In sports nutrition, L-Carnitine is considered one of the most controversial supplements. Advertising slogans emphasize its amazing properties as a fat burner, which “all fitness enthusiasts use for weight loss,” while sports nutrition sellers add benefits for muscle gain, increased energy, and endurance; some even talk about the ability of carnitine to improve sexual function.
The internet is filled with enthusiastic reviews of its effectiveness for weight loss…
And only skeptical scientists critically examine almost all the listed properties of L-Carnitine.
In this material, we will introduce you to what L-Carnitine is and what it is needed for in sports and medicine, we will analyze its properties, look at what and for whom its deficiency in the diet is dangerous, and whether athletes are at risk of deficiency.
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What is L-Carnitine?
L-Carnitine appeared on the sports nutrition market as a weight loss supplement in the 1980s. It was then overshadowed by significantly more effective fat burners of the next generation containing stimulants, hormones, and anabolic steroids.
In our time, as one of the authors of bodybuilding.com puts it, “… there has been a kind of resurrection of L-Carnitine… it has returned and become stronger than ever; only now not just as a fat burner, but also as a supplement that increases physical performance and aids recovery…“
Let’s take a look at what lies behind these elevated words.
L-carnitine is a natural substance that plays an important role in human metabolism.
In sports, L-carnitine refers to a type of sports nutrition that is used as a fat burner for weight loss, as well as a supplement to stimulate muscle growth and energy.
Carnitine is present in almost every cell of the body. Its name comes from the Latin carnus (“flesh”), as it was first obtained from animal meat. It is found in high concentrations in muscles (including the heart), the brain, and even in sperm.
In its properties, it resembles both vitamins (primarily those of group B) and amino acids, as it is equally important for the body. Back in the 1950s, scientists referred to it as “vitamin BT,” highlighting its important role.
However, it is not a vitamin or mineral, which, by definition, must be obtained from food to avoid deficiency states and related disorders or diseases.
– What is the role of L-carnitine in the body?
L-carnitine plays a critically important role in energy production from fats in the body. It does this by transporting fat into the cells, into the mitochondria, which act as mini-engines: burning fats and providing energy output 5,7,20. This is where the popularity of L-carnitine as a fat-burning supplement originates.
Carnitine can be synthesized in the body from two essential amino acids, lysine and methionine 2. For this, a sufficient amount of vitamin C 21 is necessary.
In small amounts, L-carnitine is obtained from animal-derived foods (fish and meat) 22.
Vegans, some types of vegetarians, and people with certain genetic disorders are at risk of deficiency, as their bodies either do not produce carnitine at all or produce it in very small amounts.
For this reason, L-carnitine is sometimes referred to as a “conditionally essential” nutrient 4.
L-carnitine is a natural substance that performs important metabolic functions in the body; in sports, it is a type of sports nutrition used for weight loss, muscle growth, and energy.
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Forms of L-carnitine in sports nutrition
“L-Carnitine” is a general term for the three forms in which it is available on the market. Different forms of L-carnitine are used for different purposes and contain varying amounts of the active substance:
- acetyl-L-carnitine – for improving brain function;
- L-carnitine L-tartrate – as a sports supplement to improve efficiency and power;
- Glycine-Propionyl-L-carnitine – to enhance cardiovascular system performance.
Acetyl-carnitine is often falsely marketed and taken as an energy stimulant, but its known effect is significantly less than that of other stimulants, such as caffeine.
The acetyl group attached to the carnitine molecule increases its ability to penetrate the brain, where it acts as a powerful antioxidant, plays an important role in energy production, and is also involved in the creation of an important neurotransmitter (a substance used for transmitting nerve impulses). This is why acetyl-L-carnitine is beneficial in protecting against aging processes and nerve cell damage.
Different forms of carnitine contain varying amounts of the active substance. Equivalent doses are as follows:
(630-2500 mg of acetyl-carnitine) = (1000-4000 mg of L-carnitine L-tartrate) = (1000-4000 mg of Glycine Propionyl L-carnitine).
What foods contain L-carnitine
Sources of carnitine that enter the body are primarily animal products.
It is found in large amounts in meat (the redder the meat, the more), in smaller amounts in milk (mainly in whey) 1, and in significantly smaller amounts in plant products, such as avocados and soybeans. Carnitine is a component of human breast milk.
Animal products contain significantly more carnitine than plant products. And the redder the meat, the higher its concentration.
The National Institutes of Health in the USA recommends the following carnitine-rich foods 16:
| Carnitine in food | ||
|---|---|---|
| Product | Serving | Carnitine content, mg |
| Beef (lean), cooked | 1 serving (112 g) | 56-162 |
| Ground beef, cooked | 1 serving (112 g) | 87-99 |
| Whole milk | 1 cup | 8 |
| Cod, cooked | 1 serving (112 g) | 3-5 |
| Chicken breast, cooked | 1 serving (112 g) | 3-5 |
| Ice cream | 1/2 cup | 3 |
| Cheddar cheese | 1 serving (56 g) | 2 |
| Whole grain bread | 2 slices | 0.2 |
| Asparagus, cooked | 1/2 cup | 0.1 |
Carnitine from natural products is better absorbed: by 57-84%, while in supplement form – only by 14-18% 3. The dose size likely matters: at smaller doses, absorption is more complete.
