Best L-Carnitine Supplements: Top 10 Brands Reviewed

Even if you are not interested in nutritional and dietary supplements, you have most certainly heard of L-Carnitine supplements. Even nowadays, L-carnitine has remained one of the most popular dietary supplements, purchased with the primary objective of losing weight and getting rid of excess fat.

Acetyl-L-Carnitine and L-Carnitine are both derived from a specific amino acid. They are both frequently supplemented. That said, there are some key differences between the two.

Acetyl-L-Carnitine can pass through the blood-brain barrier. Both forms also offer their own health benefits. The primary purpose of L-carnitine is to boost athletic performance and fat burning.

Acetyl-L-Carnitine is frequently used to improve memory and overall brain health. It's possible to take both supplements at the same time. If you choose to take Acetyl-L-Carnitine, you'll be able to enjoy the perks provided by L-Carnitine, and you'll also get to experience the brain-enhancing benefits.

However, when it is the time to buy it, a question that has probably existed since time immemorial arises, which is the best form of l-carnitine and which form to buy - liquid L-Carnitine, tablets, capsules or maybe powder? But first, let's dive into some scientific facts about L-Carnitine benefits.

So Liquid Form, Tablets, Capsules, or Maybe Powder

Interestingly, while there are several possible answers to almost everyone, there is a default, and it is: "Liquid." However, is this the right answer? The argument behind this choice is that the liquid form gets absorbed better and faster in 99 % of the cases.

I have prepared one of the best liquid, powder, and pills l-carnitine supplements I like, and I use it.

The Top 10 L-Carnitine Supplements Reviewed

L-Carnitine has, in recent times, rising in popularity as an essential nutrient and potent supplement vital for heart health, energy production, and metabolism. L-Carnitine is an amino acid that enables the human body to use the stored energy to enhance endurance in the process of recovery from vigorous exercise.

It converts fat into energy, which ultimately boosts weight loss, increases strength, and decreases fatigue. However, not all these L-Carnitine sources are similar.

The name Carnitine comes from the Latin root “carnus.” It translates to flesh as it is found in meats and dairy products mostly. This article will list nine of the best Carnitine supplements that deliver quality Carnitine in doses that are clinically proven to reap maximum benefits.

1) NOW Foods Triple Strength L-Carnitine Liquid

Product Overview

  • Purest form, clinically tested;
  • Carnipure;
  • GMP quality assured;
  • A dietary supplement;
  • Vegetarian/vegan.

What Is Now Foods Triple Strength L-Carnitine Liquid

This product contains the L-Carnitine (3,000 mg/Spoonful) thrice as in the standard strength product (1,000 mg/spoonful). NOW L-Carnitine Liquid is a popular product as it gives users all of the far-reaching benefits of L-Carnitine but in a much better form.

This liquid form is highly absorbable. L-Carnitine is a non-essential amino acid that is vital to maintaining the body’s general health. It does this by enabling the transfer of fatty acids groups into the mitochondrial membrane for the purpose of the production of cellular energy.

Naturally occurring in red meat and other animal-source foods, this may not be enough for the body. Adults that are omnivorous consume approximately 60-180 mg of Carnitine from their diet, whereas vegans consume only 10-12 mg from a few plant-based sources like asparagus. We recommend supplementation to reach the optimal levels of this amazing amino acid.

Distinguishing features and benefits of using NOW Triple Strength L-Carnitine Liquid:

  • The purest form of L-Carnitine;
  • Vegetarian (non-animal sourced), making it popular among vegans;
  • May enhance cognitive health;
  • Clinically tested, which means it is safe to consume if used correctly or as prescribed.

How to Use This Product

Shake well before using. As a dietary supplement, take 1 tablespoon daily, preferably on an empty stomach.

2) Nutrex Research Labs, Liquid Carnitine 3000

Product Overview

  • Diet support and energy;
  • Maximum strength;
  • No artificial colors or flavors;
  • Liquid carnitine 3000 product highlights;
  • 3000 mg of pure liquid l-carnitine per serving;
  • Helps convert dietary fats to energy;
  • Helps increase endurance;
  • Stimulant free diet support;
  • Liquid L-carnitine supplements for rapid absorption.

What Is Nutrex Research Labs Liquid Carnitine 3000

Nutrex Liquid L-Carnitine helps in the transportation of fatty acids to the mitochondria in the muscles.

