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Acetyl-L-Carnitine: Benefits, Side Effects and Summary

Last Updated: Dec 2, 2022

Overview | What it is | Body Composition | Weight loss | Mental benefits | Perception | Side effects | Food sources | Bottom Line

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Acetyl-L-Carnitine (ALCAR) appears to provide the greatest benefit for those who are at risk of mental impairment, overweight or older adults.

If you’re fit, young and healthy the benefits of supplementation are less promising, although likely to be well tolerated.

As you age, ALCAR production levels drop leading to a greater risk of neurological issues.

For older persons supplementing ALCAR can possible confer a host of benefits:

  • body composition in older adults
  • metabolic health
  • cardiovascular health in older adults
  • those suffering from Chronic Fatigue Syndrome
  • Cardiovascular disease markers
  • impaired glucose tolerance
  • insulin resistance
  • arterial hypertension
  • hypoadiponectinemia
  • neuropathy (peripheral)
  • osteoarthiritis
  • Parkinson’s Disease in rat models
  • male infertility
  • Alzheimer’s disease outcomes
  • Chronic obstructive pulmonary disease (COPD)
  • Type 2 Diabetes
  • Sperm motility
  • Increased lean mass in elderly persons
  • Coronary heart disease
  • Headaches & Migraines

What are the types of Carnitine?

Acetyl-L-Carnitine is the acetylated form of L-Carnitine which is used for its role in improving depression, sexual health markers & body composition. It is a non-essential amino acid, meaning your body can produce it naturally. However, levels drop with age.

Carnitine occurs in two forms: L-Carnitine and D-Carnitine

L-Carnitine is the active form found in the body and food.

Acetyl-L-Carnitine (ALCAR) is the most efficient form of L-Carnitine.

Compared to other forms, this form can easily cross the blood-brain barrier.

Most research is focused on ALCAR for this reason.

ALCAR boosts acetylcholine production, a neurotransmitter that affects your mental faculties. Your body needs acetylcholine as it affects learning, memory and motivation. Acetylcholine is the first neurotransmitter to be identified in 1914.

As you age, the production of acetylcholine falls so supplementation can be a way to mitigate this loss.

ALCAR is the acetylated form of L-Carnitine that can exert positive effects on the brain.


1. Can increase energy

Source: Pexels (via Evelyn Chong)

ALCAR has been used by athletes extensively to improve performance, however the evidence is unclear.

In short studies of less than 4 weeks, excess carnitine is excreted through the kidneys to maintain stable levels leading to no benefit in athletic performance.

However in longer studies, there appear to be benefits for muscle damage.

In a study over 24 weeks, healthy male subjects supplementing with 2g L-carnitine-L-Tartrate showed a greater percentage of fat burning at 50% intensity exercise.

The same subjects had a better energy production (80% intensity) and performance relative to control (+11%).

4g of L-Carnitine daily for 14 days in athletes was unable to significantly increase muscle carnitine content or influence blood lactate levels, a key indicator of cardiovascular fitness.

2. May induce weight loss

Acetyl-L-Carnitine has only been found to lead to weight loss in overweight individuals or those suffering from fatigue.

Healthy young individuals taking Acetyl-L-Carnitine may not see any change in fatty acid oxidation.

3. May increase lean mass levels

There is strong evidence to suggest that elderly persons supplementing with ALCAR improve their lean mass levels and decrease fat levels.

In a double blind trial of elderly persons consuming 2g of L-carnitine daily over a period of 30 days, notable improvements on blood lipid parameters (ApoE, ApoA, LDL-C, HDL-C) and body composition were found.


Longterm supplementation of 1.5g – 2g daily may lead to an increased reduction of weight and fat mass

4. Muscle Damage & Recovery

The effects of L-Carnitine supplementation on muscle damage largely focus on L-carnitine L-tartrate, which is widely available for this purpose.

Biomarkers of muscle damage including malondialdehyde (an indicator of oxidative damage), creatine kinase and muscle soreness all returned to baseline minorly faster with supplementation.

In a study of young healthy males aged 18-29 who regularly resistance train – 2g of L-carnitine L-tartrate for 3 weeks daily led to less muscular damage and muscle oxygenation rate.


Muscle damage has been found to be reduced due to L-carnitine supplementation. This may be useful for those wanting to limit muscle soreness and improve recovery.

5. May improve memory

Acetyl-L-Carnitine is promising due its effectiveness in reducing the symptoms of brain diseases such as depression.

Numerous studies of Acetyl-L-Carnitine have shown ALCAR to curb the effects of memory decline as we age.

An improvement of mental function has been observed following Acetyl-L-Carnitine intake in older adults with Alzheimers and mild dementia.

During a 2-month study of 66 centenarians, each received 2g of L-carnitine daily, observed mental and physical fatigue levels decreased. Increases in perceived well-being, energy and mood were observed.

