It’s great that people are finally talking about this. It should have been obvious that sun exposure without sunscreen is needed to some extent. If you’re blocking the UV all the time, then how could you possibly be getting the minimum UV exposure that you do need. But people have become absolutely obsessed with sun protection.
flyingshelf · 2026-06-29 08:39:04 UTC
I don't know of anyone using sunscreen from the moment they wake up until they go to sleep. Guaranteed that even the best user will still receive a healthy amount of UV even if they refresh every few hours. As far as I'm concerned sunscreen is a 10am-5pm endeavor, not needed before or after
Zenbit_UX · 2026-06-29 08:52:41 UTC
Worth noting here for any readers new to UV guidelines that the above rule isn’t necessarily helpful for you. I’m currently traveling in an area that is 8:30am-4:30pm and live in an area that’s 10-6 pm in the summer and shifts throughout the year.
The actual rule is derived from your location’s safe UV index zones, which is found out by determining what local time the UV Index <= 2. Above 2, wear some amount of protection.
sevenseacat · 2026-06-29 10:03:53 UTC
That's basically sun up to sun down, here.
It's been completely grey, overcast, and raining here all day and the UV index sat between 3 and 5.
Zenbit_UX · 2026-06-29 11:59:48 UTC
Ya, the relationship between UV and sunlight is strange and unintuitive. For that reason I use a UV widget on my lock screen.
I find that being exposed to the value (e.g. 4) while being able to see the suns effect (e.g. cloudy) gives me a better feel for conditions.
flyingshelf · 2026-06-29 18:10:52 UTC
The worst sunburn I ever got was on a boat while overcast. I don't trust them clouds no more.
plorkyeran · 2026-06-29 21:57:41 UTC
Clouds block a decent amount of UV on average, but it’s much less consistent than you might expect. 9/10 you might be completely fine with no sunscreen and then get a horrible sunburn the tenth, with no apparent visual distinction between them.
rcxdude · 2026-06-29 08:57:06 UTC
Sunscreen isn't a 100% block, though. In fact it's advertised by what proportion of the UV it blocks. And in general it's far more common to have too much sun exposure than too little, and in the areas where people have too little, it's not exactly the norm to wear sunscreen every time you step outside.
erelong · 2026-06-29 07:23:37 UTC
tl;dr you probably should get a few minutes of sunlight daily on your unexposed skin without sunscreen for the "health gains"
(you can also wear clothes to block sun instead of sunscreen so you don't necessarily need sunscreen at all)
maleldil · 2026-06-30 13:51:25 UTC
You still need it at least on your face and hands. A hat won't completely protect against UV, and you're probably not going to wear gloves in the summer.
dntrkv · 2026-06-29 07:26:24 UTC
So everything in moderation? Cool, glad my philosophy still applies.
TacticalCoder · 2026-06-29 21:54:15 UTC
Extreme tension leads to breakage. Something something in buddhism about not trying to put too much tension in a bow or it'll break.
Also known as the middle way.
Moderation is a great philosophy.
echelon_musk · 2026-06-29 22:18:09 UTC
> something in buddhism about not trying to put too much tension in a bow or it'll break
The article seems to be a meta analysis of a bunch of conflicting research to support a narrative that we don’t really know shit.
And fair, we don’t.
But a couple of things we do know that weren’t covered - egregiously so - is that aging is UV damage. Sometimes called photoaging, wrinkles, sun spots, discoloration, fine lines, grey hair, all of that shit that you associate with someone visibly looking old is sun damage.
So the picture that the article paints of some pasty nerds in offices shielding themselves from all UV and thus: they might as well be smoking… it doesn’t even touch on why people might be doing this.
Both kurgezadt and veritasium did some really great videos on photoaging and it’s worth checking out if this is new information to you.
JR1427 · 2026-06-29 09:26:55 UTC
I've not heard that grey hair is sun damage.