Here, they can be used for energy, ultimately resulting in weight loss and increased endurance. Improved endurance is necessary for enhancing athletic performance. The energy produced from this whole process is called adenosine triphosphate or simply ATP.

Distinguishing features of Liquid L-Carnitine 3000:

  • You get 3000mg of pure L-Carnitine per serving;
  • Liquid Carnitine 3000 enhances the quick conversion of dietary fat into energy;
  • Stimulant free diet support.

Benefits of using Liquid Carnitine 3000:

  • Rapid absorption;
  • L-Carnitine helps in the fast energy metabolism of the body;
  • It helps improve endurance;
  • It may improve mood and happiness;
  • It is highly concentrated, and you can easily combine with different diet products.

How to Use This Product

Shake well before opening. Consume one serving daily preferably on an empty stomach. On workout, days consume one serving 30 minutes prior to exercising.

3) Muscle Pharm, Liquid L-Carnitine Core

Product Overview

  • Official nutritional supplement provider of the ultimate fighting championship;
  • Natural flavors;
  • Core series;
  • Balanced carnitine formula with raspberry ketones;
  • Promotes energy for weight loss by utilizing fat;
  • Helps reduce body fat;
  • Helps athletic performance and endurance;
  • Helps convert fat to energy;
  • Made in a cGMP certified facility.

What Is Muscle Pharm Liquid L-Carnitine Core

Muscle Pharm, Liquid L-Carnitine Core is the Official Supplement Provider of the Ultimate Fighting Championship (UFC). It assists in the transportation of long-chain fatty acids towards the power plant or mitochondrial cells.

Your body generates Carnitine in the liver and kidneys and then stores in the brain, heart, skeletal muscles, and sperm. L-Carnitine makes the process more efficient, and it increases an athlete’s ability to metabolize fat into powerful energy rapidly.

Distinguishing features of Muscle Pharm Liquid Carnitine Core:

  • It contains natural flavors meaning they are safe for consumption.
  • A well-balanced Carnitine Formula with Raspberry Ketones. They act as a natural energy booster for an athlete on a low-calorie diet or anyone else for that matter.

Benefits of using Muscle Pharm Liquid Carnitine Core:

  • Aids in reducing body fat.
  • Carnitine Core aids in the rapid conversion of fat to energy.
  • Carnitine Core aids in nutrients absorption.
  • Stimulates energy for the purpose of weight loss by utilizing fat.
  • Famous for athletic performance and endurance.

How to Use This Product

As a dietary supplement consume 1 serving (16 mL) of MusclePharm Carnitine Core one to three times daily. Shake well before each use. May also be mixed with your favorite juice or beverage. Refrigerate after opening.

4) Solgar L-Carnitine Natural Lemon Flavor

Product Overview

  • Free form;
  • Supports energy & fat metabolism;
  • Promotes exercise recovery;
  • Gluten, wheat & dairy free;
  • Suitable for vegetarians;
  • Dietary supplement.

What Is Solgar L-Carnitine Liquid

Solgar Liquid L-Carnitine is dipeptide by nature. It means that it is a combination of two amino acids. The two amino acids are lysine and methionine. Being a peptide offers extra support for endurance exercise and the recovery from high-intensity exercise.

It is present in the mitochondria, popularly referred to as the powerhouse of cells. Here, it facilitates the metabolism of fats and the production of energy. Losing weight can prove to be a big challenge, especially for beginners.

One interesting feature of L-Carnitine is that it is heart-healthy. Being heart-healthy means that it is non-harmful for the heart as the heart relies on it for energy production from fat.

Distinguishing features of Solgar Liquid L-Carnitine:

  • This formulation delivers Free Form L-Carnitine necessary for optimal assimilation and absorption.
  • It has Pantothenic acid that is part of the essential coenzyme tasked with the responsibility of the release of energy from cells.

Benefits of using Solgar Liquid L-Carnitine:

  • Offers all the essential nutrients in a ready to use liquid delivery form.
  • Increased insulin sensitivity.
  • Improved cardiovascular health.
  • It has a great taste making it easy to take.
  • It has a nitrogen blanket to minimize oxidation and preserve nutrient potency.

How to Use This Product

Shake well before use. As a dietary supplement for adults, take one (1) tablespoon (15 ml) twice daily, preferably on an empty stomach.

