Hacker News new | past | comments | ask | show | jobs | submit login
Sunlight through glass does not provide Vitamin D (nytimes.com)
601 points by bookofjoe on Feb 25, 2019 | hide | past | favorite | 331 comments

It's worth noting that despite not providing Vitamin D, there's still a fair bit of value in getting sunlight through glass:

1. Seasonal Affective Disorder is treated using just the visible light spectrum entering the retinas of the eyes [1], and there are a ton of studies showing its effectiveness (in fact, most SAD lamps explicitly filter out ultraviolet light).

2. Some infrared passes through some glass and seems to be good for a thousand different things. [2] [3]

3. UVA passes through glass and has beneficial effects on the cardiovascular system. [4]

[1] https://www.sciencedirect.com/science/article/pii/0273230092...

[2] https://valtsus.blogspot.com/2017/05/the-therapeutic-effects...

[3] https://www.quora.com/Can-infrared-light-pass-through-glass

[4] https://www.sciencedirect.com/science/article/pii/S0022202X1...

There is a lot of value in being able to see the outside. I can barely see outside from my position in the building and I feel it's really starting to eat my soul staring at walls the whole day.

Have you tried plants? I can't see windows from my desk, but I've got my cubicle filled with plants & it kind of makes up for it. One is a tropical shrub behind my monitors which would swallow my whole workstation if I didn't prune it back. Now if only people who seem to like the gloom would stop disconnecting bulbs in the fluorescent light fixtures..

There is evidence[1] that tropical plants and microorganisms in the soil will remove VOCs from sealed indoor environments, although the effect will likely be limited in an open plan office. At least they are nice to look at.

[1] https://en.wikipedia.org/wiki/NASA_Clean_Air_Study

Critical Review: How Well Do House Plants Perform as Indoor Air Cleaners?


This might be of interest to you.

Oh... If only I could keep a plant alive in my office. I struggled with one for months, got it really healthy. Left instructions with co-worker and went to Europe for a month. While I was gone at least 5 people walked by that plant and said "oh, he's gone to Europe, I'd better water his plant for him". I get back and my plant is dead. My co-worker feels really, really bad about it and tells me he followed my interactions to the letter. It was over the course of 2 weeks that the other 4 people excitedly tell me that they watered my plant for me while I was gone, even though there was a little sign in it saying "please don't water me".

Facilities doesn't allow plants Everything needs to to dull, uniform and gray.


(Edit: That sounds very depressing, and could be health affecting in the long term, so if you can, please do leave!).

break up with your SO.

detach from the electrical grid

buy a van

Just bring one! They may not ask you to remove it.

Fluorescent light is typically low quality.

I would add early morning sunlight helps regulate circadian rhythm.

UVA is what causes skin cancers. Recommending or dismissing UVA exposure is irresponsible, especially in places with tons of UV radiation. Dermatologists go extra to teach people to choose sunscreen with good UVA protection, meanwhile Applied Science (one of my favourite youtubers) - “UVA penetrates regular window glass; hey its not to be worried about”...

Seems there's actually some debate on the net benefit/risk of this exposure [0]. Yes it raises risks for certain skin cancers but the survival rate of these is very high, meanwhile exposure decreases a collection of other risks whose death rates are much higher.

So I think the right course of action is a little more nuanced than simply saying, "UV increases skin cancer risk therefore ignore everything else as well as magnitudes of net risks/benefits". Should we not weigh all factors?


Actually, there was an article posted here (I think) not too long ago about a study that showed the positive benefits from sunlight were enough to outweigh the slightly increased chances of skin cancer.

I'll see if I can find the link.

Yeah I think it really varies by the region. Sure it's good to go outside in Sweden and England, but not in Aussie and NZ when you can get sunburn in about 15 minutes.

I've had couple of barbecue parties this summer in Auckland and NOBODY went outside until sun was way past 5PM. We preferred to sit in stuffy kitchen rather than enjoy beautiful beautiful outdoors. Even in middle of winter you can feel sun bite you as you stand in front of pedestrian crossing.

Trying to explain this to people visiting Australia is always amazing.

"It's so lovely and sunny here, why aren't you tan?"

"Because the sun is a terrifying ray of pain and death here."

The sooner we completely phase out CFCs and other stratospheric ozone depleting gases, the sooner we can go back to the good old days where you could enjoy that sunshine.

The prediction is 2050-2070 we will be back to the 1980 level of ozone thickness.

Scientists have been trying to combat the perception that it is to blame for the high prevalence of skin cancer in Australia for a couple of decades now - it will never be a good idea to 'enjoy that sunshine' the way people used to.

(2001 paper - https://pdfs.semanticscholar.org/6944/503469e4f779e99884e144... " Sufferers of skin cancer today should more likely blame their affliction on skin type and sun exposure during their youth than any changes in ozone distributions over the last twenty years. Therefore it is safe to say that even without ozone depletion, Australia would still have a very high rate of skin cancer.")

Can't agree more. It was pretty crazy in the 70s/80s.

You had people literally baking themselves in the sun with tanning oils. Even after "Slip Slop Slap" was first promoted in the early 80s everyone was still trying to get a tan.

Wasn't the worst of the ozone thinning over the poles? Not sure the ozone layer actually affects sun exposure in Australia or NZ.

Over Antarctica, yes. But in some conditions (right winds? I forget) thinner patches of ozone do blow over the south coast of Australia, and does increase UV exposure.

...and this is why about a third of us NZers have vitamin D levels that are below the recommended level (5% + 27% ~ 1/3).


Yep, whether it does or doesn't give you skin cancer, sunburn is really unpleasant. That's enough to put most people off.

Linked in sibling comment...

Thanks! That's exactly the one I was thinking of.

From wikipedia:

> Seasonal affective disorder is a mood disorder subset in which people who have normal mental health throughout most of the year exhibit depressive symptoms at the same time each year, most commonly in the winter.

I usually get depressed in the summer though, even when I get enough unfiltered sunlight.

There are all kind of things that happen seasonally that might dampen your mood (for instance people taking vacations, students being home from school, work being more/less busy, outdoor exercise options changing, etc). Your depression might not have anything to do with that and just be a random variation that happened to occur in the summer.

Most depression has nothing to do with SAD; it's merely a specific type. It's a type that has a fairly straightforward treatment, thankfully!

I often have a depressed mood in November and December when the sun is at its lowest, but my family also likes to make "the holidays" as miserable an experience as possible, so it's really no surprise and probably unrelated to light levels.

FWIW, I have the same symptoms in winter, but none of the reasons you list apply to me. I can easily see SAD being caused by lack of natural light, and I try to spend as much time as possible in sunlight (which is hard given a normal work schedule).

