Comment by dn3500 4 days ago
I live in the tropics and there is plenty of sunshine here. So my skin doctor told me to avoid the sun at all costs, always wear suncreen and a hat, don't go out in the daytime. A few years of that and now I have a vitamin D deficiency.
I think we’re starting to find that the “if you get sunlight you will develop skin cancer” mantra is way overblown, if not outright wrong. Being out in the sun is good for humans. In fact, we need it. But modern life largely conspires to prevent it for most of the developed world. Even when we do, we slather ourselves with sunscreen that might be doing more harm than good. Better to wear long sleeves and a hat that you can take off and at least get reflected sunlight while wearing. Oddly, it turns out that our bodies have been tuned to survive outside. Whodathunkit?
Here’s my hypothesis: it’s not total sun exposure that causes issues, it’s inconsistent sun exposure. Those of us in northern climates experience an annual cycle of very high and then nonexistent sun exposure. This causes our skin to stop producing melanin during the winter and then leaves us vulnerable to sunburn in the spring and summer. If we had year-round sun then our skin would consistently maintain melanin levels and we wouldn’t have sunburn.
I’d love to know if there are any studies trying to answer my question.
This is precisely the picture that I seemed to get when looking at this in depth some time ago. Most meta-reviews highlight a correlation between _number of blistering sunburns_ and melanoma. Not between actual amount of UV exposure. You may think that they’re the same, but they’re not. In fact, the same meta-review was noticing weak anti-correlation between chronic sun exposure and melanoma, I.e. people who work outside shirtless actually have better odds than baseline.
Most risk seems to come from occasional exposure to extremely strong sunlight compared to your day-to-day baseline. Practically speaking, if your skin is able to tan, absorbing as much sunlight as your environment allows for most of the year, with the intrinsic gradual build-up over spring, should be harmless if not even beneficial.
Of course, this highly depends on your genetics and your location. Avoid sunbathing around the equator regardless. And if you’re physically unable to tan, as some people do, then this might not be true either. I couldn’t determine that as easily.
This, and we are staying inside most of the time, so when spring arrives, we won't have gradual exposure but exposure all at once on the first sunny weekend we decide to get some sun.
Funny story. I started doing the couch to 5k running plan a few years back in January. Come March I realised I'd actually managed to get a tan (living in the outskirts of London, UK being further north than practically all of the inhabited North Americas).
Just being outside in whatever the weather consistently for 30 minutes or so every other day.
There's a hole in the atmosphere where I live. Incidentally, one of the highest skin cancer occurrences in the world.
Calling it overblown, is... A dangerous sentiment.
We tore a hole in our atmosphere. This is not the natural way of things, no. But we do have to live with the consequences.
I agree. When it is sunny, I get at least 20 min of sun on my bare skin and in my eyes (not protected from UV by glasses) every other day as recommended by neuroscientist Andrew Huberman. I am however careful not to get a lot more than that at once and have high-UPF clothing, hat and sunglasses to protect myself if I ever do need to be out in the sun for an extended period. (I am of Northern European ancestry.)
Even though I believe that the vitamin D we can buy in bottles is probably just as good as the vitamin D my skin makes, I do not consider vitamin D supplementation an adequate replacement for getting UV light on my skin and in my eyes because vitamin D production is only one of the benefits of getting UV light on the skin and in the eyes. (BTW I think HN put way too much emphasis on vitamin D.)
There are UV light receptors (that use a compound called neuropsin to sense the UV light) on the skin and in the parts of the brain that receive UV light (which gets into the skull mainly through the eyes). These receptors have nothing to do with vitamin D. Getting UV light onto these receptors is a more potent trigger for the release of endorphins in the brain than exercise is.
Regular UV light exposure also increases levels of sex hormones in men and in women. In men, increasing testosterone increases optimism and motivation and drive. Again, IIUC this effect has nothing to do with vitamin D.
When people eat plants, the compounds (e.g., lutein, zeaxanthin and lycopene) that plants use to protect themselves from UV light and blue light tend to be absorbed and to end up in high concentrations in the retina. If you do what I do, namely, get UV light from the sun every other day in moderate doses, then I suggest making sure you are getting plenty of these compounds. (Alexis Cowan says that omega 3 is helpful here, too.)
> I get at least 20 min of sun on my bare skin and in my eyes (not protected from UV by glasses) every other day as recommended by neuroscientist Andrew Huberman
Andrew Huberman peddles nothing more than pop-science supplement grift. I highly recommend you get your health info from somewhere other than bro-optimization podcasts and "light therapy" hucksters.