5) ALLMAX Nutrition L-Carnitine Liquid + Vitamin B5

Product Overview

  • No glycerin;
  • Improves exercise capacity via fatigue reduction;
  • Assists in faster recovery after heavy exercise;
  • Helps increase total muscle mass;
  • Carb free - sugar free - calorie free;
  • 100% quality & potency guaranteed;
  • Lab tested - every ngredient - every lot;
  • CGMP certified facility;
  • 100% natural color;
  • Vegetarian;
  • Gluten free.

What Is ALLMAX Nutrition L-Carnitine Liquid + Vitamin B5

Allmax Liquid L-Carnitine provides a convenient approach to intake these amino acids in liquid form. As mentioned, L-Carnitine is essential in the transportation of long-tail fats into the mitochondria cells.

It taps cuts fat and does even more by burning the fat as fuel. The result is increased energy, which emphasizes the importance of L-Carnitine.

Without it, these fats cannot turn into energy. L-Carnitine works closely with Vitamin B5, which is a key coenzyme A (coA). It is a vital part of L-Carnitine supplementation.

Distinguishing features of Liquid L-Carnitine by Allmax:

  • 1200 mg per serving.
  • Stimulant free metabolizer.
  • High-quality pure value Liquid L-Carnitine.

Benefits of using Liquid L-Carnitine by Allmax:

  • It has a delicious taste making it easy to ingest.
  • It boosts energy, performance, and endurance of the user - L-Carnitine augments performance by improving how the human body depends on fat or energy. Increased energy decreases the exhaustion of glycogen. Reduced lactic acid build-up enables performance athletes to have the ability to extend the duration of muscular exertion before fatigue.
  • Rapid delivery and absorption Liquid L-Carnitine.

How to Use This Product

Shake well before each use. Take one tablespoon (15 ml) of Liquid L-Carnitine preferably on an empty stomach. On workout days, consume 30 to 60 minutes prior to training. On non-workout days, consume anytime throughout the day.

6) ALCAR Acetyl-L-Carnitine Powder

Product Overview

  • Tested for purity and potency;
  • Burn fat;
  • Improve performance;
  • Maximize focus;
  • Dietary supplement;
  • Product produced in a GMP certified facility.

What Is Acetyl-L-Carnitine Powder

Acetyl L-Carnitine plays a significant role in energy metabolism. It specifically aids in transportation and converting or burning them for energy.

Primaforce Acetyl L-Carnitine Powder is suitable for strict dieters, vegans, and people suffering from eating disorders.

Distinguishing features of Alcar Acetyl-L-Carnitine Powder:

  • It helps in mental focus.
  • Vital for fat/weight loss as it supports better performance while dieting.

Benefits of using ALCAR Acetyl-L-Carnitine Powder:

  • Improves the performance of athletes.
  • Aids in heightening mental acuity.
  • Acetyl supports recovery after strenuous training by the user.
  • Acetyl enhances the process of burning fat.
  • A neuro-supporting agent.

How to Use This Product

As a dietary supplement take one scoop 1-3 times per day.

7) Doctor's Best Best L-Carnitine Powder Fumarate

Product Overview

  • Science-based nutrition;
  • Biosint carnitines;
  • Helps burn body fat;
  • Vegan;
  • Helps the body burn fat for energy;
  • Helps maintain normal cardiovascular health;
  • Non-GMO;
  • Gluten free.

What Is Doctor's Best L-Carnitine Fumarate

Doctor's Best L-Carnitine Fumarate Tablets comes from a base of Pharmaceutical grade L-Carnitine. Its creation is a patented process that is FDA approved.

L-Carnitine is a nutrient that stimulates energy production in cells. The mitochondrion is an intracellular structure responsible for the generation of metabolic energy in the form of ATP.

Distinguishing features of Doctor's Best Best L-Carnitine Powder Fumarate:

  • Fumarate is a naturally occurring compound in the body that acts as an intermediate in the Krebs cycle. The Krebs cycle is a significant energy-producing process that happens in the mitochondrion

Benefits of using Doctor's Best Best L-Carnitine Powder Fumarate:

  • Pesticide free, BSE free, and GMO-free.
  • L-Carnitine helps the body to metabolize fats resourcefully.
  • FDA approved

How to Use This Product

Take 1 - 3 capsule daily, with or without food.

