Acetyl-L-carnitine may lift your mood, sharpen your mind, and offset brain aging. It works by improving energy use in the body and boosting acetylcholine. However, most of its benefits lack stronger clinical evidence. Read on to find out if acetyl-L-carnitine is for you and how to use it for optimal results.
What is Acetyl-L-Carnitine?
Amino Acid Fuel
Acetyl-L-carnitine (ALC or ALCAR) is an amino acid that fuels energy production in your cells and supports nerve function. It supplies the acetyl group for burning fats in your mitochondria (fatty acid oxidation) and producing acetylcholine [1, 2].
Your muscles and heart tissue stock different forms of carnitine as energy reserves .
Meat and other animal foods contain L-carnitine, but your liver and kidneys can also produce it from two amino acids: lysine and methionine. An enzyme called carnitine acetyltransferase (CRAT) then turns L-carnitine into acetyl-L-carnitine and vice versa .
Vegetarians consume less carnitine from the foods they eat, however, they maintain normal carnitine levels in the blood. How? The theory is that vegetarians are able to adapt to diets low in carnitine and absorb it more efficiently .
- Combats depression
- Helps with Alzheimer’s disease
- May reverse brain and nerve damage
- Improves fertility and sexual function
- Reduces fatigue
- May cause stomach upset
- May raise the risk of heart disease
- May suppress thyroid hormones
Who Needs It?
Under normal conditions, your body will produce sufficient amounts of carnitine and acetyl-L-carnitine. However, the following may impair the process and raise your risk of carnitine deficiency [5, 6, 7, 3]:
- Genetic disorders
- Old age
- Kidney and liver disorders
- Antibiotics and drugs for seizures
- Diabetes and obesity
- Long-term fasting or calorie restriction
- Premature birth
Do athletes and bodybuilders need more carnitine? Not quite. However, they might benefit from supplementation because higher levels of l-carnitine in the blood and muscles increase blood flow and oxygen supply, enhancing muscle recovery after exercise .
Most people use acetyl-L-carnitine to enhance their cognition and rev up energy levels. Clinical research confirms the benefits of acetyl-l-carnitine for the brain, especially in older people. We’ll cover the main ALCAR benefits below .
Acetyl-L-Carnitine vs. L-Carnitine
Both Acetyl-L-Carnitine (ALCAR) and L-carnitine combat fatigue and enhance fertility, but they also have some distinct benefits (Table 1) .
ALCAR boosts acetylcholine and has more pronounced effects on mental health and cognition. It also shields the brain against oxidative stress better than L-carnitine [10, 11, 12].
On the other hand, L-carnitine is a better-researched option for weight loss, physical performance, and heart health [13, 8, 14, 15].
Table 1: Uses and Benefits of Acetyl-L-Carnitine (ALCAR) vs. L-Carnitine
1) Nerve Damage
Nerves are particularly sensitive to oxidative stress. Certain drugs and conditions such as diabetes can cause nerve damage (neuropathy), which manifests with pain, tingling, or numbness in legs and arms [16, 17].
In two meta-analyses with more than 2,000 neuropathy patients, acetyl-L-carnitine (ALCAR) significantly reduced pain and improved nerve health [18, 19].
Acetyl-L-carnitine seems to be an effective option for diabetic neuropathy. A review of six clinical trials (711 patients) suggested its ability to shield the nerves against toxic glucose levels and reduce pain in people with diabetes. However, the results are less convincing when it comes to nerve conduction speed .
Anti-HIV drugs can also cause nerve damage, antiretroviral toxic neuropathy (ATN), which is a major drawback of HIV treatment. Based on multiple reviews and clinical trials, ALCAR (2-3 g daily) can repair nerve damage and relieve pain and other symptoms in patients with ATN [21, 22, 23, 24].
According to animal trials and limited clinical evidence, acetyl-carnitine may also help with [25, 26, 27]:
- Carpal tunnel syndrome (hand and wrist nerve injury)
- Spinal cord injury
- Chronic pain due to nerve damage and inflammation
On the other hand, it may not help with nerve damage from chemotherapy (more details below) .