Do you have any sources for that?
Zenbit_UX · 2026-06-29 11:53:19 UTC
There’s plenty, though please evaluate the veracity of their claims for yourself, I’m not a scientist nor do I excel at parsing scientific articles. Here’s one I’ve come across after a few minutes which references many others https://www.sciencedirect.com/science/article/abs/pii/S10111...
JR1427 · 2026-06-29 13:05:37 UTC
After a quick skim, that article seems to be talking about something other than typical age-related greying. More photobleaching.
Zenbit_UX · 2026-06-29 13:22:10 UTC
From the conclusions:
> Sun radiation affects hair properties as color, luster, mechanical resistance, the content of proteins and others.
TLDR Yes it impacts color. Further reading can be found in the 75 studies that can be found in the references section.
JR1427 · 2026-06-29 13:43:59 UTC
When most people think of age-related hair greying (which you referenced in your original post), they think of the phenomenon whereby hair follicles stop producing pigments that colour hair.
This is distinct from UV bleaching of the pigments in the hair.
mianos · 2026-06-29 23:07:24 UTC
Which grows out. So if it was substantial, you can just stay inside a while and eventually your hair will grow out and replace the faded hair.
JR1427 · 2026-06-29 13:46:23 UTC
If hair greying was mostly caused by UV damage, I would expect that the pattern of greying would be even, and begin on the top of the head.
In contrast (based on my own unscientific observations!) greying typically begins in small areas, and often on the temples - not what I'd expect if caused by UV damage.
gib444 · 2026-06-29 22:03:47 UTC
Now I'm curious why it starts on the temples (it's where mine started too, then my fringe)
ButlerianJihad · 2026-06-29 22:53:11 UTC
If you compare President Obama photos (2008) to President Obama photos (2016) you may conclude that he spent most of his time lounging on the beach?
Pro golfers look a good 10-20 years older than their real age sometimes fwiw. In contrast to most other pro athletes in indoor disciplines who generally look better than their age. There's also examples of truckers who spent most of their career with the window rolled down and you can tell straight up what side of the road they drove on.
thih9 · 2026-06-29 21:39:07 UTC
Truckers, plural? Is there an example that isn’t William McElligott from the famous photo[1]?
Those drivers don't even need to have the window rolled down as far as I know. That's because most door auto glass lets UVA rays through and that's what causes premature aging. If you want to block those UVA rays, you would need to apply some kind of additional film to the side window.
Rendello · 2026-06-29 22:19:32 UTC
I first took sun exposure seriously after backpacking and spending time with other young travellers in hostels. It was apparent who spent their time exposed to the sun, I remember a girl my age who was in the middle of a multi-year cycle tour, and although I envied her journey, her skin looked quite rough. I decided that if I ended up doing that, I'd get one of those cycle helmet brim visors and would probably just cover my face during a lot of the riding portions.
Then I met a man who did kayak tours of a city. He was awesome, but really leathery due to the 20 years in a boat without shade and having the UV reflections off the water. Your skin cancer risk is off the charts at that point.
dghlsakjg · 2026-06-29 23:30:50 UTC
I used to work on boats in the Caribbean.
After my first few months there I realized that the people who didn't look like an old leather bag wore long sleeve shirts and big hats pretty much constantly.
pneumic · 2026-06-30 00:01:32 UTC
The sunny side of the road?
tasty_freeze · 2026-06-29 22:31:25 UTC
I often embarrass my daughter when she has some new friend over. If the topic comes up, I give a demonstration. I'm 62 and I've never tried to get a tan and work indoors, and I haven't had a serious sunburn in close to 40 years. On the other hand, I lived spent the last 20 years in Austin, TX. I mow the yard and I ride a bike and in the summer months I put on sunblock before doing the bike rides an sometimes mowing.
