Antioxidants
Contributed By: Dick
Raford, MD from cyclingforums
Over
the last few years, we have been hearing more and
more about antioxidants - vitamins (C, E, and beta
carotene) that neutralize dangerous compounds known
as free radicals. Although the focus of much of the
discussion has been on cardiovascular health, there
has been a suggestion that free radicals may
contribute to a slow recovery after tough rides.
What
is a free radical? It is a molecule with an unpaired
electron, and a normal by product of all biologic
systems (exercising or not). These free radicals
are unstable and can produce cellular damage such as
lipid peroxidation (damage of lipid membranes) and
changes in membrane protein structure - both of
which have been suggested as possible culprits in
the development of heart disease and cancer. An
antioxidant, as the name suggests, can neutralize
free radicals before they interact with living
tissue, detoxifying them into water and oxygen.
A
review of studies on the role of anti-oxidants in
exercise suggests that although exercise does
increase the rate of lipid peroxidation (the
formation of free radicals), there is also a rise in
the natural antioxidant activity in the blood. And
with regular training, the antioxidant defense
system increases even further. There is little data
as to which has the upper hand in this balancing act
- the free radicals or the defenses. There has been
speculation that the "weekend warriors"
who do not have a regular training program, might be
more susceptible to free radical damage. However,
there is no convincing evidence that supplements of
antioxidants are of any value in counteracting the
potential effects of free radicals, for either
competitive cyclists or recreational exercisers.
One
study suggested that the use of antioxidants in the
form of vitamins C, E, and beta carotene decreased
muscle damage in a group of runners as compared to a
control group, and there are numerous anecdotal
reports that vitamin C taken before a ride
diminished the amount of muscle soreness the next
day. The only controlled studies were with 600 IU of
vit E for 2 days before exercise (no effect) and a
second with 3 grams of vit C per day for 3 days
before and 4 days after an exercise bout (reduced
soreness). However, none have suggested a
positive effect of any of the antioxidant
vitamins on actual exercise performance or
the rate of postexercise recovery in athletes on a
balanced diet.
There
is considerable speculation on the long term
benefits of antioxidants in general. A study of
nurses and male professionals published in 1993
demonstrated a lower rate of heart disease in those
taking Vit E supplements. And a study from China
indicated that the use of a multivitamin, containing
antioxidants among other things, lowered the cancer
death rate by 13%. However a more recent study
(1996) indicated the opposite, that patients at risk
for lung cancer had a HIGHER cancer rate if they
took beta carotene supplements, and the study was
terminated early because of those results.
How
about antioxidants in cardiovascular disease - an
area where there has been considerable interest and
research? The most recent study demonstrated no
benefit of antioxidants over placebo in blunting the
effect of atherosclerosis, and indeed even
suggested some harm in that antioxidants appeared to
blunt the effectiveness of a proven therapy (simvastatin-niacin).
As an aside, there has been interest in the benefits
of other vitamins (B vitamins and folate) in the
treatment of coronary artery disease - via their
effect on homocysteine metabolism. The evidence is
strong enough that one of my cardiology partners
routinely puts his post angioplasty patients on a
multivitamin plus an additional 400 mcg of folic
acid and 50 mg of vitamin B6.
The
bottom line is that very little evidence to support
the short term benefit of antioxidants for the
competitive athlete - and plenty of controversy
remains as to the long term health benefits.
Although there is no evidence that they will do you
any harm in the usual doses, megadoses have been
reported to have side effects and actually decrease
optimum physical performance.
As
there is general agreement that the natural sources
of these micronutrients appear to be more effective
than the vitamins you can buy in a bottle,
increasing the fruits and vegetables in your diet
might be a good compromise if you feel you'd like to
give them a try. And if you opt to go with
reasonable doses of vitamin supplements, only your
pocketbook would appear to be at risk.
- Vit C
- Food
sources:
citrus fruits, potato, broccoli, cauliflower,
cabbage, watermelon, cantaloupe
- RDA:
60
mg/day - 1 orange, 1/2 cup broccoli
- Supplement:
250-500 mg/day
- Warnings:
More than 500 mg can cause diarrhea
- Vit E
- Food
sources:
vegetable oil, nuts, wheat germ, margarine,
seeds, leafy greens, asparagus
- RDA:
8-10 mg/day (4-5 oz of peanuts)
- Supplement:
200-800 IU
- Warnings:
No serious side effects in the doses
recommended
- Vit A
- Food
sources:
milk, cheese, egg, liver, fish oil
- RDA:
800-1000 micrograms
- Supplement:
None; your body will convert B Carotene safely
into Vit A
- Warnings:
Toxic (even lethal) at high doses
- Beta carotene
- Food
sources:
carrots, cantaloupe, squash, sweet potato,
spinach
- RDA:
None, but 5 - 6 mg are suggested (1/2 carrot)
- Supplement:
6-15 mg per day
- Warnings:
Not toxic but in high doses your may turn
yellow (carotenemia)
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