Sunlight through glass does not provide Vitamin D

https://www.nytimes.com/2019/02/08/well/live/does-sunlight-through-glass-provide-vitamin-d.html

by bookofjoe • 7 years ago

601 322 7 years ago

nytimes.com

leemailll• 7 years ago

Isn’t this common sense?

dorkwood• 7 years ago

No.

crummy• 7 years ago

Common sense is, if I can see the sun through it unblocked, it must let light through, and light gives me vitamin D, right?

antris• 7 years ago

Who cares if it's common sense? Common sense is a very bad way to make conclusions.

Insanity• 7 years ago

I knew about this - and I think that if you have had a deficiency of Vitamin D your doctor might have told you about it.

But I'd wager to say the majority of the population that didn't consult a doctor due to a deficiency won't know this. (Unless, perhaps, when they studied something in the medical field).

redcalx• 7 years ago

I've occasionally posed this question to people during casual conversation, and I've always received the same answer - 'of course!' (... you make vitamin D behind glass).

It's still not clear to me if there are some types of glass that do allow vitamin D synthesis or not.

jrs235• 7 years ago

From my understanding, UVB is required for vitamin D synthesizing by your body. If the glass blocks UVB then you're out of luck.

TeMPOraL2• 7 years ago

Common sense is a function of individual's level of knowledge. For vast majority of people, "common sense" would dictate answering this question "yes", even though in reality, the answer is "no".

Ensorceled3• 7 years ago

How could the fact that glass blocks UVB but allows UVA and Light be common sense?

turc16563• 7 years ago

I think it's one of those things that should be common sense but we don't generally think about it hard enough. By that I mean everyone probably could figure it out if they just gave it about 30 seconds of thought. I clearly remember the day I learned this back in high school. My physics teacher was discussing the refraction of light in materials like water and glass and the conversation moved into how materials can break up the components of light (like a prism). Another student was trying to make sense of this concept of light breaking down into frequencies and its component parts but still be light after being broken down. Forcing us to think about it ourselves, the teacher asked the class two questions: 1) Have you ever gotten a tan anywhere on your body on a long car drive in the summer? Everyone thought for a moment and answered that they hadn't even gotten so much as a farmer's tan on their arm to which he asked... 2) Why?

This forced us to think about it and realize that the window was doing more than just refraction and was stripping out or absorbing part of the light and even though it appeared as the same light to us, whatever was being removed must have been in the spectrum of light not visible to humans.

So we all intuitively know this, but never stop to actually think about it.

pjc50• 7 years ago

UVB is required for health and carcinogenic?

tomrod• 7 years ago

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

sametmax4• 7 years ago

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.

nkozyra• 7 years ago

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

saalweachter2• 7 years ago

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.

sametmax4• 7 years ago

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.

Erlich_Bachman3• 7 years ago

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).

0xcafecafe2• 7 years ago

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

chooseaname3• 7 years ago

Welcome to unintelligent design.

Or just designed for another purpose.

lm284693• 7 years ago

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.

sametmax4• 7 years ago

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.

iguy3• 7 years ago

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:

https://www.outsideonline.com/2380751/sunscreen-sun-exposure...

whatusername• 7 years ago

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."

https://en.wikipedia.org/wiki/The_dose_makes_the_poison

flavor8• 7 years ago

See: Oxygen.

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

gnulinux2• 7 years ago

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.

trumped• 7 years ago

water, a building block of life, can kill you

rapsey9• 7 years ago

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.

iamben• 7 years ago

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!

rapsey9• 7 years ago

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.

stinos• 7 years ago

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..

rapsey9• 7 years ago

I have no idea

FreeFull• 7 years ago

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

Erlich_Bachman3• 7 years ago

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.

rapsey9• 7 years ago

It was 6000+

wolfi1• 7 years ago

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

dhimes4• 7 years ago

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...

Amygaz• 7 years ago

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.

C1sc0cat2• 7 years ago

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

opportune2• 7 years ago

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

drited• 7 years ago

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 ?

Angostura• 7 years ago

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.

endorphone• 7 years ago

A related article that was on here recently-

https://www.outsideonline.com/2380751/sunscreen-sun-exposure...

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.

gnclmorais• 7 years ago

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).

nradov• 7 years ago

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?

istjohn• 7 years ago

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

zaroth• 7 years ago

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.

Nomentatus3• 7 years ago

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

Nomentatus3• 7 years ago

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

rapjr9• 7 years ago

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.

mtgx• 7 years ago

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

Which one do you recommend?

rapsey9• 7 years ago

I mentioned the model in another reply. Androv 3000

BerislavLopac2• 7 years ago

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...

graeme3• 7 years ago

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.

api• 7 years ago

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.

gerbilly• 7 years ago

Which lamp do you use?

ip263• 7 years ago

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.

