Vitamin D is important in helping the body absorb and use calcium from food and supplements. It aids in bone and tooth formation and supports muscle and nerve function, and studies have shown that vitamin D helps to prevent osteoporosis. Nutritionists categorize vitamins by the materials that a vitamin will dissolve in. There are two categories: water-soluble and fat-soluble vitamins. Fat-soluble vitamins are vitamins A, D, E and K which stored in the fat tissues of the body for a few days to up to six months. If you get too much of a fat-soluble vitamin, it can be stored in your liver and may sometimes cause health problems. Vitamin D is a fat-soluble vitamin. Some people take mega-doses of fat-soluble vitamins, which can lead to toxicity. Eating a normal diet of foods rich in these vitamins won't cause a problem. Remember, you only need small amounts of any vitamin.

Vitamin D promotes absorption and use of calcium and phosphate for healthy bones and teeth.

Vitamin D is found in milk (fortified), cheese, whole eggs, liver, tuna, fish-liver oils, salmon, and fortified margarine. The skin can synthesize vitamin D if exposed to enough sunlight on a regular basis.