The exposed parts of my arms look like I'm 62 -- freckles, some age spots, the skin has lost a lot of elasticity. But then I roll up my T-shirt sleeve to expose my shoulder and my skin is like it was when I was 25: not just pale, but no freckles, no age spots, still supple.
eager_learner · 2026-06-29 23:03:52 UTC
the culprit is not the sun-- but overdoing it. If you overdrink water, it is fatal, too.
The sun is responsible for benefiting over 200 processes in the body. And you don't need to be out in the sun all day to get the benefits (if your job does not demand it).
maleldil · 2026-06-30 12:50:56 UTC
It's far harder to overdrink water than it is to overstay in the sun.
jodrellblank · 2026-06-29 23:29:46 UTC
Photo claiming to be a 92 year old woman who used suncream on her face, but not her neck, for 40 years:
That seems to be something you have 'hallucinated'?
DANmode · 2026-06-30 18:53:36 UTC
You think that happened to her from a single exposure?
A handful of exposures?
She looks like a football!
Who’s hallucinating?
krupan · 2026-06-29 22:35:26 UTC
Who cares about your skin looking a little older when it prevents cardiovascular related deaths??
floren · 2026-06-29 23:02:20 UTC
I'd rather look old than be one of those lunatics who goes for a summer walk in a longsleeve shirt, gloves, and a hat with built-in veil (a pretty common sight in the Bay Area)
littlexsparkee · 2026-06-30 04:44:30 UTC
Sounds like my parents, I would always sweat our beach walks with my mom wearing a nose protector that resembled a beak
aranelsurion · 2026-06-29 23:40:50 UTC
> kurgezadt
I suffered with German too, in fact, still do :)
As a trivia: "kurz gesagt" -> kurz: short, gesagt: said. "sagen" is the verb "to say", "ge"+"t" is to form the past participle. (but not always :)
jml7c5 · 2026-06-29 10:02:15 UTC
(2019)
Cockbrand · 2026-06-29 11:09:22 UTC
A bit unclear - it says
> Weller’s largest study yet is due to be published later in 2019
But in the header, it also says
> Updated May 31, 2024
I'd still love to know whether there has been further research in the meantime.
Coming from the skin cancer capital of the world (Australia) - no, no it is not
jhbadger · 2026-06-29 22:01:50 UTC
Yeah, lack of Vitamin D may or may not be a problem (well, obviously in extreme cases it leads to rickets, but that's rare). But skin cancer unquestionably is a problem, and not infrequently a deadly one. Pick your battles.
amanaplanacanal · 2026-06-30 00:12:22 UTC
Very infrequently. Total death rate per year in the US is something like 900 per 100,000 adults, of which less than 3 are from skin cancer. Heart disease, stroke, other cancers, accidents, are all much bigger.
kulahan · 2026-06-29 22:25:26 UTC
Australia is kind of an exception. You’ve got a super outdoor culture, a bunch of fair-skinned people, thin ozone, and very clear skies.
kirrent · 2026-06-29 23:14:13 UTC
The title is inadvertently correct only because modern margarine is healthier than alternatives such as butter.
picofarad · 2026-06-30 04:39:47 UTC
Seed oil is healthier than milk fat? Going to need some framing definitions, here...
kirrent · 2026-06-30 06:57:27 UTC
I had to look up the concept of a framing definition so I might have gotten these wrong but I would equivalently state:
1. Modern margarine is healthier than butter.
2. Seed oils are generally healthier than animal fats.
3. PUFAs are healthier than saturated fats.
4. In this case the industrial processed spread is healthier than the more natural less-processed spread.
audunw · 2026-06-30 08:21:58 UTC
PUFA vs saturated fats come with a lot of caveats. It's generally good advice to avoid saturated fats, but there are only certain conditions in which saturated fats are unhealthy and we don't fully understand those conditions yet. Saturated fats from dairy is even more complicated. It's may not be as bad as other saturated fats.
