Carnitine
What is it?
Carnitine is a vitamin-like compound with a structure similar to an amino acid. It is found in food, particularly in meat and dairy products, and can also be made by the body from the amino acid, lysine.
What it does in the body
Carnitine is essential for fat metabolism as it transports fatty acids into the mitochondria, where they are 'burned' to release energy for body functions. Carnitine thus increases the use of fat as an energy source.
Deficiencies
Carnitine deficiency may occur due to genetic defects, reduced absorption, dietary deficiency of precursors, and increased requirements due to stress, medication use or disease.
Supplements
Only the L-carnitine form should be used as the D form of carnitine may cause adverse side effects. L-carnitine is available in several different forms including L-propionylcarnitine and L-acetylcarnitine.
Therapeutic uses of supplements
Supplements are used to treat carnitine deficiency.
Cardiovascular disease
Carnitine can be used to treat several types of cardiovascular disease.
Angina
In a 1994 study, Dutch researchers assessed the effect of L-propionylcarnitine on ischemia in 31 untreated male patients with left coronary artery disease. The patients were studied during two identical pacing stress tests 45 minutes before and 15 minutes after administration of 15 mg/kg of L-propionylcarnitine or placebo. The results showed that the L-propionylcarnitine prevented ischemia-induced heart dysfunction through its enhancement of metabolism.1
Recovery from heart attack
Carnitine deprivation occurs in heart muscle during heart attack and some studies suggest that supplementation has a beneficial effect on heart function. In a 1995 study, Italian researchers investigated the effects of L-carnitine on heart function in 472 heart attack patients. The patients received either placebo or L-carnitine within 24 hours of the onset of chest pain. The treatments were given at a dose of 9 g per day intravenously for the first five days, and then 6 g per day orally for the next 12 months. The results showed that heart function was better in the carnitine-treated group than in the placebo group. There was a lower incidence of congestive heart failure and fewer deaths in the carnitine- treated group.2
Other types of cardiovascular disease
Carnitine supplements have also been used to treat cardiomyopathy, congestive heart failure, peripheral vascular disease, dyslipidemia, diabetes and arrhythmias. Propionyl-L-carnitine has shown beneficial effects in the treatment of intermittent claudication.3
It can also be used to lower blood fat levels, aid in weight loss, and improve muscle strength in some cases of weakness. A 1997 Italian study showed that carnitine supplements improved glucose metabolism in healthy people.4
Alzheimer's disease
There are several studies which suggest that acetyl-L-carnitine may delay the progression of Alzheimer's disease.5 In a small double-blind trial published in 1995, seven patients with probable Alzheimer's disease received 3 g/day of acetyl-L-carnitine for one year, while five similar patients were given a placebo. Patients treated with acetyl-L-carnitine showed significantly less deterioration on mental status tests than did patients receiving the placebo.6
Interactions
Interactions with other nutrients
Vitamin C, niacin and vitamin B6 are required for carnitine synthesis from lysine. Carnitine may work with coenzyme Q10. Choline supplementation seems to reduce urinary excretion of carnitine.7
Cautions
Carnitine is not recommended in people with active liver or kidney disease, or with diabetes.