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L-Carnitine: Fact or Fiction? A rejoinder to Hilary Spruytenburg's article: L-Carnitine: Powerful Endurance Enhancer or unnecessary ergogenic? WHAT IS L-CARNITINE? L-Carnitine is a naturally occurring amino acid which plays a vital role in the metabolism of fat. It functions as a transporter of fatty acids into the mitochondria, the metabolic furnace of the cell. L-carnitine was discovered in Russia, and one year later in Germany. The proper name, Carnitine, refers to the Latin origin, (carno, caris). Its structural formula was decoded in 1927, and its physiological significance was understood by the 1960's. (http://www.hlthmall.com/l-carnitine.html) L-carnitine is synthesized in the liver and kidneys, from two essential amino acids, lysine and methionine. This synthesis requires the presence of vitamins niacin, B6, and iron. Most (98%) of the carnitine supply resides in the body's muscle tissue. Approximately 80% of the amino acids our bodies need is endogenously synthesized, the remaining 20% are referred to as the essential amino acids. The supply of such aminos, like l-carnitine, must be supplemented exogenously. L-carnitine is available in the following food sources: red meat, diary products, avocado, and tempeh. Although a well balanced diet can provide approximately 75% of what the body is lacking, often conditions arise that make it difficult to obtain all the carnitine one needs.
It has been established that an adequate supply of l-carnitine is necessary for the maintenance of good health. L-carnitine transports long-chain fatty acids across the mitochondrial membrane to be metabolized. L-carnitine aids in the release of stored body fat, tryglycerides, into the bloodstream for energy. Tryglycerides are the major source for the production of energy in the heart and skeletal muscles. Access to l-carnitine is believed to increase energy levels for long-term aerobic activity. L-carnitine is also responsible for muscle contraction, regulation of protein balance and maintenance of a healthy heart. Research also suggests that an adequate supply of l-carnitine could be instrumental in the treatment of diabetes, chronic fatigue syndrome, kidney and liver disease. (http://www.healthlink.com.au/nat_lib/htm-data/htm-supp/supps72.htm) Since its involvement in the process of burning fats is of most importance to those interested in endurance and body fitness, it is this topic that will be focused upon.
THE ROLE OF L-CARNITINE: HOW DOES IT WORK?
Carnitine boosts energy by stimulating the body's burning of tryglycerides as fuel, and sparing the supply of glycogen stored in the liver for heavier exertion. During exercise, the body will burn fat at a rate of 75-80% of maximum exertion, thus less glycogen from carbohydrates is burned. L-carnitine allows the body to burn more fat, save more glycogen, and ultimately boost stamina and endurance. By providing more fat to the muscles, carnitine makes accessible an otherwise unavailable energy source. (http://www.betterbodz.com/library/l-carnitine.html)
FAT + OXYGEN + L-CARNITINE = ENERGY
Is this the recipe for success? According to proponents of L-Carnitine, it is the essential amino acid in the optimum fat burning process. They believe that carnitine is to the human body, what a turbo mechanism is to a car: both provide optimal fuel and performance. Minus L-carnitine, fatty acids would have a difficult time permeating the walls of the mitochondria. Energy, stored in carbohydrates and fats, is required to work the muscle. Carbohydrates are converted from glucose to glycogen, to be stored in liver and muscle cells. Eventually, the body turns to fat storage for energy, and possibly, with more ease in the presence of L-carnitine. This is where L-carnitine as a supplement enters. During high energy output, the supply of L-carnitine becomes exhausted. Is it possible to compensate for this decrease solely through metabolic processes and diet? Or is an additional carnitine supplement needed for the extra boost? Judging from the variety of carnitine products now on the market, apparently many believe an additional outside source proves beneficial.
WHAT'S AVAILABLE? IS IT EFFECTIVE?
On the market today, exists a wide domain of ergogenic (or "energy boosting") aids, designed to enhance performance and to create a leaner, trimmer and more beautiful body. L-carnitine is found in many of these products. The amino acid is considered so potent that it is as equally often packaged independently, as it is compounded with other ingredients. Briefed here are several l-carnitine supplements readily available. Each product's marketing adheres to the fundamental claim that L-carnitine increases the amount of fat burned, thus increasing energy and lean muscle mass.
