Mainly, vitamin D deficiency in the body leads to malfunction of calcium and phosphorus metabolism, and calcium salts cannot be properly deposited in the growing part of the bones, causing abnormalities in the bones and the nervous system. Vitamin D deficiency rickets has been studied as both a nutritional and metabolic disease, which can affect the healthy growth of infants and children. The main manifestations: The onset of the disease starts at the age of 2-3 months, with the highest incidence within one year of age, and the incidence is significantly higher in winter and spring than in summer and autumn. After winter, irritability, night terrors, night cries, restlessness, excessive sweating (mostly unrelated to the season) with no obvious cause appear, and occipital baldness ensues from frequent rubbing of the occipital area due to the stimulation of sweat. Early onset of the head may show enlarged fontanelle, late closure of fontanelle, and delayed teething. The heavier children can also present ping-pong-like softening of the skull, rib beads on the chest, chicken chest, and “O” or “X” shaped bone changes in the lower limbs before and after learning to walk. Preventive measures: 1, advocate breastfeeding, timely addition of complementary foods to ensure that the child’s needs for various nutrients. 2. Two weeks after birth, newborns should start taking cod liver oil orally every day under the guidance of a pediatrician. 3.For infants and toddlers with rapid growth and development, parents should not neglect to supplement adequate amount of vitamin D and calcium. 4.Promote outdoor activities and proper sunshine. Sun exposure should be comfortable and not damage the skin. Daily outdoor activities should be more than one hour. In summer, when the sun is not strong in the morning and evening to go outdoors, pay proper attention to ultraviolet protection, avoid exposure to the sun, can be in the shade of the shade, winter should also pay attention to outdoor activities, in the indoor window should be open to the sun. 5, eat more calcium-rich food, such as dairy products, fish, shrimp, seafood and soy products.