Meet: carb rinsing. Here's what you need to know

By Lauren Mazzo
July 13, 2018
Photo: zoff/Shutterstock

If you've been tuning into the World Cup, you may have seen many of the world's best soccer players swishing and spitting all over the field. What gives?!

While it might seem like a total bro thing, it's actually a legit, science-backed performance trick called "carb rinsing" which involves drinking a carb solution (like a sports drink) but spitting it out rather than swallowing it. Turns out, just rinsing a high-carb beverage can trick your body into thinking you actually consumed carbs. (Related: What Is Carb Cycling and Should You Try It?)

It's true: A 2009 study from the University of Birmingham found that carb-rinsing activated muscles as if the athletes had actually consumed carbs; athletes who rinsed performed just as well as those who fueled up on food or a sports drink. A 2014 review of studies on carb-rinsing also found that carb rinsing seems to have a positive effect on athletic performance during moderate- to high-intensity exercise of at least an hour or longer.

How Does Carb Rinsing Work?

A 2016 study published in Medicine & Science in Sports & Exercise goes more in-depth into how and why carb-rinsing actually works: Researchers tested male cyclists in a variety of states (fed, fasted, and depleted), and found that carb-rinsing was most effective when their energy stores were drastically reduced. The researchers believe that carb-rinsing tricks your brain into thinking more fuel is heading toward your muscles, and either convinces them to work harder or transmits signals to them more efficiently. (Here are other science-backed strategies to push through workout fatigue.)

Here are the deets: The researchers tested eight male cyclists under different experimental conditions: One round of testing was done with the cyclists in a "fed" state (they'd had breakfast at 6 a.m. then started the experiment at 8 a.m.). Another round of testing was done with the cyclists in a "fasted" state (they had an 8 p.m. dinner and a 12-hour fast before the 8 a.m. experiment). The last round of testing put the cyclists in a "depleted" state (they did a 6 p.m. workout consisting of 90 minutes of high-intensity cycling and six intervals of one minute of hard riding with one minute of rest, followed by a very-low-carb dinner at 8 p.m., and then a 12-hour fast until the experiment at 8 a.m.). (Related: These foods can help boost your workout performance.)

For the experimental trial, cyclists in each condition (fed, fasted, and depleted) completed 30 minutes of hard cycling and a 20km cycling time-trial with periodic carb-rinsing or rinsing with a placebo.

The overall results were consistent with previous studies that showed carb-rinsing was most effective when energy stores are super low. When cyclists were in a fed state, the carb-rinsing didn't have a significant effect on the time-trial times (both placebo and carb-rinse trail times were around 41 minutes). When they were in a fasted state, it had a slight benefit (placebo rinse times averaged about 43 minutes, while carb-rinse times averaged 41 minutes). And when cyclists were in a depleted state, there was a significant benefit (placebo rinse times averaged 48 minutes, while carb-rinse times averaged 44 minutes). The study also found, by monitoring the cyclists' quads with an EMG sensor, that muscle activity is reduced when they were in the depleted condition, but it was counteracted by carb-rinsing.

Should You Try Carb Rinsing?

It's worth noting that even with carb-rinsing, the time-trial times were worse at a depleted and fasted state than in a fed state, proving that if you have the opportunity to fuel properly, you should. (Studies have shown that eating carbs before training improves endurance because carbs are the fuel that allows your brain, muscles, and nerves to do their jobs. Without enough you "hit the wall" like a car running out of gas.) These positive effects from carb rinsing are only seen when your body is seriously depleted. Chances are, you're not going into a workout without having eaten in 12 hours. And, if it's available to you, it's just as easy (and better for you!) to actually swallow the sports drink if your body needs it that desperately.

However, carb-rinsing can come in handy. Other studies show that carb consumption during intense exercise can cause all sorts of GI distress, meaning swishing and spitting can be a good alternative when you're powering through a long event (like a marathon, triathlon, lengthy cycling race... or World Cup game) but can't stomach eating carbs from food, chews, or goos.

Otherwise, it's important for athletes (or people training like athletes) to eat carbs at every meal. A high overall carb intake allows athletes to stock carbs in their muscles. That "piggy bank" of carbs, called glycogen, can then be accessed immediately to keep your muscles working. Glycogen stores are especially important for endurance athletes, to keep you going during long activities when you can't stop and eat. (See: Why Healthy Carbs Belong In Your Diet.)

In general athletes need about 50-60% of their daily calories from carbs. For an athlete who needs 2,500 calories a day that's somewhere between 300 and 400 grams of carbs. And of course the best choices are those created by Mother Nature – fruits, veggies, and whole grains, which are carbs naturally bundled with vitamins, minerals, and antioxidants.

If you're not an athlete you can stick with a slightly lower percentage of calories from carbs, say 45 to 50 percent and, of course, non-athletes generally need fewer total calories (for 150-pound person office work burns about 100 calories per hour). So for a person who only needs 1,600 calories a day that's about 200 grams of carbs daily.