Vitamin D is a very important substance that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. Its deficiency is known to cause several bone diseases. Vitamin D is produced naturally by the skin from cholesterol with the help of UV light.

However, UV light is also responsible for an increased risk of skin cancer. Ultraviolet light is sufficiently energetic that it can produce mutations in the DNA of the skin cells. When these mutations are not corrected by the organism's enzymes and the cells multiply, skin cancer develops.

In case of people over 50 the skin's ability to convert cholesterol into vitamin D decreases as well as their enzymes ability to correct mutations. Thus, the beneficial effects of UV light decrease and their negative effect increase. It is recommended they rather use vitamin D pill supplements than sunbathing.

The people who are most likely to have a vitamin D deficiency are the ones with dark skin because they are the most adapted to repeal the damaging effects of UV. On the other hand, young light-skinned people face the greatest skin cancer risk from UV light - and they are among the least likely to have vitamin D deficiency.

"You can get all the good stuff with a vitamin pill - you do not have to put yourself at increased risk of skin cancer and photo-ageing," said Dr. Barbara A. Gilchrest, of Boston University School of Medicine and co-author of a review on vitamin D requirements and UV radiation. "Sunbathing to get more vitamin D is like taking up smoking to lose weight."

Newborn infants who are exclusively breastfed usually require vitamin D supplements because breast milk does not contain significant levels of the vitamin and it is not recommended for them to be exposed to sunlight in the levels required to produce a sufficient amount of vitamin D.

Dr Gilchrest advised people who were worried about not getting enough vitamin D to take a vitamin pill - or two. "Vitamin D is very safe to take in the form of oral supplements," she said.

There are few food that naturally contain significant amounts of vitamin D. These include fatty fish such as salmon, tuna or sardines, eggs, and beef liver. However, to make a comparison, one egg for example has 8 times less vitamin D than a single pill.

Photo Credit: STEVE HORRELL/SPL