Effect of carnosine or beta-alanine supplementation therapy for prediabetes or type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials.

Background: Carnosine and beta-alanine (β-alanine) have shown potential in the management of chronic conditions, including metabolic disorders. However, their therapeutic efficacy in individuals with type 2 diabetes mellitus (T2DM) and prediabetes remains inconclusive due to heterogeneity in clinical trial results and limited synthesis of human evidence.

Objective: This systematic review and meta-analysis aim to evaluate the effects of carnosine and β-alanine supplementation on patients with prediabetes and T2DM.

Methods: We searched PubMed, Cochrane Library, Web of Science, and Embase from inception to 9 October 2024 for randomized controlled trials that compared carnosine or β-alanine supplementation to placebo in prediabetic and diabetic populations. The quality of evidence was appraised using the Jadad scale, and the risk of bias was assessed using the Cochrane Risk of Bias tool. Data were analyzed using RevMan and Stata, employing fixed-effects models and I-V methods.

Results: Eight trials met the inclusion criteria, totaling 377 participants. Our analysis indicated that supplementation significantly reduced fasting blood glucose (FBG) (SMD: -0.53; 95% CI: -0.75 to -0.31; p < 0.00001) and hemoglobin A1c (HbA1c) levels (SMD:-0.36; 95% CI:-0.59 to -0.12; p = 0.003) compared to placebo. No significant effects were observed on body mass index (BMI), fasting insulin. low-density lipoprotein cholesterol (LDL-c) or high-density lipoprotein cholesterol (HDL-c), but a lowering effect was observed in total cholesterol (TC). Notably, Homeostasis Model Assessment of Beta-cell Function (HOMA-β) values were improved, suggesting enhanced β-cell function, while changes in homeostasis model assessment of insulin resistance (HOMA-IR) did not reach statistical significance.

Conclusions: Carnosine and β-alanine supplementation show potential as adjunct therapies for improving FBG, HbA1c and HOMA-β in prediabetes and T2DM. Further rigorous studies are warranted to establish optimal dosage, treatment duration, and long-term efficacy in clinical practice.