Recently there are very good studies tracking heart disease progression with extreme accuracy and it is very clear that you can eat high amount of saturated fat for a very long time with zero CVD progression. The mechanism depends on other factors.
Still, personally I think it's good advice to reduce saturated fat until we understand these mechanisms better. Eventually though, I suspect we will find other interventions that eliminate the CVD impacts of saturated fats.
I gotta imagine that margarine with EVO is a clear winner, EVO has several great benefits. Not saying processed seed oils are bad.. I'm not in that camp. Evidence for that idea seems very flimsy.
kirrent · 2026-06-30 08:37:49 UTC
By all means please caveat away! This is HN after all. I was torn between pithyness and qualifying those statements myself. Obviously there's a lot of interesting variation that's not being captured by population means or the limited subgroups we've studied and I'm excited for us to learn more.
In the meantime, I use butter because it's tastier and for me that's worth it. I don't understand why that's not enough for some people.
I have heard that some Asian or European sunscreens have some UV blockers that are much more stable than the ones that are mainly used in sunscreens available in the USA. So if you’re using one of these, the need to reapply isn’t as much of a concern. The only thing is that they aren’t FDA approved.
Some examples I have heard of are “ethylhexyl triazone”, “diethylamino hydroxybenzoyl hexyl benzoate”, and “bemotrizinol”.
EDIT: The last chemical on my list was actually approved by the FDA this month (June 2026).
DuckConference · 2026-06-29 23:41:56 UTC
Yes. Most modern sunscreens are photostable, but even if you aren't going in water or sweating, just moving around (and thus scrunching and un-scrunching your skin on a micro level over and over again) is enough to mess up the sunscreen layer you put on your skin.
This is one of those things that will start a fight at a beach party so I'm just goongtto forget the two tenuous studies the FDA used to stand up the guidelines.
toasty228 · 2026-06-30 08:00:33 UTC
It depends what sunscreen you use: mineral vs chemical font behave the same, on how much you used, on what you're doing.
Chemical ones go bad with exposure to sun, mineral ones not as much, but either way they can both be rubbed off the skin
yixu34 · 2026-06-30 16:36:41 UTC
I'd suggest checking out Lab Muffin Beauty Science's videos and blogs. The tl;dr is that ideally yes, not because modern sunscreens break down (they're generally pretty photostable), but because your skin cells move over time and create gaps in coverage.
Side note: you can also buy a UV camera on Amazon that shows your suncreen application coverage!
Cider9986 · 2026-06-30 18:29:08 UTC
That's cool, do you have one?
layman51 · 2026-06-29 21:41:02 UTC
Does anyone know whether UVA or UVB is more conducive to producing vitamin D naturally? A quick search shows me that it is mainly UVB that's responsible for that, but unfortunately, this is what gets blocked out by glass windows and sunscreen. On the other hand, UVA is what causes early aging.
So this is just an unfortunate situation because I don't think there's a way of just getting UVB into you in a safe way.
krupan · 2026-06-29 22:36:48 UTC
The article explains that it is much safer than not getting UVB. Nothing in this universe is completely safe, but the evidence is that getting UVB is bar far safer than not getting it
jodrellblank · 2026-06-30 01:49:24 UTC
UVB makes it.
UBA denatures it[1], which I thought was how we avoid overdose levels building up in the skin when outside, but can't find a source for that.
Offhand, what was the overdose level? Because 150ng/ml (adjust if I messed units up) isnt an overdose and most people are around ~50 unless they supplement (I mean people outside the 25th parallel.) I think even approaching 300ng/ml is possibly safe as long as you're accounting for the calcium.
I aim to be around 105ng/ml.
jodrellblank · 2026-06-30 16:34:30 UTC
I have no idea what the numbers were, I took it in as a system idea: more time in sunlight, more UVB, more Vitamin D. Then UVA breaks it down slowly, so more builds up in the skin, more is being broken down, acting as a control-feedback brake on the increase.
