The Science Behind the Hype
Like thousands of others, I was looking for a magic bullet, a secret supplement no one else was taking, that would lead me to newfound levels of strength and athleticism. When I read that l-carnitine l-tartrate (LCLT) could help me burn fat, recover from exercise, favorably affect my hormone levels, and deliver more oxygen to my muscles, I was intrigued.
When I read that all of this was backed up with peer-reviewed academic research, I drove to my local GNC and laid my money on the table. It was only then that I decided to read the research myself and only then that I discovered that all the research was funded by Lonza, a company that manufactures LCLT. So, is LCLT research biased? From what I’ve found, it is, but that doesn’t necessarily mean it’s wrong. In this article, we’ll take a look at what LCLT is, why powerlifters specifically may or may not want to take it, and what current science there is to support this conclusion.
Carnitine is responsible for the transport of long-chain fatty acids (or, simply put, fat) into the energy producing factories of your cells known as the mitochondria (1). Theoretically, l-carnitine could be taken in supplement form to aid in fat metabolism. However, research on the subject has had mixed results. One problem is that l-carnitine is not easily storable in its natural form. It attracts moisture and is easily degraded. A possible solution for this problem is to use l-carnitine l-tartrate, a salt of l-carnitine, which is stored more easily as a solid. Within the past few years, several key studies have been published by the University of Connecticut on the use of LCLT as a performance-enhancing supplement, all of which yielded promising results.
Over the past six years, a series of four research reports were published in various academic journals on the effects of LCLT. The reports covered a range of topics such as hormonal responses to resistance exercise (2), recovery from exercise stress (3), muscle oxygenation (4), and varying doses of LCLT that may be effective (5). However, all of the studies shared similar themes that need to be examined more closely when applying the findings to athletes in our sport.
In every report, athletes performed 15–20 repetitions of the squat exercise at a resistance equal to 50 percent of their one repetition maximum (1RM). Subjects performed all reps on the Plyometric Power System, which is very similar to a Smith machine. All participants had experience with the squat exercise for at least one year prior to testing, and all participants were of similar age. In every report, 8–10 athletes were included. Furthermore, in three of the reports, subjects took 2 grams of LCLT daily while regularly meeting with a registered dietician to help standardize dietary behaviors. Lastly, every report was funded by a grant from Lonza Inc., a company that produces LCLT.
Beyond the conflict of interest present due to sponsorship, the most glaring problem that I see is sports specificity. Rarely do powerlifters train at 50 percent of their 1RM for 15–20 repetitions, and, if training is performed at a heavier load, how will that affect LCLT use? In fact, the authors specifically chose a load of 50 percent because “excessive muscle damage might affect capillary integrity and subsequently mitigate the effects of LCLT on muscle blood flow” (4). Simply put, if you plan on doing any actual powerlifting, LCLT may not work at all.
Another important factor to consider is that subjects were regularly meeting with dieticians and
consistently performing exercise testing three hours after lunch. This is important when you consider that muscle, carnitine use, and fat oxidation rates are lower during exercise with higher muscle glycogen (carbohydrates stored in the muscle) (6). Because many well-fed powerlifters are carrying extra muscle glycogen, this may limit the effectiveness of supplemental carnitine as well.
This, in fact, is the most important concept—l-carnitine is certainly involved in fat oxidation in muscle cells. The only question is whether typical well-fed athletes will absorb the LCLT and use it to increase performance. According to the University of Maryland Medical Center, carnitine is produced in the liver and kidneys by breaking down the amino acids lysine and methionine (1). These amino acids are found in many foods including meat and cheese. In addition, up to 75 percent of dietary l-carnitine may be absorbed from food in contrast to only 5–18 percent of l-carnitine in supplement form (7). On top of these statistics, athletes whose dietary fat levels vary may not be the best subjects for carnitine supplementation research (8).
So, back to our main question…should powerlifters supplement with LCLT? For lifters with deficiencies in some key amino acids or muscle glycogen, those carefully monitoring their dietary fat, or those who don’t plan on doing fairly intense and heavy lifting, LCLT supplementation could help. Otherwise, there are more effective supplements no matter what
Lonza might tell you.
References
1. Debusk R (2002) Carnitine (L-Carnitine). Retrieved: January 2, 2009. From: University of Maryland Medical Center website #.
2. Kraemer WJ, Volek JS (2003) The effects of L-Carnitine L-Tartrate supplementation on hormonal responses to resistance exercise and recovery. Journal of Strength and Conditioning Research 17(3):455–62.
3. Volek JS, Kraemer WJ (2002) L-Carnitine L-Tartrate supplementation favorably affects markers of recovery from exercise stress. American Journal of Physiology: Endocrinology and Metabolism 282:474–82.
4. Spiering BA, Kraemer WJ (2008) Effects of l-carnitine l-tartrate supplementation on muscle oxygenation responses to resistance exercise. Journal of Strength and Conditioning Research 22(4):1130–35.
5. Spiering BA, Kraemer WJ (2007) Responses of criterion variables to different supplemental doses of L-Carnitine L-Tartrate. Journal of Strength and Conditioning Research 21(1):259–64.
6. Roepstorff C, Halberg N (2004) Malonyl-Coa and carnitine in regulation of fat oxidation in human skeletal muscle during exercise. American Journal of Physiology: Endocrinology and Metabolism 288:133–42.
7. Evans AM, Fornasini G (2003) Pharmacokinetics of L-Carnitine. Clinical Pharmacokinetics 42(11):941–67.
8. Ransome JW, Lefavi RG (1997) The effects of dietary L-Carnitine on anaerobic exercise lactate in elite male athletes. Journal of Strength and Conditioning Research 11(1):4–7.