A daily dose of 2 g L-carnitine protects athletes’ muscles from breaking down, according to a human study that sports scientists at the Islamic Azad University in Iran published in the Asian Journal of Sports Medicine. Whether the anticatabolic effect of L-carnitine speeds up muscle building? The researchers did not look at this, but who knows…
Your body’s cells convert nutrients into energy in their mitochondria. You could say that mitochondria are molecular power plants. And if mitochondria are power plants, then L-carnitine molecules are the trucks that transport the coal fermentable biomass. That’s why sports scientists are so interested in L-carnitine supplementation.
The researchers divided 22 physically active young men into two groups. One group took a placebo for two weeks; the other group took a supplement containing 2 g L-carnitine. At the end of the two weeks the researchers got the men to run for 15 minutes.
The researchers also analysed the subjects’ blood: before supplementation started [Base], just before they started running [Pre], just after they finished running [Post] and again 2 [2 h] and 24 hours [24 h] afterwards.
The running session boosted the concentration of the enzymes LDH and CK in the men’s blood, but the increase was noticeably less in the men who had been given carnitine. LDH and CK are markers for muscle damage. It seemed that L-carnitine supplementation reduced muscle damage.
TBARS is a marker for free radical activity. These are aggressive molecules that can damage cell structure and are released during intensive physical exercise. The running session raised the concentration of TBARS in the subjects’ blood, but the increase was less in the men who had taken L-carnitine.
In addition L-carnitine supplementation maintained the antioxidant functioning of the blood. Antioxidants can neutralise free radicals.
“The present study demonstrates that an acute bout of exercise can induce oxidative stress in active healthy young men”, the researchers wrote in the last paragraph of their publication. “Two-week daily oral supplementation with L-carnitine has some alleviating effects on lipid peroxidation and muscle damage indices in favour of increased antioxidant capacity.”
“Nevertheless, the exact mechanism of L-carnitine in attenuating the markers of oxidative stress is not well established and further exploration is needed.”
Wild speculation on our part
Sports supplements manufacturers sometimes put L-carnitine in supplements intended to promote muscle growth. This study suggests that these supplements may indeed be effective because they reduce muscle breakdown during intensive workouts.
The effects of L-carnitine supplementation are inconclusive in the literature. This is probably because the body only absorbs L-carnitine in supplements if they are consumed with large quantities of carbohydrates. You can read more about this here and here.
The effect of two-week L-carnitine supplementation on exercise -induced oxidative stress and muscle damage.
This study was conducted to assess the effect of Two-week L-carnitine supplementation on known markers of oxidative stress and muscle damage following acute bouts of exercise in active healthy young men.
Twenty-one active healthy men volunteered for this study. Participants were randomized in a double-blind placebo-controlled fashion into two groups: L-carnitine (C group; n=10) and placebo group (P group; n=11). They arrived at the laboratory after overnight fasting. A baseline blood sample was taken. Afterwards, subjects consumed either L-carnitine (2 capsules containing totally 2000 mg L-carnitine) or placebo (2 capsules containing totally 2000 mg lactose) daily for 14 days. On the day of the test, participants attended the athletics arena after overnight fasting. Then, participants were asked to run 14 km on the track at their highest ability. Blood samples were taken immediately, 2, and 24 hours after exercise. Plasma total antioxidant capacity (TAC), malondialdehyde (MDA) as thiobarbituric acid-reactive substance (TBARS) as a marker of lipid peroxidation, creatine kinase (CK) and lactate dehydrogenase (LDH) as markers of muscle damage were measured.
TAC increased significantly 14 days after supplementation and 24h after exercise in C group compared with P group (P<0.05). Serum MDA-TBARS, CK, and LDH were significantly lower 24h after exercise in C group compared with P group (P<0.05).
These results suggest that two-week daily oral supplementation of L-carnitine has alleviating effects on lipid peroxidation and muscle damage markers following an acute bout of exercise in active healthy young men.
PMID: 25834706 PMCID: PMC4374610 [PubMed]