woman sun sunglasses Skin cancer is the most common type of cancer diagnosed in the United States. Since the main cause of skin cancer is ultraviolet (UV) rays from the sun, people are becoming more conscious of the harmful effects of sun exposure.

Since the 1980s, Americans have transitioned from slathering on baby oil and baking in the sun to covering themselves with high SPF (sun protection factor) sunscreens and avoiding midday sun. While there are still many sun worshipers out there, most people are now aware of the risks of sun exposure.

The National Cancer Institute recommends avoiding the sun between 11 am and 3 pm whenever possible, wearing protective clothing (e.g., sun hats, long sleeves), and using sunscreen with an SPF of at least 15 or 30. Similarly, the American Academy of Dermatology recommends staying out of the sun between 10 am and 4 pm, wearing protective clothing, and applying broad-spectrum sunscreen (the kind that protects against both UVA and UVB rays) with an SPF of 15 or higher.

The sun, however, does have certain health benefits. It can enhance your mood, protect against certain diseases, and boost your level of vitamin D. And recent studies have suggested that sun exposure may help prevent certain types of cancer. So should sun protection guidelines change? Should people work to balance their level of sun exposure—finding a common ground between getting enough, but not too much, rather than avoiding the sun altogether?

Sunlight and Skin Cancer

Each year, about a million Americans are diagnosed with skin cancer. Of these, an estimated 54,000 (5%) have melanoma, the most deadly form of skin cancer. While non-melanoma skin cancers (basal and squamous cell carcinomas) rarely spread, melanoma can spread to other parts of the body.

Ultraviolet rays from the sun are the main cause of skin cancer. Scientists have discovered that people who live in climates closer to the sun are more likely to get skin cancer. To demonstrate, skin cancer is more common in people living in Texas than in Minnesota, and the highest rates of skin cancer are found in South Africa and Australia.

Fortunately, for the most part, skin cancer can be prevented with safe and consistent sun protection. But since the damaging effects of the sun start early in life, it is important to begin practicing sun protection in childhood.

The Benefits of the Sun

The warmth and light generated by the sun can enhance your feeling of well-being and stimulate blood circulation. Sun exposure can also help prevent Seasonal Affective Disorder (SAD) , a condition that results in bouts of depression in the late fall and winter, when exposure to sunlight is reduced.

Furthermore, the sun triggers your skin to synthesize vitamin D. While vitamin D is found in foods, including fortified milk and cereals, cod liver oil, and certain fish, many people don’t get enough of it from foods, so the sun provides most people with their vitamin D requirement. The catch is that sunscreen blocks the production of vitamin D.

With 10-15 minutes of sun exposure to the face, arms, hands, or back without sunscreen at least two times per week, most people can get an adequate level of vitamin D. However, people who live in northern or cloudy climates during certain times of the year may not be able to synthesize enough vitamin D from the sun.

Adequate levels of vitamin D prevent rickets in children and osteomalacia in adults (both are diseases that weaken bones). In addition, vitamin D may help maintain a healthy immune system, promote normal cell growth, and prevent osteoporosis .

Research on Sun Exposure and Cancer

Interestingly, a number of studies have linked sun exposure to a reduced risk of cancer.

An article published in Preventive Medicine in November 1990 found that the risk of fatal breast cancer in the United States was higher in the northeast and lower in the south and southwest, indicating that sunlight exposure may protect against death from breast cancer . And in 1999, the National Institutes of Health published a report that showed that people living in northern states are more likely to die from a number of cancers, compared to those living in southern states.

More recently, two studies in the February 2, 2005 issue of the Journal of the National Cancer Institute provided striking evidence of the protective effect of sunlight against cancer. The first study looked at the level of sun damage to the skin, and history of sunscreen use, severe sunburn, and intermittent sun exposure in 528 people diagnosed with early-stage melanoma, a type of skin cancer. Other than sunscreen use, all measures of sun exposure were associated with a decreased risk of death from melanoma.

The second study compared 3,700 people with malignant lymphomas to 3,200 people without cancer. The researchers found that high frequencies of sunbathing and sunburns before age 21 were associated with a significant 30% to 40% reduction in the risk of developing non-Hodgkin’s lymphoma .

Two more studies, one in the June 15, 2005 issue of Cancer Research and one in the April 2005 issue of Mutation Research , indicated that increased levels of sun exposure may be associated with a lower risk of advanced prostate cancer .

Why might sun exposure be protective against cancer? Researchers don’t yet know for sure, but some propose that increased levels of vitamin D associated with sun exposure may have anti-cancer effects. In laboratory studies, vitamin D has been shown to inhibit cancer cell growth and induce death of cancer cells.

What This Means to You

While the evidence continues to build that sun exposure may be protective against cancer, these studies are far from conclusive. They cannot say why people who are exposed to more sun are less likely to develop or die from cancer, so it is too early to go back to the days of baking in the sun.

Until there is enough evidence to make solid recommendations, the best advice is to use your own good judgment. Weigh your own personal risks versus benefits of moderate sun exposure and decide on a safe amount of sun for you.

While anyone can get skin cancer, people with fair skin, light-colored eyes, blonde or red hair, a tendency to burn or freckle, and a family or personal history of skin cancer are at higher risk. For most people, spending 10-15 minutes in the sun two or three times per week before applying sunscreen is a safe, healthful way to get an adequate amount of vitamin D.