vitamin
1. Vitamin D: Vitamin D is an essential nutrient for the human body, its active product 1,25 (OH)2D is an important hormone to maintain bone health, 1,25(OH)2D The main role is to promote the absorption of calcium by the small intestine, which is conducive to the normal mineralization of bones, the concentration of serum 25 ( OH) D is an important indicator to judge the nutritional level of vitamin D, the main source of vitamin D in the human body is the skin 7-dehydrocholesterol generated by ultraviolet radiation in the sun, and there are few types of foods rich in vitamin D, such as fat More wild marine fish and sun-exposed mushrooms, other species of food content is very low or deficient, so if the sun exposure is insufficient, it is easy to develop vitamin D deficiency or deficiency.
If you encounter special circumstances, can not often go out for outdoor activities, especially in the winter can not fully expose the skin, it is not easy to obtain vitamin D through sun exposure, it is generally believed that serum 25 (OH) D is lower than 20 ng / ml for vitamin D deficiency, 20- 30 ng / ml for vitamin D is not enough, the incidence of vitamin D deficiency in our population is high, especially in winter, a multicenter national vitamin D nutrition status survey results show that the average serum 25 (OH) D concentration in summer is 22.2 ng/ml, 13.2 ng/ml in winter, vitamin D deficiency in 43.8% of postmenopausal women in summer, vitamin D deficiency in 86.5% of postmenopausal women, vitamin D deficiency in 61.4% of postmenopausal women in winter, and vitamin D deficiency in 91.2% of postmenopausal women.
According to the consensus of the Osteoporosis and Bone Mineral Salt Disease Branch of the Chinese Medical Association, for people with vitamin D deficiency or deficiency, it is necessary to correct vitamin D deficiency or inadequacy through sun exposure or vitamin D supplementation, in the season when the skin of the limbs can be exposed, such as summer, try to obtain vitamin D through sun exposure, require limb exposure when receiving sun exposure, do not use sunscreen, do not separate glasses, do not use umbrellas, the time selection is between 10 points and 14 points, the irradiation time is 5 - 10 minutes, the frequency is 2 - per week 3 times, the elderly and individuals with darker skin color need longer sun exposure, and in the season when the skin of the limbs cannot be exposed, the amount of vitamin D supplementation can be determined according to the basal 25 (OH)D level, the Chinese Nutrition Society recommended in 2013 The intake of vitamin D for adults in China is 400 IU / d, the recommended intake of 600 IU / d for people over 65 years old, and the maximum tolerable intake is 2 000 IU / d, according to Sacheck et al. and recent domestic research results, If oral administration of 800 - 2 000 IU of vitamin D3 per day or intramuscular injection of 600,000 IU of vitamin D2 every 6 months can increase serum 25 (OH) D by approximately 10 ng / ml, if the concentration of serum 25 (OH) D can be maintained above 30 ng / ml, anti-osteoporosis drugs will work better, but if the concentration of 25 (OH) D is too high due to overdose, such as above 40 - 45 ng / ml, may gradually lose the protective effect on the bone.
Vitamin D also has the function of stimulating the differentiation and function of various immune cells, promoting the production of antimicrobial peptides by macrophages to enhance the respiratory tract's ability to resist bacteria and viruses, which may help prevent acute respiratory infections.