Vitamin D in ocular and systemic health

Solani D Mathebula

doi:10.4102/aveh.v74i1.35

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 itplays 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 forsight-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.

Highlights

Sunlight exposure has always been important as an energy source in the food chain
Results from the study by Payne et al.[31] found that diabetic patients have lower serum vitamin D levels than those without diabetes. They concluded that patients at risk for Diabetic retinopathy (DR) should consider the use of vitamin D supplements
This study has found that patients with DR, especially the proliferative form, are more likely to have insufficient serum vitamin D levels than people without diabetes, suggesting a link between vitamin D deficiency and DR.[32]

Summary

Introduction

Sunlight exposure has always been important as an energy source in the food chain. For millions of years phytoplankton has been converting the sun’s energy by photosynthesis into energyproducing sugars.[1,2,3] Vitamin D ( known as the sunshine vitamin) is known to promote calcium absorption in the digestive system preventing rickets in children, and osteomalacia (non-specific throbbing, aching, bone pain, weakness and muscle discomfort) in adults.[1,2,3,4,5,6,7,8,9] Vitamin D deficiency and insufficiency coincide with osteoporosis (disorder characterised by low bone mineral density and increased risk of fracture). Calcium ions are essential for a large variety of cellular and metabolic processes in the body.[9] The first clinical description of rickets was made in 1651 but it was only in 1922 that an association was found between lack of sunlight and rickets, and that vitamin D was capable of curing rickets.[1]

Objectives

Results

Conclusion