Despite its name, vitamin D is not a regular vitamin. It’s actually a steroid hormone. It refers to a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, iron, magnesium, phosphate, and zinc. In humans, the most important compounds in this group are vitamin D3 and vitamin D2. It is also produced when ultraviolet-B (UVB) radiation from sunlight strikes the skin and triggers vitamin D synthesis.
Vitamin D is naturally present in very few foods, added to others, and available as a dietary supplement. It is impossible to get enough vitamin D from foods.
Vitamin D obtained from sun exposure, food, and supplements is biologically inert and must undergo two hydroxylations in the body for activation. The first occurs in the liver and converts vitamin D to 25-hydroxyvitamin D 25(OH)D, also known as calcidiol. The second occurs primarily in the kidney and forms the physiologically active 1,25-dihydroxyvitamin D 1,25(OH)2D, also known as calcitriol.
Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and to prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.
According to an article from the Journal of Pharmacology & Pharmacotherapeutics published on PubMed Central® (PMC) titled: Vitamin D: The “sunshine” vitamin by Rathish Nair and Arun Maseeh
“Vitamin D insufficiency affects almost 50% of the population worldwide. This pandemic of hypovitaminosis D can mainly be attributed to lifestyle and environmental factors that reduce exposure to sunlight, which is required for ultraviolet-B (UVB)-induced vitamin D production in the skin.”
“The high prevalence of vitamin D insufficiency is a particularly important public health issue because hypovitaminosis D is an independent risk factor for total mortality in the general population. Emerging research supports the possible role of vitamin D against cancer, heart disease, fractures and falls, autoimmune diseases, influenza, type-2 diabetes, and depression.”
Learn more! Read the article: Vitamin D: The “sunshine” vitamin by Rathish Nair and Arun Maseeh
PubMed Central® (PMC) is a free full-text archive of biomedical and life sciences journal literature at the U.S. National Institutes of Health’s National Library of Medicine (NIH/NLM). In keeping with NLM’s legislative mandate to collect and preserve the biomedical literature, PMC serves as a digital counterpart to NLM’s extensive print journal collection. Launched in February 2000, PMC was developed and is managed by NLM’s National Center for Biotechnology Information (NCBI).