Background: Alginate is a plant-derived polysaccharide used in sport nutrition for its gel-forming properties. Alginate- and pectin-based carbohydrate hydrogels aim to optimize carbohydrate delivery during endurance exercise by modulating gastric emptying and intestinal absorption. However, evidence on their effects on metabolism, gastrointestinal (GI) tolerance, recovery, and performance remains inconsistent. Objective: To systematically evaluate the effects of alginate-based carbohydrate hydrogels on metabolic responses, GI tolerance, recovery, and endurance performance in humans. Methods: PubMed, Scopus, Web of Science, SPORTDiscus, and Google Scholar were searched for randomized controlled trials (2000-2025) comparing alginate- or alginate-pectin-based hydrogels with non-hydrogel carbohydrate or placebo during =60-min endurance exercise. Outcomes on metabolism, GI symptoms, recovery, and performance were qualitatively synthesized and visualized via an evidence heatmap. Results: Nine trials met inclusion criteria. Hydrogels generally enhanced metabolic indicators such as exogenous carbohydrate oxidation, particularly at high ingestion rates. GI tolerance was similar to traditional solutions, with fewer symptoms reported under high-carbohydrate conditions. Performance effects were inconsistent-minor improvements occurred mainly in running, with limited or null effects in cycling and skiing. Preliminary evidence indicates potential attenuation of muscle damage markers and preserved post-exercise amino acid availability. Conclusion: Alginate-based hydrogels appear to modulate carbohydrate metabolism without consistently improving endurance performance. Their efficacy depends on exercise type, carbohydrate dose, and athlete training status. Further well-controlled trials are needed to define their role in supporting performance and recovery.
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