 for an 18 month period of time? There really is no precedence for it. Their thinking was to get vitamin D levels to the upper limit as quickly as possible, but obviously it was not the right choice.
• The Vitamin D3 used in the study was a water-soluble tablet, so while it may have raised vitamin D levels in the subjects, it left their bodies immediately. All the other studies that have shown reductions in URTI's have used much lower doses taken on a daily basis. The authors acknowledge this variable.

For reference purposes, here are recent studies showing the positive effects of vitamin D and infection reduction.

• A study in Journal of Allergy and Clinical Immunology stated that narrowband UV light reduces systemic immune responsiveness via the induction of regulatory T cells. Light and vitamin levels may affect particular immune functions independently. The levels of serum vitamin D over which these effects are apparent should guide future interventions. August 2012
• Camargo CA Jr, Ganmaa D, Frazier AL, et al. Randomized trial of vitamin D supplementation and risk of acute respiratory infection in Mongolia. Pediatrics. 2012;130(3):e561-e567
• Manaseki-Holland S, Maroof Z, Bruce J, et al. Effect on the incidence of pneumonia of vitamin D supplementation by quarterly bolus dose to infants in Kabul: a randomised controlled superiority trial. Lancet. 2012;379(9824):1419-1427 
• The effect of two oral dosing regimens of vitamin D supplementation on vitamin D status and markers of immune function was evaluated in people in Antarctica with no UV light exposure for 6 months in a Journal Nutrition study. Participants were given a 2000IU daily or 10,000IUweekly vitamin D supplement. After 6 months, the serum 25-hydroxyvitamin D concentration increased dramatically in both groups. The data provided evidence that vitamin D, interacting with stress, can reduce risk of latent virus reactivation during the winter. June 2011
• According to a recent study in Journal of the American College of Nutrition, cod liver oil was a traditional source of vitamin D in the United States and was used to prevent and treat rickets up until the 1930s. The researchers used liquid cod liver oil of adequate purity and acceptable taste for infants and young children, as well as a children's multivitamin/mineral supplement with selenium and other trace metals. In a cluster-randomized study of pediatric visits for upper respiratory illness during the winter and early spring, these nutritional supplements decreased mean visits/subject/month by 36%–58%. Cod liver oil is culturally valued and has been used as a folk remedy by many low-income minorities in the United States. Unfortunately, nutritional supplements cannot be purchased with SNAP benefits (formerly called food stamps). Inclusion of cod liver oil in state Medicaid formularies would make it available to low-income children, whose families may not be able to pay for it out-of-pocket. June 2011
• Researchers in the Netherlands said in a recent report that vitamin D is essential in activating the human immune defense system.The researchers, from the University of Copenhagen, said that without vitamin D, T-cells, which fight off serious infection in the body, cannot do their job. Vitamin D activates T-cells to detect and kill foreign pathogens. It transforms the cells from harmless immune cells into what the researchers called "killer cells," which search for and destroy all traces of a foreign pathogen. Without vitamin D, the researchers said the T-cells would remain dormant and do nothing to protect the body against illness. The study appears in the latest edition of the journal Nature Immunology. March 2010