Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind, randomised, controlled trial

Abstract

In this double-blind, randomised, controlled trial, we investigated the effects of vitamin C and E supplementation on endurance training adaptations in humans. Fifty-four young men and women were randomly allocated to receive either 1000 mg of vitamin C and 235 mg of vitamin E or a placebo daily for 11 weeks. During supplementation, the participants completed an endurance training programme consisting of three to four sessions per week (primarily of running), divided into high-intensity interval sessions [4-6 × 4-6 min; >90% of maximal heart rate (HRmax)] and steady state continuous sessions (30-60 min; 70-90% of HRmax). Maximal oxygen uptake (VO2 max ), submaximal running and a 20 m shuttle run test were assessed and blood samples and muscle biopsies were collected, before and after the intervention. Participants in the vitamin C and E group increased their VO2 max (mean ± s.d.: 8 ± 5%) and performance in the 20 m shuttle test (10 ± 11%) to the same degree as those in the placebo group (mean ± s.d.: 8 ± 5% and 14 ± 17%, respectively). However, the mitochondrial marker cytochrome c oxidase subunit IV (COX4) and cytosolic peroxisome proliferator-activated receptor-γ coactivator 1 α (PGC-1α) increased in the m. vastus lateralis in the placebo group by 59 ± 97% and 19 ± 51%, respectively, but not in the vitamin C and E group (COX4: -13 ± 54%; PGC-1α: -13 ± 29%; P ≤ 0.03, between groups). Furthermore, mRNA levels of CDC42 and mitogen-activated protein kinase 1 (MAPK1) in the trained muscle were lower in the vitamin C and E group than in the placebo group (P ≤ 0.05). Daily vitamin C and E supplementation attenuated increases in markers of mitochondrial biogenesis following endurance training. However, no clear interactions were detected for improvements in VO2 max and running performance. Consequently, vitamin C and E supplementation hampered cellular adaptations in the exercised muscles, and although this did not translate to the performance tests applied in this study, we advocate caution when considering antioxidant supplementation combined with endurance exercise.

Figure 1. Numbers of endurance-trained and untrained participants in each group

Numbers of participants in tests and analyses applied. PGC-1α, peroxisome proliferator-activated receptor-γ coactivator 1 α; HSPs, heat shock proteins.

Figure 2. Percentage changes in plasma levels of vitamin C and E in the vitamin C and E group and the placebo group

A, vitamin C levels. B, vitamin E levels. Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule); #, difference between groups; *, within-group changes.

Figure 3. Percentage changes in plasma 8-iso-prostane in the vitamin C and E group and the placebo group

Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule); #, difference between groups; *, within-group changes.

Figure 4. Percentage changes in and the 20 m shuttle run test in the vitamin C and E group and the placebo group

A, changes in . B, changes in 20 m shuttle run. Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule); #, difference between groups; *, within-group changes.

Figure 5. Percentage changes in COX4 mRNA, COX4 (protein), HSP60 mRNA and HSP60 (protein) in the vitamin C and E group and the placebo group

A, COX4 mRNA. B, COX4 (protein). C, HSP60 mRNA. D, HSP60 (protein). Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule); *, within-group changes. Exact P-values denote tendencies for group differences.

Figure 6. Percentage changes in PGC-1α mRNA and PGC-1α in cytosol and nuclear fractions in the vitamin C and E group and the placebo group

A, PGC-1α mRNA. B, PGC-1α in cytosol. C, PGC-1α in nuclei. Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule); #, difference between groups; *, within-group changes.

Figure 7. Percentage changes in HSP60 and HSP70 levels in cytosol and nuclear fractions in the vitamin C and E group and the placebo group

A, HSP60 in cytosol. B, HSP60 in nuclei. C, HSP70 in cytosol. D, HSP70 in nuclei. Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule).

Figure 8. Percentage changes in CDC42 mRNA and MAPK1 mRNA in the vitamin C and E group and the placebo group

A, CDC42 mRNA. B, MAPK1 mRNA. Boxplots show maximum–minimum values, 25–75th quartiles, and medians. ●, outliers (Tukey's rule); #, difference between groups; *, within-group changes.