L-carnitine: What you need to know

L-carnitine plays a crucial role in converting fat into energy. And while the body successfully converts certain amino acids into L-carnitine, some people can benefit from taking supplements or eating foods that are naturally rich in the substance. To find out how L-carnitine impacts well-being, and whether you should increase your intake, keep reading.

What is L-carnitine?

Derived from amino acids, levocarnitine (commonly called L-carnitine) is a conditionally essential nutrient—meaning the body only produces what it needs, when it needs it. For most people, this process happens without intervention, and a balanced diet will provide all the L-carnitine they need.^[1]

Still, there are circumstances where L-carnitine production is lacking, making specific foods and supplements a must. There may also be physical wellness benefits associated with supplementing L-carnitine, a topic we'll cover in more detail shortly. For now, let's focus on how the nutrient works.

How does L-carnitine work?

In humans, L-carnitine plays a sophisticated role in energy production, specifically turning fat into energy. It does this by providing fatty acids to cell mitochondria, the “powerhouse” of cells. Mitochondria are responsible for producing chemical energy and powering cells so they can function correctly.

However, to create L-carnitine, the body uses two precursor amino acids: lysine and methionine. It then converts these compounds, inside the liver, into L-carnitine, before storing the nutrient in muscles (over 95%) and the brain for when they need its energy-boosting abilities.

Different types of L-carnitine

Although L-carnitine is commonly available in supplements and food, it is one of several nutrients belonging to the wider carnitine family. Each variation helps with energy production but has a slightly different mechanism and outcome inside the body.

• Acetyl-L-carnitine: Although very similar to L-carnitine, acetyl-L-carnitine (ALCAR) is better at crossing the blood–brain barrier. Researchers are actively exploring its potential in cognitive disorders.^[2]

• D-carnitine: This version is the antihero of the carnitine family, as it can block the absorption of more valuable forms.

• L-carnitine L-tartrate: Popular with athletes and the fitness industry, L-carnitine L-tartrate is thought to influence muscle growth and exercise performance.^[3]

• Propionyl-L-carnitine: This form of L-carnitine is closely linked to the respiratory system, with possible benefits to anaerobic performance.^[4]

What are the potential benefits of L-carnitine?

Given L-carnitine's role in converting fat into energy and its abundance in muscle tissue, the potential benefits extend to two closely linked processes—muscle recovery and weight loss.

L-carnitine and muscle recovery

A 2018 review gives us fairly detailed insight into the role of L-carnitine in sports performance. Interestingly, the researchers summarise that not only could supplementation be beneficial in a "healthy young active population", but also "older subjects engaged in moderate exercise".^[5]

The paper outlines the areas L-carnitine could influence, including muscle sarcomeres, lean muscle function, and mitochondrial dysfunction. While this all sounds positive, it's important to highlight that the outcomes vary depending on age, sex, stress level, and training intensity, with researchers acknowledging that further research is warranted.

L-carnitine and weight loss

The connection between L-carnitine and weight loss stems from the nutrient's role in converting fat into energy. However, with a topic as complex as body mass, is it really as simple as increasing L-carnitine levels to achieve greater fat loss?

A 2016 systematic review and meta-analysis asks this very question, examining the effect of L-carnitine on weight loss in adults. Results from nine studies indicate that "subjects who received carnitine lost significantly more weight and showed a decrease in body mass index". As a result, the researchers conclude that there is potential for carnitine to form part of a multi-treatment approach to weight loss.^[6]

Though promising, this review does not offer enough evidence to confidently assert that increasing L-carnitine levels correlates with fat loss.

How to dose L-carnitine

While there are general dosing guidelines for L-carnitine (and its variations), research has yet to identify optimal ranges. Instead, guided by advice from your doctor or physician, it's up to you to find a dose and schedule that meets your wellness needs.

To support your decision-making, the dose ranges used across research papers include:

• L-carnitine: 500–2000mg daily
• Acetyl-L-carnitine: 600–2500mg daily
• L-carnitine L-tartrate: 1000–4000mg daily
• Propionyl-L-carnitine: 400–1000mg daily

It's important to highlight that the National Institute of Health does not give a recommendation on L-carnitine intake. After a review of the evidence in 1989, they concluded it was not an essential nutrient. Not only does the body produce the L-carnitine it needs to function, but most of us get enough supplementary L-carnitine from a balanced diet.[1]

Which foods contain L-carnitine?

With an idea of how much L-carnitine to consume, you have two options for increasing intake—food or supplements. The former won't contain as much L-carnitine, but may be a better fit depending on your lifestyle and nutritional goals.

L-carnitine-rich foods include:

• Beef steak
• Ground beef
• Cheese
• Milk
• Cod

You've probably noticed that the most abundant natural sources of L-carnitine are animal products. There is a small amount of L-carnitine in cooked asparagus and whole wheat bread (0.1–0.2mg). Still, by comparison, 100 grams of beef steak contains up to 162mg of L-carnitine, making it a far superior option.

When should you take L-carnitine?

The last consideration when taking L-carnitine is timing. Several studies show that the best time to take L-carnitine is shortly before exercise. This means eating one of the foods listed above, or taking supplements, roughly 1–2 hours before physical activity.

If you miss this relatively small window, it isn't the end of the world, so think of it as a recommendation rather than a definitive rule. Ultimately, the best time to take L-carnitine is whichever time best suits your lifestyle.

What are the side effects of L-carnitine?

So far, we've talked almost exclusively about the possible benefits of L-carnitine, but what about downsides? Even a nutrient as crucial to energy production as L-carnitine has some potential side effects, especially if you consume highly concentrated supplements.

Mild side effects linked to L-carnitine include:

• Nausea
• Upset stomach
• Fishy body odour

Most studies support the use of up to 2000mg (2g) of L-carnitine daily. However, there aren't many extensive studies on the long-term implications, so be wary of going above the general recommendations for long periods.

Is L-carnitine safe?

L-carnitine is a naturally occurring nutrient with a fundamental role in energy production, but should you be concerned about increasing L-carnitine levels?

For most people, a balanced diet will provide sufficient L-carnitine levels, and therefore many governing bodies don't recommend a minimum daily intake. That said, underlying health conditions or certain lifestyles may warrant L-carnitine supplementation.

Most of the time, supplements are more advisable than food sources for this purpose, simply because concentrations of L-carnitine are significantly higher in the former. If you think you could benefit from increasing your L-carnitine intake, your doctor or physician is the best person to speak to. With case-specific advice, you can make an informed decision.

Ready to add L-carnitine to your daily wellness routine? Experience Body Energizer, available now from the Cibdol store. Or, to learn more about the role of amino acids in mental and physical well-being, visit our Education section.