Vitamin D is so important, the American Academy of Pediatrics recommends using a supplement to help meet daily requirements of 400 IU. Immune Health. Proper levels of Vitamin D can help to maintain a healthy functioning immune system in your child. Bone Health. Vitamin D, along with a healthy diet and exercise, can help the body's natural production of cells, which are found in healthy joints and is a key nutrient for helping your child maintain proper bone health. Respiratory Health. Vitamin D can help support a healthy immune and respiratory system. Heart Health. Studies on the sunshine vitamin support Vitamin D's role in a healthy heart, both in children, as they develop, and in adults.