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Non-Stimulant Diet Support
L-carnitine Emerges as a Promising
Alternative for Transformational Results

[ Editor's Note: Athletes who are sensitive to stimulants have long had few alternatives when it comes to diet support supplements, which are typically beefed up with caffeine, synephrine, and yohimbine, all potent stimulant compounds. Below, noted supplement science expert Dwayne Jackson takes a look at recent scientific developments regarding Acetyl-L-Carnitine and and L-Carnitine L-Tatrate (LCLT). ProSource, of course, offers the industry's purest and most potent formulation of ALC available. Investigation is ongoing, but current findings are highly promising for those who are considering using ALC alone or stacking it with a stimulant-based thermogenic.]

Most diet supplements use specialized formulas containing central nervous system stimulants. These constituents increase norepinephrine (noradrenaline) and epinephrine (adrenaline) levels to increase fat mobilization and diet support. Unfortunately, the over use of stimulants can cause a combination of undesirable side effects like adrenal fatigue, headaches, insomnia, irritability and anxiety. In addition, some people must avoid stimulants due to sensitivities or medical conditions, thus limiting options for these supplements.

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Interestingly, recent research has been investigating stimulant-free substances that produce diet-supportive effects. One such compound that has received significant scientific accolades in this department is L-carnitine. L-carnitine is essential as it is responsible for transporting fatty acids to the mitochodria to be oxidized. It is found naturally in animal products, with red meat and dairy products being the most abundant sources. In the world of L-carnitine supplements, the most notable and highly bioavailable forms are acetyl L-carnitine (ALCAR) and L-carnitine L-tatrate (LCLT). Scientists developed ALCAR and LCLT to be readily digested, which boosts L-carnitine bioavailability and absorption in skeletal muscle.

Past research has repeatedly shown that under exercise conditions, where glycolytic flux is high, there is a consistent decline in muscle carnitine content, which directly correlates with decreases in fat oxidation (van Loon et al., 2001;Roepstorff et al., 2005). In support, there is definitive evidence illustrating that when muscle carnitine levels fall, exercise induced fat mobilization is blunted (Stephens et al., 2006). A study published in the Journal of Clinical Endocrinology and Metabolism indicated that an acute increase in skeletal muscle total carnitine content (as noted with ALCAR or LCLT ingestion) results in greater use of body fat for an energy source, even under conditions of high carbohydrate availability (Stephens et al., 2006).

Additional support for L-carnitine comes from a study published in Metabolism involving slightly overweight males. The researchers concluded that L-carnitine supplementation resulted in increased fatty acid oxidation that was not accompanied by increases in protein catabolism (Wutzke & Lorenz, 2004). In a most recent article published in the prestigious Journal of Physiology, scientists from the University of Maastricht (The Netherlands) have conclusively shown that chronic ingestion of L-carnitine (2.0 g of LCLT two times per day) with 80 g of carbohydrates boosts skeletal muscle carnitine levels by 21% compared to baseline levels. Most intriguingly the researchers observed improvements in exercise performance and measured a substantive switchover to favor fat metabolism and glycogen sparing during low intensity and high intensity exercise.

Taken together, it seems that using an L-carnitine supplement like ALCAR or LCLT may prove beneficial for anyone who is concerned with physique improvement while preserving muscle mass. Based on the current scientific evidence, ALCAR and LCLT may augment the fat utilization effects of your workouts regardless of intensity.

Roepstorff C, Halberg N, Hillig T, Saha AK, Ruderman NB, Wojtaszewski JF, Richter EA, & Kiens B (2005). Malonyl-CoA and carnitine in regulation of fat oxidation in human skeletal muscle during exercise. Am J Physiol Endocrinol Metab 288, E133-E142.

Stephens FB, Constantin-Teodosiu D, Laithwaite D, Simpson EJ, & Greenhaff PL (2006). An acute increase in skeletal muscle carnitine content alters fuel metabolism in resting human skeletal muscle. J Clin Endocrinol Metab.

van Loon LJ, Greenhaff PL, Constantin-Teodosiu D, Saris WH, & Wagenmakers AJ (2001). The effects of increasing exercise intensity on muscle fuel utilisation in humans. J Physiol 536, 295-304.

Wall BT, Stephens FB, Constantin-Teodosiu D, Marimuthu K, Macdonald IA, Greenhaff PL. Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans: the dual role of muscle carnitine in exercise metabolism. J Physiol. 2011 Jan 4. [Epub ahead of print]

Wutzke KD & Lorenz H (2004). The effect of l-carnitine on fat oxidation, protein turnover, and body composition in slightly overweight subjects. Metabolism 53, 1002-1006 .