What is L-Carnitine?
Carnitine is found in abundance in nearly every cell in our body. It is naturally produced (in the liver and kidney) by amino acids, but we can also ingest it from foods.
About 98% of carnitine stores are contained in skeletal muscle, along with trace amounts in your liver and blood.
(SNAP). There are many natural dietary sources of carnitine, with the highest found in red meat, additional sources include green vegetables, dairy products, chicken, fish, egg yolks, beans, and avocado.
In the body, carnitine plays a critical role in energy production. It transports long-chain fatty acids into the mitochondria so they can be burned to produce energy - carnitine is a major component of cellular fat burning in the body, so various supplements have become popular among fitness gurus and athletes.
For most people, natural carnitine production in the body is sufficient to meet our biological needs.
There are some medical conditions, such as preterm infants, where-by the body cannot make enough, so for them, carnitine is a conditionally essential nutrient and requires supplementation.
Are carnitine and L-carnitine the same thing?
Carnitine is a broad term that describes a few different compounds, with l-carnitine being a common form found in dietary supplements.
Carnitine on its own is confusingly referred to as an amino acid, when in truth - it is produced in the body by lysine and methionine (both amino acids).
What does the L stand for in L-carnitine?
L-carnitine, also known as levocarnitine, the L in front indicates levorotary or ‘left side’ or left form, as opposed to the dextrorotary, which represents the ‘right side’ or right form.
Amino acids are more commonly represented by the L form.
Dietary supplemental forms of carnitine are commonly L-carnitine, acetyl-L-carnitine, propionyl-L-carnitine, and L-carnitine tartrate, each with varied actions on the body.
What forms do supplements come in?
Dietary supplements contain either singular form or combined l-carnitine forms and are now available in powder, capsules, tablets, and even gummies.
It is important to understand the varied role of each form when looking to begin supplementation and choose products that are free from fillers and sugar.
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What does L-carnitine L-tartrate supplementation do?
L-carnitine intake is popular among recreationally active, competitive, and highly trained athletes, due to its promising capacity to help recover after extreme workouts.
The International Olympic Committee has approved l-carnitine administration for its use as an ergogenic supplement because it causes little to no side effects.
(SNAP). Given its pivotal role in energy metabolism, l-carnitine intake has been investigated for its potential to enhance physical exercise performance, stamina, and exercise recovery in healthy active people.
Supplementation is postulated to spare glycogen, via increased fat burning, and to promote more efficient carbohydrate burning. (SNAP).
However, it has strong antioxidant properties and thus has brain-supportive health benefits and can be considered as part of an antioxidant treatment plan. (SNAP)
What does L-carnitine L-tartrate supplementation do?
While l-carnitine therapy has been studied in randomized, double-blind placebo-controlled trials for its role in physical exercise-induced muscle recovery and antioxidant action.
L-carnitine tartrate has the potential to impact fatty acid metabolism and weight in obese people.
In one clinical trial, researchers examined the effects of 14 days of L-carnitine L-tartrate oral supplementation (3 grams daily) in non-diabetic obese adult males.
Results showed a significant difference between groups for body mass, fat percentage, and body mass index after supplementation. (SNAP).
Who is taking oral L-carnitine supplements?
L-Carnitines' primary beneficial effects have been associated with athletic performance in patients (active healthy people) - see studies below.
It’s reported that there is a significant decrease in both plasma and muscle levels of carnitine during high-intensity exercises, ensuring adequate l-carnitine intake is important.
Supplementing can help maintain optimal levels and decrease the chances of muscle carnitine deficiency.
Some researchers suggest that oral L-carnitine administration should be considered to greatly reduce the potential effects of this decrease and help retain muscle and blood carnitine levels. (SNAP).
However, other demographics have been studied for its health potential.
- In one randomized double-blind, placebo-controlled study on the endurance performance of patients (12 footballers), researchers examined l-carnitine supplementation at doses of 3 and 4 grams 1 hour prior to performing a running test.
The result showed that the running speeds corresponding to specific l-carnitine concentrations were increased, and heart rate responses to the running speeds were decreased in carnitine versus placebo groups.
No adverse effects were reported (SNAP).
- There is evidence to support oral l-carnitine supplementation in elderly patients.
A systemic review published in the Journal of the International Society of Sports Nutrition titled: The bright and the dark sides of L-carnitine supplementation. (2020).
Sawicka et al, concluded that prolonged supplementation may positively impact physical performance in patients (elderly subjects). (SNAP). Further clinical trials in older adults have shown the potential that l-carnitine supplementation can lead to increased muscle mass accompanied by a decrease in body weight and reduced physical and mental fatigue.
