[raverbashing]

Having your skin burned by sun rays (with a certain frequency) is worse than using sunscreen. And it is certainly not only 'mild cancer'

Constantly damaging a tissue (mechanical, chemical, radioactive damage) is a trigger for cancer

Not to mention the Ozone layer hole (in the southern hemisphere)

[beagle3]

And yet, athletes who constantly subject their body to mechanical damage, have a much lower incidence of cancer than the general population. Yes, there are a lot of confounding factors and it is hard to tell what causes what.

But there is also a lot of evidence for hormesis - the idea that small amounts of bad stuff is good for you; a small amounts of alcohol daily is better than no alcohol at all, and better than exactly same cumulative amount consumed weekly. And I assume the same thing goes for sun, and mechanical damage, although I'm not familiar with the literature.

[raverbashing]

The hormesis idea is nice, but it doesn't work if the damage is too much.

So I suppose a moderate dose of sunbathing is beneficial (and not only because of Vitamin D)

There are some cases where cancer is believed to be caused by repeated damage to a tissue, example (search for 'hot beverages') http://www.cancerresearchuk.org/cancer-info/cancerstats/type...

[guard-of-terra]

Even in the same age range? I imagine most athletes are in ages 16-35, where getting cancer is pretty rare (save for some inherited ones) and should be equal for all occupations and lifestyles.

[beagle3]

I'm not intimately familiar with the data, but results hold among multiple studies that, controlled for age, lifestyle, occupation, and just about any other parameter anyone ever controls for, athletes have lower rates of cancer, and professional athletes have significantly lower rates of cancer (although, that makes "occupation" a variable you can't control for, and it's hard to isolate many other factors, because e.g. those people almost never smoke, and almost always eat healthy. But as much as can be controlled, it seems like sport confers an advantage against cancer, despite subjecting a lot of tissues to repeating and continuous damage).

Statistics is confusing though.

It's possible that people who are less likely to get cancer (for whatever reason) are more likely to be better at sports, thus more likely to be pro athletes; and with the right base rates, it might mean that pro athletes are more likely to not get cancer BECAUSE people who are less likely to get cancer are often athletes. No study that I'm aware of ever tried that angle, and I'm not sure anyone ever collected the right data to try.