Written by Garett Reid | NSCA, CSCS, CISSN, M.S.E.S.S
Fact checked by Andrew Lenau, ISSA CPT & Sports Nutritionist
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L-carnitine has become quite popular in the fitness industry over the past few years as it's become well known for its ability to support weight loss, fight disease, improve health and brain function, and lead to better aging.
And as a naturally produced amino acid, it seems to pop up in every new fat burner as the latest "must-have" ingredient. But what exactly is L-carnitine, and how does it work?
In this article, we'll see if l-carnitine is all it's cracked up to be, along with providing you with the best time, dose, and method to take it for optimal results.
Table of Contents:
- What Is L-Carnitine?
- Different Types of L Carnitine
- Benefits Of Acetyl L Carnitine
- How And When To Take L Carnitine
- When To Take L Carnitine For Fat Loss
- What Is The Best L Carnitine Dosage?
- L-Carnitine Dosage For Weight Loss
- Is L Carnitine Safe?
- How Long Should I Take An L-Carnitine Supplement?
- The Best Fat Burner With L-Carnitine
- FAQs
What Is L Carnitine?
L-carnitine is an amino acid that is naturally occurring in our environment as well as our bodies.
Your body can produce l-carnitine naturally by synthesizing the amino acids lysine and methionine. Just make sure to get your daily dose of vitamin C, as it's a central component of this synthesis.
In addition to the natural production of l-carnitine, you can also eat small amounts by consuming various animal products such as meat and dairy (carn=meat). Below is the l-carnitine content of some whole foods:
|
Food |
Serving |
L-Carnitine (mg) |
|
Beef steak |
3 ounces |
81 |
|
Ground beef |
3 ounces |
80 |
|
Pork |
3 ounces |
24 |
|
Canadian bacon |
3 ounces |
20 |
|
Milk (whole) |
8 fluid ounces (1 cup) |
8 |
|
Fish (cod) |
3 ounces |
5 |
|
Chicken breast |
3 ounces |
3 |
|
Ice cream |
4 ounces (½ cup) |
3 |
|
Avocado |
1 medium |
2 |
|
American cheese |
1 ounce |
1 |
|
Whole-wheat bread |
2 slices |
0.2 |
|
Asparagus |
6 spears (½ cup) |
0.2 |
Source: Oregon State University
Even though you can produce l-carnitine by yourself, l-carnitine is considered a conditionally essential nutrient. Many people either can't make or don't consume enough, whether from poor diet or genetic issues. As such, plenty of conditions require extra care to ensure you're meeting your needs.
One situation where this rings true is in vegans, who tend to have a l-carnitine deficiency. As vegans don't eat animal products, the primary source of l-carnitine, it's challenging for them to maintain an adequate supply.
Enter l-carnitine supplementation. Vegans and similarly deficient populations can take exogenous l-carnitine in supplemental form, whether pill or powder.
Different Types of L Carnitine Supplements
It's important to understand that there are various forms of l-carnitine, meaning there are several different types of l-carnitine that you could buy.
1) D-carnitine:
D-carnitine is an inactive form of carnitine. It can help to reduce blood levels of carnitine and increase fat buildup, leading to liver inflammation and oxidative stress¹.
2) Acetyl-L-carnitine:
Acetyl-l-carnitine (ALCAR) is believed to be the most effective form of carnitine for brain health. Studies suggest that it may benefit people with neurodegenerative diseases².
I like Naturalife Labs Acetyl L-Carnitine, which contains 1,500mg of 100% pure Acetyl L-Carnitine per serving and can help improve mood, energy, learning, and memory.
3) Propionyl-L-carnitine:
Propionyl-L-carnitine is a form of l-carnitine usually attributed to treating circulatory issues such as peripheral vascular disease and high blood pressure. Research shows it may improve blood flow through the increase in the production of nitric oxide³.
Looking for a product recommendation? Swanson Propionyl L-Carnitine with Glycine contains 515mg propionyl l-carnitine and 150mg glycine per capsule, supporting cardiovascular health, cellular energy, and muscle strength.
4) L-carnitine L-tartrate:
The most common variation of l-carnitine for improved sports performance is l-carnitine l-tartrate, commonly added to sports supplements due to its rapid absorption rate. It may aid muscle soreness and recovery in exercise⁴.