"most commonly", but there is some evidence that SAD is not triggered only by amount of light:

"This model also explains the otherwise confusing tendency of some SAD sufferers to get depressed in the summer. The problem isn’t amount of light, it’s circadian rhythm disruption – which summer can do just as well as winter can."


My question was: "Why does it block UVB?".

Found the answer on Quora: https://www.quora.com/Why-does-glass-block-UV

"With a band gap of 4eV, glass can't absorb any photons with less energy than UVB light; namely, it is transparent to UVA, visible light, infared, etc; but the higher energy photons can and are highly likely to be absorbed."

So it seems hard to create glass that doesn't block UVB.

Feynman knew this and claims to be the only person to have watched the Trinity test with naked eyes, rather than through welding goggles:

> In Surely You’re Joking, Mr. Feynman, American physicist Richard Feynman speculates that he may have been the only person who watched the Trinity Test relatively directly, using a windshield to exclude ultraviolet light. Everyone else, he claims, was looking through something akin to welding goggles.


I've never really understood this story. Feynman wasn't wrong, but UV-A and even sufficiently-bright visible light also cause eye damage.

Did he know the main visual hazard from the bomb was UV-B? Did he just get lucky?

We don't even know that he got lucky.

Lasers didn't exist yet to force us to study retinal exposure to bright non-UV light and the flash from the bomb didn't last that long, nor were the first few bombs that bright, so he may have been fine... but obviously if you stare at the sun through three inches of glass you're still going to burn your retinas.

He says "I figured the only thing that could really hurt your eyes (bright light can never hurt your eyes) is ultraviolet light. I got behind a truck windshield, because the ultraviolet can’t go through glass, so that would be safe, and so I could see the damn thing."

What we know from later laser research is that unless you have a comprehensive visual field test, it's often hard to identify that part of your retina has been scorched. Your brain just filters it out as a blind-spot and you don't realize what you're failing to see.

There's every chance that Feynman totally burned a section of his retina and never realized it, and there's every chance that he was fine because the exposure at his distance wasn't that bad, but at the end of the day he was more reckless than insightful in this situation.

Maybe he should have closed one eye, but the first atomic bomb only explodes once. Your body won't last forever no matter how well you care for it (as Feynman well knew, having just watched his wife Arline die slowly of incurable tuberculosis); seeing the first atomic-bomb test with your own eyes seems eminently worth the risk of blindness, or even sacrificing an eye.

I really can't agree. I would not exchange my eyesight for the whole world, literally. Therefore the qudos of having looked at a novel explosion in no way compensates for any risk to my eyes.

>I would not exchange my eyesight for the whole world, literally.

FYI vacuum exposure can cause blindness, visual impairment, and death.


Downvoted not because I’m afraid of my own mortality, but because pointing out the obvious fact that nobody can see after they die is neither insightful nor useful. Go tell that to someone who has become blind and let me know how much consolation that provides them.

Even if I knew was going to die tomorrow, I will not exchange my remaining eyesight for qudos. I would prefer to spend my last day looking at my family, the trees, the running water, the flowers. It seems totally uncontroversial to me, I'm really surprised to find someone who disagrees.

I thought the next few decaces was a climate change reference.

Sorry, no, I just meant that the maximum human lifespan recorded so far is 12.2 decades, and the vast majority of people reading this will die in even less, 2–5 decades, regardless of what happens with climate change. Given that, it's silly to treat your body as if you could make it last forever.

I've edited my comment above to clarify.

I think people understand the nihilistic viewpoint but it makes no sense to sacrifice your health while you still have it.

> bright light can never hurt your eyes

Before y'all criticize that statement, keep in mind it's coming from one of the best scientists of the 20th century.

He was talking before lasers. For a purely thermal source to hurt the eyes, it would have to be:

1. insanely hot

2. quite close to the observer

First condition is met by the nuke, but the second one, obviously, is not, unless you're a victim of the explosion.

Scientists, even the best ones, do dumb things all the time.

Source: Am experimental physicist; do dumb things. Sometimes my colleagues do too, even the best ones.

Los Alamos was replete with brilliant people doing dangerously stupid things.


I know. It was not meant as an absolute statement.

As much as a window blocks UV, I wouldn't trust a laser if a high-powered UV laser was aimed through it at my eye.

I have a scar on my retina near the fovea, and I can only see it if I deliberately focus on it.

Are we sure he wasn’t wearing sunglasses too?

Yep, he basically says that he knew the only thing that would damage his eyes would be UV-B, so he just went for it. Long time since I read the book but that's what I remember.

> Feynman knew this and claims to be

I don't get this type of thinking. Unless he thought it would be worse to wear the googles what is to be gained by doing something like wearing goggles (in that situation) just in case you were wrong? Why not reduce the chance of harm as much as you can?

Because he was a curious man and wanted to see every detail?

I think this also has to be considered in the context of an ongoing cataclysmic war encompassing the world where whole cities were being destroyed and of course they were developing a weapon to destroy them faster. Today, WWII is that long ago thing that lasted for a few years and then it was over. Soon the veterans and the Holocaust survivors will all be dead. To anyone then, a lot of things probably didn't seem as important. A lot of people reacted to the atomic bomb once it was public as the impending end of the world, too. So the scientists who knew about it first probably had their attitudes affected.

There's a fine line between genius and madness.

You probably can't see shit with those goggles.

The window didn't block a lot of other high power radiation, and he died from cancer 35 years later, though the connection is not scientifically certain.

He was also smoker. He also lived in Los Alamos during its development where the cancer rates where significantly higher

43 years later (Trinity test was in 1945, he died in 1988).

Sorry, my morning coffee must have been weak.

There's a great Applied Science video on the various light absorption properties for various materials here: https://www.youtube.com/watch?v=vwsHRrDYu5o

So in case anyone just panicked thinking “Wait, so do my car and office windows block cancer producing UV or not??”, this is what I found on cancercouncil.com.au (first google result):

- UVA penetrates deeply into the skin (the dermis) causing genetic damage to cells, photo-ageing (wrinkling, blotchiness etc) and immune-suppression.

- UVB penetrates into the epidermis (top layer of the skin) causing damage to the cells. UVB is responsible for sunburn – a significant risk factor for skin cancer, especially melanoma.

Which contrary to what I knew, links melanoma to sunburn, not DNA damage.

A good example of what UVA does would be the famous trucker with sun damage to one side of his face-


Here's an archive for those getting Oath'd


Well this has made me reconsider my lack of use of sun screen. Thanks for sharing.

I'm stuck between a rock and a hard place because this article makes a lot of sense.


I think I'm just going to use daily sunscreen on my face only.

Melanoma is definitely due to DNA damage; somatic mutation is the principal cause of all cancer. In this case the cause is either direct damage or damage by free radical byproducts created by UV. UV causes a kind of mutation in DNA called a pyrimidine dimer, where two adjacent bases mutate at once. By far the most common mutation in melanoma (reponsible for 50% of cases) is a CC to TT mutation at position 600 of the gene BRAF.

