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Health
food
stores are well-stocked with all kinds of
antioxidant pills and capsules. Magazines abound extolling the virtues
of vitamins C and E and beta-carotene. Just how important are
antioxidants? Can they prevent disease? In what foods do we find them?
Can we get too much of them?
Oxygen
is needed
for the metabolism of fat and carbohydrates
for energy. However, exceed oxygen molecules and other free radicals
that form as by-products of normal cellular reactions can cause damage
to cells if not inactivated. The body has a complex antioxidant defense
system to neutralize radicals and prevent cell damage and disease.
Aging and chronic diseases, such as heart disease and cancer, are
currently believed to result from damage caused by free radicals.
The
antioxidant
defense system of the body includes the
antioxidant vitamins E and C, and the carotenoids (pigments present in
colored vegetables and some colored fruits). Higher intakes of these
nutrients are associated with lower rates of cancer and cardiovascular
disease. Optimal levels of antioxidants are also needed for maintenance
of immune function. HA Finnish study reported that vegetarians had a
higher dietary intake of antioxidant nutrients and higher levels of
antioxidant enzymes than nonvegetarians.
The
oxidation of
LDL cholesterol is now commonly regarded as
important for atherogenesis. Vitamin E is especially effective in
protecting LDL from oxidation. Vitamin E also inhibits platelet
clumping so that blood clot formation is reduced. Vitamin E is found in
large quantities in whole grains seeds, nuts, and vegetable oils.
In
a Harvard study, tomatoes and strawberries were found
to be
effective against prostate cancer. The benefits of tomatoes were found
in both raw and cooked forms. Men who ate at least 10 servings a week
of tomato-based foods had 40% less risk of prostate cancer, while men
who ate 4 to 7 servings per week had a 22% reduced risk compared with
those eating less than 2 servings per week. Tomatoes are rich in
Iycopene, a red carotenoid pigment that has antioxidant activity.
Compromises
in
the function of the lens and retina of the eye
during aging are exacerbated by a lack of antioxidant vitamins and
diminished antioxidant enzyme capabilities. Increased antioxidant
intake from a diet rich in fruit and vegetables may provide the least
costly and most practicable means to delay cataracts. Furthermore, the
retina accumulates two carotenoid pigments, lutein and zeaxanthin,
obtained from green leafy vegetables. Evidence suggests that the
carotenoids, as well as vitamins E and C, help retard retinal damage
that leads to blindness.
Many
people have
decided to increase their antioxidant status
by ingesting vitamin E and C and beta-carotene supplements to reduce
their risk of disease. This practice is fairly safe since these
antioxidants have a fairly low toxicity. However, large scale
intervention studies involving the use of supplemental antioxidant
vitamins have produced mixed results. Some studies have indicated
benefits (such as less coronary artery disease with vitamin E
supplements) while others have failed to reduce cancer rates. Some
studies have even shown that antioxidant supplements may in fact
promote cancer. However, the antioxidant story is much bigger than just
these three nutrients.
In
addition to
the antioxidant vitamins they contain, whole
grains, nuts' fruits and vegetables also contain a wide variety of
flavonoids and other plant phenolics (such as ellagic, ferulic and
caffeic acids) that act as powerful antioxidants. The flavonoids also
extend the activity of vitamin C and inhibit blood clot forrnabon.
Grapes, strawberries, raspberries and nuts are rich in ellagic acid,
while oats, grapes, blueberries, soybeans and prunes are good sources
of ferulic and caffeic adds. The phenolic compounds in ginger have an
antioxidant activity even greater than vitamin E. Two recent European
studies have found that high intakes of flavonoids from fruits and
vegetables are related to low rates of heart disease and cancer.
Andrews
University
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