The correct understanding of calcium supplementation for infants and children: a. The correct understanding of vitamin D supplementation. Rickets is commonly referred to as “calcium deficiency” because it is characterized by delayed growth and poor bone calcification in children. The key to preventing rickets is to supplement vitamin D. Vitamin D can promote the absorption of calcium in the intestines and facilitate the deposition of calcium to the bones. The effect of vitamin D supplementation can be achieved by taking your child to the sun more often. The vitamin D content in breast milk is low, and if the infant has little time for outdoor activities, breastfeeding alone cannot meet the infant’s need for vitamin D. Therefore, infants should start taking vitamin D supplements from one to two weeks after birth, with 400 international units per day until two years of age; or infants should take 400 to 800 international units per day under the guidance of a doctor from birth; or according to different feeding methods: infants who are exclusively breastfed or mixed-fed should take 400 international units of vitamin D per day; infants who drink fortified vitamin D formula should take 400 international units of vitamin D per day. Infants and toddlers who drink less than 1000 ml of milk per day should also take an additional 400 international units of vitamin D. Vitamin D should be supplemented until adolescence. Second, the correct understanding of calcium supplementation. Normal full-term newborns generally do not need calcium supplements for 6 months after birth. This is because infants within 6 months rely entirely on drinking breast milk or formula to provide nutrition, and both breast milk and formula contain abundant and sufficient calcium. The vast majority of infants and toddlers begin to add complementary foods after 6 months of age, at which point additional supplementation is required if sufficient calcium is not consumed in food. Breast milk contains 25mg of calcium per 100ml, while the equivalent amount in formula can generally contain up to 50mg or more. Although breast milk has the right ratio of calcium to phosphorus, which is more beneficial to the baby’s absorption and utilization, the content is limited; while milk is high in calcium, but due to the low bioavailability, if the amount of milk is less than 600ml per day, you also need to supplement calcium again. Infants should receive 300mg of calcium per day from 0 to 6 months, 400mg per day from 7 to 12 months, 500mg per day from 1 to 3 years, 600mg per day from 4 to 6 years, 700mg per day from 7 to 9 years, and 1300mg per day from 10 to 18 years. If your baby is born with a weak constitution or has frequent diarrhea, he or she should be fortified with a variety of nutrients and the amount of calcium intake should be twice that of a healthy full-term baby. Third, calcium supplementation alone will not have serious consequences such as kidney stones and other calcium deposits, because the excess calcium not absorbed by the body will be excreted with the excretory system. Except in the case of excessive vitamin D supplementation, which can lead to kidney stones due to excessive calcium absorption. Therefore, when supplementing children with vitamin D and calcium, it is important to calculate the recommended intake and preparation content precisely.