Sun light vs. damage & Vit.D

[Kasper]

However, what is a desirable vit. D level? It seems they go by the almighty RDA, or the Recommendations from the Institute of Medicine.

A serum level of 25-hydroxyvitamin D lower than 15 nanograms per milliliter (ng/mL)—equivalent to 37.5 nanomoles per liter (nmol/L)—is generally considered inadequate.
http://www.nap.edu/openbook.php?record_id=5776
The 2005 Dietary Guidelines for Americans notes that the optimal level may be as high as 80 nmol/L.

(long-term implications are unknown).

Long term implication of high vitamin D levels are as unknown as eating a natural raw diet (consider the Wai for example ).
Vieth and others have shown that the vitamin D levels in non-human primates (who still live the naked natural way in the sun) extend to beyond 200 nmol/L.
http://www.direct-ms.org/pdf/VitDVieth/ ... needed.pdf
Modern humans who live in sunny countries and spend much time in the sun have at least 100-140nmol/L, and more likely 135-225nmol/L in the summer.

That people in general might not get their personal optimal vit. D intake could very well be true, but which (dietary) amounts would be sufficient to remedy that, remains unclear.

So you think the literature is unclear about optimal vitamin D levels ?
Normally the wai diet advices, if you're unsure, do it the natural way.
Why is this not the case width vitamin D?
Our natural vitamin D blood level, where we humans evolved at for thousands of years, are much higher than those "almighty" recommendations where you are worried about.

By the way, does anybody (who is eating Wai) knows his vitamin D level? My vitamin D blood level was 25 nmol/L last summer.

[Kasper]

But one thing this study shows, is that after 1 year of supplementation,
five subjects (1.5%) had elevated 25-OHD levels at the end of the study ranging from 63 to 195 ng/ml; all were in the high-dose group.

Blood levels above 100 ng/ml are considered unsafe.
Since concentrations twice this amount have yet to ever be associated with toxicity. (Toxicity threshold level is 200-250 ng/mL (500-750 nmol/L).
http://www.ncbi.nlm.nih.gov/pubmed/18689406

In animal models, serum concentrations have reached as high as 400-700 ng/mL (1,000-1750 nmol/L) before toxic effects (severe hypercalcemia) were observed.
The reason that animals show even higher upper limits is unclear. Maybe because humans overdose on calcium?
A relatively new model is that vitamin K2 deficiency causes toxic effects of high vitamin D blood levels.


To make this clear, I don't say we need to supplement the diet width extra vitamin D. Or that we should eat (unnatural) much vitamin D rich food.
My point is that we need UVB exposure to get vitamin D blood levels above 30 nmol/L and that eating a healthy natural diet alone is not sufficient (even if it provides the RDA of vitamin D).

If you want to raise your vitamin D level in the winter, you can buy a UVB lamp, or even better, a lamp width gives the natural wavelengths of the (summer) sun.

You cannot make that conclusion, because here we dont have a dresscode as mentioned in the study,
covering head, arms, and legs.

Agree

So, on what do they base their hypothesis that higher vitamin D levels are better?

It's not only about bone health.
Vitamin D has been shown to influence at least 229 of the 30000 genes in our DNA. It's estimated that upwards of 2000 genes are directly or indirectly regulated by vitamin D.
As we evolved on high vitamin D blood levels, we need high vitamin D blood levels to let those genes work in the same way they have done for thousand of years.
If you think you have strong evidence that we need to keep our vitamin D blood level unnaturally low, I would like to see it.
But I rather live the natural way.

[RRM]

Yes, the RDA should be about health, not the result of a faulty hypothesis (that high bone mass is better).
In the study you posted:
"A vitamin D-replete state can be considered as one that does not produce secondary hyperparathyroidism"
That makes sense, as hyperparathyroidism is deleterious to bone health.
So, one should not set RDA in accordance with aiming at increasing bone mass,
but at preventing hyperparathyroidism and other deficiency symptoms

(long-term implications are unknown).

Long term implication of high vitamin D levels are as unknown as eating a natural raw diet (consider the Wai for example ).

