What FODMAPs are and why they matter in IBS
FODMAPs are short-chain carbohydrates found in many foods. In people with IBS, whose gut is more sensitive, the extra water and gas they produce stretch the bowel and cause pain, bloating, wind and diarrhoea or constipation. Vegetables contain different FODMAPs, such as fructans in onion and garlic, polyols in cauliflower and mushrooms, and excess fructose in asparagus.
Vegetables generally low in FODMAPs
- Carrots, parsnips, swede and turnip.
- Cucumber, lettuce, rocket and spinach.
- Tomatoes, including cherry tomatoes.
- Potatoes and, in small portions, sweet potato.
- Green beans, aubergine (eggplant) and bok choy.
- Kale, bean sprouts, radishes and olives.
- Courgette (zucchini) and red pepper in moderate portions.
- The green tops of spring onions and leeks, and chives.
- Fresh ginger and most fresh herbs.
Low FODMAP status depends on the serving size tested. Larger portions of some of these vegetables may contain moderate or high amounts.
Vegetables high in FODMAPs
- Onion (all types) and garlic, including onion and garlic powder.
- Leeks (white part) and the white bulb of spring onions.
- Cauliflower and button mushrooms.
- Asparagus and artichokes.
- Sugar snap peas and, in larger portions, green peas.
- Beetroot, Brussels sprouts, savoy cabbage and celery in larger portions.
Pulses such as beans, chickpeas and lentils are also high in FODMAPs, though small portions of canned, rinsed lentils and chickpeas are often tolerated.
Why portion size matters
FODMAPs add up. A vegetable that is low FODMAP in a small portion may become moderate or high in a larger one, and eating several moderate-FODMAP foods in one meal can add up to a high load. Broccoli, sweet potato, butternut squash and sweetcorn are examples where portion size makes a difference.
Using a reliable, regularly updated app helps check servings, since values are updated as more foods are tested.
Easy swaps for onion and garlic
- Use garlic-infused oil: fructans do not dissolve into oil, so the flavour comes without the FODMAPs.
- Use the green tops of spring onions and leeks, and chives.
- Add asafoetida (a small pinch) for an onion-like flavour; choose a gluten-free version if needed.
- Season with ginger, herbs, lemon, mustard and spices.
- Check stock cubes, sauces and ready meals, which often contain onion and garlic.
Low FODMAP vegetable meal ideas
- Roasted carrots, parsnips and potatoes with rosemary and garlic-infused oil.
- Stir-fry with bok choy, green beans, red pepper, bean sprouts and ginger.
- Spinach and tomato omelette.
- Salad with lettuce, cucumber, tomato, olives and feta.
- Aubergine and courgette bake with tomato sauce made without onion and garlic.
Low FODMAP snacks and bread
- Carrot and cucumber sticks with a small portion of peanut butter or lactose-free yoghurt dip.
- Rice cakes, plain popcorn and a small handful of nuts such as walnuts, macadamias or peanuts.
- Lactose-free yoghurt, hard cheese, firm bananas, kiwi, oranges and strawberries in suitable portions.
- Traditional sourdough spelt or white bread, which is often lower in fructans than standard wheat bread.
- Gluten-free bread, checking labels for high FODMAP ingredients such as inulin, honey or soy flour.
Elimination, reintroduction and personalisation
The low FODMAP diet has three phases: a strict elimination of 2 to 6 weeks, a reintroduction phase testing one FODMAP group at a time, and a personalised long-term diet that includes as many foods as tolerated. Most people only react to some FODMAPs, and staying on a strict diet long term can reduce fibre and affect gut bacteria.
A dietitian experienced in IBS makes the process easier and safer. See also why am I so bloated.
Keeping enough fibre
Cutting out high FODMAP foods can reduce fibre intake and worsen constipation. Low FODMAP sources of fibre include oats, quinoa, brown rice, potatoes with skins, carrots, kiwi, chia seeds and linseeds in moderate amounts. Drinking enough water helps fibre work.
When to see a doctor first
- Blood in the stool or black stools.
- Unexplained weight loss.
- Change in bowel habit after age 50 or a family history of bowel cancer or coeliac disease.
- Waking at night with diarrhoea or pain.
- Anaemia or persistent vomiting.
IBS should be diagnosed by a doctor, and coeliac disease ruled out, before starting a low FODMAP diet.
Key points to remember
- Many vegetables are low FODMAP in normal portions.
- Onion, garlic, cauliflower, mushrooms and asparagus are the main ones to swap.
- Portion size matters, and FODMAPs add up across a meal.
- The diet is short term, followed by reintroduction, ideally with a dietitian.
Questions about low FODMAP vegetables
These answers are general information and do not replace an examination or individual medical advice.
Which vegetables are low FODMAP?
Carrots, cucumber, lettuce, spinach, tomatoes, potatoes, green beans, aubergine, kale and bok choy, among others, in normal portions.
Is broccoli low FODMAP?
Broccoli heads are low FODMAP in moderate portions; larger servings contain more FODMAPs.
Are tomatoes low FODMAP?
Yes, fresh tomatoes are low FODMAP in normal portions.
Can I eat onion on a low FODMAP diet?
Not during elimination, but you can use spring onion and leek greens, chives and garlic-infused oil.
Are cooked vegetables lower in FODMAPs?
Cooking does not remove most FODMAPs, though some may leach into cooking water.
What are good low FODMAP snacks?
Rice cakes, popcorn, a small handful of nuts, lactose-free yoghurt and carrot sticks.
Is sourdough bread low FODMAP?
Traditionally made spelt or white sourdough is often lower in FODMAPs than standard bread.
Sources
This guide is for general information and does not replace medical advice. How a problem is diagnosed and treated depends on your examination and medical history. If you think you have an emergency, contact your local emergency services.