Vitamin A deficiency on the growth and development of infants and young children: 1, the impact on visual development. Vitamin A constitutes the visual cells within the light-sensitive substances “retinal”, when the baby body lacks vitamin A, there will be a decline in the ability to see dark vision, night to see things clearly, can lead to serious night blindness. In addition, vitamin A is also an important substance to ensure the integrity of the conjunctiva, corneal epithelial cells, the lack of the body will appear abnormal keratinization and corneal softening, tear secretion is reduced, the formation of dry eye. 2, the impact on growth and development. Vitamin A can affect the function of osteoblasts and osteoclasts, the lack of which can affect bone development, recently found that short stature of vitamin A deficiency in children with reduced secretion of nocturnal growth hormone, infant insulin-like growth factor-I (IGF-1) concentration is also related to plasma vitamin A levels, to short stature of children with neurosecretory disorders of growth hormone supplementation of vitamin A can be restored or at least partially restored nocturnal growth hormone secretion. Short stature is often accompanied by vitamin A deficiency. 3, the effect on hematopoietic function. Vitamin A deficiency will reduce the transferrin synthesis ability, so that hemoglobin synthesis process of iron from the liver and other tissues of the transfer process is blocked. Medical research has found that the incidence of iron deficiency anemia in children with vitamin A deficiency is much higher than in children with normal vitamin A levels. 4, the impact on immune function. Vitamin A deficiency can lead to atrophy of immune organs, affect the number, differentiation and function of immune cells, destroy the mucosal barrier, reduce the generation of antibodies. Lack of vitamin A children, respiratory tract, urinary tract and digestive tract epithelial cells will lose the barrier function, the immune system development is limited, the resistance to germs decreased, susceptible to respiratory, urinary tract and digestive tract infectious diseases. Why does China advocate vitamin AD supplementation? Vitamin D deficiency is a global problem, while vitamin A deficiency varies from country to country and is related to different races, dietary structures, economic conditions, environmental climate and other factors. The World Health Organization (WHO) suggests that in some developing countries, large doses of vitamin A supplementation should be taken (e.g., one-time supplementation of 100,000-200,000 International Units (IUs) of vitamin A every 4-6 months). Chinese children’s health experts suggest that a small daily dose of vitamin AD supplementation is more suitable for China’s national conditions, with good compliance and high safety. Vitamin AD supplementation has a synergistic effect with adequate vitamin D is to ensure the absorption of calcium from food, to ensure bone growth and development of the prerequisites, the lack of which will lead to rickets. Vitamin A is also very important for the development of bones, the lack of which will cause degeneration of bone tissue, affecting the absorption of calcium, so that the amount of bone and bone density decline, resulting in delayed bone development, but also affect the development of teeth. Therefore, AD supplementation plays a synergistic role in the bone development of infants and young children. Vitamin A helps to maintain the integrity of the mucous membrane of the respiratory tract, enhance the defense ability of the epithelial tissue, and can improve the function of immune cells, promote antibody production. Vitamin D is also important for activating the immune system, and recurrent respiratory infections in children are associated with low levels of vitamin D. Therefore, A D supplementation will have a synergistic effect on the development of bones in infants and children. Therefore, A D supplementation will achieve the effect of 1+1>2, and improve the baby’s resistance. The optimal dose of vitamin AD supplementation according to the Chinese Nutrition Society recommended nutrient intake, and the Pharmacopoeia of the People’s Republic of China clearly stipulates that the optimal ratio of vitamin AD supplementation for children aged 0-7 years old is 3:1, i.e., the supplemental dosage of vitamin A should be 3 times the dose of vitamin D (calculated in international units). In “Pediatrics” and authoritative guidelines such as “Recommendations for Prevention and Treatment of Micronutrient Deficiencies in Children”, “China National Formulary (Children’s Edition)”, “Prevention and Treatment of Vitamin A Deficiency in Subclinical States”, “Recommendations for Prevention and Treatment of Vitamin D Deficiency Rickets”, all of them give a clear guideline dosage for prevention of Vitamin AD deficiency: newborn babies should be supplemented with Vitamin AD preparations every day from the 15th day of their birth, and infants up to the age of 1 year The recommended dose for infants is vitamin A1500IU, vitamin D500IU, and the recommended dose for young children aged 1-3 years is vitamin A2000IU, vitamin D700IU, in order to meet the nutritional needs of babies of different ages.