Contact: Mayer Resnick
Office: 301-634-7209
Cell: 301-332-4402
[email protected]
Green Tea Extract Boosts Exercise Endurance 8-24%
Dose-related improvement utilizes
fat as energy source
BETHESDA, Md. (Jan. 27, 2005) � Now that even baseball
players may need to seek new, more natural performance aids, will Japanese
green tea sets become standard in dugouts and athletic training tables
around the world?
A new study tested the effect of regularly taking green
tea extract (GTE) and found that over 10 weeks, endurance exercise
performance was boosted up to 24% with 0.5% GTE supplementation, and 8% with
0.2% by-weight addition to food.
Reporting in the online edition of the American
Journal of Physiology-Regulatory, Integrative and Comparative Physiology
researchers at the Biological Sciences Laboratories of Kao Corp., Tochigi,
Japan, said the 8-24% increase in swimming time-to-exhaustion was
�accompanied by lower respiratory quotients and higher rates of fat
oxidation.�
The results �indicate that GTE is beneficial for
improving endurance capacity and support the hypothesis that the stimulation
of fatty acid utilization is a promising strategy for improving endurance
capacity,� according to the study entitled, �Green tea extract improves
endurance capacity and increases muscle lipid oxidation in mice.� Research
was conducted by Takatoshi Murase, Satoshi Haramizu, Akira Shimotoyodome,
Azumi Nagasawa and Ichiro Tokimitsu, working at Kao Corp., a Japanese maker
of healthcare products, including green tea beverages.
Results came from the equivalent of about 4 cups of
tea a day
Although it�s difficult to extrapolate from mice eating
GTE as a food supplement to a major leaguer or Olympic swimmer sipping green
tea, the study�s lead author, Takatoshi Murase said: �We estimate that an
athlete weighing 75 kilograms (165 pounds) would have to drink about four
cups (0.8 liter) of green tea daily to match the effect in our experiments.�
�One of our important findings,� Murase pointed out,
�was that a single high-dose of GTE or its active ingredients didn�t affect
performance. So it�s the long-term ingestion of GTE that is beneficial.� (Murase
based his calculations of mouse-to-human tea/GTE consumption equivalents on
work his lab is doing on the anti-obesity effects of GTE on mice and
humans.)
In an era when professional and amateur athletes are
always looking for ways to improve performance, and most people want to
improve their health and exercise capabilities, �the efficacy of dietary
interventions is still controversial,� the authors acknowledge. They note
that green tea and cacao contain a class of polyphenols called catechins,
which consist mainly of epigallocatechin gallate (EGCG), epicatechin gallate
and gallocatechin gallate. Catechins have been reported to have various
physiological and pharmacological properties over the years.
The Kao lab �recently demonstrated that the long-term
consumption of tea catechins was beneficial in counteracting the
obesity-inducing effects of a high-fat diet, and that their effects may be
attributed, at least in part, to the activation of hepatic lipid catabolism�
in mice. �Overall,� the authors said, �observations so far suggest that
thermogenesis and fat oxidation are stimulated by the intake of catechins.�
Working hypothesis and study methods
�To confirm our hypothesis that catechins affect
endurance exercise capacity (i.e. time to exhaustion) by increasing lipid
utilization, in this study we examined the effect of catechin-rich GTE
intake on the endurance capacity of Balb/c mice swimming in an
adjustable-current water pool. We also analyzed changes in energy
metabolism, especially lipid metabolism. We demonstrated that GTE intake
improved endurance capacity and this was accompanied by an increase in lipid
catabolism. Our results support the hypothesis that stimulation of lipid
metabolism is a promising strategy for improving the capacity for endurance
training.�
The ideas for the experiment come from the fact that
�skeletal muscles utilize carbohydrates, lipids and amino acids as energy
sources, but the ratio in which they are used varies with the intensity of
exercise and the level of fitness� as well as the type of exercise involved.
For instance �during endurance exercise, excess glucose is undesirable
because it induces insulin secretion, which in turn simultaneously inhibits
lipid metabolism and stimulates lactate production. Conversely, enhanced
availability and utilization of free fatty acids are considered to reduce
carbohydrate utilization, which in turn spare glycogen and suppresses
lactate production and results in an increase in endurance.�
To test what effects GTE and its components would have
on endurance exercise, the researchers ran two experiments. In the first,
swimming endurance capacity was measured at eight weeks of age and the mice
were divided into four groups of 10 each. All subjects had unlimited access
to water for exercise. For 10 weeks, controls ate a standardized diet only,
while experimental animals had this diet supplemented with 0.2% and 0.5% GTE
by weight. During this period experimental mice were exercised in a pool
twice a week, but non-exercise mice weren�t.
