First isolated in the 1930s, vitamin B6 is a highly water
soluble vitamin of vital importance to human health. An
adequate dietary supply is essential because the vitamin
cannot be manufactured by the body, and is required for the
proper action of more than 100 enzymes involved in vital
biochemical reactions.
Amongst its many functions, in its coenzyme form of
pridoxal 5'-phosphate (PLP), vitamin B6 is critical for the
release of energy within the body, for the proper formation
and function of oxygen carrying red blood cells, and for
the synthesis of neuro-transmitting hormones within the
brain.
There is also some evidence that PLP may play a role in
mitigating the potentially harmful effects of the steroid
(sex) hormones, such as oestrogen and testosterone, within
the body, so that levels of vitamin B6 may even be related
to the incidence of the characteristic cancers eg of the
breast and prostate, which are most strongly associated
with the hormones.
Perhaps most important, however, is vitamin B6's role in
the regulation of the protein, homocysteine, even sightly
raised blood levels of which have been repeatedly
identified as a risk factor for cardiovascular disease and
stroke. Homocysteine is a perfectly normal by-product of
the body's digestion of protein foods and should normally
be removed harmlessly from the body. But the risk of
excess build up is not negligible.
A large 1997 European study of young and middle aged adults
showed a more than doubled risk of cardiovascular disease
and stroke for individuals whose blood homocysteine levels
were in the top fifth of the normal range. And some
sources attribute as many as 10% of heart attack fatalities
and an even higher proportion of stroke deaths directly to
high homocysteine levels. Since these are still two of the
biggest causes of premature death in the affluent Western
world, such figures are particularly alarming.
The B vitamin complex is known to be vital for the
prevention of excess homocysteine. Vitamins B12 and folic
acid operate to convert homocysteine into the vital amino
acid, methionine; whilst B6 in the form of PLP converts it
into another amino acid, cysteine.
Not surprisingly then, research studies have demonstrated a
clear link between low intakes of vitamin B6, higher levels
of blood homocysteine and enhanced risk of cardiovascular
disease. One such study, in particular, showed that the
daily consumption of 4.6 mg of vitamin B6 reduced the
incidence of heart disease by more than a third as compared
with the consumption of 1.1 mg (slightly below the 1.3 mg
Recommended Dietary Allowance (RDA) for adults under 50).
In addiition to its important role in regulating blood
homocysteine levels, there is also good evidence to
associate vitamin B6 with the proper functioning of the
immune system and indivduals deficient in B6 have been
shown also to have reduced numbers of vital immune system
cells. It is notable, too, that the amounts of vitamin B6
required to restore optimum immune function, particularly
in the elderly, have been shown to be well in excess of the
RDA. Other benefits of vitamin B6 for which there is
some research evidence include improved memory, reduced
incidence of kidney stones, the alleviation of
pre-menstrual syndrome, the side effects of the
contraceptive pill and morning sickness in pregnancy.
Severe deficiencies of vitamin B6 are thought by most
conventional medical sources to be highly unlikely in
Western societies and indeed the following food values
would suggest that the RDAs of 1.3 mg for adults and 1.7 mg
for the over 50s should be easily achievable. A cup of
fortified cereal will provide between 0.5 and 2.5 mg and
even a single banana perhaps as much as 0.4 mg. Meat,
particularly poultry such as chicken and turkey, will
provide up to 0.5 mg per 3 oz serving, as will fish.
Vegetables, especially potatoes, and nuts are also useful
sources.
But despite this wide range of possible sources, surveys
have shown that the typical adult's daily intake of B6 is
only around 2 mg per day, and for older individuals this
reduces to 1- 1.2 mg. Both figures are worrying, because
they suggest not only that many older people are falling
below the RDA, but that many younger adults are perilously
close to doing so. It has to be remembered, too, that the
RDAs are in any case at levels only sufficient to avoid
outright deficiency, which is not at all the same thing as
optimum health.
Being water soluble, vitamin B6 is easily excreted from the
body and the consumption of alcohol and other diuretic
drinks such as tea and coffee may dramatically increase the
body's need for the vitamin. The requirement also
increases in line with the amount of protein consumed in
the diet.
For these reasons, even conventional medicine is inclined
to recognise the value of supplementation with B6 up to a
level of 2 mg per day. Some nutritional therapists,
however, recommend doses of as much as 100 mg a day in view
of B6's significant role in combatting the increased risk
of heart disease and stroke attributable to elevated blood
homocysteine levels.
And indeed there are no known toxic effects of vitamin B6
at this level of intake, which is in fact the upper safe
limit recommended by the US Food and Nutrition Board. As
always with the B complex vitamins, however, their close
interdependence means that such doses should only be taken
as part of a supplement containing the whole complex. And
to enable the vitamins to do their work to maximum effect,
a comprehensive multi-mineral supplement is also highly
recommended.
----------------------------------------------------
Steve Smith is a freelance copywriter specialising in
direct marketing and with a particular interest in health
products. Find out more at
http://www.sisyphuspublicationsonline.com/LiquidNutrition/In
formation.htm
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