Laboratory-grown gingival cells treated with vitamin D boosted their production of an endogenous antibiotic, and killed more bacteria than untreated cells, according to a new study. The research suggests that vitamin D can help protect the gums from bacterial infections that lead to gingivitis and periodontitis. Periodontitis affects up to 50 percent of the US population, is a major cause of tooth loss, and can also contribute to heart disease. Most Americans are deficient in vitamin D.