8) ALLMAX Nutrition L-Carnitine Capsules Tartrate

Product Overview

  • L-Carnitine Supplements support transport of fats to muscle tissue;
  • Helps increase in lean muscle mass;
  • Supports overall body fat reduction;
  • Vegan caps - 100% vegetarian;
  • 100% quality & potency guaranteed;
  • CGMP certified;
  • Gluten free.

What Is ALLMAX L-Carnitine L-Tartrate

This L-Carnitine-L-Tartrate is a product of Allmax. By now, you already know what L-Carnitine's primary objective is.

The result is increased energy. The lack of L-Carnitine, therefore, means the fats cannot be turned into energy and instead are shunted to store body fat, which is not what we want.

Besides, it enhances performance by improving how the body relies on fat for energy. People using this product can prolong workout duration before fatigue.

Distinguishing features of ALLMAX Nutrition L-Carnitine Capsules Tartrate:

  • Arguably the most popular bio-available form of L-Carnitine supplementation.
  • Stimulant free metabolizer.
  • It helps to ease the aging process.

Benefits of using ALLMAX Nutrition L-Carnitine Capsules Tartrate:

  • Contributes to boost endurance and performance.
  • Easy consumption and gets into the bloodstream faster.
  • Relatively cheaper

How to Use This Product

As a dietary supplement, take 1 to 3 servings daily, preferably on an empty stomach. On workout days, consume 30 to 60 minutes prior to training. On non-workout days, consume anytime throughout the day.

9) Dymatize Nutrition L-Carnitine Xtreme

Product Overview

  • L-Carnitine supplements act as fat burner;
  • Boost endurance & performance;
  • Convenience, quality & value;
  • Dietary supplement.

What Is Dymatize Nutrition L-Carnitine Xtreme

L-Carnitine is known to be an amino acid that promotes growth and development, increasing energy, burning fat, and refining resistance to muscle fatigue.

An athletic can, therefore, experience extended training sessions before they are exhausted. Apart from that, Dymatize L-Carnitine Xreme capsules also reduce feelings of weakness and hunger making it great in dieting.

Distinguishing features of Dymatize Nutrition, L-Carnitine Xtreme:

  • Available in a generous 60 serving bottle.
  • Excellent quality and value for your money.

Benefits of using Dymatize Nutrition, L-Carnitine Xtreme:

  • Burning fat – L-Carnitine plays a crucial metabolic role in stimulating body weight loss. It does this by transporting fats to the mitochondria where burned for energy takes place.
  • Advancing endurance and athletic performance.
  • Available in sweet flavor.

Regardless of the intended use of L-Carnitine, the above products can be trusted in satisfying your needs. Whether you are using it for the health of your heart, fat loss, or increased endurance during workouts, L-Carnitine delivers what other supplements cannot.

How to Use This Product

As an adult dietary supplement take 1 capsule daily preferably with a meal. You can take two servings daily if desired.

10) MRM Acetyl L-Carnitine

Product Overview

  • 500 mg per capsule;
  • Certified vegan;
  • Supports alertness and mental focus;
  • GMP - produced in a certified facility - good manufacturing practices.

What Is MRM Acetyl L-Carnitine

The MRM Acetyl L-Carnitine supplement is incredibly bioavailable and capable of traveling across the blood-brain line of demarcation.

After reaching the brain, it serves as an antioxidant and neuroprotective substance while also boosting the metabolism of energy sources. Focus and alertness are markedly improved by the addition of Vitamin B6 to the mix.

Benefits of Using MRM Acetyl L-Carnitine

  • Improved memory function.
  • Antioxidant activity.
  • Support for overall cognitive activity.
  • Burning fat – L-Carnitine plays a crucial metabolic role in stimulating body weight loss. It does this by transporting fats to the mitochondria where burned for energy takes place.
  • Advancing endurance and athletic performance.

How to Use This Product

Take 1 capsule up to 3 times a day or as directed by your qualified healthcare provider.

L-Carnitine: the Benefits It Has to Offer:

L-carnitine offers many benefits. Some of these benefits we have already discussed above. With that said, some of the key benefits include:

Best L-Carnitine Supplements and L-carnitine Health Benefits

1) Lose Weight

  • L-carnitine can help you get lean. The amino acid has been shown to suppress the appetite and to reduce fatigue, which is why you should be taking it when you are dieting. It will help prevent your body from storing fat, and it will help you burn off more calories. If your goal is to get lean and burn fat, then take L-carnitine.