The UV damages the DNA. That step is usually required to produce melanoma cancer. The sunburn causes the deeper cells with damaged DNA to multiply in order to replace the damaged cells.

A single quiescent skin cell with precancerous DNA can be cleaned up by the immune system. A precancerous cell that has multiplied itself to cover a patch of sunburn, activating some of the genes for rapid growth, is much harder to clean up.

Well, when you get sunburn i.e. high UVB exposure, you get high UVA exposure, too. My understanding is, that UVA radiation causes cancer.

But I would like to see some clarification on this topic, too.

UVB causes melanoma, that is also a form of cancer. So typical glass would prevent sunburn and melanomas from forming but not the deep genetic and tissue damage that UVA causes. It is not a bad idea to apply SPF moisturizer before going out if you plan to spend anytime with the sun shining on you.

UVA causes DNA damage (and potentially cancer) indirectly via oxidation.

From what I read UVB melanoma is an "easy" type of cancer.

> So in case anyone just panicked thinking “Wait, so do my car and office windows block cancer producing UV or not??”

I just figured automotive glass doesn't block UV (or at least all of it) since window tinting places always advertise UV blocking as a feature of their films. Cynically I know it could be just empty marketing, but it didn't seem like it.

Of course, ordinary light, while still less energetic, penetrates still more deeply into skin, and it, too causes DNA damage. In situ DNA is damaged by light absorbed by less transparent molecules it is near.

Why are you assuming there isn’t DNA damage when sunburned?

Not that there's no damage, but that sunburned skin is top layer skin that is constantly shedding so won't accumulate damage for decades

Only the most burnt skin is shed. The UV light penetrates further layers.

Quartz glass is transparent to the UV range, so it's not so much that we don't have the technology, it's just way more expensive than regular glass.

Sapphire's also transparent down to far ultraviolet (150nm). Not sure about ALON.

Replying to self (because the edit window has gone): ALON apparently goes down to 200nm, so it's transparent to UVB (280-315)

Sapphire is an incredibly trivial compound, aluminum oxide.

The problem is, its melting point is huge. To make artificial sapphire you have to melt the stuff at very high temperature and let it drop and collect onto a ceramic base or something. And then you cut, grind and polish it into shape, which is not easy either because it's an extremely hard material.

The challenges to making a large flat plate of AlOx would be huge.

Nikon released a lens in 1984 that offered transmission and correction from UV to IR -- from ultraviolet, through visible light, to infrared (near IR, not heat).


This product was originally announced in 1984 as the Nikon 105mm f/4.5 UV-Micro-Nikkor, and from September 1985 it was marketed as the Nikon UV-Nikkor, then the lens sold then for $2,200.00 USD, then about half the cost of a full sized car.

Mildly amusing related aside from this. Because of this, glass is completely opaque in the UV spectrum. Looking at the world in UV [1] is quite interesting! Such a reminder that how and what we experience of the world is so largely a product of our physiological composition. What is perfectly transparent to us would be a great hiding place from the perspective of something that only saw in UV.

[1] - https://www.youtube.com/watch?v=V9K6gjR07Po

Other comments say glass does not block UVA

My grandfather, who was an ophthalmologist with a passion for inventing, has shown me schematics for this kind of glass. His idea was that you could put it in places that are sunny but not warm (like a mountain hotel) to allow for indoor sunbathing.

We always make fun of him for this idea as it's one of his strangest. I don't think he ever finished filing the patent.

I mean this as politely as possible: why would you make fun of someone developing in an unusual idea?

And as a follow-up question, what are you doing in HN?

I don't think I need to explain teasing a family member in terms of the HN worldview.

> So it seems hard to create glass that doesn't block UVB.

Physics aside, why would you want to do that in the first place? UVB is the chief cause of skin reddening and sunburn and plays a key role in the development of skin cancer and a contributory role in tanning and photoaging. [1]

Just for that little benefit of triggering Vitamin D synthesis is not worth the increased risk of skin cancer IMO. And the author lays out the alternative there too: "Those concerned about low vitamin D levels can get more of the vitamin through foods. "

[1]: https://www.skincancer.org/prevention/uva-and-uvb

There is an alternative view that regular sun exposure is beneficial, and that many of the health benefits linked to vitamin D are actually just using vitamin D as a proxy for sun exposure. If this is the case, it's plausible that allowing for more UVB exposure indoors would be a net benefit.

Previous HN discussion: https://news.ycombinator.com/item?id=18890475

I don't doubt that sun exposure is a contributing factor to skin cancer, but it just does not make sense that skin cancer rates have shot up over the past 100 years, while at the same time people spend less and less time outside.

IMO, there's probably some other causal factor(s), and reducing sunlight exposure is not the solution.

Sunlight exposure is important for health, not just for Vitamin D (which others have pointed out, may just be a proxy for some other factor of sun exposure). It's important for regulating circadian rhythm, as well as preventing myopia in childhood.

If you take a dive on PubMed, you'll see that indeed, sunlight exposure appears to be inversely correlated with all-cause mortality.

Why? It is not known, but even when controlling for physical exercise, Vitamin D status, and other factors, the correlation still holds. Some authors suggest other chemicals produced by sunlight, not only Vitamin F, might be involved.

(correction to above, I meant Vitamin D, not F, of course).

> Physics aside, why would you want to do that in the first place?

I worked on a product that had a UV sensor. It needed to be protected.

Sourcing glass that didn't block UVB, that could be used in a mass market product, at cost, integrated into a manufacturing line, was a bit of a challenge. The mechanical engineering team eventually got a hold of some. For awhile, there were weekly status updates of "got another manufacturing sample, spec sheet wasn't quite honest, it blocks some UVB."

Depends for some skin conditions its better to have timed exposure via UVB therapy - I have had this in the past.

The answer to all such questions is - something related to energy levels of electrons in that material. If there's a resonance somewhere, photons at that energy get absorbed.

> So it seems hard to create glass that doesn't block UVB.

Ok, so what is the glass in tanning-booths made of? Or the glass of UVB fluorescent lamps?


Soda-lime glass transmits pretty much all UV ranges and is readily manufactured (it is used often in germicidal lamps.)

You can coat it - sunglasses are, for example. The coating can be invisible to the naked eye too, I think.

This is one of those situations where I think government intervention is needed. I bet the long-term benefits of coating glass like this are very real - both for society and individually (especially in professions that involve a lot of driving time). However, the short-term economic incentives work against it - there is probably a strong first-move disadvantage. Also, what is the economic benefit to a landlord to have UV-proofed glass for their tenants?

