[aantix]

Anecdotally, whenever I go swimming with my kids in the summer, and I don't put sunscreen on right away, but let myself get some intense direct sun, I feel good and sleep really well that night.

As long as I don't let myself get in a red, sunburn situation.

[krrrh]

The number one reason I wear an Apple Watch all summer is the UV index complication. If the number is at 4 and trending down I let the kids run free.

[pazimzadeh]

Interestingly the best time to go out is at solar noon, when the UVB/UVA ratio is higher. Just go for a shorter amount of time to compensate for the higher overall intensity.

[tartoran]

That's only if you don't have a lot of time out. If you're planning to be out for a while I'd avoid being too exposed during the 12-3 window.

[pazimzadeh]

I agree, but you can titrate your exposure. So at the beginning of the season, in the 12-3 window you can start by going 5 mins without sunscreen for a few days, then 10 mins, then 20 etc. depending on your skin type.

The worst thing to do is to go from low exposure (i.e. winter months, or just constant indoor time) to long periods of exposure, even with sunscreen.

[otikik]

My country, Spain, is famous for its beaches. Everyone native leaves the beach in the middle of the day and returns after lunch/siesta, when the rays are less intense.

Tourists stay and get burn to a crisp

[pazimzadeh]

Cool anecdote but as I said, in the middle of the day you should go for a shorter amount of time (starting with just a few minutes) to get ideal UVB exposure.

Tourists are an especially bad example since they often work indoors all year or come from less sunny countries, so the sudden sun exposure is doubly bad for them.

Spain is sunnier yet has lower melanoma incidence than Northern Europe..almost like moderate sun exposure is protective, or that going from a cloudy country to a sunny area for a few weeks is especially bad - you can analyze it how you wish.

[anon48293]

Or like the people living there for generations have slightly darker skin which protects better against the sun..

[pazimzadeh]

For sure that contributes to their higher ceiling for exposure, and also makes it harder for them to get vitamin D, which is why they shouldn't avoid going to the beach until the sun is down, since as a population they are quite deficient in Vitamin D.

[Rnonymous]

Care to explain? Isn't UVB more harmful than UVA?

[pazimzadeh]

No, UVA is stronger and more harmful. UVA penetrates deeper in the skin, since it's stronger. UVB stimulates Vitamin D production, while UVA doesn't.

So almost anything that is "UV-blocking" (sunscreen, UV-treated glass) gets rid of all of the beneficial UVB before UVA starts getting reduced. So you are actually enriching your exposure to the most harmful UV type, and not making Vitamin D.

This might explain the paradoxical finding that people who use sunscreen more can have higher rates of skin cancer

https://pmc.ncbi.nlm.nih.gov/articles/PMC10840669

[miladyincontrol]

Confounding by indication.

People who spend more time outdoors are more likely to try to wear sunscreen, as are people who already got a lot of pre-existing risk to excessive sun exposure.

Key word on try as its greatly assuming there isnt a wide audience who do use sunscreen, then just apply it in poor amount, or never re-apply but enjoy staying out far longer than most do in the sun feeling they're oh so very protected.

Spray sunscreens for example are just about useless, as are those solid stick applicators. They only get a fraction the amount you need for the rated protection. The biggest issue with sunscreen relates to companies selling sub par "convenience" slop, often right beside their other products some of which might actually be half decent.

[pazimzadeh]

Sure that’s a theory, but hasn’t been proven. If I recall, the study showed that heavy sunscreen use amongst sunscreen users was associated with higher cancer rates.

Secondly, if sun exposure is really that bad then how do you explain why most skin cancers are on the trunk and thighs rather than more exposed areas like hands and arms?

The simplest answer is it’s not sun exposure that’s bad but sudden high exposure after non-exposure (repair mechanisms can’t keep up with damage).

Not sure why I’m being downvoted. I guess there’s a lot of sheep among us. If anything I said is incorrect, please show me the evidence.

[KetoManx64]

Vitamin D levels are directly tied to melatonin production, that's why the less sun you get the worse your sleep gets. Vitamin D also lowers inflamation throughout the body.

[bob1029]

I can spend a solid hour in the sun before I start to burn, assuming I have a hat on my head.

I've also noticed some correlation between my diet and how fast I burn. Whenever my metabolism is running at/near ketogenesis, it seems like it takes a lot longer for the sun to affect me.

[IshKebab]

Just so you know, burning & cancer isn't the only reason to avoid strong sunlight - it also causes skin aging (i.e. wrinkles). If you don't want to be super wrinkly when you're old, wear suncream!

[causalmodels]

When we were dating, the first thing my now wife did was get me on a regimin of sunscreen and tretinoin. I now have significantly fewer wrinkles than my younger siblings (2-3 years).

