Vitamin D plays a crucial role in various aspects of human health, making it an essential nutrient. It is stored in the body, dissolves in fat, and is present in foods such as fatty fish, mushrooms, and fortified dairy products. The deficiency of Vitamin D is a widespread issue in the health of the public that affects individuals of all ages, particularly those in low- and middle-income nations. It is believed to affect more than one billion individuals globally. Pregnant and nursing women, elderly persons, people with a dark complexion, and those who live in places with little sun exposure are the population categories most at risk for deficiency. The World Health Organization advises people and groups who can be Vitamin D insufficient to make sure to enhance their levels of the vitamin through increased sun exposure, food sources, or supplementation. Depending on personal characteristics including age, skin type, and health state, different amounts of supplements may be required. Additionally, since consuming too much Vitamin D can result in toxicity and other health issues, it’s crucial to stick to suggested dosages and not go over the daily recommended amount. Vitamin D is a crucial mineral for human health, especially in infancy. It helps control the amounts of calcium and phosphorus and is crucial for maintaining the formation and progress of bones and teeth. Although breast milk provides neonates with a natural source of nourishment, Vitamin D daily requirements are not fulfilled. This has raised worries about Vitamin D insufficiency in breastfed infants, which can have detrimental effects on their health. This chapter will examine the importance of Vitamin D for neonates, as well as its sources, reasons for deficiency, and strategies for supplying breastfed infants with enough amounts of this vital mineral. The most recent research on Vitamin D in young children will also be covered, along with how it impacts health outcomes and what that implies for clinical practice and overall public health.