The impact of sports supplements on metabolism, glycemic control, and lipid profile in adolescents and young adults: a narrative review.

INTRODUCTION: Glucose and lipid metabolism are tightly regulated by hormonal signaling, nutrition, and physical activity. Adolescence and young adulthood represent critical developmental periods characterized by puberty-related hormonal shifts and fluctuating insulin sensitivity. At the same time, sports supplement use has increased markedly in these age groups. AIM OF THE RESEARCH: This narrative review examined regulatory mechanisms of glucose and lipid metabolism and evaluated the available evidence regarding the metabolic effects of commonly used sports supplements in adolescents and young adults, considering baseline metabolic status such as obesity, insulin resistance, and diabetes. Relevant findings from adult populations were considered when youth-specific data were limited. MATERIAL AND METHODS: A literature search of PubMed/MEDLINE and Scopus was conducted for studies published up to 2025. Eligible publications included randomized controlled trials, observational studies, systematic reviews, meta-analyses, and experimental research. Supplements of interest were creatine, carnitine, citrulline, taurine, caffeine, branched-chain amino acids (BCAAs), whey protein, arginine, and -alanine. RESULTS: Taurine, carnitine, and citrulline were associated with modest improvements in fasting glucose, insulin resistance, triglycerides, and non-high-density lipoprotein cholesterol, particularly in individuals with obesity or insulin resistance. Creatine appeared metabolically neutral or mildly beneficial when combined with exercise. Elevated BCAA levels were associated with impaired insulin sensitivity. Whey protein showed short-term insulinotropic effects without clear long-term benefits. Caffeine induced transient, dose-dependent reductions in insulin sensitivity. Arginine and -alanine had minimal metabolic impact. Regular physical activity remained the most consistent modulator of glucose and lipid metabolism. CONCLUSIONS: Sports supplements exert heterogeneous metabolic effects in youth. While selected supplements may provide modest benefits in specific populations, regular physical activity remains fundamental for metabolic regulation. Professional supervision and cautious use are recommended.