We know the long term implication of eating raw food; it resulted in the evolution of mankind.
Enforcing elevated serum vitamin D levels is a different thing.

Vieth and others have shown that the vitamin D levels in non-human primates (who still live the naked natural way in the sun) extend to beyond 200 nmol/L.

They may also eat leaves from the trees, and dont live as long as us.
The question is: what effect do elevated vitamin D levels have on long term bone health?
(given that it induces bones mass, as high milk intakes do)

Normally the wai diet advices, if you're unsure, do it the natural way.
Why is this not the case width vitamin D?

It is.
Just eat some fish / egg yolks / meat daily, and you will be fine.

Our natural vitamin D blood level, where we humans evolved at for thousands of years, are much higher than those "almighty" recommendations where you are worried about.

Any evidence to back this up?

By the way, does anybody (who is eating Wai) knows his vitamin D level?

I dont.

[RRM]

But one thing this study shows, is that after 1 year of supplementation,
five subjects (1.5%) had elevated 25-OHD levels at the end of the study ranging from 63 to 195 ng/ml; all were in the high-dose group.

Blood levels above 100 ng/ml are considered unsafe.

So, it resulted in unsafe levels in some.

Since concentrations twice this amount have yet to ever be associated with toxicity.

Toxicity is just one aspect.
I did not have toxicity in mind.
Im concerned about the effects of elevated vitamin D levels on long term health.

In animal models, serum concentrations have reached as high as 400-700 ng/mL (1,000-1750 nmol/L) before toxic effects (severe hypercalcemia) were observed.
The reason that animals show even higher upper limits is unclear. Maybe because humans overdose on calcium?

Maybe because they are exposed to higher levels of vitamin D naturally.
Evolution tends to compensate for that.

A relatively new model is that vitamin K2 deficiency causes toxic effects of high vitamin D blood levels.

You tend to think in deficiences only.
Everything in our body is limited, so that everything needs to be balanced.
When you think in deficiencies only, you will not see that deficiency and excess both will cause an imbalance.

My point is that we need UVB exposure to get vitamin D blood levels above 30 nmol/L and that eating a healthy natural diet alone is not sufficient (even if it provides the RDA of vitamin D).

I understand your point.
The flaw that im seeing is the assumption that we need more vitamin D to maintain higher bone mass,
whereas in all countries where average adult bone mass is high, so are eventual osteoporotic fracture rates in the elderly.

As we evolved on high vitamin D blood levels

Any evidence?
Black people need more daylight exposure to get their vitamin D.
The skin of our early ancestors was black, to protect us against the sun,
and apparantly, that included the effects of UVB on endogenous vitamin D production.

I rather live the natural way.

Then you need a black skin to protect you against the effects of the extra sun exposure.

[Kasper]

Okay, here is some more empirical evidence which show beneficial effects at 25(OH)D levels above 37.5 nmol/L.

Progression osteoarthritis
Our findings suggest that elderly women with low serum levels of 25-vitamin D (8–22 ng/ml) are nearly 3 times as likely to develop incident radiographic hip OA, characterized by the development of joint space narrowing, as are elderly women with serum levels of 25-vitamin D in the highest tertile (30–72 ng/ml)

Our study suggests that persons with low intake and low serum levels of vitamin D (4.9-24.0 ng/mL) are approximately three times more likely to have progression of established osteoarthritis of the knee than are persons with high intake and high serum levels (36.0-79.0 ng/mL).

Rickets
The published 25(OH)D levels in children with frank nutritional rickets range as high as 20 nmol/L (8 ng/mL) (Chesney et al., 1981; Garabedian et al., 1983).

Diabetes
In our study we show that the intake of vitamin D supplement given to prevent rickets in early child-hood could also contribute to a decrease in risk for childhood-onset insulin-dependent diabetes.

