Coeliac and Low-FODMAP: What Can You Actually Eat?

More than it looks like when you first lay the two lists side by side. When you're coeliac and also keeping to low-FODMAP, it can seem as though everything safe for one diet is banned by the other, but there is a solid core of everyday food that works for both: simple meat, fish and eggs, white rice and potatoes, and a good range of fruit and veg.

It can feel hard because the two diets work in completely different ways.

This comes up a lot, usually a few months after a coeliac diagnosis, when going strictly gluten-free has helped but not fully settled the gut and a dietitian has suggested trying low-FODMAP on top. It can be a demoralising place to be, so here are some useful tips.

How the two diets differ

Gluten-free, for a coeliac, is an absolute. No wheat, barley, rye etc, not even the traces from a shared toaster, because even a small amount sets off the immune reaction that damages the gut.

Low-FODMAP works on amounts. FODMAPs are a group of carbohydrates that draw water into the gut and ferment, causing bloating and discomfort. Most foods that contain them are fine in a normal serving but a problem in a large one. The low-FODMAP diet is also meant to be short: a few weeks of strict elimination, then a structured reintroduction to work out your own tolerances. It's not a diet you stay on forever.

For those with sensitivities and inflammation, gluten-free alone doesn't fix everything. A food can be completely gluten-free and still be loaded with FODMAPs.

Foods that are safe on both

These form a reliable base to build meals around, in normal portions:

• Protein: chicken, salmon, cod, beef and eggs, plain and unprocessed.
• Carbs: white rice, potatoes, quinoa, polenta and cornmeal, and buckwheat when you want a change from rice.
• Veg: carrots, courgette, cucumber and lettuce.
• Fruit: blueberries, kiwi, oranges and a firm, slightly green banana, one portion at a time.

Plain, single-ingredient foods are the easiest place to start. The fewer things on a label, the fewer places for gluten to hide and the less chance something high-FODMAP has been added.

To make food enjoyable, fresh herbs and spices such as cumin, paprika, turmeric and ginger are great. Spice blends and stock cubes often contain onion, garlic or wheat flour, so check the label. A splash of tinned coconut milk, or wine or rice vinegar, adds a lot too. Skip malt vinegar, which is made from barley.

The foods that are gluten-free but still high-FODMAP

These are the ones to avoid:

• Onion and garlic. Onion and garlic are both gluten-free and both high-FODMAP, and between them they turn up in nearly every sauce, gravy and stock. For most people they're the biggest low-FODMAP problem. Garlic-infused oil gets round it, since the FODMAPs don't cross into the oil, and the green tops of spring onions give a milder onion flavour.
• Pulses. Chickpeas, lentils and butter beans are naturally gluten-free but high-FODMAP.
• Some fruit. Red apples, pears, grapes and spotty, overripe bananas are gluten-free but high in FODMAPs. Kiwi, oranges and a handful of blueberries sit far better.
• Gluten-free bread and baking. A gluten-free loaf is sometimes made with chicory root fibre (inulin) or apple and pear concentrate, both high-FODMAP, so a bread that's fine for a coeliac can still upset the gut. Worth a read of the ingredients, and check the label each time, as recipes change.

Portion size matters

What makes low-FODMAP manageable is thinking about portion size rather than seeing it as an outright ban. Bananas show it well. A firm, slightly green one is fine. A ripe yellow one is fine as one small banana. Once brown spots appear it's high-FODMAP and best left out. Unsweetened almond milk is fine up to a glass (250ml), but much more than that and it's not. Gluten-free oats are fine in modest amounts, if your coeliac team has cleared oats for you. So before you strike a food off the list, check whether a smaller serving keeps it on.

If going gluten-free hasn't settled things

If you're a few months in, strict about gluten and still struggling, that doesn't mean you've done something wrong. It's common, and low-FODMAP on top is one of the standard next steps. The strict phase is meant to be short. You run the elimination for four to six weeks to calm things down, then reintroduce foods one group at a time, ideally with a dietitian, to find out which FODMAPs you actually react to and in what amount. Most people get a good number of foods back. It's worth asking whether something upstream is driving the sensitivity too, rather than treating each food as the problem on its own.

Keeping track of what's safe across both diets at once is the fiddly part. The ClearToEat food finder rates each food on gluten-free, low-FODMAP, low-histamine, lactose-free and SCD side by side, so you're not cross-checking separate lists. There's more on managing two overlapping diets in our low-FODMAP and histamine overlap post.

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This article is general information, not medical or dietary advice. Coeliac disease and FODMAP tolerance vary a lot between individuals, and low-FODMAP in particular should be done with a registered dietitian so it stays balanced and doesn't become more restrictive than it needs to be.