2) Gain Muscle

  • The amino acid can help you pack on muscle. In fact, this is why many hard gainers choose to use it when they want to gain muscle. If you use the amino acid, then it can help you gain straight, and the more weight you can lift, the more muscle you will pack on. 

3) Improve Bone Mass

  • As people age, they tend to be at risk of bone loss. This can lead to an in the case of fractures and arthritis. You can improve your bone mass by taking l-carnitine.

4) Improve Cardiovascular Health

  • Carnitine is often used to treat heart-related conditions, and some clinical trials show the amino acid can be used alongside traditional treatment for angina. It works to reduce the need for medicine. There are a few studies that have shown that those who take the amino acid after suffering a heart attack reduce their chances of suffering another heart attack in the future. The amino acid has been given to people with heart disease, and it was given to them to help treat them.

5) Kidney Treatment

  • Carnitine is produced in the kidney. It is recommended to those who kidney don't produce enough carnitine. In other words, the amino acid is used for kidney treatment.

6) Infertility Treatment

  • Many men have issues with infertility. This can be due to having low sperm counts. Carnitine can help improve sperm count in men, and it can improve the quality of sperm.

7) Helps Women Who Breastfeed

  • New mothers choose to breastfeed in part because it burns calories, but breastfeeding can lower carnitine in the body. This is why it's a good idea to take carnitine while you are breastfeeding. Doing this can prevent you from becoming deficient in carnitine. New mothers may find it easier to lose weight while taking carnitine.

8) Diabetes Type II

  • Type II diabetes affects many. Those who suffer from it can benefit from using a carnitine supplement. It increases glucose oxidation, and it helps with glucose uptake.

9) Good For The Immune System

  • The amino acid acts as an antioxidant. It can protect your body's cells. This can help when you are dealing with various allergies or if you have a cold.

10) Good For Brain Function

  • Seniors often deal with brain issues, which is due to natural aging. L-carnitine protects the brain from damage. In short, the amino acid can help your brain function better and function for longer.

11) Valproic Acid Poisoning

  • Bodybuilders may not deal with valproic acid poisoning. However, there have been many cases of valproic acid ingested yearly. The amino acid has been known to help those who suffer from valproic acid poisoning.

So Which Is the Better Option

The truth is that there is no better or best option for everyone. There is a “the most convenient” or “the cheapest for you” option. Practically, the final effect will be the same. The absorption is the same.

I don’t want to make this argument sound like fudge, and that is why I will give you some real scientific data, which we found about a study, conducted precisely for this purpose.

How to Stack L-Carnitine

Stacking it is easy, but the most important thing to stack it with is carbs. The supplement needs to be taken at a time when insulin would spike and when muscle uptake is adequate. This is why stacking it with carbs makes sense.

Some research shows that insulin levels should be high in order for carnitine to enter the muscle cells. The good news is that when you take the amino acid, then insulin's actions are enhanced.

The end result is more glucose being delivered into the cells, and more l-carnitine will be delivered to the cells, too. You can get away with consuming as little as one gram of carnitine, but you should take 2-3 doses and try to take at least 30-40 grams of carbs and 20-35 grams of protein.

You don't have to, but consider taking it with a meal if you want to get the best results. If you take l-carnitine with the right ingredients, then its fat-burning properties can be enhanced, so take l-carnitine with green tea, caffeine or take it between meals.

When Should I Take L-Carnitine

By now, you may be wondering when you should take it, and you should take it after working out. Feel free to take it with a high-protein meal at any point of the day. If you stack it with fat-burning ingredients, then consider taking the acetyl-L-carnitine form.

A good strategy is to take 2-3 doses of carnitine with another fat burning ingredient. Take one dose with a post-workout meal and take the other doses without food between meals.

If you follow this strategy, then you could end up getting the best results with carnitine, so make sure you give it a try and see how it works for you. L-carnitine is a great supplement, and your body can benefit from using it, so start taking it today and start reaping the benefits.

A Study on L-Carnitine Forms Showed That

The study has compared the bioavailability with a single dose of the three oral forms of L-carnitine - liquid, tablet, and chewable tablet.