But if government were to implement a policy of requiring glass in cars and buildings to be coated like that? That levels the playing field. I doubt it is going to happen any time soon though.

But of we were ever going to to do that, I know for a fact that are also coatings with reflective layers (invisible to us) that tell birds that the glass is there, which would also save a lot of wildlife.

I think you're inverting what parent is saying. Glass by nature seems to block UVB.

Ah, right. I somehow thought GP suggested near the end that it seems to be hard to fabricate glass that blocks UVA, and answered the question of how to deal with that.

How does coating it prevent the glass itself absorbing UVB?

As Waterluvian pointed out, I misread GP and explained how we could make glass block UVA as well.

Ah, yes the classic "government intervention to attack a misunderstood problem with a solution that won't work".

Ah yes, the classic "I just assert that governments can only intervene with wrong solutions, without in any way engaging with the topic at hand and actually arguing why it is a wrong solution."

Well it’s a wrong solution since glass already filters it. Seems a bit premature to salivate over regulation for something that isn’t a problem.

Did you read the other comments? I misread GP and the coating I talked about is for UVA radiation.

> Those concerned about low vitamin D levels can get more of the vitamin through foods.

As someone who had a number of health issues whose underlying cause was a vitamin D deficiency I do not agree.

There is no substitute for light. Supplementing with D3 had very limited effect. Using a vitamin d lamp however was a world changer within days.

Was your supplement dosage enough though? In the order of 10000 IU per day?

The problem with vitamin D was that up until about a year ago, official recommendations in many countries were mistakenly low (500-1000 IUs), which as it turned out, was not enough for many people. It was even hard to find proper pills that has high enough dosages, because when you got to your local farmacist which was going by the official recommendations, all they had were 200-500 IU pills, because they were not expecting that anyone would need more. So as an average citizen who does not do their research properly, if they just went into a farmacist and took the first Vitamin D supplement they saw, the chances were that they were getting one which had basically no effect.

When the dosage is right, many people experience positive effects and dormant Vitamin D levels really do go up. The sun is not required.

The problem with Vit D3 supplement is that you don’t absorb most of it. It is well known, than the bioavailability of the supplements is not the same and that even the molecule itself is not the same as the one your organism produces.

Also, the science is starting to question the supplementation. It’s too early to tell, but one hypothesis is that it is a biomarker at the end of a pathway and not at the beginning of it, i.e. as a consequence of a proper diet and sunlight, and not a cause of a healthy system.

So the vitamin D might be there due to a healthy system instead of the system being healthy due to vitamin D.

An analogy would be the analysis of car exhaust, finding certain levels of CO2, and trying to fix cars with "bad exhaust" by throwing more CO2 into the intake (except maybe this would even have a negative effect by hindering combustion).

> An analogy would be the analysis of car exhaust, finding certain levels of CO2, and trying to fix cars with "bad exhaust" by throwing more CO2 into the intake (except maybe this would even have a negative effect by hindering combustion).

This is an hilarious (and fitting) analogy for nutrition sciences.

There was a classic TV ad by an oil company that said that CO2 is great because it is plant food. It's still an argument used by folks who oppose CO2 controls.

> It is well known, than the bioavailability of the supplements is not the same and that even the molecule itself is not the same as the one your organism produces.

Reputed and trustworthy citations from scientific sources required, please.

Every cholecalciferol molecule is the same. This is chemistry. Chemicals that are not the same cannot have the same chemical name. Every animal (without a genetic defect specific to the precursor chemicals) produces the same 7-dehydrocholesterol molecules, and every 7-dehydrocholesterol will, under UVB light, convert to cholecalciferol.

Industrial production of vitamin D3 irradiates the 7-dehydrocholesterol extracted from sheep's lanolin with UVB light.

There is some question as to whether ergocalciferol--a chemical mainly found in fungi that produce ergosterol and have been exposed to UVB light--is biologically equivalent to cholecalciferol in humans. It can alleviate vitamin D deficiency symptoms, but it is not known with certainty whether it can produce a sufficiency. As far as I am aware, the known cases of hypervitaminosis D have resulted from ergocalciferol supplementation, rather than from cholecalciferol.

If you are supplementing with vitamin D3, the chemical you are consuming is identical to that produced in your skin under UVB irradiation. There is no evidence whatsoever that it is destroyed in or poorly absorbed by the human digestive system. If you swallow 15000 IU of vitamin D3, that is the equivalent of standing shirtless in temperate midday sun for 15 minutes, after which time you will achieve no further benefit until some time has been spent absorbing the cholecalciferol and replenishing the 7-dehydrocholesterol in your skin.

It is poorly known, that if you have to preface a statement with "it is well known", what follows is less likely to be "known" than "unattributably rumored".

No it’s not required. This is a discussion board not a thesis paper review board. Do your own googling. If he or she is wrong then call bullshit.

IMO "Reputed and trustworthy citations from scientific sources required, please." is just a more elegant way of calling bullshit

It's an elegant way of covering noise with more noise.

It is required. Just claiming something is well-known to counter someone’s suggestion without providing any evidence isn’t very productive.

No other suggestion was offered in the post I am referring to, just a "sources pl0x" ask. Here is the simplest counter example I can think of.

"Gravity is real."

"Reputed and trustworthy citations from scientific sources required, please."

You can get less and less ridiculous from here ad nauseam, but the point is made.

"It is well known" is a weasel word, and hence requires more substantiation when asked. If one has to rely on Googling on these matters, one can find so many contradictory views. So I wanted to know what reputed sources the GP was relying on to use "It is well known" for that claim.

how about just search hacker news? https://www.npr.org/sections/health-shots/2018/11/10/6665455...


And those studies saying otherwise have been backed by a lot of questionable money: https://www.nytimes.com/2018/08/18/business/vitamin-d-michae...

Oh by the way sunscreen is terrible, it doesn't have a proven link to reducing cancer and it destroys reefs so do yourself a favor and get more sun without all the slimy goop so you can feel better AND save the planet!

Pairing K2, or consuming vegetables high in vitamin K, helps with this. Personally I both consume a supplement and use a SAD light.

Do you have a source for the 10000 IU per day guideline? If that's D3, that's 25 times to "recommended" amount, well above what is considered safe for long-term use. Now, I realize that our understanding of these things are in a state of (often violent) flux, but I would like to know who's recommended such a high amount. The problem with Vitamin D is that it is fat-soluble, not water-soluble, so your body doesn't expel the excess very quickly and it builds up. Too much can be harmful, particularly to your bones and kidneys[1].

[1] https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-h...

> well above what is considered safe for long-term use.

The Mayo clinic article says:

> Taking 60,000 international units (IU) a day of vitamin D for several months has been shown to cause toxicity.