These are a couple ones I could find quite quickly. But there are many more studies which show positive effects in diseases like:
Cancer, Hypertension, Heart disease, Autism, Obesity, Rheumatoid arthritis, Diabetes 1 and 2, Multiple Sclerosis, Crohn's disease, Flu, Colds, Tuberculosis Septicemia, Psoriasis Eczema, Insomnia, Hearing loss, Muscle gain, Cavities, Periodontal disease, Athletic performance, Macular degeneration, Myopia, Pre eclampsia, Seizures, Fertility, Asthma, Cystic fibrosis, Migraines, Depression, Alzheimer"s disease, Schizophrenia ...

Of course, I haven't read them all, but it's not hard to believe that vitamin D could have such a high impact on health.
Vitamin D has been shown to influence at least 229 of the 30000 genes in our DNA. It's estimated that upwards of 2000 genes are directly or indirectly regulated by vitamin D.

After calcitriol stimulation, we identified 2776 genomic positions occupied by the VDR and 229 genes with significant changes in expression in response to vitamin D. VDR binding sites were significantly enriched near autoimmune and cancer associated genes identified from genome-wide association (GWA) studies.

To let our genes work optimally, we need to have the 25(OH)D level as high as our DNA evolved at.
Because of clothes, living inside, avoiding direct sunlight, sunscreen, etc..., most of humans nowadays have much lower 25(OH)D blood levels.

Long term implication of high vitamin D levels are as unknown as eating a natural raw diet (consider the Wai for example ).

We know the long term implication of eating raw food; it resulted in the evolution of mankind.

That's exactly the point I was trying to make. We know the implication of eating raw food, because our DNA evolved at a raw diet.
Same argument goes for high vitamin D levels. We know the implication of high 25(OH)D blood levels, because our DNA evolved at high UVB exposure. (relative to the UVB exposure when wearing clothes, being inside, etc.)

[RRM]

Okay, here is some more empirical evidence which show beneficial effects at 25(OH)D levels above 37.5 nmol/L.

You are missing the point.
Vitamin D (i mean 25(OH)D, of course) is a hormone.
An elevated level of any hormone can have beneficial effects, for certain conditions.
If too much insulin is secreted, elevated levels of glucagon will have beneficial effects.
That does not mean we should elevate the level of any hormone in healthy human beings beyond our actual needs.
Do you really think there is one hormone that we could elevate in our body without adverse effects?
So, what is our actual need?
Our actual needs are met when all symptoms of deficiency are absent.
Beyond that there is still some room for elevation, but a subsequent elevation will prompt adverse activities.
Dont try to 'fix' something that is not broken.
If you are healthy, you dont need extra vitamin D.
If not, and you suffer from hyperparathyroidism, for example, it may be the result of a tumor, and not a lack of vitamin D.
Additional vitamin D would attenuate the syptoms, and leave the tumor to grow.

Vitamin D has been shown to influence at least 229 of the 30000 genes in our DNA.

Because thats what ALL HORMONES do!
Hormones are chemical messengers that transport signals to thousands or millions of cells,
requiring receptors, receptor protein and cell type-specific responses, and each and every detail of that process is embedded in genes.
Hence the hundreds of genes involved.
All hormones have various impacts in our body; hence the involvement of so many genes.
Thats normal for hormones.

To let our genes work optimally, we need to have the 25(OH)D level as high as our DNA evolved at.

There is no such level.
Why?
Because our evolution comprises millions of years.
In what point of history should we look at the 25(OH)D levels?
100.000 years ago?
1 million years ago?
5 million years ago?
And in what part of the world?
Africa?
Northern Europe?

Our natural vitamin D blood level, where we humans evolved at for thousands of years, are much higher than those "almighty" recommendations where you are worried about.

In which humans?
Where did they live, how long ago, and what was the colour of their skin?

Long term implication of high vitamin D levels are as unknown as eating a natural raw diet (consider the Wai for example ).

We know the long term implication of eating raw food; it resulted in the evolution of mankind.

That's exactly the point I was trying to make. ... We know the implication of high 25(OH)D blood levels, because our DNA evolved at high UVB exposure.

