A fructan is a polymer (essentially a large molecule) of fructose molecules which store carbohydrates. They can have either a short and long chain length are known as fructoligosaccharides (FOS) and inulin respectively. Fructans (along with galactans) account for the ‘O’ in the FODMAP acronym.
A wide range of foods including artichokes, asparagus, leek, garlic, onion, wheat and ripe bananas. Scroll down for more extensive list.
Inulin (the long chain fructan), can be added to processed foods as a‘ functional ingredient’.
The addition of inulin increases the fibre content of the food product and acts as a prebiotics.
Cooking, drying, processing, sour-doughing, pickling, activating and sprouting foods (that already contain fructans) can increase or decrease that foods’ fructan content. Some examples:
We don’t have the enzymes to break down fructans in our small intestine. This results in:
Someone who has lactose intolerance can take lactase enzyme tablets to help break down any lactose that they have eaten.
It’s a different story if you need help breaking down fructans. There is no current product available on the market to do this job.
Eating an excessive amount of fructans can cause an increase in flatulence / gas and mild bloating in many of us.
However, for people with functional gut disorders (such as irritable bowel syndrome), even eating small amounts of fructans can cause significant gut issues.
This may include abdominal bloating, distension, pain, reflux, excessive wind and altered bowel movements.
Short answer. No. Wheat, barley, rye and oats are all sources of fructans. They also contain gluten.
All too often gluten gets mistakenly identified as the trigger if gut symptoms are experienced when these foods are consumed.*
As described earlier fructans are prebiotics. Prebiotics are classified as fibres that pass through the gastrointestinal tract undigested and stimulate the growth and/or activity of healthy gut bacteria.
Malabsorption of fructans is a pre-programmed bodily function vital to the health of our gut (e.g. producing butyrate). With this in mind, there can be several downsides to a diet restricted in fructans.*
If fructans are restricted in the diet they should ALWAYS be rechallenged once symptoms settle. There may be unnecessary dietary restrictions otherwise.
The rechallenge process is recommended to be conducted in partnership with your dietitian to ensure optimal liberalisation. .
*keep an eye out for future articles where these ideas will be expanded upon.
Fructans are fibres that are poorly digested and malabsorbed which can lead to gastrointestinal disturbance in sensitive people.
They are contained in a wide variety of foods and should only be restricted above levels that trigger gastrointestinal symptoms.
Always consult your dietitian before undertaking a fructan-restricted diet.
dried fruit (dried apricots, dried pineapple, dates, dried fig, dried mango, dried pawpaw, prunes, sultanas)
common banana (ripe)
blueberries (>1/2 cup)
fresh beetroot (>30g)
Brussel sprouts (>3 sprouts)
Savoy cabbage (>3/4 cup)
fennel (>1/4 bulb)
onion, shallots, spring onions
snow peas (<7 pods)
green peas (>1/4 cup)
zucchini (>1/2 cup)
wheat, barley, rye, oats (>1/2 cup)
cashews (>10 nuts)
black beans / baked beans (>1/2 cup)
red kidney beans, pinto beans, split peas
lentil burgers, vegetarian mince
silken tofu (>1/2 cup)
*Please refer to the Monash University low FODMAP app or low FODMAP booklet for a complete list of fructan-containing foods