Lighting the way to better health: vitamin D

17th July 2010

The Lancet

The public health message is compellingly simple: avoid the sun to prevent melanoma and other forms of skin cancer. Unfortunately, exposure to sunlight is the mainstay of vitamin D synthesis, and vitamin D deficiency causes rickets and osteomalacia, contributes to osteoporosis, and has been associated with many other disorders, including diabetes, cancer, and cardiovascular disease.

Ultraviolet B radiation produces 90% of vitamin D in human beings; only a very small proportion can be obtained through diet. However, at high latitudes, levels of sunlight in winter are often so low that vitamin D insufficiency is common. Avoidance of the sun’s rays by covering up or use of sunscreen can compound this problem, and is thought to have contributed to a recent increase in metabolic bone disease. Cancer Research UK recognises the need to balance skin cancer prevention with generation of adequate vitamin D, but specified that “the skin efficiently produces vitamin D at levels of sun exposure below those that cause sunburn…when it comes to sun exposure, little and often is best”. Australia’s SunSmart guidelines underwent a revision to reflect this balance in 2006—07.

A major concern is that people might seek prolonged sun exposure without protection to boost vitamin D synthesis. Indeed, the American Academy of Dermatology argues that the risks of sun exposure outweigh the benefits, advocating instead for dietary supplementation as a safe source of vitamin D. A report published in the British Journal of Nutrition emphasises that in the UK, a unified approach to vitamin D supplementation is needed to address deficiency in pregnant women and avoid life-threatening complications for their babies.

Despite the simmering debate about sun exposure surrounding vitamin D, the SUNLIGHT consortium’s genome-wide association study, published in The Lancettoday, should add to our understanding of the genetic basis of interindividual variability in the synthesis of vitamin D. These findings could eventually help to identify who is most at risk of vitamin D insufficiency and related diseases. Until such potential applications come to the fore, the message about sun exposure has to be sensibly moderate. Enjoy the summer sun, with caution.

Source : The lancet

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(10)61094-X/fulltext?elsca1=TL-160710&elsca2=email&elsca3=segment

Public advice on suntanning may mean vitamin deficiency risk

Concerns over the link between rising skin cancer rates and exposure to sunshine may have led to overly precautionary advice being given to the public about staying out of the sun at midday, according to a confidential “position statement” by leading health organisations.

The current advice to the public from the leading research charity on skin cancer, Cancer Research UK, states to spend between 11am and 3pm in the shade and to cover the skin with clothing, hats and sunscreen if out.

But a confidential position statement being prepared by the charity in collaboration with other health organisations – and seen by The Independent – acknowledges the changing evidence and emphasises the importance of exposing the skin to the midday sun without any protection in order to maximise production of vitamin D.

Many experts are concerned that past advice designed to protect against skin cancer may have resulted in an increased risk of other illnesses linked to a lack of vitamin D, which the body can only produce when skin in exposed to bright sunlight. New concerns about Britain’s policy on sun exposure led to this review of the evidence about the risks and benefits of staying in the shade and covering up during the sunniest part of the day.

The confidential document, seen by The Independent, says: “The time required to make sufficient vitamin D is typically short and less than the amount of time needed for skin to redden and burn. Regularly going outside for a matter of minutes around the middle of the day without sunscreen should be enough. When it comes to sun exposure, little and often is best. However, people should get to know their own skin to understand how long they can spend outside before risking sunburn under different conditions.”

The wording of the draft document is being seen by come commentators as a tacit admission by Cancer Research UK that it had got it wrong in the past about telling people to avoid the midday sun, to apply sunscreen and to stay in the shade in order to avoid exposure to the cancer-causing rays of the sun.

“Cancer Research UK is working on a new position statement on vitamin D and sunshine which it expects to agree with other health organisations,” said Oliver Gillie, a health writer who has championed the case for vitamin D. “Their new position is expected to break with 20 years of advice to seek the shade and is expected to suggest that people go out in the sun in the middle of the day for at least a few minutes. Several health bodies have agreed to the wording but others are still discussing the details.”

Organisations such as the British Heart Foundation, the Multiple Sclerosis Society, Diabetes UK and the National Osteoporosis Society are discussing what their public position should be on sunshine and vitamin D in the light of several new studies suggesting a link between various illnesses and a chronic lack of the vitamin.

The draft position statement says: “Cancer Research UK’s SunSmart campaign encourages people to enjoy the sun safely and avoid exposures that lead to sunburn. However, for most people, sunlight is also the most important source of vitamin D, which is essential for good bone health.

“It is important to ensure that skin cancer prevention messages are balanced with the need to make enough vitamin D, and reflect the latest scientific evidence.” Sara Hiom, director of health information at the charity, said that the draft consensus statement has not yet been finalised, agreed or released. “It is not our advice to the public and should not be interpreted in that way,” Ms Hiom said.

“Even once we reach a consensus we will not be advising the public to go in the sun in the middle of the day without sunscreen. This is because, for some people – those most likely to be at risk of skin cancer – a few minutes in the middle of the day is enough for them to burn and cause serious and lasting skin damage.

“The very fact that messages around safe sun exposure times cannot be generalised to the population means that our advice needs to be general and is, and will remain, to enjoy the sun safely, spend time in the shade around midday and know your own skin type.”