If, like me, you came of age in the 1980s and 1990s, you probably don’t remember a time when you weren’t warned to stay out of the sun. The message for the past few decades has been that sun exposure = skin cancer, and that if you absolutely have to go out during daylight hours for more than a nanosecond, to please not do so without first donning sunscreen and a full suit of body armor.
It’s true that excessive sun exposure can cause skin damage and increase the risk of skin cancers. But there’s (pun intended) a wrinkle to this. And that is that limiting sun exposure might also increase your risk of getting lots of other diseases, including heart disease and virtually every other known cancer. I’ll discuss some data about this in a moment, but first I want to just share some thoughts about sun exposure in general:
Sun exposure is strongly linked to the two most common types of skin cancer, basal cell cancer and squamous cell cancer. So it’s not a good idea to just go bake in the sun all day. However, these two types of cancer, while very common, are rarely lethal. They are slow growing, rarely metastasize, and are cured in over 99% of cases. By contrast, the type of skin cancer that is much more likely to kill (melanoma) is less firmly linked to sun exposure. (There does appear to be a link between sunburns and melanoma, but whether chronic low-grade sun exposure is a risk factor is more controversial). Hence, avoiding the sun will reduce your risk of developing non-lethal skin cancer, but may not drop your risk of developing the lethal type of skin cancer all that much.
We get most of our vitamin D from sun exposure, and studies have consistently shown that in virtually every disease imaginable, from COVID to cancer to autoimmune disease, low vitamin D levels increase the risk for poor outcomes. (During the COVID pandemic, for example, having a low vitamin D level was a big risk factor for hospitalization and death. By contrast, those with normal vitamin D levels tended to have mild illness). At the same time, many studies using vitamin D supplementation have failed to show a major benefit. Taken together, the implication of these two facts is that either 1) the vitamin D we get from the sun is in some way better for us than the vitamin D we can get from a capsule, or 2) there’s something about sun exposure that is really good for our health, and having a high vitamin D level without taking a supplement is simply a marker for getting enough sun.
Finally, if we take the historic lens, humans spent much of their time outdoors until relatively recently. It’s logical to consider the possibility that being outdoors and getting sun exposure might in fact be a biological necessity, one that we have inadvertently disrupted by moving almost all of our existence inside.
Therefore, it is reasonable to wonder if there might be benefits to getting outdoors and getting at least a little sun exposure each day. And indeed, there are studies to support this idea.
A caveat is important. The studies reviewed by Dr. Weller are epidemiological, and hence could be subject to bias and errors. The most obvious alternative explanation is simply that people who get outside a lot are able to do so because they are already healthier than those who don’t. Also, people are often physically active when outside, and being physically active is protective against many health problems. This paper does not provide definitive proof that being in the sun is good for you.
Nonetheless, in tandem with the points I raise earlier in this post, I think a commonsense conclusion would be that neither excessive UV exposure (tanning beds, sunburns) nor complete avoidance of the sun are best for optimal health, and a commonsense middle of the road approach is best.
For me personally, this means that I try to spend some time outdoors every day in the early morning and in the later afternoon, when sunlight is available but when UV exposure is lowest. Additionally, I try to get outside briefly a few times throughout the day, and when doing so I don’t take any particular sun precautions. By contrast, if I am going to be outside for many hours during the day (e.g. at a beach during the summer), I do use sun protection such as sunscreen, a t- shirt, and a hat.
