Cinnamon Supplementation Improves Uric Acid Levels in Adolescents with Obesity: Secondary Metabolic Outcomes from a Randomized Controlled Trial

Background: Serum uric acid (SUA) has emerged as a relevant cardiometabolic and hepatic risk marker in adolescents with obesity. Cinnamon has shown metabolic benefits in adults; however, its effects on SUA and hepatic markers in pediatric populations remain unclear. This study aimed to evaluate the efficacy of cinnamon supplementation on serum uric acid, hepatic enzymes, and lipid profiles in adolescents with obesity. Methods: This is a secondary analysis of a randomized, double-blind, placebo-controlled clinical trial including 93 adolescents (10–18 years) with obesity (BMI ≥ 95th percentile). Participants received either 3 g/day of Cinnamomum verum or a placebo for 16 weeks, alongside lifestyle intervention. Changes in BMI z-score, SUA, alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), and triglycerides were analyzed. Results: The cinnamon group showed a greater reduction in BMI z-score compared to placebo (Δ −0.08 vs. −0.02; p < 0.001). Serum uric acid decreased significantly in the cinnamon group (median change: −0.5 mg/dL [IQR: −1.0 to −0.2]) compared to placebo (−0.1 mg/dL [IQR: −0.4 to 0.2]; p < 0.01). Triglycerides also decreased in the cinnamon group (−18 mg/dL [IQR: −35 to −5]) versus placebo (−5 mg/dL [IQR: −20 to 10]; p < 0.05). Hepatic enzymes (ALT, AST, and GGT) decreased significantly within both groups, without significant differences between groups. In a subgroup of participants with elevated baseline ALT (n = 67), ALT decreased in both groups (placebo: 32.0 to 30.0 U/L, p = 0.004; cinnamon: 33.0 to 26.0 U/L, p = 0.001), with a greater but non-significant reduction in the cinnamon group (Δ −6.0 vs. −2.0 U/L; p = 0.197). Conclusions: Cinnamon supplementation significantly reduced serum uric acid and improved metabolic parameters in adolescents with obesity. These findings suggest that cinnamon may act as an adjunct strategy targeting early cardiometabolic risk markers, particularly uric acid.