Authors' reply: Vitamin D deficiency

Abstract

589 L e t t e r t o t h e E d i t o rDear Sir, We thank Lange and Cegolon for their letter. Regarding extraskeletal benefi ts, we agree that vitamin D potentially regulates many other cellular functions in addition to its role in calcium and bone homeostasis. The vitamin D receptor (VDR) is nearly universally expressed in nucleated cells and about 3% of the human/mouse genome is regulated by 1,25-dihydroxyvitamin D, the active form of vitamin D. Thus, the vitamin D endocrine system has a much broader spectrum of activity than calcium or bone homeostasis; in this regard, the vitamin D-VDR system resembles that of other nuclear receptor ligands, such as thyroid hormones.(1-3)It is thus not unexpected that numerous studies have demonstrated an association between vitamin D defi ciency and an increased risk of more than a dozen cancers (including that of the colon, prostate, breast and pancreas), autoimmune diseases (including types 1 and 2 diabetes mellitus, rheumatoid arthritis, Crohn's disease and multiple sclerosis), infectious diseases and cardiovascular diseases.(4) However, most randomised controlled trials on the topic do not have an adequate dosing range to provide level I evidence on whether vitamin D can reduce the risk of these chronic diseases. We therefore agree with the Endocrine Society task force's most recent vitamin D guideline, which emphasised the importance of preserving musculoskeletal health and preventing childhood rickets and adult bone disease.(4) Vitamin D supplementation or treatment is usually inexpensive and cost-effective, particularly in treating medical entities such as osteoporosis, rickets and osteomalacia. It is less clear how much costs and resources are required for other preventive indications. We acknowledge the rapidly changing science in this fi eld and that recommendations will likely need to be revised as the evidence grows.We also agree with Lange and Cegolon that foods vary in their vitamin D content. Table I, which was taken from a review paper, shows the dietary, supplemental and pharmaceutical sources of vitamins D 2 and D 3 .(4) The list is not exhaustive and is provided as a guide.Yours sincerely,