No, thats essentially different.
Let me give you an example:
Suppose 3 million years ago, the UVB exposure was 3 fold as high as now.
Would that mean we now would need the same exposure as we did back then?
No, because we have evolved and may live in a very different region.
We are not like then, and here is not like there.
Every time humans migrated north, our skin eventually got lighter, because there was less UVB exposure.
Thats is why people originating (what is originally, but anyway) from northern european countries, have such a fair skin.
Our skin evolved, particularly so to get the right amount of UVB.
As a matter of fact, even your skin will try to protect itself against UVB by getting a tan.
That tan is for your protection, against UVB.

Do you understand that there is no way that you can compare our current need for UVB exposure to that in the past?
The colour of our skin is the best proof that you cannot.
Every region in the world has its own requirements, also depending on the colour of the skin, and on other individual differences as well.

[Kasper]

I do agree that we need to find the right balance for vitamin D.
I'm not saying that we need to elevate vitamin D beyond our actual need.
I'm saying we need to get our vitamin D blood level at our actual need.
So we don't disagree here at all.

However the big question is:
What's our actual need of vitamin D? What is our optimal level of vitamin D? When is our vitamin D level in the right balance?

We can focus at determining our actual need for vitamin D by focusing on preventing hyperparathyroidism, preventing flu, preventing Alzheimer, etc. etc.
Or, we can focus on optimal muscle gain, optimal immune system, optimal well-being, etc.
But as you said, it is about balance. And is very hard to determine what the optimal balance is by looking at such studies.
On other way to determine our optimal vitamin D level is, looking at our natural vitamin D level.

It's likely that our optimal vitamin D level is, is the vitamin D level our DNA evolved at for million of years.

There is no such level. Why? Because our evolution comprises millions of years. In what point of history should we look at the 25(OH)D levels?

I'm not saying we evolved specifically at for example 100 ng/mL for the last million of years. Of course, it has fluctuated in the history of evolution.
But without any doubt we can set up a range of 25(OH)D levels our DNA has evolved at for the last million of years.

As I showed you, vitamin D levels in non-human primates extend to above 200 nmol/L. Average around 160 nmol/L.
It's estimated that around 107,000 years ago, first humans migrated out of africa and start to begin wearing clothes.
It's likely that up until that point in evolution, our DNA evolved at around the same 25(OH)D level (average 160 nmol/L) as non-human primates.

After that point, humans begin to wear more and more clothes and get less UVB from the sun when they migrated from the equator
Surely, this has made 25(OH)D levels lower. BUT Evolution of humans humans has compensated by getting a lighter skin.
And besides this, humans are still spending much time in the sun. To survive, they need to hunt, find berries, catch fish etc.

If we look at recent studies considering humans who spend much time in the sun but do wear clothes, we see that our 25(OH)D are still in the same range as our ancestor from Africa.
Those studies looks at lifeguards, farmers and hospital personal in Israel, Puorto Rico and St. Louis. Average 25(OH)D levels of those studies are 105, 135, 163, 148.
Edit: For the Lifeguards in the USA and Israel, as well as farmers in the Puerto Rico, the lowest level found was greater than 100 nmol/L. According to: this website
The highest individual serum 25(OH)D concentration obtained from sunshine was 225 nmol/L in a farmer in Puerto Rico.
The study about lifeguards in Israel (average 148 nmol/L) is particularly interesting.
It's estimated that our ancestors up to 35 000 YBP, are living around Isreael, or even closer to the equator.
This indicates that in the evolution of human DNA, until 35000 YBP, our 25(OH)D levels should have been in the range 100-200 nmol/mL or higher.
If we consider humans, whose ancestors come from Israel or closer to the equator, there is good evidence that their DNA evolved at 100-200 nmol/mL up until very recently.

Conclussion:
1. Human DNA width ancestors around Israel or closer to the equator evolved at 100-200 nmol/mL until very recently.
So do you agree that for those people their natural vitamin D level is as high as that ?

2. Human DNA width ancestors living further away from the equator evolved at 100-200 nmol/mL until 35000 YBP (or earlier).
I think that even in the Netherlands, if light-skinned human spend as much time in the sun as our ancestors, you will get vitamin D levels as high as 100 nmol/mL. But I couldn't find evidence very quickly to back this up, and it's already late, so I'll keep it like this for now.

