Carnitine is a vitamin-like compound however it is also considered a non- essential amino acid as it can be made by the body from the essential amino acid lysine. Demand for carnitine often exceeds the rate of synthesis making supplements important. Carnitine is predominantly found in meat & dairy produce. Carnitine is available in different forms however L- carnitine is the most widely used and is considered the best-studied form. There is no established Recommended Daily Amount (RDA) for Carnitine however dosage ranges are considered to be in the region of 1,500 and 4,000mg in divided doses.
Carnitine is responsible for the transport of long chain fatty acids in the mitochondria (the battery powerhouse of each cell) where they are burned to be used as energy. Carnitine thus increases the use of fat as an energy source which helps to prevent fatty build up in the heart, liver and skeletal muscles.
Deficiency states are rare in adults and usually, only occur as a systemic (whole body) deficiency as opposed to myopathic (muscle) deficiency and is secondary to a factor other than an inability to make carnitine. Deficiency in children, however, is more common as they are unable to adapt to low carnitine levels as well as adults. Symptoms of carnitine deficiency include enlarged heart, fatigue and weakness, abdominal cramps, loss of appetite, gastrointestinal disturbances which may include nausea and vomiting, abdominal pain and diarrhoea and in children symptoms manifest clinically resembling a condition known as Reye’s syndrome, characterised by acute brain swelling with altered liver function. Symptoms include loss of muscle tone, failure to thrive, recurrent infection, hypoglycaemia and heart disturbances.
The majority of research relating to the use of L carnitine supplementation is associated with the potential benefit in various cardiovascular diseases, enhancing physical performance, Alzheimer’s, Age Related Senility and kidney disease (1).
Cognitive function– A meta-analysis of studies suggests that supplements of acetyl-L-carnitine may improve mental function and reduce deterioration in older adults with mild cognitive impairment and Alzheimer’s disease (2) In these studies, subjects took 1.5–3.0 grams/day of acetyl-L-carnitine for 3–12 months.
Cardiovascular Health – The effectiveness of supplemental carnitine in the management of cardiac ischemia (a condition which consists of reduced blood flow to the heart) and peripheral arterial disease (a condition which involves narrowing of the arteries which supply the limbs) has been subject of much research. Studies undertaken suggest L carnitine supplements may counteract the toxic effects of free fatty acids and improve carbohydrate metabolism (3). A clinical trial involving 2,330 patients with acute anterior myocardial infarction (heart attack) showed treatment with L-carnitine significantly reduced death rates compared to the placebo group (4). The results of the study were combined with 12 other smaller trials which concluded that treatment with L-carnitine in patients experiencing an acute myocardial infarction (heart attack) reduces all-cause deaths by 27%, ventricular arrhythmias (irregular heartbeats) by 65%, and angina (chest pain caused by reduced blood flow to the heart muscle) by 40% over a follow-up period of 2 months (5).
Side effects of chemotherapy– Carnitine is thought to be deficient in those experiencing fatigue resulting from chemotherapy (6). Treatment with carnitine supplements has been shown to be beneficial in relieving fatigue, improving mood and quality of sleep in terminal cancer patients (6) (7).
Diabetes– Early research suggests that supplementation with L-carnitine may improve insulin sensitivity in diabetics (8) (9) and (10).
HIV– In HIV-infected individuals L carnitine has been shown to slow HIV progression by slowing down the death of white blood cells known as lymphocytes (11), (12).
Male fertility– Several studies indicate that carnitine oral supplementation with L- carnitine may improve sperm quality and therefore male fertility (13), (14) and (15).
Fat Burning and Endurance– Carnitine is stored primarily in the skeletal muscles where it is needed to transform fatty acids into energy for muscular activity. Carnitine is utilised to transport fatty acids into the cells. It also increase the rate at which the liver uses fat, an energy generating process. With Carnitine’s effect on fatty acids and energy production, especially in the muscles, it is a popular supplement for supporting weight loss programmes, and has been linked with helping cellulite, due to its action in converting fats into energy.
Lactic Acid and Oxygen Uptake– Supplementing with L-carnitine may help lessen the likelihood of experiencing muscle soreness as it reduces the tendency of the body to create lactic acid and it may help to improve a person’s athletic performance by increasing the body’s oxygen uptake (i.e. it raises a person’s fitness rating). This may help to delay fatigue.
Heart Function and Circulation– Anecdotal reports suggest L-carnitine may help to strengthen the heart muscle and promote circulation, making it popular with people suffering from high blood pressure and other circulatory problems. Therefore, it may help to protect individuals from heart disease.
Brain Function-L-carnitine has been anecdotally linked with delaying the progression of Alzheimer’s disease, improving low mood related to senility and other forms of dementia, and improving memory in the elderly.
Fertility– L-carnitine may be helpful in increasing semen quality, sperm concentration and sperm mobility, meaning that if dietary intake is low, male infertility problems may be linked. Also, the Acetyl form of L-carnitine is believed to help restore menstruation.
Fibromyalgia-may improve musculoskeletal pain, depression and general health in people with fibromyalgia.
L carnitine is considered to be extremely safe with no significant side effects reported in human studies. However, the D form, which is the mirror image of the L form has been associated with interfering with the L form, producing symptoms such as muscle pain and loss of muscle function. It is therefore recommended to avoid the D form. There is no established Tolerable Upper Intake Level for Carnitine.