So 10,000, while it's well above the "recommended" dosage, is nowhere near the toxic level. Although when I was looking around the toxic level was 20,000, still, I've seen no guidance regarding Vitamin D that suggests 10,000 IUs/day can be toxic. (Especially if your BMI is over 25, and you're not getting much sunlight.)

Mayo clinic article concerns excessive supplementation, isolated on vitamin D, specifically.

A hypothesis exists that increasing vitamin K consumption in proportion to the vitamin D, and restricting calcium intake, would eliminate the main symptoms of excessive vitamin D supplementation. Nonhuman animal experimentation confirms, but it has not been tested in humans (likely due to the obvious ethical concerns).

Vitamin D, vitamin K, and calcium are all related.

I have seen guidance specifically for vitamin D2 (ergocalciferol), indicating that adverse symptoms may be observed at lower levels of supplementation than for vitamin D3 (cholecalciferol), but it was quite some time ago, and I don't know if the claim was confirmed or refuted scientifically.

Remember that 60,000 was chosen so that toxicity could be very reliably demonstrated. It does not mean that lower doses are not also toxic.

I'm always worried about how easy it would be for manufacturers to accidentally put more in a pill than the label says.

10,000 IU is only 1.25 mg, and vitamins aren't well regulated. It's not like you'd notice if your supplement contained 100,000 IU.

That happens all the time. Please check https://labdoor.com/ before buying any unregulated drug.

Oh dammit! I wish I had seen this before I went to the drug store...

USP and other certifications are supposed to address this, but the onus is on the consumer to seek out the certification label.


Others include NSF, UL, and consumerlab


There's still the chance that a manufacturing mistake could result in bad dosage but that applies to all products including medicine.

Vitamin D is particularly worrisome to me because a few milligrams is the difference between therapeutic and toxic.

... and in fact it has happened. With drops for infants that had a 75 times too high concentration:


I know you have faith that taking large doses of vitamin d isn't dangerous, but there is very little evidence supporting its value. We all have to make serious decisions every day without scientific support, so I don't begrudge you the right to do what you believe is best for you. But don't you think it's a little irresponsible to try to convince people that this belief of yours is actually effective? AFICT, there's as good a change that your advice will take ten years off of a life as it has of improving life. And you want to push this on others?

Mark Hyman made post on it(he is Hillary Clinton’s doctor): https://drhyman.com/blog/2010/08/24/vitamin-d-why-you-are-pr...

That's a good read. He says you can go high (10000 IU/day) for 6-10 months, under doctor's supervision, then cut back down 2000-4000/day. This also makes sense from the perspective that it's fat-soluble, so you should be able to "fill up the tank" as he puts it.

Thankfully it was posted to HN so I could find it. Google search has a truly become useless for this stuff. It's early in the morning, but I think I'm reading the abstract right. [1]

1. https://www.ncbi.nlm.nih.gov/m/pubmed/28768407/

Try google scholar next time instead of regular google search.

To add some anecdotal info, those numbers are much more closer to my own personal experience. I've been experimenting with various dosages, with regular blood tests by a doctor, for a few years now. Currently I've setteled at 4000 IU/day to stay at 75 nmol/L, which is the lower end of what is considered normal.

Excellent! Thank you!

I would be very careful with liposoluble vitamines, they can aggregate in your fat tissue and cause toxic effects

It was 6000+

Was it gelcaps or dry tablets? Vitamin D is fat-soluble so much better absorbed in gelcap format (and taken with a meal).

Personally, I've been taking 5000 IUs/day and recently started stepping that closer to 10,000 IUs. I use the liquid drops which are in oil, and I always try to take them with some sort of meal. The liquid is a lot cheaper and seems like the ideal way to absorb it to me.

This is in cloudy wintertime Seattle. In sunny times it may be completely unnecessary.

Just another anecdote, a friend of mine with Lyme Disease has serious problems absorbing vitamin D (and other nutrients) via food, his doctor has him on 10K per day.

If I recall correctly, such a treatment is not yet evidence based, though clinical trials are ongoing.

That is interesting. I had read that 500 was ineffective but did not know that 10000 was effective. If you've done the research what is the most reliable source you found ?

taking vitamin D at such a high dose can give you health problems such as kidney stones. When I took 5000 IUs for a period of time I started getting painful kidneys just from the urinary effects.

Now I try to get my vitamin D through more normal sources by eating lots of UV-exposed mushrooms, salmon, and sardines. Plus side is these foods are all quite healthy even without the vitamin D

I didn't have any problems getting 20k IU in the UK had to get it prescribed

There is research implying that levels of vitamin D are only an indicator of good health, and does not cause it (i.e. correlation instead of causation): https://www.outsideonline.com/2380751/sunscreen-sun-exposure...

OP would still likely be fixing their problem though, right? That article says it is the sun exposure itself that has a positive effect, and vitamin D is the byproduct.

To be clear, that's a really useful article, just want to clarify that your intent is indeed to explain why vitamin D wouldn't work but a UVB lamp would.

Another possibility: higher vitamin D levels are associated with health because people who are outside more might be getting more exercise, and it's really the exercise that is doing it.

It's hard to disentangle all these things.


A related article that was on here recently-


Vitamin D is something we can measure and often serves as an indicator, but large scale tests have shown limited effectiveness of supplements at resolving the issues a Vitamin D deficiency causes. e.g. We increase blood Vitamin D, but there are unknown correlative mechanisms that we aren't substituting.

Good, straightforward advice from the NHS here. https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-... - just about the only vitamin that they recommend supplementing orally for the general population, at least during the winter months.

The evidence on this seems to be changing frequently, not unlike the evidence on whether taking vitamin supplements is a good idea (https://www.health.harvard.edu/staying-healthy/should-you-ge...). Generally speaking, the latest science on nutrition seems to be more subject to later revision, or even reversal, than the latest science on, say, physics or geology.

So, while we wait (perhaps decades) for nutrition to become a more reliable science, I like to consider it from an evolutionary angle. That which is very dissimilar to what my ancestors experienced, like plentiful sugar or a sedentary lifestyle, is more likely to be bad for my health.

Exposure to the sun for hours a day, including the UV part, was part of our ancestors' lifestyle from the beginnings of our species, until a few decades ago. Now it is possible that this is the exception, and we should keep ourselves shielded from UV at all times even though it was what we evolved for. But...

- we don't now much about our skin microbiome, but we know we have one and it matters, and it seems unlikely that removing all UV would not impact that - we know there's an impact on vitamin D levels, but the details of that are still unknown - we know that eczema, psoriasis, and other skin conditions have been rising in recent decades, since the "always wear sunscreen" advice became common

Now, many that's all a coincidence, and UV is bad for us, and lack of UV is good for us, regardless of the fact that it's the environment we evolved for. But I'm skeptical.

