Fructose malabsorption (dietary fructose intolerance)
After the diagnosis the most important task is to make an appointment with a registered dietician who is well versed in the subject of food intolerances. In addition, you will need to clarify whether you have any other food intolerance(s). Nearly 75% of those who have fructose malabsorption also suffer from lactose intolerance.
Some important terms:
First of all we need to clarify some terms since there have been a lot of misunderstandings in this area.
- The suffix -ose is used in biochemistry to form the names of sugars
- Enzymes are large biological molecules responsible for the thousands of metabolic processes that sustain life. They mostly break down bigger molecules to their smaller parts.
- Fructose is also known as fruit sugar. It's a monosaccharide, a single sugar molecule.
- Fructose malabsorption is the same as dietary fructose intolerance (DFI) or fructose intolerance! (Attention! Please also read our article on fructose malabsorption and hereditary fructose intolerance), but the term fructose malabsorption is more common
- Glucose is also known as dextrose or grape sugar. Also a monosaccharide.
- Sucrose, the most commonly used household sugar, is the same thing as granulated sugar (it is also referred to as saccharose; Sucrose is composed of one molecule of fructose and one molecule of glucose; it's a disaccharide). This also includes the finer-ground versions of the sugar we normally find in the sugar-bowl on the table or use for cooking, caster and icing sugar, but it will simply be referred to here as "granulated".
The first few weeks after diagnosis (fructose-restricted diet):
Fructose, sucrose and sorbite, sorbitol and other sugar alcohols need to be avoided completely in order to grant the intestines a period for rest and recuperation. It is important that during these first few weeks pulses, cabbage and too much dietary fibre is also avoided. After approx. 2 weeks these foods should gradually be reintroduced into the diet. It is important to keep the body hydrated (2-3 litres [0.5 gallons] of water per day) – water, herbal teas, no soft drinks or fizzy drinks, no alcohol).
It is wrong to assume that a person who suffers from fructose malabsorption is meant to avoid all fructose at all times. Fructose will be tolerated to a certain extent after the first weeks. Larger amounts can be tolerated when glucose is added. This only applies after the fructose-restricted diet.
Download Fructose content tables of foods tolerable during the fructose-restricted diet.
As soon as you feel better (which will happen pretty quickly!) and as soon as the symptoms have disappeared the fructose-restricted diet can be ended and a reintroduction or test phase can begin.
Book about the fructose-restricted diet
We highly recommend our book "Food Intolerances: Fructose Malabsorption, Lactose and Histamine Intolerance: living and eating well after diagnosis" if you're dealing with fructose malabsorption.
The test phase:
Depending on your mood you can start to eat foods that contain smaller amounts of fructose. You should always keep a close eye on your reactions. At this point it is possible to reintroduce small amounts of granulated sugar (white sugar) and add small amounts of glucose to foods that contain fructose. The test phase normally lasts for about a month and varies a great deal from person to person.
It is important to know that after the test phase you should NOT avoid fructose completely.
What it boils down to is this: Find out what YOU can tolerate und don't let others influence you!
Every person reacts individually to different foods and every person reacts differently to different foods from one day to the next!
Fructose is tolerated more easily when it is ingested on a full stomach rather than an empty stomach and is better tolerated in the afternoon!
What can I still eat when I suffer from fructose malabsorption?
Constant restraints make your life a misery. This raises the question: what can still be eaten after the fructose-restricted diet? You will find more information about how you can continue to observe a healthy and balanced diet in our article "A healthy diet despite fructose malabsorption".
Most fruits that contain more glucose than fructose and foods that have lower fructose contents in general. Fruits that are more likely to be tolerated are prickly pears, pineapples, bananas and tangerines (whereby the latter two have high sugar levels!). You can find a detailed list either here or in our download section.
Certain sugar alcohols can block the already malfunctioning transport system in the intestines of people affected by fructose malabsorption. These substances should thus be strictly avoided. Some of these substances are sorbitol (aka. glucitol) or mannitol (aka. Mannite, manna sugar. These substances tend to be used in chewing gum, sweets and ready meals. You can find the corresponding E-numbers in the ingredients dictionary. Xylitol and other sugar alcohols should also be avoided during the fructose restriced diet, but can be re-introduced in the test phase.
Normal granulated sugar is generally tolerated in small doses without a problem by most patients!
Granulated sugar (sucrose) is a disaccharide. It is composed of one molecule of fructose and one molecule of glucose. Because glucose makes it easier to absorb fructose, the sucrose is normally well tolerated (after the fructose-restricted diet, and mostly only in smaller doses!).
Wine contains relatively high levels of sorbitol and fructose and should therefore be avoided. Small amounts of dry white wines are often relatively well tolerated while sweeter wines are not tolerated very well. In general the following rule of thumb should be observed: The sweeter the alcoholic drink, the less likely it is going to be tolerated. With regard to alcohol, it is very important that you read the article "Fatty liver and fructose malabsorption"!
These substances should thus be avoided:
The E-Numbers are used in the European Union.
- Sorbitol (E420)
- Mannitol (E421)
- Isomalt (E953)
- Maltitol, maltitol syrup (E965)
- Fructose, fructose syrup, high fructose corn syrup
- Glucose syrup (depending on formula some can be tolerated very well)
These substances are unproblematic
- Xylitol (E967, xylite)
- Maltose, malt sugar
- Glucose, dextrose
- Sorbate - Sorbate is not the same as sorbite! Sorbate is a salt and is often used as a preservative. Potassium sorbate or calcium sorbate are mostly used (E202 and E203). Sorbate has been classified as safe for food intolerances.
Finally, another note from the "rumours" category:
Rumour: Sorbitol, xylitol... in toothpaste and mouth washes should be avoided!
Answer: No. This is incorrect!
The substances cause a problem when they have reached the gut. And if someone doesn’t intend to eat their toothpaste, then they don’t have anything to worry about! Quite the contrary, because the xylitol in these pastes has a caries-inhibitory effect it is actually highly advisable to use them!
Stryer, L., Biochemie, Specktrum Akademischer Verlag, 4. Auflage
NMI-Portal (Mag. Michael Zechmann)
Zechmann, M.; Masterman, G.; "Nahrungsmittel-Intoleranzen: Erste Hilfe beid er Diagnose", Berenkampverlag, 2012;