L-Carnitine — Supplements
Amino acid derivative essential for mitochondrial fatty acid beta-oxidation and energy metabolism.
Overview
L-carnitine is a conditionally essential amino acid derivative synthesized from lysine and methionine that plays a critical role in mitochondrial fatty acid beta-oxidation by shuttling long-chain fatty acids across the inner mitochondrial membrane via the carnitine palmitoyltransferase (CPT) system. Meta-analyses support modest benefits for exercise performance, recovery (reduced muscle damage markers), and cardiovascular health. Acetyl-L-carnitine (ALCAR) may have additional nootropic benefits via acetylcholine precursor activity.
Indications
- Fatty acid metabolism and energy production
- Exercise performance and recovery
- Cardiovascular health support
- Cognitive function (acetyl-L-carnitine form)
- Male fertility support
Mechanism of Action
L-carnitine shuttles long-chain fatty acyl-CoA across the inner mitochondrial membrane via the CPT-I/CPT-II system
Dosing
| Compound | Dose | Frequency | Notes |
|---|---|---|---|
| L-Carnitine | 1,000 mg | 1-2 times daily | L-carnitine L-tartrate for exercise; ALCAR for cognitive; take with carbohydrate for uptake |
Safety & Contraindications
- GI side effects (nausea, diarrhea, fishy body odor) at higher doses
- TMAO production from gut bacterial metabolism is a theoretical cardiovascular concern
- May cause insomnia if taken late in the day (due to energizing effects)
- Seizure threshold may be lowered in individuals with seizure disorders