Vitamin D: The Challenge of Bridging the Gap and the Rationale for Supplementation

Abstract

Vitamin D is classified amongst nutrients as a fat-soluble vitamin, which is consumed from food, including fortified food or supplements. It can also be synthesized by exposure of the skin to sunlight. Vitamin D facilitates absorption and retention of calcium and phosphorus both of which are critical for bone and teeth formation. Many organs and tissues have vitamin D receptors, which suggest important roles in the body beyond bone and research has shown that vitamin D regulates inflammation and immune function with potentially beneficial effects on the health of the brain, the cardiovascular system, the endocrine system, and other metabolic pathways. Few foods contain vitamin D. Oily fish, butter, liver, eggs, milk, and fortified foods including some breakfast cereals and spreads are the main dietary sources. Whilst most of the requirement for vitamin D is considered to come from casual exposure to sunlight, there is considerable debate on the sufficiency of sunlight to achieve acceptable blood levels of vitamin D because a significant proportion of the population does not achieve adequate skin exposure. Studies from many countries, including those in sunnier regions, such as Southern Europe, the Middle East and Australia demonstrate low vitamin D levels in a high proportion of the populations. Because so few foods contain vitamin D, supplementation with vitamin D should be recommended to bridge this gap.