On average, non-vegetarians consume about 2-12 mcg of carnitine per kilogram of body weight per day, while vegetarians consume significantly less 4,5. For an omnivorous person weighing ~100 kg, this amounts to approximately 1 mg daily.
The dose of carnitine in special supplements is thousands of times higher: 1-4 grams. At such dosages, even with low absorption, the body retains about 250-500 mg, which is significantly more than from meat products.
Carnitine from natural products is absorbed significantly better than from supplements; however, the concentration in supplements is 1000 times higher.
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What is L-carnitine used for? Useful properties of carnitine
Carnitine is involved in a large number of functions in the body, which explains its necessity.
Sales websites and research portals slightly differ in describing its roles and benefits for the body. Overall, the general picture of the beneficial properties of L-carnitine looks as follows:
- Fat burning (theoretically)
For scientists and researchers, unlike athletes and sellers, it is more typical to speak only of the theoretical ability of L-carnitine to enhance fat burning.
Important: Numerous studies on the fat-burning effect are very controversial and generally refute it (see our study on the benefits of L-carnitine for weight loss).
Most often, the fat-burning effect is explained by scientists as an increase in physical activity due to obtaining a greater amount of calories from carnitine supplements.
Theoretically, carnitine should be a good fat burner, but studies do not confirm this; most often, the possible fat-burning effect is explained by a simple increase in calories in the diet due to carnitine supplements.
- Elimination of toxic compounds
This refers to the byproducts of fat burning; L-carnitine prevents their accumulation in the body.
- Stimulation of brain activity
Carnitine can increase alertness and mitochondrial potential, ensuring better functioning of neurons.
- Mitigation of the side effects of aging
- Combatting depression and chronic fatigue
- Improvement of sexual health
- Improvement of vascular health
- Protection of nerve cells and their recovery after damage due to diabetes and diabetic neuropathy
- Enhancement of athletic performance
It refers to the influence of L-carnitine consumption on increasing endurance and reducing fatigue.
Scientific studies do not support this. See our research on the benefits of L-carnitine for increasing endurance and gaining muscle mass.
- Benefits for gaining muscle mass
Scientific studies do not confirm the effectiveness of L-carnitine as a supplement for gaining muscle mass and increasing muscle strength. See our research on the benefits of L-carnitine for increasing endurance and gaining muscle mass.
L-carnitine deficiency
L-carnitine deficiency can occur when there is insufficient intake from food in certain categories of people or when the mechanism of its absorption and synthesis in the body is impaired.
1 Veganism and vegetarianism
The first to fall into the risk category are vegetarians and vegans, as their diet does not contain animal products 5 rich in carnitine. They can be recommended additional intake of carnitine in the form of supplements. Studies indicate that when carnitine enters their bodies, it is absorbed very efficiently 5, but is poorly transported to the muscles 6.
Overall, despite the obviousness of the problem, there is very little research on the benefits of additional carnitine intake for vegetarians.
Vegetarians and vegans are at risk of carnitine deficiency due to the absence of animal products in their diet
2 Athletes
As for athletes, according to some scientists, they are not at risk of carnitine deficiency and do not need additional intake 17.
Athletes are not at risk of carnitine deficiency and do not need additional intake
A lack of carnitine is especially dangerous for the heart muscle due to its high energy demands.
3 Medications and carnitine deficiency
Some medications can lead to a decrease in carnitine levels. For example, the heart medication Mildronate reduces carnitine levels by 18% by the fourth week of intake and may contribute to the development of its deficiency 6.
4 Diseases associated with carnitine deficiency
Chronic deficiency of L-carnitine can lead to the following conditions:
- dementia 8
- muscle weakness and liver dysfunction 9
- cardiomyopathy (disease of the heart muscle) 10
- hypoglycemia (lack of glucose in the blood)
Increased doses of carnitine are used to treat these and other diseases.
Carnitine deficiency can be observed in certain cancers, which is why it is being studied as an adjunct treatment for cancer.
In one study, a gradual increase in doses of carnitine (0.5 g over 2 days, 1 g over 2 days, 2 g over 10 days) taken by patients with progressive cancer and carnitine deficiency led to a reduction in feelings of fatigue, improved overall well-being, and decreased levels of functional impairments related to cancer.
There was also a significant increase in muscle mass and appetite observed. For this category, doses up to 3000 mg per day have been shown to be safe 11-15.
Conclusion
The most common answer to the question of what L-carnitine is and what it is needed for is that it is a fat burner. However, scientific studies do not confirm its effectiveness for weight loss.
Most studies demonstrate the beneficial properties of L-carnitine as a supplement for improving brain, heart, and vascular health.
Athletes are not at risk of carnitine deficiency and do not need additional intake. But even when they do, athletic performance does not significantly improve.
The intake of L-carnitine as a supplement may be recommended for elderly people and vegans/vegetarians, as well as in certain diseases.
Of all forms, acetyl-L-carnitine and L-carnitine are the most popular and effective.
