Remember when your parents would remind you to take your vitamins every morning before going to school? Well, that advice might very well be what spells the difference between a long bout of respiratory infections and a short one. Many studies indicate that those who have high vitamin D levels experience shorter durations of respiratory infections or milder symptoms, while those with low vitamin D levels are found to be more prone to a whole gamut of respiratory infections. The jury is still out on whether or not vitamin D can be used to treat bronchitis, but as a vitamin, it is important and integral to a healthy functioning body.