But besides this, let's assume, for the sake of argument, that after 35000 YBP our 25(OH)D level drastically lowered when we migrated north.
Let's say our 25(OH)D level was around 10-30 nmol/mLfor around 30000 years.
Even if this is true, than it's still highly unlikely that our DNA completely adapted to this new vitamin D level.

The color of our skin proves that our DNA is able to adapt in 30000 years.
However, only a couple of genes are affected with changing skin colour.
But to adapt to a hormone level 10-folds lower than humans are used to, that it's a different story.
The amount of mutations needed to adapt to such a low vitamin D level, are of a complete different order.

[overkees]

Yes, I really do not understand the skin argument for vitamin D, RRM.

If I understand correctly you say that we need not so much vitamin D so that our skin became black to protect us from the sun, and therefore we made less vitamin D. BUT, you simply cannot overdose on vitamin D in the sun. The black skin is therefore a protection for burning in the sun and not for vitamin D.

We migrated north, where there is only a small amount of UVB available, then we got a lighter skin. Why?? Because the black skin seemed to be a disadvantage compared to the lighter skinned people. Why was there a disadvantage? Because the black people didn't get enough vitamin D compared to the lighter skinned people. Not because it was no longer needed. Nature tends to drop only drops the features that have a disadvantage when compared to other features. We still have a lot of rudimentary features that never dissapeared, because they never had a disadvantage when compared to copies that had dissapeared rudimentary features. Therefore we got a lighter skin, to compensate for the vitamin D shortage.

Another thing you say is there can't be an excess, but you fail to make the point when there is an excess of vitamin D. We see that a lot of things get prevented by taking or getting more vitamin D, so I think that we can assume that these are signs of deficiencies. You say that when you're healthy you're balanced, but how do you know your healthy? I don't know. I think vitality is a much more important feature that has a whole lot more to tell, and I noticed can feel much more vital than only having the wai diet. Due to alot of breathwork, running, swimming, cold showers and posture for example. I also feel much more energetic in the summer and I always enjoy the sunlight, I think the treat for skin cancer is exaggerated and are planning to do my own research. That is why I think there is always room to improve and not say you have found the ideal.

Environment changes, sometimes very rapidly (due to culture for instance), so we need to change and we have the ability to think and see and compensate for that effect (breathing is a very good example).

We NEED sun exposure to get optimal vitamin D levels. And we got a light skin, so it is alot easier to achieve. Supplementing with vitamin D will be unnecessary, but eating a little bit more fish in the winter will be a very good strategy in my opinion.

[Kasper]

How to get natural vitamin D blood levels ?

At least 4 studies support the concept that one full-body exposure to sunlight can be equivalent to an oral vitamin D intake of 250 mg (10 000 IU).
Ultraviolet exposure beyond the minimal erythemal dose does not increase vitamin D production further.
The concentration of previtamin D in the skin reaches an equilibrium in white skin within 20 min of ultraviolet exposure.
Although it can take 3–6 times longer for pigmented skin to reach the equilibrium concentration of dermal previtamin D, skin pigmentation does not affect the amount of vitamin D that can be obtained through sunshine exposure.

The highest individual serum 25(OH)D concentration attained by artificial ultraviolet light treatment sessions was 274 nmol/L.
The highest individual serum 25(OH)D concentration obtained from sunshine was 225 nmol/L in a farmer in Puerto Rico.
In a report showing results for 391 subjects that excluded individuals taking calcium or vitamin D supplements, reported 3 subjects with serum 25(OH)D concentrations >200 nmol/L.
There isn't any study that shows overdosing on vitamin D by sunshine or artificial UVB exposure is possible.

Conclusion:
For people width white skin, only 20 min of full-body exposure in midday summer sun is effective in getting natural high vitamin D blood levels.
Overdosing on vitamin D by sunshine isn't possible.
The minimal erythemal dose happens BEFORE the concentration of previtamin D in the skin reaches an equilibirium.
So making sure you don't get burned goes hand in hand width optimizing vitamin D blood levels.

