“To the best of the researchers' knowledge, this study is the first comprehensive meta-analysis designed to analyse the effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors,” wrote the authors from Ahvaz Jundishapur University of Medical Sciences in Clinical Nutrition.
“Our meta-analysis showed that l-carnitine supplementation could be effective on lipid profile levels, particularly in doses more than 1500 mg/day.
“Additionally, l-carnitine supplementation can improve glycaemic control, particularly along with hypocaloric diet.”
L-Carnitine, a vitamin-like nutrient, occurs naturally in the human body and is essential for turning fat into energy. It is frequently used as a dietary supplement by physically active people to help with post-exercise recovery.
The potential health conditions of the ingredient include cardiovascular benefits, weight management potential, sports nutrition (energy and recover), and maintaining levels during pregnancy.
The new meta-analysis pooled data from 24 randomized clinical trials. The majority of the trials were conducted in Italy, but other trials were performed in Mexico, Lebanon, Korea, Iran, Greece, China, and Taiwan.
Doses used in the trials ranged from 500 mg per day to 4,000 mg per day, and the trials lasted between 4 and 48 weeks.
The pooled data indicated that L-carnitine supplementation was associated with significant improvements in total cholesterol (average reduction of 14 mg/dL), LDL-cholesterol (average reduction of 7.7 mg/dL), and HDL-cholesterol (average increase of 0.8 mg/dL).
In addition, measures of glycemic control, including fasting blood glucose, HbA1C, and HOMA-IR also significantly improved as a result of L-carnitine supplementation. However, the blood glucose improvements were only observed in trials that lasted longer than 12 weeks.
No improvements were recorded for triglyceride levels, or for Apo A-I and Apo B 100.
“There are several mechanisms for the effectiveness of l-carnitine supplementation in improving lipid profile,” stated the researchers. “In effect, l -carnitine attaches to fatty acyl-CoA to produce acyl-carnitine. Acyl-carnitine could be transported into the mitochondrial matrix for beta-oxidation to produce adenosine triphosphate (ATP).
“In addition, l-carnitine influences fatty acid and carbohydrate metabolism by boosting non-oxidative glucose disposal.
“The leakage of insulin increases lipolysis in the adipose tissue, augments fatty acid oxidation, fosters the formation of acyl-carnitine esters and also increases the discharging storage of free l-carnitine. Therefore, l-carnitine supplementation can fill this gap and improve glycemic and lipid profile in patients with Type 2 DM and insulin resistance.”
Source: Clinical Nutrition
January 2020, Volume 39, Issue 1, Pages 110-122, doi: 10.1016/j.clnu.2019.01.020
“The effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled clinical trials”
Authors: M. Asadi et al.