Acetyl-L-Carnitine

Acetyl-L-Carnitine, also known as ALCAR, is a supplemental form of a non-essential amino acid carnitine. As a supplement, carnitine can be used in many forms, each of which has its unique benefits and effects on the body. Regular L-carnitine is often used for improving cardiovascular health and exercise performance. Acetyl-L-Carnitine shares most of the benefits of regular L-carnitine and can act also as a potent cognitive enhancer. This article is about the main benefits of ALCAR, its potential side effects, the best time to take it, and more.

There are many supplemental forms of carnitine, each of which has its unique effects on the body.

L-Carnitine is the pure form that can be derived from food or synthesized in the lab. Most supplements labeled as L-carnitine do not contain pure L-carnitine but rather L-carnitine tartrate. Pure L-carnitine is mainly used for improving cardiovascular health.

L-Carnitine Tartrate (LCLT) is the most common form labeled as L-carnitine. It is typically used for improving physical performance and power output. The main difference between LCLT and pure L-carnitine is how fast these forms get absorbed. It takes about 3-4 hours for pure carnitine to be absorbed by our body whereas LCLT gets absorbed in 30-40 minutes, making it more suitable for improving exercise performance.

Glycine Propionyl-L-Carnitine (GPLC) is used to alleviate intermittent claudication and blood flow issues. It increases the production of nitric oxide, which improves blood flow. While there are more studies on GPLC supporting these specific effects, this supplement doesn’t seem superior to pure L-carnitine and tends to be more expensive.

Acetyl-L-Carnitine (ALCAR) is used for mood and cognitive enhancement. While the previous forms have similar effects on the body, ALCAR is very different from all of them. This form can easily cross the blood-brain barrier, which aids in improving brain functions. ALCAR can therefore boost energy metabolism in your brain, resulting in an improvement of almost all cognitive processes. Other forms do not have this ability but ALCAR does share many of the benefits of the other forms.

Since carnitine is a non-essential amino acid, you do not need to consume it to survive. However, this amino acid still plays a significant role in human health.

This amino acid plays a crucial role in cellular energy production, boosting antioxidant capacity, protecting cellular membranes from oxidative stress, reducing inflammation, and increasing nitric oxide levels.

On top of this, acetyl-L-carnitine can easily cross the blood-brain barrier and can therefore act as a potent cognitive enhancer.

ALCAR provides an acetyl group that can bind with choline to form acetylcholine, an important neurotransmitter. This is why the supplement is synergistic with choline donors (such as phosphatidylcholine, CDP-choline, and alpha-GPC)

The benefits mentioned below are dose-dependent. Generally, the higher the dose, the more pronounced the effects are. However, they do reach a plateau at a certain point. We will discuss the best dosing protocol later in this article.

Major benefits

Reduced ammonia – A strong reduction in ammonia occurs in people with impaired liver health. The supplements can reduce ammonia levels even in healthy individuals.

Reduced fatigue – A combination of ALCAR and Propionyl-L-Carnitine (2 grams/day each) was able to decrease fatigue while alleviating symptoms of erectile dysfunction in older men. In people with impaired liver health, this benefit is mostly associated with reduced ammonia levels which tend to induce fatigue. An improvement is most notable in people with hepatic encephalopathy and those with high ammonia levels. The supplement can also decrease fatigue in people with celiac disease independent of ammonia levels. As an adjunct therapy for cancer, L-Carnitine may decrease fatigue indirectly through increased lean mass and reduced cancer cachexia.

Minor benefits

Improved cognition – People with hepatic encephalopathy often notice strong cognitive benefits following the supplementation of ALCAR. Other forms of carnitine may impact cognition as well, although to a lesser degree. In healthy people, these supplements can slow down cognitive decline and also improve some aspects of cognitive health.

Improved insulin sensitivity – All forms of carnitine can improve insulin sensitivity in obese people and those with impaired glucose tolerance. ALCAR increases glucose levels in some brain regions.
Reduced muscle damage – The supplement can reliably reduce some biomarkers of muscle damage, such as creatine kinase and muscle soreness.

Reduced symptoms of intermittent claudication – This benefit was mainly observed in people who take Propinyl-L-Carnitine (GPLC). The reduction may also apply to Acetyl-L-Carnitine but more research is needed to prove this.

Reduced heart rate – A small decrease has been found following supplementation.

Antioxidant effects – Carnitine supplements can reduce lipid peroxidation, exercise-induced oxidation, and general oxidation. An increase in all three main antioxidant enzymes (SOD, glutathione peroxidase, and catalase) has been detected.

Increased lean muscle mass – An increase in muscle mass and a reduction in muscle decay is most notable in elderly people. There is not much research on whether or not this applies to young and healthy individuals.

Improved aerobic exercise capacity – This benefit is most notable when people take LCLT but may apply to other forms as well.

Improved attention – The supplement can improve focus and concentration secondary to reducing chronic fatigue.

Increased blood flow – GPLC is the most reliable form for improving blood flow but other supplemental forms of the amino acid may also work.

Reduced blood pressure – This benefit is related to an increase in blood flow.

