Inadequate vitamin C levels may limit fat burning during exercise. Digest
Fat oxidation, the process of breaking down fatty acids from both stored and dietary fat for energy, is critical for endurance during physical activity and weight control. However, not everyone's body uses fat efficiently during activity. In search of contributing factors, researchers investigated whether low vitamin C levels reduce fat burning.
The study involved healthy young adults with either marginal or adequate vitamin C status. Participants completed a one-hour treadmill session at submaximal intensity while researchers measured fat oxidation. In a follow-up experiment, participants with low vitamin C levels were randomly assigned to take either 500 milligrams of vitamin C per day or a placebo for four weeks, after which the exercise test was repeated.
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Vitamin C status showed effects on increasing fat burning:
- Participants with marginal vitamin C status used roughly one-quarter less fat for energy during exercise, relative to those with adequate status.
- Lower fat oxidation was linked to higher self-reported fatigue.
- Among deficient participants, vitamin C supplementation increased fat-derived energy expenditure during exercise four-fold compared to placebo.
- Plasma carnitine differed by vitamin C status and was related to fat oxidation during exercise. Carnitine helps shuttle fatty acids into mitochondria to be broken down for energy.
These findings are consistent with vitamin C's role in producing carnitine. Without enough vitamin C, carnitine synthesis may falter, reducing the transport of fatty acids for oxidation. This bottleneck could increase reliance on carbohydrate stores and contribute to fatigue during exercise.
Conclusion:
The study suggests that low vitamin C status is associated with reduced fat oxidation and greater fatigue during submaximal physical activity, and that supplementation can improve fat metabolism. Beyond its impact on exercise performance, the combination of reduced fat oxidation and increased fatigue could also contribute to weight gain, both by discouraging regular, demanding physical activity and by favoring fat storage. Although the results are intriguing, the study was small and did not directly measure muscle carnitine. Larger, more comprehensive studies are needed to confirm these findings. Learn more about how inadequate micronutrient levels impact health in this clip featuring Dr. Bruce Ames.