It has been shown that L-Carnitine is required to carry long chain fatty acids from the cytosol to the cell mitochondria in order to generate energy. Hypothetically, high levels of L-Carnitine in the cells may improve lipid transport on mitochondria and may increase the lipid metabolism. The main objective of the present study was to evaluate the effect of L-Carnitine in reducing body fat in Mexican soccer players. Firstly, we determined participants' body composition by bioimpedance. Participants were divided into two groups, one group was given L-Carnitine (3 g/day) and the other group was given placebo for 30 days. The teams had the same workout routine and a balanced and adequate diet. Finally, participants returned to be assessed about their body compositions. Twenty-one players were included, middle aged, weight and height of 20.9 years, 70.4 kg and 175.5 m, respectively. We did not find changes in the percentages of body fat in both groups after the treatments (p>0.05). Data leads us to conclude that supplementation with L-Carnitine for 30 days (3g/day) does not reduce the fat percentage in soccer players.
Currently, there is a great awareness of the benefits of a regular practice regarding physical activity, along with healthy eating habits, which may help prevent or delay manifestation of certain diseases.[1] Several studies have demonstrated that nutritional supplementation such as amino acids, vitamins or proteins may improve health and fitness. L-Carnitine is a quaternary amine, which acts as a cofactor in the transportation of long chain fatty acids to the inner mitochondrial membrane with the purpose of producing energy. It has been shown that L-Carnitine supplementation has potential benefits in cardiovascular diseases, physical performance, chronic fatigue syndrome and Alzheimer’s disease.[2] L-Carnitine seems to be a safe supplement; some researchers recommend consuming from 2 to 5 grams per day.[3] Contraindication of L-Carnitine supplementation only exists when there is hypersensitivity to it. There are no contraindications for pregnancy and lactation, and L-Carnitine has not been reported to be mutagenic, teratogen or to possess drug interactions. There are only adverse reactions when L-Carnitine is given in higher doses (3 to 5 g) to adults. [4]
Due to the capacity of L-Carnitine for increasing lipid metabolism, it is hypothesized that this L-Carnitine-induced action is associated with a decrease of weight and/or a better athletic performance in healthy individuals by various mechanisms such as increased fatty acid oxidation, altered homeostasis glucose, improved production of acyl-Carnitine, and delayed onset of muscle fatigue.[5] The International Federation of Association Football considers L-Carnitine as a supplement which helps increase energy.[6] L-Carnitine is not in the list of substances and methods prohibited by the World Anti-Doping Agency.[7] The International Society of Sports Nutrition (ISSN) classifies L-Carnitine as a supplement which is apparently ineffective and/or dangerous, indicating that the majority of well-controlled studies indicate that L-Carnitine supplementation does not affect muscular content thereof, metabolism of lipids and body weight loss in overweight subjects[8]; however, L-Carnitine has not been evaluated in soccer athletes. Therefore, the main objective of the present study was to determine the effect of the supplementation of L-Carnitine on the body fat percentage in soccer players of a Mexican University.
Sample, Participant Selection and Methodology
It was carried out a single-center, prospective, randomized and double-blinded clinical trial to search the effect of L-Carnitine on the fat percentage of soccer players from a Mexican University. The study was carried out at the Universidad Autónoma del Estado de México. The study protocol was approved by the Ethics and Research Committees from the Universidad del Futbol y Ciencias del Deporte, Hidalgo, Mexico. This study was conducted according to the Declaration of Helsinki.
The Inclusion criterion for this study was: age≥18 years, male gender, soccer players, and individuals who have signed a consent letter. It was carried out a medical history, as well as a diet and supplementation data of the participants and they did not present a history of allergy to any substance of the medication in this study. Participants were excluded if they had any metal prosthesis within the body, also if they require any special diet, and if they had had any medication during the 7 days before starting the project.
All participants had a medical examination carried out by a physician. Weight and height were measured with the participants wearing light clothing and without shoes. BMI was calculated as the weight in kilograms divided into the height in square meters. Bioelectrical Impedance measures were collected using the Inbody 720, Body Composition Analyzer, Biospace Co. Ltd.