As a conclusion, the study has stated that the three forms are bioequivalent, which on a pharmacokinetics language means that the substances are the same and do the same job. [1]

The choice of the form should be taken into account, especially in terms of compactness and convenience of administration.

Foods That Contain L-Carnitine

One of the top sources of L-Carnitine is animal products. Beef packs in a very high amount per serving, especially if the beef comes from grass-fed cows.

You can also find small amounts of L-Carnitine in grains and vegetables. The National Institute of Health reports that these foods contain the highest amount of L-Carnitine per serving:

  • 4 ounces of cooked beef steak: 56 to 162 milligrams;
  • 4 ounces of cooked ground beef: 87 to 99 milligrams;
  • 1 cup of whole milk: 8 milligrams;
  • 4 ounces of cooked codfish: 4 to 7 milligrams;
  • 4 ounces cooked chicken breast: 3 to 5 milligrams;
  • 1/2 cup ice cream: 3 milligrams;
  • 2 ounces cheddar cheese: 2 milligrams;
  • 2 slices of whole wheat bread: 0.2 milligrams;
  • 1/2 cupped cooked asparagus: 0.1 milligrams.

Who Should Take L-Carnitine

L-Carnitine is the safest supplement to burn fat and lose weight. That said, there are other advantages to adding L-Carnitine to your diet:

  • It can improve your brain function, protect your muscles, build your endurance, enhance your athletic abilities, and correct other deficiencies.
  • Taking an L-Carnitine supplement is a very smart idea for people that follow a vegan or vegetarian diet. People that avoid animal products may not be consuming many foods that are rich in carnitine.

L-Carnitine FAQs

1) What Is L-Carnitine Used For

L-carnitine is an essential amino acid compound, where l-carnitine is used for breaking down fats into energy. L-carnitine delivers part of the fatty acids to the mitochondria, which is responsible for producing all the energy the body uses.

Studies prove that to use fatty acids as energy, your body needs l-carnitine.

2) How Much L-Carnitine Should I Take for Weight Loss?

The most appropriate dosage of l carnitine for weight loss is between 1 – 3 grams of l-carnitine.

Usually, the athletes take it in a separate dosage, one dosage of l-carnitine before a workout, and one dosage of l-carnitine in the evening or before bedtime.

3) How Does Carnitine Work in the Body?

In the body, l-carnitine works by escorting long-chain fatty acids to the cells' mitochondria, where they produce energy. The l-carnitine can be synthesized in the body from the two essential amino acids lysine and methionine.

L-carnitine is an essential amino acid compound used for the breakdown of the fats into energy.

4) What Is L-Tartrate Used For?

L-tartrate (l-carnitine-l-tartrate/LCLT) is a form of L-carnitine that is used in a lot of studies in athletes, and it is thought to have a more rapid influx into plasma following oral ingestion (which makes it useful for timing-critical situations, like pre-workout dosing).

5) What Are the Side Effects of L-Carnitine?

The side effects of l-carnitine are very rare.

A few studies have noted a benign adverse effect of "odd smell," which is said to be due to the formation of trimethylamines; it has occurred at a frequency of 4%. Some authors have stated (unpublished data) that this smell is attenuated with riboflavin supplementation.

6) Is L-Carnitine Effective for Weight Loss?

L-carnitine is effective for weight loss, mostly when the person using the l-carnitine amino acid suffers from an l-carnitine deficiency. Meat being the major food source of l-carnitine, vegetarians, and vegans are prone to l-carnitine deficiency.

7) How Much L-Carnitine Is Safe to Take?

L-carnitine is a very safe and well-researched supplement. Studies have shown that taking up to 3-4 grams per day l-carnitine is safe, showing no side effects at all.

L-Carnitine is a naturally occurring amino acid found in animal tissue (meat products) and milk to a degree, it is also a constituent of human breast milk.

L-Carnitine has many mechanisms by which it can theoretically increase the rate of fat loss, yet it doesn't seem to actually induce or augment fat loss when supplemented. The exception to this is in a deficiency state, in which L-carnitine supplementation will restore hindered fat-burning potential.

Insulin sensitivity can be increased with Carnitine supplementation in obese persons and those with impaired glucose tolerance, such as pre-diabetes and those with metabolic syndrome.

Improvements in sensitivity have been noted as quickly as 10 days with 2 g of Carnitine supplementation, although this particular study required a hypocaloric diet in conjunction with Carnitine supplementation.

