L-Carnitine for recovery , The evolution of a weight loss supplement
Carnitine is not just popular, but is the most popular and well-known dietary supplement for burning fat. 10-15 years ago, everyone seemed to be using L-carnitine for weight loss. And this continues to be the case. Carnitine itself has several forms, the most famous being the base form, L-carnitine-L-tartrate and acetyl L-carnitine. In most studies, scientists simply use the name carnitine, but very often it matters what form it is used. For example, the acetyl form is used as a means to improve memory and cognitive functions due to the ability to cross the blood-brain barrier. These are additional features that other forms do not have and are not related to fat burning.
It is possible that L-carnitine has other functions, but this time focused on muscle recovery and performance. It is these properties that are the subject of a large study (meta-analysis) published in 2020. This study found that post-workout carnitine intake reduced some markers of muscle damage such as creatine kinase, myoglobin and lactate dihydrogenase within 24, 48, 72 and 96 hours after physical training. The results are more noticeable in inexperienced individuals. Eric Trexler of MASS is trying to replicate this study with his own tests, and his results are more than interesting.
L-carnitine has always been associated with fat burning and more aerobic endurance. However, the supplement can have a number of benefits for muscle recovery after intense training.
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What is research? L-Carnitine for recovery
In 2020, a meta-analysis was conducted that observed the effect of L-carnitine on muscle fatigue and markers of muscle damage. The meta-analysis included 7 studies and a total of 79 participants, 70 of whom were men. 34 of the participants are non-training people and the other 45 participants have training experience. The age of the participants varies from 22 years to 59 years. According to the generally accepted calculation methods, 4 of the surveys are of high quality and 3 are of low quality.
Scientists include studies that meet the following criteria:
- Double-blind with random selection;
- To observe at least one of the desired results;
- Have measurements at the beginning of the tests and 24-72 hours after that;
- To include individuals in good health.
The main desired result is the state of muscle fatigue. The authors also perform additional tests, comparing the effect of:
- Carnitine and L-carnitine-L-tartrate;
- Trained against non-coaches;
- Aerobic and anaerobic training.
What is established?
Intake of L-carnitine successfully affects most markers of muscle damage. In the following table, the BB-Team Store team described in detail the results for several markers
| 0 hours | 24 hours | 48 hours | 72 hours | 96 hours | |
| Muscle fatigue | Decrease | Decrease | Decrease | Decrease | Decrease |
| Creatine kinase | Unchanged | Decrease | Unchanged | Unchanged | Unchanged |
| Myoglobin | Unchanged | Decrease | Unchanged | Unchanged | Unchanged |
| Lactate dihydrogenase | Unchanged | Decrease | Unchanged | Unchanged | Unchanged |
The researchers also compared the results in the analysis of the subgroups, finding the following:
- The results are better in individuals without training experience;
- The results are better when training with resistance (strength);
- There are no differences between the efficacy of L-carnitine and L-carnitine-L-tartrate.
How to interpret the results? L-Carnitine for recovery
Most of the research in the meta-analysis is from the last 20 years, but it is a little known fact that there is literature from the 90’s that contains data on the effect of carnitine on muscle recovery. This topic is not new to science. Current data do suggest that carnitine may reduce muscle fatigue and creatine kinase levels after strength training. However, the results in the considered meta-analysis overestimate the results and the statistical significance of the changes in the individual time tests.
If we compare the results to practical conditions, it seems that carnitine reduces muscle fatigue in the first 48 hours after training. However, the magnitude of the effect is about 1-1.5 on a scale of 10. So, if you rated your pain from 0 to 10, carnitine would lower the rating by 1-1.5 points (for example, from 8 to 6.5 or 7), but up to 72 hours after training, the effect is negligible. Changes in creatine kinase confirm these results, while changes in other markers are rather insignificant.
These results can be easily explained. Our current understanding of muscle damage and delayed onset of muscle soreness suggests that in addition to the initial mechanical damage from exercise, there are contributing factors and subsequent responses, including oxidative stress, inflammation, and local hypoxia. In one study, for example, hypoxic conditions were found to lead to the release of carnitine from endothelial cells, increased oxidative stress, and impaired blood flow.
Some evidence even confirms that carnitine can affect nitric oxide and its metabolites, improve vasodilation, and have an antioxidant effect. Most likely, this is one of the main mechanisms of action that directly affects muscle damage.
Carnitine reduces muscle damage not only through its effect on some biomarkers, but also due to additional properties such as the effect on nitric oxide, improved vasodilation and antioxidant effect.
Despite the direct benefits of muscle fatigue, this does not mean that carnitine will successfully affect athletic performance. The results of the research so far are mixed, but the general opinion is that carnitine is not an effective supplement for strength and endurance. There is a theory that while carnitine does not support rapid training adaptation, its anti-fatigue properties may contribute to long-term adaptation to special training protocols over long periods of time. The evidence is still modest and more research is needed. So far, the tests are no longer than 8 weeks and use modest doses of 2-3 grams of carnitine per day.
The big picture L-Carnitine for recovery
Overall, carnitine has been one of the most controversial supplements for nearly two decades. And this applies not only to the topic under consideration at the moment, but also to the properties of carnitine for burning fat and improving endurance. Especially the second one has long been rejected. Carnitine has properties that can make it a suitable tool for counteracting muscle fatigue and this is due to two main mechanisms:
- Reduction of markers such as creatine kinase, myoglobin and lactate dihydrogenase;
- Regulation of nitric oxide and antioxidant effect.
Carnitine can improve strength and endurance, but that’s just a theory. It can happen with training programs with long-term effect (over 3 months). A typical example is the 5/3/1 scheme. Carnitine as a dietary supplement is controversial because of its nature. The substance is vitamin-like and is used for health purposes. It was in a study of the effect of carnitine on blood sugar and insulin that it was found that the substance acts 5 to 7 times more strongly in subjects from Eastern Europe. This means that the genotype can have a decisive effect.
Another factor is the low bioactivity of the substance as a dietary supplement. 2 grams of L-carnitine is characterized by 9-25% digestibility. Carnitine from food has 54-86% digestibility. Last but not least, carnitine may have a stronger effect in non-trainers or vegetarians / vegans. The main reason for this is that these groups consume less meat and fish (main sources). In these cases, the benefits of carnitine may not be due to an improvement in normal function, but rather to a positive change in dysfunction.
At this stage, the team of StayFitLonger still can not recommend carnitine as a basic nutritional supplement for recovery in strength training. More and more specific research on the topic is needed.
Despite promising initial and limited results, more research is needed to find a more specific link between carnitine intake, muscle recovery, and potential benefits in athletic performance. Carnitine may have a stronger effect on inexperienced people or vegans who have a harder time getting it from food.
L-Carnitine for recovery