The second experiment was similar to the first but the
experimental groups received a diet containing 0.1% to 0.5% EGCG for 10
weeks.
At the beginning of the experiment, the mice swam about
26 minutes until they were exhausted. After 10 weeks on the training
regimen, the time-to-exhaustion for the exercise-control mice (no GTE or
EGCG supplement) rose to about 33 minutes, showing the effects of unaided
practice on endurance capacity. From the first week of the experiment, the
mice on GTE showed greater improvement compared with the exercise-controls.
By week eight, the improved performance of mice on 0.5% GTE was
significantly better (39 minutes) than the exercise-controls (33 minutes) at
a 0.05 level, while improvement in weeks 9 and 10 (40 minutes vs. 33
minutes) were significant at the 0.01 level.
GTE effects not matched by EGCG alone suggesting
other additional influences
In the global search for enhanced athletic performance
(and health and fitness), the Kao team said they �have shown that GTE
improved endurance capacity and that the improvement was dose-dependent. A
similar effect was observed in mice fed EGCG, a major constituent of GTE,
suggesting that the effects of GTE were mediated at least in part by EGCG.
�However, because the effects of EGCG appear weak
compared with those of GTE, we cannot rule out a possible contribution from
other components of GTE. Although long-term intake of GTE enhanced endurance
capacity, no marked effects were observed after a single dose of GTE,
suggesting that some biochemical changes induced by habitual GTE intake,
such as up-regulation of muscular beta-oxidation, contributed to the
improvement in endurance capacity.�
The study found that plasma NEFA (non-esterified fatty
acid) measured immediately after exercise slightly, but significantly,
increased in mice fed tea catechins. Though they concede that the effect of
plasma fatty acid level on endurance capacity is controversial, they say
that increased supply of circulating fatty acids would �induce the uptake of
fatty acids, and thereby stimulate lipid metabolism in muscle.�
Indeed, lab results showed that muscular beta-oxidation
was higher in GTE-fed mice (compared with non-exercise and exercise-control
mice), �suggesting that GTE enhanced the capacity of muscle to catabolize
lipids and utilize fatty acids as an energy source.� Conversely, GTE lowered
plasma lactate concentrations, which would be raised by glycogen breakdown
and glycolytic flux, they note.
Taken together the experimental results �suggest that
habitual exercise and the intake of GTE enhance fatty acid availability,
catabolism and utilization in muscle, and this is accompanied by a reduction
in carbohydrate use, which together result in prolonged swimming times to
exhaustion.�
Controlling for caffeine
Kao researchers controlled for possible influences of
caffeine and possible weight-fat changes that might affect buoyancy.
Aware that previous studies were criticized by the
possible role of caffeine on fatty acids and exercise, the Kao researchers
reduced the amount of caffeine in supplements. �In addition, we observed no
changes in plasma NEFA level under resting conditions, suggesting that
caffeine-stimulated lipolysis did not occur under these conditions. Thus our
results overall suggest that the effects observed in this study are not
attributable to caffeine. In particular, our findings that purified EGCG
improved endurance capacity supports this conclusion.�
Next steps
-
The �precise molecular mechanism by which GTE
stimulates fatty acid metabolism is unclear at present (and) remains to be
elucidated.�
-
For instance, the researchers wrote, �it is possible
that the anti-oxidant properties of tea catechins mediate their effects on
endurance capacity.�
-
And finally they noted: �Although the clinical
efficacy of GTE has not yet been confirmed in human studies, our results
suggest that GTE may be a useful tool for improving endurance capacity.�
Source and funding
The study, �Green tea extract improves endurance
capacity and increases muscle lipid oxidation in mice,� was conducted by
Takatoshi Murase, Satoshi Haramizu, Akira Shimotoyodome, Azumi Nagasawa and
Ichiro Tokimitsu, appears in the online edition of the American Journal of
Physiology-Regulatory, Integrative and Comparative Physiology, published by
the American Physiological Society.
All researchers work at the Biological Science
Laboratories of Kao Corp., Tochigi, Japan, which makes healthcare products,
including green tea beverages.
Editor�s note: A copy of the research paper by
Murase et al. is available to the media. Members of the media may obtain an
electronic version and interview members of the research team by contacting
Mayer Resnick at the American Physiological Society, 301.634.7209, cell
301.332.4402 or
[email protected].
* * *
The American Physiological Society
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