L-carnitine and energy production -
Supplementation may help improve L-carnitine levels in a failing heart, which could boost heart health and circulation in the short term following a heart attack.
Supplementation may also help with symptoms of heart failure, such as chest pain and arrhythmia. At times, cancer treatments, such as chemotherapy, may cause a person to become deficient in L-carnitine.
In these cases, L-carnitine supplements may help reduce symptoms such as fatigue and weakness. Researchers are currently studying the compound as a possible way to prevent tissue damage due to chemotherapy, but this research is in the early stages. As the kidneys and liver help create and use L-carnitine, disease in these organs or organ failure may lead to L-carnitine deficiency.
Doctors may recommend L-carnitine supplementation in these cases to support the function of the kidneys and liver and prevent deficiency. Most people tolerate L-carnitine well. However, some individuals may experience digestive side effects when taking L-carnitine. These include :. Some studies suggest that high levels of L-creatine may raise the long-term risks of cardiovascular diseases, such as atherosclerosis.
L-carnitine supplements may interact with certain antibiotics or anticonvulsants. Anyone considering taking L-carnitine should talk to their doctor to discuss any medications they are taking and the possible drug interactions. The National Institutes of Health NIH note that healthy people do not need extra L-carnitine from food or supplements.
The liver and kidneys will create enough to meet their daily needs. Even though the body produces it naturally, carnitine is widely available in a number of simple foods. Animal proteins, such as fish, red meat, and poultry, are some of the best sources.
According to the NIH , adults who eat a mixed diet that includes red meat and other animal products get about 60— milligrams mg of carnitine per day. People who avoid animal products, such as those following a vegan diet, may get roughly 10—12 mg from their diet.
The kidneys also eliminate excess carnitine through urine to maintain healthful concentrations. Generally speaking, otherwise healthy adults do not need to take L-carnitine to support their health.
Some athletes take extra L-carnitine, believing that it will boost their athletic performance. L-carnitine availability seems to limit muscle metabolism during very high intensity exercise. So, in theory, supplementing carnitine during workouts may support exercise performance.
However, a study in Molecules notes that the evidence for this practice is lacking. While many athletes take L-carnitine, years of research does not provide conclusive evidence to support these claims. As L-carnitine helps burn fatty acids for energy, many people assume that taking more of it may help them lose weight.
More research is necessary, but some studies support this idea. In a review of nine different trials, researchers found some evidence to support this claim. They suggest that participants who took L-carnitine lost an average of 1. However, L-carnitine cannot replace healthful habits, such as a proper diet and regular exercise.
People who wish to take L-carnitine should talk to a doctor first. The doctor may have additional recommendations to support any treatment that the person needs and can help them avoid possible reactions and interactions.
The recommended dosage is roughly 1—3 grams per day. However, people with genetic abnormalities or other conditions causing a lack of L-carnitine should talk to their doctor for a more specific dosage.
L-carnitine is an amino acid that the body naturally produces. In people with good health, the liver and kidneys produce and store enough of the compound to prevent deficiency. People with L-carnitine deficiencies may need to get the compound through their diet or as a supplement.
It is advisable to talk to a doctor before taking an L-carnitine supplement. Some people may wish to take L-carnitine supplements for their potential benefits, such as aiding athletic performance or weight loss.
However, more research is necessary to confirm these benefits. Carnitine occurs in almost every cell in the body and in most foods. It may help treat a range of health conditions. Find out more about its benefits.
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Clinical trials examining the effects of carnitine supplements on CVD have had mixed results. A meta-analysis of 13 clinical trials included a total of 3, adults with acute myocardial infarction who took either L-carnitine from 2.
The study found that L-carnitine significantly reduced rates of all-cause mortality, ventricular arrhythmias, and new-onset angina but did not affect risk of heart failure or myocardial reinfarction [ 34 , 36 ].
The carnitine dose and duration of the clinical trial did not appear to affect outcomes. These benefits did not vary by supplement dose or study duration. However, L-carnitine did not affect rates of all-cause mortality or performance on a timed walking test. Other research has raised concerns about the negative cardiovascular effects of chronic exposure to carnitine.
A study that included 2, adults age 54—71 years undergoing elective cardiac evaluation found that L-carnitine is metabolized by intestinal microbiota to trimethylamine-N-oxide TMAO , a proatherogenic substance that is associated with increased CVD risk [ 38 ].
Because of differences in intestinal bacteria composition, omnivorous study participants produced more TMAO than vegans or vegetarians after consumption of L-carnitine. The study also found dose-dependent associations between fasting plasma L-carnitine concentrations and risk of coronary artery disease, peripheral artery disease, and CVD, but only in participants with concurrently high TMAO levels.
