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L-Carnitine for Sports & Fitness

Why Use

L-Carnitine

Why Do Athletes Use It?*

Some athletes say that L-carnitine improves athletic performance.

What Do the Advocates Say?*

This is a good supplement to take if you exercise, particularly if you participate in endurance activities, such as running. It helps with transporting fatty acids into the mitochondria, so L-carnitine may make exercise more productive, particularly among obese people.

*Athletes and fitness advocates may claim benefits for this supplement based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles.

Dosage & Side Effects

L-Carnitine

How Much Is Usually Taken by Athletes?

L-carnitine, which is normally manufactured by the human body, has been popular as a potential ergogenic aid (i.e., having the ability to increase work capacity), because of its role in the conversion of fat to energy.1 However, while some studies have found that L-carnitine improves certain measures of muscle physiology, research on the effects of 2 to 4 grams of carnitine per day on performance have produced inconsistent results.2 L-carnitine may be effective in certain intense exercise activities leading to exhaustion,3 but recent studies have reported that L-carnitine supplementation does not benefit non-exhaustive or even marathon-level endurance exercise,4 , 5 anaerobic performance,6 or lean body mass in weight lifters.7

Side Effects

At the time of writing, there were no well-known side effects caused by this supplement.

Interactions with Supplements, Foods, & Other Compounds

The body needs lysine, methionine, vitamin C, iron, niacin, and vitamin B6 to produce carnitine.

Interactions with Medicines

Certain medicines interact with this supplement.

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • AZT

    Preliminary information suggests that muscle damage sometimes caused by AZT is at least partially due to depletion of carnitine in the muscles by the drug.8 It has been reported that most patients taking AZT have depleted carnitine levels that can be restored with carnitine supplementation (6 grams per day).9

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Carbamazepine

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.10 , 11 , 12 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.13 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.14 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Felbamate

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.16 , 17 , 18 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.19 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.20 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Levetiracetam

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.24 , 25 , 26 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.27 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.28 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Oxcarbazepine

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.29 , 30 , 31 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.32 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.33 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Phenytoin

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.36 , 37 , 38 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.39 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.40 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Primidone

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.41 , 42 , 43 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.44 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.45 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Topiramate

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.47 , 48 , 49 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.50 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.51 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

  • Zonisamide

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.52 , 53 , 54 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.55 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.56 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

Reduce Side Effects

  • Doxorubicin

    Animal research suggests carnitine may prevent doxorubicin’s toxicity.15

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Interferon Alfa-2a
    In a randomized trial, patients with chronic hepatitis C who were being treated with Peg-interferon-alpha 2b and ribavirin were randomly assigned to receive L-carnitine (2 grams twice a day) or no L-carnitine (control group). Compared with the control group, fewer patients in the L-carnitine group had to reduce the medication dosage or discontinue treatment because of side effects such as anemia or a decline in the white blood cell count.21
  • Interferon Alfa-2B
    In a randomized trial, patients with chronic hepatitis C who were being treated with Peg-interferon-alpha 2b and ribavirin were randomly assigned to receive L-carnitine (2 grams twice a day) or no L-carnitine (control group). Compared with the control group, fewer patients in the L-carnitine group had to reduce the medication dosage or discontinue treatment because of side effects such as anemia or a decline in the white blood cell count.22
  • Interferon Alfacon-1
    In a randomized trial, patients with chronic hepatitis C who were being treated with Peg-interferon-alpha 2b and ribavirin were randomly assigned to receive L-carnitine (2 grams twice a day) or no L-carnitine (control group). Compared with the control group, fewer patients in the L-carnitine group had to reduce the medication dosage or discontinue treatment because of side effects such as anemia or a decline in the white blood cell count.23
  • Peginterferon Alfa-2a
    In a randomized trial, patients with chronic hepatitis C who were being treated with Peg-interferon-alpha 2b and ribavirin were randomly assigned to receive L-carnitine (2 grams twice a day) or no L-carnitine (control group). Compared with the control group, fewer patients in the L-carnitine group had to reduce the medication dosage or discontinue treatment because of side effects such as anemia or a decline in the white blood cell count.34
  • Peginterferon Alfa-2b
    In a randomized trial, patients with chronic hepatitis C who were being treated with Peg-interferon-alpha 2b and ribavirin were randomly assigned to receive L-carnitine (2 grams twice a day) or no L-carnitine (control group). Compared with the control group, fewer patients in the L-carnitine group had to reduce the medication dosage or discontinue treatment because of side effects such as anemia or a decline in the white blood cell count.35
  • Ribavirin
    In a randomized trial, patients with chronic hepatitis C who were being treated with Peg-interferon-alpha 2b and ribavirin were randomly assigned to receive L-carnitine (2 grams twice a day) or no L-carnitine (control group). Compared with the control group, fewer patients in the L-carnitine group had to reduce the medication dosage or discontinue treatment because of side effects such as anemia or a decline in the white blood cell count.46