Structure and Sources:

L-Carnitine (L-3-hydroxytrimethylamminobutanoate) is a naturally occurring amino acid found in animal tissue (meat products) and milk to a degree, it is also a constituent of human breast milk.

It can be synthesized in the body through the two essential amino acids lysine and methionine. Due to these sources, it is known as one nutrient that affects vegetarians and omnivores differently.

Carnitine exists in the body in two forms, either L-carnitine or the acetylated form known as Acetyl-L-Carnitine (ALCAR).

The synthesis of these molecules can occur endogenously from the two dietary amino acids L-methionine and lysine.

  • L-Carnitine can be synthesized in the human body from two dietary essential amino acids, L-methionine, and lysine. This process involves a few Vitamin C-dependent enzymes, and deficiencies of Vitamin C can impair L-carnitine biosynthesis.
  • Synthesis of L-carnitine is lower in newborns, although this is covered by both breast milk (provides dietary L-carnitine) and formulations which tend to add L-carnitine to avoid complications of low synthesis.
  • It would be prudent for vegetarians to supplement L-carnitine, but there is a lack of human interventions on the subject matter.
  • Older people suffering from fatigue or other non-clinical complications would benefit from L-carnitine supplementation.
  • Acetyl-L-carnitine is another form of L-carnitine that is catered toward neurological effects, and it seems to have some unique properties associated with it that basic L-carnitine does not.
  • Glycine propionyl-L-carnitine (GPLC) or propionyl-L-carnitine (PLC) are seen as variants of L-carnitine that can benefit blood flow and pressure to a larger degree than the other forms of L-carnitine.
  • L-Carnitine L-Tartrate (LCLT) is a form of L-carnitine that is used in a lot of studies in athletes, and it is thought to have a more rapid influx into plasma following oral ingestion (which makes it useful for timing-critical situations, like pre-workout dosing).
  • L-carnitine is used more by people that are trying to lose weight or by bodybuilders, as it helps convert fatty acids found in the body into a natural energy source.

Absorption, Metabolism, and Elimination By the Body:

L-Carnitine is absorbed in the gut via the OCTN2 transporter, and alterations in this transporter determine alterations in L-carnitine absorption. If it is increased, then more is absorbed, if it is impaired or blocked, then less L-carnitine is absorbed.

When examining variations in the absorption of L-carnitine, it seems that L-carnitine found in food products is absorbed to a better degree than L-carnitine from supplements (regardless of the form used), but supplements are still absorbed to a fairly decent degree.

  • L-Carnitine appears to be absorbed through the skin when applied topically
  • At a cellular level, insulin appears to increase the rate of uptake of L-carnitine into tissue
  • At a cellular level, insulin appears to increase the rate of uptake of L-carnitine into tissue
  • L-Carnitine is excreted via the kidneys
  • Carnitine can also be excreted fecally

Obesity and Fat Burning Mechanism:

On a cellular level, the presence of Carnitine in the form of supplementation does induce enzymatic changes that do make the potency of the beta-oxidation pathway increase when paired with exercise.

During exercise, L-Carnitine (as L-Tartrate) supplementation may influence substrate utilization slightly but does not appear to influence overall fat and glucose oxidation rates. 

Glycogen depletion rates are also not affected. After exercise, a slight trend towards fat oxidation (as assessed by respiratory quotient) has been noted.

L-Carnitine has many mechanisms by which it can theoretically increase the rate of fat loss, yet it doesn't seem to actually induce or augment fat loss when supplemented.

The exception to this is in a deficiency state, in which L-carnitine supplementation will restore hindered fat-burning potential.

Insulin Sensitivity and Glucose Uptake:

Insulin sensitivity can be increased with Carnitine supplementation in obese persons and those with impaired glucose tolerance, such as pre-diabetes and those with metabolic syndrome.

Improvements in sensitivity have been noted as quickly as 10 days with 2 g of Carnitine supplementation, although this particular study required a hypocaloric diet in conjunction with Carnitine supplementation.

The mechanisms by which it increases muscular uptake of glucose is via stimulation of AMPK-mediated glucose uptake.

Mechanisms of increasing insulin sensitivity include shuttling acyl and acetyl groups out of a cell and into plasma, to be excreted in the urine; a process known as fatty acid dumping. 