TremendousJudge• 7 years ago

was a world changer within days

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

rapsey9• 7 years ago

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.

atomic772• 7 years ago

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.

DenisM2• 7 years ago

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.

MPSimmons• 7 years ago

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

achillesheels• 7 years ago

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

derefr• 7 years ago

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.

rossdavidh5• 7 years ago

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.

wongarsu• 7 years ago

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.

ip263• 7 years ago

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.

jeffdavis3• 7 years ago

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.

bookofjoe• 7 years ago

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

chaoticmass• 7 years ago

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

shirro2• 7 years ago

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.

ourmandave• 7 years ago

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

Meing4im• 7 years ago

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

fastball• 7 years ago

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!

bellerose• 7 years ago

My personal experience with nutrition makes me consider the childhood years as the deciding factor in regards to living healthy without much time or resources allocated towards personal health. There are outliers, such as genetics and parenting will limit a child or not but I can only assume it’s a struggle starting unhealthy in the early to late 20s. All my childhoods friends that were into skateboarding, biking or another intense activity from sun rise to sunset cannot put on weight. Typically have healthy skin unless acne prone and are very coordinated with balancing. The reason this article compelled me to write is because the next generation of parenting is restricting kids from the freedom of outside activities unless a parent is there with the kids. There will be a lot of lacking factors besides vitamin D and it’s terrible to think about. I’ve been a person who has most of my life believed that deterrents should exist against parents who let there kids become unhealthy. It seems we’re heading the opposite direction.

dTal• 7 years ago

Might you be confusing correlation and causality? Whatever caused your childhood friends to be into intense physical sports, might also be the cause of their adulthood health - perhaps a natural inclination to physical activity, or maybe an unusually fast metabolism that gives them lots of energy to burn.

Not to suggest that you're wrong - childhood exercise probably is very important, and is under threat.

interfixus2• 7 years ago

Exactly what I was told as a child, and hence have 'known' for more than fifty years.

telesilla• 7 years ago

Yes, I asked my science teacher this exact question when I was 15 (as I burn easily) and was happily told I couldn't get sunburnt behind glass. So far, experiments have proven this true.

TeMPOraL2• 7 years ago

A similar fact is that photochromic lenses will not work in cars, i.e. when you're looking at the world through the windshield. The photochemistry in them is triggered by UV rays. It's another thing that should be common knowledge, but isn't.

iguy3• 7 years ago

I don't know if this counts, but there's picture of a truck driver which was doing the rounds:

https://www.nejm.org/doi/full/10.1056/NEJMicm1104059

fauigerzigerk• 7 years ago

Unfortunately UVA contributes to skin cancer as well: https://www.skincancer.org/prevention/uva-and-uvb

chooseaname3• 7 years ago

Auto glass must be somehow different, because in Florida, you can surely get "some color" on your skin on a long drive and the sun beating in through the window.

SmellyGeekBoy• 7 years ago

I was told that TV would turn my eyes square as a child, looking forward to having it proved by science so I can smugly announce that I've known all along.

Wait, no, it doesn't work like that.

interfixus2• 7 years ago

No it doesn't. Therefore the quotes around 'known'. Let us split the smugness down the middle.

kuon2• 7 years ago

I agree with the other comments, isn't this common sense and known? I have been told this when I was a kid.

optymizer• 7 years ago

I did not know this, but I also didn't grow up in the US.

vitaflo• 7 years ago

Thought the same thing, I thought this was common knowledge. But I live in the upper midwest where low D levels are common in winter, so perhaps it's just discussed here more.

lm284693• 7 years ago

Common sense is wrong as often that it's right, being told something as a kid doesn't help either since you're less likely to question the source.

kuon2• 7 years ago

Yeah of course, there are many things that are widely believed but are false. But we were told this in a 30 minutes course a doctor was giving, in a campaign the schools were doing to educate us about the danger of the sun. A few other things were told, like that there is no total protection sun cream or that even cream that are marked as water resistant do not resist water. That's when we learned that 1mm of "modern glass" would cut nearly all uv light, while it requires nearly 50 meters of water to block it.

Of course not all that might be true, but as far as I know, it is pretty accurate.

izzydata2• 7 years ago

As I mentioned in another comment I was aware of this fact. I would have been able to tell you as such if someone had asked, but Vitimin D would never have crossed my mind as being an issue.

dragontamer• 7 years ago

The one thing I learned in college was that schools outside of my state are pretty bad with "common sense".

