How to Read a Food Label for Low-FODMAP

1. The allium names — the biggest single category

Onion and garlic are high in fructans at any portion, and they are in a startling proportion of savoury processed food because they are the cheapest way to make something taste cooked. Dehydrated forms are worse than fresh, because drying concentrates the fructans by weight — a teaspoon of onion powder carries far more than a teaspoon of chopped onion.

The practical consequence is that stock cubes, gravy granules, crisps, crackers, marinades, ready meals, sausages, deli meat and barbecue sauce are all suspect until read. Note that garlic-infused oil is the deliberate exception: fructans are water-soluble and do not migrate into fat, so infused oil carries the flavour and none of the problem.

2. Added fibre — the health-food trap

This is the category that catches the most people, because it appears specifically on products marketed as good for you. Manufacturers add prebiotic fibre to boost the fibre number on the nutrition panel and to justify a gut-health claim. The most common addition is inulin, extracted from chicory root — and inulin is a fructan. It is, in fact, close to a pure fructan concentrate.

The bitter irony is real: a "gut-healthy high-fibre" yogurt, a keto bar, or a fibre-fortified cereal can be a worse choice for IBS than the plain version it replaced. Protein bars and granola are the classic offenders, and inulin turns up increasingly in gluten-free bread, ice cream and "low-sugar" chocolate. Prebiotics genuinely do feed beneficial bacteria — that is exactly the mechanism that produces gas in a sensitive gut.

3. Polyols and the laxative warning

Polyols — sugar alcohols — are the P in FODMAP, and anything labelled sugar-free is a candidate. They are poorly absorbed by design, which is what makes them low-calorie and also what makes them ferment.

The single most useful sentence on any label: "Excess consumption may have a laxative effect." That warning is legally triggered by a significant polyol content, which means the manufacturer has told you the dose is meaningful without you having to interpret anything. Sugar-free gum, mints, "no added sugar" squash and diabetic chocolate are the usual carriers.

4. Excess-fructose sugars

Fructose is absorbed in the small intestine by a transporter that works far better when glucose is present alongside it. Sweeteners with more fructose than glucose overwhelm that route, and the excess passes on to the colon. So the question is not "is there sugar in this" but "is the sugar fructose-dominant".

• Avoid: high-fructose corn syrup, HFCS, agave syrup, honey, fructose, crystalline fructose, fruit juice concentrate, apple juice concentrate, pear juice concentrate, corn syrup solids.
• Fine: sucrose, cane sugar, glucose, dextrose, glucose syrup, rice syrup, maple syrup at 2 tbsp.

"Sweetened with fruit juice" and "no refined sugar" are marketing phrases that frequently mean apple or pear juice concentrate — two of the most fructose-dominant sweeteners available. Apple juice and date paste both fall into the same trap, which is why so many "refined-sugar-free" snacks trigger symptoms.

5. Wheat in disguise, and legume flours

Wheat appears under a lot of names that do not contain the word wheat: semolina, durum, durum wheat, couscous, bulgur, farro, spelt, kamut, freekeh, rusk, breadcrumb, malt extract, malted barley, barley, rye, triticale, and seitan (which is pure wheat gluten). Rusk in particular is the standard filler in British sausages and burgers.

Legume flours carry GOS: chickpea flour, besan, gram flour, lentil flour, fava bean flour, soy flour, and chickpea- or lentil-based pastas and crisps, which have become popular as high-protein alternatives. Baked beans and green peas are the whole-food versions of the same problem. One genuine exception: pea protein isolate is heavily processed in a way that strips out most of the GOS, so pea protein powders are usually well tolerated despite the name.

For lactose, the flags are milk, milk solids, milk powder, skimmed milk powder, whey, whey powder and buttermilk powder. Note the split within dairy proteins: whey protein concentrate retains lactose, while whey protein isolate has had almost all of it removed and is usually fine. Butter and hard aged cheeses are low in lactose too — the mechanism is explained in our piece on why some cheeses trigger IBS and others do not.

The 15-second scan

You do not need to read a label like a document. Read it like a search, in this order:

1. Scan for onion and garlic in any form — including the umbrella terms. This one check eliminates most savoury products.
2. Scan for inulin, chicory root and FOS. Fastest way to disqualify a "healthy" product.
3. Check the sweetener. Fructose-dominant, or a polyol other than erythritol? Out. Look for the laxative warning.
4. Check the flour and the fibre source. Wheat under any alias, or a legume flour?
5. Check where the offender sits in the list, and check the serving size. Ingredients are ordered by descending weight, so last-of-twenty is a very different dose from second-of-five — and FODMAPs are dose-dependent. Then confirm the stated serving matches what you will actually eat, since the whole tub is not the 30g on the panel.

That last step is the one people skip, and it is where the diet stops being all-or-nothing. A trace of onion powder at the end of a long ingredient list is often perfectly tolerable. Being able to make that call is the difference between a workable diet and a miserable one.

Shortcuts worth using

Certification logos. Some packaged goods carry a Monash-certified or FODMAP Friendly mark, meaning the finished product has been lab-tested against threshold values rather than merely assessed by ingredient. When you find a certified brand you like, it removes the label-reading burden for that product entirely.

Look the ingredient up rather than guessing. If you are standing in an aisle unsure about an ingredient, our IBS food checker gives you the grade and Monash portion for individual foods, and the full FODMAP food database covers every ingredient we have written up. For a whole product rather than a single ingredient, the GutAI app reads a photo of the ingredient list and flags the FODMAPs for you.

Keep a personal safe list. Label formulations change, but slowly. Once you have cleared a product, write it down. Within a few weeks of shopping you will have a list that covers most of a normal week, and the scanning drops away to only new products. Our complete low-FODMAP grocery list is a starting point, and the seven most common low-FODMAP mistakes covers the errors that most often undo careful shopping.

Frequently Asked Questions