Antioxidants
are widely used as supplements in the general population and
among sportspeople, due to observations that high concentrations
of ROS damage proteins, nucleic acid and other cellular compounds
[16,17]. More than 50% of elite endurance athletes in the
United States report taking dietary supplements daily [11], while
41% of the general population take multivitamins [17], typically at
much higher doses than recommended daily allowances. Vitamins
C and E are the most prevalent single vitamin supplements, with
approximately 20% of the population reported to use vitamin C
and/or E [18,19]. Given the popularity of vitamin C and E supplementation,
further studies are required to clarify if they can exert
inhibitory effects on the adaptive response to endurance training
in humans.