This is the chemical that doctors usually measure to diagnose vitamin D deficiencies. The first stop is in the liver, where vitamin D picks up extra oxygen and hydrogen molecules to become 25-hydroxyvitamin D, or 25(OH)D.
#Models in vitamin d video skin
The sun's energy turns a chemical in your skin into vitamin D 3, which is carried to your liver and then your kidneys to transform it to active vitamin D.
Because their function is almost identical, D 2 and D 3 are lumped together under the name vitamin D - but neither will function until the body works its magic (see figure). In contrast, most dietary supplements are manufactured by exposing a plant sterol to ultraviolet energy, thus producing vitamin D 2. Sunlight is the key: Its ultraviolet B (UVB) energy converts the precursor to vitamin D 3. The natural type is produced in the skin from a universally present form of cholesterol, 7-dehydrocholesterol.
#Models in vitamin d video full
Coming full circle in the modern world, this substance may actually come to fit the technical definition of a vitamin. Instead, we increasingly depend on artificially fortified foods and pills to provide this vital nutrient. But it breaks the other rules for vitamins because it's produced in the human body, it's absent from all natural foods except fish and egg yolks, and even when it's obtained from foods, it must be transformed by the body before it can do any good.Īs our habits change, most of us cannot rely on our bodies to produce vitamin D the old-fashioned way. True, it's essential for health, and only minuscule amounts are required. Vitamins play a crucial role in our body's metabolism, but only tiny amounts are needed to fill that role.Īlthough vitamin D is firmly enshrined as one of the four fat-soluble vitamins, it is not technically a vitamin. Ever since, scientists have defined vitamins as organic (carbon-containing) chemicals that must be obtained from dietary sources because they are not produced by the body's tissues. Vitamin D is one of the 13 vitamins discovered in the early 20th century by doctors studying nutritional deficiency diseases. Research results suggest that vitamin D may have a role in other aspects of human health.
But solving the problem of rickets was only the beginning of research into vitamin D. Within a decade, the fortification of foods with vitamin D was under way, and rickets became rare in the United States. Vitamin D was discovered in 1920, culminating the long search for a way to cure rickets, a painful childhood bone disease.