There's another important factor to consider, and that's how we expose ourselves to UV. Our ancestors used to be outside most of the day, allowing skin pigmentation to adapt to the regional and seasonal UV levels. Until agriculture came along fairly recently we also lived mostly in the shade of the forest and not in direct sunlight.

Compare that to today, where UV exposure mostly means exposing the skin to massive bursts of UV for short times, at best in an effort to build skin pigmentation that isn't sufficient. That's completely different and much more damaging, leading to the general feeling that any UV is bad.

We are also a lot cleaner. We remove dirt and dead skin, whereas our ancestors left it there and it may have acted as a protective shield from UV.

I think our ancestors lived in the full sun of the African savannah a lot more than the forest, and even in northern Europe, hunter gatherers were killing meat-on-the-hoof (mammoth, wild horse, etc.) so they were running about in the open a lot.

However, the change in exposure is surely true. I'm just not at all convinced that complete shielding from UV is a better choice than occasional UV.

Until recently, children would run around outside a lot during the summer, even in urban environments, and especially in suburban or rural ones.

Be careful of the natural fallacy. Life expectancy was much lower a long time ago, and causes of death from poor health were not recorded very accurately.

Choosing the natural over the artificial is a reasonable default where the science is uncertain. But just remember that science has eliminated an awful lot of problems.

Also remember that natural experiences aren't always a la carte. Picking natural foods from disperate regions might be very unnatural, as is getting natural UV light after taking a shower.

Certainly, many natural things are not good. However, the idea that a complete absence of natural light (which includes UV) is good, is suspect. It reminds one of the idea, in the early 20th century, that getting rid of all bacteria was good. It turns out that there are way more kinds of bacteria than we know, and an excess of antibiotics and disinfectants is almost certainly a big part of why we have ever-escalating rates of severe allergies and auto-immune disorders.

Not that we would wish to have a complete absence of antibiotics. But, the attitude of "you have a virus, so take this antibiotic just in case there's also a bacteria", sounds a lot like "block all UV light from hitting your skin, at all times". I am skeptical.

I mostly agree. I'm just saying that you might want to stop using soap as well ;-)

Using soap has a big effect on how the UV light hits your skin, the damage it might cause, and the benefits that it might have. Of course this is all speculation on my part, but I am just warning of the idea of picking one natural thing at a time -- natural things go together.

Maybe instead of sunscreen, we should be using mudpacks. :) I think it might hurt my chances of getting employed, unless I worked only remotely. Also, my wife would have words.

However, anecdotally, the "mud beggars" at modern Renaissance Faires are said to have healthy skin. It could be a confusion of cause and effect, though.

Do consider that your ancestors developed in a particular latitude in a particular climate. E.g. anglo-saxons developed in northern latitudes & have pale skin. The fact that they spent many hours a day in the sun unprotected does not mean that an anglo-saxon would be advised to do the same in Phoenix.

Absolutely. I do think that the typical amount of sun which a descendant of northern Europeans, now living in Phoenix, gets is probably still not as much as their ancestors got, simply because the amount of time spent outside is so much less. But your point is well taken.

Also, most descriptions of our ancestors show them to have been far more hairy than we are.

I think there's a business opportunity for someone to make light bulbs which emit a little UVB. Not enough to cause sunburn or raise skin cancer risk, just enough to keep our vitamin D levels up. That way you could just stick it in a light fixture and go about your normal life. Is such a light practical to build?

There are plenty of tanning (UVB) lights at all different wattages available for purchase.

I think the problem is the visible light output tends to be harsh, and the bulbs are highly inefficient, they are exensive, and they don’t last very long either.

So there would be a lot of problems to solve, not the least of which is the cultural issue you raise of scaremongering around UVB exposure in the first place.

There is one FDA approved vitamin D lamp made by Sperti.com. Costs about $400, has a 5 minute timer, instructions say to use it once every other day, the UVB spectrum of the lamps is tailored to Vitamin D production. I have one, it works better than pills.

For those curious about the lamp, this is the link: https://www.sperti.com/product/sperti-vitamin-d-light-box

They used to sell these (as regular-size fluorescent tubes) decades ago.

Or just replace window glass with OP4 plastic. Not cheap.

I try to use a tanning bed a couple times a week in winter.

I think we need to update GTL: Golang, tan, laundry.

is that safe?

Tanning beds are banned in some countries with high skin cancer rates for good reason. It is a lottery and you are accumulating risk with exposure. I strongly suspect (without any real evidence) that there are a number of beneficial health effects to moderate UV exposure that can improve quality of life for some people but the experience with fair skinned populations in high UV parts of the world has been overwhelmingly negative. The public health advice is basically written in blood on this topic and so I would view people and sites promoting alternative views with an appropriate amount of skepticism for now.

Not at all.

I agree that food doesn’t have enough vitamin D, but supplements really made the difference for me. Just get the right dosage (which is probably higher that you think).

Were you measuring in observed serum vitamin D levels, or just in subjective wellbeing? Light therapy fixes Seasonal Affective Disorder but doesn’t necessarily do so by increasing vitamin D production.

Could I ask what lamp you chose and how long you spend in front of it? I take a fairly high dose of D3 and I'd be curious to try artificial light. Thanks!

Androv 3000 uv-b lamp for vitamin d.

I never use it for more than 1 minute and I alternate between facing away and towards it. For the first month I used it every day, now more like every other day or every two days.

Tangentially related, I got an androv full-spectrum lamp several years ago for some color work. It was one of the few true "full spectrum" bulbs you can get for cheap which are decently balanced without resorting to use a combination of bulbs. And yes, we tested it with a spectrometer.

Most other full-spectrum lamps I tried at the time on amazon didn't get even close.

If you never tried, working with these lamps is weird: turning it on in the evening or night by mistake _really_ wakes you up.

So yeah, I hope Androv kept up with the quality.

Maybe I should replace my daylight lamp with this, to counter the winter depression. (Norwegian).

Was that the desklamp? Do you happen to know a more specific model of such a lamp?

Yes, to be specific the 42W model. I did the order in 2010, to be specific, so some time has passed since I did the tests.

>... now more like every other day or every two days.

Can I ask the difference? I'm assuming a typo, but haven't experienced sun shortage for at least six years, so I'm not sure on boom / bust cycle potential with these things.

I dont understand the question. The difference between using every other day or every two days?

Using every other day = use one day, then not use it the day after.

Using once every two days = use one day, then not use it the day after.

Perhaps you meant "once every three days", i.e. use it one day, then not use it for two days?

Yes I meant every three days

Are these lamps safe?

A few applications à 15 min with a mercury high pressure lamp with a good reflector and you look like you went to the Caribbean for holidays. Maybe add a filter for UV-C, but there is no ionizing radiation. Just show any lamp in question to your favorite dermatologist. If he seems unhappy, you have the chosen the right lamp.

