A case-control study recently published did not find any protective effect of prescribing vitamin D on the risk of developing pneumonia.
Remmelts HH, Spoorenberg SM, Oosterheert JJ, Bos WJ, De groot MC, Van de garde EM. The role of vitamin D supplementation in the risk of developing pneumonia: three independent case-control studies. Thorax. 2013;
Pneumonia is still a major public health problem, leading to over one million hospitalizations per year. It is more likely to be fatal in the elderly and young.
There is a fairly clear relationship with vitamin D and respiratory infections. A recent meta-analysis of 11 randomized controlled trails found that vitamin D protects against respiratory infections to a certain degree.
But what about pneumonia? Pneumonia is an inflammatory condition of the lung, occurring after a virus or bacterial infection. Does vitamin D protect against pneumonia?
Because vitamin D has known effects on the immune system, researchers wanted to study the relationship between vitamin D and a person’s chances of being diagnosed with or hospitalized for pneumonia.
The study compared 33,726 patients with pneumonia to 105,243 matched controls without pneumonia. The patients were subdivided into three groups for analysis:
- Group 1 included patients hospitalized for community-acquired pneumonia.
- Group 2 included cases and controls derived from the data base of an independent research organization in the Netherlands.
- Group 3 included patients who were diagnosed with pneumonia by their general practitioner.
Overall, those diagnosed with pneumonia were more likely to have diabetes, osteoporosis, congestive heart failure, and asthma.
The researchers looked at prescription drug use in their patients and controls, to see which were taking prescription vitamin D and which were not. Vitamin D use was defined as receiving two or more vitamin D prescriptions within six months of diagnosis of pneumonia.
The researchers wanted to know, did prescribing vitamin D protect against pneumonia?
Vitamin D use was not found to help prevent pneumonia in any of the groups, and in the third group, vitamin D use was actually associated with a slightly higher risk of pneumonia.
The authors commented that it is possible the elevated risk may be due to the presence of other health conditions not accounted for. They also speculated that the doses of vitamin D taken might not have been enough to positively affect immune function, but no data was available to assess before and after vitamin D serum levels.
Furthermore, it’s hard to infer whether prescribing vitamin D actually leads to vitamin D sufficiency on a population scale. For instance, a doctor can prescribe vitamin D once or twice or more and if the patient doesn’t take the prescription, then prescribing vitamin D is a marker for vitamin D deficiency, rather than sufficiency.
While it is possible that vitamin D does not reduce your risk of being diagnosed with pneumonia, only well designed clinical trials can help us know for sure. Future studies using daily doses high enough to achieve average 25(OH)D levels of 50 ng/mL are sorely needed.