Supplements for Runners — Running Nutrition | 6AM Run

Your legs are ready. Your lungs are ready. Then at mile 18 your stomach decides the race is over. Sloshing, cramps, a sudden urgent search for a porta-potty — gut problems ruin more marathons than bad weather and missed workouts combined. Studies of marathon finishers routinely find 30 to 50 percent report gastrointestinal symptoms during a race.

Here is the part most runners miss: your gut is trainable, just like your legs. The stomach and intestines adapt to taking in fuel while you run, but only if you practice it on purpose. This is the 6-week gut-training plan I give every runner who tells me they “just can’t eat during a run.”

Why your stomach rebels on race day

When you run hard, blood moves away from your digestive system toward your working muscles. That alone slows digestion. Add three common mistakes and trouble is almost guaranteed:

• Taking in more on race day than you ever did in training. A gel every 30 minutes sounds simple until your untrained gut meets 60 grams of carbs per hour at mile 15.
• Concentrated fuel with too little water. Very sugary drinks and gels sitting in the stomach pull water in and cause sloshing and cramps.
• New products on race morning. Different sugar mixes, fiber, fat, and caffeine all change how fuel empties from your stomach.

If you want the carb math first, start with our Marathon Fueling Calculator guide. Gut training is how you teach your body to actually handle those numbers.

The golden rule: nothing new, and progress like mileage

You would never jump from a 10-mile long run to 20 miles in one week. Treat gut training the same way. Increase the amount of fuel you take during runs by roughly 10 to 15 grams of carbohydrate per hour each week, and practice at race effort at least once a week. Easy runs are useful for habit-building, but your gut behaves differently at marathon pace, so one session a week needs to be at goal pace or faster.

The 6-week gut-training plan

Weeks 1–2: Build the habit

On every run longer than 60 minutes, take in 30 grams of carbs per hour — roughly one standard gel, a serving of chews, or a handful of gummies every 30 minutes. Sip water steadily instead of chugging at aid stations. Eat your normal pre-run breakfast 2 to 3 hours before, using the framework in What to Eat the Morning of a Marathon. The goal this block is zero drama, not maximum carbs.

Weeks 3–4: Push toward race targets

Move to 45 to 60 grams per hour on your long run and your marathon-pace workout. Practice your exact race timing: set a watch alert every 30 minutes and eat on the alert, not when you feel hungry — by the time you feel empty, you are already behind, which is exactly how runners end up hitting the wall at mile 20. If 60 grams causes trouble, hold there for an extra week instead of forcing week 5.

Weeks 5–6: Dress rehearsal

Your longest run becomes a full race simulation: same wake-up time, same breakfast, same fuel, same hourly carb target you plan for race day — 60 grams per hour for most runners, up to 90 for experienced runners who have built up to it. Drink to a plan as well, and review your sodium needs with our guide on how many electrolytes runners actually need. If the rehearsal goes clean, you have your race-day system. If it does not, you still have time to adjust one variable — timing, water, or product — and retest.

Pick fuel your stomach can learn

Consistency beats variety during gut training. Use the same product, in the same amount, at the same intervals, so your gut adapts to one predictable input. A few practical points from years of testing on myself:

• Smaller, more frequent doses beat big boluses. Half a serving every 15 to 20 minutes is gentler than a full serving every 40.
• Mix your sugar sources once you pass 60 grams per hour. Glucose-only fuel tops out around 60 grams per hour; blends that also use fructose can be absorbed faster. Our comparison of gels vs. gummies vs. chews breaks down the tradeoffs honestly — gels are fastest, but they are sticky and hard to portion.
• Portability matters at mile 20. This is why I personally train with 6AM Run Marathon Gummies for a lot of my gut-training sessions: I can take a few at a time instead of committing to a whole gel at once, there is no sticky mess on my hands, and the dose is easy to repeat exactly the same way every 15 minutes. Whatever you choose, choose something you can dose in small pieces.
• Keep fiber, fat, and protein low during the run. They slow stomach emptying. Save them for after.

Troubleshooting the three most common problems

Sloshing and nausea: usually too much fluid or too-concentrated fuel at once. Spread intake out, take fuel with water, and slow down for two minutes after a dose rather than surging.

Cramps and urgency in the last hour: often fructose overload from a new product, or caffeine taken late for the first time. Practice your caffeine timing in training — never debut it on race day.

Reflux and burping: large doses swallowed while running hard. Smaller doses and eating during a brief walk through an aid station can help; you lose seconds and save your stomach.

After the run: finish the training effect

Gut training does not end at your front door. Within 30 to 60 minutes, get carbs to refill glycogen plus protein or amino acids to start repair, and keep sipping fluid with electrolytes until your weight and urine color look normal again. On my own long-run days I use FinishLine in that window because it is simple, sits light after a hard stomach day, and gets the recovery process moving while I make a real meal. A full meal within two hours still matters — the drink is the bridge, not the replacement.

Your one-week starter checklist

• Pick ONE fuel and commit to it for the next 6 weeks.
• Set a 30-minute fuel alert on your watch.
• Start at 30 grams per hour on runs over 60 minutes.
• Log fuel, water, and any stomach symptoms after every long run — same detail as your mileage log.
• Add about 10 grams per hour each week toward your race target.
• Run one full dress rehearsal at least 10 days before race day.

Your stomach is not weak. It is untrained. Give it the same patient, progressive six weeks you gave your legs, and race day stops being a gamble. See you out there at 6AM.

— Hami, 6AM Run