L-Carnitine
Shuttles fatty acids into mitochondria where they're burned for energy. Useful for fat metabolism, exercise recovery, and (the acetyl form) brain energy.
Strong for documented carnitine deficiency (rare). Moderate for: cardiovascular outcomes post-MI, intermittent claudication (propionyl form), erectile function, mild cognitive impairment (ALCAR), exercise recovery, and male fertility (sperm quality). Weaker for fat loss in normal-weight people. Effects: 4–12 weeks.
L-Carnitine is a small molecule made from lysine and methionine that ferries long-chain fatty acids across the mitochondrial membrane so they can be oxidised for energy. Without it, fat can't be efficiently used as fuel. The body makes some and gets the rest from animal foods (the name comes from 'carnis' — flesh). Supplemental forms have distinct uses: standard L-carnitine for fat metabolism and cardiovascular support; acetyl-L-carnitine (ALCAR) crosses the blood-brain barrier and supports cognitive energy; propionyl-L-carnitine targets cardiac and vascular tissue specifically. Vegetarians have measurably lower carnitine and may benefit most.
- Form
- L-Carnitine tartrate — standard, well-absorbed, general use. Acetyl-L-Carnitine (ALCAR) — crosses blood-brain barrier, cognitive and mood support. Propionyl-L-Carnitine — cardiac and peripheral vascular (intermittent claudication, angina). L-Carnitine L-Tartrate — preferred for exercise recovery.
- Dose
- L-Carnitine: 1–3 g/day. ALCAR: 500 mg–2 g/day. Propionyl: 1–2 g/day.
- Timing
- With food (improves absorption significantly — fat-containing meal best). ALCAR can be mildly stimulating — AM. Split high doses across the day.
- Schedule
- Daily.
- Side effects
- Generally well-tolerated. Fishy body odor at high doses (trimethylamine production). Nausea, mild GI upset, vivid dreams.
- Interactions
- Warfarin — may potentiate (monitor INR). Thyroid hormone — high-dose carnitine can blunt thyroid hormone action at receptors (relevant in hyperthyroidism, less so otherwise).
- Contraindications
- Hypothyroidism (relative — may worsen). Active seizure disorder (mixed evidence). Pregnancy / lactation — limited safety data above food intake.
- Lab markers
- Plasma free carnitine and acylcarnitines (research / clinical for documented deficiency). Triglycerides, free fatty acids for metabolic tracking.
- Food sources
- Red meat (especially beef) — by far the richest source, ~80 mg per 4 oz. Pork, fish, chicken, dairy. Plant foods have very little. Vegetarians often run 30–50% lower body stores.
Pairs with
CoQ10, alpha-lipoic acid, PQQ — mitochondrial nutrient stack. Choline (alpha-GPC, citicoline) — ALCAR + choline brain stack. Omega-3 (cardiovascular synergy).
within Amino acids & derivatives