Big old hole in the ozone layer right over North East Australia, I see dark skinned south Americans blistering because they spent too long in the sun.
Legend has it why Aussies call the English Poms, short for pomegranate, because they come over and get burnt to shit, end up bright red.
> Legend has it why Aussies call the English Poms, short for pomegranate, because they come over and get burnt to shit, end up bright red.
I love Aussies’ sense of humour!
Skin cancer is no joke, but I don’t wear much sunscreen because I don’t need to. I need all the vitamin D I can get. I wish I would’ve protected myself more earlier in life, though.
Same is a great part of the culture.
I'm also in the same boat but more out of laziness and hating being greasy.
Definitely wish I'd been more sun smart when younger though.
Having lived in the UK and Australia, they're not kidding when they have don't get skin cancer promotions. The most remembered one from my youth is Slip, Slop, Slap. So Australian. Slip on a shirt, Slop on some suncream and Slap on a hat.
And yet mostly living in Australia, (was only in the grey UK from 2.5 years in our 20's), I'm still vitamin D deficient, because the majority of my life I've been inside on computers, presumably like a large percentage of Hacker News readers.
Ironically, our suncream QA is crap and all of the supposedly good sunscreens with high SPF factors failed indepdent testing - even including the one recommended by the Cancer Council.
The sunscreen thing is atrocious, about 7 years ago I bought a big expensive bottle of LeTan spf50 waterproof sunscreen, had a big day at the beach but applied and reapply diligently following the instructions.
Burnt to a crisp, I emails them and never heard back, I can't image I was the only person to notice.
Which is why Im probably vitD deficient too, the sun is toobharde to spend any amount of time outside unprotected here.
It's now slip, slop, slap, seek, slide - shade and sunglasses!
Yea sun damage and cancer vs. vitamin d deficiency is a little bit of a balancing act. It also doesn't help skin color is very critical part in all of this but people view that topic as taboo to discuss. The entire reason for skin color variations is a genetic optimization for UV absorption at specific latitudes vs sunburn risks.
That and the other half of the problem is we are all sedentary as hell in all latitudes these days. Be it people hiding under AC at the tropics or hiding in heated homes in the north. We don't go outside to get enough sunlight and our fat reserves that store vitamin d don't grow large enough because we still don't go outside when the weather is tolerable.
> The entire reason for skin color variations is a genetic optimization for UV absorption at specific latitudes vs sunburn risks.
This seems obvious but was not confirmed by genetic evidence. The rate of adaptation turns out to be much higher than can be explained by skin cancer.
The real cause appears to be fertility. UV radiation breaks down folate (vitamin B9) in the bloodstream, and folate is critical for DNA synthesis and repair. Folate deficiency causes serious problems in pregnancy, neural tube defects like spina bifida, and may impair sperm production. So darker skin in high-UV equatorial regions likely evolved partly to protect reproductive capacity.
In the other direction, lower melanin production helps with vitamin D synthesis in lower sunlight environments. Vitamin D requires UV-B radiation to be synthesized in the skin, and melanin inhibits this. Vitamin D is also linked to fertility. It's involved in sex hormone production and has been associated with successful implantation and pregnancy outcomes.
If you're curious, check out Nina Jablonski and George Chaplin's work. Their hypothesis is that skin color evolution as fundamentally about reproductive fitness: dark enough to protect folate, light enough to synthesize vitamin D. Both nutrients affect fertility, fetal development, and offspring survival. They have an immediate primary impact on fertility and success, while skin cancer even in the most extreme environment/phenotype mismatch, has an onset after reproductive age.
> It's taboo when you tie it to all sorts of other things, say, how well they should do at school.
Vitamin D deficiency might affect how well you do in school though and skin color affects that a lot. People who don't live in their native environment get such issues, just like white people getting burnt easily if they move south.
Well, supplementing vitamin D surely is cheaper than dealing with accelerated skin aging and cancer. Unless your doctor is a vampire, I presume they didn't mean to imply you should never go outside, but rather avoid any direct sunlight. I suspect the shade and sunscreen wasn't the issue.
Reminder that the FDA recommended daily allowance of vitamin D is 10x lower than it was supposed to be, because of a math error, and they have never corrected it.
The abstract wasn't clear to me, but looking it up FDA recommends 20mcg = 800 IU, and the paper recommends 8000 IU. It seems like others are more conservative (7000 IU).
I don't think I've ever seen the 20mcg rec, everywhere I've seen was something like 2000 (and that's what the supplements come as), but P appears correct.
What was the math error that led to this? And I'm curious now how to get 8000 IU. Just take a bunch of pills all at once in the morning?