I recommend Nutricost L-Carnitine Tartrate Powder, which delivers 1 gram of L-carnitine tartrate per serving and is manufactured in a GMP-compliant, FDA-registered facility.
L-Carnitine's Role In The Body
L-carnitine plays several roles inside the human body, with its primary function being to optimize mitochondrial function and energy production.
By transporting fatty acids into the cell's mitochondria, it allows them to be converted into energy. And if you remember anything from your middle school biology class, fatty acids provide an incredibly sustainable energy source. Tissues with high energy requirements (read: the brain and the heart) especially rely on fatty acids for energy.
Research suggests this can play a role in the following:
- Promotes healthy aging
- Supports weight loss
- Helps to fight disease
- Improves health and brain function
Different variations of l-carnitine supplements are suited for different purposes, so it's important to know why you want to take l-carnitine.
5 Benefits Of Acetyl L-Carnitine
Now that you know what l-carnitine does, let's go over the science-backed benefits. Research suggests that l-carnitine plays a role in several different processes, many of which surround the conversion of fatty acids into fuel.
Maintaining high energy levels can mitigate mitochondrial dysfunction and keep your systems running optimally.
1) Promotes Fat Loss:
As mentioned above, l-carnitine plays a significant role in energy production and mitochondrial function. Since l-carnitine is a primary fatty acid transportation system, it makes sense that with more available l-carnitine, one can transport more fatty acids, resulting in more fat loss.
One meta-analysis researched and compared nine studies of the effect of l-carnitine supplementation on weight loss⁵. They concluded that overweight individuals who supplemented lost an extra 2.9 lbs (1.3 kg).
In 2020, another meta-analysis looked at 37 different randomized controlled studies researching the effects of l-carnitine on body fat percentage, body composition, and BMI⁶.
In conclusion, they determined that l-carnitine supplementation modestly affected fat loss. Specifically:
- Reduced body weight −1.21 kg
- Reduced BMI by −0.24 kg/m2
- Reduced fat mass by −2.08 kg
You can learn more about this in our article: L Carnitine For Weight Loss: Does It Actually Work?
2) Improves Heart Health:
Due to its role in transferring of long chain fatty acids, l-carnitine has long been considered as a way to help normalize lipid profiles and improve glycemic control.
A recent study from 2020 showed this to be true⁷. When taking 1,500mg daily, l-carnitine supplementation successfully improved lipid profiles by increasing HDL and lowering LDL cholesterol.
In 2017, a meta-analysis found that supplementation effectively treated patients with congestive heart failure⁸. In these studies, the amount taken ranged from 1,500mg-6,000mg a day.
3) Treats Diabetes:
Diabetes is a significant health issue in the Western world, with approximately 10.5% of the American population affected. With that being the case, any effective therapy could bring immense benefits.
A review from 2023 looked at 41 different trials and concluded with positive results⁹. Results showed that L-carnitine supplementation reduced both fasting blood sugar and hemoglobin A1c.
In addition, it improved insulin sensitivity in people with diabetes, possibly due to the optimization of pancreatic cell function, which is responsible for insulin production.
4) Reduces Depression:
While it is still largely misunderstood, l-carnitine is thought to be capable of reducing symptoms of depression. As of now, numerous studies back this belief.
For example, in 2018, a meta-analysis was performed and looked at 12 different studies examining the relationship between l-carnitine and depression10.
Not only did they find that l-carnitine supplementation improved symptoms better than placebos, but researchers also found that it produced similar results to common anti-depression medication.
5) Improves Exercise Performance:
Due to its role in energy production, it's believed that l-carnitine plays a role in several performance-related areas. For example, l-carnitine supplementation has been used by both elite and recreational athletes to help optimize workout recovery. Various benefits include less discomfort and faster recovery times¹¹.
Another key benefit of l carnitine supplements is improved endurance through reduced fatigue¹². This comes from its ability to increase oxygen supply, blood flow, and nitric oxide production.
How And When To Take L-Carnitine
Regarding the timing of l-carnitine supplementation, researchers don't have any evidence that timing matters much, apart from one bit of nuanced information.
We do know that insulin is required to load l-carnitine into the skeletal muscle cells. For this reason, you should always pair your l-carnitine consumption with healthy carbs to cause an insulin spike¹³. Therefore, the best time to take your l-carnitine is with a meal containing anywhere from 30-60g of carbs.
