Acetyl-L-Carnitine (ALCAR)
The acetylated ester of L-carnitine, more readily absorbed and able to cross the blood-brain barrier. Marketed as a nootropic and for peripheral neuropathy and fatigue; the strongest human evidence is for diabetic peripheral neuropathy, with mood and cognition benefits more modest.
01 Overview
Acetyl-L-carnitine (ALCAR) delivers both a carnitine moiety and an acetyl group that can feed acetyl-CoA and acetylcholine synthesis. Its greater lipophilicity gives better oral absorption than L-carnitine and CNS penetration, underpinning its nootropic and neuroprotective marketing.
The best-supported clinical use is symptomatic diabetic peripheral neuropathy, where trials show reduced pain and improved nerve function. There is weaker evidence for improvements in fatigue, depressive symptoms (particularly in the elderly) and age-related cognitive decline. As with L-carnitine, chronic high intake raises TMAO.
02 Mechanism
Provides carnitine for mitochondrial fatty-acid transport and an acetyl group supporting acetyl-CoA and acetylcholine synthesis; crosses the blood-brain barrier, giving central metabolic and cholinergic effects.
03 Dosing
| Tier | Dose | Route | Notes |
|---|---|---|---|
| Supplement | 500–2000 mg/day | Oral | Common supplemental range, often split. |
| Neuropathy trials | 2000–3000 mg/day | Oral | Doses used in diabetic neuropathy studies. |
04 Effects
| Effect | Magnitude | Evidence | |
|---|---|---|---|
| Reduced diabetic neuropathy painTrials show reduced neuropathic pain and improved nerve conduction. | moderate | Clinical | |
| Improved mood/fatigue in elderlySome evidence for reduced depressive symptoms and fatigue in older adults. | modest | Observational | |
| Cognitive supportNootropic claims have mixed and generally modest support. | Disputed |
05 Side effects
| Effect | Severity | Frequency | Evidence | Countermeasures |
|---|---|---|---|---|
| Overstimulation / insomniaRestlessness and sleep disturbance, particularly with evening dosing. | Mild | Common | Observational | |
| Gastrointestinal upsetNausea and abdominal discomfort at higher doses. | Mild | Common | Clinical | |
| Raised TMAOShares carnitine's TMAO-raising potential with chronic high intake. | Moderate | Uncertain | Observational |