Free full text: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5129901/
Dermatoendocrinol. 2016 Jan-Dec; 8(1): e1248325.
Published online 2016 Oct 19. doi: 10.1080/19381980.2016.1248325
The risks and benefits of sun exposure 2016
David G. Hoel, Marianne Berwick, Frank R. de Gruijl, and Michael F. Holick
Public health authorities in the United States are recommending that men, women and children reduce their exposure to sunlight, based on concerns that this exposure will promote skin cancer. On the other hand, data show that increasing numbers of Americans suffer from vitamin D deficiencies and serious health problems caused by insufficient sun exposure. The body of science concerning the benefits of moderate sun exposure is growing rapidly, and is causing a different perception of sun/UV as it relates to human health. Melanoma and its relationship to sun exposure and sunburn is not adequately addressed in most of the scientific literature. Reports of favorable health outcomes related to adequate serum 25(OH)D concentration or vitamin D supplementation have been inappropriately merged, so that benefits of sun exposure other than production of vitamin D are not adequately described. This review of recent studies and their analyses consider the risks and benefits of sun exposure which indicate that insufficient sun exposure is an emerging public health problem. This review considers the studies that have shown a wide range health benefits from sun/UV exposure. These benefits include among others various types of cancer, cardiovascular disease, Alzheimer disease/dementia, myopia and macular degeneration, diabetes and multiple sclerosis. The message of sun avoidance must be changed to acceptance of non-burning sun exposure sufficient to achieve serum 25(OH)D concentration of 30 ng/mL or higher in the sunny season and the general benefits of UV exposure beyond those of vitamin D.
KEYWORDS: cancer, cardiovascular disease, melanoma, ultraviolet radiation, vitamin D, 25-hydroxyvitamin D
Quotes from the full text:
The incidence of melanoma in the United States has increased dramatically from 1 per 100,000 people per year in 1935 to 23 per 100,000 per year in 2012. (...) While sunburns have been associated with a doubling of melanoma risk, chronic non-burning sun exposure and outdoor occupations have been associated with reduced risk of melanoma. Indoor occupations such as professional, managerial, clerical, sales and service workers grew from 25% to 75% of total employment between 1910 and 2000. 25% of Americans lived on farms in 1930 whereas only 2% do so today. Indoor attractions such as air conditioning, television, computers and the internet probably have led to Americans spending more of their leisure time indoors, the prevalence of sunburns is high and has been increasing, and serum 25(OH)D levels of the American public, a likely marker for sun exposure, are low and have been declining. A more plausible explanation for the rise in melanoma incidence since 1935 may be the continually-increasing insufficient non-burning sun exposure and related increasing vitamin D deficiency/insufficiency, and the increasing sunburn prevalence experienced by the American public over the same time period. Furthermore, epidemiological studies do not indicate any difference in melanoma risk based on the age at which UVR exposure occurs. Sunburns appear to be equally risky at any age. The public health messages of the past 50 y to avoid sun exposure and to use chemical sunscreens may have contributed to the rise in melanoma incidence.
We can find no consistent evidence that use of chemical sunscreens reduces the risk of melanoma.
Sunscreens do, however, reduce acclimatization to UVR and vitamin D production in the skin. Since public health authorities recommend liberal use of sunscreens for good health, the labeling of sunscreens should contain a statement about the possibility of vitamin D deficiency that may result from excessive use of sunscreens. Labeling should also state that sunscreens have not been shown to be effective in reducing the risk of melanoma.
Sunscreens are intended to prevent sunburn when used in thickness and frequency recommended by manufacturers or used in setting SPFs. However, studies have shown that the incidence of sunburn is higher or the same in people who almost always use sunscreens compared with those who rarely use sunscreens.