[RRM]

I have very little time tonight, so my response will be hasty.
I apologize for that.

How much vitamin D do we need?
How much do we need to maintain vitamin D levels in healthy human beings in such a way that no deficiency symptoms will occur.

If you think one should set recommendation for 25(OH)D blood levels at aiming at preventing secondary hyperparathyroidism,
than we can conclude out this study that one should set the recommendation around 78 nmol/mL (even higher than 37.5 nmol/L).

For those particular people with HPTH, yes. So, you really are considering 78 nmol/mL now?

We can focus at determining our actual need for vitamin D by focusing on preventing hyperparathyroidism, preventing flu, preventing Alzheimer, etc. etc.

As if these are exclusive vitamin D deficiency symptoms.
Of course that IS the way to go about it:
We need as much vitamin D as required to prevent vitamin D deficiency symptoms.

This indicates that in the evolution of human DNA, until 35000 YBP, our 25(OH)D levels should have been in the range 100-200 nmol/mL or higher.

No it doesnt.
That range must have been much wider, as the individual differences are much greater.

As I showed you, vitamin D levels in non-human primates extend to above 200 nmol/L. Average around 160 nmol/L.

And what is the lowest level found?
Dont just look to the highest levels. Try to find the natural range.

Those studies looks at lifeguards, farmers and hospital personal in Israel, Puorto Rico and St. Louis. Average 25(OH)D levels of those studies are 105, 135, 163, 148.
The highest individual serum 25(OH)D concentration obtained from sunshine was 225 nmol/L in a farmer in Puerto Rico.

The lowest levels in healthy individuals are also essential in getting to know how much we need.
We dont need part of the picture, but the whole picture.

Conclussion:
1. Human DNA width ancestors around Israel or closer to the equator evolved at 100-200 nmol/mL until very recently.
So do you agree that for those people their natural vitamin D level is as high as that ?

I dont agree that we can conclude the range was 100-200 nmol/ml.
Its pure speculation.
The israeli lifeguards may have a much lighter skin than the people that naturally lived there.

[RRM]

you simply cannot overdose on vitamin D in the sun.

If you mean toxicity, no.
Im not talking about that.
But yes, vitamin D will be produced beyond your needs if you overdo it in the sun.
Hence, yes, its also protection against increasing vitamin D too much.

you fail to make the point when there is an excess of vitamin D.

I will show you later.

I also feel much more energetic in the summer and I always enjoy the sunlight,

serotonin.

I think the treat for skin cancer is exaggerated

Not just cancer.
Also accelerates ageing of the skin.

We NEED sun exposure to get optimal vitamin D levels.

Daylight exposure will do.

eating a little bit more fish in the winter will be a very good strategy in my opinion.

Agree.

[Kasper]

The level of vitamin D that healthy people need, is the level that keeps them from getting deficiency symptoms.

Some evidence I've found shows:
- Serum PTH×25(OH) D levels in 393 healthy adolescent females (12–18 years). 
The data suggested that the change in the slope of the plot for serum 25(OH)D from negative to positive occurred at 90 nmol/l.
- Guillemant and colleagues found that when 25(OH) levels fell below 83 nmol/l when assayed using the CPB method, the increase in PTH concentration accelerated
- Chapuy and colleagues [14] reported that in French adults (35–60 years), serum PTH levels were stable at a 25(OH)D concentration of 78 nmol/l (CPB assay)

So, you really are considering 78 nmol/mL now?

No... I thought you were proposing to look at preventing HTPH...
I said that this was not a good idea. And that we should look at our natural level.

