How to take vitamin D supplements? Nowadays, many parents know that their children’s so-called “calcium deficiency” is mainly due to poor calcium absorption caused by vitamin D deficiency, so they will give their children vitamin D supplements, but in clinical practice, we are often asked by parents: When should our children start taking vitamin D supplements and for how long? Is it true that we don’t need to take vitamin D supplements when we have sun exposure? Some of them believe in their next-door neighbors or a program on CCTV a few years ago and think that they don’t need vitamin D supplementation until they have O-shaped legs, X-shaped legs, chicken breasts, and sunken lower ribs and become anxious, when they already have skeletal deformation, which affects their appearance and function. Natural food sources rich in vitamin D are limited, and although UV light exposure to the skin can synthesize vitamin D, the amount is not easily determined, while excessive light exposure may increase the risk of skin cancer. To prevent vitamin D deficiency and rickets, the American Academy of Pediatrics revised its clinical guidelines in November 2008, recommending that all infants (including exclusively breastfed infants), children and adolescents take at least 400 IU of vitamin D daily (Note: IU is the International Unit, the physiologically active mass unit of the vitamin; 1 IU = 0.025 μg of vitamin D3) from the first few days of life. To meet this requirement, the following recommendations should be followed: 1. Infants who are exclusively breastfed or mixed fed (note: infants refer to children under one year of age) should take 400 IU of vitamin D daily from the first days of life; if the infant consumes >1000 ml of vitamin D fortified formula daily when weaned from breast milk, no additional vitamin D supplementation is required. (Note: usually our commercially available formulas are fortified with vitamin D, which will be indicated in the ingredient list) 2. All artificially fed infants and children who consume <1000ml of formula (or milk per day (meaning children over one year of age) need to take a vitamin D supplement of 400 IU per day (Note: referring to vitamin D supplements means vitamin D drops or capsules). 3. Adolescents (referring to children around puberty age 12-18) who cannot consume 400 IU of vitamin D per day from vitamin D fortified milk or vitamin D fortified food need to take additional vitamin D supplements. What is a normal blood vitamin D level? Serum 25-(OH)D levels in infants and children should be ≥50 nmoL/L. (Currently, testing serum 25-(OH)D3 concentrations is the gold standard for diagnosing the presence of vitamin D deficiency.) 25 to 50 nmol/L is a decrease, and less than 25 nmol/L is a deficiency. What foods are rich in calcium? The main sources of dietary supply of calcium are: Dairy (milk, yogurt, cheese) Soy products (marinated tofu, plastered tofu, dried tofu, etc.) Dark green leafy vegetables (chard, kale, etc.) Sesame seed paste, nuts, small fish with bones and shrimp and shellfish, etc. If your usual food is rich in calcium, no additional calcium supplementation is needed.