the most important and most intensively studied of the B complex
vitamins. This group of vitamins is known as the B complex
because of their biochemical similarity and because of their
close interaction and interdependence in the performance of
their numerous vital functions. So the B complex vitamins are
commonly found together in various common food sources and, each
being water soluble, will also be excreted together from the
body. A deficiency in one of the complex is therefore almost
always accompanied by a corresponding deficiency in each of the
others.
But all of that said, the consequences of a deficiency are
different in the case of each individual vitamin, and
deficiencies of B12 are particularly associated with
cardiovascular disease, a type of anaemia, Alzheimer's disease
and other dementias, and depression.
Vitamin B12 is required for the body's manufacture of the
essential amino acid, methionine and its associated enzyme,
methionine synthase, an inadequate supply of which may lead to
an excess of homocysteine, a naturally occuring protein within
the body, which is well known to be associated with an increased
risk of cardiovascular disease.
But it is also now known that sufferers from Alzheimer's
disease are often found to have low levels of vitamin B12 in
their blood as well as the raised levels of homocysteine which
are also associated with more common vascular dementias. In fact
a number of studies have suggested that low B12 and high
homocysteine levels may as much as double the risk of
Alzheimer's.
Although conventional medicine remains reluctant to accept any
causal link, it might well seem to the "intelligent layman" who
takes an interest in these matters that such a link is more
likely than not. And this is particularly so when it is
remembered that vitamin B12 deficiency leads to a reduction in
the synthesis of methionine, which is known to be essential for
the methylation reactions which are in turn vital for the health
of nerve cells and neurotransmitters.
Research has also noted a strong associative link between
vitamin B12 deficiency and depression, that widespread and
disabling, but still poorly understood and defined condition. In
fact different studies have suggested that up to 30% of patients
with depression severe enough to require hospital admission may
be deficient in vitamin B12, and that elderly people found to be
deficient in the vitamin are twice as likely to suffer severe
depression as those with normal blood levels.
Again the conventional "wisdom" prefers to regard these
findings as an observational association rather than evidence of
a causal link. But it has been argued that such a link may be
due to B12's acknowledged role in the synthesis of methionine
and its associated enzymes, which are vital for the effective
performance of certain neurotransmitters whose absence is known
to be a factor in depression.
Evidently Alzheimer's disease, dementia and depression are all
conditions which become more common and more severe with
advancing age, so perhaps it should be no surprise that
deficiencies of vitamin B12 are also much more frequent in the
elderly population. In fact as many as 10 -15% of the over 60s
may be severely deficient, but a far higher proportion than this
are likely to fall below the threshold required for optimum
protection against these justifiably dreaded diseases.
However, these deficiencies are unlikely to be caused by an
inadequate dietary supply. The Recommended Dietary Allowance
(RDA) for vitamin B12 is only 2.4 mcg a day, an amount which
should be readily obtainable, except perhaps for those following
a strict vegetarian regime, given that a single 3 oz serving of
fish or red meat may provide this quantity. For those with a
taste for it, sea food may provide a great deal more, and
chicken, turkey, eggs, milk and cheese are also useful, though
less lavish, sources.
But good absorption of vitamin B12 from food is heavily
dependent on the normal stomach acid and digestive enzymes, the
quantity and effectiveness of which decreases substantially as
the body ages, and on the presence in the stomach of a
specialised protein known as Intrinsic Factor. The correct
action of Intrinsic Factor requires the presence of adequate
calcium in the body, another nutrient in which the elderly are
of course notoriously likely to be deficient.
Absorption of B12 from supplements is much less problematic,
however, because stomach acid and digestive enzymes are not
required to release the vitamin from its protein bindings. So
this is a rare case in which even conventional medical "wisdom"
recognises the value of supplementation, at any rate for the
over 50s.
So given that relatively small amounts of these vitamins are
required by the body, and that no toxicities or adverse side
effects have been reported, there really seems no reason to run
the risk of a deficiency.
About The Author: Steve Smith is a freelance copywriter
specializing in direct marketing and with a particular interest
in health products. Find out more at
http://www.sisyphus
