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.
RRM wrote: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.
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.