No, because they have a demonstrable mechanism from pre-established science: UV radiation damages DNA, which causes cancer. Their product absorbs or scatters UV radiation.

This is the same as the teeth flossing skeptics: observational studies suggesting a paradox are interesting, but they actually need to unearth convincing alternative models with at least as much support as the dominant one for why they're right.

> No, because they have a demonstrable mechanism from pre-established science: UV radiation damages DNA, which causes cancer. Their product absorbs or scatters UV radiation.

As mentioned in article, but also some general knowledge in physics is that interaction of radiation with the matter is probabilistic. It is not like every quantum of UV radiation will always damage DNA, which always result in cancer. There's some "conversion funnel" that depends on a number of parameters, and the actual probability of cancer in the end could indeed be lower than probability of the negative consequences of low sun exposure. Even if physical mechanism of diseases is established, it does not mean we should always avoid the risk by disabling it by some expensive means. Sometimes it is low enough to accept it or mitigate (e.g. by efficient cancer treatment).

The article did describe some mechanisms, for instance the skin uses UV to make nitric oxide, which is known to lower blood pressure. That said, I'm not sure why this would be better than just taking nitric oxide. The same question comes up for vitamin D, and it's noted that supplements don't seem to help there -- with no explanation for that. So I would agree that the explanations for the pro-sunlight case are weaker.

   That said, I'm not sure why this would be better 
   than just taking nitric oxide

One might do well to start with the assumption that "taking XYZ orally" is not as effective as producing it naturally.

The digestive system involves a pit of acid and a diverse, poorly-understood, and variable biome. It is an extremely fraught and indirect way to introduce substances into the body. Obviously many things can be introduced this way, but the list of those that can't is probably longer than the list of things that can.

Well, I never said "orally." If it's beneficial to get NO via sunlight on your skin, it doesn't seem crazy that it might work via some lotion. Even considering oral supplements, one might also take a precursor if the molecule itself isn't stable in the stomach.

It's true there may be some important difference between sunlight-induced NO generation and whatever other supplement/injection/lotion/etc, but my point here is that the right approach is to focus on the mechanism, and avoid the naturalistic fallacy.

Surely you'd need to smear sunlight lotion on your skin if you want to use the existing the dermal route?

Not to mention that one of the premises of the article was that vitamin d levels were a marker, not some singular responsible agent.

The conclusion that vitamin D levels are an effect not a cause came from exploring the mechanisms. And yes, it may turn out that NO similarly is a marker.

It's ironic that the author didn't consider that getting sunlight may similarly be the side effect of the true cause of the stated benefits (being active?).

It may be, but NO itself is also very much a vasodilator, and used therapeutically for that.

One reason getting these from the evolved route may be better is because feedback mechanisms stop making the beneficial substance when the body has enough, which may not happen via intake by other methods. This is the case for vitamin D from sun vs oral D supplements. Serum levels stop going up when they reach a natural adequate evolutionary range if it's coming from sun. I don't know if that's true of NO or not. Or of melatonin from the near-infra-red wavelengths, but I wouldn't be surprised.

> This is the case for vitamin D from sun vs oral D supplements.

Wait, has there been a study suggesting this? This implies that there's a narrow optimal range and exceeding it causes problems. Seems you would see this in the supplement trials. Vitamin D toxicity doesn't occur until you take many times the RDA for months, and presumably none of the supplementation trials went anywhere near that high. https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...

This feels wrong, too. You are presenting one option as a settled thing because it has a proposed mechanism.

I agree that just dropping a seemingly safe belief should take effort. I have no problem challenging them on a regular basis, though. Especially with more than just arguments and thought experiments. More observational studies can almost certainly only be a good thing.

GP didn't say that the science of sun exposure is "settled."

Also, that UV damages DNA and causes cancer isn't simply a "proposed" mechanism, it's been tested many times.

I would say pure "observation" per se has little value -- for it to be scientifically valid it needs to seek explanations.

Observational studies are certainly science. Any claim against that is going to be hard to defend.

The mechanism isn't really at question. But just as sun exposure can kill grass, so to can lack of sun. We know that humans don't do photosynthesis, but it seems reasonable to ask if we do get other benefits.

Note. Is reasonable to ask and study. Is not reasonable to just assume the conclusion.

By "observational" studies I realize you probably just meant studies where they don't manipulate a variable (which, while less than ideal, it is indeed science), whereas I was making a more philosophical point, a la Popper https://www.goodreads.com/quotes/778918-the-belief-that-scie...

Ah, makes sense. You are correct in what I was referencing. To your point, I would expect most observational studies to be done with the expection of validating understood mechanisms.