Carnitine Deficiency of Vegetarians Can Be Compensated W/ 2g of L-Carnitine Tartrate Per Day - Unfortunately, Without Measurable Metabolic or Performance Benefits

Vegetarian athletes do lack carnitine in their diets and muscle, but whether this has significant effects on their performance appears to be questionable based on the results of the study at hand.

In a recent study, researchers from the University Hospital Basel investigated whether the previously observed low carnitine levels of vegetarians could be compensated for by longterm oral treatment with 2g of l-carnitine to replenish the body carnitine pool. Furthermore, the scientists wanted to know whether this would have significant effects on (a) fuel metabolism and (b) physical performance of vegetarians and omnivores.

Novakova et al. hypothesized that "treatment with carnitine would increase plasma and possibly also skeletal muscle carnitine concentrations in vegetarians and would thereby improve skeletal muscle energy metabolism and physical performance" (Novakova. 2015).
As you already know from the headline of this article, the latter was not the case and that despite the fact that the data in Figure 1 indicates that the daily provision of 2x1g l-carnitine tartrate after breakfast and dinner, respectively, for twelve weeks lead to a significant increase of the muscular carnitine levels of the 16 vegetarian, 18-40 year-old subjects of the study at hand.

Figure 1: Study design (left) and total skeletal muscle carnitine levels according to biopsy (right | Novakova. 2015)

In the 8 omnivore subjects that served as a control, the non-choline supported (choline maximizes carnitine retention | learn more) provision of a total 2g of l-carnitine tartrate did not show a consistent effect on the total carnitine muscle content (Figure 1).
This observation in the omnivore control group is quite disappointing - specifically in view of the fact that 90% of the people who buy carnitine supplements probably eat meat.

Figure 2: None of the metabolically or performance relevant parameters changed sign. (Novakova. 2015).

In that, it's probably a small comfort that the increase in muscle carnitine levels didn't pay off in terms of increased physical performance, anyway. A brief glimpse at the data in Figure 2 goes to show you: Neither of the tested metabolic and performance variables changes significantly from baseline to post-supplementation. If anything there as a minimal glycogen sparing effect which didn't reach statistical significance either (not shown in Figure 2). Most importantly, however, the VO2max and the RER of which you would hope that a supplement that's supposed to increase fatty acid oxidation would increase and lower them, respectively, didn't budge.
References:

• DiNicolantonio, James J., et al. "L-carnitine in the secondary prevention of cardiovascular disease: systematic review and meta-analysis." Mayo Clinic Proceedings. Vol. 88. No. 6. Elsevier, 2013.
• Koeth, Robert A., et al. "Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis." Nature medicine 19.5 (2013): 576-585.
• Micha, Renata, Sarah K. Wallace, and Dariush Mozaffarian. "Red and processed meat consumption and risk of incident coronary heart disease, stroke, and diabetes mellitus a systematic review and meta-analysis." Circulation 121.21 (2010): 2271-2283.
• Novakova, Katerina, et al. "Effect of l-carnitine supplementation on the body carnitine pool, skeletal muscle energy metabolism and physical performance in male vegetarians." European Journal of Nutrition (2015): 1-11.
• Wang, Zeneng, et al. "Gut flora metabolism of phosphatidylcholine promotes cardiovascular disease." Nature 472.7341 (2011): 57-63.