What foods are low in fructans?

Some people who think their bodies are sensitive to gluten may, in fact, be intolerant to fructans, polymers of fructose that occur in large quantities in wheat products.

This naturally occurring carbohydrate also is found in many fruits, vegetables and legumes. So if someone truly has a fructan intolerance, they would benefit from cutting out more than just foods that contain gluten.

However, if you suspect that a fructan or gluten intolerance is causing digestive issues, it’s best not to immediately eliminate either of the substances from your diet forever — the foods containing fructans and gluten can be beneficial and should be included in your diet if you’re not actually intolerant.

Can a new portable tester detect gluten?

Here’s what you need to know when considering whether to avoid fructans:

What foods contain fructans?

Wheat and onions are the biggest sources of fructans in most Americans’ diets. However, there are other foods high in fructans, falling into two categories: those that also contain gluten and those without gluten.

Gluten-containing, high-fructan foods: wheat, spelt, rye and barley.

High-fructan foods that don’t contain gluten include:

• These fruits: watermelon, grapefruit, nectarine, persimmon, plums, pomegranate, ripe bananas, dates, prunes and raisins
• These vegetables: onions, shallots, leeks, asparagus, artichoke, beets, Brussels sprouts, savoy cabbage, fennel and snow peas
• Kidney beans, black beans, lima beans, mung means, navy beans and split peas
• Cashews and pistachios
• Garlic and inulin (aka chicory root) and some soy products

What does a fructan intolerance look like?

People who have trouble digesting fructans may experience gas, bloating, belching, constipation or diarrhea.

As a registered dietitian nutritionist, I see patients with digestive issues quite frequently.

Some people are bothered by their symptoms significantly enough that they miss work or school, but others experience symptoms more as a nuisance rather than as an interruption to their day.

Digestive symptoms can almost always be linked back to diet, but fructan intolerance is just one of many possibilities when you experience these types of symptoms.

How do I determine if I should avoid fructans?

Someone with irritable bowel syndrome (IBS) or IBS-like symptoms might benefit from either a short-term fructan elimination in their diet (where they would slowly reintroduce fructans) or a low-FODMAP diet (also with a subsequent reintroduction).

The low-FODMAP diet, while fairly complex, has been studied and found to be effective for IBS.

FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols. Fructans fall into the oligosaccharides group. A low-FODMAP diet avoids foods high in these sugars and fibers because they’re easily fermented by intestinal bacteria, leading to IBS symptoms.

If you suspect a fructan intolerance, the best approach is to avoid fructans for two to four weeks. If digestive symptoms improve during that time, then you’ll know there’s a problem digesting fructans. After the initial elimination, gradually add fructan-containing foods back into your diet one at a time to determine your individual intolerance.

Why shouldn’t I eliminate fructans altogether if I determine I have an intolerance?

Fructans can be a beneficial part of the diet — they can be considered prebiotic, meaning they feed the good bacteria in the gut. Additionally, fructans have been linked to improvements in blood glucose, triglycerides and the improvement of lipid metabolism and immune function.

A diverse diet supports the most diverse gut microbiome, which in turn supports good health overall.

Furthermore, stress and anxiety over having to avoid certain foods can lead to an increase in the symptoms we’re trying to improve with a low-FODMAP or low-fructans diet. And social isolation related to unnecessary dietary restrictions can be harmful.

A final word on diagnosing food intolerances or sensitivities

Don’t continue to avoid foods high in FODMAPs or fructans indefinitely. Elimination should always be followed by a careful, systematic reintroduction. Reintroduction helps us identify which fructan-containing foods are most bothersome and in what quantities.

Keep a detailed food and symptom diary to help you determine which foods are best avoided long-term. Consult with a registered dietitian nutritionist if you need help sorting through the details.

#BuckeyeBites recipes from our experts

Understanding what fructans are and how they fit with the low FODMAP diet can be tricky. Fructans like to lurk in a variety of foods, from fruit and veggies right through to cereal grains. They are also added to processed foods. This article is going to explain what they are and how to avoid them.

