The physiological function of vitamin D

For the steroid derivatives, is a fat-soluble vitamins. Vitamin D and calcification of the animal bones, it is also known as calciferol. It has anti-rickets role in the animal's liver, milk and egg yolk content of more, especially the most abundant fish liver oil. Natural vitamin D, there are two, lysergic calciferol (D2) and cholecalciferol (D3). Vegetable oil or yeast ergosterol contained in (24 - methyl -22 dehydrogenation -7 - dehydrocholesterol), activated by ultraviolet light can be converted to vitamin D2. In the animal skin of 7 - dehydrocholesterol by ultraviolet radiation can also be converted into vitamin D3, ergosterol, and therefore 7 - dehydrocholesterol vitamin D is often referred to as the original. In animals, food, vitamins D2 and D3 can be absorbed in the small intestine via lymphatic Xishouruxue, mainly by liver uptake, and then stored in adipose tissue, or other containing lipid-rich tissues. Of vitamin D in the human body is mainly D3, vitamin D3 from the original (7 - dehydrocholesterol). Therefore, prevention of vitamin D over the lack of sun exposure is the main one way. Vitamin D2 and D3 Jie Wei colorless crystals, nature relatively stable, not easily damaged, regardless of vitamin D2 or D3, itself no biological activity, they must conduct a series of in vivo metabolic changes in them to become active substances. This shift is mainly in the liver and kidney in the hydroxylation reaction carried out in the first hydroxylation in the liver into a 25 - hydroxy vitamin D3, and then further hydroxylation in the kidney into 1,25 - (OH) 2-D3, which is vitamin D3 active form in the body. 1,25 - dihydroxy vitamin D3 regulation of significant calcium and phosphorus metabolism activity (Figure 11). It promotes small intestinal absorption and transport of phosphorus, but also the promotion of renal tubular reabsorption of calcium and phosphorus. In the bones, both contribute to new bone calcification, but also the promotion of calcium from the bone marrow stroma-free out of the old, so that bone constantly updated at the same time, while maintaining calcium balance. Because 1,25 - dihydroxy vitamin D3 in the kidney into the blood circulation after synthesis, role in the small intestine, renal tubules, bone tissue and other long-distance target tissue, generally in line with the characteristics of hormones, so it was classified as vitamin D hormone material. Vitamin D and have a moderating role of calcium, so is the normal development of bones and teeth are necessary. Especially in pregnant women, infants and young big requirements. If at this time of vitamin D insufficient, then the blood calcium and phosphorus lower than normal, there will be soft and deformed bones: occurs in children is called rickets; in pregnant women as a bone softening disease. 1 gram of vitamin D for the 40 million international units. Infants and young children, pregnant women and lactating and a daily requirement is 400 ~ 800 units.

Vitamin D in 1926 by a chemist Carl first extracted from cod-liver oil. It is light yellow crystals, melting point 115 ~ 118 ℃, insoluble in water, soluble in ether and other organic solvents. It is chemically stable, at 200 ℃ still maintain biological activity, but susceptible to UV damage, therefore, pharmaceutical vitamin D should be kept in brown bottle. The physiological function of vitamin D is to help the body absorb phosphorus and calcium, are necessary to build bone material, and therefore lack of vitamin D will get rickets. In the cod liver oil, animal liver, egg yolk, rich in its content. Of vitamin D synthesis in the human body with the sun, and therefore, proper lighting conducive to health.

The daily demand: from 0.0005 to 0.01 mg. 35 g herring fillet, salmon fillet 60 grams, 50 grams of eel or 2 eggs plus 150 grams of mushrooms. Only a few people break only need to eat the amount of vitamin D-containing food or preparation.

Effects: Vitamin D is the development of bone and cartilage of the engine, make the teeth hard. Pairs of nerves is also very important, and inhibition of inflammation.

Side effects: Researchers estimate that the long-term daily intake of 0.025 mg of vitamin D harmful. The possible consequences are: nausea, headache, kidney stones, muscle atrophy, arthritis, arteriosclerosis, high blood pressure, mild poisoning, diarrhea, thirst, weight loss, polyuria, and nocturia and other symptoms. Severe poisoning will damage the kidneys, so that soft tissue (such as heart, vascular, bronchial, stomach, renal, etc.) calcification.