> "unless they supplement"
I have seen plenty of claims that low levels of Vitamin D correlate with many diseases and overall mortality, but that supplementing Vitamin D hasn't been proven to help. Is there any consensus on that?
> "as long as you're accounting for the calcium".
Vitamin D helps bodies absorb calcium but has concerns about high blood levels of calcium. Taking Vitamin K2 as well helps redirect that calcium to the bones instead of the artery walls, apparently. But high levels of Vitamin A could also be causing loss of bone calcium into the blood:
"""in the industrialized world excess of vitamin A has been suggested to be a risk factor for secondary osteoporosis and enhanced susceptibility to fractures. Preclinical studies unequivocally have shown that increased amounts of vitamin A cause decreased cortical bone mass and weaker bones due to enhanced periosteal bone resorption. Initial clinical studies demonstrated a negative association between intake of vitamin A, as well as serum levels of vitamin A, and bone mass and fracture susceptibility. In some studies, these observations have been confirmed, but in other studies no such associations have been observed. One meta-analysis found that both low and high serum levels of vitamin A were associated with increased relative risk of hip fractures.""" - https://pmc.ncbi.nlm.nih.gov/articles/PMC11070503/
which could be a confounding factor with Vitamin A and its precursors in so many animal and plant foods and fortified into more, and in daily multivitamin supplements, skin creams, moisturisers and such.
jondcallahan · 2026-06-29 21:44:21 UTC
I made a small little web app calculator for myself and my family to figure out how long we could stay outside without needing sunscreen based on current UV and skin type. I use it daily in the summer and a couple thousand people use it every month also. You can check it out at https://sunburntimer.com. It's also free and open source software, github link in footer.
Arubis · 2026-06-29 21:59:25 UTC
Denver, CO, USA resident here -- this looks _super_ useful and I'm likely to start using it heavily. Our weather here is usually very outside-encouraging (if getting hotter over the years) and our UV is _ridiculous_; I see the index hit 11 and 12 with some regularity. Thanks for the link!
Yep, this—we aren’t as close to the equator, but there’s less atmosphere to filter UV. Not so much in terms of beach days, of course, so sunburns here tend to be less than full-body.
All that said: a daily mean of 13-14 is past what we’d see here—and yeah that is some serious burning.
hankbond · 2026-06-29 22:22:23 UTC
This is awesome thank you for making this!
fullykubed · 2026-06-29 22:41:32 UTC
Looks like the weather might be a bit off, I imagine from your upstream provider. In Indianapolis, all stats look correct except it says we have thunderstorms. Couldn't be a clearer day and nothing on the radar.
eurleif · 2026-06-29 23:24:03 UTC
It would be useful to have an option to change the time of day, rather than always using the current time; e.g. for planning at night what to do tomorrow.
tele_ski · 2026-06-30 01:25:28 UTC
I came here to post this so glad I'm not the only one looking for specific time of day. Or at least give the user the estimated time they can be outside before getting burned? The timer feels great to fire and forget but I might want to plan and I couldn't figure out from the UI what the duration is "safe"
eurleif · 2026-06-30 21:09:00 UTC
It looks like the "Skin Damage Over Time" chart is the same information as the timer.
This is neat if you are avoiding the "getting red". My understanding is that the damage occurs with or without the sunburn but maybe this goes without saying.
giwook · 2026-06-30 00:24:48 UTC
This is a clever idea.
Unfortunately, UV exposure is cumulative. So your skin is still getting damaged by the UV rays even if you're not getting burnt.
TurdF3rguson · 2026-06-30 00:45:33 UTC
Cumulative but with a repair mechanism. There's not necessarily "rollover exposure".
littlexsparkee · 2026-06-30 04:41:52 UTC
There are temporary as well as permanent effects and the repair mechanism can be overwhelmed: photoaging, age spots, mutations.
