Low-FODMAP Diet for Runners: Race-Week Filter

A low-FODMAP race week for plant-based runners is a temporary overlap with the site’s ~15 g fiber/day gut heuristic: cut fermentable carbs that pull water and gas into the gut for about 48–72 hours while carbohydrate rises toward 8–12 g/kg. It is not an IBS diagnosis, not a permanent Monash-style elimination diet, and not medical advice.

If you have diagnosed IBS, IBD, or a clinician-prescribed FODMAP plan, follow that plan. This page is for runners who already eat plant-based staples, want fewer mid-race bathroom emergencies, and still need a shopping list that hits a vegan carb load. Broader GI mechanics live in preventing runner’s diarrhea.

What FODMAPs are (and what this page is not)

FODMAPs are fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. In vegan kitchens that usually means:

• Oligosaccharides (GOS/fructans): beans, lentils, chickpeas, onion, garlic, wheat in larger amounts, many whole grains
• Excess fructose: large servings of apple, pear, mango, dried fruit, some juices, and honey (honey is also not vegan)
• Polyols: stone fruit, sugar-free gum and “diet” gels with sugar alcohols, some mushrooms

They draw water into the small intestine and ferment in the colon. During prolonged running, splanchnic blood flow falls and residual contents sit longer — the pattern de Oliveira, Burini, and Jeukendrup (2014) describe. Fiber volume and fermentable load both sit on the “contents” side of that problem.

Clinical low-FODMAP work (for example Gibson and Shepherd, 2010) is a structured, usually dietitian-supervised process. Race week is not that process. You are lowering residue and gas for two hard days so 8–12 g/kg of carbohydrate can land without a bean-chili colon.

How this maps onto the ~15 g fiber heuristic

plantbaes.net uses about 15 g of fiber per day for the final 36–48 hours of race week. That is a site gut-management heuristic, not an ACSM fiber target and not a Monash FODMAP threshold.

Many high-FODMAP vegan foods are also high-fiber. Cutting lentils, chickpeas, bran, and large raw salads often moves both knobs at once.

| Knob | What it controls | Race-week target on this site | | --- | --- | --- | | Fiber (g/day) | Residue volume | ~15 g/day for ~48 hours (heuristic) | | FODMAP load | Osmotic water pull + fermentation | Lower for ~48–72 hours (practical filter) | | Carbohydrate (g/kg) | Glycogen for the race | About 8–12 g/kg for 36–48 hours |

You can hit 15 g of fiber and still wreck the gut with onion-garlic pasta sauce, a litre of apple juice, or a handful of dried mango. Fiber and FODMAP are related, not identical. Check the fiber column with the fiber load checker.

Day-by-day: when to tighten the filter

1. 7–5 days out: Keep familiar training food. Optionally swap one grain meal to white rice or white pasta.
2. 4–3 days out: Drop beans, large servings of onion/garlic, bran, and dried fruit. Begin raising carbohydrate.
3. 2–1 days out: Hold the ~15 g fiber ceiling and the low-FODMAP filter while hitting 8–12 g/kg. Scale grams with the carb-loading calculator.
4. Race morning: Practised low-residue breakfast only. No overnight oats with chia “because an app said a small serve of oats is OK.”
5. After the finish: Reintroduce legumes and vegetables over a few days.

Vegan swap table (race week, not forever)

| Everyday plant plate | Why it bites | Race-week swap | | --- | --- | --- | | Lentil or chickpea bowl | High GOS + fiber | Firm tofu + white rice | | Onion–garlic tomato sauce | Fructans | Plain tomato passata or soy sauce + oil on pasta | | Steel-cut oats + chia + berries | Fiber stack; fruit FODMAPs | Cream of rice or white bagel + maple | | Apple, pear, dried fruit | Excess fructose / polyols | Ripe banana (budgeted) or counted pulp-free juice | | Wheat-heavy grain bowls | Fructans + fiber | White pasta, rice noodles, bagels | | Sugar-free gum / polyol gels | Osmotic load | Practised glucose/fructose gels without sugar alcohols | | Hummus + raw veg | Chickpeas + crucifers | Soft tofu, peeled cucumber, rice cakes |

What stays on the plate

Low FODMAP does not mean low carb.

• White rice, white pasta, rice noodles, bagels, rice cakes, cream of rice
• Maple syrup, seedless jam in measured amounts
• Firm tofu, fortified soy milk
• Ripe banana if the rest of the day is sparse on fiber
• Pulp-free juice counted toward the daily carb total
• A manufacturer-confirmed vegan drink mix you have already used

Skip new gel flavours, honey packets, and “real food” mid-race dates. Race-day fueling still follows practised rates — about 30–60 g/h from a single source, rising toward ~90 g/h with glucose + fructose after gut training.

Common mistakes: treating two days like a six-week clinical elimination; cutting FODMAPs for ten days; free-pouring apple juice; assuming a garlic-bomb sauce is “just oil.” Recurrent pain, blood, weight loss, or night symptoms need a clinician — not another race-week article.