Improved sperm quality – 3 grams of L-carnitine daily appears to increase sperm quality mostly

related to sperm morphology. Improvements in male fertility have been noted in a small number of studies. This benefit also applies to Acetyl-L-Carnitine but you would need to take about 4 grams to notice it fully.

Fat loss – This effect only applies to people with low carnitine levels.

Treatment of hepatic encephalopathy – All supplemental forms can reduce fatigue and cognitive side effects of hepatic encephalopathy.

Reduced symptoms of autism – Very high doses of L-carnitine (50 mg/kg/d) can notably reduce some of the negative symptoms of autism. This benefit is probably more notable for ALCAR than the other forms of carnitine.

Reduced ADHD in children – In children with ADHD, the amino acid can reduce some of the negative effects, such as aggression. This effect applies mainly to ALCAR.
Reduced symptoms of fibromyalgia, hypothyroidism, and multiple sclerosis – The supplement can reduce some of the symptoms associated with these diseases.

These side effects are dose-dependent. The risk for them increases (often linearly but sometimes exponentially) as you increase the dose. Some of the side effects only apply to very high doses.

Nausea
Diarrhea
Fishy odor – This side effect applies to about 4% of people who take the supplement and is likely due to the formation of trimethylamine.

Narrowing of the carotid arteries – One study has reported a narrowing of the carotid arteries of individuals with metabolic syndrome who took 2 grams of L-carnitine (or about 2.5 grams of ALCAR) for six months.

Toxicity – While acute toxicity is extremely rare, taking high amounts of Acetyl-L-Carnitine could lead to chronic toxicity and cause some health problems. To prevent chronic toxicity, it is best to stay below 4 grams a day unless you have a great reason to take more.

 Contamination – Contaminated supplements are uncommon in the USA and other well-regulated countries. However, if you wish to buy products from China, India, or other countries without strict regulations, beware that the supplements may be contaminated. Either way, you need to choose the brand you order from wisely. It is highly recommended to check the certificates or read through some reviews for the specific product before you buy it. The FDA (Food and Drug Administration) has the power to regulate dietary supplements but can only do so after they have been on the market for a while. That’s because supplement companies are not obligated to announce to the FDA when releasing a new product on the market. The FDA has to discover the product and test it for potential impurities, which can take a lot of time. During that time, the supplement can be sold on the market even if it’s impure. Also, supplement companies can change their manufacturers without announcing it to the FDA.

You should probably avoid taking the supplement if you:

experience a severe adverse reaction after taking the amino acid

You should consider taking the supplement if you:

suffer from hepatic encephalopathy or have impaired liver health

consume very little protein (less than 0.3 grams/pound of body weight)

are on a vegan or vegetarian diet

wish to optimize cognition

suffer from PCOS (polycystic ovary syndrome)

have an impaired glucose tolerance

are diagnosed with autism or ADHD

have fibromyalgia, hypothyroidism, or multiple sclerosis

wish to optimize exercise performance

If you plan to take ALCAR to improve cognition, the ideal daily dose is anywhere from 500-1000 mg.

If you plan to take ALCAR to improve exercise performance and cardiovascular health, 500-2000 mg of L-carnitine appears to be the best daily dose for most people. This amount can be found in about 630-2500 mg of ALCAR.

Some people may benefit from doses higher than 2.5 grams. These include people with liver disease and autism.

The upper safety limit for acetyl-L-carnitine is not well-established. To stay on the safe side, don’t take more than 4 grams daily unless you have a great reason to do so. Higher amounts may cause problems if you take the supplement for a prolonged period.

Like most other amino acids, carnitine is water-soluble, so you don’t have to take it with food to absorb it well. To maximize absorption, take the supplement at least an hour before or after a meal so it doesn’t compete for absorption with other amino acids.

To maximize the benefits, take acetyl-L-carnitine in the morning on empty stomach.

To maximize the absorption, take carnitine at least an hour before or after a meal so it doesn’t compete for absorption with other amino acids.

The half-life of ALCAR in the body is about 4.2 hours. This amino acid should be processed in your body within 12-16 hours after consuming it. Regular L-carnitine gets utilized faster, usually within 3-4 hours after consuming it.

Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.

Other amino acids
Essential and non-essential amino acids should be kept in balance as they act synergistically in many ways. Too much of one amino acid can sometimes cause side effects if there isn’t enough of another amino acid. For example, this principle applies to glycine and methionine, lysine and arginine, and the BCAA trio. There are many other proven and unproven examples. Food or a protein powder is usually a better choice for getting enough amino acids unless you have a specific goal in mind targeted by a particular amino acid/s.

ALA
The combination is effective at increasing mitochondrial density and mRNA levels in mitochondria.

Mildronate
Mildronate may induce a mild carnitine deficiency by reducing L-carnitine levels by about 18% after 4 weeks of using the medication.

Choline
Acetyl-L-Carnitine provides the acetyl group that can be used for the synthesis of acetylcholine. In other words, ALCAR makes it easier to produce acetylcholine when paired with choline donors.

Alcohol
Supplementing with ALCAR can cause protective effects against ethanol-induced neurodegeneration, mainly due to its antioxidant properties.

Riboflavin
about 4% of people taking carnitine may get a mild fishy odor from the supplement. Riboflavin might reduce or eliminate this smell.