The only other instance where timing can make a difference is for improved performance. If you want to use l-carnitine supplementation to enhance performance, take it 30-60 minutes before an event. This will allow your body to optimize the utilization of fats for fuel, saving glucose and enhancing endurance and workload.
When To Take L-Carnitine For Fat Loss
As you can see, research on timing for l-carnitine is still in its infancy. I'm still not entirely sure of the specific mechanisms of fat loss, so researchers aren't positive about the best time to take l-carnitine for fat loss, if one exists.
Of all of the different benefits of l-carnitine, exercise performance is the only one we have a good rationale for timing. Due to increased fat metabolism, you should take l-carnitine 1 hour before exercise.
However, keep in mind that l-carnitine can improve muscle endurance and workload. If l-carnitine can help you perform more work in the gym, this will also translate to more calories burned. Therefore, if you are working out (which you should be!), adding some l-carnitine to your peri-workout supplement stack makes sense.
Looking for other ways to amp up your supplement stack and boost fat loss? Check out our 8 Best Supplements For Fat Loss to load up on the top, evidence-based ingredients to lose weight.
What Is The Best L-Carnitine Dosage?
Dosing can vary quite a bit, but most studies recommend 500-1,500mg per day14. That said, due to bioavailability issues, many recommend a much higher dosage, such as:
- L-Carnitine: 4-6 grams
- L-Carnitine L-Tartrate: 6-8 grams
As mentioned, for best results, take the above dose with 60g of carbs, as it's believed to help with absorption. Finally, l-carnitine may require chronic oral ingestion to build up in the muscle cells. Therefore, it's believed that you may need to take it for an extended period to see any real effects.
L-Carnitine Dosage For Weight Loss
The optimum dosage for weight loss is hard to pinpoint. While studies suggest 1,500mg a day, many actual users will suggest 3g/ day or even consuming 2g twice a day.
Note that these numbers are in addition to whatever you consume throughout the day in your diet. However, it's incredibly difficult to accurately track how much you eat through food.
Therefore, if you eat a lot of meat, your l-carnitine supplementation requirements may be on the lower end. However, you'll need a higher daily dose if you're a vegan or don't eat much meat.
To learn more about l carnitine and losing weight, head to our article: Is L Carnitine Good For Weight Loss?
Is L-Carnitine Safe?
Generally speaking, l-carnitine supplements are considered safe. Of course, there's always an upper maximum tolerable limit, but it's unclear what it is.
Studies suggest it could range depending on the person, but some science and anecdotal evidence suggest 6g a day, so we'd err on the side of caution.
How Long Should I Take An L-Carnitine Supplement?
When taking l-carnitine, you need to understand that it is different from other supplements. Unlike a pre-workout which can be felt immediately, it can take weeks or even months to notice a substantial improvement.
Therefore, if you're considering taking l-carnitine, you should be prepared to take it daily for at least a few months. Fortunately, it seems that you can take carnitine every day for 12 months without any adverse reaction.
Reddit users help shed light on some real experiences:
"I've been using 3g of oral l-carnitine with 3g of garlic every morning while fasting. I normally cut by fasting, but this time, I have definitely noticed a difference In how much fat I am losing, and I am retaining more muscle proportionally." (source)
"L-Carnitine is the only thing so far that is truly helping me lose unwanted fat. I always drink a tablespoon of 3000mg 45 minutes before my cardio workouts, and I just love the endurance boost it gives me." (source)
What Is The Best Fat Burner With L-Carnitine?
While you can purchase l-carnitine as an independent supplement in powder or pill form, another popular method of consumption is through a fat burner. These are supplements that will contain l-carnitine as well as other compounds that will aid in weight loss.
One of my favorite l-carnitine-containing fat burners is Kaged Muscle Clean Burn. One serving of Clean Burn provides 1000mg of l-carnitine tartrate, which will help metabolize fat and improve athletic performance.
Clean Burn also contains:
- Green Tea Extract: For a thermogenic and mild stimulation
- ChromeMate®: Improve fat metabolism
- Gymnema Sylvestre Extract: Decrease cravings for sweets
While most weight-loss formulas only address one of the typical person’s weight management challenges, Clean Burn™ attacks the problem from multiple angles! Losing weight is...
