By Rachael Link, MS, RD
Let’s face it: Amino acids are crucial to pretty much every aspect of health. These compounds are the building blocks of proteins, which make up our skin, hair and muscles and perform a variety of functions in the body. When it comes to health, though, some amino acids, like L-carnitine and glycine, stand out from the rest.
Found only in small amounts in certain foods like beef, fish and chicken, it’s safe to say that many of us aren’t getting enough L-carnitine in our diets. Fortunately, it’s also available in capsule, liquid or injectable form to help supply a quick and concentrated dose of carnitine.
This superstar supplement has been shown to do everything from enhance athletic performance to bring fat burning to the next level. Here’s what you need to know about this important amino acid and what it can do for you.
What Is L-Carnitine?
Carnitine is a type of amino acid that benefits energy levels by transporting fatty acids into the mitochondria where they can be burned up and used as fuel. For this reason, many take carnitine as a weight loss supplement to help bump up fat burning.
Carnitine occurs in two forms, or isomers: L-carnitine and D-carnitine. L-carnitine is the active form that plays a role in energy metabolism and production. It is produced within the body, but it can also be taken as a supplement or found in many different protein foods as well. In supplement form, it’s available as a capsule, liquid or even injectable.
A deficiency in carnitine can be caused by an inadequate intake, excess loss through diarrhea or dialysis, liver disorders, the use of certain medications, and some genetic disorders. Additionally, because it is primarily found in animal products, vegans and vegetarians are at a higher risk of deficiency.
Although many people take L-carnitine as a way to speed up weight loss and fat burning, carnitine benefits include enhancing brain function, preventing muscle damage, regulating blood sugar and increasing endurance as well.
- Increases Endurance
- Enhances Weight Loss
- Prevents Muscle Damage
- Amps Up Fat Burning
- Boosts Brain Function
- Regulates Blood Sugar
1. Increases Endurance
Because L-carnitine plays a central role in energy production, many athletes begin taking it as a way to enhance endurance and boost athletic performance. Both human and animal studies have confirmed the beneficial effects of this amino acid on endurance levels.
In one study out of Turkey published in the Journal of Strength and Conditioning Research, giving professional soccer players three to four grams of L-carnitine before exercise was found to prolong the time it took to reach exhaustion. (1) Similarly, an animal study out of India published in the journal Wilderness & Environmental Medicine showed that giving rats L-carnitine improved exercise endurance. (2)
For this reason, supplementing with this amino acid may especially benefit endurance athletes, such as long-distance runners, swimmers or cyclists.
2. Enhances Weight Loss
Many people look to L-carnitine as a way to help shed unwanted pounds and lose weight fast. When combined with diet and exercise, some studies have found that supplementing with it can, in fact, be an effective way to enhance weight loss.
One analysis of research out of Iran looked at the results of nine studies and found that supplementing with carnitine led to a significantly greater amount of weight loss as well as a larger drop in body mass index compared to a control group. (3)
However, L-carnitine weight loss results may vary, and other studies have turned up mixed results. In a study out of Australia published in the International Journal of Sports Nutrition and Exercise Metabolism, for instance, 36 obese women took either L-carnitine or a placebo and completed eight weeks of aerobic training. At the end of the study, researchers concluded that L-carnitine had no impact on either total body mass or fat mass. (4)
While L-carnitine may work for some people, it shouldn’t be considered a quick fix. Pair it with regular exercise and a healthy diet to see maximum results.
3. Prevents Muscle Damage
Besides increasing endurance and amping up weight loss, this amino acid also makes a useful supplement for athletes looking to prevent and protect against muscle damage.
In one 2014 study published in the Asian Journal of Sports Medicine, 21 male athletes were given either L-carnitine or a placebo daily for two weeks prior to an athletic test. Compared to the control group, those who took L-carnitine were found to have lower levels of certain markers that indicate muscle damage. (5)
Other ways to aid in muscle recovery include eating lots of anti-inflammatory foods, loading up on fruits and vegetables, and getting enough protein in your diet.
4. Amps Up Fat Burning
Besides increasing weight loss, this amino acid also helps kick up fat burning as well. In one study conducted in Germany, overweight participants received a regular diet, either with or without the addition of L-carnitine. After 10 days, L-carnitine was found to significantly increase the breakdown of fat. (6)
Another study published in the Journal of Physiology showed that increasing the amount of carnitine in the muscles helped prevent fat gain by increasing fat burning and energy expenditure during physical activity. (7)
Other fat-burning foods include apple cider vinegar, bone broth, cayenne pepper and chia seeds.
5. Boosts Brain Function
L-carnitine isn’t just good for your body, but it’s good for your mind as well. In fact, promising research has found that it may positively impact brain function and cognition.
One study conducted by the University of Catania in Italy and published in the American Journal of Clinical Nutrition looked at the effects of daily L-carnitine supplementation on mental and physical fatigue in elderly participants over 100 years old. Not only was it found to reduce total fat mass and increase muscle mass, but it also helped decrease fatigue and improve cognitive function. (8)
Avocados, beets, blueberries and broccoli are also brain foods that can help enhance your focus and memory.