To address the question, "Is L-Carnitine Effective?", it becomes necessary to look beyond advertised claims. Understandably, manufacturers support their products, and are thus biased. Likewise, individual testimony most frequently arises from successful trials with L-carnitine. In order to provide a full-spectrum report, we now turn to information evidenced in non-promotional sources. WHAT DO THE STUDIES SHOW? Recent research done on L-carnitine shows mixed results concerning its effectiveness. A number of journal studies involving the administration of l-carnitine to both human participants and animal subjects reveals both adverse and positive results. In Training and Nutrition, J. P. Krabbe (1996) reports that although L-carnitine is important in the correction of human carnitine deficiency, once such a deficiency is corrected, more is unnecessary. Since humans get plenty of it from meat and diary products, most healthy individuals exceed the recommended daily dosage. Krabbe writes, "Also true is that once any deficiency is corrected, that the majority will get excreted. Thus, more is not better, unless you need it." (http://ww.cyberiron.com/supplement/carnitine.html) Such a case is reported in the Journal of Clinical Neurology. A woman showed secondary carnitine deficiency as a result of anorexia nervosa and liver damage, which rendered her liver incapable of synthesizing l-carnitine (Negoro, Tsuda, Kato & Morimatsu, 1995). Her deficiency was treated with oral administration of L-carnitine. M. H. Williams (1992) researched the use of ergogenic aids among endurance athletes, and found L-carnitine to be ineffective. Factors that did in fact enhance performance were genetic endowment, proper training and nutrition, and an adequate supply of fluids and carbohydrates. Conversely, McCarty (1995) found that carnitine may promote weight loss in exercise regimens by enhancing glucose homeostasis in the liver. At the Nestle Research Centre, researchers studied the effect of L-carnitine on exercise metabolism after depletion of muscle glycogen. Nine healthy male subjects received L-carnitine or a placebo and then were submitted to 60 minutes of exercise after an overnight fast. It was concluded that metabolism was not influenced by carnitine supplementation (Decombaz, Deriaz, Acheson, Gmuender & Jequier, 1993). A similar study found that during submaximal exercise, carnitine supplementation did not result in increased lipid oxidation or muscle carnitine content, indicating that the administered carnitine was not absorbed by the body (Vukovich, Costill & Fink, 1994). IN CONCLUSION Is L-carnitine a safe and effective means of enhancing fat metabolism? The evidence presented here reports no harmful side effects. Product reports contest that l-carnitine works by transporting fatty acids to be burned for fuel, increasing both energy supply and lean muscle mass. Studies show a more skeptical look at the product. Most found that unless an individual is deficient in l-carnitine, it is an unnecessary ergogenic aid. I conclude that as with other vitamins, minerals and medications, L-carnitine is as effective as the consumer's belief in the product. REFERENCES
After reading Hilary's article it seems quite logical to argue that this supplement (like most) becomes most effective when your body is naturally deficient in supply. Once this deficiency is corrected by oral administration, through the assistance of a medical professional, further use becomes unnecessary. Any extras are excreted from the body. The Western diet is not deficient in L-Carnitine, going by its natural sources of dairy products, red meat and so the recommended daily amount can be easily met. I cannot speak for vegetarians and vegans. Furthermore, the human body can synthesise it from the amino acids Lysine and Methionine. They say it increases the use of fat as an energy source by transporting fatty acids into the mitochondria where they are "burned" to release energy for body functions. Maybe, but you can also"manually" deny your body of carbohydrate and force it to mobilise fat to be burnt. This begs the question of the efficacy of sustained supplementation as the body already has enough and can/should be able to do it on its own. Bodybuilders known for their get the job done mentality would simply use a thermogenic supplement tried and tested. Even if you were to use a carb/starch source to drive in the carnitine "as quickly as possible", speed here is not the issue. What about issues relating to the carb calories which must be included as part of the calorie calculation? The frequency of use may be an unwanted factor in calorie restriction i.e. if you needed 2-3 servings per day as most recommend. Most damaging, especially to your wallet, is the cost of pharmaceutical grade L-Carnitine compared to the commercial carnitine found on the market although marketing hype may try to make you think differently. Real pharma grade L-Carnitine is quite pricey. If we, therefore, examine the weight of conclusive scientific evidence, the existence of cost effective alternatives, the fact that the body can synthesise L-Carnitine, the fact that it has actually been proven to work best when the body is deficient in it, its use in any way or form as a fat burning supplement is very limited. I know this industry i.e. the supplement industry is very astute when it comes to marketing and carnitine concoctions and mixes come and go (with a frequency akin to viral mutations) each explaining their effectiveness. A lot has been said of its benefits in treating certain heart conditions and memory disease and I would hope anyone with symptoms of these aforementioned diseases or L-Carnitine deficiencies seek proper professional medical care. When you do this, compare the cost of the L-Carnitine your doctor would prescribe to what is commercially available. Probably why its required by law to state that your supplement is not designed to cure, diagnose or treat disease. So far as effective fat loss is concerned, the efficacy of L-Carnitine leaves much to doubt. It was big in the early to late 90s in liquid and tablet form but seems now to be relegated to the dust-heap of supplements that have been and taken their place in the archives of sports nutrition. Long live L-Carnitine! Only as a supplement to correct L-Carnitine deficiency in the system. It is within this realm and not outside it that its importance is to be realised. |
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