Vitamin D is known as the "sunshine vitamin." Though sunlight itself doesn't carry this essential nutrient, exposure to sunlight can cause this vitamin to form in the body. Vitamin D carries out important functions in bone development and in the maintenance of calcium levels. A deficiency of this vitamin may occur if you do not get enough sun exposure. In that case you should take or receive a nutritional supplement.
Activation of Vitamin D
Vitamin D is a fat-soluble vitamin which can be obtained both from the diet and by exposure to sunlight. Cholesterol is an important chemical in animal cells that plays a variety of functions, and all cells can synthesize some amount of this important substance. Vitamin D has a structure that is similar to cholesterol. Sunlight can react with some of the early forms of cholesterol and "activate" it, converting it to vitamin D. The form of vitamin D that is created by sunlight exposure is vitamin D3; another form, vitamin D2, is found in plant products and has similar vitamin activity.
Actions of Vitamin D
Vitamin D performs important functions in bone formation and calcium maintenance. Vitamin D increases the absorption of calcium and phosphate; the vitamin also prevents the loss of these minerals from urine. In the bone, vitamin D stimulates the bone forming cells, known as osteoblasts, to deposit calcium and phosphate. Thus, vitamin D is essential in bone development and maturation.
Amount of Sun Exposure Needed
Ultraviolet rays in sunlight are critical to the formation of vitamin D. Specifically, UV B, in the wavelength of 290 to 320 nanometers, has the greatest effect. According to the Office of Dietary Supplements, the amount of Vitamin D that can be created through exposure to sun is sufficient to meet the vitamin requirements for most people. Certain people, however may be at risk. Older people, who may not get adequate sun exposure, are at risk of deficiency. People with dark skin color are also prone to development of this deficiency as the melanin pigments absorb more of the UV rays. The breastfed, and especially those of African descent, are also at risk, as human milk has low quantities of this vitamin.
Vitamin D Deficiency
Vitamin D deficiency causes different diseases in children and adults. In children, because the bone is immature, a disease known as rickets may develop. These children have malformed bone with bowing of legs and soft skull bones. Bone pain, dental deformities and muscle weakness are also common symptoms. In adults, a similar disease -- osteomalacia -- may result. Osteomalacia is similar to rickets but without the bone deformity. It is characterized by soft bones, bone pain, muscle weakness and a tendency to fracture easily. Both conditions are treated with vitamin D.
References
- "Lippincott's Illustrated Reviews: Biochemistry"; Richard A. Harvey; 2010
- Office of Dietary Supplements: Vitamin D
- PubMed Health: Osteomalacia
- PubMed Health: Rickets
- "Guyton and Hall Textbook of Medical Physiology"; John E. Hall, Ph.D.; 2010
