Carbohydrate, protein, and fat metabolism during exercise after oral carnitine supplementation in humans
Abstract
Twenty nonvegetarian active males were pair-matched and randomly assigned to receive 2 g of L-carnitine L-tartrate (LC) or placebo per day for 2 wk. Participants exercised for 90 min at 70% VO2max after 2 days of a prescribed diet (M +/- SD: 13.6 +/- 1.6 MJ, 57% carbohydrate, 15% protein, 26% fat, 2% alcohol) before and after supplementation. Results indicated no change in carbohydrate oxidation, nitrogen excretion, branched-chain amino acid oxidation, or plasma urea during exercise between the beginning and end of supplementation in either group. After 2 wk of LC supplementation the plasma ammonia response to exercise tended to be suppressed (0 vs. 2 wk at 60 min exercise, 97 +/- 26 vs. 80 +/- 9, and 90 min exercise, 116 +/- 47 vs. 87 +/- 25 micromol/L), with no change in the placebo group. The data indicate that 2 wk of LC supplementation does not affect fat, carbohydrate, and protein contribution to metabolism during prolonged moderate-intensity cycling exercise. The tendency toward suppressed ammonia accumulation, however, indicates that oral LC supplementation might have the potential to reduce the metabolic stress of exercise or alter ammonia production or removal, which warrants further investigation.
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Research investigating the impact of carnitine supplementation on muscle fuel metabolism and/or exercise performance has produced inconclusive results.
“To date, research investigating the impact of carnitine supplementation on muscle fuel metabolism and/or exercise performance has produced inconclusive results [[185], [186], [187], [188], [189], [190], [191]].”
From Nutritional Considerations for the Vegan Athlete (2023) · cites this paper as [187]
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Self-citation
- Authors
- Broad, E. M., Maughan, R. J., & Galloway, S. D. R.
- Affiliations
- University of Stirling (GB)
- Venue
- International Journal of Sport Nutrition and Exercise Metabolism
- Publisher
- Human Kinetics
- Published
- 2008-12
- Volume
- 18
- Issue
- 6
- Pages
- 567-584
- ISSN
- 1526-484X (ISSN-L)
- 1543-2742
- OpenAlex
- W1563717935
- Cited by
- 35
- References
- 31
- Citations by year
- 2026: 3 · 2025: 3 · 2024: 1 · 2023: 3 · 2022: 1 · 2021: 2 · 2020: 4 · 2018: 6 · 2017: 2 · 2015: 1 · 2014: 2 · 2012: 1
- FWCI
- 0.87
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- International Journal of Sport Nutrition and Exercise Metabolism (publishedVersion)
- PubMed (publishedVersion)
- Stirling Online Research Repository (University of Stirling) (submittedVersion, public-domain)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Cell Biology › Muscle metabolism and nutrition
- Health Sciences › Medicine › Complementary and alternative medicine › Cardiovascular and exercise physiology
- Health Sciences › Medicine › Rehabilitation › Exercise and Physiological Responses
- Keywords
- exercise metabolism, carbohydrate oxidation, fat oxidation, protein oxidation, branched-chain amino acids, nitrogen excretion, blood ammonia
- MeSH terms
- Adult, Amino Acids, Ammonia, Bicycling, Blood Urea Nitrogen, Carnitine, Double-Blind Method, Exercise Test, Humans, Male, Nitrogen, Proteins, Tartrates, Exercise, Dietary Supplements, Carbohydrate Metabolism, Lipid Metabolism, Young Adult
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