The public health message is : avoid the sun to prevent melanoma and other forms of skin cancer. But exposure to sunlight is important for vitamin D synthesis, and vitamin D deficiency causes rickets and osteomalacia, contributes to osteoporosis.
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.
Leader Lightening the way to better health : vitamin D Lancet vol 376 p 142
Brit J Nutr 2010 ; DO1; 1017/SOOO7114510002436
- Martin Eastwood