Vitamin A is the general name for substances that include retinol, retinal and carotenoids. Vitamin A is key for good vision, and may help maintain a healthy immune system and cell growth. Vitamin D, the “sunshine vitamin”, is produced in the skin in response to sunlight exposure. It has several important functions. Perhaps the most vital are regulating the absorption of calcium and phosphorus, and facilitating normal immune system function. Getting a sufficient amount of vitamin D is important for normal growth and development of bones and teeth, as well as, improved resistance against certain diseases. Not getting enough vitamin D, promotes the development of bone abnormalities such as soft or fragile bones.