Do white British children and adolescents get enough sunlight?

Fear of skin cancer, prompted by campaigns such as “SunSmart” (www.sunsmart.org.uk/) in the United Kingdom, may have led to children spending less time exposed to sunlight, reducing opportunities for the production of vitamin D in the skin and resulting in a consequent detriment to bone health.1 Furthermore, recent evidence shows that sunlight exposure and the resulting synthesis of vitamin D might reduce the risk of certain cancers2 and, perhaps, of other diseases such as multiple sclerosis.3 In response, there have been calls for current skin cancer awareness campaigns in the UK to be abandoned.4 Are such calls justified?

Adequate sun exposure is not easily defined,1 but one of the leading proponents of the beneficial effects of sun exposure has indicated that exposing the face, hands and arms two to three times a week to a third to a half of the exposure necessary to result in a just perceptible reddening of white skin (the so called minimal erythema dose, MED) in the spring, summer, and autumn is more than adequate to satisfy the body's requirement for vitamin D throughout the year.5 In other words, receiving a weekly dose of around 1 MED to these sites should be sufficient to prevent vitamin D insufficiency. If only the face and hands are normally exposed, then a weekly dose of about 2 MED would be required.

In 1994 we measured the sun exposure of 180 children and adolescents in three regions of England during the spring and summer and found that 98.5% and 91% of children and adolescents, respectively, exceeded a weekly dose of 1 MED.6 Adolescents, however, and especially teenage boys, generally expose only their hands and face when outside: the prevalence of weekly doses that exceeded 2 MED in this age group was only 58%. The median time spent outdoors each day by adolescents during those periods when the weekly dose was less than 2 MED was 1.6 hours, rising to 2.5 hours when the weekly dose exceeded 2 MED.

A popular perception is that being outdoors for 5-10 minutes, two or three times a week, in the summer is sufficient for effective vitamin D production. The reason why one to two hours outdoors each day was insufficient in many cases to result in a cumulative weekly dose of 2 MED, even though in the summer this dose could be achieved by lying in unshaded sunshine for about half an hour around noon, is that people are generally upright, the sky is often cloudy in the UK and buildings and trees often obscure direct sunlight and part of the sky. All these factors serve to reduce the intensity of sunlight on exposed skin thus necessitating the need for prolonged exposure to acquire sufficient dose. That the exposure to sunlight in many adolescents may be insufficient in the spring and summer would certainly account for the observations that the wintertime vitamin D status of almost all teenage girls living in northern Europe is insufficient.7 The association between low vitamin D levels in young people and the subsequent risk of diseases such as osteoporosis or cancer is not clear, however, so the wider implications of this are uncertain.3 7

Such evidence that many adolescents are not sufficiently exposed to the sun is not enough to justify abandoning current awareness campaigns about skin cancer, which are aimed primarily at avoiding excessive exposure. This is especially true for children and adolescents, for whom exposure to high levels of sunlight strongly determines subsequently increased risk of melanoma.8 This is a disease whose incidence is predicted to continue rising in the UK for at least another 30 years, even if current intervention strategies eventually translate into a downturn in incidence.9

Furthermore, campaigns such as SunSmart are intended to advise people primarily during recreational exposure for extended periods in strong sunshine when measures to protect the skin, even if they are used, will not be perfect and will still allow the synthesis of vitamin D.10 So such campaigns should not be abandoned, and British children and adolescents need not deliberately spend extended periods in strong sunshine. Rather, those whose lives are spent almost entirely indoors, in the shade, or in vehicles should take the opportunity during casual everyday activities to walk on the sunny side of the street and, when possible, to avoid taking the car.