Last month, when the Kenyan runner Eliud Kipchoge ran the fastest marathon ever, he had cyclists alongside him feed him a sugary drink. Likewise, on Sunday, the New York City Marathon will litter the streets with empty packets previously filled with goos and gels of simple sugars. I will be among the runners, and this time I am determined to hit no walls. I’ve started training by eating Sour Patch Kids on long runs. I had some left over from my birthday party, and I found that, unlike the commercial formulas that somehow manage to make sugar taste bad, candy makes training much more enjoyable.
Read: The greatest, fakest world record
Then I saw a new study that seemed to suggest I should be eating potatoes instead. When ingested, the starch in potatoes breaks down to become glucose, so at least the concept is sound. In the Journal of Applied Physiology, researchers at the University of Illinois compared the performance of elite cyclists when they were fed three different substances: a sugary goo, an identical amount of carbohydrate as potato puree, and a placebo. Twelve endurance athletes each did a two-hour time trial under each condition, on separate days. All were fed through a syringe, their physiology tracked minute by minute. The performances suffered in the placebo condition, as expected. But overall, the distances were comparable when the athletes got sugar and when they got potato puree.
The study’s authors, led by Nicholas Burd, a kinesiology researcher at the University of Illinois, were curious about potatoes because some athletes already eat them during competitions—especially ultramarathoners, who sometimes run for days at a time. The researchers also knew that the panoply of gels for sale at a pre-race expo can be overwhelming, and that the decision of how to properly fuel oneself is a source of anxiety. “I told my research team, just go buy potatoes, bake them, and puree them,” Burd told me.
The research was funded by a grant from the potato industry, but he says the point isn’t that everyone should eat more potatoes. The results simply show, according to Burd, that “you don’t have to be too fancy with your fueling strategy. At the end of the day, you just need to increase carbohydrate availability—whether it’s from a goo or from a potato.”
He sees this study as basic proof of concept that rice or comparable starchy foods might be effectively interspersed during lengthy events. Both have the additional benefit of being cost-effective, plus Bird posits that a savory option can avoid the “flavor fatigue” of using the pure-sugar concoctions for hours upon hours of exercise.
Intrigued, I asked him if I should bring a potato with me on Sunday. But he was definitely opposed. “Switching up your dietary strategy on race day is one of the worst things you can do,” he said. This was a relief to hear, because I was already deterred by a caveat in the study: When the cyclists ate the potatoes, they experienced higher levels of abdominal pain, flatulence, and bloating. (The paper contains a bar graph whose vertical axis is “Flatulence %”). The effect might be due to the fact that to get enough sugar, the cyclists had to eat the pureed equivalent of four potatoes per hour.