TurdF3rguson · 2026-06-30 07:46:05 UTC
Right but there are common precautionary rule-of-thumb heuristics which lead normal people to believe that every sun exposure brings them a little closer to death. That's exaggerated. Or at least, the claims are widely contested.
smallpipe · 2026-06-30 12:26:49 UTC
So how many Joules can you safely sustain in say, a month, or a lifetime ?
Comments
The actual rule is derived from your location’s safe UV index zones, which is found out by determining what local time the UV Index <= 2. Above 2, wear some amount of protection.
It's been completely grey, overcast, and raining here all day and the UV index sat between 3 and 5.
I find that being exposed to the value (e.g. 4) while being able to see the suns effect (e.g. cloudy) gives me a better feel for conditions.
(you can also wear clothes to block sun instead of sunscreen so you don't necessarily need sunscreen at all)
Also known as the middle way.
Moderation is a great philosophy.
Perhaps you are referencing AN 6.55 Sona Sutta.
https://www.accesstoinsight.org/tipitaka/an/an06/an06.055.th...
And fair, we don’t.
But a couple of things we do know that weren’t covered - egregiously so - is that aging is UV damage. Sometimes called photoaging, wrinkles, sun spots, discoloration, fine lines, grey hair, all of that shit that you associate with someone visibly looking old is sun damage.
So the picture that the article paints of some pasty nerds in offices shielding themselves from all UV and thus: they might as well be smoking… it doesn’t even touch on why people might be doing this.
Both kurgezadt and veritasium did some really great videos on photoaging and it’s worth checking out if this is new information to you.
Do you have any sources for that?
> Sun radiation affects hair properties as color, luster, mechanical resistance, the content of proteins and others.
TLDR Yes it impacts color. Further reading can be found in the 75 studies that can be found in the references section.
This is distinct from UV bleaching of the pigments in the hair.
In contrast (based on my own unscientific observations!) greying typically begins in small areas, and often on the temples - not what I'd expect if caused by UV damage.
https://commons.wikimedia.org/wiki/File:20081217_PRESSER-504...
https://commons.wikimedia.org/wiki/File:President_Obama_and_...
Edit: self answer, yes[2] (left side!)
[1]: https://www.cbsnews.com/news/trucker-accumulates-skin-damage...
[2]: https://www.mirror.co.uk/news/health/lorry-driver-ages-drama...
Then I met a man who did kayak tours of a city. He was awesome, but really leathery due to the 20 years in a boat without shade and having the UV reflections off the water. Your skin cancer risk is off the charts at that point.
After my first few months there I realized that the people who didn't look like an old leather bag wore long sleeve shirts and big hats pretty much constantly.
The exposed parts of my arms look like I'm 62 -- freckles, some age spots, the skin has lost a lot of elasticity. But then I roll up my T-shirt sleeve to expose my shoulder and my skin is like it was when I was 25: not just pale, but no freckles, no age spots, still supple.
The sun is responsible for benefiting over 200 processes in the body. And you don't need to be out in the sun all day to get the benefits (if your job does not demand it).
https://i.ytimg.com/vi/ITlo7TAy_Hs/maxresdefault.jpg
(She also appears to have Frank's Sign: https://en.wikipedia.org/wiki/Frank%27s_sign )
Don’t forget that step.
That seems to be something you have 'hallucinated'?
A handful of exposures?
She looks like a football! Who’s hallucinating?
I suffered with German too, in fact, still do :)
As a trivia: "kurz gesagt" -> kurz: short, gesagt: said. "sagen" is the verb "to say", "ge"+"t" is to form the past participle. (but not always :)
> Weller’s largest study yet is due to be published later in 2019
But in the header, it also says
> Updated May 31, 2024
I'd still love to know whether there has been further research in the meantime.
Searching for the title of the article ("Is sunscreen the new margarine?") makes it easy to pinpoint: there is a open letter responding to the article, dated January 15, 2019. https://www.asds.net/Portals/0/PDF/LetterToTheEditor-Outside...
