Why is carnitine bad for you

A large body of work, accumulated over decades, indicates that one form of carnitine called acetyl-L-carnitine is safe to use at appropriate doses. Acetyl-L-carnitine has been given clinically at very high doses — as much as 8 grams per day — with no observed side effects.

Furthermore, we know from studies in rodents that it improves mitochondrial function, lowers lipid levels which would lower cardiovascular risk , and improves muscle and brain function. Personally, I will continue to take a daily supplement containing 1, mg of acetyl-L-carnitine. In addition, I exercise regularly, eat a heart-healthy diet, and avoid red meat.

As a resource of trusted nutrition information for the public, we at the Linus Pauling Institute continually reassess our recommendations, based on new scientific information.

We will let you know if we find compelling evidence against carnitine supplementation. In addition to our Research Newsletter and Micronutrient Information Center MIC , we are enhancing our communication efforts, such as with this new blog, to help you make informed personal decisions towards achieving optimum health.

To your health! Oregon State University. Should you be concerned about your carnitine intake? Read on. Early research suggests that supplementation with L-carnitine intravenously may improve insulin sensitivity in diabetics by decreasing fat levels in muscle and may lower glucose levels in the blood by more promptly increasing its oxidation in cells [ ].

The treatment was most effective in subjects with type 2 diabetes of short duration [ 30 ]. HIV-infected individuals often accumulate fat in some areas of the body and lose fat in others and develop high levels of blood fats hyperlipidemia and insulin resistance, which together constitute the lipodystrophy syndrome.

This syndrome may represent mitochondrial toxicity brought about by the HIV infection and the antiretroviral drugs used to treat it, and can induce a carnitine deficiency that limits mitochondrial fat metabolism [ 31 ]. The molecular mechanisms by which this occurs are poorly understood.

End-stage renal disease and hemodialysis Carnitine homeostasis balance within the body among individuals with renal diseases can be substantially impaired by several factors, particularly reduced synthesis and increased elimination of the compound by the kidneys as well as reduced intake from food due to poor appetite and consumption of fewer animal products [ 41 ].

Many patients with end-stage renal disease, particularly those on hemodialysis, become carnitine insufficient. Carnitine blood levels and muscle stores are low, which may contribute to anemia, muscle weakness, fatigue, altered levels of blood fats, and heart disorders.

Numerous studies suggest that high doses of supplemental carnitine often injected in patients on maintenance hemodialysis can correct some or all of these symptoms, though most involve small numbers of patients and are not double-blinded trials. A recent meta-analysis of these studies concludes that carnitine supplements may aid anemia management but not blood-lipid profiles, and that their effects on exercise capacity or heart stability are inconclusive [ 42 ].

Male infertility The carnitine content of seminal fluid is directly related to sperm count and motility [ 43 , 44 ], suggesting that the compound might be of value in treating male infertility. The reported benefits may relate to increased mitochondrial fatty-acid oxidation providing more energy for sperm and reduced cell death in the testes [ 49 ]. Larger and more carefully designed studies are needed to evaluate carnitine's potential value as an infertility therapy.

Rarer side effects include muscle weakness in uremic patients and seizures in those with seizure disorders. Some research indicates that intestinal bacteria metabolize carnitine to form a substance called TMAO that might increase the risk of cardiovascular disease [ 24 ]. This effect appears to be more pronounced in people who consume meat than in vegans or vegetarians.

The implications of these findings are not well understood and require more research. Carnitine interacts with pivalate-conjugated antibiotics such as pivampicillin that are used in the long-term prevention of urinary-tract infections [ 51 ].

Chronic administration of these antibiotics increases the excretion of pivaloyl-carnitine, which can lead to carnitine depletion. However, while tissue carnitine levels may become low enough to limit fatty acid oxidation, no cases of illness due to deficiency have been described [ 1 , 6 ]. Treatment with the anticonvulsants valproic acid, phenobarbital, phenytoin, or carbamazepine has been shown to significantly reduce blood levels of carnitine [ ]. In addition, the use of valproic acid with or without other anticonvulsants may cause hepatotoxicity and increase plasma ammonia concentrations, leading to encephalopathy [ 54 , 55 ].