(SNAP). There are some positive results from clinical trials investigating the role of l-carnitine supplementation in elderly patients as an antioxidant for brain support to protect against age-related degeneration.
Combined L-carnitine treatment may be considered as adjunctive therapy to support healthy aging for elderly subjects.(SNAP)
- Another demographic where l-carnitine supplements have become popular is obese subjects, with a growing number of animal studies providing promising beneficial effects of l-carnitine supplements to assist with the reduction of muscle degradation and help with weight loss.
In a recent animal meta-analysis, one study showed body weight was significantly reduced in obese subjects who received l-carnitine compared with the control groups. (SNAP).
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Does l-carnitine supplementation also help with exercise recovery?
Clinical studies in healthy athletes show a positive impact of dietary l-carnitine supplementation on physical performance and the recovery process after exercise.
The studies demonstrated that l-carnitine alleviates muscle injury and muscle soreness.
Supplementing with carnitine may be suggested to promote healthy blood flow and oxygen supply to the muscle tissue, promote recovery post-exercise, and decrease the chance of muscle carnitine deficiency. (SNAP)
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Does l-carnitine help to improve muscle strength?
There is no conclusive evidence to show that l-carnitine supplementation improves muscle mass or strength.
One randomized, double-blind, placebo-controlled trial supplementing with l-carnitine for twenty-four weeks alone did not affect muscle strength in healthy aged women but
seems to improve muscle mass in elderly patients aged between 90-and 100 years old, as well as help to improve mental fatigue. (SNAP)(SNAP)
What are recommended intakes for carnitine according to Clinical Practice Guidelines?
Supplementation may not be always the best choice, according to one clinical study, 57–84% of L-carnitine is absorbed when it’s consumed from food, compared to only 14–18% when taken as a supplement (SNAP).
However, for people who have systemic carnitine deficiency, or are undertaking high-intensity exercise and looking to improve physical performance where carnitine stores are shown to be depleted.
Supplementing would help maintain optimal stores and decrease muscle carnitine deficiency.
The standard daily oral dose of L-carnitine therapy is 500–2,000 mg per day. L-carnitine L-tartrate oral doses are between 1,000–4,000 mg per day.
For oral supplementation, L-carnitine is likely safe when taken for up to 12 months. (SNAP).
There have been reports of adverse effects such as nausea, diarrhea, and abdominal cramping. And, rarer side effects include muscle weakness in uremic patients and seizures in those with seizure disorders. (SNAP)
When can a carnitine deficiency occur?
These can be identified as primary carnitine deficiency - associated with a congenital disease or secondary carnitine deficiency. Secondary carnitine deficiency is more common and is associated with help problems such as:
- Liver disease
- End-stage renal disease
- A digestive disease that causes poor absorption
- Malnutrition
- Mitochondrial disease
- Certain metabolic disorders
- Certain medicines, such as valproate
L-carnitine in review
There are both animal studies and well-organized (randomized double-blind placebo-controlled trial) in human subjects investigating the role of l-carnitine treatment for exercise improvement, physical performance, and recovery with promising results.
Beneficial acute effects of l-carnitine supplementation were observed after oral administration as little as one hour before exercise, and clinical practice guidelines have reported that l-carnitine supplementation is likely safe for up to 12 months.
Researchers detail the benefit of elderly patients and older adults for its role in free radical scavenging, brain support, and as part of an antioxidant treatment plan.
The primary evidence supports the role of l-carnitine supplements for athletes involved in high-performance regular exercise, supplementation of up to 3 and 4 grams has shown to help improve running speed and athletic performance and may help with muscle recovery due to reduction of muscle carnitine deficiency.
These higher doses above 3 grams however have been associated with adverse events in some people. While some diseases and health challenges have shown to be linked to systemic carnitine deficiency, you should speak to your health care provider before undergoing l-carnitine treatment to ensure you are taking the correct form of carnitine, and, to establish the correct dose that's right for you.
For average people with a varied diet, getting adequate dietary carnitine intake may be sufficient to keep muscle carnitine levels healthy.
For physically active people, older people, and high-performance athletes, daily supplementation of l-carnitine or l-carnitine tartrate may help with muscle recovery and exercise performance.
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Amanda Lovett-Jones is an Australian Naturopath, registered Herbalist, and culinary medicine specialist. She is a freelance copywriter and compliance specialist within the dietary supplement industry. She owns a virtual natural therapies wellness clinic that targets and treats inflammation. She lives with her family in Seattle.
