Some individuals with genetic or medical disorders (such as preterm infants) cannot make enough carnitine, requiring dietary supplementation. Preliminary clinical research indicates it may improve heart function in people with cardiovascular disease or neuropathy in people receiving chemotherapy. Despite common use among athletes to consume carnitine supplements for improved exercise performance or recovery, there is insufficient high-quality clinical evidence to indicate it provides any benefit. Despite widespread interest among athletes to use carnitine for improvement of exercise performance, inhibit muscle cramps, or enhance recovery from physical training, the quality of research for these possible benefits has been low, prohibiting any conclusion of effect. At supplement amounts of per day over a month, there was no consistent evidence that carnitine affected exercise or physical performance. Carnitine supplements do not improve oxygen consumption or metabolic functions when exercising, nor do they increase the amount of carnitine in muscle. In fact, contrary to various misconceptions, L-Carnitine also does not influence fat metabolism , i. e., burning out of fat without exercise. The carnitine content of seminal fluid is directly related to sperm count and motility, suggesting that the compound might be of value in treating male infertility. One study concluded that carnitine supplementation may improve sperm quality, and the reported benefits may relate to increased mitochondrial fatty-acid oxidation (providing more energy for sperm) and reduced cell death in the testes of mice subjected to physical stress to the testes. Cardiovascular and peripheral arterial diseases Several studies have approved the effectiveness of supplemental carnitine in the management of cardiac ischemia (restriction of blood flow to the heart) and peripheral arterial disease. If levels of carnitine are low in the failing heart muscle, supplemental amounts might counteract the toxic effects of free fatty acids and improve carbohydrate metabolism. Carnitine has had anti-ischemic properties when given orally and by injection. Atherosclerosis%DIFDELCMD < %DIFDELCMD < %%% Koeth et al., from the Cleveland Clinic reported that carnitine from animal flesh (four times as much in red meat as in fish or chicken), as well as phosphatidylcholine from egg yolk, are converted by intestinal bacteria to trimethylamine (the compound that causes uremic breath to smell fishy). Trimethylamine is oxidized in the liver to trimethylamine N-oxide (TMAO), which causes atherosclerosis in animal models. Patients in the top quartile of TMAO had a 2.5-fold increase in the 3-year risk of stroke, death, or myocardial infarction . A key issue is that vegans who consumed -carnitine did not produce TMAO because they did not have the intestinal bacteria that produce TMA from carnitine. Diabetes mellitus type 2 Type 2 diabetes, which is marked by insulin resistance, may be associated with a defect in fatty acid oxidation in muscle. Several studies suggest that carnitine supplementation may have a beneficial effect on glucose utilization and reduce diabetic neuropathy . End stage renal disease and hemodialysis The kidneys contribute to overall homeostasis in the body, including carnitine levels. In the case of renal impairment, urinary elimination of carnitine increasing, endogenous synthesis decreasing, and poor nutrition as a result of disease-induced anorexia can result in carnitine deficiency. Carnitine blood levels and muscle stores can become very low, which may contribute to anemia, muscle weakness, fatigue, altered levels of blood fats, and heart disorders. Some studies have shown that supplementation of high doses of -carnitine (often injected) may aid in anemia management. The form present in the body is -carnitine, which is also the form present in food. Food sources rich in -carnitine are animal products, particularly beef and pork. Redder meats tend to have higher levels of -carnitine. Adults eating diverse diets that contain animal products attain about 60–180 mg of carnitine per day. Vegans get noticeably less (about 10–12 mg) since their diets lack these carnitine-rich animal-derived foods. Approximately 54\% to 86\% of dietary carnitine is absorbed in the small intestine, then enters the blood. Even carnitine-poor diets have little effect on total carnitine content, as the kidneys conserve carnitine. Recommended intakes of carnitine In 1989, the Food and Nutrition Board concluded that carnitine wasn't an essential nutrient as healthy human liver and kidneys synthesize sufficient quantities of carnitine from lysine and methionine to meet up with daily body requirements without the need of consuming it from supplements or food. Also, the FNB has not established Dietary Reference Intakes (DRIs) for carnitine. Supplemental sources of carnitine -carnitine, acetyl--carnitine, and propionyl--carnitine are available in dietary supplement pills or powders  . It is also a drug approved by the Food and Drug Administration to treat primary and certain secondary carnitine-deficiency syndromes  .