Another powerhouse of a fat burner is Transparent Labs Stim-Free. Each serving delivers 1000mg of acetyl-l-carnitine, but that's just the start. You also get the following:
- Citrulline Malate: 6,000mg
- Beta-Alinine: 2,000mg
- Organic Caffeine: 180mg
- L-Theanine: 180mg
- Plus about ten other quality ingredients
With a unique combination of clean and natural fat burning ingredients, PhysiqueSeries Fat Burner Stim-Free is perfect for anyone intolerant to stimulants looking...
One of the benefits of l-carnitine as a fat-burning ingredient is that it's non-stimulating. That means it's featured in many a non-stim fat burner, such as the Clean Burn from Kaged I just discussed. While it does contain some green tea extract, it's too small of an amount for any real "stimulant" effects.
FAQs
In case you have any lingering questions, let's examine some of the more common things people ask about l-carnitine supplementation.
When is the best time to take l-carnitine?
For exercise performance or weight loss, taking l-carnitine 30-60 minutes before exercise seems to be the most commonly suggested time.
Can I take l-carnitine without exercise?
Absolutely! l-carnitine has numerous benefits completely separate from exercise, such as an improved heart health.
Can I take l-carnitine and l-glutamine together?
Yes! These compounds work through different mechanisms so can be taken together.
Can you take l-carnitine and creatine together?
Yes! In fact, studies that look at the effect of pairing these compounds show a lot of success¹⁵.
Should I cycle l-carnitine?
There are no studies that suggest this would be helpful.
Where can I buy acetyl-l-carnitine?
Acetyl l-carnitine can be purchased at just about any nutrition store or pharmacy. However, the most popular place will definitely be Amazon. For example, check out Naturalife Labs Acetyl L-Carnitine, which has a 4.5-star rating from 10,254 real users. That's about as top-rated as you can get.
When To Take L-Carnitine: Final Summary
L-carnitine appears to be a promising supplement assuming you have the proper expectations. When it comes to weight loss, understand that l-carnitine is not a miracle drug that will melt fat off of you.
You must still commit to a calorie-restricted diet and an effective weight-based exercise program. Once you have this under control, consistent l-carnitine supplementation can accelerate your weight loss efforts.
Finally, its role in general health and wellness makes it an important compound for just about everyone, not just those who wish to lose weight.
If taking L-carnitine for weight loss is your main goal, check out these 8 Best Fat Burners For Men and the 9 Best Fat Burners For Women, many of which combine l-carnitine with other proven fat-burning ingredients!
While most weight-loss formulas only address one of the typical person’s weight management challenges, Clean Burn™ attacks the problem from multiple angles! Losing weight is...
References
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- Traina G. (2016). The neurobiology of acetyl-L-carnitine. Frontiers in bioscience (Landmark edition), 21(7). https://doi.org/10.2741/4459
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- Asadi, M., Rahimlou, M., Shishehbor, F., & Mansoori, A. (2020). The effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled clinical trials. Clinical nutrition (Edinburgh, Scotland), 39(1). https://doi.org/10.1016/j.clnu.2019.01.020
- Song X, Qu H, Yang Z, Rong J, Cai W, Zhou H. Efficacy and Safety of L-Carnitine Treatment for Chronic Heart Failure: A Meta-Analysis of Randomized Controlled Trials. Biomed Res Int. 2017;2017:6274854. doi:10.1155/2017/6274854
- Zamani, M., Pahlavani, N., Nikbaf-Shandiz, M., Rasaei, N., Ghaffarian-Ensaf, R., Asbaghi, O., Shiraseb, F., & Rastgoo, S. (2023). The effects of L-carnitine supplementation on glycemic markers in adults: A systematic review and dose-response meta-analysis. Frontiers in nutrition, 9, 1082097. https://doi.org/10.3389/fnut.2022.1082097
- Veronese, N., Stubbs, B., Solmi, M., Ajnakina, O., Carvalho, A. F., & Maggi, S. (2018). Acetyl-L-Carnitine Supplementation and the Treatment of Depressive Symptoms: A Systematic Review and Meta-Analysis. Psychosomatic medicine, 80(2). https://doi.org/10.1097/PSY.0000000000000537
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- “L-Carnitine.” Linus Pauling Institute, 23 Apr. 2014, lpi.oregonstate.edu/mic/dietary-factors/L-carnitine#:~:text=Table%201.%20L-Carnitine%20Content%20of%20Selected%20Foods%20. Accessed 5 July 2023.
Garett Reid
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