The absorption of calcium needs vitamin D, and the metabolic balance of calcium is also affected by vitamin D. You can choose to take cod liver oil (vitamin AD) or vitamin D3 preparation, or you can promote the conversion of cholesterol in the skin into vitamin D by sunbathing. According to the nutritional needs of infants and young children, the Chinese Nutrition Association suggests supplementing vitamin D400-800IU every day.

Vitamin D is converted from the corresponding vitamin D by ultraviolet irradiation. Provitamin D is a cyclopentane dihydrophenanthrene compound. The 5-position and 7-position in the B-ring of vitamin D are double bonds, which can absorb light quantum with wavelength of 270 ~ 300 nm, thus starting a series of complex photochemical reactions and finally forming vitamin D.

Extended data;

The main function of vitamin D is to regulate calcium and phosphorus metabolism, promote intestinal calcium and phosphorus absorption and bone calcification, and maintain the balance of blood calcium and phosphorus. Active vitamin D acts on the nucleus of intestinal mucosa and promotes the biosynthesis of troponin. Troponin combines with calcium to form a soluble complex, thus accelerating the absorption of calcium.

Vitamin D promotes the absorption of phosphorus, which may be indirectly produced by promoting the absorption of calcium. Therefore, the total effect of active vitamin D on calcium and phosphorus metabolism is to increase blood calcium and phosphorus and make the plasma calcium and phosphorus level reach saturation level. It is beneficial for calcium and phosphorus to deposit on bone tissue in the form of bone salt and promote calcification of bone tissue.

Baidu encyclopedia-vitamin d

Baidu encyclopedia-calcium supplementation

Baidu encyclopedia-excessive exercise