Many parents are prone to anxiety about their children's height. In pediatric nutrition clinics, height is consistently listed on the top 3 most concerning issues for parents. Regarding height issues, the most important nutrient for parents is calcium, followed by protein. But the truth is: most children's dietary intake of these two nutrients is often sufficient. Protein intake may even be excessive. But another nutrient closely related to height growth is often overlooked by parents, especially for children over 2 years old. This nutrient is vitamin D. Related studies have shown that vitamin A and D deficiency is more common in preschool children. Let's take a look at a recent study published in the Chinese Journal of Pediatrics. A survey and analysis were conducted on the serum vitamin A and vitamin D levels of 2924 children aged 2-7 in 20 cities in China from September 2018 to September 2019, jointly conducted by 17 children's professional institutions, including the Children's Nutrition Research Center of Chongqing Medical University Affiliated Children's Hospital, the National Clinical Medical Research Center for Children's Health and Diseases, and the Key Laboratory of Children's Developmental Diseases Research of the Ministry of Education. The overall deficiency rates of vitamin A and D were 2.19% and 3.52%, respectively; The overall deficiency rates of vitamin A and D are 29.27% and 22.0%, respectively; 10.50% of children have insufficient levels of both vitamin A and D; The deficiency rates of vitamin A and D in children aged 3-5 and 5-7 are higher than those in children aged 2-3; The deficiency rate of vitamin A and D in children with an annual household income below 60000 yuan is significantly higher than that in children with an annual household income above 60000 yuan; The northwest and southwest regions have the highest rates of vitamin A and vitamin D deficiency between the ages of 2-7, respectively; Continuous supplementation of vitamin A and D for three months can help improve the deficiency of vitamin A. From the above data, it is not difficult to extract a core conclusion: the shortage and deficiency rate of vitamin A and D in preschool children in urban areas of China are relatively common. Especially in economically underdeveloped areas such as the northwest, northeast, and southwest. Vitamin A is more easily obtained from the diet than vitamin D, and animal liver is a very rich source of vitamin A. And in various red, yellow, green vegetables and fruits β- Carotenoids, in the presence of fat, can be converted into vitamin A within our body. Therefore, correcting vitamin A deficiency through diet is relatively not that difficult. Vitamin D is not that easy. There are very few foods that can provide vitamin D, and the content is low. There are only a few common sources: egg yolk, mushrooms (only vitamin D2 from plants, not D3 in the active form), animal liver, and various oily fish (such as sardine, salmon, etc.). But even if we eat these foods regularly, they can only provide about 10% of our body's required vitamin D, and the remaining 90% needs to be synthesized through proper sun exposure on the skin. However, sunbathing well is not an easy task. To have enough sunlight for your skin, you first need to live in an area with sufficient ultraviolet radiation, which is a high level of solar radiation. The typical frontal view is the Qinghai Tibet Plateau, with scorching sun shining in the sky every day. Negative examples are in the Sichuan Chongqing region,