Vitamin C appears to have no benefit on exercise
despite public preconceptions, suggests a small US study.
Earlier research had showed that the vitamin reduced oxidative stress indicating a potential boost during exercise. But a team from the University of Colorado says that they found no improvements in real exercise capacity for young or old men and women, by either acute or long-term intake of ascorbic acid.
The physiologists gave vitamin C through an infusion to a group of 12 young adults, aged on average 23 years old, and 10 older (61 years old) adults just before exhaustive exercise on a treadmill. They also took a 500mg dose of the vitamin daily for one month prior to the tests.
The researchers predicted that "acute administration of ascorbic acid might improve/restore maximal aerobic capacity (MAC) and maximal cardiac output (MCO) in the sedentary older adults, thus creating the possibility that longer-term ascorbic acid supplementation could be used therapeutically to sustain the improvement".
But reporting in the 22 October online edition of the Journal of Applied Physiology (doi:10.1152/japplphysiol.00790.2004) the scientists write that "the age-associated decline in (MAC and MCO) is unaffected by acute or chronic administration (the supplements) of moderate daily ascorbic acid supplementation" for either men or women.
Lead researcher Christopher Bell said: <>"We did see a decrease in oxidative stress with large doses of vitamin C, but this decrease didn't improve aerobic abilities either for younger or older subjects."
The only major difference found throughout the experiment was that "irrespective of age, MAC, MCO and heart stroke volume were greater in men compared with women; however there were no sex-differences or age-sex interactions pertaining to the response of any of these variables to administration of ascorbic acid", said the researchers.
The study also showed that plasma concentration increased in all subjects following the acute but not chronic administration and that oxidative stress was reduced in both groups after acute administration.
Yet maximum stroke volume was similar in the older and young adults, and was unchanged after taking vitamin C.
According to Bell, the big difference in results came from the fact that in earlier studies some of the metabolic manifestations of exercise were chemically induced, while the current study actually tested the role of vitamin C in hard-exercising humans.
