Vitamin D is an essential nutrient for the maintenance of our health. Its main function is the regulation of calcium and phosphate levels, so it has a nutritional role in the maintenance of healthy bones and teeth.
Vitamin D levels
Vitamin D is produced in the human skin from 7-dehydrocholesterol by the action of UVB rays. This vitamin D is biologically inactive and needs to be metabolized to produce different compounds that are active and responsible for multiple functions in the body.
When UV rays come into contact with the skin, 7-dehydrocholesterol is transformed into cholecalciferol or vitamin D3. This, which is actually a prohormone, is biologically inactive. To be functional, it must undergo two transformations, the first in the liver forming calcidiol or 25-hydroxycholecalciferol and the second in the kidney forming calcitriol or 1-alpha-25-hydroxycholecalciferol which is the active form.
The main function of vitamin D is the regulation of calcium and phosphorus homeostasis, however, in recent years, many other unrelated functions have been identified in the immune, endocrine, neuromuscular or hematopoietic systems. Beneficial effects of vitamin D consumption have even been observed in some diseases such as rheumatoid arthritis or multiple sclerosis.
The vitamin D needed by the body comes from two sources: synthesis in the skin in the presence of sunlight and the intake of foods that contain it. In the human species, the main source is skin synthesis and a smaller proportion depends on food. However, there are external agents that can hinder this cutaneous synthesis, such as latitude, advanced age and dark-colored skin, and in these cases it is important to guarantee an adequate intake.
There are very few foods that contain vitamin D naturally, being fatty fish such as salmon or trout the richest in this compound, in addition to fish liver oil which is the richest source. Nowadays, we can find many foods fortified with vitamin D.
13.5 million variants
Sinnot-Armstrong N, Tanigawa Y, et al. Genetics of 35 blood and urine biomarkers in the UK Biobank. Nature Genetics, 18 Jan 2021, 53(2):185-194
National Library of Medicine (NIH). Office of Dietary Supplements [April 2022]
National Health Service in England (NHS). Vitamin D [August 2020]