"Common sense" is highly localized. My schools had health studies for sure, but no home economics. I had classmates in college who had home economics, but not very robust health classes.

Any and all combinations of learning exist in the USA alone. Each State is in charge of its own education department. Travel just 2 or 3 states in any direction, and you'll have a grossly different set of skills being taught at the high-school level.

pasta2• 7 years ago

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.

Etheryte• 7 years ago

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.

masklinn2• 7 years ago

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

vanderZwan5• 7 years ago

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.

georgyo• 7 years ago

How does coating it prevent the glass itself absorbing UVB?

Waterluvian• 7 years ago

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

losvedir• 7 years ago

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

spuz• 7 years ago

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

harperlee• 7 years ago

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.

garmaine2• 7 years ago

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

logfromblammo4• 7 years ago

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.

meschi• 7 years ago

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.

astazangasta• 7 years ago

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.

JohnJamesRambo2• 7 years ago

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

https://www.huffingtonpost.ca/2012/06/06/bill-mcelligott-sun...

Nomentatus3• 7 years ago

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.

taneq• 7 years ago

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.

rjf72• 7 years ago

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

hopler4• 7 years ago

Other comments say glass does not block UVA

lightedman• 7 years ago

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

kough• 7 years ago

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.

https://www.sindark.com/2011/02/22/feynman-and-the-trinity-t...

Bartweiss• 7 years ago

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?

BurningFrog2• 7 years ago

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.

gist• 7 years ago

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?

devy• 7 years ago

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

tlals• 7 years ago

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

rhinoceraptor• 7 years ago

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.

C1sc0cat2• 7 years ago

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

com2kid• 7 years ago

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."

habosa2• 7 years ago

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.

tomcam3• 7 years ago

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

amelius• 7 years ago

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?

duskwuff• 7 years ago

Quartz.

Florin_Andrei4• 7 years ago

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.

foobar1962• 7 years ago

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).

http://www.company7.com/nikon/lens/0105f4.5uv.html

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.

SoulMan• 7 years ago

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 )

cryptozeus• 7 years ago

capitalism

ewgoforth• 7 years ago

I've known about glass inherently blocking UV for a long time, but have wondered why do posters, etc. fade in store windows.

syphilis2• 7 years ago

I've noticed plants do poorly behind windows at my office (thick glass, newer glass) despite being South facing (northern hemisphere). At home in a windowsill behind glass from the 60s they thrive.

Anyone had a similar experience? Think it could be because of the office glass?

DenisM2• 7 years ago

Office glass is heat-shielded to reduce AC costs. That's be my guess - lack of IR.

adrianN• 7 years ago

I think it's more likely that they don't like the warm dry air produced by the radiators that are typically installed below the windows. Chlorophyll doesn't absorb much UV.

debacle• 7 years ago

I have a lemon tree that is indoors in full sun. Last summer I put it outdoors for the first time and it has 3-5x more foliage than it has ever had.

ivanhoe• 7 years ago

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.

air7• 7 years ago

tldr: no.

kaitari• 7 years ago

My newborn daughter's pediatrician recently told my wife and I how important it is to sit in front of the window with our daughter, specifically for vitamin D generation via sunlight exposure (as opposed to taking her outside right now because it's very cold/winter). I guess I (and perhaps all parents of winter babies?) should ask about a vitamin D supplement.

thedmstdmstdmst• 7 years ago

You should definitely check out a Vitamin D supplement for your daughter. Where I am from we have reduced sunlight during winter months and it is something all the pediatricians have recommended and asked if we are doing because of the lack of sunlight.

bluntfang3• 7 years ago

or just go outside with your baby. humans are pretty resilient, especially the rubbery little ones and they are really good at telling you when they are uncomfortable.

pricecomstock• 7 years ago

Sunlight does not provide enough UVB for sufficient vitamin D production above a surprisingly low latitude (35N) during the winter months.

https://www.nytimes.com/2018/02/16/well/live/do-i-get-enough...

nicwolff• 7 years ago

Or look for another pediatrician!

viggity• 7 years ago

ignoring the glass - in the winter much of the US is at too high a lattitude to get any UVB, as it bounces off the atmosphere because the angle of attack is too shallow. The sun needs to be at least 50degrees above the horizon for UVB to penetrate the atmosphere. In an iowa winter, even at its apogee the sun is only ever 26deg above the horizon

Dolores12• 7 years ago

How much cold is 'very cold'?

