Evidence: Very High Possible Benefits: Very High Safety: Very High
TABLE OF CONTENTS
What is carnitine?
Carnitine is a non-essential amino acid. As a supplement, it can be used in many forms, each of which has its unique benefits and effects on the body. Supplements labeled with L-carnitine can be pure L-carnitine, but they mostly come in a form of L-Carnitine Tartrate. Both of these can be used for improving cardiovascular health and exercise performance. Another popular form, Acetyl-L-Carnitine (ALCAR), can act as a potent cognitive enhancer. This article is about the main benefits of supplemental carnitine, its potential side effects, the best time to take it, and more.
Types of carnitine supplements
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.
What does carnitine do for the body?
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.
Possible benefits
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 regular L-carnitine or ALCAR 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.
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.
Possible side effects
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 for six months.
Toxicity – While acute toxicity is extremely rare, taking high amounts of 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.
Who should not take carnitine?
You should probably avoid taking the supplement if you:
experience a severe adverse reaction after taking the amino acid
Who will benefit the most?
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
How much carnitine should you take?
If you plan to take L-carnitine to improve exercise performance and cardiovascular health, 500-2000 mg appears to be the best daily dose for most people. This amount can be found in about 1-4 grams of LCTC or GPLC.
These amounts should provide most of the benefits without meaningful side effects.
Some people may benefit from doses higher than 2 grams. These include people with liver disease and autism.
If you plan to take ALCAR to improve cognition, the ideal daily dose is anywhere from 500-1000 mg.
The upper safety limit for 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.
Best time to take carnitine
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 carnitine before or after a workout.
Whether you take the supplement in the morning or the evening doesn’t matter much. It should not interrupt your sleep in any way.
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 L-carnitine in the body is about 60 minutes. This amino acid should be processed in your body within 3-4 hours after consuming it. L-carnitine taurate gets utilized much faster, usually within 30-40 minutes. On the other hand, the half-life of ALCAR is about 4.2 hours.
Unless it feels too impractical, spread the daily dose into 2+ smaller doses throughout the day.
Interactions
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.
Where to buy carnitine
Amazon is the best option for ordering carnitine supplements in most countries. They offer some very affordable products backed by many positive reviews. Also, you can choose from a wide range of brands without having to search through other markets on the internet.
Beware some brands display the dosage per serving instead of per pill or capsule. Therefore, you may accidentally buy something less potent than you intended. Do not fall for this marketing trick.
FAQ
Most supplements labeled as L-carnitine do not contain pure L-carnitine but rather L-carnitine tartrate (LCLT).
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.
LCLT is typically used for improving physical performance and power output while pure L-carnitine is mainly used for improving cardiovascular health.
You can take the amino acid daily and do not need to cycle it. However, it is certainly not a problem if you don’t take it daily. Not taking the supplement every once in a while could lead to better absorption. That is yet to be proven or disproven.
All of these options are fine. The two most important things to consider are the price and dosing. Powders are almost always the cheapest form. However, you may need a highly accurate scale to dose them correctly (preferably 0.001g). You can get one for as little as $20 from Amazon. Dosing the powders also takes some time that can add up over months or years. The disadvantage of capsules is that they often contain bovine gelatin, which rarely comes from an ethical source.
Yes. Most amino acids, including carnitine, absorb and digest well if you take them before falling asleep. The supplement should not impact sleep quality in any significant way.
This amino acid should not become harmful once it exceeds the expiration date but can lose potency over time.
Keep the supplement in a cold, dark, and dry place, and it should remain just as potent for many months or even years.
While toxicity is rare, too much carnitine in the system can cause some health problems. It is best to stay below 4 grams a day to prevent these side effects.
You may need more of this amino acid if you: – eat very little protein (less than 0.3 grams/pound of body weight) – wish to optimize exercise performance – have fibromyalgia, hypothyroidism, or multiple sclerosis – are diagnosed with autism or ADHD – have an impaired glucose tolerance – are on a vegan or vegetarian diet – suffer from hepatic encephalopathy or have impaired liver health – wish to optimize cognition – suffer from PCOS (polycystic ovary syndrome)
The half-life of L-carnitine in the body is about 60 minutes. This amino acid should be processed in your body within 3-4 hours after consuming it. L-carnitine taurate gets utilized much faster, usually within 30-40 minutes. On the other hand, the half-life of ALCAR is about 4.2 hours.
In the long term, you need to take the supplement for about 2-4 weeks to begin noticing the benefits.
You can easily find vegan-friendly carnitine pills and powders but always check the label to be sure. If you buy the amino acid in a capsulated form, beware that the capsules often contain animal-based gelatin. Instead, find a brand that puts its products into cellulose capsules.
Like most other amino acids, carnitine is water-soluble, so you don’t have to take it with food to absorb it well.
Carnitine should not break a fast unless you take a very high dose at once. If you practice time-restricted eating, you can take this amino acid during your eating window to make sure it doesn’t break your fast. Taking it on empty stomach may be slightly better if you wish to maximize the absorption.
References
Most of the information provided in this guide is supported by scientific research that can be found and verified in the PubMed medical library. We highly encourage you to use the library to verify anything said in this article. We excluded from consideration studies that are either confounded or have a high conflict of interest.
