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Could
Vitamin B12 Be The Secret Weapon in the Battle Against
Depression?
Vitamin B12, occasionally
also known as cobalamin, is one of 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.
Steve Smith