Marginal vitamin C status is associated with reduced fat oxidation during submaximal exercise in young adults.
Level 2 - randomized trial
Double-blind, placebo-controlled interventional trial following a cross-sectional assessment
PubMed 16945143 · doi:10.1186/1743-7075-3-35
What was done
Fat energy expenditure was measured during a 60-minute submaximal treadmill test in 22 young adults with either marginal (n = 15) or adequate (n = 7) vitamin C status. Subsequently, 8 participants with marginal vitamin C status completed an 8-week double-blind, placebo-controlled depletion-repletion trial evaluating daily supplementation with 500 mg vitamin C versus placebo during submaximal exercise testing.
What was found
Participants with marginal vitamin C status oxidized 25% less fat per kg body weight during the treadmill test compared to those with adequate status. Fat oxidation during exercise was inversely correlated with fatigue (r = -0.611, p = 0.009). In the intervention phase, 500 mg/day vitamin C repletion increased fat energy expenditure during exercise 4-fold compared to depleted controls (p = 0.011).
Why it matters
These findings suggest that suboptimal vitamin C intake directly impairs fatty acid oxidation during exercise, identifying a potential metabolic mechanism linking low vitamin C status with elevated adiposity and difficulty losing weight.
Limits
The total sample size was very small (n = 22 for the cross-sectional phase, n = 8 for the interventional phase). The abstract does not report baseline fitness levels, sex distribution, dietary carnitine intake, or actual body weight changes over time.
Cited by
- supports In a study of 22 adults, fat utilization during exercise was 25% lower in individuals with marginal vitamin C status (below 34 micromoles per liter) compared to those with adequate levels.