Vitamin D is known to play a vital role in metabolism of calcium, which is needed for strong bones.
And last week a new study revealed it may help stave off Alzheimer’s Disease. Research on English adults aged 65 and over showed that as their Vitamin D levels decreased, mental impairment increased.
Deficiency can also cause osteomalacia – a weakening of the bones that may cause rheumatism or chronic backache – and children can develop rickets, a condition in which the bones do not develop properly.
Research has shown that without it we are more prone to everyday infections such as colds and flu, and also more worrying ones, such as tuberculosis (TB).
But perhaps more surprisingly, there is also evidence that Vitamin D could protect us from cancer.
Recent studies have found those countries with the most annual sunshine have the fewest cases of colon, prostate and breast cancer (although exactly what role Vitamin D plays isn’t totally clear in these instances).
In one case, sunshine exposure was linked to a 40 per cent reduced risk of prostate cancer.
And research published in the American Journal Of Clinical Nutrition in 2007 reported a possible reduction of breast cancer in women who took Vitamin D tablets.
The idea that Vitamin D is essential for good health is not new; nor is the connection to sunlight.
In Britain just after the turn of the 19th Century, children in cities had less exposure to sunlight and became crippled by rickets. It was also discovered that TB – which was commonplace – could be treated with cod liver oil, another good source of Vitamin D, and sunlamps – early versions of sunbeds that provide artificial UV light similar to sunlight.
But in more recent years, antibiotic-resistant strains of diseases such as TB are emerging, proving that medicine may no longer be enough.
Combine the anti-sun skin cancer message and the trend for young people to play indoors on computer games rather than running around outside and there is the potential for a health crisis.
In 2009 we are simply not getting enough sunlight to make the Vitamin D we need to stay healthy.
Dietary sources of Vitamin D include oily fish, liver, eggs and fortified foods such as cereals, margarine and powdered milk. There are supplements, such as cod liver oil, but it’s almost impossible to get sufficient Vitamin D from diet alone. A person would have to drink ten tall glasses of Vitamin D-fortified milk each day just to get the minimum levels.
There are several pills available in low doses (the European Recommended Daily Allowance is 5mcg). But, despite being a doctor, I am not a great fan of pill-taking, especially as there is controversy over what is a ‘safe’ level of the vitamin.
In the early Fifties, use of Vitamin D supplements in food caused infants to die of heart and kidney failure.
But, by contrast, it is impossible to overdose through sunlight exposure. The skin automatically switches to manufacturing pigment (resulting in a tan) when it has made enough Vitamin D.
Sunshine really is the best source.
This doesn’t mean you should throw yourself at a beach once a year and let yourself burn. The skin cancer message is right. Melanomas – tumours on the skin – are found on people who have burnt in the sun, particularly when young.
Best estimates from a recent World Health Organisation report are that, on a sunny day, a fair skinned person will achieve maximum Vitamin D production from exposing face and forearms to midday sunlight for five to ten minutes, up to three times a week. Short exposure gives the benefit and long exposure causes harm.
Of course, in this country, sun can be hard to come by, especially during the winter. It’s during these times that many of us may benefit from the UV lamps used in sunbeds. Because the whole body is usually exposed, a single five to ten-minute session once every six weeks should be sufficient.
Those with darker skin may need up to eight times as much exposure as someone of a Caucasian background because their skin is more resistant to UV rays.
The danger with sunbeds comes if they are used by children. The risk of melanoma increases for those who start using sunbeds under the age of 18.