In the far reaches of Mongolia, Harvard researchers worked together with local health researchers, diligently looking for an inexpensive treatment that might reduce respiratory infections in kids during the winter months. In children who tested low in their blood levels of vitamin D at the beginning of the winter, supplementing with vitamin D cut the risk of getting lung infections in half.
The amount of vitamin D used in the study was 300 IU. Since this study was run, the U.S. Institute of Medicine has raised the recommended dosage for most children up to 400 IU and even up to 1000 IU for children especially at risk of vitamin D deficiency.
This study was a well-controlled randomized trial that clearly pointed a finger to one more protective action of vitamin D: protecting lung tissue from infection. Pediatrics 2012
Consider: If you are suffering with recurrent bronchitis or pneumonia, get your vitamin D levels checked, try to be in the robust range of 60-90, identify and avoid any potential allergens in food and/or the environment, and get your thyroid checked, as recurrent infections can also be a low level of the active T3 signaling molecule.