L-Carnitine: Benefits, Side-Effects, & Dosage Recs

L-carnitine is marketed as a natural mood enhancer, energy booster, and weight loss aid. Supplement manufacturers also say that it promotes post-workout recovery and cardiovascular health. But is there any evidence to support these uses? 

Like with most supplements, the research is mixed. 

Some studies confirm the benefits of l-carnitine benefits on athletic performance and cardiovascular health. Others suggest that it facilitates weight loss and improves brain function. 

These findings make perfect sense. Nearly all cells in your body contain carnitine. This amino-acid-like compound is synthesized from methionine and lysine and used as an energy source by your cells. 

As a dietary supplement, L-carnitine may boost your mood, physical performance, and immune function — but more on that later. 

It’s particularly beneficial for athletes and vegans, as well as for people with malabsorption disorders. When used as part of a well-rounded diet and training program, it can improve your workouts and lead to faster gains. 

For example, a 2014 study conducted on professional football players has found that taking just 3 or 4 grams of l-carnitine before training may ward off fatigue by delaying blood lactate formation. 

As the scientists note, this compound may also increase maximal oxygen consumption, running speed, and muscle endurance. 

Sounds interesting, isn’t it? Let’s see how l-carnitine works and whether or not it’s right for you. 

What Is Carnitine?

Carnitine is often referred to as an amino acid, but it’s actually an umbrella term for several substances derived from amino acids. These include: 

• L-carnitine
• Propionyl-L-carnitine
• Acetyl-L-carnitine
• D-carnitine

The above compounds are found in most cells of the body and support energy production. They’re particularly important for your heart and skeletal muscle, explains the National Institute of Health (NIH). 

L-carnitine is widely used for athletes due to its role in energy production and fat loss. As a sports supplement, it may speed up recovery, attenuate muscle soreness, and boost physical performance. 

Acetyl L-carnitine has similar effects, but it might be a better choice for brain health. It may help slow the progression of cognitive impairment and benefit people with neurodegenerative disorders. 

Propionyl-L-carnitine may improve circulation and increase nitric oxide production, especially when combined with glycine. Therefore, it may help those with hypertension and circulatory problems. 

D-carnitine has no therapeutic uses. In fact, it may affect your body’s ability to absorb and synthesize dietary l-carnitine, leading to deficiencies. 

Generally, l-carnitine and acetyl-L-carnitine supplements are best for overall health and sports performance. Choosing one over another depends on your goals. 

How Does L-Carnitine Work?

This naturally occurring compound is derived from the amino acids lysine and methionine. Its role is to transfer fat to your cells so it can be used for fuel. 

Under normal conditions, your body produces l-carnitine on its own. Some foods, especially animal products, contain this substance too and they may help increase your carnitine intake. 

Steak, for example, provides about 56 to 162 milligrams per serving (4 ounces), reports the NIH. 

The same amount of cooked ground beef supplies 87 to 99 milligrams. Chicken breast, milk, fish, and cheese only contain small doses of this compound. 

Some disorders, like diabetes and cirrhosis, may affect your body’s ability to produce or absorb carnitine. Individuals with liver or kidney disease, as well as those with certain genetic mutations, may develop deficiencies too. 

For this reason, carnitine is considered a conditionally essential nutrient, states a 2010 review in Nutrition and Metabolism. 

According to the above review, l-carnitine supplements may help improve immune function and reduce neuropathic pain in people with diabetes. Furthermore, it may aid in the treatment of certain conditions, such as:

• Alzheimer’s disease
• Dementia
• Chronic heart failure
• Coronary heart disease
• Neuromuscular disorders
• Nerve damage
• Glucose intolerance
• Encephalopathy
• Obesity
• Dry eye
• Retinal disorders

After ingestion, this compound is synthesized in the liver and kidneys. Next, it enters the bloodstream, and then it’s used for energy production by your cells and tissues. 

But its role doesn’t end here. 

As the researchers note, carnitine also improves your body’s ability to use carbs for fuel and regulates fluid levels. Additionally, it helps flush out metabolic waste and prevents it from building up in your system, according to the NIH. 

L-Carnitine and Weight Loss

L-carnitine supplements claim to boost your metabolism and accelerate fat loss. Again, the research is mixed. 

Let’s start with a 2016 research paper published in Obesity Reviews. After analyzing nine different studies conducted on over 900 men and women, scientists concluded that carnitine promotes weight loss, but its effects decrease over time. 

Not all studies support these claims, though. For example, in a clinical trial conducted on moderately overweight women, l-carnitine supplements didn’t produce any changes in fat mass or body weight. 

Another study, which was conducted on overweight active subjects, has found no significant changes in the caloric intake, body composition, and resting metabolic rate of those who took l-carnitine. 

As discussed earlier, this compound helps move fatty acids into the cells to be used for fuel. Therefore, carnitine supplementation should facilitate weight loss. Yet, there isn’t sufficient evidence to confirm its fat-burning effects. 

But this doesn’t mean you should stop using carnitine. From increased endurance to improved brain function, this supplement has many other benefits. 

At Old School Labs, we use L-carnitine tartrate in our pre-workout formulas. This fast-absorbing form of carnitine supports your heart, brain, and muscle function, leading to enhanced physical performance. 

