Why Some Sun Exposure Will Protect You from Deadly Skin Cancer

How does sun exposure relate to skin cancer risk? The simplistic, popular story is that sunlight exposure has a linear relationship with cancer, similar to how we view smoking. None is safest and each additional minute in the sun will increase our chance of getting cancer. Many people (maybe most) therefore live in a world with danger lurking beyond every shadow, umbrella, overhang, and roof. You let your kid go outside without a layer of sunblock so thick he looks like he’s been smashed in the face with a whip cream pie, and you’re a terrible mother. And don’t even think about the beach unless you’re wearing a burqa. It’s even got a scary name: ultraviolet radiation. Radiation! Isn’t that the stuff inside nucular bombs? The relationship between sun exposure and skin cancer is far more complex than you’ve been led to believe. While clearly too much sun is a causative factor in skin cancer of all types, it’s not clear what “too much” means. Is there a U-shaped curve where none is bad, some is good, and too much is bad again? What about other factors, like skin color, hair color, propensity to tan versus propensity to burn, and time of day? We already know that living in areas that get more UV radiation seems to be protective against other types of cancers, like prostate cancer, lung cancer, colorectal cancer, leukemia, bladder cancer, pancreatic cancer, breast cancer, and lymphoid cancers (I probably could have kept going, but my fingers were getting tired). Okay, but what about cutaneous malignant melanoma (CMM)? It’s not the most common kind of skin cancer, but it’s by far the deadliest. Is it worth the tradeoff if we increase our risk of CMM? When we combine the estimated number of annual diagnoses for the cancers I just mentioned in the US, we get a staggering figure: 1,071,000. What about melanoma? 76,100. Incredible, huh? Getting adequate amounts of ultraviolet radiation (scary!) may very well reduce the incidence of cancers that are afflicting over a million Americans each year. Even if the dermatologists and sun alarmists are right and melanoma risk increases linearly with sun exposure and ultraviolet availability, the protection we get against so many other cancers (and the tan, and the sublime feeling of the sun on your skin) might make the tradeoff worth it. That’s clearly, objectively true, at least on the population level. Melanoma just isn’t as large an absolute threat as the totality of other cancers. Every reader of this blog is likely aware of the importance of vitamin D in the body. The vital pro-hormone, which also comes in supplement form, helps regulate skeletal, cardiovascular, immune, hormonal, and dental health. A deficiency can cause rickets, osteoporosis, muscle wasting, and various hormonal deficiencies. Low levels are linked to heart disease, autoimmune diseases, all cause mortality, and many cancers. These are the systemic effects that get the most attention, but what if the dermatologists and sun alarmists were wrong, or at least a little misguided in their binary opposition to any and all sun? On the surface, it seems counterintuitive that an act that … Continue reading Why Some Sun Exposure Will Protect You from Deadly Skin Cancer