Vitamin C supplements may not improve athletic performance, a new study finds.
Certain vitamin supplements may blunt the muscle's natural response to endurance training, a new study from Norway suggests.
In the study, 54 healthy participants were randomly assigned to take vitamin C and E supplements, or a placebo, during an endurance training program that consisted of running three to four times a week.
Participants completed fitness tests and underwent a muscle biopsy at the beginning and end of the study to see how their bodies adapted to the training.
After 11 weeks, the muscles of the people in the placebo group had produced more mitochondria — "powerhouses" of the cells — a natural response to training. However, those in the supplement group did not see an increase. [7 Common Exercise Errors And How to Fix Them]
The findings suggest "vitamin C and E supplements blunted the endurance training-induced increase of mitochondrial proteins, which are needed to improve muscular endurance," study researcher Dr. Gøran Paulsen, of the Norwegian School of Sport Sciences, said in a statement.
Despite these cellular effects, the supplements did not appear to hurt participants' overall performance — both groups had similar improvements in their maximal uptake of oxygen, an indicator of endurance.
Still, Paulsen said, "our results indicate that high dosages of vitamin C and E — as commonly found in supplements — should be used with caution, especially if you are undertaking endurance training."
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