What are fructans and why are they a problem?

Fructans are oligosaccharides and polysaccharides that store carbohydrates in a variety of vegetables, for example, onions, garlic and artichokes, fruits such as bananas, and in cereals (1 2 3). Unripe common bananas contain lower levels of fructans and are safe to eat in small serves (1 small to medium unripe banana), however as the bananas ripen the fructan levels increase to a high FODMAP level. In the FODMAP acronym fructans belong under the ‘O’ for oligosaccharides. Humans lack the enzyme needed to break down the fructose molecule chains that fructans are made of, which means they end up being malabsorbed in our small intestines (1 2). The fructans are then fermented by the gut bacteria, which can cause gas, bloating, pain, reflux, and altered bowel movements (2 3 4).

There are two types of fructans:

• Fructans with shorter chain lengths (2-9 units) are called fructo-oligosaccharides (Oligos-FOS for short)
• Fructans with longer chain lengths (10 units or greater) are called inulin. Inulin has already been discussed in depth in a previous article – you can read more about inulin here.

(2)

For the purpose of this article, there will be no differentiation between the types of fructans. Additionally, the different types of fructans are not labeled separately in the Monash University Low FODMAP app (3).

Fructans consist of soluble fibre (4). Adding fructans to processed food is a growing trend in the food manufacturing industry. This is because fructans (especially inulin) are considered a functional ingredient that can increase fibre content of processed food (4). The fermentable fibre is meant to help the growth of ‘friendly’ gut bacteria because they act like prebiotics (1 4), which is great for normal people but not so great for people who can’t tolerate FODMAPs! This means you should check the labels of processed foods and supplements for inulin, added fibre, and other fructans.

Where are fructans found?

Plants use fructans as storage carbohydrates. This means fructans can be found in a wide range of fruits, vegetables and cereals (1). Most types of beans/pulses/legumes and some nuts are also high in fructan containing oligosaccharides (3). One of our major sources of fructans is wheat, which means cutting out wheat can dramatically decrease our fructan intake (1 4). Below is a table of high FODMAP foods that contain fructans. This table is by no means intended to provide a full list of fructan-containing foods, but to show how many different foods contain fructans. For a more comprehensive list of fructan-containing foods and their FODMAP levels, please refer to the Monash University phone app or low FODMAP booklet.

High FODMAP Foods Containing Fructans (non-exhaustive list)

(Source: Muir et al., 2009; Monash University App, 2017)

Do different foods have different fructan levels?

Different foods can contain different levels of fructans. It is also important to note that cooking, manufacturing or refining processes, and the fermentation of foods can change their FODMAP rating and fructan levels. For example, spelt sourdough bread is lower in FODMAP levels as the yeasts use the fructans during the fermentation process (5). Another example of changes in fructan levels is the drying of fruit. The drying process concentrates the sugar present in the fruit and can increase the fructan levels, even if these fructan levels weren’t detectable in the fresh fruit (5). The processing of cereal grains can also change the fructans levels in the end-products.  The tables below indicate how fructan levels can change between foods.

Table One: High FODMAP Vegetables Containing Fructans

(Source: Muir et al., 2009)

Table Two: Cereals Containing Fructans

(Source: Verspreet et al., 2015)

Reintroduction of Fructans

Section Updated on 21/04/2016

After the elimination phase of the diet, fructans can be re-challenged and reintroduced. Fructan levels can vary greatly between different fruits, vegetables, and cereal grains. This means you need to test one to two foods in each of the different fructan groups to find your tolerance levels (8). FODMAP reintroduction specialist, Lee Martin (RD), recommends that you re-challenge each fructan group separately:

(Table Information Sourced from: Martin, 2015)

For more information, you can find our overview of the reintroduction phase here. Otherwise, join our FODMAP Made Easy programme for a complete guide on reintroducing FODMAPs and expert support.