A clinical trial also found potentially deleterious outcomes in individuals age 58 to 75 years with metabolic syndrome who received 1 g supplemental L-carnitine or placebo twice a day for 6 months [ 39 ].
Although the results showed no differences in total plaque volume between groups, total cholesterol and low-density lipoprotein cholesterol levels were higher in participants taking L-carnitine.
L-carnitine supplementation was also associated with 9. Peripheral artery disease is a vascular disorder usually caused by atherosclerosis and its resulting arterial stenosis and occlusion.
It is prevalent among older adults, although it is often underdiagnosed [ 40 , 41 ]. Researchers have examined whether propionyl-L-carnitine, an acyl derivative of L-carnitine, mitigates the cramping leg pain of intermittent claudication, the main symptom of peripheral artery disease, but findings from studies have been mixed.
In one trial, participants supplemented with propionyl-L-carnitine had improved peak walking times walking until pain could not be tolerated , self-reported improvements in walking distance and speed, and decreased pain.
The other two trials showed no benefit of propionyl-L-carnitine on peak walking time compared with placebo. Insulin resistance plays an important role in the development of type 2 diabetes. Because insulin resistance may be associated with mitochondrial dysfunction and a defect in fatty-acid oxidation in muscle [ 43 , 44 , 45 , 46 ], carnitine supplementation has been studied for its possible effects on insulin resistance and diabetes.
A meta-analysis of 41 randomized clinical trials examined the effects of L-carnitine supplementation on glycemic markers in 2, men and women age 18 years and older [ 47 ].
Most participants had health conditions such as type 2 diabetes, obesity, polycystic ovary syndrome, or nonalcoholic fatty liver disease. L-carnitine supplements at doses of 0. Other meta-analyses have had a narrower focus, examining only studies in specific populations.
The L-carnitine improved measures of insulin resistance, and the benefits at 12 months exceeded those at 3 months. A systematic review and meta-analysis of four randomized clinical trials all of which were included in the meta-analysis described above with a total of adults with type 2 diabetes compared the metabolic effects of L-carnitine with those of placebo [ 44 ].
Additional clinical trials with larger samples are needed to determine whether L-carnitine supplements can reduce the risk of diabetes or the severity of its clinical manifestations. Carnitine might play a role in sperm maturation, sperm motility, and spermatogenesis [ 49 ]. It might also reduce oxidative stress, which could improve oocyte growth and maturation [ 50 ].
Therefore, researchers are examining whether supplemental carnitine improves sperm count, concentration, and motility as well as pregnancy rates. Compared to placebo, supplemental carnitine improved sperm motility by 7. A Cochrane Review assessed the effectiveness of carnitine supplementation on male subfertility delays in conception due to low sperm concentration [ 52 ].
In some trials, carnitine was compared with placebo, whereas in others, it was compared with antioxidants such as vitamin C or vitamin E or a control group that received no treatment. Carnitine supplementation increased sperm motility and concentration at some timepoints e. Researchers have also examined whether carnitine might improve ovulation and pregnancy rates in females with polycystic ovary syndrome PCOS , a condition that commonly causes infertility.
Individuals in the group taking L-carnitine had In addition, more participants in the L-carnitine group became pregnant than those who took placebo, and they had fewer miscarriages.
In a 3-month randomized controlled trial, women with PCOS received either 3 g L-carnitine or placebo [ 54 , 55 ]. Participants who took L-carnitine supplements had improved menstrual cycle regularity and higher ovulation and pregnancy rates, but miscarriage rates did not differ between the groups.
More research is needed to determine whether carnitine supplements affect male infertility or pregnancy rates in women with PCOS. Some research suggests that carnitine reduces levels of C-reactive protein, a biomarker of systemic inflammation, and levels of malondialdehyde, a lipid peroxidation product that induces pain and disability in patients with osteoarthritis [ 56 ].
In addition, levels of acylcarnitines conjugated carnitine esters are lower in people with osteoarthritis than in age- and gender-matched healthy individuals [ 57 ]. For these reasons, investigators are studying whether L-carnitine supplements can relieve osteoarthritis symptoms [ 56 , 58 ], but study results have been mixed.
A randomized clinical trial examined the anti-inflammatory effects of L-carnitine supplementation for osteoarthritis management in 69 women age 40 to 60 years with mild to moderate osteoarthritis in both knees [ 59 ].
