The bright and the dark sides of L-carnitine supplementation: a systematic review.
- 2020-01-03
- Journal of the International Society of Sports Nutrition 17(1)
- Angelika K Sawicka
- Gianluca Renzi
- Robert A Olek
- PubMed: 32958033
- DOI: 10.1186/s12970-020-00377-2
Study Design
- Type
- Systematic Review
- Sample size
- n = 11
- Population
- healthy human subjects
- Methods
- Systematic review of studies on healthy human subjects treated with oral L-carnitine for at least 12 weeks
- Duration
- 12 or 24 weeks
Background
L-carnitine (LC) is used as a supplement by recreationally-active, competitive and highly trained athletes. This systematic review aims to evaluate the effect of prolonged LC supplementation on metabolism and metabolic modifications.Methods
A literature search was conducted in the MEDLINE (via PubMed) and Web of Science databases from the inception up February 2020. Eligibility criteria included studies on healthy human subjects, treated for at least 12 weeks with LC administered orally, with no drugs or any other multi-ingredient supplements co-ingestion.Results
The initial search retrieved 1024 articles, and a total of 11 studies were finally included after applying inclusion and exclusion criteria. All the selected studies were conducted with healthy human subjects, with supplemented dose ranging from 1 g to 4 g per day for either 12 or 24 weeks. LC supplementation, in combination with carbohydrates (CHO) effectively elevated total carnitine content in skeletal muscle. Twenty-four-weeks of LC supplementation did not affect muscle strength in healthy aged women, but significantly increased muscle mass, improved physical effort tolerance and cognitive function in centenarians. LC supplementation was also noted to induce an increase of fasting plasma trimethylamine-N-oxide (TMAO) levels, which was not associated with modification of determined inflammatory nor oxidative stress markers.Conclusion
Prolonged LC supplementation in specific conditions may affect physical performance. On the other hand, LC supplementation elevates fasting plasma TMAO, compound supposed to be pro-atherogenic. Therefore, additional studies focusing on long-term supplementation and its longitudinal effect on the cardiovascular system are needed.Research Insights
significantly increased muscle mass, improved physical effort tolerance and cognitive function in centenarians.
- Effect
- Beneficial
- Effect size
- Moderate
- Dose
- 1 g to 4 g per day for either 12 or 24 weeks
Twenty-four-weeks of LC supplementation did not affect muscle strength in healthy aged women
- Effect
- Neutral
- Effect size
- Small
- Dose
- 1 g to 4 g per day for either 12 or 24 weeks
significantly increased muscle mass, improved physical effort tolerance and cognitive function in centenarians.
- Effect
- Beneficial
- Effect size
- Moderate
- Dose
- 1 g to 4 g per day for either 12 or 24 weeks
LC supplementation, in combination with carbohydrates (CHO) effectively elevated total carnitine content in skeletal muscle.
- Effect
- Beneficial
- Effect size
- Moderate
- Dose
- 1 g to 4 g per day for either 12 or 24 weeks
significantly increased muscle mass, improved physical effort tolerance and cognitive function in centenarians.
- Effect
- Beneficial
- Effect size
- Moderate
- Dose
- 1 g to 4 g per day for either 12 or 24 weeks
LC supplementation was also noted to induce an increase of fasting plasma trimethylamine-N-oxide (TMAO) levels, which was not associated with modification of determined inflammatory nor oxidative stress markers.
- Effect
- Harmful
- Effect size
- Small
- Dose
- 1 g to 4 g per day for either 12 or 24 weeks