Carnitine is an amino acid derivative. It is a nutrient required for fat oxidation and energy production. It is seen in two isomeric forms. One is L-carnitine, which is a naturally occurring carnitine and other D-carnitine which is a synthetic one. Dietary supplements contain L-carnitine or DL-carnitine mixture. Dietary intake of carnitine for an omnivorous diet provides 100-300 mg of carnitine daily.
Although not an officially recognized vitamin, carnitine is also sometimes known as vitamin BT.
Sources of carnitine are meat and dairy products. Tempeh and avocados are also sources of carnitine. Fruits, vegetables and cereals are poor sources of carnitine. Most soy-based infant formulas are supplemented with carnitine. Actions of carnitine include regulation of fatty-acid chain transport through cell membranes; facilitation of beta-oxidation of long chain fatty-acids and keto acids; transportation of acyl-CoA compounds.
As such carnitine is synthesized in sufficient quantities to meet human requirements by liver, brain and kidney from essential amino acids like lysine and methionine. The dietary carnitine gets absorbed rapidly from intestine by both passive and active transport mechanisms.
There are basically two types of carnitine deficiency: primary and secondary deficiency. Primary type arises due to impairment in the membrane transport of carnitine and this leads to muscle weakness as muscle lacks the carnitine, recurring episodes of coma, hypoglycaemia in infants and children, encephalopathy and cardiomyopathy. Secondary type occurs due to inherited disorder in metabolism of carnitine. It should be not mistaken that as plant foods are poor sources of carnitine, vegetarians might be prone to carnitine deficiency because the endogenous synthesis in our body balances the level of carnitine required.
A slightly different form of carnitine, called acetyl carnitine is better than carnitine as an anti-oxidant as it improves coenzyme Q-10 level and protects the mitochondria from damage. It also acts as a ‘shuttle’ for long chain fatty acids to the mitochondria, where they are converted into energy.
Health benefits of Carnitine
Cardiac benefits : heart muscle obtain energy from the fatty oxidation. As seen earlier, carnitine is a good source of fatty oxidation. Thus supplementation with carnitine raises the heart carnitine levels allowing the heart to use limited oxygen supply more efficiently. Carnitine therefore is being effectively used to treat atherosclerosis, angina and coronary heart disease. Carnitine also decreases blood fat basically be decreasing the low-density-lipoprotein and increasing the high-density-lipoprotein. So it can help patients with angina and some type of muscle disease.
As neuroprotective agent- acetyl L-carnitine is a derivative of carnitine. This acetyl L-carnitine is a neuroprotective agent. It improves the cognitive defects associated with forms of senility and age-related depression.
- L-carnitine is seen to mimic the actions of gluco-corticoid in-vivo. It reduces the glucocorticoid receptor affinity for steroid ligand; suppresses receptor mediated tumor necrosis factor and interleukin-12 release. All these effects are concentration dependent.
- L-carnitine acts as a peripheral antagonist of thyroid hormone in some tissues. It inhibits thyroid entry into cell nuclei. It is shown to reverse or prevent some symptoms of hyperthyroidism in a controlled clinical study.
- It modulates the aging process by slowing down the progression of neurodegenerative diseases.
- L-carnitine supplementation in patients undergoing haemodialysis shows improved lipid metabolism, antioxidant status, anaemia requiring erythropoietin, and reducing muscle cramps and muscle weakness.
Possible uses of carnitine
- In cardiovascular disease – carnitine supplementation is investigated for its effect in cardiac disorders. One study showed that oral supplementation of L-carnitine improved the symptoms of angina, reduced the angina attacks, as well as gylceryl trinitrate consumption. Another study also showed that carnitine supplementation improved the heart rate, arterial pressures, and proved beneficial to patients having congestive heart failure (CHF) by reducing the dyspnoea, oedema and increasing the diuresis. Also it reduced the daily digoxin dose in those patients.
- Hyperlipidaemia – study shows that carnitine supplementation reduced the blood cholesterol levels or triglycerides or both and simultaneously increased the level of HDL cholesterol. Therefore, it proved beneficial for curing Hyperlipidaemia that leads to atherosclerosis or heart stroke if not treated early.
- Exercise performance – carnitine shows the potential of increasing the lipid utilization in the body and conserving the glycogen supplies in the muscles and henceforth, improves the athletic performance. But when placebo studies were conducted it showed no effect in exercise performance in healthy patients.
- Chronic fatigue syndrome – it is seen that people suffering from chronic fatigue syndrome have low carnitine levels. So supplementation of carnitine to such showed improved clinical parameters. However, there is no statistical observation for this.
- Alzheimer’s disease – placebo controlled trials showed that carnitine supplementation could reduce the deterioration symptoms of Alzheimer’s disease. However, many trials resulted in poor or vague description of treatment of dementia. At present, there is less evidence to recommend carnitine clinically for treating this disorder.
- Miscellaneous – there are some evidences that states carnitine effect in improving insulin resistance in type-2 diabetes; promising effect in treating pain in diabetic neuropathy; treatment of epilepsy; complementing the anti-retroviral therapy in HIV patients. Studies are still going on.
Adverse effects, Interactions and Precautions
Adverse effects – high doses of carnitine can cause nausea, vomiting, diarrhea. Serious toxicity is also reported especially greater with D-isomer that the L-carnitine. Ingestion of DL-carnitine is reported to cause myasthenia also.
Abdominal cramps and ‘fish-odor-syndrome’ are also seen in some cases.
Interactions – carnitine interacts with some drugs such as anticonvulsants, Pivampicillin, Pivmecillinam. All the drug interaction stated above causes increased excretion of carnitine.
Precautions – no problems have been reported in pregnant and breast feeding women but sufficient study to guarantee its safety is not yet established so you should be careful. D-isomer or the DL-mixture tends to interfere with the normal function of L-isomer, so only L-isomer should be used in studies also.
Safe Dose – dose is not established. L-carnitine supplementation is available in the form of tablets and capsules. Daily dose of 1-6 gram of L-carnitine have been used.
As discussed above, it can be concluded that carnitine specifically L-carnitine has many health benefits from antioxidant property to modulation of gene expression. It has a lot many meaningful physiological uses. And still more clinical trials are going on to discover more of its utility in medicinal field to promote better health