Writing in the Journal of Physiology, the researchers from the School of Biomedical Sciences at the University of Nottingham Medical School, said a combination of L-carnitine and carbohydrates delivered the measurable increase and concomitant athletic boost.
“This is the first demonstration that human muscle total carnitine (TC) can be increased by dietary means and results in muscle glycogen sparing during low intensity exercise (consistent with an increase in lipid utilisation) and a better matching of glycolytic, PDC and mitochondrial flux during high intensity exercise, thereby reducing muscle anaerobic ATP production,” they wrote.
“Furthermore, these changes were associated with an improvement in exercise performance.”
The researchers emphasised the dual metabolic effect of the L-carnitine supplementation at both low and high-intensity exercise levels, which led to a decrease in anaerobic energy production and a decrease in muscle lactate accumulation. Participants also registered lower perceived exertion as well as increased work output.
Speaking with NutraIngredients, lead researcher Professor Paul Greenhaff said the findings were, “very exciting” and a demonstration of evidence-based nutrition which was, “rare in the sports nutrition market”.
“Most of the studies to date have been heart-based and not focused on skeletal muscle,” he said. “These findings should spur a fresh round of research in this area.”
Professor Greenhaff said the University of Nottingham had filed a patent based on the L-carnitine uptake rates that had been granted in Australia and were pending in North America and Europe.
Swiss-based L-carnitine supplier Lonza, which provided the L-carnitine for the independent study, welcomed the findings.
“Previous studies show that Carnipure [its branded version] tartrate supplementation can increase fatty acid oxidation in a non-athletic population,” Lonza said.
“The current study is the first to show the same effect in recreational athletes. These findings together with previous findings demonstrate that Carnipure supplementation may lead to a decrease in the production of free radicals, less tissue damage and reduced muscle soreness after exercise.”
The randomised, double blind study had 14 healthy male volunteers with an average age of 25.9 years and Body Mass Index of 23 perform an exercise test comprising 30 minute cycling at 50% VO2max, 30min at 80% VO2max, then a 30 minute work output performance trial. They did this on three visits separated by 12 weeks.
After each visit the 14 men consumed either 80g of carbohydrate (CHO) or 2g of L-carnitine-L-tartrate and 80g of CHO twice daily for 24 weeks.
After that muscle TC increased 21% in the Carnitine group and was unchanged in the control group.
At 50%˙VO2max, the Carnitine group utilised 55% less muscle glycogen compared to control and 31% less pyruvate dehydrogenase complex (PDC) activation compared to before supplementation. At 80% VO2max, muscle PDC activation was 38% higher and muscle lactate content was 44% lower.
The Carnitine group increased work output 11% from baseline in the performance trial.
L-Carnitine, a vitamin-like nutrient, occurs naturally in the human body and is essential for turning fat into energy.
Journal of Physiology
‘Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans’
Authors: Benjamin T.Wall, Francis B. Stephens, Dumitru Constantin-Teodosiu, Kanagaraj Marimuthu, Ian A. Macdonald, Paul L. Greenhaff