Sun light vs. damage & Vit.D

[MJ]

In Wai's book, she says to get as much sunlight as possible. However, it seems that the general concensus in our society now is that we should cover up from the sun as much as possible to avoid skin damage from the sun. Personally, I have ended up getting freckles and sunspots on my skin from being in the sun, so I use sunblock and cover up as much as possible.

So what's the deal? It is a fact that sunlight can damage the skin and increase your chance of getting skin cancer, so why does the Wai Diet recommend getting more sun exposure?

[MJ]

I live in California. There are times where the sun feels so hot that I feel the "burn" on the back of my neck and on my arms within a few minutes of being under the sun without sunblock. Now I almost always wear long sleeve shirts, a hat, and put on sunblock.
I believe people can get skin damage from UVA rays which can still get to you even on cloudy days. I'd be willing to get that most people in the UK don't use sunblock because they don't feel they will be harmed because it is cloudy. However, I do understand what you all are saying in regards to the skin reacting differently when it is healthy.
So what happens if I have to be in direct sun light? Do you recommend sunblock for those situations?

[RRM]

In Wai's book, she says to get as much sunlight as possible.

It specifically says daylight, not sunlight. Somewhere else it says to avoid direct sunlight.
Daylight exposure is good for your serotonine metabolism; it doesnt require direct sunlight exposure.

So what happens if I have to be in direct sun light? Do you recommend sunblock for those situations?

A big hat is better, and/or clothes.
Or an umbrella.

[colorles]

the lighter your skin is, the least you should expose it to direct sunlight
however if you have relatively light skin but genetically thicker fat under and around the skin evenly distributed, your skin will be alot more resiliant than light and 'thin skin'
perhaps humans were naturally ment to do well in sunlight, but then again perhaps only relatively darker or moderate skin peoples.

[Kasper]

It specifically says daylight, not sunlight. Somewhere else it says to avoid direct sunlight.
Daylight exposure is good for your serotonine metabolism; it doesnt require direct sunlight exposure.

I don't understand this advice at all...
Serotonine is surely not the only thing we get from the sun.
Fumaric acid and vitamin D are created from direct sunlight exposure (reflection from snow and water will do the same job I guess).
But windows etc block the UVB rays which is needed.
You can get the RDA for vitamin D in this diet. But the RDA is not based on persons who avoid direct sunlight.
Edit: Many studies show that you don't get healthy vitamin D levels from ingesting the RDA alone. So I guess that the RDA is not only based on dietary vitamin D but also on UVB exposure.

Total-body sun exposure easily provides the equivalent of 250 μg (10000 IU) vitamin D.
Why would your body make such high amount, if 400 IU is already enough ?

[dime]

You can get the RDA for vitamin D in this diet. But the RDA is not based on persons who avoid direct sunlight.

Where is it written on what is the RDA based?

[overkees]

They updated the RDA to 600UI just recently to get the total vitamin d of north americans above 20 micrograms. That is why old people need 800UI, because they spend less time outside. So, you really need alot more vitamin D in the winter, twice as much as we previously thought to be completely safe.

Here it is stated that they only looked to the job vitamin D does in calcium absorption to establish a RDA: http://ods.od.nih.gov/factsheets/Vitami ... fessional/

There are many researches that report very good results with over 1000UI of dietary vitamin D:
http://www.ncbi.nlm.nih.gov/pubmed/20219962
http://www.ncbi.nlm.nih.gov/pubmed/19781131
http://www.ncbi.nlm.nih.gov/pubmed/18793245
http://www.ajcn.org/content/85/6/1586.abstract

and the lists goes on and on and on.

The Upper Limit for dietary vitamin D has been raised to 4000UI.

In this article it is stated that vitamin D works best when it's levels are kept stable: http://www.ncbi.nlm.nih.gov/pubmed/19667164
That is why so many people have this winter blues thing going on.. in the summer they spent a lot of time outside and then all of a sudden they only go outside when it is really necessary. So in the winter we must eat a whole lot more vitamin D to prevent it from fluctuating too rapidly.

