- Rinsing with but not swallowing carbohydrate drinks is a proven performance-enhancer.
- Research has found that bitter, hot, and cold tastes might also help you run farther or faster.
Back when there were major marathons to watch, you may have noticed a seeming oddity: Elites would grab their bottles at the 40K aid station, even though someone like world record-holder Eliud Kipchoge had less than seven minutes of running left at that point.
If you looked closely, you would have seen Kipchoge and others sip from their bottles, then spit the drink out. What’s become known as rinse-and-spit has caught on among elites for the simple reason that it works—research has consistently shown that the technique improves endurance performance. For example, in one study, cyclists rode at a steady pace for two hours, and then did a 30-minute time trial. When they rinsed and spat a carbohydrate drink, they rode 1.7 percent farther in the time trial than when they rinsed and spat a similar-tasting carb-free drink.
With carbohydrate rinse-and-spit established in the lab and in elite practice, it’s logical to ask: Are there are other foods and drinks that can improve performance just by tasting them?
The answer appears to be yes, according to a research review published in the European Journal of Nutrition. In addition to the sweet taste of carbohydrates, researchers have investigated the performance benefits of bitter, hot (spicy), and cooling tastes. Here’s what they’ve found about those—jargon alert!—“tastants” and why they work.
Sweet Tastes
As the new research review notes, there’s overwhelming evidence in favor of carbohydrate rinse-and-spit. The technique appears to be most effective in people who are running low on glycogen, your muscles’ stored form of carbohydrate. Rinse-and-spit is used most often by marathoners past the 20-mile mark, when there might not be time for the carbs in a sport drink to be converted to fuel. Another reason it’s most often done late in a race is to get a performance boost without putting more liquid in what might be an increasingly wonky digestive system.
How can tasting carbs but not digesting them help performance? Aren’t muscles either low on fuel or not?
The key to rinse-and-spit are “receptors in the mouth that detect the presence of carbohydrate, which then relay the message that a potential source of fuel is coming,” said Russ Best, Ph.D. at the Center for Sports Science and Human Performance in Wintec, New Zealand, and the lead author of the new research review. “This lights up a range of areas in the brain that are associated with emotion, motor control, and reward. This interaction might improve performance in a range of ways, including quicker reaction times, improved decision-making, and power output without actually affecting the fuel levels within athletes’ muscles.”
Even if you’re not yet a rinse-and-spit aficionado, you might have experience with this phenomenon. Think about getting home from a long run and eating or drinking something sweet, and almost immediately feeling better. That boost occurs before your body’s fuel supplies have been affected by what you consumed.
It should be noted that saying the taste of sweets is what helps isn’t entirely accurate. Rinsing with a flavorless carbohydrate can boost performance, while rinsing with a sweet carb-free drink, such as diet soda, hasn’t been found to help.
Best speculates that the effect is because of carbohydrates binding with receptors that send various encouraging signals to the brain but that researchers have yet to identify. “We see similar physiological responses in people with loss of taste and smell, strongly suggesting that these effects run deeper than taste alone,” he said.
Bitter Tastes
As you’ve probably noticed, almost all sport nutrition products lean heavily on sweetness. But research backs expanding your palette. The research review notes that bitter tastes activate similar areas of the brain as sweet tastes. One study found a boost in cyclists’ sprint performance when they rinsed with and then swallowed a bitter drink. A follow-up study found no benefit from rinsing with but not swallowing a bitter drink. Best writes that this might be the case because there are bitter taste receptors in the upper GI tract that aren’t activated by the rinse-and-spit technique.
What’s a bitter taste? Most of the research, Best said, uses a quinine solution. “This is the ingredient responsible for giving tonic water its familiar bitter taste, so that may be one option,” he said. “Just remember, no gin to go with it!” Pickle juice, which some runners have turned to help with muscle cramps, is another option.
And you might well start your day with a bitter taste—the caffeine in coffee and tea. The research review cites studies in which caffeine mouth rinses improved thinking and lessened mental fatigue during exercise. “Given coffee’s history with running and other endurance sports, I think we’d be foolish not to consider using that too,” Best said.
In practical terms, Best suggested two scenarios when you might opt for bitter over sweet. “Bitter tastes seem to improve shorter duration, power-type performance to a greater extent than sweet tastes, so they may be useful in supporting faster sessions or all-out time trials up to about 1 kilometer or so,” he said.
At the other end of the spectrum, bitter might be best toward the end of long events, such as ultramarathons and triathlons. Rinsing with caffeine late in the game might improve your mood and decision-making. You might also simply welcome a different taste if you’ve been fueling with sweet carbs the previous however many hours.
Hot and Cool Tastes
Spicy foods probably don’t top the list of what you crave late in a long run. That hasn’t stopped researchers from investigating whether capsaicin, a chemical compound that gives chili peppers their “hot” sensation, improves performance. In one study, runners averaged 5 seconds faster in a 1500-meter time trial when they took capsaicin capsules. Another study found that runners did significantly more near-all-out 15-second sprints when they took capsaicin capsules compared to a placebo. The mechanism behind these improved performances remains speculative.
Best said that swilling a diluted hot sauce could be a DIY alternative to capsaicin capsules. “All these hot and spicy products come with the risk of stomach upset and downstream effects, though, so if you are going to trial these, do so in training, and close to a bathroom,” he said.
Perhaps more appealing are cool tastes. Research has found swilling a menthol solution to improve both time trials and time to exhaustion (how long you can maintain a given effort level). Part of the performance benefit is thought to occur because cool tastes “turn on the receptors that are associated with feeling cold temperatures, so they mimic this sensation or improve how comfortable athletes are in the heat,” Best said.
It’s important to note that, although people report feeling cooler after swilling cool-tasting products, their body temperatures aren’t lower. The same phenomenon has been reported in research on ingesting cold water or ice slurries before or during working out in hot conditions. These findings matter because, theoretically, an especially driven runner who sweats heavily could feel cooler despite her core temperature steadily rising, and eventually push herself to the point of heat exhaustion.
In practical terms, Best suggests alcohol-free mint mouthwashes, chewing gum with a strong menthol or mint flavor, peppermint teas, or mint leaves bruised and left in water until the menthol in them is extracted. (An oily layer will appear when that has happened.) He also recommends adding mint flavors to ice slushies on hot days, but warns that downing the slushies too quickly might cause what Best, using the scientific term, calls “brain freeze.”
It’s always interesting to know how researchers make personal use of their findings. When asked whether he has incorporated taste-based drinks into his training, Best replied, “Yes, but only recently. In the past I wanted to remain impartial, but with the growing research in the area and the range of tastes we’re now seeing as beneficial under certain conditions, I think it’s a great way to add a fun element to training. I’m looking forward to having a go with bitter and hot tastes in quality sessions and gym workouts, and use carbohydrate swilling in longer sessions and to support fasted training.”
Scott is a veteran running, fitness, and health journalist who has held senior editorial positions at Runner’s World and Running Times. Much of his writing translates sport science research and elite best practices into practical guidance for everyday athletes. He is the author or coauthor of several running books, including Running Is My Therapy, Advanced Marathoning, and Meb for Mortals. Scott has also written about running for Slate, The Atlantic, the Washington Post, and other members of the sedentary media. His lifetime running odometer is past 110,000 miles, but he’s as much in love as ever.
