Thorne Acetyl-L-Carnitine

Most athletes who take carnitine think of it as a fat-burning supplement. That's part of the story — but acetyl-L-carnitine (ALCAR) is doing something standard L-carnitine can't. The acetyl group attached to this form of carnitine allows it to cross the blood-brain barrier efficiently, which means its benefits extend well beyond the mitochondria in your muscles. ALCAR actively supports brain function, peripheral nerve health, acetylcholine production, and the neurological resilience that high-volume endurance training quietly erodes over time.

For athletes who want both the metabolic and the cognitive performance edge, Thorne Acetyl-L-Carnitine delivers both.

Crosses Blood-Brain Barrier – Standard L-carnitine stays largely in the body's periphery and doesn't cross the blood-brain barrier effectively. ALCAR does — and once inside the central nervous system, it supports acetylcholine production, the neurotransmitter responsible for muscle activation, learning, and memory. It also acts as an antioxidant in brain tissue and peripheral nerves, protecting against the oxidative stress that accumulates with heavy training loads and aging.

Mitochondrial Fuel Delivery — Fat Into Energy – In skeletal muscle and throughout the body, acetyl-L-carnitine does what carnitine is best known for: transporting long-chain fatty acids across the mitochondrial membrane so they can be burned for ATP. This supports more efficient fat oxidation during sustained aerobic efforts, helps spare glycogen at submaximal intensities, and supports the cellular energy production that drives both training output and recovery.

Nerve Health and Cortisol Modulation – ALCAR supports the health of peripheral nerves — the network running through your limbs that delivers motor signals and reports sensation back to your brain. Research also suggests ALCAR may partially inhibit the hypothalamic-pituitary-adrenal (HPA) axis, helping moderate chronically elevated cortisol — a relevant benefit for athletes in heavy training blocks where stress hormone dysregulation is common.

Acetyl-L-carnitine is naturally synthesized in the body from L-carnitine, primarily in the brain, liver, and kidneys. Production declines with age and with the demands of chronic high-output training. Thorne's formula delivers a clean 500mg per capsule with no unnecessary additives — the same clinical grade you expect across the entire Thorne line.

How to Use Thorne Acetyl-L-Carnitine

Daily Foundation: Take 1 capsule two to three times daily with food, or as recommended by your healthcare practitioner. Spreading doses through the day supports consistent ALCAR availability for both cognitive function and energy metabolism.

For Cognitive Support: Many athletes take one dose in the morning to prime focus and mental clarity for the training day, and one dose before key sessions where cognitive sharpness matters — race simulations, technical workouts, or long training blocks.