Sunshine can be a rarity in this part of the world, so making good use of it matters. The body produces vitamin D when exposed to ultraviolet B (UVB) rays from sunlight. Vitamin D promotes the absorption of calcium and phosphate from food, and is essential to forming bone and teeth. It has also been linked to helping control asthma, preventing high blood pressure, multiple sclerosis and warding off Parkinson's disease.
What deficiency causes
A deficiency in vitamin D leads to a failure of bones to grow, causing rickets in children and osteomalacia in adults. Vitamin D is also believed to play an important role in regulating cell production, which may have an effect on reducing breast, colon and prostate cancers. Lack of vitamin D can also lead to lower lung function and weaker control of an asthma attack. The nutrient plays a role in strengthening nerve cells, which are affected in Parkinson's disease.
Sources
Most vitamin D is made by the body when skin is exposed to sunlight. Some comes from oily fish (tuna and salmon), milk, and fortified cereal. Vitamin D supplements can also be taken. Sunlight is the main source, but exposure also carries a risk of skin cancer, so sunscreen is advised after a few minutes in direct sun. The amount of exposure needed for adequate vitamin D depends on where you live and the time of year. UK winters in particular call for extra sources beyond sunlight. UVB intensity is reduced by clouds, pollution and glass, so sitting next to a window does not generate vitamin D.
A note on sunbeds
Sunbeds emit the same UV rays (UVA and UVB) that penetrate deep into cells and can cause gene damage, triggering skin cancer. Many experts argue that sunbeds should not be used as a tanning method.