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L-carnitine

Synonyms/Common Names/Related Substances:

  • AcCn, acetyl-L-carnitine, B (t) Factor, beta-hydroxy-gamma-N-trimethylamino butyrate, canitor, Carnilean®, carnitene, carnitor, D-carnitine, D,L-carnitine, glycine propionyl-L-carnitine (GPLC), Godex®, Intralipid®, L-3-hydroxytrimethylamminobutanoate, LAC, L-acetyl-carnitine, L-Carnipure®, L-carnitina (Spanish), L-carnitine L-tartrate, LCLT, levacecarnine, levocarnitine, levocarnitine chloride, LK-80, L-propionylcarnitine, MMX™, propionil-L-carnitine, propionyl-L-carnitine, ST200, ST261, VitaCarn®, vitamin B(t), vitamin Bt.
  • Selected combination product: Carnidrop® (Sigma Tau, Pomezia, Italy; L-carnitine 1%, taurine 0.50%, and sodium hyaluronate 0.20g/100mL), Fertimev® (L-arginine, L-carnitine, acetyl-L-carnitine, and ginseng extracts), Optive® (Allergan, Rome, Italy; L-carnitine 0.258%, glycerine 0.9%, an unspecified amount of erythritol, and sodium carboxy methyl cellulose 0.5%), PhenCal (phenylalanine, tryptophan, glutamine, pyridoxal-5'-phosphate, chromium picolinate, carnitine).
  • Note: This monograph focuses on supplemental sources of carnitine (including acetyl-L-carnitine and propionyl-L-carnitine) and not the acyl (fatty acid) derivatives of carnitine made in the body upon metabolism of carnitine. Unless otherwise stipulated, the use of the term carnitine in this monograph implies the levocarnitine (L-carnitine) and not D-carnitine, which may cause secondary deficiency.

Clinical Bottom Line/Effectiveness

Brief Background:

  • The main function of L-carnitine is to transfer long-chain fatty acids in the form of their acyl-carnitine esters across the inner mitochondrial membrane before beta-oxidation. In humans, it is synthesized in the liver, kidney, and brain from lysine and methionine and actively transported to other areas of the body. For example, 98% of the total body L-carnitine is confined to the skeletal and cardiac muscle at concentrations approximately 70 times higher than in the blood serum.
  • Supplementation may be necessary in rare cases of primary carnitine deficiency, which results due to a defect in carnitine biosynthesis, a defect in carnitine active transport into tissue, or a defect in renal conservation of carnitine. L-carnitine was shown to be effective in the following conditions which arise from secondary deficiency of L-carnitine: chronic stable angina and intermittent claudication characterized by distinct tissue hypoxia. Another condition that may benefit from carnitine supplementation is decreased sperm motility.
  • Although use in preterm infants suggests that carnitine supplementation may aid in maintaining or increasing plasma carnitine levels and possibly weight gain, carnitine is not routinely added to preterm total parenteral nutrition (TPN). However, soy-based infant formulas are fortified with carnitine to levels found in breast milk.
  • Carnitine supplementation, as L-carnitine, or acetyl- or propionyl-L-carnitine, has been investigated in many other diseases and conditions. As yet, there is a lack of strong evidence for these uses.
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Dosing/Toxicology

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Precautions/Contraindications

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Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

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Mechanism of Action

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History

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Evidence Table

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Evidence Discussion

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Products Studied

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.