To estimate the circulating 25(OH)D concentrations prevalent in humans of the late Paleolithic period, we need to focus on people in sun-rich environments who regularly expose most of their skin surface to the sun.
Lifeguards in the United States and in Israel, as well as farmers in the Caribbean all exhibit serum 25(OH)D concentrations greater than 100 nmol/L.
Furthermore, even regular short periods in sun-tan parlors consistently raise serum 25(OH)D to beyond 80 nmol/L. (7 studies)
The synthesis of vitamin D is a self-limiting chemical reaction whereby equilibrium is achieved between production of precursors that will become vitamin D, and the photocatalytic breakdown of these precursors and vitamin D into inactive molecules.
Skin color does not affect the amount of vitamin D that can be generated. However, darker skin requires longer exposure. Very black skin requires about 1.5 hr, or six times longer than white skin, to reach the equilibrium for vitamin D production.
At least four studies show that UV exposure of the full skin surface of an adult is equivalent to a vitamin D consumption of about 250 ug (10,000 IU/d).

Do you think... hmm... maybe our natural ancestors did expose theirself regulary to the sun. That SEEMS to make SOME sense.
For a black skin it takes 1.5 hour to produce the MAXIMUM amount a human skin can produce in a day.
For a light skin it takes 20 min to produce the MAXMIUM amount a human skin can produce in a day.

Don't you think that when our black ancestors where hunting an animal, they might have spend 1.5 hours in the sun ?
Don't you think that our white ancestors where spending 20 min. in the sun when they were trying to catch a fish ?

Or do you think those people where covering their self completely width animal skin and where using ancient sunscreen....??
Well, let's assume, for simplicity, that they weren't...

ALL the evidence that's out there, shows consistently that our natural 25(OH)D blood level is much higher than the recommended 37.5 nmol/L.
Since our genome was selected through evolution under these conditions, it should be evident that our biology was optimized for a vitamin D supply far high than what RRM/Oscar currently regard as normal.

Not just cancer. Also accelerates ageing of the skin.

Well, I think this is true. I don't notice it, but I'm still young. I can imagine that some people have big problems width this.
More than 20 min of full body exposure gives no benefits for white skin, so that's good to know if you are worried.
Surely don't get burned, because that's a clear sign you overdoing it way to much.
Eating astaxanthin (organic or wild salmon) has shown to reduce wrinkle forming and other signs of skin aging. So that is a must have if you want to look young.
If you are really worried, you could try to eat a whole lot of fish, and avoid direct and indirect sunlight (as RRM showed that indirect sunlight can contain UVB, which will accelerate aging of the skin)

But this is a unnatural way to live, and could have side effects we don't oversee just yet.
Fumaric acid, and maybe others, are other things we produce in our skin as a result of UVB exposure, and probably there is a good reason for it.

And not to forget, we are supposed to look older when we age!
Not smoking, eating a healthy diet rich in antioxidants like astaxanthin, etc. , will already make someone look much younger than others of his/her age
If you also avoid direct and indirect sunlight, you will make people only unnecessary jealous in my opinion.

Vitamin D will not cut it, because 'seasonal affective disorder' is not just about vitamin D, but also about serotonin and cholesterol.

I also feel much more energetic in the summer and I always enjoy the sunlight

Vitamin D is more effective than broad spectrum therapy in helping people who feel depressed.
All subjects receiving vitamin D improved in all outcome measures. The phototherapy group showed no significant change in depression scale measures.
Improvement in 25-OH D was significantly associated with improvement in depression scale scores.

We NEED sun exposure to get optimal vitamin D levels.

Daylight exposure will do.

You don't know that.
For example:
1. If someone gets daylight only through windows or other material which don't allow UVB.
2. If someone covers his skin for 95% width clothes, you won't produce a significant amount of vitamin D in your skin.

[RRM]

Again, im having little time, so please excuse me for my hasty response.

- Serum PTH×25(OH) D levels in 393 healthy adolescent females (12–18 years). 
The data suggested that the change in the slope of the plot for serum 25(OH)D from negative to positive occurred at 90 nmol/l.
- Guillemant and colleagues found that when 25(OH) levels fell below 83 nmol/l when assayed using the CPB method, the increase in PTH concentration accelerated
- Chapuy and colleagues [14] reported that in French adults (35–60 years), serum PTH levels were stable at a 25(OH)D concentration of 78 nmol/l (CPB assay)

Ah, this is more like it!
I will look into these studies when i have some time.
Any long term studies?

