Antioxidants needed by exercising populations: Nutritionist
By Stephen Daniells, 14-May-2009
Related topics: Research, Antioxidants, carotenoids, Vitamins & premixes, Energy
& endurance

Conclusions that supplements of vitamins C and E may blunt the positive effects
of exercise are a "gross over extrapolation of the experimental findings", says
a nutrition expert.

German researchers have reported that antioxidant vitamins C and E may blunt the
positive effects of exercise, with respect to insulin sensitivity. Findings were
published in the Proceedings of the National Academy of Sciences.



Dr Rob Childs, nutritional biochemist for the Cervelo Pro Cycling Test Team, who
are currently competing in the Giro D'Italia, told NutraIngredients.com that the
study "forms part of popular trend claiming that antioxidants attenuate the
adaptive responses to exercise".

"The benefits provided by antioxidant supplementation provide key drivers for
their use by exercising populations."
Dr Rob Childs

The German study used a combination of 1,000 mg per day of vitamin C and 400 IU
per day of vitamin E, and investigated how insulin sensitivity was affected
following 85 minutes of exercise five days per week for four weeks. Participants
were both trained and untrained.


Responding to the findings, Dr Childs said: "Studies dating back to the 1980s
have shown that antioxidants reduce muscle damage, while more recent
investigations demonstrate that they can also improve both ventilatory and
exercise performance. Such effects are of particular relevance to exercising
populations."


Commenting on the design of the study, Dr Childs said it was unclear if the
subjects encountered the same absolute level of muscle fatigue during exercise
in the supplement and control conditions and hence stimulus for antioxidant
up-regulation. "Because of this, the reported `prevention of the `health
promoting effects of antioxidants' may be nothing more than an experimental
artefact," he said.


In addition, Dr Childs said that comments by the authors that antioxidants may
block many of the beneficial effects of exercise were a "gross over
extrapolation of the experimental findings on two levels".


"Firstly, the study only investigated the effects of two free radical scavengers
in a highly complex system involving hundreds of antioxidant compounds. This
makes it inappropriate to extrapolate the study findings to other antioxidants.


"Secondly the potential advantages provided by antioxidant supplementation for
attenuating muscle soreness and structural damage, while enhancing muscle
recovery and performance were not assessed.


"The benefits provided by antioxidant supplementation on these parameters
provide key drivers for their use by exercising populations," said Dr Childs.