Vitamin C and E supplements bad for running - stops production of new muscle mitochondria (endurance adaptation)?

From the article:

Participants were randomly allocated to one of two groups. The first group was required to take 1,000 mg of vitamin C and 235 mg of vitamin E each day, which the researchers say is consistent with the amount found in store-bought supplements. The second group received a placebo pill each day.

Results of the study revealed that markers for the production of new muscle mitochondria - structures that supply power to the cells - only increased in the participants who received the placebo pill.

The researchers note that the supplements had no impact on the participants' maximal oxygen uptake or their results in a 20-meter shuttle test.

The investigators hypothesize that since vitamins C and E are antioxidants, high doses may take away some of the oxidative stress and block the development of muscular endurance.

Here's another discussion on the topic:

https://www.ncbi.nlm.nih.gov/books/NBK299041/

Several studies have attempted to attenuate the inflammatory effects of exercise using antioxidant-rich supplements. A reduction in creatinine kinase and urinary 8-hydroxy-guanosine has been reported following pre-season supplementation with a blend of antioxidants and amino acids in collegiate soccer players (Arent et al. 2010). Although no performance benefit was demonstrated in the players, this could imply a possible recovery benefit. Acute supplementation of trained cyclists 4 h prior to an exercise trial with a pine bark extract, Pyconogenol®, increased time to exhaustion, maximal oxygen uptake and economy (Bentley et al. 2012). Another study which supports the theory of increased antioxidant capacity examined the impact of cherry juice supplementation compared with an energy-matched placebo on knee extension maximum voluntary contractions (Bowtell et al. 2010). Cherry juice supplementation substantially improved post-exercise recovery of isometric strength compared with placebo. Although this study is not specific to endurance athletes, the outcomes support the concept that improved antioxidant availability can delay time to fatigue and promote muscle recovery that potentially improves performance (Bowtell et al. 2010). Blueberry consumption prior to prolonged exercise (2.5 h of running) resulted in higher post-exercise NK cell counts and an increased concentration of anti-inflammatory cytokines compared with a control group (McAnulty et al. 2011).

Quercetin is one of the few antioxidant supplements that has been examined in a number of studies and demonstrated a consistent performance benefit; however, the studies have been conducted mostly using untrained subjects. In a study of running performance in a 12-min treadmill test, a substantial improvement was observed in untrained subjects (Nieman et al. 2010). In another study, maximal oxygen uptake and cycle time to fatigue were increased following 7 days of quercetin supplementation compared to placebo (Davis et al. 2010), again in untrained subjects. It is unclear whether this benefit would be seen in highly trained athletes.

A topic of much discussion in sport nutrition is whether the use of supplements may compromise natural physiological processes. Some researchers contend that antioxidant supplementation may interfere with cellular signalling function of ROS, and therefore prevent the adaptations that are necessary for performance improvements (Gross et al. 2011). An alternate view is that dietary supplements simply augment natural antioxidant capacities in the face of very high demands associated with endurance training and the fear of physiological interference is overstated. Further studies are needed to resolve this controversy.