Page updated Dec 5, 2018. First published Sep 16, 2013. No comments
L-carnitine is one of the most often used ingredients of over-the-counter fat loss formulas. In theory, L-carnitine almost seems like the ideal fat burner (non-stimulant, preferentially burns fat for energy, with minimal adverse effects and useful for its ability to cause recovery from intense exercise sessions). However, the fact remains that L-carnitine doesn’t enjoy much scientific support. Let us investigate!
L-carnitine is one of the most often used ingredients of over-the-counter fat loss formulas (Kreider et al., 2010). In theory, L-carnitine almost seems like the ideal fat burner (non-stimulant, preferentially burns fat for energy, with minimal adverse effects and useful for its ability to cause recovery from intense exercise sessions).
However, the fact remains that L-carnitine doesn’t enjoy much scientific support. Let us investigate!
What is L-carnitine?
L-carnitine is an amino acid that is synthesized by the liver and kidneys (Higgins, Tuttle, & Higgins, 2010). Chief food sources of L-carnitine are red meat and mutton (Yonei, Takahashi, Hibino, Watanabe, & Yoshioka, 2008).
What does L-carnitine work its magic?
It main mode of action seems to be to stimulate basal metabolic rate (Higgins et al., 2010).
Moreover, there is some suggestion that L-carnitine may also improve recovery from intense training sessions (Higgins et al., 2010). This is attributed to its action of preventing/reducing cell damage in response to the stress of training (Higgins et al., 2010; Karlic & Lohninger, 2004). It is also equally impressive in effecting recovery of injured athletes (Karlic & Lohninger, 2004).
So, how exactly does L-carnitine cause fat loss? One suggested mechanism is that L-carnitine burns intracellular fat (Yonei et al., 2008; Seifert, Schaechter, Hershorin, & Lipshultz, 2011). L-carnitine combines with acyl coenzyme A to form acylcarnitine which helps stimulates transport of fatty acids from within the cells to inside the mitochondria – where they are used as substrate for energy production.
Additionally, it is believed that L-carnitine may reduce the reliance on blood sugar as the prime source of energy (Yonei et al., 2008).
In a nutshell, this is what L-carnitine does:
Transports fats in the mitochondria of the cells
Intracellular fats are then oxidised
Fats used preferentially over blood sugar for producing energy
Net result – loss of body fat
Other physiological roles of L-carnitine (Higgins et al., 2010) are:
Stimulation of haematopoiesis (formation of new blood cells)
Inhibition of aggregation of platelet in response to presence of collagen
Prevention of cell injury and premature cell death
Thus, L-carnitine seems to play a crucial role in cell protection and cell recovery.
Are there any Other Benefits of L-carnitine Supplementation?
Notwithstanding the alleged effectiveness of L-carnitine in improving exercise tolerance and body composition, there are some pathological conditions under which supplementation with L-carnitine may be of therapeutic and preventive benefit; for instance:
Treatment of liver and heart disease (Ferrari et al., 2004)
Treatment of mental stress (Alesci, De Martino, Kino, & Ilias, 2004)
Improvement of male reproductive functions (Alesci et al., 2004)
Improvement in vision (Yonei et al., 2008)
Prevention of cardiovascular diseases by lowering plasma lipid levels (Ferrari et al., 2004)
Prevention of short-term memory loss, depression and Alzheimer’s disease (Virmani & Binienda, 2004)
As a dietary supplement in patients with renal failure (Yonei et al., 2008)
What are the Doses that I Should be Taking?
The doses of L-carnitine for fat-loss or improving exercise performance have not been defined. However, doses greater than 2g per serving fail to elicit any more advantages since research suggests that at this dose, saturation of absorption occurs (Bain, Milne, & Evans, 2006).
However, doses of L-carnitine used by researchers for studding its benefits in pathological states have tended to range from 2g to 6g per day in divided doses. These are to be taken either in tablet form or as oral solution (WebMD, 2013).
Although associated with minor side-effects when taken orally – nausea, heartburn, stomach upset – L-carnitine is generally well tolerated by almost everyone (WebMD, 2013).
Is there any Scientific Proof in Support of L-carnitine?
Over the last few decades, numerous studies have been conducted investigating the alleged benefits of L-carnitine on exercise performance, fat metabolism, and body composition. Opinion regarding the effective of L-carnitine in causing weight loss, however, is divided.
