Fructan Intolerance: Symptoms, High-Fructan Foods and How to Manage It

01What

What are fructans?

Fructans are a type of carbohydrate made of fructose units linked together, sometimes with a glucose at the end. They include fructo-oligosaccharides and inulin. They act as prebiotic fibres, feeding beneficial gut bacteria, which is generally healthy. But because they are fermented rather than absorbed, they produce gas and draw water into the bowel. Fructans are one of the main groups in the FODMAP family (fermentable oligosaccharides, disaccharides, monosaccharides and polyols).

02Symptoms

Symptoms of fructan intolerance

• Bloating and abdominal swelling.
• Excess wind.
• Abdominal pain or cramping.
• Diarrhoea, constipation or alternating bowel habit.
• Nausea in some people.
• Symptoms usually appear a few hours after eating and can last into the next day.
• Unlike coeliac disease, fructan intolerance does not damage the gut lining.

03Foods

High-fructan foods

• Grains: wheat, rye and barley, including bread, pasta, couscous, crackers and cereals.
• Vegetables: onions, garlic, leeks (white part), shallots, spring onions (white part), artichokes and asparagus.
• Legumes: chickpeas, lentils and some beans, especially in larger portions.
• Fruit: watermelon, nectarines, white peaches and some dried fruits.
• Nuts: cashews and pistachios.
• Additives: inulin, chicory root fibre and fructo-oligosaccharides added to “high-fibre” products.

04Low

Lower-fructan alternatives

• Grains: rice, oats, quinoa, buckwheat, millet, corn, potatoes and gluten-free bread (check for inulin).
• Sourdough spelt bread: fermentation reduces fructans, often tolerated in small amounts.
• Flavour swaps: garlic-infused oil, chives, the green part of spring onions and leeks, ginger and herbs.
• Vegetables: carrots, courgettes, peppers, spinach, tomatoes, cucumber and green beans.
• Fruit: bananas, oranges, kiwi, strawberries, blueberries and grapes.
• Nuts and seeds: peanuts, walnuts, pumpkin seeds and macadamias.

05Gluten

Fructans or gluten?

Many people who feel better avoiding wheat assume they are sensitive to gluten. However, wheat contains both gluten and fructans. In a randomised, double-blind crossover trial, people with self-reported non-coeliac gluten sensitivity had more symptoms after eating fructans than after eating gluten or placebo. This suggests that, for many people, fructans may be the main trigger. Coeliac disease, an autoimmune reaction to gluten, must be ruled out first; see gluten intolerance tests.

06IBS

Fructan intolerance and IBS

Fructans are a common trigger for people with irritable bowel syndrome, who often have increased gut sensitivity to normal amounts of gas and stretch. A randomised controlled trial found that a diet low in FODMAPs reduced overall IBS symptoms, bloating, pain and wind compared with a typical diet. The NHS lists the low-FODMAP diet as an option for IBS, ideally with the help of a dietitian. Our guide to the low-FODMAP diet for beginners explains the approach.

07Diagnosis

How fructan intolerance is diagnosed

• There is no reliable blood test or routine breath test for fructan intolerance.
• First, a doctor should rule out coeliac disease while you still eat gluten.
• A dietitian may guide a low-FODMAP elimination diet for two to six weeks.
• Foods are then reintroduced one group at a time, including a specific fructan challenge.
• Symptoms returning with fructan foods suggest fructan intolerance.
• Many people find they tolerate small amounts.

08Manage

Managing fructan intolerance long term

The goal is not to avoid fructans forever, but to find your personal threshold. Long-term strict avoidance reduces prebiotic fibre and may affect gut bacteria. Most people can include some fructan-containing foods, especially in smaller portions or spread through the day. Including other fibres, such as oats, linseeds and low-FODMAP fruit and vegetables, helps maintain gut health. More dietary ideas for IBS are in diet for IBS.

09Day

A sample low-fructan day

• Breakfast: porridge oats with lactose-free milk, banana and blueberries.
• Lunch: rice salad with chicken or tofu, carrots, cucumber and peppers, dressed with garlic-infused oil.
• Snack: a handful of walnuts and an orange.
• Dinner: salmon with potatoes, green beans and courgettes, flavoured with herbs and the green part of spring onions.
• Dessert: strawberries with plain yoghurt.

10Cases

Three common situations

• Bloating after bread and pasta, coeliac test negative: consider a dietitian-led trial of reducing fructans.
• IBS symptoms after meals with onion and garlic: try garlic-infused oil and chives.
• Bloating after “high-fibre” bars: check labels for inulin or chicory root.

11Labels

Reading labels for fructans

• Look for wheat, rye and barley in the ingredients list.
• Check for onion powder and garlic powder in sauces, stocks, crisps and ready meals.
• Watch for inulin, chicory root, fructo-oligosaccharides (FOS) and oligofructose.
• “Gluten-free” does not always mean low in fructans; check for added fibres and onion or garlic.
• Choose plain foods and add your own herbs and spices.

12Summary

Key points to remember

• Fructans are found in wheat, onions, garlic and many other foods.
• They can cause bloating and pain, especially in IBS.
• Rule out coeliac disease before cutting out wheat.
• A dietitian-led low-FODMAP approach helps find your tolerance.