Acetyl-L-carnitine (ALCAR): what it does and what research shows
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- Acetyl-L-carnitine 500 mg capsules. Best for: Adults whose doctor has approved ALCAR. See options on Amazon
- ALCAR powder. Best for: People who want to measure their own dose. See options on Amazon
- ALCAR with alpha lipoic acid. Best for: Buyers comparing nerve support combinations. See options on Amazon
What acetyl-L-carnitine is
The NIH Office of Dietary Supplements (ODS) says the two main forms of carnitine in supplements are L-carnitine and acetyl-L-carnitine. Carnitine helps turn food into energy, and healthy people make all they need. A 2015 meta-analysis describes ALCAR as a molecule involved in fatty acid metabolism.
A 2020 review in Nutrients lists proposed brain-related actions, including supporting cell membranes and nerve signaling, boosting the activity of the memory chemical acetylcholine, and supporting mitochondrial energy.
What the research shows
| Use | Evidence |
|---|---|
| Painful peripheral neuropathy | About 20% more pain reduction than placebo (4 RCTs) |
| Neuropathic pain, broader | Moderate pain score reduction (4 RCTs, 523 people) |
| Dementia and cognitive decline | Still debated |
| Nerve function | Improved nerve conduction and fiber regrowth in trials |
Nerve pain. A 2019 systematic review in the Journal of Pain Research examined 14 clinical trials and pooled four randomized trials in neuropathy from diabetes or HIV antiretroviral therapy. ALCAR reduced pain by 20.2% from baseline compared with placebo, with good safety. A 2015 meta-analysis in PLOS One of 523 patients also found a moderate pain reduction but called for larger, longer trials.
Memory and dementia. The 2020 Nutrients review says a 2003 systematic review found insufficient evidence for clinical use, although a 2003 meta-analysis showed an advantage on clinical scales. Its role in dementia is still under debate.
Doses used in studies
- Neuropathy. In one year-long trial described in the 2019 review, people received 1,000 mg a day by injection for 10 days, then 2,000 mg a day by mouth for the rest of the study, and pain scores fell more than with placebo after 12 months.
- Alzheimer's disease. Two trials using 3 g a day for a year slowed decline on several cognitive measures, but a later study designed to confirm this did not.
- Memory. Another trial using 1 to 2 g a day for 6 to 12 months found improvements in some memory tests that did not reach statistical significance.
- Chemotherapy nerve damage. Studies have tested ALCAR for protecting nerves during chemotherapy, but the 2019 review found no data on pain reduction, so this is a question for your oncology team.
The 2020 review notes ALCAR was well tolerated for up to a year, with nausea, agitation, insomnia and increased appetite among reported side effects.
ALCAR vs L-carnitine
- Same family. Both are carnitine forms covered by the ODS fact sheet; see our L-carnitine guide for weight loss and exercise research.
- Different focus. ALCAR research centers on nerves and the brain, while L-carnitine research focuses more on energy, exercise and weight.
- Food sources. Red meat is a good source of carnitine; poultry, fish and dairy have some. The body absorbs food carnitine better than supplements.
Safety
- High doses. The ODS says 3 grams or more a day of carnitine can cause nausea, vomiting, stomach cramps, diarrhea and a fishy body odor.
- Seizure disorders. High amounts can raise seizure risk.
- Kidney disease. High amounts can cause muscle weakness in chronic kidney disease.
- Medicines. Anticonvulsants like phenobarbital and valproic acid lower carnitine levels; tell your doctor about all supplements.
- Pregnancy. NOW Foods advises consulting a physician if pregnant or nursing.
- Neuropathy needs a diagnosis. Numbness or burning in the feet can signal diabetes or other conditions that need care.
How to choose an ALCAR supplement
- Amount per serving. NOW Foods' Acetyl-L-Carnitine provides 1 g (from 1,205 mg acetyl-L-carnitine HCl) per 2 capsules, taken 1 to 2 capsules 1 to 2 times daily as needed.
- Stay under 3 g a day of total carnitine to avoid digestive side effects.
- Forms. Capsules, tablets and powders are sold.
- Talk with your doctor before using ALCAR for nerve pain, especially if you have diabetes or take medicines.
What to look for when you buy
Acetyl-L-carnitine 500 mg capsules
Best for: Adults whose doctor has approved ALCAR
NOW Foods provides 1 g ALCAR per 2-capsule serving, from acetyl-L-carnitine HCl.
Watch out: Keep total carnitine under 3 g a day. Caution with seizure or kidney disorders.
See options on AmazonALCAR powder
Best for: People who want to measure their own dose
ALCAR is also sold as a powder.
Watch out: Measure carefully; high doses cause stomach upset and fishy odor.
See options on AmazonALCAR with alpha lipoic acid
Best for: Buyers comparing nerve support combinations
Alpha lipoic acid is another ingredient studied for diabetic neuropathy.
Watch out: Alpha lipoic acid can lower blood sugar. See our alpha lipoic acid guide.
See options on AmazonQuestions people ask
- What is acetyl-L-carnitine used for?
- Mainly nerve pain from peripheral neuropathy and memory support. Nerve pain evidence is moderate; memory evidence is debated.
- Does ALCAR help neuropathy?
- A 2019 meta-analysis of four trials found about 20% more pain reduction than placebo in diabetic and HIV-related neuropathy.
- Is ALCAR better than L-carnitine?
- They are studied for different things. ALCAR research focuses on nerves and brain; L-carnitine on energy and exercise.
- What are acetyl-L-carnitine side effects?
- At 3 grams or more a day of carnitine: nausea, vomiting, cramps, diarrhea and fishy body odor.
- How should I take ALCAR?
- Follow the label. NOW Foods directs 1 to 2 capsules 1 to 2 times daily as needed.
Sources
- Acetyl-L-carnitine in painful peripheral neuropathy: a systematic review (pmc.ncbi.nlm.nih.gov), Journal of Pain Research (PMC6498091)
- Acetyl-L-carnitine in the treatment of peripheral neuropathic pain: a systematic review and meta-analysis (pmc.ncbi.nlm.nih.gov), PLOS One (PMC4353712)
- Acetyl-L-Carnitine in Dementia and Other Cognitive Disorders: A Critical Update (pmc.ncbi.nlm.nih.gov), Nutrients (PMC7284336)
- Carnitine: Fact Sheet for Consumers (ods.od.nih.gov), NIH Office of Dietary Supplements
- Acetyl-L-Carnitine 500 mg Veg Capsules (www.nowfoods.com/products/supplements/acetyl-l-carnitine-500-mg-veg-capsules), NOW Foods