New Focus on L-Carnitine
Spotlights Muscle and Energy
by Dallas Clouatre, Ph.D.
Sometimes, a well known and valued supplement is reformulated to provide significant new benefits. Such is the case with L-carnitine. Propionyl-Lcarnitine is a form that until recently was restricted to medical uses. Under the name GPLC™, it is now available more readily as the patented compound, glycine propionyl-L-carnitine hydrochloride. This L-carnitine form focuses on muscular energy, exercise recovery, and reducing fatigue.
What is L-carnitine?
An amino acid, L-carnitine is supplied in limited quantities by the diet and manufactured in the body, mainly in the liver and the kidneys. Supplementing offers numerous benefits as a cellular deficiency of L-carnitine can lead to symptoms such as fatigue, muscle weakness, obesity, plus elevated blood lipid and triglyceride levels. Jeffrey Bland, Director of the Bellevue Medical Laboratory, has argued that proper L-carnitine supplementation while dieting can help control the negative effects of ketosis (the accumulation of waste from fat metabolism). There is also evidence that some forms of obesity may be related to a genetic propensity to produce less L-carnitine. Liver and kidney problems will similarly reduce the body's production since as much as 80% of L-carnitine is produced by these organs. Fi n a l l y, L- carnitine penetrates the mitochondria. It is here that most free radicals generated as food are oxidized to produce energy. L-carnitine protects antioxidants and reduces free-radical damage.
Some researchers argue that supplemental L-carnitine does not increase the amount of fatty acids used for energy except in cases of a deficiency. Some of the mixed results in studies have been attributed to using the wrong forms and doses of carnitine. It's now understood that L-carnitine has two particularly active forms, although they are active for different purposes. Acetyl-L-carnitine is especially active in neuronal tissues, whereas propionyl-Lcarnitine is especially active in lean muscle tissue. The form of L-carnitine used must correspond with the particular condition or reason for its use.
Acetyl-L-carnitine, found in Jarrow Formulas' Acetyl-L-Carnitine 500, is involved in the same metabolic functions as is L-carnitine in its other forms, but acetyl-L-carnitine offers greater general protection at 500 mg for the brain and nervous system. As an antioxidant, acetyl-L-carnitine protects neurons from damage caused by superoxide radicals. One reason may be that the molecular structure of acetyl-L-carnitine resembles that of the neurotransmitter, acetylcholine. Research on preventing age-related mitochondrial decay and mental ability decline—perhaps even reversing some instances of mental decline— has stressed the combination of acetyl-Lcarnitine and alpha-lipoic acid, such as that found in Jarrow Formulas' ALCA™ 500 ALA 100.
What About Propionyl-L-carnitine?
Propionyl-L-carnitine has its own set of strengths. It is used to manage peripheral vascular disease, atherosclerotic and diabetic angioplasties, and congestive heart failure. In combination with acetyl-L-carnitine, propionyl-L-carnitine is used for symptoms of chronic fatigue syndrome and age-related testosterone deficiency. In fact, it seems to lessen symptoms of male hormone decline in older men, which reduces instances of sexual dysfunction, depression, and fatigue—but without the side effects of testosterone supplementation.
The focus of propionyl-L-carnitine, therefore, is on the muscles, such as the heart and on the vascular system, which is particularly helpful to athletes. Compared with at least one other form, propionyl-L-carnitine appears to produce greater increases in cellular L-carnitine concentrations. Researchers believe that it is transported more easily into muscle fibers and may better support uscle-cell energy production, perhaps because it increases the flow of pyruvate (a co-factor) into the Krebs Cycle to start it. Propionyl-L-carnitine also exhibits significant free-radical scavenging activity and helps prevent blood from coagulating too readily. The availability of GPLC, in Jarrow Formulas' GPLC, as a non-medical (less concentrated) source of propionyl-L-carnitine is good news. And one should not forget that the amino acid, glycine (which is part of GPLC), is useful in the liver's detoxification processes.
In short, GPLC offers both the benefits of ordinary L-carnitine and improved musclespecific benefits to all looking or needing to improve blood flow and energy.