Original study found here: http://jp.physoc.org/content/early/2014/01/31/jphysiol.2013.267419.abstract
Vitamin C and E supplementation hampers cellular adaptation to endurance training in humans: a double-blind randomized controlled trial
In this double-blind, randomized, 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 vitamin C and 235 mg vitamin E daily or a placebo for 11 weeks. During supplementation, the participants completed an endurance training programme consisting of 3-4 sessions per week (primarily running), divided into high intensity interval sessions (4-6x4-6 minutes; >90% of maximal heart rate (HRmax)) and steady state continuous sessions (30-60 minutes; 70-90% of HRmax). Maximal oxygen uptake (VO2max), submaximal running, and a 20 m shuttle run test were assessed and blood samples and muscle biopsies were collected, before and after the intervention. The vitamin C and E group increased their VO2max (8±5%) and performance in the 20 m shuttle test (10±11%) to the same degree as the placebo group (8±5% and 14±17%, respectively). However, the mitochondrial marker cytochrome c oxidase subunit IV (COX4; +59±97%) and cytosolic peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1alpha; +19±51%) increased in m. vastus lateralis in the placebo group, but not in the vitamin C and E group (COX4: -13±54%, PGC-1alpha: -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 (p≤0.05, compared to the placebo group). 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 VO2max and running performance. Consequently, vitamin C and E supplementation hampered cellular adaptions in the exercised muscles, and although this was not translated to the performance tests applied in this study, we advocate caution when considering antioxidant supplementation combined with endurance exercise.
Isolates don't occur in nature. So when you eat something with vitamins, you're eating complexes which is the vitamin combined with other vitamins, minerals, and similar micro nutrients which occur together naturally and your body can use. When you take a whopping dose of ascorbic acid (SYNTHETIC Vit C--not true Vit C), the body is forced to use its own stores of nutrition to digest and assimilate it as the other co-factors are missing from the supplement. Food is the best supplement out there.