Previtamin D3

Previtamin D3 is a type of vitamin D that is produced in the skin as a result of exposure to ultraviolet B (UVB) radiation. It is an important precursor to the active form of vitamin D, known as calcitriol or vitamin D3.

Production

Previtamin D3 is produced in the skin when the compound 7-dehydrocholesterol, which is naturally present in the skin, absorbs UVB radiation. This causes a chemical reaction that converts 7-dehydrocholesterol into previtamin D3. This process is dependent on the intensity and duration of UVB exposure, as well as the individual's skin type and age.

Conversion to Vitamin D3

Once formed, previtamin D3 undergoes a heat-dependent isomerization in the skin to form cholecalciferol, also known as vitamin D3. This process is non-enzymatic and occurs as a result of the body's natural heat. Cholecalciferol is then transported to the liver, where it is converted into calcidiol, the main circulating form of vitamin D. Finally, calcidiol is converted into calcitriol, the active form of vitamin D, in the kidneys.

Role in Health

Previtamin D3, and the vitamin D3 it is converted into, play crucial roles in maintaining human health. They are essential for the absorption of calcium and phosphorus from the diet, which are necessary for the formation and maintenance of healthy bones and teeth. Vitamin D3 also plays a role in immune system function and may have protective effects against certain types of cancer.

Deficiency

A deficiency in previtamin D3, and therefore vitamin D3, can lead to a number of health problems. These include rickets in children, which is characterized by soft, weak bones, and osteomalacia in adults, which is characterized by softening of the bones. Vitamin D deficiency can also lead to osteoporosis, a condition characterized by low bone mass and increased risk of fractures.

See Also

• Vitamin D
• 7-dehydrocholesterol
• Cholecalciferol
• Calcidiol
• Calcitriol

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