After the first clinical evaluation, participants were divided randomly into two groups, one of them received 3 g/day L-Carnitine and the other one was given placebo three times a day for 30 days (all orally). Placebo was similar in appearance to medication, but contained only an inert substance (rice flour). Participants ingested capsules with 12 ounces of bottled water. The capsules were manufactured by Laboratorios Grossman S.A. (Mexico, D.F.), and they were identical in appearance, participants were provided with unlabeled bottles every week. The compliance for the intaking was determined by the capsule counts upon bottle return. Soccer players were instructed to maintain their normal diet during the study period and to complete food records in order to allow a nutrient intake assessment seven days prior to each testing session. Subjects were given specific instructions regarding the recording of portion sizes and quantities, in addition to viewing food models in order to enhance precision. Diet records were analyzed for the total of calories, proteins, carbohydrates, and fats (Food Processor SQL, version 9.9, ESHA Research, Salem, OR). At the end of the supplementation, participants reported back to a final medical examination to determine body composition and adverse reactions to medication.
Statistical analysis
An statistical analysis was carried out using SPSS 16.0 (SPSS Inc., Chicago, IL). Data are shown as the mean ± SEM and frequencies and percentages. Data were evaluated using t student. P < 0.05 was required for significance.
A total of 24 participants was evaluated. 21 out of these participants completed the study and were retained in the analysis; 11 (52.4 %) in the L-Carnitine group and 10 (47.6 %) in the placebo group.
The average age ± standard deviation age in the L-Carnitine group was 20.9 ± 1.9 years and 20.9 ± 2.2 years in the placebo group, which did not represent a significant difference between the two groups (P > 0.05).
The average ± standard deviation height in the L-Carnitine group was 173.5 ± 4.5 cm and 177.8 ± 7.9 cm in the placebo group, which did not represent a significant difference between the groups (P > 0.05). Anthropometric data of the patients of both groups are displayed in Table 1. There were not significant differences in the main anthropometric variables (P>0.05) between the L-Carnitine and placebo groups, neither before (basal) nor after the treatments. In Table 2, we can observe the adverse reactions presented by the players of both groups.
Table 1. Anthropometric data of the patients of both groups.
| L-Carnitine Group n=11 |
Placebo Group n=10 |
|||||
| Basal | Treatment | P value | Basal | Treatment | P value | |
| Weight (kg) | 68.8 ± 4.4 | 69.5 ± 4.0 | 0.71 | 72.1 ± 9.0 | 72.8 ± 9.5 | 0.31 |
| BMI | 22.9 ± 1.2 | 23.1 ± 1.1 | 0.64 | 22.7 ± 1.2 | 22.9 ± 1.3 | 0.72 |
| Visceral fat (cm2) | 26.8 ± 15.1 | 25.4 ± 16.3 | 0.84 | 28.8 ± 21.1 | 28.5 ± 20.2 | 1.00 |
| Total fat (kg) | 9.2 ± 2.6 | 9.0 ± 2.4 | 0.87 | 8.7 ± 2.9 | 8.9 ± 2.7 | 0.90 |
| % fat | 12.4 ± 3.3 | 12.9 ± 3.1 | 0.72 | 11.9 ± 3.2 | 12.1 ± 2.7 | 0.90 |
| Muscle mass (kg) | 34.3 ± 2.3 | 34.8 ± 2.2 | 0.59 | 36.4 ± 4.4 | 36.7 ± 4.6 | 0.90 |
| % muscle | 49.8 ± 2.2 | 50.1 ± 2.0 | 0.79 | 50.6 ± 1.9 | 50.5 ± 1.6 | 0.90 |
BMI: Body Mass Index.
Table 2. Adverse reactions presented by players of both groups.
