L-carnitine benefits are numerous but according to clinical studies, it looks like L-carnitine is more than likely ineffective.
L-carnitine has several other names: aminocarnitine, B(t) Factor, Carnitine, Carnitor, D-Carnitine, DL-Carnitine, Facteur B(t), L-Carnitina, L-Carnitine Fumarate, L-Carnitine L-Tartrate, L-Carnitine Tartrate, Levocarnitine, Levocarnitine Fumurate, Vitacarn, Vitamin B(t), Vitamine B(t).
When L-carnitine is used orally and properly L-carnitine has been used with safety in clinical trials with a total duration up to 6 months. In children, L-carnitine has been used orally and safely for up to 2 months. Avoid using during pregnancy. In low doses, L-carnitine is safe during lactation but large does during nursing have unknown effects.
L-Carnitine was shown ineffective in a study done on endurance-trained athletes. Seven men were given 2 grams of l-carnitine 2 hours before the start of a long-run and again after 20 km of the run. The administration caused no significant change in the running time of the runners. In addition, a test was run to check the performance output of the athletes the morning after the run. There was no difference in the result of this test even though the athletes supplemented with L-carnitine. The study proved that there was no enhancement of physical performance of the endurance-trained athletes during the run and it did not alter their recovery either. Note: This study is in direct contrast to claims that say L-carnitine enhances athletic performance.
A study published in the Journal of Sports Medicine notes that there has been a lot of supplementary use of L-cartinine without scientific support for this practice. It was found that l-cartinine does not postpone fatigue during exercise. It also doesn’t unequivocally improve performance of athletes. It didn’t reduce body fat or help support weight loss either. Some have said that athletes are at risk for carnitine deficiency however scientific observations found there is a redistribution of free carnitine and acylcarnitines in the muscle without a loss of total carnitine, meaning supplementation is not needed.
In another study of the Journal of Strength and Conditioning Research, L-carnitine and its effects on anabolic hormones were assessed. It appears that L-carnitine L-tartrate significantly increases Insulin-like growth factor-binding protein 3, an anabolic hormone. It also, over the recovery period, reduced the amount of exercise-induce tissue damage. This supports the use of L-carnitine L-tartrate as a recovery supplement.
Finally, the last study I looked at looked at moderately obese women that consumed L-carnitine in the amount of two grams twice daily for 8 weeks. All study participants walked 30 minutes a day 4/days a week. After the study was completed, the L-carntinine group was assessed compared to a placebo group which took a sugar pill. There were no significant changes in mean total body mass, fat mass, and resting lipid utilization occurred over time, nor were there any significant differences between groups for any variable. This shows that L-carnitine did absolutely nothing in terms of improving lean body mass and fat mass in people walking 30 minutes a day for 4 days a wee for 8 weeks.
While L-carnitine appears to be used safely it doesn’t appear to help aerobic or endurance athletes train. This is despite its widespread use, which doesn’t have any scientific support for it. I suspect they are referring to acetyl L-carnitine which is different than L-carnitine tartrate.
Apparently, L-carnitine L-tartrate works to increase an anabolic response while reducing the amount of exercise induced tissue damage. If you can increase the anabolic response you could likely increase the amount of muscle gained and fat loss. While preventing tissue damage, it seems like you could return to 100% performance during athletics or aerobic exercise before normal.
What needs to be done is a placebo trial testing subsequent athletic performance after a heavy exercise session to see if this lessor amount of tissue damage really results in a significant change. It is still possible that the lessor amount of tissue damage may very well not amount to any difference in performance or training.
I suspect if you want some benefit from L-carnitine that you try the L-tartrate form of it. Make sure to take 2 grams twice daily of it because that was the dose used that showed an improved anabolic profile and a lessor amount of muscle tissue damage. I’ve heard of many bodybuilders using L-carnitine before but the majority of the evidence is pointing to no benefit whatsoever. Note that most of the studies didn’t differentiate between acetyl L-carnitine and L-carnitine L-tartrate.
1. Colombani P, Wenk C, Kunz I, et al. Effects of L-carnitine supplementation on physical performance and energy metabolism of endurance-trained athletes: a double-blind crossover field study. Eur J Appl Physiol Occup Physiol. 1996;73(5):434-9.
2. Heinonen Oj. Carnitine and physical exercise. Sports Med 1996;22:109-32.
3. Kraemer WJ, Volek JS, French DN, et al. The effects of L-carnitine L-tartrate supplementation on hormonal responses to resistance exercise and recovery. J Strength Cond Res 2003;17(3):455-62.
4. Villani RG, Gannon J, Self M, et al. L-carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. Int J Sport Nutr Exerc Metab. 2000;10(2):199-207.