CAN VITAMIN E
SUPPLEMENTATION FORESTALL MUSCLE-DAMAGING EFFECTS OF A SINGLE BOUT OF
RESISTANCE TRAINING?
Vitamin E may enhance insulin production by the
pancreas; results being presented at a meeting on exercise and
physiology by international scientists during Olympics
PORTLAND, ME — Exercise has been shown to lead
to the formation of membrane-damaging oxygen free radicals. The damage
created by these free radicals has been associated with the loss in muscle
function and insulin sensitivity that intense exercise induces, says Bruce
Craig, Ph.D. Dr. Craig is a member of the Human Performance Laboratory at
Ball State University in Muncie, IN and will present his findings during the
American Physiological Society’s interdisciplinary meeting, "The Integrative
Biology of Exercise," being held September 20-23, 2000 in Portland, ME.
Background: Free radicals are unstable
and tend to react with the fats within the cell membrane. Vitamin E is a
fat-soluble vitamin that acts as an antioxidant; it is important in the
formation of red blood cells and has been shown to protect the cell membrane
against free radical damage. Its effectiveness has been demonstrated in
aerobic exercises like running, but has not been adequately tested with
anaerobic training, such as weight lifting.
Methodology: To determine if three weeks
of vitamin E supplementation could hinder the muscle-damaging effects of a
single bout of resistance training, Dr. Craig and his colleagues studied the
effect of short-term (21 days) vitamin E supplementation upon muscle
function and hormonal responses following a single bout of resistance
(weightlifting) exercise.
Eleven college-age male subjects were given
1200 IU of vitamin E or placebo capsules daily for 3 weeks. On day 15 the
subjects were given a 75 gm glucose (sugar) drink and blood levels of
glucose, insulin, and C-peptide (pancreatic-released hormone) were measured.
Muscle power tests (the time it takes to lift a weight) were performed on
day 16 and at 24 hours and 48 hours after the final weightlifting session.
On day 21, the subjects exercised by lifting weights, and 45 minutes later
were given a second glucose drink, followed by a re-testing of their muscle
power.
Results: Results of the study showed that
vitamin E significantly reduced the blood levels of creatine kinase, which
is an enzyme marker of membrane damage. Vitamin E intake also reduced the
formation of malondialdehyde, a blood marker of free radical formation. The
protective effects of vitamin E did not, however, influence muscle power or
strength. The glucose test performed on the subjects also demonstrated that
three weeks of vitamin E intake can significantly elevate hormonal responses
without influencing the body's ability to remove glucose from the
circulatory system.
Conclusions: The conclusions drawn from
this research suggest that vitamin E can significantly reduce the muscle
damage created by resistive training, and may enhance insulin production by
the pancreas.
While the researchers doubt that vitamin E has a direct
effect on pancreatic insulin release, they theorize that its ability to
stabilize the membrane may enhance the release mechanism. No data exists yet
to support the hypothesis, but it may be possible that vitamin E speeds the
interaction between insulin storage vesicles and the plasmalemma of the beta
cells. It is also possible that vitamin E makes the beta cell of the
pancreas more sensitive to glucose. Either way, says Dr. Craig, insulin
levels are elevated, which is important to non-insulin dependent diabetes
mellitus (NIDDM) patients who have a decreased sensitivity to insulin. Prior
research has shown improved insulin responses in NIDDM patients exposed to a
single bout of weight training. Further research on the effects of vitamin E
in diabetic subjects is planned.
From an athletic standpoint, Dr. Craig's research data
suggests that the disposal of post-exercise carbohydrate could be faster in
an athlete taking vitamin E. This would be a great advantage to athletes
trying to replenish post-exercise glycogen levels, and would be important
for athletes who have to compete over several days of competition.
***
Physiology research in exercise has
been responsible for demonstrating that women are physiologically capable of
running the marathon without the event being detrimental to their health and
well being; the necessity of competing in a hydrated state, seeking frequent
fluid replacement during endurance events; being acclimatized to heat before
competition; scheduling competition in the early or late hours of the day;
and providing fluids that contain a fixed concentration of glucose during
the long distance events; the advantages to athletes -- particularly
swimmers -- of tapering in their training before competition; the importance
of the specificity concept in athletic training schedules and the acceptance
by coaches of team sports (basketball and volleyball, among others) that
specific power and strength training principles must be followed to enhance
performance. The American Physiological Society is devoted to fostering
scientific research, education, and the dissemination of scientific
information. By providing a spectrum of physiological information, the
Society plays a significant role in the progress of science and the
advancement of knowledge.
Editor's Note: For further
information or to schedule an interview with Dr. Craig, contact Donna Krupa
at 703.527.7357; cell: 703.967.2751; or at
djkrupa1@aol.com; or visit the APS website at
www.the-aps.org.
