Vitamin D in ocular and systemic health

Abstract

Accumulated data supports the argument that vitamin D possesses several biological and molecular actions apart from its role in calcium absorption and facilitation of gene expression. Vitamin D deficiency has been an associated risk factor for cardiovascular disease, metabolic syndrome and ocular complications. The aim of this review is to summarise the most relevant data regarding these associations and to try to clarify whether, and to what extent, oral vitamin D supplementation could be used as a beneficial intervention in such diseases. Vitamin D is produced in skin exposed to sunlight UVB radiation and is then metabolised by the kidney into calciferol, which is an active form. The main function of vitamin D is to promote calcium and phosphorus absorption, and studies have shown that a lack of it plays an important role in ocular conditions, such as age-related macular degeneration and diabetic retinopathy. Recent studies have suggested that vitamin D may protect the diabetic retina; however, other vitamin D-associated conditions (diabetes, hypertension and cardiovascular diseases) may result in secondary ocular manifestations and the potential for sight-threatening complications. The purpose of this review is to describe the current literature on the role of vitamin D in ocular and systemic wellness. However, more research is needed to determine if increasing levels of this vitamin can assist in preventing age-related macular degeneration or diabetic retinopathy. Since vitamin D is a circulating steroid hormone, its receptors are found in almost every cell in the human body, and this suggests that vitamin D might have a very broad role for overall health. However, there is still demand for further research to clarify the clinical use of vitamin D in the prevention and treatment of various chronic diseases.