The public health policies regarding solar UV exposure and vitamin D have swung back and forth like a pendulum. In the 1920s and 1930s, public health policies supported exposure to the sun as a means to reduce the burden of disease. This changed in the 1970s and 1980s due to concerns regarding the risk of skin cancer, and therefore public health policies turned against UV exposure.
With all of the conflicting information that is out there, how can we make sense of this in order to make more informed decisions about our health and reducing the risk of skin cancer? What I’ve found in my own research is that sun exposure and skin cancer risk is a complex subject. There are many factors involved, including your skin type, history of sunburn, tanning ability, vitamin D status, anti-oxidant levels, fatty acids and many other host factors individual to each person. Lets take a closer look.
Melanoma is the most serious form of skin cancer and accounts for approximately three-quarters of all skin cancer deaths. Over the last few decades, the incidence and mortality rates of melanoma have been increasing worldwide. Sun exposure is recognised as one of the most important environmental risk factors for malignant melanoma and research shows that, on a molecular level, the sun’s ultraviolet (UV) light damages the skin’s cellular DNA, creating genetic mutations that can lead to skin cancer.(1) There are also other theories as to why we are seeing an increase in the rates of melanoma, however. Some say that the use of sun cream, which blocks UVB but allows us to stay in the sun for longer, is the culprit. Others say that a low vitamin D status as a result of not getting enough sun exposure is the main reason. Who is right? Let’s take a closer look.
Behaviours that increase sun exposure have been suggested to be major contributors to the rising incidence of skin cancer. As a result, topical sunscreen lotions are promoted as one of the key strategies to help prevent excessive sun exposure. There is conflicting research here. Some research shows that it can reduce the risk of melanoma, while other studies show that the use of sunscreen is associated with an increased melanoma risk! In conducting my own research, I came across several studies that systematically evaluated the data from studies published between 1966 and 2003 using rigorous meta-analytic techniques. There was no evidence to indicate that sunscreen increased melanoma risk.
Indeed, research published in 2011 shows that regular sunscreen users reduced their incidence of melanoma by 50–73%. In this randomised, follow-up trial, 1,621 Australians (aged between 25 and 75 years) were randomly assigned to daily or discretionary sunscreen application to the head and arms from 1992 until 1996. The participants were observed with questionnaires, through pathology laboratories and the cancer registry until 2006 to ascertain primary melanoma occurrence. The researchers concluded that melanoma may be preventable by regular sunscreen use in adults.(2)
It looks that there is a good body of evidence to suggest that there is value to using topical sunscreen to protect our skin against excessive sun exposure. However, it is worth noting that UVB is the chief culprit behind sunburn, while UVA rays, which penetrate the skin more deeply, are associated with aging effects of skin such as wrinkling. UVA also exacerbates the carcinogenic effects of UVB rays and increasingly are being seen as a cause of skin cancer on their own. Most sunscreens, with a sun protection factor (SPF) of 15 or higher, do a good job of protecting against UVB.
There has been some controversy, however, over whether the use of sunscreen leads to vitamin D deficiency. High SPF sunscreens are designed to filter out most of the sun’s UVB radiation, and it is the UVB wavelengths that trigger vitamin D production in the skin. Nonetheless, clinical studies have not found that everyday use of sunscreen leads to vitamin D deficiency and some have shown that people who use sunscreen daily can maintain their vitamin D levels.(3,4) This could be explained by the fact that no matter how much sunscreen you put on, there will always be some UVB rays that penetrate the skin. For example, an SPF 15 sunscreen filters out 93% of UVB rays and an SPF 30 filters out 97%.
There is also a school of thought that suggests that skin cancer risk is not increased by exposure to the sun but by low levels of vitamin D that results from a lack of sunshine. It is very true that we can obtain a significant amount of vitamin D from the sun, but how much vitamin D you can get from the sun depends on where you live and how much sunshine you get. Here in the UK we get variable amounts of sunshine interspersed with a lot of cloudy days! During the winter months, we might not see a whole lot of sunshine.
In Europe, there is a significant positive correlation between Vitamin D levels in the form of 25(OH)D concentration and latitude.(5) The latitude determines the available sunlight exposure, which affects 25(OH)D concentration. A study published in 2009 showed that in northern latitude locations, in particular, up to 41% of the population may have levels of less than 20 ng/ml during the winter.(6)
Even if you live in a very sunny place, we need to balance the health benefits of sun exposure with the risks of skin cancer. Over the years, the confusion about the ideal levels of sunlight has increased, with different advice being issued by various organisations. In 2010, a group of seven British health organisations issued a ‘consensus statement’ to provide some guidance on sun exposure and vitamin D. This brings together the latest evidence on vitamin D and provides some clarity on what has been a controversial issue. The consensus is that short and frequent spells in the summer sun, several times a week, can increase your vitamin D levels and benefit your health. More specifically, going outside in the sun for 10 to 15 minutes, several times a week, is optimum for increasing vitamin D levels and represents a safe balance between adequate vitamin D levels and any risk of skin cancer.
In the next article, we'll take a look at the biology of sunburn and whether diet and nutritional supplements can decrease the impact of too much sun exposure.
1. UV Damage and DNA Repair in Malignant Melanoma and Nonmelanoma Skin Cancer. In: Sunlight, Vitamin D and Skin Cancer. New York, NY: Springer New York; 2008:162-178. doi:10.1007/978-0-387-77574-6_13.
2. Reduced melanoma after regular sunscreen use: randomized trial follow-up. J Clin Oncol. 2011;29(3):257-263. doi:10.1200/JCO.2010.28.7078.
3. The Effect of Regular Sunscreen Use on Vitamin D Levels in an Australian Population. Arch Dermatol. 1995;131(4):415. doi:10.1001/archderm.1995.01690160043006.
4. Clinically prescribed sunscreen (sun protection factor 15) does not decrease serum vitamin D concentration sufficiently either to induce changes in parathyroid function or in metabolic markers. Br J Dermatol. 1998;139(3):422-427. doi:10.1046/j.1365-2133.1998.02405.x.
5. Differences in vitamin D status between countries in young adults and the elderly. Am J Med. 1992;93(1):69-77. doi:10.1016/0002-9343(92)90682-2.
6. Cyclic Changes of Vitamin D and PTH are Primarily Regulated by Solar Radiation: 5-Year Analysis of a German (50° N) Population. Horm Metab Res. 2009;41(5):402-407. doi:10.1055/s-0028-1128131.
Sports & fitness nutritionist, researcher and author on a mission to improve the human condition. Focusing on evidence-based and outcome-based nutrition, training, mindset & environment