Some people who think they have a gluten sensitivity may actually have an intolerance to fructans.
What are Fructans?
Fructans are naturally occurring carbohydrates found in common foods like wheat, fruits, vegetables, and legumes. Fructans are made of a chain of fructose molecules.
In order to digest fructans, our small intestine must break the bonds between the fructose molecules. Only about 5-15% of fructans are digested in the small intestine and the rest travel to the large intestine where they are naturally fermented. This fermentation causes a little extra gas. However, when you do not have enough enzymes to break fructans down, the fructans can start to ferment in the large intestine in great quantity, causing very uncomfortable digestive symptoms. People with Irritable Bowel Syndrome may experience severe bloating, discomfort, pain and a change in bowel movements.
Fructans vs. Gluten
In 2018 there was a study done in Norway involving 59 people with gluten sensitivity who were tested over several weeks. The patients ate three different rounds of cereal bars. One round contained gluten, the second fructans, and the third was a placebo with neither. All the bars tasted the same, so the patients did not know which bar they were eating and they had a week free between bars to ensure any symptoms had resolved before moving onto the next type of bar. The researchers found that the patients only developed bloating and other symptoms of Irritable Bowel Syndrome after eating the bars containing fructans. The researchers concluded that people who find some relief by avoiding gluten may still have symptoms because they have problems with other foods such as fructans.
What Foods Contain Fructans?
High Fructan Gluten containing foods: wheat, spelt, rye and barley
High Fructan non-gluten containing foods:
- Fruits: watermelon, grapefruit, nectarine, persimmon, plums, pomegranate, ripe bananas, dates, prunes and raisins
- Vegetables: garlic, onions, shallots, leeks, asparagus, artichoke, beets, brussels sprouts, savoy cabbage, fennel and snow peas
- Legumes: kidney beans, black beans, lima beans, mung beans, navy beans, split peas, soy beans
- Nuts: cashews and pistachios
- Honey, agave nectar, inulin and chicory root
Should I Avoid Fructans?
If you have Irritable Bowel Syndrome symptoms, speak to your physician to determine if you would benefit from a strict short-term (4 weeks) fructan elimination diet followed by a slow reintroduction of fructans.