The Effects of L-Carnitine Supplementation on Weight Loss, Glycemic Control, and Cardiovascular Risk Factors in Patients With Type 2 Diabetes: A Systematic Review and Dose-response Meta-Analysis of Randomized Controlled Trials.

2024-05
Clinical therapeutics 46(5)
- Amin Mirrafiei
- Ahmad Jayedi
- Sakineh Shab-Bidar

PubMed: 38594107
DOI: 10.1016/j.clinthera.2024.03.002

Study Design

Type: Meta-Analysis
Sample size: n = 2,041
Population: adults with type 2 diabetes
Methods: Systematic review and meta-analysis of randomized controlled trials, searching PubMed/Medline, Scopus, and Web of Science until May 2022; random-effects meta-analysis and nonlinear dose-response modeling

Purpose

L-carnitine supplementation has been recommended to improve cardiometabolic health markers in diabetic patients. Our purpose was to assess the dose-dependent effects of l-carnitine supplementation on cardiometabolic risk factors in patients with type 2 diabetes.

Methods

PubMed/Medline, Scopus, and Web of Science were searched until May 2022 for randomized controlled trials that examined the impact of l-carnitine supplementation on cardiometabolic risk factors in adults with type 2 diabetes. The mean difference (MD) and its 95% confidence interval (CI) were estimated utilizing a random-effects model. Nonlinear dose-response associations were modeled with restricted cubic splines. The certainty of evidence was rated using the GRADE approach.

Findings

Twenty-one randomized trials with 2041 patients with type 2 diabetes were included. We found that every 1 g/d supplementation with l-carnitine significantly reduced body mass index (MD: -0.37 kg/m², 95% CI: -0.59, -0.15; I² =93%, n=13, GRADE=low), HbA_1c (MD: -0.16%, 95% CI: -0.32, -0.01; I² = 94%, n = 18, GRADE = moderate), and low-density lipoprotein cholesterol (MD: -0.11 mmol/L, 95% CI: -0.16, -0.05; I² = 91%, n = 11, GRADE = high). There were also reductions in serum triglycerides (MD: 0.07 mmol/L), total cholesterol (MD: -0.13 mmol/L), and fasting plasma glucose (MD: -0.17 mmol/L). A U-shaped effect was demonstrated for body mass index, with the largest reduction at 2 g/d. A linear reduction was seen for serum triglycerides, total cholesterol, and fasting plasma glucose up to l-carnitine supplementation of 4 g/d.

Implications

L-carnitine supplementation resulted in a small reduction in serum lipids and plasma glucose in patients with type 2 diabetes. However, due to high statistical heterogeneity, the results should be interpreted very cautiously.

Research Insights

L-Carnitine→Improved Fasting Plasma Glucose
fasting plasma glucose (MD: -0.17 mmol/L)
Effect
Neutral
Effect size
Small
Dose
1 g/day
L-Carnitine→Reduced Body Mass Index
every 1 g/d supplementation with l-carnitine significantly reduced body mass index (MD: -0.37 kg/m2, 95% CI: -0.59, -0.15; I2 =93%, n=13, GRADE=low)
Effect
Beneficial
Effect size
Small
Dose
1 g/day
L-Carnitine→Reduced Hemoglobin A1c
HbA1c (MD: -0.16%, 95% CI: -0.32, -0.01; I2 = 94%, n = 18, GRADE = moderate)
Effect
Beneficial
Effect size
Small
Dose
1 g/day
L-Carnitine→Reduced Low-Density Lipoprotein Level
low-density lipoprotein cholesterol (MD: -0.11 mmol/L, 95% CI: -0.16, -0.05; I2 = 91%, n = 11, GRADE = high)
Effect
Beneficial
Effect size
Small
Dose
1 g/day
L-Carnitine→Reduced Serum Triglycerides
There were also reductions in serum triglycerides (MD: 0.07 mmol/L)
Effect
Neutral
Effect size
Small
Dose
1 g/day
L-Carnitine→Reduced Total Cholesterol
total cholesterol (MD: -0.13 mmol/L)
Effect
Neutral
Effect size
Small
Dose
1 g/day