Some thoughts on Vitamin D, flu, etc

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Ali Tait
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#46 Re: Some thoughts on Vitamin D, flu, etc

Post by Ali Tait »

Which paler skinned people are better at doing than their darker skinned counterparts as far as I’m aware?
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#47 Re: Some thoughts on Vitamin D, flu, etc

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Yes, certainly - that's why it evolved as people migrated North .
You did say 'at low light levels' ! - The adaption is for 'Northern European sunshine levels' :)

ps. For evidence of what is a meaningful dose, how quickly you can raise it, how quickly it drops without supplements, what is toxic, etc etc, this is a paper I read years ago and have saved :
https://academic.oup.com/ajcn/article/69/5/842/4714819
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#48 Re: Some thoughts on Vitamin D, flu, etc

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IslandPink wrote: Sat Jan 11, 2020 5:31 pm
ps. For evidence of what is a meaningful dose, how quickly you can raise it.
Well really ! :shock: ( :lol: :lol: )
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#49 Re: Some thoughts on Vitamin D, flu, etc

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Chortle !
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izzy wizzy
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#50 Re: Some thoughts on Vitamin D, flu, etc

Post by izzy wizzy »

IslandPink wrote: Sat Jan 11, 2020 5:10 pm Correct, it's not true. Only UV-B getting through to the relevant layers of the skin can produce vitamin D. There's very little UV-B that gets through the atmosphere when the sun is below 45°to the ground.
Well that would seem you are saying that redheads don't produce healthy levels of vitmain D in low light conditions. If so, can you point to where you got this information as it seems at odds with anything I've found.
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#51 Re: Some thoughts on Vitamin D, flu, etc

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I'm trying to be accurate ( aka pedantic ) about the language used here. Nobody can produce vitamin D in their skin at 'low light levels'.
What having pale skin and red hair does, is allow you to produce enough vitamin D in lower UV levels than other people.
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#52 Re: Some thoughts on Vitamin D, flu, etc

Post by izzy wizzy »

IslandPink wrote: Sat Jan 11, 2020 6:06 pm I'm trying to be accurate ( aka pedantic ) about the language used here. Nobody can produce vitamin D in their skin at 'low light levels'.
What having pale skin and red hair does, is allow you to produce enough vitamin D in lower UV levels than other people.
Don't quite see the difference but hey, I shall carry on producing Vit D when others can't do as well with my mutant genetics. All is right with the world again :)
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#53 Re: Some thoughts on Vitamin D, flu, etc

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Well, one difference is that 'light' is not the same as 'UV'. UV is the stuff below 400nm , light goes from approx. 400nm to 700nm wavelength. To be fair there is some looseness in the general use of 'light' as a word, I prefer to use 'light' purely to describe visible light, I think most of my colleagues in optics stick to this.
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#54 Re: Some thoughts on Vitamin D, flu, etc

Post by izzy wizzy »

If Ali had said "One benefit of being ginger, your body can produce healthy levels of D at low sun light levels." would we have been OK for you optics guys?
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#55 Re: Some thoughts on Vitamin D, flu, etc

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Just to be absolutely accurate (or pedantic), Vitamin D is synethesised by exposure to UVB in the "...spectral range (255–330 nm) with a maximum at about 295 nm...".

This is the source of this information, an interesting read;

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4642156/

There are several references to related docuemnts in the 'Similar articles' section of the page should you feel so inclined.
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#56 Re: Some thoughts on Vitamin D, flu, etc

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izzy wizzy wrote: Sat Jan 11, 2020 7:05 pm If Ali had said "One benefit of being ginger, your body can produce healthy levels of D at low sun light levels." would we have been OK for you optics guys?
Yes, it's being an optics guy that is the problem. I'm currently involved in designing a night-vision objective lens. When we talk about 'low light levels' in that context, it starts at 'dimly-lit street' and goes down to 'clouded starlight, no moon, miles from any town'.
The thing about daylight also, though , is that anything that makes it dimmer, eg. sun being lower, or cloud ( at least beyond some haze ) will knock out the UV and particularly the UV-B long before it significantly drops the visible light level.

One thing just occurred to me while I was under the sunlamp, Stephen ( no, really ) : your are from NZ originally, am I correct ?
If so, wasn't the ozone hole most severe over there, and about 20 or 30 years ago ?

Thanks for the link Ray, will read it later.
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Ali Tait
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#57 Re: Some thoughts on Vitamin D, flu, etc

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Thanks for the link Mark, will have a read tomorrow.
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#58 Re: Some thoughts on Vitamin D, flu, etc

Post by izzy wizzy »

IslandPink wrote: Sat Jan 11, 2020 8:30 pm One thing just occurred to me while I was under the sunlamp, Stephen ( no, really ) : your are from NZ originally, am I correct ?
If so, wasn't the ozone hole most severe over there, and about 20 or 30 years ago ?
It probably was bad then but I wasn't there; left 35 years ago. Don't remember it being talked about then. I just remember the sun being vicious anyway and that hole made things worse when it circled over NZ. There's a concerted effort to reduce the effects of UV starting with kids. Sunhats are a mandatory item of school wear, much public awareness of the damage it does etc. When I left, people were chasing the tan. Now when I go back, that is the exception.

A pale skinned friend in Oz uses an app to calculate when you should be out in direct sun to get your 10min dose of vit D (rough approximation from memory). She was here last Feb and it calculated the next opportunity was sometime April/May. Guess that's why you're under a sun lamp.
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#59 Re: Some thoughts on Vitamin D, flu, etc

Post by simon »

I remember visiting my cousin in NZ in 1995. They were well aware of the hole in the ozone and El Nino/La Nina effects back then, just as we were becoming aware over here.

I think I read that the effects of the sun can actually be worse in NZ than Oz. Presumably because of the hole in the ozone, but perhaps because it doesn't feel as hot and sunny in NZ as it can in Oz so there may be a temptation not to slip slap slop as much??? (It's the old Aussie joke - you don't tan in NZ you rust.)

They have their own formulation sun block in NZ too which I think is higher rated than Australian, and when I went last 4 years ago I don't recall seeing too many tans as izzy says.
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#60 Re: Some thoughts on Vitamin D, flu, etc

Post by simon »

Maybe 20 years ago we had a fortnight in Thailand in February. The beneficial affect of the sun in the depths of winter was huge, and carried me all the way through summer, but in a way that was better than usual in summer. I haven't explained that very well, hope it makes sense.
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