L-carnitine supplementation was explored as an alternative to statins for combating low-density lipoprotein-cholesterol (LDL-C) and chronic heart disease (CHD).
It was noted that L-carnitine supplementation may reduce total cholesterol (TC), triglycerides (TG), and LDL-C levels whilst increasing high-density lipoprotein-cholesterol (HDL-C) levels.
The imbalance in blood lipids (dyslipidaemia) is a significant modifiable risk factor for atherosclerosis and CHD.
Natural compounds, such as L-carnitine, with antioxidant, anti-inflammatory, and lipid-modulating properties, are being explored as potential supplements to prevent and treat chronic diseases.
L-carnitine, found in animal-based foods, plays a vital role in fatty acid metabolism and has potential benefits for lipid profiles and related diseases.
It is necessary for importing long-chain fatty acids (LCFA) into the mitochondrial matrix for beta-oxidation.
Previous meta-analyses have been conducted to investigate the therapeutic effects of L-carnitine on lipid profiles. However, the authors note that this prior research on its effects on lipid profiles has yielded inconsistent results.
Therefore, the new meta-analysis was conducted to provide accurate and conclusive data on L-carnitine supplementation's impact on lipid profiles.
Databases including PubMed, Scopus, Embase, Web of Science, and Google Scholar were searched up to June 2023. Meta-analysis was performed using a random-effects model, with 13 eventually meeting the inclusion criteria.
The included studies were published between 2013 and 2021, and the participants’ average age ranged from 26 to 53. In the studies, L-carnitine administration ranged from 0.54 g/day to 2.4 g/day on average across studies.
Results from the thirteen meta-analyses indicated that L-carnitine supplementation significantly reduced total cholesterol (TC) (ES = −1.05 mg/dL, 95% CI: −1.71, −0.39; p = 0.002), triglycerides (TG) (ES = −2.51 mg/dL; 95% CI: −3.62, −1.39, p < 0.001), and low-density lipoprotein-cholesterol (LDL-C) (ES = −4.81 mg/dL; 95% CI: −6.04, −3.59; p < 0.001).
It also increased high-density lipoprotein-cholesterol (HDL-C) (ES: 0.66 mg/dL, 95% CI: 0.20, 1.12, p = 0.005) levels.
The analysis revealed that L-carnitine supplementation has potential antihyperlipidemic effects, as it reduces TC, TG, and LDL-C levels while improving HDL-C levels.
Several studies suggested that L-carnitine consumption is associated with normalising the blood concentrations of TC, TG, and LDL-C.
The authors suggest the potential mechanisms behind these effects include L-carnitine's role in transporting fatty acids across mitochondrial membranes, enhancing beta-oxidation, reducing free fatty acid availability, and inhibiting cholesterol synthesis.
Additionally, L-carnitine exhibits antioxidant and anti-inflammatory properties, which can further modulate dyslipidaemia and protect LDL from oxidative stress.
Beyond that, L-carnitine can reduce the availability of free fatty acids (FFAs), diminish the conversion of FFAs to TGs, and prevent excess TG accumulation in hepatocytes.
The authors note that L-carnitine also can affect cholesterol synthesis pathway (mevalonate pathway) via inhibition of β-hydroxy β-methylglutaryl (HMG)-CoA reductase activity.
However, they also explain that the effects of L-carnitine on lipid parameters were found to be heterogeneous, likely due to variations in dosage, gender, age, study population, and intervention duration.
They state: “In sum, it seems that the effect of L-carnitine on TG and LDL-C depends on the health condition of individuals, so the patients with metabolic disorders and T2DM have had the most beneficial efficiency of this supplementation.”
They explain that some contradictory results in previous meta-analyses are attributed to differences in participant characteristics, study duration, and L-carnitine supplementation regimens.
The authors recommend considering L-carnitine as a potential lipid-modulating agent, either alone or in combination with other lipid-lowering drugs, based on suggestive evidence.
Journal: Frontiers in Nutrition
“The effect of L-carnitine supplementation on lipid profile in adults: an umbrella meta-analysis on interventional meta-analyses."
Authors: Vali Musazadeh, Hanie Alinejad, Niloofar Kouhi Esfahani, Zeynab Kavyani, Majid Keramati, Neda Roshanravan, Erfan Mosharkesh, and Parvin Dehghan.