Low-FODMAP food lists: why they disagree and how to use one safely

What a food list can and cannot tell you

FODMAPs are fermentable short-chain carbohydrates: oligosaccharides such as fructans and galacto-oligosaccharides, lactose, fructose and polyols. Monash University says they can trigger symptoms in people with irritable bowel syndrome (IBS), and that it is impossible to guess the FODMAP content of a food, because careful laboratory analysis is needed.

A list copies the result of that analysis for certain foods and portions at one point in time. It cannot know your recipe, your brand, how ripe the fruit was or how much you served. This page does not reproduce a list. It explains how to read one.

Portions decide the rating

Monash’s app rates foods low, moderate or high in FODMAPs with a traffic light system. The rating belongs to a serving size. A food can be green at a small serving and amber or red at a larger one, so a list that says only “low” without a portion is incomplete.

Quantity matters in the science too. The 2013 review by Shepherd, Lomer and Gibson notes that poorly absorbed short-chain carbohydrates have similar and additive effects in the gut, which is a reason to think about the whole meal and not one food. Count the portion, and count what else was on the plate.

Why two lists disagree

The likely reasons are plain. Lists may use different serving sizes, different cutoffs or data from different dates, and some copy older tables or mix sources. Laboratory results also differ a lot from food to food: a 2007 study by Muir and colleagues measured fructans in 60 vegetables and 43 fruits, and the vegetables highest in fructans, such as garlic, artichoke, shallots, leek bulb and onions, ranged from 1.2 to 17.4 grams per 100 grams.

These are likely explanations, not a ruling on which list is right. When two sources differ, go to the one that shows the serving size, which the official app does.

How to check a food in the official source

Open the Monash University FODMAP Diet app and search the exact food, for example the form you will eat. Look at the serving size shown beside the rating. If your food is a packaged product, check its ingredient list for items you know are high, and ask a dietitian about the rest.

If the food is not in the app, do not guess. Monash says no one can guess FODMAP content, so treat the food as unknown, try it in a small portion at a calm time, and write down what happens.

• Search the exact food and the portion you will eat.
• Read the rating for that portion, not for the food in general.
• Note the date of your printed list if you compare it to the app.
• Ask your dietitian when the app and your experience disagree.

Who the diet is for, and how long it lasts

Monash says the diet is intended for people with medically diagnosed IBS. Several conditions have similar symptoms, such as celiac disease, inflammatory bowel disease, endometriosis and bowel cancer, so do not self-diagnose. See a doctor first.

Monash describes a period of high restriction lasting 2 to 6 weeks, then a more relaxed diet as foods are gradually reintroduced. It says symptoms improve in 3 out of 4 people and do not in 1 out of 4, and that the diet is best followed under the supervision of a qualified dietitian or healthcare professional. Gibson and Shepherd reached the same view in 2010: it needs expert delivery.

Log what you actually ate

A list tells you what a lab found. Your own log tells you what happened to you. Write down the food, the portion in grams or a measure, the time, and how you felt over the next hours. A pattern needs several entries, and one bad day with a stressful meeting proves little.

During reintroduction, change one thing at a time and record the dose and response, so that you and your dietitian can see which group affects you.