Sun light vs. damage & Vit.D

[RRM]

If people are deficient of vitamin D in sunny countries then this is very likely caused by clothing habits (such as the ethiopian study).

Thats protection against the relentless sun.
I dare you to expose yourself to the Ethiopian sun without protection...
Exactly what im talking about; weighing cons and pros.

I don't see any reason why you're suggesting that dime shouldn't raise his vitamin D level above 40 nmol/L.

Rural Indian farmers;
Even with 5 hours of daily sunshine exposure 68.5% had serum 25(OH)D levels below 50 nmol/L
The mean 25(OH)D values of all subjects in the rural area was 36.4 nmol/L.Goswami R et al

There is too much evidence that the body may prefer lower levels.
Forcing these levels up may have adverse effects.
At least, increased UV exposure will accelerate ageing of the skin.

In evolutionary sense, this is a very low vitamin D level.

Adaptation, adaptation...

So, if the body is so adaptive, why does it maintain such (relatively) low blood levels?
Even in sunny countries...

Clothing habits, overexposure to water, being indoors most of the time, etc. etc.

No, my question was:
Why does the body not adapt to this habit of wearing clothes etc.?
The body has been shown to be very adaptive regarding UV exposure and vitamin D levels.

People that live a traditional lifestyle, a lifestyle we evolved at, then vitamin D level isn't low at all.

Did you see their skin?
You dont want a skin like that...
Also, white people did not evolve at these serum vitamin D levels at all.
And again, adaptation.
As humans moved out of Africa (and started wearing clothes), we adapted rapidly.
(to the extend of about 7.5 nmol / L per 400 years. Signorello LB)

[Kasper]

Adaptation, adaptation...

If things where thát simple, then we would be adapted to cooked food a long time ago.
For calcium (in lesser extend) the same is true.

[RRM]

It has been shown that humans are remarkably adaptive regarding sun exposure and vitamin D levels,
to the extend of about 7.5 nmol / L per 400 years. Signorello LB,
which is quite impressive. (maybe because its a hormone)
And yes, we are also somewhat adapting to the toxins in cooked foods (and cigarettes), as there are several enzym systems (P450) involved in their detoxification.
Calcium metabolism may be a harder nut to crack, as by minimizing it gets increasingly harder to further decrease fractional calcium uptake, and Its not possible to decompose calcium (just to gradually deport it),

If levels of 36 nmol/L of vitamin D are quite normal even with 5 hours of daily sunlight exposure in a tropical country,
we should not blindly adhere to a much higher recommendation,
because it may be that the body (in specific conditions) prefers that level over a higher level.
Instead of UV exposure, it may be smarter to offer dietary vitamin D generously (regular fish intake).

[dime]

Novel Mechanism by Which UVA Contributes to Photoaging of Skin

The findings demonstrate that aspects of photoaging, the process of skin aging by chronic exposure to ultraviolet radiation, could be linked to genetic factors that accelerate the aging process when induced by the environment.

[fred]

Please confirm that excess vitamin D can only come from excess dietary vitamin D, and not from sun exposure ?

[RRM]

I cannot confirm that.
The higest average serum vitamin D levels are found in lifeguards, due to extensive daily sun exposure.

The study about lifeguards in Israel (average 148 nmol/L) is particularly interesting.

I agree.
They seem to have a lot more kidney stones than normal... Shabtai M et al
"Eleven of 45 (24%) Lifeguards had proven N (= nephrolithiasis = kidney stones). This is approximately twenty times the incidence of N in the general population". Better OS et al

So, yes, sun exposure may increase serum vitamin D (or not),
and excessive sun exposure may do so (or not) to such an extend that this very much increases the risk of kidney stones.
Even in sunny countries and with abundant sun exposure (eg 5 hours / day), serum vitamin D may be low on average (down to 36.4 nmol/L) for a (protective) reason.

[fred]

Kidney stones can be caused by many factors, like dehydratation, excess protein and calcium intake, magnesium and K deficiency, etc.
Do we know the factors that contribute to the high incidence of nephrolithiasis in lifeguards ? I don't have access to the full article.

[RRM]

Kidney stones can be caused by many factors

Excess vitamin D is a well established factor.

Do we know the factors that contribute to the high incidence of nephrolithiasis in lifeguards ?

High serum vitamin D, due to extensive daily sun exposure.
Their mean level was 148 nmol/L

[RRM]

Among 36,282 postmenopausal women, 50 to 79 years of age, daily calcium (1000 mg) plus vitamin D3 supplementation (400 IU; their reference intake) increased bone mineral density (BMD),
did not reduce hip fracture, and increased the risk of kidney stones. Women's Health Initiative Study
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