Fed, not fasted: is carbohydrate mouth rinsing still ergogenic? A three-level meta-analysis

Carbohydrate (CHO) mouth rinsing improves performance by stimulating oral receptors linked to brain regions involved in motor control and motivation, without requiring digestive processing. Most research has focused on fasting states, but the effects of postprandial CHO mouth rinsing remain inconclusive. This study aims to synthesize existing studies on the impact of postprandial CHO mouth rinsing on exercise and cognitive performance, offering insights for future research and practical recommendations for athletes and coaches.

Six databases (Pubmed, Web of Science, Cochrane Library, Embase, SciELO and SPORTDiscus) were searched up to March 2025 for randomized, placebo-controlled trials in healthy adults who performed exercise or cognitive tasks under fed conditions following CHO mouth rinsing. A three-level random-effects meta-analysis was performed for exercise performance, while narrative synthesis was applied for cognitive outcomes. For exercise performance, moderator and meta-regression analyses examined sex, training status, exercise modality, rinse composition and concentration, rinse duration, timing of food intake and pre-exercise dietary content.

Thirty-five articles met inclusion criteria: two assessed cognitive performance and thirty-three evaluated exercise performance. Overall, CHO mouth rinsing improved cognitive function under fed conditions compared with placebo, though certainty was very low. Meta-analysis showed a small but significant ergogenic effect on exercise performance (Hedges' g = 0.18, 95% CI [0.09, 0.28], p < 0.01). Moderator and meta-regression analyses indicated that CHO mouth rinsing was more effective under fed conditions during aerobic exercise, when using maltodextrin solutions, rinsing for ≤10 s, and following a high-CHO meal.

This systematic review and three-level meta-analysis provides evidence that CHO mouth rinsing is ergogenic under fed conditions, improving both exercise and cognitive performance, though the overall certainty of evidence is low. Practical applications include its potential use as a simple, noninvasive ergogenic aid, particularly when combined with specific exercise modalities and nutritional strategies.