Substrate utilization and work efficiency during submaximal exercise in vitamin C depleted-repleted adults.
A placebo-controlled, depletion-repletion protocol was utilized to examine the effect of vitamin C status on substrate utilization during a 90 min walk at 50% maximal oxygen consumption (VO2max). Nine vitamin C depleted subjects (plasma vitamin C < 28 mumol/L) agreed to participate in the 5-week study (aged, 27.6 +/- 2.5 years, mean +/- SE; 5 females, 4 males). Subjects were apparently healthy but unaware of their vitamin C status. Prior to the experimental period, VO2max was measured using open-circuit spirometry during a graded walking protocol. Subjects ingested a placebo capsule daily during weeks 1-3 and a 500 mg vitamin C capsule daily during weeks 4-5 of the experimental study. Mean plasma vitamin C rose nearly 3-fold and mean plasma carnitine fell by nearly 20% at repletion (week 5) versus depletion (week 3). At the end of weeks 3 and 5, subjects completed a 90 minute treadmill walk at an exercise intensity of 50% VO2max. The relative contribution of fat utilized for energy during walking did not differ in the vitamin C depleted versus repleted states. However, work performed by subjects and gross efficiency during exercise increased significantly at repletion versus depletion (10% and 15%, respectively). These data indicate that vitamin C depletion is associated with reduced work efficiency during submaximal exercise.
Johnston
C S
CS
Department of Family Resources and Human Development, Arizona State University, Temple 85287, USA.
Swan
P D
PD
Corte
C
C
D000328:Adult; D001205:Ascorbic Acid / Q000008:administration & dosage* / Q000097:blood; D001206:Ascorbic Acid Deficiency / Q000378:metabolism*; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D050356:Lipid Metabolism; D008297:Male; D009752:Nutritional Status; D010101:Oxygen Consumption; D010919:Placebos
D010919:Placebos; D001205:Ascorbic Acid