"Carotenoids" is the term which describes the large range
of more than 600 phytochemical pigments from which many
plants derive their characteristic red, orange or yellow
colourings. Those most commonly found in modern Western
diets are alpha-carotene, beta-carotene, lutein,
zeaxanthin, and lycopene.
Alpha and beta-carotene have traditionally attracted most
attention as they can be synthesised by the body to form
vitamin A, one of the body's most powerful anti-oxidants,
immune system boosters and infection fighters. More
recently lycopene has won substantial publicity as a
possible weapon in the battle against cancer, particularly
that of the prostate.
Like lycopene, neither lutein nor zeaxanthin are
"pro-vitamin A" active substances in the way that alpha and
beta-carotene are, but the evidence now indicates that they
also function as valuable fat-soluble anti-oxidants within
the body, and as such may be particularly important in
preventing free radical damage to the delicate but vital
fatty structures of the body's cells such as the membranes.
These fat-soluble anti-oxidants also help to prevent the
oxidation of low-density blood lipids (LDL), the so-called
"bad cholesterol", which is implicated as a major factor in
the development of cardiovascular disease.
But in addition to sharing the general health giving
anti-oxidant properties of carotenoids, lutein and
zeaxanthin have been highlighted for their role in
maintaining visual health, and particularly in protecting
against the principal causes of loss of vision in later
life, ie age-related macular degeneration (AMD) and
cataracts.
The macula is the centre of the eye's retina, and its
degeneration is the main cause of visual deterioration and
ultimately even blindness amongst the elderly in affluent
Western societies. Since lutein and zeaxanthin are the
only carotenoids found in the retina, particular attention
has been paid to their possible role in eye health, and it
appears that both may play a role in preventing oxidative
damage from blue and ultra-violet light, ie sunlight, in
the macula. Like every other structure in the body, the
cells of the retina are vulnerable to free radical damage
in the absence of sufficient anti-oxidants and research
published in the Journal of the American Medical
association in 1994 suggests a 43% reduced incidence of AMD
for those following a diet rich in lutein and zeaxanthin
anti-oxidants as against those whose diet was poorest in
these foods.
Lutein and zeaxanthin are likewise the only carotenoids
found in the lens of the eye, where ultra-violet light and
oxidative damage can cause the growth of the cataracts that
frequently obscure the vision of the elderly. Several
research studies have demonstrated that diets rich in
lutein and zeaxanthin, particularly dark green, leafy
vegetables, may reduce the incidence of cataracts by as
much as 25-50%.
Conventional medicine nevertheless continues to insist that
these findings may be due to elements in a lutein rich diet
other than lutein and zeaxanthin themselves, although
commonsense would seem to suggest that as these are the
only carotenoids present in these vital structures of the
eye, nature has probably put them there for a good reason.
The consumption of ample lutein and zeaxanthin requires the
consumption of a wide variety of vegetables, particularly
the dark, green leafy varieties which are the best dietary
source. So a cup of cooked spinach, for example, will
provide up to 30,000 mcg, kale around 25,000 mcg, collards
or turnip greens perhaps up to 20,000. Squash, peas,
sprouts, pumpkin and broccoli, amongst others, may also be
useful sources, but will provide rather lower quantities.
As with other carotenoids, the optimum absorption of lutein
and zeaxanthin requires the presence of dietary fat. But
this is not too tough to achieve so long as the required
vegetables are taken as part of a meal also including some
meat, particularly red meat.
Supplements containing either lutein, zeaxanthin, or a
combination of the two are readily available as an
alternative, the combination supplements normally
containing significantly more lutein than zeaxanthin. But
whilst conventional medicine has largely accepted the value
of a diet rich in these carotenoids in helping to ensure
continued eye health, it remains sceptical as to the value
of such supplementation. Alternative practitioners, of
course, admit to no such doubts and urge the benefits,
particularly for those with particular reason to fear the
onset of age related optical health problems.
And although such practitioners tend to recommend
supplements in quantities which ought to be easily
achievable through the consumption of a selection of the
foods listed above; it appears that many people are still
not managing to consume such a diet. This is evidenced by
the sad fact that around 25% of the over sixty-five age
group show some signs of AMD, and that several hundred
thousand people are blinded by it each year.
So as ever, the sensible and cost effective precaution
appears to be to combine supplementation with a normal
daily diet already well supplied with foods rich in lutein
and zeaxanthin.
----------------------------------------------------
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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