6. May improve depression

One of the most promising aspects of Acetyl-L-Carnitine is its link to depression.

A Stanford University School of Medicine study discovered that people with depression have low levels of ALCAR, and those who had the lowest blood levels of Acetyl-L-Carnitine were also the most depressed.

Acetyl-L-Carnitine provides these benefits due to its effects on modulating inflammatory cytokines.

The neuroprotective effects of ALCAR may be due to its antioxidant properties.

However, L-carnitine’s ability to reduce oxidative stress may not provide benefit to healthy individuals who are not overweight.

People who had the worst cases of a depressive disorder had the lowest level of Acetyl-L-Carnitine in their blood.

Neuroprotective, Neurotrophic and Analgesic

Acetylcholine is a neurotransmitter critical to brain function.

It affects neuroplasticity, reasoning and concentration – all of which decline with age.

ALCAR serves as a precursor to Acetylcholine production – it donates a methyl group to it.

Alzheimer’s patients brains show a reduction in Carnitine acetyltransferase which is an enzyme responsible for cellular metabolism and fat oxidation.

One animal study found that ALCAR can help those who suffer from pain sensitivity.

How Acetyl-L-Carnitine feels

You may perceive a minor difference in focus when taking Acetyl-L-Carnitine unless you are elderly or have sexual Erectile Dysfunction in which case the benefits are stronger.

In persons suffering from physical or mental fatigue, their perception of fatigue levels is lower after Acetyl-L-Carnitine supplementation.

The improvements to fatigue perception may be a result of ALCAR’s effects on pain tolerance.


The benefits of L-Carnitine for the brain are limited to the form ALCAR. As we age, inefficient ALCAR production can lead to dementia and Alzheimers. The evidence is strong that ALCAR has numerous mental benefits.

Who shouldn’t take Acetyl-L-Carnitine?

Those with Inborn errors of metabolism

Chronic supplementation of Acetyl-L-carnitine leads to increased TMAO in patients who have abnormal metabolism or acidemia.

These patients had ~45 fold elevated TMAO compared to the reference population.

L-carnitine intake that circumvents intestinal bacteria in the case of an IV may have potential for those suffering from IEM or acidemia.


General: 630-2,500 milligrams per day is safely tolerated.

Numerous studies demonstrating cognitive improvement in older adults used 1.5-3g /day of acetyl-L-carnitine for 3 months to a year.

For anaerobic work capacity – higher dosages (>3g) are observed to be less effective than lower doses (1.5g). It is unclear why this is the case – further research is required.

In a human study, Acetyl-L-carnitine reduced insulin resistance and hypertension at a dosage of 1 g taken twice daily for 24 weeks.

Treatment was well tolerated and safe in all subjects. Subjects also had improved markers of glucose tolerance and hypoadiponectinemia.


Less than 2g is considered safe long-term and may confer benefits for strength, as a secondary effect of faster recovery time. Similar doses are therapeutic for mental benefit.

Side Effects

The National Institutes of Health (NIH) suggests ALCAR supplementation above 3g/day can cause nausea, vomiting, abdominal cramps and diarrhea. Large doses may cause a body odour that has been described as “fishy” due to altered enzyme metabolism, leading to increased levels of trimethylamines (TMA).

Aside from these side effects, certain individuals should not take L-Carnitine:

  • people taking Sintrom/Acenocoumarol should not take Acetyl-LCarnitine
  • Those taking Warfarin

Food Sources

  • Beef steak, 4 ounces contains 56-162 milligrams (mg)
  • Chicken breast, 4 ounces contains 3-5 milligrams
  • Codfish,  3 ounces contains 3-6 milligrams
  • Tuna, 2 ounces contains 1-3 milligrams
  • Cheese, Cheddar, 1 ounce contains 1 milligram
  • Bread, 1 slice contains 0.1 milligrams

The Bottom Line

ALCAR appears to provide the highest benefits in brain and general health for those who are already unhealthy or older as L-Carnitine levels decrease with age.

The average person who is overweight or has extra body fat will mentally benefit from taking Acetyl-L-Carnitine.

For athletic benefits, long-term use at lower doses (1.5g, 4-6 months) may provide some benefit although studies are equivocal.

L-Carnitine can lower muscle soreness and faster recovery.

Regular doses have been given to people aged over 100 for 2 months and had no side effects aside from improved body composition and general wellbeing. Acetyl-L-Carnitine could benefit sexual health for men and women of all ages.

Overall L-carnitine is one of the most promising nootropics.

As an amino acid, it can be safely taken.


Nootritious only uses information from select peer-reviewed studies, medical associations and research institutions. It is our strict adherence to this policy that allows us to delivers accurate and actionable advice.

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