When to Take L-Carnitine for Optimal Training Benefits

Carnitine, derived from an amino acid is a compound necessary for transporting fatty acids into the mitochondria for beta-oxidation to generate energy.

Owing to its role in energy production, some pre-workouts and thermogenics include it in their formulation. However, you might wonder whether it has any immediate effects on training performance or fat burning.

This article discusses l-carnitine supplementation timing so you can optimize its exercise training benefits.

L-Carnitine and Its Various Forms

Carnitine's primary role is transporting fatty acids into the mitochondria to generate energy.

It also regulates compounds that control adipose tissue growth, plays important roles in metabolic pathways involved in muscle protein synthesis, and acts as an antioxidant and anti-inflammatory agent.

The body produces carnitine in the liver, kidneys, and brain from the amino acids lysine and methionine and stores it primarily in the heart and muscle cells. It's also naturally found in foods, especially animal products like beef, poultry, and dairy, and available as a dietary supplement where it's sold alone or alongside other ingredients intended to support fat loss or increase exercise performance.

Many forms of carnitine exist, including L-carnitine, acetyl-L-carnitine, propionyl-L-carnitine, and L-carnitine-L-tartrate. Among these, L-carnitine and acetyl-L-carnitine tend to the most common forms. Supplemental forms aren't absorbed as well as carnitine from dietary sources (1).

When to Take L-Carnitine

Carnitine plays an important role in energy production and glycogen preservation and regulates muscle protein balance between rates of synthesis and breakdown, making supplementation potentially ergogenic.

To this point, a review and meta analysis of 11 trials demonstrated significant improvements in various high-intensity exercise performance measures including time to exhaustion, work capacity, peak power, and number of repetitions and volume lifted in leg press exercises (2).

However, there still remains conflicting data regarding the use of carnitine supplementation to enhance exercise performance due to various factors like dose and timing but also exercise intensity level and training or conditioning of study participants (3).

With regards to dose, the benefits of carnitine are primarily demonstrated when serum carnitine levels increase. The amount necessary to raise serum levels depends mainly on baseline carnitine levels.

Some people may have normal carnitine levels while others may have low levels caused by a genetic problem or certain condition that affects the body's ability to produce or absorb it. For example, people with liver or kidney disease or who are overweight or obese are known to have a carnitine deficiency or lower levels than otherwise healthy people.

Aside from dose, timing may also influence carnitine's effects since some data suggests it has a beneficial effect when taken before exercise but this isn't always the case depending on the person's baseline serum carnitine levels, with lower levels requiring longer supplementation periods to elicit exercise performance benefits.

That said, taking carnitine pre workout could improve exercise performance but long term daily supplementation seems to be required to maintain muscle carnitine levels and the associated benefits, including its muscle recovery benefits for alleviating delayed-onset muscle soreness and markers of muscle damage (4, 5).

For instance, one placebo-controlled clinical trial demonstrated significant improvements in bench press and leg lifting volume along with beneficial changes in total antioxidant capacity in men who supplemented with carnitine daily but not around their workout for nine weeks (6).

Other Benefits of L-Carnitine

In addition to its benefits on exercise performance, carnitine may also promote weight loss and lower inflammation in certain populations.

Weight Loss

By transporting fatty acids into the mitochondria for energy production and controlling fat breakdown and formation, carnitine supplementation may offer weight loss benefits.

A meta-analysis of 43 trials revealed that carnitine supplementation in doses ranging from 500 mg to two grams daily anywhere between two and 54 weeks significantly decreased body weight and fat mass (7).

However, these effects were only demonstrated in people who were overweight or obese. And, although the amount of weight lost was statistically significant, the average loss was 2.4 pounds (1.1 kg), not necessarily clinically significant.

In either case, it's possible that only the overweight or obese people lost weight following supplementation since carnitine concentrations are known to be decreased in higher fat individuals. So by increasing carnitine levels, the rate of fatty acid oxidation could have been returned to normal levels.

Inflammation

Owing to carnitine's strong antioxidant and anti-inflammatory effects, supplementation may be beneficial for improving inflammatory conditions by reducing levels of inflammatory proteins.

To this point, a review of 48 trials demonstrated that carnitine supplementation significantly lowered various markers of inflammation like C-reactive protein, interleukin 6 (IL-6), and tumor necrosis factor (TNF), while increasing total antioxidant capacity (8).

Inflammatory markers are linked with many diseases and infections but are also elevated in those who are overweight or obese. Athletes can also experience a short-term increase in inflammatory markers after strenuous exercise.

Safety of L-Carnitine

Carnitine is relatively well-tolerated but in high doses it may increase levels of trimethylamine-N-oxide (TMAO), a compound linked with an heart disease since it can increase blood pressure and the formation of plaque within the artery walls (atherosclerosis) (9).

However, in certain populations, such as those with fatty liver disease, carnosine may be useful for improving liver function and triglyceride levels, which can decrease heart disease risk (10).

Moreover, because carnitine also offers antioxidant and anti-inflammatory effects, it has been shown to reduce markers of vascular injury in patients undergoing hemodialysis and in those with peripheral vascular disease (11, 12).

So, while it's important to note the rise in TMAO associated with high doses, carnitine supplementation may also offer cardioprotective properties for people with certain conditions.

More research is necessary to confirm carnitine's potential for increasing TMAO levels and the various factors potentially involved like dose, form, treatment duration, and individual factors like diet and activity level of the person supplementing it.

FAQs about L-Carnitine

Does Carnitine Burn Fat?

Carnitine transports fatty acids to the mitochondria where they undergo beta-oxidation for energy. In this way, carnitine assists with breaking down fat to produce energy. Several trials have shown small to moderate weight loss effects with carnitine supplementation in people who are overweight or obese.

Does Carnitine Make You Sweat?

Many supplement ingredients can increase thermogenesis, the process in which the body raises its temperature or energy output. Depending on the dose and other factors, carnitine may make you sweat because it can increase energy expenditure and supports the function of brown adipose tissue, a site of metabolic thermogenesis.

Does Carnitine increase Testosterone?

Carnitine supplementation has been shown to increase testosterone in some people but not others, suggesting an unreliable effect. For instance, carnitine increase levels in men with poor sperm health in one study but not in another study involving athletes (13, 14).

Conclusion

Carnitine is a compound necessary transporting fatty acids into the mitochondrial for energy production. It also plays an important role in muscle protein balance and has antioxidant, anti-inflammatory, and glycogen-sparing effects.

These effects make carnitine supplementation potentially ergogenic, primarily for high-intensity exercise like resistance training, sprinting, combat moves, and jumping.

There doesn't appear to be an optimal time to supplement with carnosine as its benefits are primarily realized only when serum levels are increased. Therefore, when you take carnitine is probably not as important as just remembering to take it.

While carnitine is generally safe, some research suggests it may be pro-atherogenic, but additional long-term trials assessing its effects on the cardiovascular system are necessary.