1. Modern margarine is healthier than butter.
2. Seed oils are generally healthier than animal fats.
3. PUFAs are healthier than saturated fats.
4. In this case the industrial processed spread is healthier than the more natural less-processed spread.
Recently there are very good studies tracking heart disease progression with extreme accuracy and it is very clear that you can eat high amount of saturated fat for a very long time with zero CVD progression. The mechanism depends on other factors.
Still, personally I think it's good advice to reduce saturated fat until we understand these mechanisms better. Eventually though, I suspect we will find other interventions that eliminate the CVD impacts of saturated fats.
I gotta imagine that margarine with EVO is a clear winner, EVO has several great benefits. Not saying processed seed oils are bad.. I'm not in that camp. Evidence for that idea seems very flimsy.
In the meantime, I use butter because it's tastier and for me that's worth it. I don't understand why that's not enough for some people.
Current guidelines for sun exposure are unhealthy and unscientific – research (2019) - https://news.ycombinator.com/item?id=31471416 - May 2022 (335 comments)
Some examples I have heard of are “ethylhexyl triazone”, “diethylamino hydroxybenzoyl hexyl benzoate”, and “bemotrizinol”.
EDIT: The last chemical on my list was actually approved by the FDA this month (June 2026).
Chemical ones go bad with exposure to sun, mineral ones not as much, but either way they can both be rubbed off the skin
Side note: you can also buy a UV camera on Amazon that shows your suncreen application coverage!
So this is just an unfortunate situation because I don't think there's a way of just getting UVB into you in a safe way.
UBA denatures it[1], which I thought was how we avoid overdose levels building up in the skin when outside, but can't find a source for that.
Suggested as a reason why fair-skinned indoor workers are getting more melanomas, (ref glass blocking UVB and passing UVA): https://www.sciencedirect.com/science/article/abs/pii/S03069...
I aim to be around 105ng/ml.
> "unless they supplement"
I have seen plenty of claims that low levels of Vitamin D correlate with many diseases and overall mortality, but that supplementing Vitamin D hasn't been proven to help. Is there any consensus on that?
> "as long as you're accounting for the calcium".
Vitamin D helps bodies absorb calcium but has concerns about high blood levels of calcium. Taking Vitamin K2 as well helps redirect that calcium to the bones instead of the artery walls, apparently. But high levels of Vitamin A could also be causing loss of bone calcium into the blood:
"""in the industrialized world excess of vitamin A has been suggested to be a risk factor for secondary osteoporosis and enhanced susceptibility to fractures. Preclinical studies unequivocally have shown that increased amounts of vitamin A cause decreased cortical bone mass and weaker bones due to enhanced periosteal bone resorption. Initial clinical studies demonstrated a negative association between intake of vitamin A, as well as serum levels of vitamin A, and bone mass and fracture susceptibility. In some studies, these observations have been confirmed, but in other studies no such associations have been observed. One meta-analysis found that both low and high serum levels of vitamin A were associated with increased relative risk of hip fractures.""" - https://pmc.ncbi.nlm.nih.gov/articles/PMC11070503/
which could be a confounding factor with Vitamin A and its precursors in so many animal and plant foods and fortified into more, and in daily multivitamin supplements, skin creams, moisturisers and such.
https://www.bom.gov.au/climate/maps/averages/uv-index/?perio...
My area is similar to Sydney in your map. For Denver it’s the elevation that’s exposing them to more UV rays.
[1]https://www.epa.gov/sunsafety/sun-safety-monthly-average-uv-...
[2]https://www.reddit.com/r/MapPorn/comments/cd1t54/relative_la...
All that said: a daily mean of 13-14 is past what we’d see here—and yeah that is some serious burning.
Unfortunately, UV exposure is cumulative. So your skin is still getting damaged by the UV rays even if you're not getting burnt.