L-carnitine is a conditionally essential amino acid because the body can synthesize it but may need to obtain it from the diet in times of high energy needs. The liver and kidneys synthesize L-carnitine from the amino acids lysine and methionine; dietary L-carnitine comes primarily from meat and dairy foods.
Dosage
As a dietary supplement, L-carnitine is available in varying dosages generally ranging up to 1 g per capsule or tablet. Studies examining the potential effects of L-carnitine on health conditions commonly use 1 to 6 g per day, for up to six consecutive months.
Weight Loss
A primary role of L-carnitine in the body is to help shuttle long-chain fatty acids across mitochondrial membranes inside cells so they can be oxidized to produce energy. Because of this, many companies have used L-carnitine in weight loss formulations. Unfortunately, there is little evidence that increasing L-carnitine in the body will increase fat burning to a significant enough level to reduce body weight.
Cardiovascular Health
Supplementing L-carnitine may have heart health benefits. Studies have demonstrated improved exercise tolerance with chronic stable angina, decreased mortality and other complications after myocardial infarction or myocarditis, and reduced symptoms with congestive heart failure. Failing myocardium tissues have been observed as being deficient in L-carnitine.
End-Stage Renal Disease
A use of L-carnitine approved by the U.S. Food and Drug Administration involves patients with end-stage renal disease, whose kidney function is near or in complete failure. Treatment for end-stage renal disease requires either dialysis or a kidney transplant. Supplementation of L-carnitine can help increase red blood cell and hemoglobin counts, while also preventing carnitine deficiencies in those receiving dialysis.
Other Uses
Use of supplemental L-carnitine has also been indicated for peripheral vascular disease, attention-deficit/hyperactivity disorder, Rett syndrome and several disease-related fatigues. More studies will be needed to determine the benefits for those with these conditions.
Risks
Gram doses of L-carnitine can result in mild gastrointestinal upset or body odor. It may function as a thyroid hormone antagonist by blocking its entry into the nucleus of cells. Those who have a history of seizures should be aware that L-carnitine may possibly increase frequency and/or severity of seizures. L-carnitine may have interactions with several medications.
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