
Sunlight through glass does not provide Vitamin D - bookofjoe
https://www.nytimes.com/2019/02/08/well/live/does-sunlight-through-glass-provide-vitamin-d.html
======
dcx
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...](https://www.sciencedirect.com/science/article/pii/0273230092900358)

[2] [https://valtsus.blogspot.com/2017/05/the-therapeutic-
effects...](https://valtsus.blogspot.com/2017/05/the-therapeutic-effects-of-
red-and-near.html)

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

[4]
[https://www.sciencedirect.com/science/article/pii/S0022202X1...](https://www.sciencedirect.com/science/article/pii/S0022202X15368974)

~~~
dzhiurgis
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”...

~~~
jlarocco
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.

~~~
dzhiurgis
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.

~~~
dragonsngoblins
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."

~~~
dwd
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.

~~~
lazyasciiart
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...](https://pdfs.semanticscholar.org/6944/503469e4f779e99884e144fd679f58a82966.pdf)
" 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.")

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

~~~
lazyasciiart
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.

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

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

~~~
harperlee
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.

~~~
JohnJamesRambo
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...](https://www.huffingtonpost.ca/2012/06/06/bill-mcelligott-sun-
damage_n_1573546.html)

~~~
swebs
Here's an archive for those getting Oath'd

[http://archive.is/aVhiM](http://archive.is/aVhiM)

~~~
iguy
Or the source:
[https://www.nejm.org/doi/full/10.1056/NEJMicm1104059](https://www.nejm.org/doi/full/10.1056/NEJMicm1104059)

------
rapsey
> 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.

~~~
Erlich_Bachman
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.

~~~
Amygaz
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.

~~~
newscracker
> 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.

~~~
jimmy1
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.

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

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

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

~~~
Meing4im
I have checked and according to graphs I have found both sapphire glass and
AlON both do indeed transmit UVB.

~~~
fastball
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!

------
ivanhoe
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.

------
SoulMan
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
capitalism

------
pjc50
UVB is required for health _and_ carcinogenic?

~~~
saalweachter
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.

~~~
sametmax
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.

~~~
saalweachter
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.

~~~
gugagore
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?

~~~
etherealG
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.

------
chippy
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.

------
Symmetry
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](https://www.bbc.com/news/science-environment-42939192).

------
syphilis2
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?

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

------
kaitari
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.

~~~
bluntfang
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
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...](https://www.nytimes.com/2018/02/16/well/live/do-i-get-enough-
vitamin-d-in-the-winter.html)

~~~
bluntfang
Great to know! I just started supplementing vitamin D this year in New
England, and it seems like it's really helpful.

I think a big part of my point was about the resiliency of children. It's
worrying that new parents are scared to experience the world with their
children.

~~~
mikemac
as a new-ish parent, i'd love to get my kids outside to soak up sunlight but
it's nearly impossible to stay outside for any meaningful amount of time in
the northeast winter.

~~~
bluntfang
I've seen parents schlep <1 year old babies up some of the White Mountains in
mild winter conditions (snow on the ground, below 32F, etc). I think you are
doing something wrong.

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

~~~
lm28469
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.

~~~
kuon
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.

------
izzydata
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.

------
victor106
Does anyone know of any instruments you can use to measure uva and uvb?

~~~
dharma1
You can build your own, [https://makezine.com/projects/build-hack-and-deploy-
detector...](https://makezine.com/projects/build-hack-and-deploy-detectors-to-
measure-solar-uv-radiation/)

Or buy one
[https://www.solarmeter.com/model65.html](https://www.solarmeter.com/model65.html)

------
mettamage
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.”

------
manicdee
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.

------
pkaye
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.

------
bellerose
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
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.

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

It appears to be the only FDA approved one.

~~~
jforman
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](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](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...)

~~~
fitzroy
Interesting. Thanks for the information!

------
dharma1
it's interesting how UVB also modulates eye growth (and myopia) -
[https://jamanetwork.com/journals/jamaophthalmology/fullartic...](https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2588252)

"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."

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

------
neop1x
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...

------
hema_n
“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.!

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

------
vinayan3
Simple solution. Open the window in your house or in your car while you
driving. You will then get direct exposure to the sun!

------
air7
tldr: no.

------
Thermolabile
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?

------
leemailll
Isn’t this common sense?

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

~~~
turc1656
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.

~~~
hombre_fatal
Doesn't seem like much intuition was had in your example, to be honest.

The teacher primed you with "Why have you never gotten burned on a long summer
drive?" and then you bought that as fact and backsplained it with some basic
prism experiments, the backsplanation not really mattering once you buy the
fact from the teacher.

In other words, I'm not sure what 30 second thought process you think the
average person can walk through to replace a teacher telling you the fact
outright.

Once you know a fact, people can "intuit" any explanation. Just talk to
children and listen to their bizarre theories -- but I would not call that
intuition because they cannot arrive at the original fact that way.

Besides, my intuition is the opposite. My friend was a truck driver and said
he'd get sunburned hands. He always kept sunscreen in the cabin.

~~~
turc1656
My point was that once you learn the basic physics underlying this, you should
be able to come to the proper conclusion about the vitamin D question easily
enough. Every person going through the US school system is required to take a
basic physics course, as far as I know. So every child who receives a HS
diploma in the US should know this basic concept and, if they actually thought
about it, should be able to figure it out.

I think you're confusing the underlying theory with us encountering the
question _on the day we learned it_ and then dismissing the fact that we were
primed with the current conversation to know the answer. What I'm saying is
that once we had that knowledge about the underlying physics, the same
question(s) could have been posed weeks or months later (with no priming) and
we should have been able to figure it out.

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

~~~
telesilla
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.

~~~
chooseaname
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.

~~~
dawidw
Maybe it's due to heat made by Sun?

~~~
chooseaname
No. Definitely pink from slight burn. Google says some side windows aren't the
same as the front and back.