Jokes aside, skin is very photo-active and I do think lamps can help greatly against these kind deficiencies.

Most lamps emit a line spectrum though, so it is not like real sunlight. I wonder if that is the reason people going to solaria often seem to have weird skin tones. Ask a dermatologist and don't forget eye protection.

Apart from that it has the same side effects as sun exposure. Too much leads to skin aging, sunburn, cancer, etc.

Those side effects can be mitigated or at least reduced by adding extra infrared or red light. Eg sunburns are prevented or greatly reduced by treating with near infrared either before or after UV exposure.

Could you explain please how/why IR helps with sunburn? :o

There are some interesting papers turning up if you google „pubmed infrared sunburn“. One of these: https://link.springer.com/article/10.1007/BF00373376

Do you use it only in winter, or year round?

Year round

A related anecdote:

I dabbled in light therapy and found the first lamp I tried [1] very effective. However I have also started receiving comments from my colleagues about my nice new facial tan, in the dead of winter. I freaked out because the lamp was in my field of view 30 minutes per day every day without any eye protection, and sent the lamp back to where I bought it. Subsequently I have tried three different LED-based lamps and they seem to have no effect. I have carefully measured the light output and placed myself at proper distance to get the requisite 10,000 lux in all cases. No dice.

Here's the kicker - that lamp [1] appears to be the one used in some of the light therapy research (that's why I got it). It is entirely possible that much of light-therapy research was contaminated by badly designed lamps. There is no FDA certification for any of this as far as I know.

[1] Carex Day-Light Classic Plus Bright Light Therapy Lamp. Supposedly UV-filtered.

How is a Vitamin D lamp supposed to promote the creation of Vitamin D without UV?

It only blocks most of the UV. The lamp itself is blasting a very intense amount of light, so that the circadian-sensitive mechanisms in your eyes are fooled into thinking you're outside on a bright summer day. The vitamin D is secondary to the main function of the lamp, which is to be incredibly bright in comparison to most indoor lights. The light-therapy lamp must be aimed at the eyes (even for blind people!). It just doesn't work as well if you can't see it directly. You would have to pump even more light into the room to get the same amount reflected off of other surfaces.

Also, the lamp could be putting out UVA and not much UVB, so it could tan without producing much vitamin D.

For just the vitamin D, I'd get a "5.0" UVB lamp in a bare-bulb fixture, designed and sold for indoor avian and reptile pets. Aim at arms and hands, and away from the eyes. They're about $15 per bulb, and should be replaced every 6 months, as the UVB output degrades over time. Afterward, they work perfectly fine as compact fluorescents, behind glass or under lampshades, for several more months, albeit shaped inconveniently for some fixtures.

A "10.0" bulb is for desert-species pets. The UV output is too high for the overall lamp brightness, and may damage your eyesight, as human pupils don't constrict enough. I suppose you could wear sunglasses, but that seems counterproductive to just buying a lower-UV lamp.

These "light therapy" lamps don't. They just supposedly improve mood from the exposure to bright light itself and don't claim to produce vitamin D.

LED lamps do not emit any UV unless you specifically order ones that do. Fluorescent lamps put out more UV by comparison!

Do LED lamps not produce light via blackbody radiation? If they do then they must produce at least some UV

> Do LED lamps not produce light via blackbody radiation?

I'm pretty sure the answer to that is that they do not.

No, they use electroluminescence, not incandescence.

>was a world changer within days

Question, what were your health issues and what changes did you see that quickly?

Magnesium deficiency and a general mineral imbalance that resulted in severe insomnia. I also developed a bunch of food intolerances that were getting ever worse.

I was supplementing with a lot of magnesium. Sleep returned very quickly, my need for supplementing magnesium also dropped in days.

How were you measuring magnesium need, blood tests?

After reading the "Big Vitamin D Mistake" article on HN in 2017 I also started experimenting with larger doses of Vitamin D and can attest to life-changing effects.

It has been like a permanent +5 to constitution; I am now almost through my second winter without getting sick, something inconceivable for me as a kid growing up with asthma and a whole range of puffers, and always prone to debilitating sinus infections that told hold in January and never really let up sometime around April.

That is amazing. What kind of vitamin D in at what levels did you settle on?

I initially started with 1000 IU of Vitamin D3, Costco brand, and eventually settled on 5000 as I noticed improvements in energy level as I took more.

I am at 43 latitude so I only start taking it in mid-November and start weening myself off it in late March (you never really know if/when spring will happen up here in Toronto :)

Thank you,

Couldn't it be that this depends on the person? Maybe others can use the vitamin D present in food? I.e. part of your deficit might be because your body somehow cannot process the D in food? Just guessing here..

Typically there isn't enough vitamin D in food to match anybody's recommended intake, unless you eat rather large amounts of seafood.

I have no idea

Narrowband uvb is a very effective treatment for some skin conditions. The mechanism is totally different to vitamin D and oral supplementation basically has no effect. UV exposure is a significant health risk in some parts of the world and the public information campaigns to reduce exposure seem well justified. But I wonder if there isn't a case for a narrowband uvb sunscreen that only lets those dangerous but highly effective dna mutating rays through along with some sort of cheap and reliable dosimetry.

I live in Southern California and it's common for people to have these effects when moving here from darker locales and spending time outside. My severe insomnia almost vanished after coming here.

And here I was thinking I was OK because I drink vitamin D supplemented whole milk.

> Using a vitamin d lamp however was a world changer within days

Which one do you recommend?

I mentioned the model in another reply. Androv 3000

Those concerned about low vitamin D levels can get more of the vitamin through foods.

Supplementing with D3 had very limited effect.

Non sequitur. Pills are not food.

Which lamp do you use?

It's like the old Klingon proverb: People who live in glass houses should upgrade to transparent aluminum.

I have checked and according to graphs I have found both sapphire glass and AlON both do indeed transmit UVB.

Ah good, I need to replace the windows in my house, that'll be a great upgrade.

  Checks prices
It'll only cost me ~$240,000 for a single room!

It's not about us, UV light destroys almost all types of plastic materials, and affects color of wood and fabrics - so without glass UV filtering our furniture, floors and pretty much everything else inside our houses and cars that is exposed to sunlight would last a lot shorter.

I wonder why Vitamin D level blood test is unusually expensive than other blood test . It doesn't even get covered by CBP ( complete blood picture )


UVB is required for health and carcinogenic?

It's been 500 years since Paracelsus supposedly said something along the lines of: "All things are poison, and nothing is without poison, the dosage alone makes it so a thing is not a poison."


Welcome to unintelligent design.

Evolution will happily incorporate an abundant resource into one biological process even if it is damaging to another. Heck, even if it is damaging to the same process it is being incorporated into.

