From: dyer@spdcc.com (Steve Dyer)
Newsgroups: rec.food.veg
Subject: Re: vegan sources: B12, D3 and iron
Date: 30 Aug 92 23:47:06 GMT
Article-I.D.: spdcc.1992Aug30.234706.4541
Organization: S.P. Dyer Computer Consulting, Cambridge MA

In article <altar.715205396@sfu.ca> altar@beaufort.sfu.ca (Ted Wayn Altar) writes:
>>>It is NOT a good idea to take B12 daily, simply because your
>>>ability to absorb B12 will decrease with such a surfeit of
>>>available B12.  The end result is that you simply become overly
>>>dependent on B12 supplements.
>>This is simply not the case.  There is no evidence that taking B12
>>causes a reduction un the ability to absorb it.
> 
>The trouble with stating things so emphatically and absolutely is
>that it would ignore the fact that even experts in this field
>cannot be so certain that a new paper, or one buried in a less
>obvious journal, doesn't provide evidence that you do baldly
>claim simply doesn't exist.  Can you really be so certain of
>these things?
>Now, all I have to do is simply cite one reference to refute your
>categorical statement, fair enough?
> 
>My reference, which I listed [Hunt & Groff, 1990], states:
>     "Absorption rate of the vitamin decreases with increased
>     intake.  At low levels intake, the mean absorption is 70%,
>     while at very high levels of intake, the absorption rate
>     drops to 16%" [p. 210]
 
I can't believe you think this is a refutation.

This is saying that the percentage you absorb is reduced as
you take more of it.  Nothing particularly surprising here.

However, it says nothing about your ability to absorb the vitamin;
that is, larger doses do not cause a lowering in B12 absorption if
your intake was lowered.

Tell me, Ted: do you understand the difference here?
Apparently not.

>Also, take a look at:
>     See K. McMahon (1987). Coline, an essential nutrient?  NUTR.
>     TODAY, 1:95-121.
 
It's spelled choline.  What's this got to do with B12?
 
>Not being a vegan, let alone even a vegetarian, you don't have to ;-)
 
What makes you think I'm not a vegetarian?
 
>Primary hemochromatosis affects about 8/1,000. most of these
>people having an identifiable genetically transmitted
>susceptibility.  Not many to be sure but we must remember that
>this figure only pertains to identified cases.  More would
>be unidentified (just as we find with diabetes II).  Professor
>J. Moon at sfu also suspects that even mild overload over many
>years may be making for some problems in men more frequent than
>previously suspected.
 
The rationale for widespread iron supplementation presumably is that
the public health benefits of such supplementation outweigh the risks
to a small number of individuals.  Healthy men are in no danger of
iron overload.

>>>Undesirable effects from niacin from overdoes via supplements
>>>include (1) release of histamine (2) possible injury to the liver
>>>(3) raising serum uric acid levels (4) dermatological problems
>>>(5) elevation of plasma glucose levels.
>>
>>This is talking about large doses of niacin, not niacinamide.
>>50-100mg+ of niacin will cause transient but harmless flushing.
> 
>Careful, histamine produced flushing may not only be
>uncomfortable but it can be VERY INJURIOUS to persons with asthma
>and/or peptic ulcer disease.

Flushing caused by niacin is, in fact, harmless, though it can be quite
disturbing if the person isn't expecting it.  This reaction is not caused by
histamine release but by local prostaglandin release in the skin.  Tolerance
to this effect happens rapidly, after only a few days.  Niacin, in doses
which act to lower blood lipids, is not given to individuals with peptic
ulcer or similar problems associated with hyperacidity.  This isn't due
to the flushing, however.  As far as I know, someone with asthma can be
prescribed niacin safely.

-- 
Steve Dyer
dyer@ursa-major.spdcc.com aka {ima,harvard,rayssd,linus,m2c}!spdcc!dyer
Newsgroups: rec.food.veg