Carbohydrate mouth rinsing has been featured in mainstream media as the new exercise performance-boosting method that athletes worldwide are using. But is the hype supported by the evidence?
What did they test? The authors reviewed and meta-analyzed the current literature to understand whether maltodextrin-based carbohydrate mouth rinsing can positively affect exercise performance.
What did they find? Some evidence suggests that carbohydrate mouth rinsing may provide performance benefits, but their magnitude was relatively small.
What does it mean for you? Although not a replacement for proper pre-workout nutrition, carbohydrate mouth rinsing may be a viable intra-workout alternative to carbohydrate ingestion, especially if the latter leads to gastrointestinal discomfort.
What’s the Problem?
Carbohydrates are almost synonymous with “energy” when thought of in an exercise context. Ingesting carbohydrates before exercise can aid in performance increases, in both strength and endurance-based tasks 1 2. Although the role of carbohydrates for strength outcomes may not be as crucial as for endurance outcomes, carbohydrates can still help with completing more training volume and even potentially recovering better after training 3, making them a very useful macronutrient for anyone interested in becoming fitter and performing better. In previous issues of REPS we’ve looked at whether pre-workout carbohydrates are helpful for resistance training and how eating almost zero carbohydrates, aka being on the Ketogenic diet, affects one’s potential muscle and strength gains. The literature on the overall effect of carbohydrate consumption on exercise performance is relatively clear and points to a thumbs up for daily carbohydrate consumption at different time points during the day (e.g., pre, intra, and post one’s training sessions).
The importance of pre and intra-workout carbohydrate consumption will be different depending on one’s goals and exercise intensity, with those who engage in moderate to high-intensity endurance training being more likely to benefit from paying more attention to their carbohydrate intake structured around their training sessions 4. For casual trainees engaging in both resistance and endurance training, consuming an adequate amount of carbohydrates in the hours leading up to their training session will probably cover them as far as maximizing performance goes 4. However, individuals who are either endurance athletes or perform multiple moderate to high intensity training sessions per day, biasing some of their carbohydrate consumption during the exercise itself may be a viable strategy to maximize their performance with current guidelines recommending that 30-60g of carbohydrate be consumed approximately every hour of endurance exercise.
However, consuming carbohydrates during exercise may lead to gastrointestinal discomfort 5, something that can then harm training performance. An alternative to directly consuming carbohydrates during training is carbohydrate mouth rinsing. Carbohydrate mouth rinsing involves one rinsing their mouth with a carbohydrate-based solution without ingesting it, pretty much like you do with mouthwash. Carbohydrate mouth rinsing has been shown to improve exercise performance in some studies 6, but the totality of the currently available scientific evidence remains somewhat mixed as other studies have shown no benefit of carbohydrate mouth rinsing 7.
The exact mechanisms behind carbohydrate mouth rinsing are still unclear, but some of the current theories revolve around carbohydrate mouth rinsing resulting in greater brain activity in higher brain regions which are responsible for “cognitive, behavioral and emotional response,” essentially activating a pleasure & reward response. Another theory that may explain the potential benefits of carbohydrate mouth rinsing on exercise performance is that it has a positive effect on a “Central Governor” mechanism in our bodies, which is responsible for maintaining homeostasis during exercise and reacts to changes in both the internal and external environment 8. Lastly, the placebo effect of doing “the new unorthodox method that promises performance increases” may also play some role in the effectiveness of carbohydrate mouth rinsing, however, that explanation is somewhat addressed by exploring carbohydrate mouth rinsing in studies with a placebo group present.