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.


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.


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.