If I don't expose myself too much to the sun, should I be concerned about a vitamin D deficiency?

Just like vitamins A, E, and K, vitamin D is fat-soluble and can be stored in fatty tissues. It comes in two forms: vitamin D2 or ergocalciferol, and vitamin D3 or cholecalciferol. The latter is the active form. It is synthesized by the body and forms in the skin when it is exposed to sunlight. Additionally, vitamin D can also be found in cereals and dairy products. Both forms are metabolized by the liver and kidneys and transformed into active vitamin D or calcitriol. This promotes the absorption of calcium and phosphorus by the intestine. These minerals are then incorporated into the bones for mineralization.

The sun serves as an infinite source of vitamin D. As such, it is necessary to expose oneself to it for at least 10 to 15 minutes, 2 to 3 times per week, ideally between 11 a.m. and 2 p.m. Individuals with darker skin or older individuals require increased sun exposure. At a minimum, it is appropriate to expose the face, forearms, and hands. Consequently, a deficiency is a concern for those who tend not to go outside. This is particularly prevalent in winter, especially among residents of northern countries. Moreover, breastfed babies who are not sufficiently exposed to ultraviolet rays may suffer from a vitamin D deficiency and develop rickets. Insufficient consumption of foods rich in vitamin D can also lead to a vitamin D deficiency.

Vitamin D deficiency primarily manifests as fatigue, muscle pain, and bone pain. These symptoms occur in all individuals, regardless of their age or gender. In infants, muscle cramps or tetany are the first signs of a vitamin D deficiency, leading to low levels of calcium in the blood. A severely deficient baby then becomes rachitic, with an entirely soft skull. Furthermore, they will have difficulty sitting and crawling due to the fragility of their bones. They will also take longer to walk. Additionally, since their bone growth is impaired, their spine may curve abnormally, causing scoliosis.

In children and adolescents, a varus or valgus condition of the knees can result from a severe deficiency in vitamin D. In adults, it can cause bone fragility and disorders in the spine, pelvis, and legs.