[emmelaich]

I'd be wary of that! Tretinoin has been linked to birth defects in women and they are warned against it. I wouldn't trust it for the father either.

[tony_cannistra]

This is a common misconception. Topical tretinoin has been shown to have no effect on the fetus. Oral tretinoins (like isotretinoin) have been linked to congenital defects. This is due to the differing rates of absorption and the resulting ability for the retinoid to cross the placenta at higher concentrations.

With that said, folks who are pregnant are discouraged from using any retinoids out of an abundance of caution.

[Ralfp]

Yes, some stuff make your skin more sensitive to light than others. For example, you should avoid vitamin A creams and some herbs during summer because they increase risk of permanent skin discoloration.

[pazimzadeh]

Which herbs

[butvacuum]

also: citrus- wash your hands after.

[spacephysics]

I experienced similar reaction when i was doing keto. It became far more difficult to burn that summer

[ShinyLeftPad]

Why did you stop?

[milesvp]

Most likely that’s the nitric oxide (not to be confused with nitrous oxide) that is a biproduct of vitamin d synthesis which requires UV light. It is a natural muscle relaxer and is generally considered good for blood pressure and heart health in general.

[porridgeraisin]

Nutri oxide production is triggered by UVA, vit d which happens due to UVB.

[ThrowawayTestr]

Vitamin D deficiency

[GlickWick]

Definitely not. Vitamin D takes a while to synthesize and build up. A quick fix like this isn't possible.

[pixel_popping]

It's just that getting sun is healthy (in moderation) and our body reward us, we have this new anti-sun obsession which is likely to cause many health (and mental health) issues

[GlickWick]

I don't think it's that simple, and making it seem that way is counter-productive towards understanding what we should/shouldn't be doing.

There's no anti-sun obsession, either. Sunscreen isn't anti-sun, and people are well aware that Vitamin D synthesis is an issue in farther northern/southern latitudes. There's definitely an increased recognition scientifically that excessive sun is extremely bad, though.

[pixel_popping]

I would assume that many are taking Vitamin D, but there is still a major difference, if I spend few days no-lifing and I suddenly go out in the hot sun and comeback home 30min later, I feel much better, something happens internally, could be from the light itself, unsure, but I'd say for example to fight off depression, getting under the sun is quite powerful and will definitely improve your chances of getting out of it.

I let my 2-year old child (she is also taking Vit D - 300iu a day) under the sun in the garden quite a lot on/off (I'd say probably 1h a day in total) and I find that she sleeps much better and is more calm in the evening as well, I can't say the same if we do an outing to the mall, something is clearly different/rewarding.

[brightball]

I typically do the same thing. I only wear sunscreen if I am planning on being in direct sun for an extended period of time where I can't easily get back in the shade.

The more you're able to build up a base tan the less you need it to avoid a burn at least.

[vondur]

I'm pretty light skinned and the burn pretty easily. I just put on sunscreen by default when going hiking/mountain biking. I'm really excited for the new sunscreens coming out here in the US that have those new to us ingredients that the Euro's have had forever.

[brightball]

Agreed completely. I also leverage sun shirts quite a bit.

[nomel]

I discovered sun shirts very recently, with a hood. It's so much nicer to slip it on than apply sun block, which I'm trying to reduce since I don't really want it in my blood stream [1]. Mine is white, so I usually end up a bit cooler than without!

[1] https://jamanetwork.com/journals/jama/fullarticle/2733085?gu...

[NikolaNovak]

Isn't tanning basically body's reaction to cellular damage? It reduces further damage but that's due to damage done?

(It's largely irrelevant to myself, I pretty much burn immediately and don't / can't really tan, but my wife and her family tan well).

[HedonicEscal8r]

Yes, tanning is downstream of the activity of the p53 tumor suppressor protein in response to UVB-induced damage: https://www.lesswrong.com/posts/EFiCGc3YwadZBzvZ3/contra-byr...

[worldsavior]

The damage gets healed at sleep. Tanning reduces the need to heal.

[brightball]

30 years ago I was a lifeguard and got to experiment with this some. I can't tell you the biology specifically, but I have always tanned quickly. The less tan I am, the more easily I burn.

Always been that way for me at least.

[JoshGlazebrook]

So we're just out here perpetuating myths on here now as well?

[brightball]

Correction - The less you need it to avoid a burn.

[stevekemp]

I'm a pale-skinned redhead, covered in freckles. For me there is no such thing as a "base tan".

I get can get sunburnt from as little as 30 minutes in the sun at times, and I almost always wear sunscreen in the summer for that reason.

(Biggest issue is wearing sandals and forgetting to cover my feet, or when jumping in the lake after sauna and not covering up again quickly enough.)