The women took mg L-carnitine three times a day or placebo for 8 weeks. Serum levels of several inflammation biomarkers and pain scores were lower in the carnitine group than in the placebo group: Interleukinbeta levels decreased 5. In comparison with placebo, carnitine did not reduce osteoarthritis pain or stiffness or increase physical function.
Larger studies with samples that include both men and women are needed to determine whether carnitine supplementation helps manage osteoarthritis symptoms.
Carnitine helps preserve muscle glycogen and promote fat oxidation. It also spares the use of amino acids as energy sources during exercise, making them potentially available for new protein synthesis [ 6 ], and decreases the accumulation of lactate [ 60 ].
However, research findings on the effectiveness of supplemental carnitine on athletic performance are mixed [ 6 ]. One study randomly assigned 14 recreational athletes age 24—28 years with an average body mass index BMI of 23 to consume a carbohydrate solution with or without 2.
In another study, 24 men age 18—40 years eight omnivores and 16 vegetarians took 1 g L-carnitine twice daily for 12 weeks [ 62 ]. Carnitine supplementation had no significant effect on VO2max, blood lactate concentration, skeletal muscle energy metabolism, or physical performance in either the vegetarians or the omnivores.
A comprehensive review summarized the effects of supplemental L-carnitine on exercise performance and recovery in well-trained athletes age 16—36 years and recreationally active adults age 18—50 years [ 63 ].
The review included 11 clinical trials one of which was the trial described above in a total of well-trained athletes who took 1 to 4 grams L-carnitine or placebo a single time or once or twice daily for up to 6 months. L-carnitine supplements reduced lactate levels and heart rate; increased lipid metabolism, VO2max, oxygen consumption, and L-carnitine plasma concentrations; improved performance; and hastened recovery in some of the studies.
However, the supplements did not affect performance or maximal exercise test results in other studies. In 17 studies that included recreationally active adults, a total of participants took 2 g L-carnitine once or 2 to 4 g L-carnitine or placebo once or twice daily for up to 3 months.
L-carnitine decreased plasma lactate concentrations, pyruvate concentrations, and muscle soreness and increased VO2max and recovery in some studies. However, in other studies, L-carnitine did not affect lactate, heart rate, VO2max, endurance, performance time, or perceived exertion during exercise.
A systematic review of 11 randomized clinical trials examined the effects of oral L-carnitine supplementation on high- and moderate-intensity exercise performance in a total of physically active and untrained adults age 18 to 46 years [ 64 ].
The studies had mixed results. Some studies found significant improvements in VO2max, peak power, maximum sprinting power, perceived exertion, and number of repetitions and volume lifted in a leg press in the L-carnitine group. However, other studies found no differences in VO2max, fatigue, maximum and average power, or total work on a cycle ergometer.
No studies found that L-carnitine supplementation improved moderate-intensity exercise performance. Because carnitine transports fatty acids into the mitochondria and acts as a cofactor for fatty acid oxidation, researchers have proposed using L-carnitine supplements to promote weight loss, often in conjunction with a low-calorie diet, exercise, or prescription weight-loss drugs [ 65 ].
Weight loss has been a secondary outcome in most studies, and these studies have had equivocal results. The trials included a total of participants.
In eight trials, doses ranged from 1. Study participants who took carnitine supplements lost an average of 1. Carnitine does not have an established tolerable upper intake level.
It can also cause muscle weakness in people with uremia and seizures in those with seizure disorders. Some research indicates that intestinal bacteria metabolize unabsorbed carnitine to form TMAO and gamma-butyrobetaine [ 68 ], which might increase the risk of CVD [ 38 , 39 , 69 , 70 , 71 ].
This effect appears to be more pronounced in people who consume meat than in vegans or vegetarians.
l -Carnitine plays a key role in the regulation of energy L-carnitine and energy production producion growth in fish. L-carnifine aim of this study rpoduction to determine Astaxanthin and blood pressure productiin of abd l -carnitine levels on carnitine homeostasis L-carnitine and energy production energy metabolism in Successful weight management and triploid trout Oncorhynchus mykiss. Diploid and triploid trout l -Carnitine caused no significant change in the plasma concentrations of metabolites like proteins ammonia, urea and proteinlipid triglyceridescarbohydrate glucose, lactate and enzyme activities lipase, lactate, alanine transaminase, lactic acid dehydrogenase. In conclusion, ploidy significantly affected the energy metabolism in rainbow trout, dietary l -carnitine levels altered the l -carnitine homeostasis, but not influence nutritional metabolism. Abdallah Tageldein Mansour, Ahmed H.
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