Not only are such deficiencies common, but vitamin D deficiency is implicated in most of the diseases of civilization. Vitamin D’s final metabolic product targets more than 200 human genes in a wide variety of tissues. One of the most important genes vitamin D up-regulates is for cathelicidin, a naturally occurring broad-spectrum antibiotic.
Since vitamin D deficiency is both endemic and is associated with numerous diseases, it is one of the most important medical problems in modern society. Treatment of vitamin D deficiency in otherwise healthy patients must be individualized due to the numerous factors affecting vitamin D levels. Steps should be taken to keep patients with chronic diseases associated with vitamin D deficiency, especially internal cancers, in the higher normal range of vitamin D blood levels.