L-Carnitine could also simply shuttle these acyl groups into the mitochondrial to be burnt during beta-oxidation (fat burning). Build-up, of these groups in a cell, may lead to skeletal muscle insulin resistance, and thus carnitine transport would act as a therapeutic measure.

Power Output, Fatigue, Injury, and Recovery:

In general, studies suggest that L-Carnitine supplementation in all its forms does not increase acute power output when ingested once before exercise or as a daily supplement. 

One study noted slight increases in sprint power and increased work capacity, possibly secondary to reduced lactate build-up following 4.5 g GPLC once before exercise. 

Another study noted that over a supplementation period of 28 days noted this increased power during sprints occurred at 1.5 g GPLC, whereas 3-4.5 g was suppressive of power output.

In comparing 1g and 2 g L-Carnitine (and L-Tartrate), both doses are effective in reducing markers of muscular damage despite the higher dosage causing greater serum increases of Carnitine.

One study that looked as to whether these reductions in muscle damage affected acute recovery times noted no differences between placebo and 2 g L-Carnitine when two anaerobic cardio sessions were separated by 3 hours.

Aerobic and Anaerobic Exercises:

Studies show mixed results. It doesn't seem to reliably offer aerobic exercise benefits after common dosages and might increase sprint performance (both max speed and volume done). 

It seems a bit more reliable in increasing work volume at 1.5-2g daily, but further study is needed.

Interactions with Growth Hormone:

L-Carnitine L-Tartrate, at 2 g daily over 3 weeks, was able to increase levels of IGF Binding Protein-3 that are induced by exercise for about 180 minutes. 

This theoretically may increase the effects of IGF-1 and IGF-2 by giving them more time in the blood.

Hair Benefits:

Carnitine, as L-Carnitine L-tartrate, has been shown in vitro to enhance hair follicle growth by simultaneously enhancing growth and attenuating apoptosis (cell death). 

It seemed to be effective at a concentration of 0.5uM and 5uM.

Side Effects:

A safety study on L-Carnitine L-Tartrate investigating 3 g daily for 3 weeks in 21 healthy men noted no aberrations to enzyme or blood parameters and suggested its safety as an oral supplement.

At least in carnitine deficiency states (which may not be fully applicable to healthy humans) the recommended dosage of Levocarnitine (L-Carnitine) is 100-400mg per kilogram bodyweight.

A few studies have noted a benign adverse effect of 'odd smell', which is said to be due to the formation of trimethylamines; it has occurred at a frequency of 4%. Some authors have stated (unpublished data) that this smell is attenuated with riboflavin supplementation.

Dosage: How to Take L-Carnitine Supplement – Recommended Dosage, Active Amounts:

Carnitine is an essential compound to the performance of the body. It is not a vitamin nor mineral, as the classification for vitamin or mineral denotes that it must be consumed through the diet in order to avoid a disease state.

As carnitine is created in the body to a limited degree and no disease state from the diet exists, it is not classified as a vitamin.

The standard dose for L-carnitine is between 500-2,000 mg. There are various forms of carnitine supplementation available. 

Acetyl-L-Carnitine (ALCAR) is used for cognitive enhancement. L-Carnitine L-Tartrate (LCLT) is typically used for physical performance and power output. Glycine Propionyl-L-Carnitine (GPLC) is used to alleviate intermittent claudication and blood flow issues. L-carnitine is supplemented daily.

The equivalent dosage range for other forms of L-carnitine are as follows:

  • 630-2,500mg (ALCAR)
  • 1,000-4,000mg (LCLT) 
  • 1,000-4,000mg (GPLC)

Conclusion

Powdered products, for example, are much more profitable than others, but most products on the market are unflavored. The unflavored intake of L-carnitine is really not pleasant. Therefore, the liquid forms are always flavored.

The liquid forms, on the other hand, are not suitable for all people. Most products don’t have a dispenser, and tablespoons must be used. You should also gauge it by the eye or drink directly from the bottle, without knowing exactly how much you should take.

These forms are not comfortable for carrying during traveling when the luggage space is limited. While the liquid forms may not be the most comfortable, they are still the preferred choice of many.

Not because of the widespread myth of their efficiency, but mostly because of some people’s problems to swallow capsules or tablets. So when you have to choose your L-carnitine form, don’t stay away from the other forms available. Choose the one that will be most convenient for you.

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