A limitation for neuropathy benefits is that many studies used intravenous or intramuscular treatment; oral supplementation might not have the same effects [18, 20, 22].
Acetyl-L-carnitine (ALCAR) supplies the nerves with energy and enables the production of neurotransmitters crucial for mental health; these include acetylcholine, GABA, and glutamate .
It strengthens the myelin around the brain cells and stimulates their growth, helping to “regrow” your brain .
According to a meta-analysis of 11 clinical trials (791 patients), ALCAR is superior to placebo in reducing depressive symptoms. It seems to have effects comparable to standard antidepressants while causing fewer side effects .
Two clinical reviews came to a similar conclusion but also pointed out certain limitations that call for further research. According to one review, ALCAR is especially suitable for older patients and those struggling with side effects from antidepressants [31, 32].
Rapid onset of action is another advantage of ALCAR when it comes to depression. Although patients used it for two months or more, most of them experienced improvement after one week [33, 32].
3) Alzheimer’s Disease
No other neurotransmitter is more important for cognition and memory than acetylcholine; impaired cholinergic transmission is the hallmark of Alzheimer’s disease [34, 35].
By boosting cholinergic activity in the brain, ALCAR may help prevent cognitive decline and Alzheimer’s disease .
It also increases brain levels of glutathione, shielding it against oxidative stress and amyloid beta plaques that destroy neurons in Alzheimer’s disease [37, 10].
A meta-analysis summarized the data from 21 clinical trials with more than 1,200 Alzheimer’s disease patients. Long-term treatment with acetyl-L-carnitine (1.5-3g daily for 3+ months) was safe and significantly improved the patients’ mental condition .
Alzheimer’s patients receiving ALCAR had improved [12, 38, 39]:
- Attention and memory
- Mental agility and focus (reaction time)
- Speech and behavior
Another large review by came to a similar conclusion, though the authors emphasized most improvements were subjective. They also pointed to other statistical limitations and concluded that more research is needed to confirm the clinical effectiveness of ALCAR .
According to a study of 23 patients with drug-resistant Alzheimer’s disease, acetyl-carnitine may boost the effectiveness of standard drugs, such as donepezil (Aricept) and rivastigmine (Exelon) .
4) Fertility and Sexual Function
In a meta-analysis of nine clinical trials with over 800 infertile men, a combination of L-carnitine and acetyl-L-carnitine (ALCAR) significantly improved sperm mobility. As a result, the chance of a successful pregnancy increased more than 4 times .
In 120 older patients, a combination of acetyl-carnitine and propionyl-carnitine (2 g daily each, for 6 months) was as effective as testosterone in improving sexual dysfunction. Carnitines showed even better effects on erectile function and, unlike testosterone, didn’t cause prostate enlargement .
Peyronie’s disease manifests with a curved penis during erection, due to the presence of scar tissue or plaque, which may lead to erectile dysfunction. In a study of 48 patients with this condition, ALCAR showed better results than a drug, tamoxifen. Unlike tamoxifen, ALCAR significantly reduced penile curvature while having fewer side effects .
Women with hypothalamic amenorrhea have irregular cycles and fertility issues due to inadequate GnRH secretion. ALCAR increased sex hormones and improved the symptoms in three studies of 71 women [45, 46, 47].
5) Cognitive Decline and Brain Damage
The brain-protective effects of acetyl-L-carnitine (ALCAR) aren’t limited to Alzheimer’s disease. It may also improve memory and reduce mental fatigue from different causes.
Studies in Older People
Maintaining good brain health is especially important for the aging brain. As cells age, they become senescent: less functional and more pro-inflammatory. As a result, they produce less acetylcholine [48, 49, 50].
Research suggests that ALCAR might offset senescence and thus improve mental health and cognition in the elderly [51, 52].
