The topic I am going to discuss with you today is how to take vitamin and micronutrient supplements? As we know, the main nutrients in the human body are macronutrients and micronutrients. Macronutrients refer to protein, fat and carbohydrates; micronutrients refer to vitamins, minerals and other dietary ingredients; vitamins include vitamin A, D, B vitamins and vitamin C; minerals include macronutrients and trace elements, among which macronutrients are calcium, phosphorus, magnesium, potassium, sodium, chloride and sulfur; trace elements are iron, zinc, selenium, iodine and copper. Many parents often confuse vitamins and trace elements, especially vitamin D and calcium, and think that calcium is all that is needed. I will talk about vitamin D and calcium as macronutrients first, and we will tell you about other vitamins and trace elements one after another. The main source of vitamin D is the 7-dehydrocholestrol in the basal layer of the skin, which is converted to vitamin D3 by ultraviolet radiation from sunlight, and then catalyzed by the liver and kidneys as active vitamin D3 to play its role in promoting calcium absorption and calcium deposition, followed by the intake of vitamin D in food. For example, every 1000 ml of breast milk contains only 60 units of vitamin D, and 1000 ml of cow’s milk (not formula milk) contains 40 units of vitamin D. Therefore, the main source of vitamin D for breastfed infants and toddlers is the skin through ultraviolet radiation. There are many factors that make UV radiation insufficient, such as the vast territory of China, the length of sunshine in the north and south is different; seasonal changes, sunshine time and intensity are different; modern cities, tall buildings, blocking the light; urban traffic congestion, too much construction, air pollution in some areas, ultraviolet light in the sun is blocked by dust, smoke, clothing and ordinary glass, etc. The air pollution in some areas is blocked by dust, smoke, clothes and ordinary glass, etc. In summary, infancy and early childhood due to rapid growth and development, the need for large, insufficient intake, prone to vitamin D deficiency caused by calcium deficiency and rickets, must adhere to comprehensive preventive measures, reasonable supplementation of vitamin D, do not be misled by false propaganda, such as calcium supplementation does not need to supplement vitamin D, the daily amount of vitamin D plus prevention is easy to poison, as long as the sun is enough, etc..