June 22, 2023
Many competitive athletes—especially cyclists and runners—swear by ketone drinks. They believe that the popular sports supplement improves athletic performance by packing many of the purported benefits of a low-carb, high-fat, ketogenic diet into a single beverage, reports The Washington Post.
But in a new study—performed jointly by researchers at McMaster University in Canada and at Maastricht University in The Netherlands—the supplement didn’t amplify recreational cyclists’ racing speed and instead left them performing worse after swallowing the beverage than after a placebo. It also gave many of them gas.
“In our opinion, there is currently no evidence that acutely ingesting ketone supplements during exercise provides a benefit for an athlete,” said Chiel Poffé, a postdoctoral researcher at KU Leuven in Belgium, who has studied ketone drinks but was not part of the new study.
But the story of the rise and thud of ketone drinks, if discouraging for athletes, offers a helpful reminder to the rest of us to be wary of nutrition or fitness claims that sound a little too good to be true.
The keto diet in a bottle
It was the high expectations for ketone supplements that prompted Martin Gibala, a professor of Kinesiology at McMaster University, and his graduate student Devin McCarthy, to undertake the new study, which was published online in April in the International Journal of Sport Nutrition and Exercise Metabolism. With other collaborators, they wanted to test whether the ketone supplement would work in real-world sporting conditions.
The primary rationale for athletes to swallow ketones (which come in powdered, as well as liquid, form) was clear enough. They seemed to be getting the keto diet in a bottle.
On a ketogenic, or very low-carbohydrate, high-fat diet, the body produces ketone bodies, commonly called ketones, which can be used by the heart, brain, and other organs as fuel; while the muscles start relying mostly on fat rather than carbs for energy. Since our bodies store much more fat than carbohydrates, ketogenic diets theoretically should allow endurance athletes to train and race longer and harder before bonking or hitting the wall.
But any such effects—which have proven elusive in actual elite athletes—require weeks or months of bingeing on bacon and butter before a person’s body starts efficiently using fat as its primary fuel.
Cycling slower on ketones
Then they had them complete two separate 20-minute time trials on stationary bikes. Before one, they downed a ketone supplement that’s widely available commercially. On the other, they drank a beverage with similar flavoring but no ketones.
“It was a really simple study,” McCarthy said.
Som past ketone research had required hours of pre-exercise fasting or other complicated dietary routines that serious athletes wouldn’t use in training or competitions.
The cyclists couldn’t and didn’t ride as hard, in other words, but the effort felt as draining as after the placebo.
Burps, bloating, and bitterness
The ketone drink also had other downsides. “The taste is horrible, extremely bitter,” said Poffé, who has had occasion to sip ketone beverages as part of his research.
The drink also caused stomach and intestinal problems in most of the riders, who complained of bloating, burping, flatulence, heartburn, and stomach pain. Thankfully, “there were no incidences of regurgitation or projectile vomiting,” the study reports, although those have occurred in some experiments with ketone drinks.
Interestingly, these digestive side-effects have been known for some time in athletic circles but barely slowed acceptance of the supplement. “Ketone supplements are still widely used among elite athletes, to our knowledge,” Poffé said.
“I suspect some athletes would drink battery acid if someone told them it would improve performance,” Gibala said.
Research contact: @washingtonpost