The heat we produce in oil motors is what makes them work, but it's also what destroys many components. I don't pretend life has been designed or not, but it doesn't look stupid to me: in a relative world, everything is a compromise.

It's far worse than the trade-offs required by physics.

Evolution is short-sighted in a way that is hard to overstate. It exclusively cares about the current environment, it can only consider alternatives when they have actually been implemented, it can't look-ahead to see if a chain of changes is really desirable, and it can't even look-behind to determine if a previous design is better-suited to the current environment.

A better analogy to the way evolution operates using an engine would be: imagine that you first develop an engine that runs on a pure fuel, but then for a long span of time you can only get an inferior, highly contaminated fuel that produces a corrosive acid while it burns that slowly destroys the engine from the inside. You make a few tweaks to mitigate (but not stop) the damage from the acidic residue, but then you discover that by adding an additional afterburner with a special additive, you can get an extra 8% output from the engine. But then later when the pure fuel is available again, you discover that running the engine with the afterburner on a pure fuel will make it explode in short order. It's too late to redesign the engine without the afterburner -- most of the engines currently in existence suffer from the problem -- but it's pretty easy to re-contaminate the pure fuel so that it continues to produce the acidic residue that is both destroying the engines and expected by the afterburners. Meanwhile, most people still don't want to buy a pure-fuel engine without the afterburners since they have a lower output, and you really don't need most engines to last forever anyway.

That's the sort of bullshit you deal with in an evolved system.

> Evolution is short-sighted in a way that is hard to overstate. It exclusively cares about the current environment

This isn't quite accurate; while some evolutionary pressures are indeed exclusively short-term, not all are.

For instance, ability of eukaryotes to have multiple alleles of individual genes combined with sexual reproduction allow populations to maintain a large diversity of alleles and genes, which have the effect of allowing large-scale "split testing" and also "alternatives" for different current environments that may appear over time.

What else could you hope for?

It seems like you'd like for evolution to have some model, so it can test old designs in the current environment, and simulate forward the current design into future environments, without needing to burn an organism and time on the test. But how could that be possible?

By evolving intelligence that creates computers and models and does that exact simulation, and then modifies the necessary biology to apply the best scenario. Seems to me we’re well on our way there.

>in a relative world, everything is a compromise.

Modern men call it: "There is no free lunch!"

Well, evolution doesn't care if you die at 50 from sun induced cancer or at 80 from heart failure, as long as you've pumped out offsprings capable of reproduction you succeeded.

Plus nowadays with tech / medical advances evolution doesn't play the same role as 10k years ago. You can be obese, diabetic, lactose intolerant, lose a kidney and a lung and still get kids + your life expectancy will be miles ahead of our ancestors hunting antelopes with spears and pointy stones.

This is a commonly-held misunderstanding! Natural selection doesn't stop acting once you've reproduced.

Characteristics ("traits") which are potentially not helpful for direct reproductive success but have an impact on the success of the group of people you're a part of are conserved through evolution. However, the exact formulation of this idea (known as kin selection or group selection) is still quite controversial [1] among evolutionary biologists.

[1]: https://blog.oup.com/2015/01/kin-group-selection-controversy...

Sure, it depends at which scale you observe it. It's probably impossible to study individual traits vs "group" traits though. As I see it it's one of these problems with so many co-founding variables that we'll never agree (depending on who you listen to: fat is good/bad, carbs are good/bad, sun is good/bad, ad infinitum)

My point was, something can be good at some point (vitamin D production) and turn bad in the long term (increased cancer rate), but being ultimately bad doesn't mean evolution failed.

Yes. Otherwise there would be no reason to live as long as we do.

Maybe the intelligence behind the design was to make something that works, instead of something perfect? Isn't that better, after all? (Also is there even any indication anywhere that a perfect thing is possible at all, whether be by design or a result of random chaotic process?) (again, not saying whether the design might be intelligent or not, just that the argument is not really logical concerning that).

> Welcome to unintelligent design.

Or just designed for another purpose.

This and periods which are unique to humans (I think) are classic examples of evolution hackery.

> unique to humans

It appears not - http://www.bbc.co.uk/earth/story/20150420-why-do-women-have-...

> Apart from humans, most of the other menstruating animals are primates, the group that includes monkeys and apes as well as humans. Most monkeys living in Africa and Asia, such as rhesus macaques, menstruate.

> menstruation also evolved independently in two other groups: some bats and elephant shrews.

Not that any of this disproves the "evolution hackery" suggestion, mind.

Thanks. I was not 100% on it being unique to humans but I did remember it being quite rare in nature.

Similarly, water hydrates and drowns. Moderation is often a necessary principle.

Moderation may not suffice. I'd say Dihydrogen Monoxide is very dangerous given it's a colorless and odorless chemical compound so not always easy to identify for the layman. Yet we can spot it in great quantity in most food despite the fact it's PH is higher than most acids. You can't even wash it off at the sink, the more you do, the more you get in contact with it.

I mean at least UVB, you can protect against with simple glass. But something you find traces in most people's blood is no joke.

We should suppress it completly. Or at least ban it from schools.

See: Oxygen.

Required for us to stay alive, yet ultimately kills us.

What likely happened is, since humans started living on the ground after they left trees, they had enough sunlight exposure; so we evolved sunlight to be a start marker for some important metabolic activities, purely by randomness. It just so happens that too much sunlight exposure causes cancer. But since cancer happens later in life, it wasn't selected against and we just ended up with this weird biochemistry: UVB is necessary for health but it also causes cancer.

Is it required, though? If you don't get it through diet, sure.

water, a building block of life, can kill you

Don't downvote OP, it's a very legitimate question.

Medias tend to represent everything as black and white, and so it's easy to get confused, espacially since people will tell you everything then the contrary depending of the fashion of the day.

It's always nice to have those moments, when you can highlight that reality has nuances. Let's encourage people asking for answers, we don't have enough of them.

And yes, Vitamin D is required, not UVB. You can aquired vitamin D by eating organisms full of it. But the most efficient way is still to get exposed to sunlight. It's partly why some get depressed in the winter.

The sun is not "bad for the skin" any more than a cold water is bad for your health. But stay in it too long and you may die.

> And yes, Vitamin D is required, not UVB. You can aquired vitamin D by eating ...

There is some debate about this now, while sunlight certainly produces vitamin D, that's certainly not all that it does. This article showed up here recently:


Of course, but sunlight is not just UVB. Plus, the spectrum of one component is hardly what define light interraction. The many spectrums + quantity + intensity + the human receiving is a more interesting model.

E.G: I just bought a light to help with the winter blues. It does not provide any UVB, so the method of action is something else.

Guidelines | FAQ | Support | API | Security | Lists | Bookmarklet | Legal | Apply to YC | Contact