7 Common Nutrition Mistakes in Ultra Running

Ultra running nutrition isn't complicated, but it is unforgiving. Small mistakes compound over 50 or 100 miles until they become race-ending problems. Most DNFs in ultras have a nutrition component — either as the primary cause or as a contributing factor that made everything else worse.

These are the seven mistakes I see over and over again, and they're all preventable.

Mistake 1: All Gels, All Day

Gels are convenient. They're calorie-dense, easy to carry, and they work great for the first few hours. So runners stuff their vest with 30 gels and plan to take one every 30 minutes for the entire race.

By hour 6, they're vomiting.

The problem is concentrated simple sugar. Your gut can handle it when blood flow to your digestive system is adequate — roughly the first 4–6 hours. After that, your gut slows down, and dumping 100 calories of pure maltodextrin into it every 30 minutes overwhelms the system. The sugar sits in your stomach, draws in water through osmosis, and creates the nausea-bloating-vomiting cascade that ends races.

The fix: Use gels for the first 4–5 hours, then transition to real food. Boiled potatoes, PB&J, rice balls, quesadillas, pretzels. Your gut handles complex foods with mixed macronutrients better than simple sugar as the race goes on.

Mistake 2: Not Eating Enough in the First Half

You feel great at the start. You're not hungry. Eating feels unnecessary. So you skip a few fueling windows and figure you'll make up for it later.

You won't. By the time you're in calorie debt, your body has already started to shut down systems to conserve energy. Your pace drops, your mood crashes, you get cold, and worst of all — your appetite disappears completely. You're now in a spiral: you need calories to feel better, but you feel too bad to eat.

The fix: Eat on a schedule, not by feel. Set a timer on your watch for every 30 minutes. When it goes off, eat 150–200 calories regardless of whether you're hungry. Front-loading calories in the first half of the race gives you a buffer for the inevitable drop in appetite later.

Mistake 3: Ignoring Sodium

Water and calories get all the attention. Sodium gets ignored until a runner collapses at mile 50 with hyponatremia or stumbles into an aid station with cramping so bad they can't walk.

You lose 500–1,500mg of sodium per hour through sweat, depending on conditions and your personal sweat rate. If you're only replacing water and calories, your blood sodium concentration drops steadily. The symptoms are insidious: first a vague malaise, then bloating, then nausea, then confusion. By the time you realize it's a sodium problem, you're in trouble.

The fix: Supplement sodium from the start. Electrolyte capsules (200–400mg sodium each) every 30–45 minutes are the simplest approach. Salty foods at aid stations help too — broth, salted potatoes, pretzels, chips. In hot conditions, you may need 500–1,000mg per hour. Test your sodium needs in training. If you finish long runs with white salt stains on your clothes, you're a heavy sodium sweater and need to supplement aggressively.

Mistake 4: Trying New Foods on Race Day

The aid station has something you've never tried — a homemade quesadilla, some mysterious energy balls, a new sports drink. It smells amazing. You're hungry. What could go wrong?

Everything. Your gut is already under stress from hours of running. Introducing an unknown food — with unknown ingredients, unknown fiber content, unknown fat levels — is a gamble with terrible odds. Some runners get lucky. Many don't.

The fix: Eat only foods you've tested in training. Every gel, every real food, every drink mix should have been consumed during long runs at race effort. Your race nutrition plan should be finalized weeks before race day, not improvised at aid stations.

The one exception: broth. Almost everyone tolerates broth, and it provides sodium, warmth, and a small number of calories. If you haven't trained with it, broth is usually a safe bet.

Mistake 5: Drinking Too Much Plain Water

Overhydration is more common than dehydration in ultras, especially in cooler conditions. Runners dutifully drink every 15 minutes, fill their bottles at every aid station, and end up diluting their blood sodium to dangerous levels.

Hyponatremia — low blood sodium from overhydration — is a medical emergency. Symptoms include confusion, swelling in the hands and face, nausea, and in severe cases, seizures. Multiple runners have died from hyponatremia in ultras.

The fix: Drink to thirst, not to a schedule. If you're not thirsty, don't drink. When you do drink, make at least half of your fluid intake an electrolyte drink rather than plain water. Monitor your urine: it should be pale yellow, not clear. Clear urine during an ultra means you're drinking too much.

Mistake 6: Going All-In on Caffeine Too Early

Caffeine is a genuine performance enhancer. It increases alertness, reduces perceived effort, and can be the difference between a death march and a strong finish. But it has diminishing returns, and if you deploy it too early, you won't have it when you need it most.

Runners who start taking caffeinated gels at mile 10 build tolerance throughout the race. By the time they hit the night section at mile 60 — when caffeine could actually save their race — it barely makes a dent.

The fix: Save caffeine for the second half of the race. In a 100-miler, don't touch caffeine until mile 40–50 at the earliest. Then deploy it strategically: 100mg every 2–3 hours through the night section. Your total caffeine intake in a 100-miler should be 400–600mg, spread across the back half. If you're a regular coffee drinker, don't skip your morning coffee before the race — caffeine withdrawal headaches at mile 20 are not what you want.

Mistake 7: No Plan B

Your nutrition plan is dialed. You've trained with it for months. Then the race happens: it's hotter than expected, your stomach starts acting up at mile 30 instead of mile 60, and the aid station ran out of your preferred food.

If your entire plan hinges on one specific set of foods in one specific pattern, you're one bad stomach away from a DNF.

The fix: Build a hierarchy of options. Plan A is your tested, dialed-in nutrition strategy. Plan B is a simplified version — maybe just broth, flat cola, and potatoes. Plan C is survival mode: tiny sips of ginger ale, small bites of whatever you can keep down, walking until your stomach settles.

Know your Plan B and Plan C before race day. Practice downgrading in training — deliberately run a long run on only aid station food to see what you can tolerate. The runners who finish 100-milers aren't the ones with perfect nutrition plans. They're the ones who can adapt when the plan falls apart.

The Common Thread

Every one of these mistakes comes from the same root cause: treating ultra nutrition like marathon nutrition. In a marathon, you can get away with gels and water for 3–4 hours. In an ultra, you're feeding a machine for 12–30+ hours, through wildly varying conditions, with a digestive system that's progressively shutting down.

Respect the distance. Test everything. Have a backup plan. Your legs can probably get you to the finish — but only if your stomach cooperates.