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Vitamin D- Benefits, Deficiency Symptoms And Food Sources

Alternative names :- Sunshine vitamin

Vitamin D is a collective term for a group of compounds with antirachitic activity (they prevent or cure rickets), and includes ergocalciferol (D2), cholecalciferol (D3), and the dihydrotachysterols (DHT2 and DHT3), together with their biologically active metabolites. Vitamin D is now recognized as a hormone. At one time only D2 was used as a food additive, and hence plasma 25-(OH)D2 was an index of exogenous vitamin D2; now, vitamin D3 is also being increasingly used.

Vitamin D is a fat-soluble vitamin which acts like a hormone, regulating the formation of bone and the absorption of calcium and phosphorus from the intestine. It helps to control the movement of calcium between bone and blood, and vice versa.

Benefits and functions of Vitamin D

• Vitamin D aids directly in the small intestinal absorption of calcium, and increases the synthesis of intestinal calcium-binding protein.
• Vitamin D helps deposition in the bones, probably of mineralized rather than amorphous calcium phosphate, by supplying calcium and phosphorus in proper concentrations to the bony matrix.
• It also helps regulate the amount of phosphorus in the body as well as assisting in a healthy heart and nervous system.

Recommended dosage of Vitamin D

The Recommended Dosage for vitamin D are :-

• Adults - 400 IU (10 mcg )
• Pregnant women - 600 IU ( should be consult with a doctor)

Deficiency symptoms of Vitamin D

Deficiency of vitamin D occurs with :-

1. inadequate exposure to sunlight
2. inadequate intake
3. drugs that antagonize vitamin D action
4. altered metabolism due to damaged liver or kidneys.

This leads to diminished absorption of calcium and consequent low blood calcium, which may produce tetany.

Low plasma calcium stimulates the parathyroids to mobilize bone calcium for raising the plasma calcium level. The bones are thus depleted of calcium salts. This most commonly manifests as: (i) rickets during skeletal growth in children; or (ii) osteomalacia in adults due to increased demand of calcium during pregnancy or deficient intake in old age. Vitamin D deficiency exacerbates osteoporosis and increases the risk of skeletal fractures.

Macrobiotic diet consists of unpolished rice, pulses, and vegetables with a high fiber content, with a small addition of seaweeds, fermented foods, nuts, seeds and fruits. Fat is permitted in the diet but fish was initially excluded. This diet produces vitamin D deficiency in children. The avoidance of dairy products along with a high fiber diet damages bone development in young children.

Food sources of Vitamin D

The major sources are egg yolk, dandelion greens, oatmeal, salmon, sardines, milk and butter Vitamin D is found in the livers of all animals and is plentiful in oils derived from fish liver. The vitamin D content of food depends upon exposure of the fowls or milch animals to sunlight. Vitamin D is usually added to commercial baby food milk powders.

Toxicity

Massive vitamin D therapy can be harmful. With increasing doses of vitamin D, almost all the dietary calcium is absorbed; it probably also causes reabsorption of calcium from the bones. The serum calcium level is therefore raised. With this rise, the activity of the parathyroid gland is depressed and the serum phosphorus level rises. The increased serum levels of both calcium and phosphate result in abnormal calcification in the kidneys, blood vessels, and other organs.