Symmetry• 7 years ago

On the other hand UV tends to lower your folate levels. Populations' skin colors tends to track the latitudes they live in but also the ratio of vitamin D to folate in their diets. That's part of the reason the pre-agrigultural population of Europe with their fish heavy diet had skin colors so much darker than modern Europeans

https://www.bbc.com/news/science-environment-42939192.

chippy• 7 years ago

Worth saying that for fellow British users we won't be able to get any vitamin D from the Sun until mid March. We live at too high a latitude - the sun is too low down in the horizon.

izzydata2• 7 years ago

I was aware of this, but it never crossed my mind that this fact might be causing problems for me.

I realize now just how little sunlight I get. I probably spend less than 5 minutes outside a month as I only go from indoors to indoors by car.

fitzroy3• 7 years ago

Has anyone used the Sperti UVB vitamin D lamp? https://www.sperti.com/product/sperti-vitamin-d-light-box

It appears to be the only FDA approved one.

pooya13• 7 years ago

Eventually all artificial lights that don’t help with vitamin D deficiency should be banned.

jforman• 7 years ago

It is FDA cleared rather than approved, which is a lower bar. And it appears to be cleared as a tanning device, not as a Vitamin D-related device:

https://www.accessdata.fda.gov/cdrh_docs/pdf15/K151721.pdf

Note that the manufacturer has gotten in trouble with the FDA before:

https://www.fdalabelcompliance.com/letters/ucm284022

So I'd maintain some skepticism on the product's efficacy as it related to health. (I tried finding other clearances related to the product and failed, but they might still be out there...)

fitzroy3• 7 years ago

Interesting. Thanks for the information!

hypertexthero• 7 years ago

Have never used one of these, but have heard good things about lamps from https://www.circadianoptics.com/ from friends living in high latitudes.

dcx• 7 years ago

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...

ypolito• 7 years ago

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.

JimboOmega• 7 years ago

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.

eurg• 7 years ago

"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."

https://slatestarcodex.com/2018/07/10/melatonin-much-more-th...

maxxxxx2• 7 years ago

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.

phaedrus• 7 years ago

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..

dzhiurgis3• 7 years ago

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”...

jlarocco2• 7 years ago

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.

PKop2• 7 years ago

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?

https://www.outsideonline.com/2380751/sunscreen-sun-exposure...

lmilcin• 7 years ago

I would add early morning sunlight helps regulate circadian rhythm.

victor106• 7 years ago

Does anyone know of any instruments you can use to measure uva and uvb?

dharma12• 7 years ago

You can build your own, https://makezine.com/projects/build-hack-and-deploy-detector...

Or buy one https://www.solarmeter.com/model65.html

pkaye• 7 years ago

I get my vitamin D levels check every quarter because of my kidney failure. Based on my past experiments, I'd say if you are in the bay area, walking in the noon sun for 15 minutes every workday would be enough to keep healthy vitamin D levels. In terms of supplements, about 1500 IU/day is enough during winter season.

mettamage• 7 years ago

When I lived at my parent’s place the following scene always was a bit odd during the winter months:

“Hey Mettamage, why is your window wide open? It’s freezing!”

“I need vitamin D.”

“Then why do you cover your body with a blanket?”

“It’s cold.”

vinayan3• 7 years ago

Simple solution. Open the window in your house or in your car while you driving. You will then get direct exposure to the sun!

dharma12• 7 years ago

it's interesting how UVB also modulates eye growth (and myopia) - https://jamanetwork.com/journals/jamaophthalmology/fullartic...

"After adjusting for high levels of education, a well-established risk factor for myopia, they found that participants with the highest UVB exposure, especially in the teenage and young adult years, had about a 30% lower risk for myopia than those with the lowest exposure. The study also found no association with myopia and vitamin D levels or genetic variants in Vitamin D."

manicdee• 7 years ago

Also note: research on vitamin D has suggested that it’s not vitamin D that provides the benefits often touted, but the fact that you are outside getting exercise.

Thermolabile• 7 years ago

The article mentions commercial and automobile glass. What about forty year old double pane glass in an old house? On very cold winter days in Vermont I enjoy a kitchen bathed in sunlight. No benefit?

hema_n• 7 years ago

“It doesn’t matter if it’s winter or summer, you will make no vitamin D sitting in front of a window"- this is a true statement.!

neop1x• 7 years ago

Be careful not to have vitamin D deficiency! I think that might have been one of things which contributed to my multiple sclerosis. I was sitting in front of pc most of the spring/summer, rarely spending time outside...

Sunlight through glass does not provide Vitamin D

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