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Moderate evidenceBrain & cognition

Acetyl-L-Carnitine

Acetyl-L-carnitine has the best evidence for painful diabetic neuropathy and depressive symptoms, where several trials show real benefit; its reputation as a general nootropic for healthy brains rests on much thinner ground.

What the science says

  • Reduces pain in diabetic peripheral neuropathy Moderate evidence

    A 2019 Cochrane review pooling 4 trials in roughly 900 participants found acetyl-L-carnitine reduced neuropathic pain versus placebo, with the larger effect at 2000-3000 mg/day (about a 20-point reduction on a 100 mm visual analogue scale). Cochrane rated the certainty low because of small trial numbers and industry sponsorship.

  • Improves depressive symptoms in trials of modest size Moderate evidence

    A systematic review and meta-analysis of 12 studies found acetyl-L-carnitine significantly reduced depressive symptoms versus placebo, with effects broadly comparable to established antidepressants but markedly fewer adverse events. The trials were mostly small, short (4-12 weeks) and concentrated in older adults, so this is promising rather than settled.

  • Cognitive benefit in mild cognitive impairment and Alzheimer's is small at best Limited evidence

    A meta-analysis of 21 double-blind trials in mild cognitive impairment and mild Alzheimer's disease found a small advantage over placebo on clinical scales at 1500-3000 mg/day over 3-12 months. Subsequent research has not established clinically meaningful benefit, and there is essentially no good evidence it sharpens cognition in healthy young adults.

Dosage & safety

Studied dose1500-3000 mg/day split into 2-3 doses. Neuropathy trials used 2000-3000 mg/day for 6-12 months; depression trials typically 1000-3000 mg/day for 4-12 weeks.
SafetyCommon side effects are nausea, abdominal discomfort, headache and a fishy body odor; some users report restlessness or insomnia if taken late in the day. It can lower seizure threshold in people with epilepsy and may interact with warfarin and thyroid hormone. Because of the antidepressant-like effect, people on psychiatric medication should not add it without medical supervision. In Italy and some other countries acetyl-L-carnitine is registered as a prescription drug rather than a supplement.

Scientific references

Where to buy

NOW Foods, Acetyl-L-Carnitine, 500 mg, 100 Veg Capsules

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