6. Regulates Blood Sugar
Some promising research has shown that carnitine supplementation could aid in maintaining normal blood sugar levels and fighting insulin resistance. Insulin is the hormone responsible for transporting sugar from the bloodstream to the cells where it can be used as fuel. Too much insulin can lead to insulin resistance, decreasing its effectiveness and resulting in high blood sugar.
A study out of Rome published in the Journal of the American College of Nutrition showed that infusing diabetic participants with L-carnitine improved insulin sensitivity and increased the uptake of sugar from the bloodstream. (11) Another small study in 2010 conducted at Sapienza University’s Department of Clinical Medicine in Rome found that combining L-carnitine with caloric restriction helped reduce insulin resistance and increase sensitivity. (12)
Controlling your carb intake, including more fiber and protein foods in your diet, and using natural stress relievers can also help keep blood sugar in check.
L-Carnitine vs. Acetyl-L-Carnitine
L-carnitine and acetyl-L-carnitine are two different forms of the same amino acid, but acetyl-L-carnitine has been processed so it’s able to pass the blood-brain barrier. Both are commonly supplemented in the diet, but they each boast unique benefits to health.
While L-carnitine is primarily used to kick-start fat burning and enhance athletic performance, acetyl-L-carnitine also benefits brain health and memory.
Although both can be used concurrently, it’s not always necessary. Taking acetyl-L-carnitine can supply the same benefits as L-carnitine, with the bonus brain-boosting benefits as well.
L-Carnitine Food Sources
Animal products are the best natural sources of L-carnitine, with foods like grass-fed beef packing in the highest amount per serving. It can also be found in small amounts in some sources like vegetables and grains. Here are the foods that contain the most L-carnitine per serving, according to the National Institutes of Health: (13)
- Beef steak, cooked, 4 ounces: 56–162 milligrams
- Ground beef, cooked, 4 ounces: 87–99 milligrams
- Whole milk, 1 cup: 8 milligrams
- Codfish, cooked, 4 ounces: 4–7 milligrams
- Chicken breast, cooked, 4 ounces: 3–5 milligrams
- Ice cream, 1/2 cup: 3 milligrams
- Cheddar cheese, 2 ounces: 2 milligrams
- Whole wheat bread, 2 slices: 0.2 milligram
- Asparagus, cooked, 1/2 cup: 0.1 milligram
L-Carnitine Supplements + Dosage
Although carnitine can be found naturally in plenty of food sources, it’s also available in supplement form as well. It can be found in L-carnitine liquid, capsule and injectable forms for a quick and convenient way to boost your carnitine levels. For oral L-carnitine, be sure to take it with meals to maximize its effectiveness.
The standard L-carnitine dosage is 500–2,000 milligrams daily. Based on most current research available, a dose of up to two grams per day can be used safely and effectively with minimal side effects.
The dosage may vary by the type of L-carnitine supplement, however. Acetyl-L-carnitine, for example, can be used in doses up to 2,500 milligrams per day while the dose for L-Carnitine L-Tartrate, a form typically used to enhance athletic performance, can range all the way up to 4,000 milligrams.
Keep in mind that when adding any supplement into your routine, you should always start with a low dose and work your way up to ensure you’re able to tolerate it without adverse side effects.
L-Carnitine Uses + Recipes
Most people use L-carnitine to help boost weight loss and increase fat burning. However, there are many other potential reasons you may want to add carnitine into your diet.
It can correct deficiencies, boost brain function, prevent muscle damage, increase endurance and enhance athletic performance.
It can also be incredibly useful for vegans and vegetarians who may have a limited intake of carnitine-rich foods. Taking a supplement can be an easy way to help meet your needs for this crucial amino acid.
If you’re looking for some ways to increase your carnitine intake without the use of a supplement, including a few servings of carnitine-rich foods can help. Here are some recipes that are high in carnitine for you to try out:
When used as directed, carnitine can be safe and effective with minimal risk of side effects. Common L-carnitine side effects include stomach pain, nausea, vomiting and diarrhea.
L-carnitine may increase the risk of seizures in those with epilepsy. If you’ve had a seizure before, you should not take carnitine.
Additionally, carnitine may worsen symptoms of hypothyroidism. If you have an underactive thyroid, you should consult with your doctor before taking this amino acid.
When starting carnitine, as with any supplement, it’s best to start with a low dose and increase slowly to assess tolerance. If you experience any negative side effects, be sure to report to your doctor to determine if supplementation is right for you.
Finally, keep in mind that carnitine may enhance fat loss and weight loss for some people, but it should be used in combination with a healthy diet and active lifestyle to see the most results.
- L-carnitine is an amino acid that works by transporting fatty acids to the mitochondria where they can be broken down into fuel.
- This amino acid is produced in the body and is also found in small amounts in certain types of food, like animal products.
- Although safe in moderation, potential carnitine side effects include stomach pain, nausea, vomiting and diarrhea.
- When paired with a healthy lifestyle and nutritious diet, taking carnitine could offer a variety of health benefits.
- In fact, studies show that carnitine could help increase endurance, enhance weight loss, prevent muscle damage, amp up fat burning, boost brain function and regulate blood sugar.
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