Wednesday, February 4, 2015

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).
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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).
Hold on, wasn't carnitine the stuff that's responsible for the artherogenic effects of meat? If you believe in the headlines in all the major news outlets after the publication of the 2013 study by Koeth et al., the answer would be: "Yes! It does.". If you take a look at the existing scientific evidence it is yet a bit strange that this hold only for processed, best fried, yet not for other types of meat (learn more). One of the latest meta-analyses of in vivo studies indicates by the way that "L-carnitine is associated with a 27% reduction in all-cause mortality, a 65% reduction in VAs [ventricular arrhythmias], and a 40% reduction in anginal symptoms in patients experiencing an acute myocardial infarction." Furthermore, the authors from the Mayo Clinic demand that "study with large randomized controlled trials of this inexpensive and safe therapy in the modern era is warranted" (DiNicolantonio. 2013). And if you look at the epidemiological evidence, it will strike you as odd that eating unprocessed red meat regularly is not associated with a significant increase of heart disease, although it is the type of meat that is highest in carnitine (Micha. 2010).
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.
The more choline the better the carnitine retention. The question is however: If the levels already increased and there still was no effect - would adding choline actually make a difference?
Bottom line: The good news is that vegetarians can easily compensate their lack of dietary carnitine by supplementing with 2g of l-carnitine tartrate per day. The bad news is that this is without consequences on any of the relevant metabolic and/or performance markers.

In view of the fact that the l-carnitine was consumed immediately after breakfast and dinner, i.e. in a period where insulin was high and could help shuttle the carnitine into the muscle, it's questionable whether the addition of choline, of which you as a SuppVersity reader know that it increases the muscular carnitine retention, would have yielded significantly different results. It may have helped to elevate the carnitine levels in the muscle of the omnivore control subjects, but it's unlikely that it would have changed the non-existent effects the increase in muscular carnitine pools in the vegetarians had on their metabolism and physical performance | Comment on Facebook!
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.