Some individuals with genetic or medical disorders (such as preterm infants) cannot make enough carnitine, requiring dietary supplementation. Despite common use among athletes to consume carnitine supplements for improved exercise performance or recovery, there is insufficient high-quality clinical evidence to indicate it provides any benefit. Despite widespread interest among athletes to use carnitine for improvement of exercise performance, inhibit muscle cramps, or enhance recovery from physical training, the quality of research for these possible benefits has been low, prohibiting any conclusion of effect. At supplement amounts of per day over a month, there was no consistent evidence that carnitine affected exercise or physical performance. Carnitine supplements do not improve oxygen consumption or metabolic functions when exercising, nor do they increase the amount of carnitine in muscle. There is no evidence that L-carnitine influences fat metabolism or aids in weight loss. The carnitine content of seminal fluid is directly related to sperm count and motility, suggesting that the compound might be of value in treating male infertility. %DIFDELCMD < %DIFDELCMD < %%% Diseases Although there is some evidence from meta-analyses that L-carnitine supplementation improved cardiac function in people with heart failure, there is insufficient research to determine its overall efficacy in lowering the risk or treating cardiovascular diseases . There is only preliminary clinical research to evaluate the use of L-carnitine supplementation for improving symptoms of type 2 diabetes, such as improving glucose tolerance or lowering fasting levels of blood glucose . The kidneys contribute to overall homeostasis in the body, including carnitine levels. In the case of renal impairment, urinary elimination of carnitine increasing, endogenous synthesis decreasing, and poor nutrition as a result of disease-induced anorexia can result in carnitine deficiency. Carnitine blood levels and muscle stores can become very low, which may contribute to anemia, muscle weakness, fatigue, altered levels of blood fats, and heart disorders. Some studies have shown that supplementation of high doses of -carnitine (often injected) may aid in anemia management. The form present in the body is -carnitine, which is also the form present in food. Food sources rich in -carnitine are animal products, particularly beef and pork. Red meats tend to have higher levels of -carnitine. Adults eating diverse diets that contain animal products attain about 23-135 mg of carnitine per day. Vegans get noticeably less (about 10–12 mg) since their diets lack these carnitine-rich animal-derived foods. Approximately 54\% to 86\% of dietary carnitine is absorbed in the small intestine, then enters the blood. Even carnitine-poor diets have little effect on total carnitine content, as the kidneys conserve carnitine. -carnitine, acetyl--carnitine, and propionyl--carnitine are available in dietary supplement pills or powders , with a daily amount of of 0.5 to 1 g considered to be safe . It is also a drug approved by the Food and Drug Administration to treat primary and certain secondary carnitine-deficiency syndromes secondary to inherited diseasess .
D
Preliminary clinical research indicates it may improve heart function in people with cardiovascular disease or neuropathy in people receiving chemotherapy.
R
In fact, contrary to various misconceptions, L-Carnitine also does not influence fat metabolism , i. e., burning out of fat without exercise.
There is no evidence that L-carnitine influences fat metabolism or aids in weight loss.
D
One study concluded that carnitine supplementation may improve sperm quality, and the reported benefits may relate to increased mitochondrial fatty-acid oxidation (providing more energy for sperm) and reduced cell death in the testes of mice subjected to physical stress to the testes.
D
Cardiovascular and peripheral arterial diseases Several studies have approved the effectiveness of supplemental carnitine in the management of cardiac ischemia (restriction of blood flow to the heart) and peripheral arterial disease. If levels of carnitine are low in the failing heart muscle, supplemental amounts might counteract the toxic effects of free fatty acids and improve carbohydrate metabolism. Carnitine has had anti-ischemic properties when given orally and by injection.
D
Atherosclerosis
R
Koeth et al., from the Cleveland Clinic reported that carnitine from animal flesh (four times as much in red meat as in fish or chicken), as well as phosphatidylcholine from egg yolk, are converted by intestinal bacteria to trimethylamine (the compound that causes uremic breath to smell fishy). Trimethylamine is oxidized in the liver to trimethylamine N-oxide (TMAO), which causes atherosclerosis in animal models. Patients in the top quartile of TMAO had a 2.5-fold increase in the 3-year risk of stroke, death, or myocardial infarction
Diseases Although there is some evidence from meta-analyses that L-carnitine supplementation improved cardiac function in people with heart failure, there is insufficient research to determine its overall efficacy in lowering the risk or treating cardiovascular diseases
D
A key issue is that vegans who consumed -carnitine did not produce TMAO because they did not have the intestinal bacteria that produce TMA from carnitine.
R
Diabetes mellitus
There is only preliminary clinical research to evaluate the use of L-carnitine supplementation for improving symptoms of
R
Type 2 diabetes, which is marked by insulin resistance, may be associated with a defect in fatty acid oxidation in muscle. Several studies suggest that carnitine supplementation may have a beneficial effect on glucose utilization and reduce diabetic neuropathy
diabetes, such as improving glucose tolerance or lowering fasting levels of blood glucose
D
End stage renal disease and hemodialysis
R
Redder
Red
R
60–180
23-135
D
Recommended intakes of carnitine In 1989, the Food and Nutrition Board concluded that carnitine wasn't an essential nutrient as healthy human liver and kidneys synthesize sufficient quantities of carnitine from lysine and methionine to meet up with daily body requirements without the need of consuming it from supplements or food. Also, the FNB has not established Dietary Reference Intakes (DRIs) for carnitine.
D
Supplemental sources of carnitine
A
, with a daily amount of of 0.5 to 1 g considered to be safe
A
secondary to inherited diseasess