The conclusion from these researches for me is that it you can better eat more vitamin D than the RDA advices, and it is very hard to overdo it when you don't supplement. In the winter we must also eat alot more vitamin D and since we spent almost all of our time inside I might even consider eating a fatty fish or egg yolk for lunch and also consuming it as dinner. Adding some more olive oil to prevent the balance to go to the omega 3 side too much.

This guy Vieth R seems to be researching vitamin D and related mechanisms all his life and has much more to say about it, a must read is:
http://www.cmaj.ca/content/166/12/1541.full

where he adviced to take 1000 UI for adults daily

[Kasper]

Many studies show that you don't get healthy vitamin D levels from ingesting the RDA alone. So I guess that the RDA is not only based on dietary vitamin D but also on UVB exposure.
But now I studied a little bit more, I found out that the RDA is based on limited sun exposure...
This makes me (and many vitamin D researchers) conclude that the RDA is not adequate.

Look at this for example:
http://www.ncbi.nlm.nih.gov/pmc/article ... figure/F3/

And beside all those studies, there is also the "do it the natural way argument".
We get much more vitamin D when we are exposed to direct sunlight. The most natural way to get healthy vitamin D (and fumeric acid) would be to spend time in the sun when feel like it. We've been doing that for ages.

[RRM]

Fumaric acid and vitamin D are created from direct sunlight exposure (reflection from snow and water will do the same job I guess).

All material reflects sunlight, but to very different extends.
Depending on the angle, water can reflect UV from 10% up to virtually 100%.
Metals seem to very effectively reflect UVB to a different extend. Aluminium most effectively (eg aluminized mylar), gold the least.
Also plastics, particularly acrylic plastics, seem to reflect UVB.
Here are some reflectancy numbers ('from a book about building greenhouses'):
white paint 80-90%
glass mirror 80-90%
polished aluminium 60-70%
aluminium paint 60-70%
stainless steel 55-65%

Cloud cover reduces UV levels, but not completely; you get burned on a cloudy day.
Wiki: "Vitamin D is produced when ultraviolet light of UVB type at wavelengths between 270 and 300 nm are present,
which is the case when the UV index is greater than three. (which hardly ever happens within the arctic circles).
Sunscreen with an SPF of 15 can reduce synthetic capacity of vitamin D by 98 percent. Matsuaka et al
Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.
UVB exposure induces the production of vitamin D in the skin at a rate of up to 1,000 IUs per minute.

It specifically says daylight, not sunlight. Somewhere else it says to avoid direct sunlight.
Daylight exposure is good for your serotonine metabolism; it doesnt require direct sunlight exposure.

I don't understand this advice at all...
Serotonine is surely not the only thing we get from the sun.

Vitamin D does not require direct sunlight exposure.
You can get all the required vitamin D from cloudy days or in the shade, as UVB is reflected by many surfaces.
Sunlight exposure accelerates aging of the skin, by destroying collagen, and damages retina in the eyes.
Wiki: An overexposure to UVB radiation can cause sunburn and some forms of skin cancer.
In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye, and immune system.
Moreover, UVC can cause adverse effects that can variously be mutagenic or carcinogenic.

Many studies show that you don't get healthy vitamin D levels from ingesting the RDA alone.

Can you give an example?

So I guess that the RDA is not only based on dietary vitamin D but also on UVB exposure.

Of course, because we all get some UVB exposure.

I found out that the RDA is based on limited sun exposure...
This makes me (and many vitamin D researchers) conclude that the RDA is not adequate.

Huh?
Please explain.
Sure, the RDA may not be not adequate if you never get any (in)direct sunexposure, but that is unrealistic.
Reality is that we all get at least limited UVB exposure, so we should start from there.

[overkees]

Did you read my post? I gave tons of examples of researches that experimented with dietary vitamin D above 1000 UI. So we must throw all these straight to the bin? I think dietary vitamin D has a lot of other helpful properties.

In the winter, people don't come outside, so reflecting surfaces or not, it doesn't help with vitamin D if you don't come outside. And it must be added that the 1000 UI made by sunlight is probably the whole body that is being used for its synthesis. Being packed with thick clothing and only your head to make vitamin D in winter will provide virtually no vitamin D.

