Sunscreen and childhood obesity

It’s late. Really late. But this post wouldn’t let me sleep until it was written. I hope any incoherence, bad grammar or spelling mistakes will be forgiven on this basis.

I’m in Moose Jaw to participate in the “Scotland Meets Saskatchewan” that Dean Shareski has organized. Earlier this evening, I sat down with Dean, Ewan McIntosh, Kyle Lichtenwald, John Evans and Cindy Seibel for a terrific conversation about education, technology, creativity and helium balloons. I could write about that, but I’m not going to.

As I was driving here from North Battleford this afternoon, I listened to the audiobook version of Linked. It is a fascinating read (listen?) that describes the importance of networks in society, physics, biology, chemistry and other areas. It would seem there is a common mathematical model that is found in some aspects of these diverse areas. I could write about that, but I’m not going to.

A little while ago I had a twit-versation about politics and media with Alec Couros, Doug Symington and Corrie Bergeron. There were some interesting ideas in there and I could write about that, but … well, you can probably guess.

There is something that’s been on my mind lately that I’ve been wanting to write about. I think that sunscreen (and insect repellant, in areas where that is also required) may be a leading cause of childhood obesity, and here’s my justification for that apparently stupid assertion. When I was a child, lo these many years ago, there was a lower incidence of childhood obesity. There were fat kids (as we called them in those blissfully politically incorrect times), just not as many of them. The increase in the proportion of fat kids in the childhood population has been explained by things like too much television watching. Not likely – my friends and I used to hibernate through the winters, lulled into a somnolent state by the comfortable blue glow of the television, punctuated only by short, intense periods of activity like sledding or skating. During warmer months, we were either at school, riding bikes, at the playground or in a yard. I think that kids today (geez do I sound old when I say that) don’t spend as much time outside during the day but not because of television. It’s partly because of sunscreen. When I was a kid (again, I am sounding old – sigh), the day started with getting dressed, breakfast and then quickly out the door with the expectation that we would return only for meals, medical care or bedtime. We no longer hurry our kids quickly out the door. We also no longer expect our children to be outside all day, but that’s a subject to be left for another time.

Before children are permitted to leave the house, they must now be subjected to the ritual of sunscreening (and general protection from the harmful rays of the day star). This involves application of lotion to all exposed or possibly exposed areas of the skin. Suitably resistant clothing must be worn. Hats are often involved. Children are instructed to return every hour or two for re-application of the sunscreen. All enthusiasm for going outside is depleted with every passing minute. If I had to go through a 30 minute ritual every time I wanted to go outside, eventually I just wouldn’t bother any more. I know that whenever I subject my children to this tortuous delay, I wear down their will to go play outside. I persist because I wouldn’t want to be thought of as a bad or negligent parent who won’t take simple precautions to protect his children’s health.

But I think the health concerns that provokes the anxiety induced sunscreen habit is mostly bunk, or at least poor understanding of the science involved. Exposure to ultraviolet radiation in sunlight can cause damage to cells that may eventually result in cancer, most often skin cancer. Getting a sunburn incrementally increases the chance of getting skin cancer. It would seem that applying sunscreen in a compulsive manner is a good way to reduce the chance of getting cancer, right?

Big disclaimer – I do have a B.Sc. in Genetics so I’m not totally ignorant about the cancer formation process, but it has been almost 20 years since I earned that degree. I am drawing on dated knowledge using a rapidly diminishing memory so this explanation is by no means authoratative. If I’m wrong, let me know.

Well – kind of but not really. For most people – those who are not genetically predisposed to cancer, there’s a chain of events that leads to the development of skin cancer (or any other kind). The first of these steps is that the DNA in cells must be damaged. UV radiation happens to do this extremely well which is why it is commonly used in genetics research to induce mutations in cells. Luckily for us, our cells (and all cells) have handy DNA maintenance enzymes that will repair damaged DNA. If our DNA gets a bit damaged by some errant UV rays, the damage is fixed up. Permanent damage can result if the damage accrues faster than it can be repaired. If the damage is not enough to overload the repair enzymes, we’re doing just fine. A momentary exposure to direct sunlight will not be enough to lead to permanent DNA harm. If there’s no permanent harm, then there’s no formation of a cancerous or pre-cancerous cell.

How much exposure can we safely be subjected to? I usually go by the 20 minute rule which as far as I know has absolutely no scientific basis, but it does seem to do the trick. Even someone with a complexion as white as a fish’s belly (like me at the beginning of summer) can safely be in direct sunlight for about 20 minutes. When someone has a darker complexion, by tanning or virtue of heredity, the time gets longer. By the end of the summer, I think my safe exposure time is about 45 minutes to 1 hour. A corollary to this rule is the shade rule – once you’ve reached the safe exposure time, go stand or sit in a shady spot for about 10 minutes. Give your DNA repair crew a chance to get caught up on their work. Then you can safely return for another period of exposure to the mutagenic rays of the day star. Using this rule, I have gotten through the entire summer without any sunscreen or sunburn, with one exception.

Is the use of sunscreen ever necessary? Yes, in situations where a person will be exposed to direct sunlight for periods of time long enough to overload their cell’s DNA repair process. In my case, it was while playing at the beach and in the lake at Waskesiu just last week. I did use sunscreen that day, but I also didn’t apply it everywhere resulting in a mild sunburn on my shoulders.

I think that it would be better for the health of children if we didn’t detain them for so long as they go outside to play. Instead of a half hour of sunscreening, we could take a half minute to tell them they shouldn’t stay out in the sun too long, and they should rest in some shade every half hour or so. The sunscreen will wear off in a couple of hours, but after repeated reminders they might follow the 20 minute rule without even being reminded.