In two studies with 576 older people, acetyl-L-carnitine enhanced cognition, improved mood and behavior, and reduced fatigue. In 56 older patients, it partially reversed dementia due to reduced blood flow in the brain [53, 54, 55].
Many animal trials suggest that ALC may support learning, memory, and emotional health. Scientists observed its ability to shield the brain and improve cognition by [56, 57, 29, 58, 59, 60]:
- Maximizing energy (ATP) production
- Boosting mitochondrial health
- Increasing acetylcholine
- Scavenging free radicals
- Preventing brain aging caused by lactate buildup in the brain
Based on these effects, acetyl-l-carnitine might also have nootropic effects (improve cognition) regardless of age, though studies haven’t researched this yet [61, 62].
Alpha-Lipoic Acid Synergy
Alpha-lipoic acid is another potent antioxidant that protects the nerves against diabetes and other conditions with increased oxidative stress.
According to animal studies and limited clinical data, acetyl-L-carnitine and alpha-lipoic acid may have a synergistic effect on brain aging and oxidative damage, which makes them a potential combination for cognitive support [63, 64, 65, 66].
Well-designed clinical trials should test the safety and efficacy of this combination.
6) Hepatic Encephalopathy
Acetyl-L-carnitine was effective for brain damage due to liver disease (hepatic encephalopathy) in three clinical trials of over 250 patients. The treatment with ALCAR [67, 68, 69]:
- Reduced depression and improved cognitive function
- Enhanced social function and general wellbeing
- Lowered the levels of ammonia and improved other biomarkers
In 96 older people, supplementation with acetyl-L-carnitine (ALCAR) improved :
It also boosted mood and mental clarity while causing no side effects.
ALCAR (2 g daily) significantly improved mental fatigue and attention in 30 patients with chronic fatigue syndrome .
Patients with chronic fatigue due to multiple sclerosis may also benefit from acetyl-L-carnitine, but the available research doesn’t allow for a definite conclusion [71, 72].
8) Fibromyalgia Symptoms
Fibromyalgia is a complex syndrome that manifests with muscle pain, fatigue, and mood problems. Doctors are still looking for effective treatment options .
Acetyl-L-carnitine significantly reduced pain and depressive symptoms in 102 fibromyalgia patients. Researchers used a combination of oral (1000 mg/day) and intramuscular treatment .
In 65 women with fibromyalgia, ALCAR relieved pain and depression; it was equally effective as an antidepressant duloxetine .
9) Alcohol Addiction
In a study of 64 alcohol abusers, ALCAR (1g/day) provided some short-term benefits such as longer abstinence and reduced cravings. Further research should investigate the potential benefits for alcohol addiction and similar disorders in the long run .
No valid clinical evidence supports the use of acetyl-L-carnitine for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.
Weight Loss and Bodybuilding
Acetyl-L-carnitine (ALC) is a popular supplement for boosting weight loss and physical performance, especially among bodybuilders. Most studies in this field have tested L-carnitine, and they showed mixed results .
A meta-analysis of nine clinical trials and 911 people suggested mild benefits of L-carnitine for weight loss. However, the effect tended to diminish over time, so it might be a good strategy to use it over short cutting cycles .
According to limited clinical evidence and animal trials, supplementation with L-carnitine may enhance physical performance, speed up recovery, and stimulate fat burning [78, 79, 8, 80, 81].
In theory, ALCAR might provide the same benefits by supplying L-carnitine, but no studies have confirmed this.
Also, comprehensive reviews have failed to confirm the above benefits of L-carnitine supplements in healthy people. Their effects may be limited to older or overweight people, kidney disease patients, and other groups with carnitine deficiency [82, 83, 84].
Nerve Damage Due to Chemotherapy
Acetyl-carnitine has shown promising effects against chemotherapy-induced nerve damage in smaller clinical trials [85, 86].
However, it provided no benefits in a study of 409 cancer patients. It even worsened the symptoms of nerve damage after 6 months of treatment .
