Vitamin D, commonly referred to as the “sunshine vitamin,” plays an important role in your health. It is the only vitamin that can be made by the human body from sunshine. Research is suggesting a strong link between vitamin D status and basic cognitive function, mood and overall mental health. The recommended adequate intake (AI) level for the active form of vitamin D (vitamin D3 or cholecalciferol) is 5 micrograms (mcg) for adults aged 31 to 50 years. After the age of 50, the AI increases to 10 mcg.
Vitamin D: How it is Made
Vitamin D is unique because it is made by the body when the skin is exposed to ultraviolet rays from the sun. When this happens, a cholesterol-like compound is converted to a vitamin D precursor and then to vitamin D3, (or cholecalciferol). Vitamin D3 is activated by enzymes from the liver and the kidney. When activated, vitamin D functions as a hormone. Just 15 minutes under the sun (for most people, without sunscreen), three times per week makes enough vitamin D. It can be stored for several months in the body.
Vitamin D deficiency, or hypovitaminosis D, is common in Americans, especially those who live in colder, northern climates, as well as the elderly population. This is because our ability to produce the vitamin declines with age. Although the AI is expressed in mcg, most vitamin D supplements are expressed in International Units (IU). One IU = 0.025 mcg cholecalciferol.