Carnitine (L-carnitine) is a non-essential organic acid that is synthesized in the body from the amino acids lysine and methionine and is mainly found in red meats and dairy products. It is also widely available as an over-the-counter nutritional supplement which is claimed to improve energy, weight loss, and athletic performance. Its potential role in treating heart disease was first reported in the late 1970s. It is important to remember that the synthesis of carnitine is highly dependent on adequate amounts of vitamin C in the body. Carnitine also plays a role in the production of acetylcholine, an important neurotransmitter. Carnitine reduces red blood cell fragility, erythropoietin resistance, enhances bone marrow, and is very important in fat energy metabolism.

Elderly people may suffer from a relative carnitine deficiency (inadequacy). Serum levels of carnitine tend to increase until approximately the age of 70, after which they decline for unclear reasons. The decline is correlated with lean body mass. It has been shown that supplementation with 2 grams of carnitine per day is associated with less fatigue and a better body composition in the elderly and can increase muscle function.

During ischemic events carnitine levels are depleted. In one study, investigators sought to determine the effects of targeting cardiac metabolic pathways using carnitine to improve free fatty acid levels and glucose oxidation in these patients. By performing a systematic review and meta-analysis of the available studies published over several decades, carnitine was shown to be beneficial, significantly improves cardiac health in patients after a heart attack (The Mayo Clinic Proceedings). Their findings, based on the analysis of controlled trials, associate carnitine with significant reduction in death from all causes and a highly significant reduction in ventricular arrhythmias and angina attacks following a heart attack.

Even more a 2016 study showed that L-Carnitine supplementation at a dose of 1000 mg/d exhibited significant increases in HDL-C and ApoA1 levels and a slight decrease in TG levels. This lipid-lowering effect may be related to its antioxidant ability.