Nutrition? What’s that?
From https://www.outsideonline.com/1915526/yes-you-can-run-ultramarathon:
“Off the line, you’re full. You don’t need anything for the first hour, maybe two hours,” Blende says. After that, you’ll have to start eating or drinking calories. But while you’ll burn about 100 calories per mile, your body can only absorb about 240 calories per hour, so it’s important not to eat too much, or you can get sick.
“It’s a deficit sport. You can’t eat all that you’re expending,” Blende says. “The best way to consume calories during a 50-mile race is to think of dripping them in like an IV.” She recommends setting a watch on a timer so it beeps every 15 minutes. Each time the alarm sounds, eat or drink something, whether it’s a gel, chew, sports drink, a peanut butter and jelly sandwich, or a baked potato dipped in salt. “Leave a little of everything in your drop bag,” Blende says. “Leave your gels, your chews, your sports foods, your mixed drinks, because you might need it or you might have dropped something.” As for hydrating, the rule is simple: Drink according to thirst.
Should your stomach get upset, slow down, stop eating, or take in less. Keep up your hydration if you’re thirsty, and then start adding things back in. “Sometimes when you throw up, it’s really just your body saying, ‘OK, I’m wiping the slate clean, let’s start over,’” Blende says. Keep calm, and keep moving.