Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial.
Level 2 - randomized trial
Double-blind randomized controlled trial in humans
PubMed 24492839 · doi:10.1113/jphysiol.2013.267419
What was done
Fifty-four young men and women were randomly allocated in a double-blind design to receive daily supplementation of either vitamins C (1000 mg) and E (235 mg) or a placebo for 11 weeks. Participants engaged in an endurance training program (3–4 sessions per week of running, consisting of high-intensity intervals at >90% HRmax and steady-state sessions at 70–90% HRmax). Maximal oxygen uptake (VO2 max), submaximal running, and a 20 m shuttle run test were evaluated, alongside blood samples and vastus lateralis muscle biopsies before and after the training period.
What was found
Both groups achieved similar gains in VO2 max (8 ± 5% in the antioxidant group vs. 8 ± 5% in placebo) and 20 m shuttle run performance (10 ± 11% vs. 14 ± 17%). However, vastus lateralis mitochondrial marker cytochrome c oxidase subunit IV (COX4) increased by 59 ± 97% in the placebo group but fell by -13 ± 54% in the antioxidant group (P ≤ 0.03 between groups). Cytosolic PGC-1α increased by 19 ± 51% in placebo versus -13 ± 29% with antioxidants (P ≤ 0.03). Messenger RNA levels of CDC42 and MAPK1 were also significantly lower in the trained muscle of the vitamin C and E group compared to placebo (P ≤ 0.05).
Why it matters
High-dose antioxidant supplementation can actively blunt exercise-induced signaling pathways essential for mitochondrial biogenesis in skeletal muscle, suggesting caution when using antioxidants during endurance training.
Limits
The study was limited to a small sample (n = 54) of young healthy individuals over an 11-week period, which may not capture longer-term performance consequences. Inter-individual variance in molecular markers was wide, and dietary antioxidant intake outside the intervention was not reported in the abstract.
Cited by
- supports High-dose combined vitamin C and vitamin E supplementation has been shown to blunt exercise-induced physiological adaptations.