Vitamin D is a hormone and a nutrient. It is made by our bodies. It is also taken as a nutrient from foods rich in vitamin D. Cereals, fatty fish, sunlight, and vitamin supplements are good sources of vitamin D.

Health benefits

The amount of vitamin D in bodies is linked to the health of bones. Calcium makes bones stronger. Without vitamin D, the human body is incapable of using calcium. A deficiency of this vitamin can lead to the weakening of bones – osteoporosis (rickets).

Rickets is not uncommon in America where a large number of people (nearly one-third of the population according to a Center for Disease Control and Prevention study) are not getting sufficient amounts of vitamin D.

Besides rickets, researchers are exploring the links between vitamin D and muscle strength, heart diseases, cancer, immune system and longevity.

There is tentative evidence that vitamin D helps people with a heart disease or cancer. A few studies have shown that vitamin D improves muscle strength and makes the immune system stronger.

Sources

There are three sources of vitamin D – (a) sunlight, (b) food, and (c) supplements. Body manufactures vitamin D when sunlight falls on the skin. Saltwater fish, egg yolks, milk, and cereals are vitamin D rich foods. Supplements are used when diet and sunlight fail to provide the required amount of vitamin D.

Side-effects

There is still no agreement on how much vitamin is required to function normally everyday. A 2010 report of the Institute of Medicine recommends 600 IU (international units) per day. The report puts the upper limit of vitamin D, which body can take without adverse side-effects, at 4,000 IU.

Consumption of larger (50,000 IU) amounts of vitamin D for a long period (several months) can lead to hypervitaminosis D. This is a rare but serious condition which can be fatal. Fortunately it so rare, that it is even uncommon among people who take regular vitamin supplements.