Support Medicine

  • none

Reduces Effectiveness

  • none

Potential Negative Interaction

  • none

Explanation Required

  • Allopurinol

    People who have Duchenne muscular dystrophy have low levels of L-carnitine in their muscles. Allopurinol restores L-carnitine to normal levels, resulting in improved muscle strength.57 Whether L-carnitine supplementation might improve this effect of allopurinol has not been investigated.

  • Gabapentin

    Several controlled and preliminary studies showed that multiple drug therapy for seizures results in dramatic reductions in blood carnitine levels.58 , 59 , 60 Further controlled research is needed to determine whether children taking anticonvulsants might benefit by supplementing with L-carnitine, since current studies yield conflicting results. For example, one controlled study indicated that children taking valproic acid and carbamazepine received no benefit from supplementing with L-carnitine.61 However, another small study revealed that children taking valproic acid experienced less fatigue and excessive sleepiness following L-carnitine supplementation.62 Despite the lack of well-controlled studies, individuals who are taking anticonvulsants and experiencing side effects might benefit from supplementing with L-carnitine.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Phenobarbital

    One controlled study showed that taking phenobarbital resulted in reduced blood levels of L-carnitine.63 Further research is needed to determine whether people taking phenobarbital might benefit from supplemental L-carnitine. Based on the currently available information, some healthcare practitioners may recommend monitoring L-carnitine blood levels or supplementing with L-carnitine.

  • Valproate

    Valproic acid causes depletion of carnitine in children,64 and blood carnitine levels are often low in people taking valproic acid for long periods of time. While there have been several case reports of valproic acid-related carnitine deficiency causing abdominal pain in children, there is controversy about the need for carnitine supplements in children taking valproic acid.65 , 66 , 67

    Complete disappearance of severe valproic acid-induced abdominal pain was achieved in one child with intractable epilepsy immediately following the introduction of 300 mg per day of L-carnitine.68 Carnitine supplementation (50 mg per 2.2 pounds of body weight) has protected children from valproic acid-induced increases in blood ammonia levels in some research,69 though other published work has questioned whether the depletion of carnitine and the increase in blood ammonia levels (both caused by valproic acid) are actually related to each other.70 This last report found that the depletion of carnitine was significantly more severe when epileptics were taking valproic acid together with other anti-seizure medications. A double-blind, crossover study found that carnitine supplementation (100 mg per 2.2 pounds of body weight) was no more effective than placebo in improving the sense of well-being in children treated with valproic acid.71 To date, the question of whether carnitine supplementation is beneficial for people taking valproic acid remains unresolved.72 However, a panel of pediatric neurologists and experts on L-carnitine supplementation strongly recommended oral L-carnitine supplementation for all infants and children taking valproic acid, as well as for adults with carnitine deficiency syndromes, people with valproic acid-induced liver and kidney toxicity, people on kidney dialysis, and premature infants on total parenteral nutrition (intravenous feeding). The panel recommended an amount of 100 mg per 2.2 pounds of body weight per day, up to a maximum of 2 grams per day.73

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

More Resources

L-Carnitine

Where to Find It

Dairy and red meat contain the greatest amounts of carnitine. Therefore, people who have a limited intake of meat and dairy products tend to have lower L-carnitine intakes.

Resources

See a list of books, periodicals, and other resources for this and related topics.

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