The paper referenced Finland, which seems like a strong confirmation of safety, but the best information I could find was https://www.ruokavirasto.fi/en/foodstuffs/healthy-diet/natio... . What effective IU dose are people getting in Finland with these changes?
> I don't think I've ever seen the 20mcg rec
The 20mcg rec (the wrong rec) is quite literally on every single nutrition label in America that has Vitamin D. Maybe you haven’t noticed it. Surely you’ve seen it if you’re in the U.S.
https://www.fda.gov/food/nutrition-facts-label/daily-value-n...
> What was the math error that led to this? And I'm curious now how to get 8000 IU. Just take a bunch of pills all at once in the morning?
Read the paper I posted. And it is easy to find 5000iu and 10000iu capsules at a drug store.
I don't know how it was approached for vitamin D, but it's all about the model they choose, which in the first instance is just something they pull out of thin air. For many water soluble vitamins and minerals the model is based on a threshold for urine excretion; up the dose until the study group is excreting as much as they take in. Until someone figures out otherwise--i.e. that it's too little, too much, or that other considerations need to be made--that's the basis for the RDA.
Between the vitamin D error (this affected US and Europe and probably more places) and the sodium/blood pressure study that was misleading if not outright false, it's amazing how a few data points can become widespread advice without much verification and follow-up.
I'm sure there's tons more cases that we don't even know about, not in the conspiracy sense, but more in the sense that there's some issues with how carefully these claims are validated before they get put out there as a rule to be followed.
Vitamin D and sodium are examples out of a couple core nutrients, and I could list other nutrients such as sugar or fat too. So the rate is not excellent.
> How many errors do police make? Actuaries? Security researchers?
They make plenty of mistakes too. What's your point?
Wearing sunscreen might be a good idea if you are white ethnicity (that is your ancestors lived in northern Europe for thousands of years).
For others. It depends.
Native South Americans, Africans and Indians seem to get skin cancer at much lower rates.
I can’t really check for the studies right now since I’m on the phone, but I distinctly remember being interested in the theme of skin cancer due to personal reasons, and that studies found that great exposure to the sun, although slightly increasing the risk of benign skin cancer, does greatly decrease the incidence of non benign skin cancer.
Here’s the American association of dermatology recommendation. They say don’t try to get your vitamin D from the sun. https://www.aad.org/media/stats-vitamin-d
Careful with this I took vitamin d every day no problem for a year. Randomly started getting heart palpitations one week and was trying to figure out why. Got an Apple Watch to monitor for a fib. Was asking myself what changed in my life that it happened all of a sudden and realized I had started taking K2. ChatGPTs theory is that it really made the absorption of vit d effective and led to hypercalcemia.
Stopped taking vit d and k2 it resolved after a week no problems almost a year later.
It should be the opposite, not taking K2 leads to calcification as K2 helps your body absorb calcium instead of lingering in your circulatory system.
Anyone reading any of this ignore it all and see a doctor/cardiologist/emergency if concerned.
Yea actually it was a while ago I think ChatGPT actually pointed out I was low on magnesium from vit d + k2 requiring/depleting more than usual leading to the palpitations.
Biggest takeaway is it’s easy to hit toxic levels when taking supplements so be careful.
well that would imply that these LLMs could be wrong and they should talk to a doctor instead - lunacy!
people should actually be more careful about taking medical advice from an LLM than grabbing a vitamin D supplement.
I mean, you're not wrong, but that's not what the discussion is about.
There's Vitamin K1 and Vitamin K2. Vitamin K2 is frequently taken alongside Vitamin D.
I have never wanted to flag a comment on hacker news more. Do you also recommend that people smoke based on... nothing but feelz?
I am 50. I had to have skin cancer removed from my face. I have never seen a more busy doctors office than this dermatologist's office. They were printing money. The waiting room was always full, half filled with men in their 50s up (so probably not getting cosmetic dermatology surgery). Some had noses/ears missing. Granted I grew up surfing in Santa Cruz. But don't think 'skin cancer isn't a thing'.
And the follow up discussion here. Do people here not have parents? Do you not talk to ANYONE over 50 about their lives? Skin cancer is actually real and common and scary AF.
Unless you're non-native and have redhead-style very white skin or some history, the doctor sounds overly cautious to paranoid.
Hundreds of millions live in such climates (including people with fairer skin) and have no problems, even though they don't do anything extreme like "avoid the sun at all costs, always wear suncreen and a hat, don't go out in the daytime".
I'm white and I lived near the tropics for a few years, big white and asian population, everybody was out in the sun all the time, hardly covered too. Skin cancer stats as good as Europe or US.