Diabetes and Heart Health
Impaired fatty acid metabolism and oxidative stress contribute to diabetes. Acetyl-L-carnitine (ALCAR) may help prevent diabetes or reduce the symptoms by enhancing the breakdown of fats and scavenging free radicals [87, 88].
In a small trial of 18 diabetic patients, intravenous ALCAR treatment improved glucose control .
However, a study of 229 diabetics with high blood pressure and lipids found no effects of ALCAR supplementation on glucose metabolism, lipid levels, or blood pressure .
Acetyl-L-Carnitine Side Effects & Precautions
This list does not cover all possible side effects. Contact your doctor or pharmacist if you notice any other side effects. In the US, you may report side effects to the FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada, you may report side effects to Health Canada at 1-866-234-2345.
Acetyl-L-carnitine was safe and well-tolerated in most clinical trials. In rare cases, it caused [30, 12, 54, 18, 91]:
- Upset stomach
Our bodies partly metabolize carnitine into trimethylamine-N-oxide (TMAO), which may promote plaque build-up in blood vessels (atherosclerosis). In a study of over 2,500 people, those with higher blood levels of L-carnitine had increased rates of heart disease .
There are various ways to lower your TMAO levels, such as eating more vegetables, dietary fiber, probiotic– and resveratrol-rich foods [92, 93, 94].
L-carnitine supplementation may cause unpleasant fishy odor and suppress thyroid hormones. ALCAR might do the same, but studies haven’t confirmed this [95, 96, 97].
Safety data about acetyl-L-carnitine during pregnancy is lacking, while the evidence for L-carnitine is limited. If you’re pregnant or trying to conceive, stay on the safe side and avoid ALCAR supplements [98, 99].
Acetyl-L-carnitine appears to be safe for children, but they should use it under strict medical supervision [100, 101].
Acetyl-L-Carnitine Dosage & Supplements
ALCAR supplements have not been approved by the FDA for medical use. In general, regulatory bodies aren’t assuring the quality, safety, and efficacy of supplements. Speak with your doctor before supplementing.
Most products are sold as capsules with 500 mg of acetyl-L-carnitine HCl (hydrochloride). Some also contain alpha-lipoic acid.
You will also find products with different forms of carnitine combined. “Quadracarn” contains four of them, including L-carnitine and ALCAR.
Although meat and animal products are the main dietary source of carnitine, most ALCAR supplements are vegan-friendly.
The below doses used in clinical trials may not apply to you personally. If your doctor suggests using ALCAR, work with them to find the optimal dosage according to your health condition and other factors.
The effective dosage of acetyl-L-carnitine for most conditions ranges from 1500 to 3000 mg, divided into two or three daily doses. Standard treatment duration is 2-3 months, though cognitive impairment and nerve damage may require 6-12 months [30, 12, 53, 54, 18].
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Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice from your doctor or another qualified healthcare provider because of something you have read on SelfHacked.
People use acetyl-L-carnitine (ALCAR) supplements to get rid of brain fog and enhance their focus and memory. Combinations with alpha-lipoic acid are popular as cognitive boosters.
Some users have also reported positive effects on their depression due to increased energy and mental clarity.
A fraction of users experienced no benefits from ALCAR supplements. The most common side effects include nausea, headache, and dizziness. It worsened anxiety in some people.
Acetyl-L-carnitine (ALC or ALCAR) supplies your cells with energy and supports brain health. It increases acetylcholine levels to support cognition and lower oxidative stress in the brain. Older people and kidney disease patients often lack carnitine and might thus benefit from supplementing.
ALCAR may slow down brain aging and help with depression, nerve damage, Alzheimer’s disease, fatigue, and fibromyalgia. It may not be effective for diabetes, heart disease, and chemotherapy-induced nerve damage.
ALCAR is likely safe, but it may cause digestive side effects and headaches in some people. Pregnant women and children should skip it unless prescribed by a doctor. Make sure to consult with your doctor before supplementing.