To estimate the circulating 25(OH)D concentrations prevalent in humans of the late Paleolithic period, we need to focus on people in sun-rich environments who regularly expose most of their skin surface to the sun.

Nonsense.
In Europe, vast areas of land were covered by thick forests.
Have you ever gone into the forest on a sunny day?
Once you leave the forest, you get surprised by how sunny it (still) is, because you couldnt notice while in the forest.
Caves dont give you much sun exposure either.
Also, it seems very likely that their skin was not the same as our skin is now;
probably our skin is less hairy and more pale.

Skin color does not affect the amount of vitamin D that can be generated. However, darker skin requires longer exposure.

So, a darker skin protects you against excessive vitamin D production.
Thats what im trying to tell you.

Don't you think that when our black ancestors where hunting an animal, they might have spend 1.5 hours in the sun ?

Sometimes, sure.
Hunting in the open, man stands little chance though.
Except for catching fish.
And again, our skin was different back then.

Don't you think that our white ancestors where spending 20 min. in the sun when they were trying to catch a fish ?

On most days, the sun may have been blocked by clouds, dont you think?

ALL the evidence that's out there, shows consistently that our natural 25(OH)D blood level is much higher than the recommended 37.5 nmol/L.

No, thats all speculation; deductive science.
Interesting, but speculative.
You need actual vitamin D levels measurements,
and not just in sunny countries, but also in less sunny countries.

All subjects receiving vitamin D improved in all outcome measures.

Calcitriol increases serotonin levels.

If someone covers his skin for 95% width clothes, you won't produce a significant amount of vitamin D in your skin.

Not true, as it depends on the total duration of sun and daylight exposure (of that 5%).
Think of tuaregs, for example.

[Kasper]

So, a darker skin protects you against excessive vitamin D production.
Thats what im trying to tell you.

No, a darker skin protects you against excessive UVB exposure.
A white skin protect as good as an black skin against excessive vitamin D production by UVB exposure.
Both skin types show that there is a mechanism which makes sure vitamin D production in the skin is stopped at a certain level.
When people ingest 10000 IU in supplement form, vitamin D blood levels keep raising, even when vitamin D blood levels get toxic.

To estimate the circulating 25(OH)D concentrations prevalent in humans of the late Paleolithic period, we need to focus on people in sun-rich environments who regularly expose most of their skin surface to the sun.

Nonsense. In Europe, vast areas of land were covered by thick forests.

The Paleolithic period ends around 10,000 BP.
The last glacial period was the most recent glacial period within the current ice age occurring from approximately 110,000 to 10,000 BP.
Ecological zones in Europe at the last glacial maximum, ca 18,000 BP, are estimated to look like this:

Only at some coastal regions, we see a lot of forest.
BUT, at those coastal regions, it's likely that people spend much time around the sea/beach to for example catch fish.

Most forest in europe originated after the last glacial period. First signs of agriculture are around the same period.
It's more likely that our DNA adopted to agriculture, than it adopted to living predominantly in thick forests width limited UVB exposure.

On most days, the sun may have been blocked by clouds, dont you think?

According to you: "Cloud cover reduces UV levels, but not completely; you [can] get burned on a cloudy day."
And besides that, I don't think that on MOST days the sun was blocked, but I don't know the climate back than.
Now it's like 50/50 or something cloud vs sun, I guess ?

ALL the evidence that's out there, shows consistently that our natural 25(OH)D blood level is much higher than the recommended 37.5 nmol/L.

No, thats all speculation; deductive science. Interesting, but speculative.

Of course, its speculation. In some sense, that's what all science is.
It's about making the best guess (model) width the evidence currently available.
And as it goes about setting up our natural/normal vitamin D level:
The models currently proposed by vitamin D researchers, all put our natural vitamin D level much higher than the recommended 37.5 nmol/L.

Of course, that's speculation, but convincing speculation, if you see were it's based on, in my opinion.
Don't you think ?

[dime]

The point is direct sunlight damages the skin. It hurts, it's red, dry, inflamed. You don't need studies to figure that out.
I'd be interested to see some graph that plots damage vs. time exposed on the sun.