From: altar@beaufort.sfu.ca (Ted Wayn Altar)
Newsgroups: sci.med.nutrition
Subject: Re: Vitamin D (was Re: True Vegeterian - is it OK?)
Date: 9 Jan 93 19:59:26 GMT
Distribution: sci.med.nutrition
Organization: Simon Fraser University, Burnaby, B.C., Canada

mds5142@ultb.isc.rit.edu (M.D. Shepherd) writes:

>Vitamin D could be an another problem if one doesn't get
>>enough sunshine though the year.  But this is easy to
>>remedy by simply ensuring that one expose one's face
>>to the sun for about 15 mins. on average throughout
>>the year (less if you expose more of your body :-)  )
>
>Do you mean 15 minutes per day here?
>
Ideally, but it is certainly not necessary as one can store up a
supply that can sustain an adult for a considerable period
of time.

>
>I was curious what Vitamin D does for people?  What happens when
>it is lacking?

I guess most simply put, we can say that it is required for the
maintaining of calcium (and phosphorus) levels in the blood, and
it does this by enhancing the absorption of calcium from the
intestine and by helping to regulate the movement of calcium
between blood and bone.   In infancy and childhood, deficiency of
blood calciferol causes deformed bones characteristic of rickets.
In adults, chronic deficiency causes a softening of the bone
known as osteomalacia

The primary function of calciferol in the intestine, then, is
increased absorption of calcium and phosphorus via stimulating in
steroid fasion the production of calcium-binding proteins that in
turn are positively correlated (the exact role is not yet quite
understood) with Ca absorption/transport.  Other primary target
cells of vitamin D are those of the bone and kidney.  Here the
function of calciferol appears to be the stimulation of
transcellular transport of calcium across cell membranes.  It
also plays a major role in the parathyroid-directed mobilization
of calcium from bone and also in the parathyroid stimulation of
calcium absorption in the kidney.  Presently, all known functions
of this steroid pertain to calcium metabolism, but there is the
possibility that it also is involved in the functioning of
tissues not related to mineral metabolism.

Evidence is scanty that mineraliztion and bone grown are directly
affected by calciferol, rather, its influence is effected by
supersaturating the plasma with calcium and phosphorus.  It does
appear, however, to be directly involved in the modeling and
remodeling of bone via its stimulation of the number and activity
of osteoclasts (cells in bone marrow concerned with the
absorption of bony tissue during the formation of canals,
cavities, etc).  Since osteoclasts are derived from blood-born
precursor cells, calciferol is therefore capable of promoting
cell differentiation (studies on its stimulation on various tumor
cell lines supports this role of stem-cell differentiation and
growth).

It is also thought that calciferol serves to maybe regulate
various cellular processes in many cell types by altering
intracellular calcium.



>
>
>I live in Rochester, NY and probably don't get much Vitamin D
>this way since the sun rarely shows itself.  What other ways is
>there to get Vitamin D (food, etc.)?
>
Mike, you have a much easier time than us Canadians :-)
Even on an overcast day, however, your skin can still produced
"vitamin" D, albeit more slowly.

Yes, calciferol is added to most (80%) of the milk supply in the
US, but there is opinion that the better way to obtain your
supply of this steroid hormone is by producing it yourself via
some exposure to ultraviolet light.(see Moon et al. 1992.
"Etiology of Atherosclerosis and Osteoporosis:Are Imbalances in
the Calciferol Endocrine System Implicated?"  JOURNAL OF THE
AMERICAN COLLEGE OF NUTRITION, 11:567-583.)

There is good article in Scientific American, (Dec. 1970) by
W. Loomis who then said:

    The discovery of the cause and cure of rickets is one of
    the great triumphs of biochemical medicine, and yet its
    history is little known.  Indeed, it is so little known
    that even today most textbooks list rickets as a
    dietary-deficiency disease resulting from a lack of
    "vitamin D".  In actual fact RICKETS WAS THE EARLIEST
    AIR-POLLUTION DISEASE"  (emphasis mine)

The plain fact of the matter is that rickets is NOT caused
by a poor diet, as are all the other nutritional diseases,
but as Loomis says, by a "deficiency of solar ultraviolet
radiation"!

Solar ultraviolet may be blocked by many means, including
the industrial smog in London and the sunless alleys of
Wezlar.  In London as early as 1888 even the London zoo
animals -- chimpanzees, lions, tigers, bears, deer, rabbits,
lizards, ostriches, pigeons, and many more other species --
showed unmistakable signs of rickets.  Yet at that time a
little distance away in Dublin, Manchester, animals were
being raised without rickets.

Wezlar was a German Town of only 8,000 with exceptionally
narrow streets and dark alleys and consequently was infamous
in the early 19th century for its high rate of rickets.  The
children simply spent almost all of their life indoors and
rarely saw direct sunlight.  It is of course not surprising
that rickets become a major problem in such towns.

For centuries folk custom had taught northern European
mothers to put their infants out of doors even during
January for some "fresh air and sunshine".  Heck, I remember
my mother also trying to get me out of the house because I
needed some "fresh air and sunshine"  :-)   The problem,
however, occurred as the Europe became industrialized and
cities became highly polluted and over-crowded, making for
narrow streets dark streets and literally a blackened sky.
The old folk remedy was no longer effective due to human air
pollution plus poor urban design and overcrowding.

While we are used to the notion of nutritional deficiencies
and worry maybe unduly about suffering from such
deficiencies, to think in terms of an "ultraviolet light
deficiency should be equally important.

Now, this is maybe a sensitive issue, but the impact of
ultraviolet irradiation on vitamin D in different racial
groups is quite marked.  For instance, 44% of the
ultraviolet light is transmitted through to the active part
of the skin in whites, but in blacks this value is only 3%
The reason why this might be a sensitive fact is that the
lunatic fringe bigot would argue that "nature" didn't intend
Blacks to live at northern latitudes.  But in point of fact
rickets and osteomalacia are not problems among, say,
British immigrant Black West Indians as it is among
Glaswegian Asians or some Canadian East Indians.  The reason
is simply differing cultural life-styles that while quite
advantageous or appropriate in one latitude are not so
advantageous in another.  Asian girls tend to be more
protected, more housebound and suffer the further exclusion
of a less yearly intense Northern sunlight by way of their
national dress.  Hence, it is a COMBINATION of climatic,
cultural, genetic and metabolic effects that act together to
precipitate this problem.  In Britain, the solution was to
supplement chapati flour with vitamin D.  This is better
than supplementing the entire flour supply, or the entire
milk supply and margarine supply as it is done
indiscriminately here in Canada.

I think we need choice on this issue.  If certain groups are
at risk due to their genetics and lifestyle, then by all
means they should have easy delivery of supplementation, but
to require the whole population to consume calciferol when
only a relatively very few need it, is simply rash when
alternative delivery methods to groups at high risk are
possible and when new evidence is coming in linking
calciferol with, atherosclerosis, osteoporosis and cancer.

                                        ted


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