Some studies have tended to support the hypothesis that L-carnitine causes fat loss (Saper, Eisenberg, & Phillips, 2004; Seifert et al., 2011; Valentino, Lin, & Waldman, 2010; Yonei et al., 2008). L-carnitine, apparently, increases maximal oxygen consumption and decreases respiratory quotient; both of which are characteristic of an enhanced fat metabolism (Karlic & Lohninger, 2004; Higgins et al., 2010).
Transport of fatty acids into mitochondria where they are oxidized is the most often suggestion mechanism of fat loss induced by L-carnitine (Seifert et al., 2011; Yonei et al., 2008).
Also, there are those who believe that L-carnitine tartrate – along with creatine, calcium ?-HMB and BCCAs (branched-chain amino acids) – is one of the supplement ingredients that indeed works when it comes to muscle recover after a heavy training session (Kreider, 1999; Knitter, Panton, Rathmacher, Petersen, & Sharp, 2000; Coombes & McNaughton, 2000; Schena, Guerrini, Tregnaghi, & Kayser, 1992; Candeloro, Bertini, Melchiorri, & De, 1995; Volek et al., 2002; Volek et al., 2004; Mero, 1999)
On the other hand, there are those researchers who tend to disagree – reporting that L-carnitine is ineffective in improving either exercise performance (aerobic/anaerobic) or fat metabolism (Smith, Fry, Tschume, & Bloomer, 2008)
Furthermore, Smith et al. in 2008, reported that L-carnitine supplementation may even fail to improve muscle content of carnitine (Smith et al., 2008). Thereby, seriously affecting the actions of L-carnitine on reducing training-induced stress (Bloomer & Smith, 2009)
No wonder then that L-carnitine – going by what most researchers report – fails to elicit weight loss in either untrained, overweight individual or a trained person (Brass, 2000; Villani, Gannon, Self, & Rich, 2000).
Further Research on L-Carnitine
The evidence in favour of effectiveness of L-carnitine seems to be inconclusive. Therefore currently, we are of the opinion – pending further research – that L-carnitine will not help you lose weight!
Although we have branded L-carnitine – based on current scientific evidence – ineffective in causing weight loss, it is still early days to suggest that it is totally worthless.
For instance, recent research suggests that L-carnitine (as its tartrate salt) is indeed effective in helping athletes recover from intense training sessions (Volek et al., 2002). And, as well know, better (and quicker) recovery translates into better performance during the next training session and therefore, better and quicker results! Thus, it can be argued that L-carnitine may have an indirect action in improving lean body mass.
Therefore, although L-carnitine fails on the ‘weight-loss front’ it does seem to have other useful benefits. However, further research needs to be conducted to corroborate these findings.
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Bloomer, R. J. & Smith, W. A. (2009). Oxidative stress in response to aerobic and anaerobic power testing: influence of exercise training and carnitine supplementation. Res.Sports Med, 17, 1-16.
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Volek, J. S., Kraemer, W. J., Rubin, M. R., Gomez, A. L., Ratamess, N. A., & Gaynor, P. (2002). L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress. Am J Physiol Endocrinol.Metab, 282, E474-E482.
Volek, J. S., Ratamess, N. A., Rubin, M. R., Gomez, A. L., French, D. N., McGuigan, M. M. et al. (2004). The effects of creatine supplementation on muscular performance and body composition responses to short-term resistance training overreaching. Eur J Appl.Physiol, 91, 628-637.
Yonei, Y., Takahashi, Y., Hibino, S., Watanabe, M., & Yoshioka, T. (2008). Effects on the Human Body of a Dietary Supplement Containing L-Carnitine and Garcinia cambogia Extract: A Study using Double-blind Tests. J Clin Biochem.Nutr., 42, 89-103.
About the author: Rachel Butler
Rachel has been with us since we launched back in 2012.
Rachel has reviewed countless products over the years, and has written many articles offering sound advice. Her professional opinions are widely respected.
Rachel graduated a BSc in Clinical Science from the University of Leicester, U.K.
She lives in York with her husband and young daughter and their dog, a little terrier named Betsy.
Disclaimer: Our reviews and investigations are based on extensive research from the information publicly available to us and consumers at the time of first publishing the post. Information is based on our personal opinion and whilst we endeavour to ensure information is up-to-date, manufacturers do from time to time change their products and future research may disagree with our findings. If you feel any of the information is inaccurate, please contact us and we will review the information provided.