This toxicity may also occur following acute valproic acid overdose. L-carnitine administration may help treat valproic acid toxicity in children and adults, though the optimal regimen has not been identified [ ]. L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine are available over-the-counter as dietary supplements.

Carnitine is often promoted as an aid for weight loss, to improve exercise performance, and to enhance a sense of well-being [ 2 ]. It is also a drug approved by the Food and Drug Administration to treat primary and certain secondary carnitine-deficiency syndromes. The federal government's — Dietary Guidelines for Americans notes that "Because foods provide an array of nutrients and other components that have benefits for health, nutritional needs should be met primarily through foods.

In some cases, fortified foods and dietary supplements are useful when it is not possible otherwise to meet needs for one or more nutrients e. For more information about building a healthy dietary pattern, refer to the Dietary Guidelines for Americans and the U. Department of Agriculture's MyPlate. This fact sheet by the Office of Dietary Supplements ODS provides information that should not take the place of medical advice.

We encourage you to talk to your healthcare providers doctor, registered dietitian, pharmacist, etc. Any mention in this publication of a specific product or service, or recommendation from an organization or professional society, does not represent an endorsement by ODS of that product, service, or expert advice. Updated: March 29, History of changes to this fact sheet. Find ODS on:. Strengthening Knowledge and Understanding of Dietary Supplements.

Health Information Health Information. Carnitine Fact Sheet for Health Professionals. Carnitine Health Professional Other Resources. Table of Contents Carnitine: What is it? What are recommended intakes for carnitine? What foods provide carnitine? Absorption and metabolism of carnitine When can a carnitine deficiency occur?

What are some current issues and controversies about carnitine? Are there health risks from too much carnitine? Carnitine and medication interactions Supplemental sources of carnitine Carnitine and healthful diets References Disclaimer. References Rebouche CJ. Lippincott Williams and Wilkins, New York, , pp. The editors. Carnitine: lessons from one hundred years of research.

Ann NY Acad Sci ;ix-xi. National Research Council. Food and Nutrition Board. Recommended Dietary Allowances, 10th Edition. Institute of Medicine. Dietary Reference Intakes.

Stanley CA. Carnitine deficiency disorders in children. Ann NY Acad Sci ; Kinetics, pharmacokinetics, and regulation of L-carnitine and acetyl-L-carnitine metabolism. The role of the carnitine system in human metabolism. Comparison of the effects of L-carnitine and acetyl-L-carnitine on carnitine levels, ambulatory activity, and oxidative stress biomarkers in the brain of old rats. The role of carnitine and carnitine supplementation during exercise in man and in individuals with special needs.

J Am Coll Nutr ; Supplemental carnitine and exercise. Carnitine and sports medicine: use or abuse? Delaying the mitochondrial decay of aging with acetylcarnitine.

Feeding acetyl-L-carnitine and lipoic acid to old rats significantly improves metabolic function while decreasing oxidative stress. But does that mean that l-carnitine supplementation puts you at risk? Let's take a closer look at l-carnitine in general, and this recent study and its implications.

First, however, it's important to keep in mind the axiom, 'If a little is good, a lot is not necessarily better. For example:. While this study is certainly intriguing, it's important to keep in mind that the study subjects both humans and mice were given "chronic" amounts of l-carnitine.

Other dosages administered three times daily a total of 0. J Clin Pharmacol. Disposition and metabolite kinetics of oral L-carnitine in humans.

Athletes can safely consume l-carnitine in supplement form to justify replacement. If you are consuming supplemental l-carnitine, we recommend keeping your totals in the range of mg 2g per day. A non-athlete who consumes large amounts of meats that contain l-carnitine does not need to supplement this substance. Animal meat not only generates bodily carnitine, it also generates a protein structure that drives weight gain, growth factors, and plaque formation. If not derived from naturally raised grass-fed animals, there are other harmful substances found in meats that over time may prove harmful to health.

Overall, we recommend not overconsuming substances from the animal kingdom that drive cholesterol accumulation on artery walls. Brass, E. The role of carnitine and carnitine supplementation during exercise in man and in individuals with special needs. J Am Coll Nutr. Dragan, I. Studies concerning the ergogenic value of protein supply and l-carnitine in elite junior cyclists.

Cerretelli, P. L-carnitine supplementation in humans. The effects on physical performance.