Acetyl-L-carnitine is important to energy production in the body and can be found in its highest concentration in the skeleton and heart muscle. It is produced by the liver and kidneys. It is not regarded as an essential nutrient and as a result no dietary recommended intake for it has been set.
The body makes sufficient carnitine to meet the needs of most people. Premature babies do not produce enough carnitine. It naturally occurs in meat, fish, poultry, and milk. There have been no studies positively linking carnitine supplementation to improved athletic performance despite its popularity in sport circles.
Some studies have linked acetyl-L-carnitine supplementation to improved mental function and reduce deterioration in older adults with mild cognitive impairment and Alzheimer’s disease when taken for between 3 and 12 months. Some clinical trials back up the use of acetyl- L-carnitine to reduce mortality in patients who had heart attacks and supplementing also seemed beneficial for heart rhythm disturbances and angina. It did not reduce the risk of heart failure or a repeated heart attack.
Patients receiving chemotherapy and who were carnitine-deficient benefitted from supplementation and reported less fatigue during treatment. Supplementation also proved to be beneficial for diabetic neuropathy in the beginning stages of the disease.
Some studies also suggest that supplementing with Acetyl-L-carnitine can slow down the progression of HIV by reducing the number of white blood cells dying.
There are some reported side-effects from taking 3 grams of carnitine as a supplement. These include nausea, vomiting, abdominal cramps and diarrhoea.
At doses of approximately 3 g/day, carnitine supplements can cause nausea, vomiting, and abdominal cramps.
A study involving just fewer than 800 patients showed that L-acetyl-carnitine supplements can significantly decreases depressive symptoms compared with a placebo or no intervention and that this effect was especially pronounced in older adults.