That is why my advice is better safe than sorry and eat more than 600UI a day, especially in the winter, where I myself would eat more than 1000UI preferably

[Kasper]

Actually, we make no vitamin D in the winter, because UVB doesn't reach the Netherlands.
The sun needs to be above a 50 degree angle to allow penetration of UVB through the atmosphere.
UVB only reaches the netherlands between mid-april until mid-august.

You can check it here:
http://aa.usno.navy.mil/data/docs/AltAz.php

[RRM]

Did you read my post? I gave tons of examples of researches that experimented with dietary vitamin D above 1000 UI. So we must throw all these straight to the bin? I think dietary vitamin D has a lot of other helpful properties.

I did not say that high intakes may not have beneficial effects.
I am not disputing any health effects of vitamin D.

Being packed with thick clothing and only your head to make vitamin D in winter will provide virtually no vitamin D....
That is why my advice is better safe than sorry and eat more than 600UI a day, especially in the winter, where I myself would eat more than 1000UI preferably

Sure, you can do that.
Whether its really better is the question though.

[Kasper]

Many studies show that you don't get healthy vitamin D levels from ingesting the RDA alone.

Can you give an example?

http://www.pediatricsdigest.mobi/content/107/4/e53.full
This studies show that even in a sunny country, hypovitaminosis D is common in schoolchildren.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2729206/#B7
This study shows that width the RDA of vitamin D those (same) children didn't get desirable vitamin D levels.

Those studies are done in Beirut.
UVB reaches beirut between begin march until begin october.
Three months longer UVB exposure than for example the Netherlands.
So it is likely that in the Netherlands schoolchildren would need even higher levels of dietary vitamin D (or would need to spend more time in the sunshine) to get desirable vitamin D levels.

[Oscar]

Actually the second study is about giving vit. D3 supplements, and they conclude:

Conclusion: Vitamin D3 at doses equivalent to 2000 IU/d for 1 yr is safe in adolescents and results in desirable vitamin D levels.

However, what is a desirable vit. D level? It seems they go by the almighty RDA, or the Recommendations from the Institute of Medicine. As is the case with calcium, the method of determining supposedly (bone) health-promoting changes as a result from doses of supplemented vit. D is debatable, and may result in far too high recommendations (long-term implications are unknown).
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.

[RRM]

Many studies show that you don't get healthy vitamin D levels from ingesting the RDA alone.

Can you give an example?

This studies show that even in a sunny country, hypovitaminosis D is common in schoolchildren.

What officially constitutes hypovitaminosis D, does not necessarily reflect actual health.

Vitamin D toxicity is hard to achieve during rapid skeletal growth.
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.

Those studies are done in Beirut.
...So it is likely that in the Netherlands schoolchildren would need even higher levels of dietary vitamin D

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

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2729206/#B7
This study shows that width the RDA of vitamin D those (same) children didn't get desirable vitamin D levels.

It shows the results after 1 year of supplementation, not after a lifetime of adequate vitamin D intake through diet.
A big difference, because vitamin D levels are very much subject to control mechanisms (via estrogen, PTH, calcium),
so that any non-overwhelming supplementary intake may get largely compensated for, and maybe for a very good reason.

What are the desirable vitamin D levels?
Officially, hypovitaminosis D is prevalent in children and adolescents worldwide.
As the study acknowledges, "what constitutes an optimal D level for the younger subjects is more debatable"
As the study mentioned, those children were healthy.
No mentioning of poor (bone) health whatsoever.
No rickets, no osteomalacia, no secondary hyperparathyroidism, no bone loss, and no increased risk for fractures.
Regarding osteoporosis, bone-remodeling rates are telling.
At baseline bone-remodeling was not too high, and thus not subsequently corrected by vitamin D supplementation.
(Just a weak positive correlation between vitamin D and C-telopeptide cross-links levels,
and no correlation between vitamin D and osteocalcin and bone alkaline phosphatase)

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

substantial increments in lean mass, bone area, and bone mass, specially in girls who received high-dose vitamin D group, confirm that mean 25-OHD levels in the mid-30s may indeed be desirable in adolescents

So, its not about getting them healthier, but to increase their bone mass,
and thats what constitutes bone health in this view.