Adverse reaction |
L-Carnitine Group n (%) |
Placebo Group n (%) |
| Softening of the stool | 9 (81.8 ) | 0 (0.0) |
| Mild diarrhea | 4 (36.4) | 0 (0.0) |
| Mild abdominal pain | 3 (27.3) | 1 (10.0) |
| Mild fatigue | 2 (18.2) | 1 (10.0) |
| Mild muscle weakness | 1 (9.1) | 0 (0.0) |
| Chills | 2 (18.2) | 0 (0.0) |
| Hunger | 1 (9.1) | 1 (10.0) |
There are several techniques used by athletes to lose body mass and to increase performance, including a restricted calorie diet and supplements such as the use of L-Carnitine, the use of stimulants as ephedra and ephedrine, or dehydration in some cases.[2] It has been shown that L-Carnitine is required for the transportation of long chain fatty acids from the cytosol to the cell mitochondria, and for energy generation. Hypothetically, higher levels of Carnitine in the cells improve lipid transport into mitochondria and lipid metabolism as well, and the probable decrease of lipids. In the present study (according to the conditions used in the design and execution of the research) a non-significant decrease in the reduction of body fat in the group which was treated with L-Carnitine was found. This ineffectiveness was probably due to some important facts, which are mentioned:
A. Size of population. Malaguernera et al.[1] evaluated the effects of L-Carnitine in 70 elderly people, which concluded that L-Carnitine reduces the total body fat. In the same sense, in a study by Dragan et al.[9], authors included a population of 40 elite athletes, and an increase in VO2 max was shown. However, Arenas et al.[11] included 24 athletes, as in our study, to prevent the decline in muscular L-Carnitine in their training. Other studies evaluated the effects of L-Carnitine in populations smaller than our population.[11- 14] In particular, we feel that the population size was adequate and it had little influence on the results.
B. Treatment time. Compared with other studies in the literature review, the treatment time used in our study was higher than in other studies, where they have carried out evaluation from a single dose [12, 13, 14,15,16], for 5 days a week[11,[17,18] from 14 to 21 days[9,14, 19,20] and some for 28 days.[21-25] On the other hand, some studies evaluated the effects of L-Carnitine for 1 month.[10] Our study was carried out for 30 days; so we do not believe that the time used in our study is the reason why we did not find a decrease in the percentage of fat in players treated with L-Carnitine.
C. The veracity of reports of food received during this study. In this sense, the best study design includes isolation of athletes and close monitoring, which increases the cost of the study. In our study, we did not realize this kind of isolation and close monitoring of athletes.
D. Lack of compliance of medication. In this sense, it is the major cause of treatment failure. In our study, participants stated they had taken all drugs supplied. We certainly cannot speak of non-compliance.
E. Accuracy that players were not taking any other supplements other than those indicated.
F. Lack of compliance by adverse reaction. Participants reported that adverse reactions were generally mild and they did not abandon their medication.
It is worth mentioning that there are no studies which seek to decrease the percentage of fat in soccer players with L-Carnitine; instead, the studies reviewed in the literature review evaluate changes in VO2Max, L-Carnitine concentration in muscle, changes in lactate, saving muscle glycogen, plasma glucose, heart rate, changes in enzyme activity, etc. A relatively recent study by Klaus et al.[26] found significant differences in fat oxidation (15.8 to 19.3 %) with 3 g/day for 10 days in adult obese. Therefore, it is probable that L-Carnitine may have beneficial effects in people with abnormal weight; and then, L-Carnitine does not produce beneficial effects in individuals with healthy body mass or in sportsmen.
Both groups showed no significant changes in the percentage of fat, which leads us to conclude that supplementation with L-Carnitine does not reduce the percentage of fat in soccer players.
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[a]. Centro de Medicina de la actividad Física y el Deporte, Facultad de Medicina de la Universidad Autónoma del Estado de México, Toluca, Estado de México, Mexico.
[b]. Área Académica de Medicina del Instituto de Ciencias de la Salud, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico
[1] Author to whom correspondence should be addressed:
Shared Alejandro Maldonado-Domínguez1
shared.maldonado@gmail.com