Vintage Blast™, the only two-stage pre-workout formula on the market, contains a unique mix of L-carnitine tartrate, amino acids, vitamins, and minerals for mind-blowing energy and stamina. This combo will take your workouts to a whole new level and help you recover faster from training. 

Effects of L-Carnitine on Exercise Performance 

L-carnitine is widely used by strength and endurance athletes due to its performance-enhancing effects. 

This amino-acid-like compound may help prevent cellular damage and reduce exercise-induced stress. At the same time, it decreases plasma lactate levels, which may further improve post-workout recovery time. 

Current research published in the journal Nutrients suggests that L-carnitine supplements mat help increase power output and VO2 max (maximum oxygen consumption). Other potential benefits include:

• Reduces muscle soreness 
• Inhibits free radical formation after exercise
• Increases blood and oxygen flow to the muscles
• Improves endothelial function
• May help increase lean mass and reduce body weight in older adults
• Boosts your energy while reducing mental and physical fatigue
• Prevents age-related muscle loss
• May improve lipid metabolism and muscle function
• Decreases heart rate

In one study, top athletes who took l-carnitine supplements experienced major improvements in lipid metabolism, VO2 max, and physical output. Their lactic acid levels after exercise were significantly lower than normal. 

A more recent study featured in the Journal of Strength and Conditioning Research assessed the effects of L-carnitine L-tartrate on strength training and recovery. 

This compound decreased exercise-induced muscle damage and increased IGFBP-3 (Insulin-like growth factor-binding protein 3) before and after training. 

L-carnitine has been also shown to improve vascular function, reduce oxidative stress, and attenuate muscle soreness. When combined with resistance training, it may protect against the age-related decline in lean mass and strength.

According to the Nutrients review, a single dose of 3 to 4 grams of l-carnitine may help increase running speed and ward off fatigue in football players while lowering their heart rate. This nutrient prevents your body from using muscle protein for fuel, leading to greater protein synthesis and reduced catabolism. 

L-carnitine: Heart Strength and Health

The above findings indicate that carnitine benefits most athletes, from runners and football players to bodybuilders. In the long run, it may help lower your blood pressure and boost cardiovascular health. 

In one study, subjects who took as little as 2 grams of acetyl-L-carnitine per day for six months experienced significant reductions in both systolic and diastolic blood pressure with no side effects. Their insulin levels and glucose metabolism improved too. 

L-carnitine may also benefit those with existing cardiovascular problems, suggests a study published in the Journal of the American College of Cardiology. Furthermore, it may help preserve cardiac function and increase exercise capacity in people with heart failure. 

According to the NIH, supplementation with l-carnitine for up to one year may improve heart health. This compound may also reduce insulin resistance and improve glycemic control, making it easier to manage diabetes symptoms. 

L-Carnitine Effects on Brain Function

This supplement isn’t good just for your body — it benefits your brain as well. 

In a clinical trial conducted on subjects with Alzheimer’s disease, acetyl-L-carnitine slowed down cognitive decline and improved cognitive function. Another study indicates that it may boost short-term memory. 

This nutrient may also improve mental function and speed up recovery from substance abuse, reports a study in the International Journal of Clinical Pharmacology Research. Researchers say that acetyl-L-carnitine may attenuate the subtle cognitive disturbances associated with alcohol abuse. 

L-carnitine in all its forms exhibits neuroprotective effects. Scientists believe it may have something to do with its antioxidant and anti-inflammatory action, as well as its ability to regulate energy metabolism. 

Other studies suggest that carnitine may help with depression, narcolepsy, and sleep disorders, but more research is needed in these areas.

L-Carnitine Dosage Recommendations 

Carnitine deficiencies are uncommon in healthy people, notes the Linus Pauling Institute. In rare cases, certain genetic defects or acquired conditions may affect the body’s ability to metabolize this compound. 

If you’re an athlete or gym-goer, try not to exceed 2 grams of l-carnitine per day. Get at least 0.5 grams a day to reap the benefits. The same recommendations apply to acetyl-L-carnitine too.  

This supplement works best when ingested along with protein and carbs. Consider taking l-carnitine right before or during a meal to make sure it’s fully absorbed. As far as acetyl L-carnitine, you may take it on an empty stomach.  

Are There Any Side Effects?

L-carnitine is safe and well-tolerated. Some individuals may experience mild abdominal discomfort, nausea, or diarrhea, but these side effects are typically associated with doses above 3 grams per day.

Note that antibiotics and anticonvulsants reduce carnitine levels in the bloodstream and may lead to deficiencies. 

Apart from that, there are no known interactions between l-carnitine and medications or dietary supplements.

Should You Take L-Carnitine?

As you see, L-carnitine is one of the safest and most well-researched sports supplements. Its effects on weight loss are subject to debate, but it has plenty of other benefits for athletes. 

Increased energy and endurance, reduced muscle damage, and faster recovery rates are just a few to mention. Over time, it may slow down cognitive decline and boost heart health. 

We recommend using l-carnitine as part of a pre-workout formula to boost your energy and last longer in the gym. Plus, you’ll have less muscle pain and soreness. 

How do you feel about carnitine? What’s your experience with it? Let us know in the comments section below!