Re: Vit D supplementation can lower 1,25-(OH)2D levels.

[Guest guest]

Good find. Yup, it's always more complicated than we think at first

glance.

penny

" Mark London " <mrl@p...> wrote:

> http://www.nutrition.org/cgi/content/full/132/9/2644

> " Thus, during positive Ca balance, high vitamin D3 intake (as in the

> hVitD group) enhances 24-hydroxylase activity and results in enhanced

> production of 24,25(OH)2D3 and probably competitive inhibition of the

> synthesis of 1,25(OH)2D3 from 25(OH)D3. "

[Guest guest]

I agree with Penny, that is a good find. It has some very good info

and is much better than most of the junk studies on Vit. D. This one

actually measured the metabolites instead of making wild assumptions.

I also agree that things are always more complicated. The

usefullness of this study is limited by one quote:

" None of the factors regulating plasma 1,25(OH)2D3 and 24,25(OH)2D3

concentrations differed between groups except for vitamin D3

intake. "

If someone (ie. Bill, or myself) have levels of 1,25D that are well

above the population normal, then some regulating factors are

different. Untill researchers recognize that large populations of

chronicly ill, now shown in several diseases, have disregulated D

systems then little useful information will be forthcoming. Instead,

we are limited to trying to apply studies on healthy populations, or

studies which fail to measure the active metabolites (they assume

normal).

Unfortunately, Vitamin D publication is controlled by a very small

group. Anyone who has research (no matter how well done), which

disagrees with those few, are S.O.L. They will not pass peer

review, they will not be published.

Ken

>

> > http://www.nutrition.org/cgi/content/full/132/9/2644

>

> > " Thus, during positive Ca balance, high vitamin D3 intake (as in

the

> > hVitD group) enhances 24-hydroxylase activity and results in

enhanced

> > production of 24,25(OH)2D3 and probably competitive inhibition

of the

> > synthesis of 1,25(OH)2D3 from 25(OH)D3. "

[Guest guest]

Great points.

That's why there just doesn't seem to be any one-size-fits-all

answer out there. We're all somewhat different to begin with, and

sick people are definitely different from the healthy.

However, if we can at least determine which problems exist, i.e.

microbes, inflammation, d-dysregulation, secondary porphyria, etc.,

we're that much closer to understanding how to customize each of our

own personal answers. We definitely learn from each others'

experiences and experiments. (Boy, if not for this list, there'd be

so much I'd be completely in the dark about.)

But wouldn't it be nice if the experts would stop trying to make our

square pegs fit into all those round holes and actually see us as

individuals?

penny

> >

> > > http://www.nutrition.org/cgi/content/full/132/9/2644

> >

> > > " Thus, during positive Ca balance, high vitamin D3 intake (as

in

> the

> > > hVitD group) enhances 24-hydroxylase activity and results in

> enhanced

> > > production of 24,25(OH)2D3 and probably competitive inhibition

> of the

> > > synthesis of 1,25(OH)2D3 from 25(OH)D3. "