Fructose Intolerance

Fructose Intolerance

Welcome to our Fructose Intolerance FAQ. Here we aim to answer all your questions about fructose intolerance, what it is, what causes it and what you can do about it.

Like our other intolerance FAQ’s, we will be updating this one as new questions and information become available. If you have any questions that aren’t answered here please be sure to email them through to us.

Let’s get started by taking a look at what fructose is.

What is Fructose?

Like lactose, fructose is a type of sugar that can be difficult to digest. Fructose is most commonly found in fruit, but is also in honey, some vegetables and grains.

It is a single unit of sugar, which means that it doesn’t need to be broken down by enzymes before the body can absorb it. However, the body can’t absorb an unlimited amount of fructose, in average adults the amount that can be absorbed ranges from 25 to 50gm of fructose in

one sitting. Anything over this digestible quota travels on into the large intestine, causing a rapid amount of fermentation and extra fluid accumulation. Bloating after eating, gas and loose stools are common when this happens, however, this is not fructose intolerance as it occurs in most people when they eat to much fruit or fructose-containing foods (over 50gm in one sitting).

When these same symptoms occur with only a small amount of fructose consumption that would NOT affect most people, then it can be named fructose intolerance.

What is Fructose Intolerance?

Fructose intolerance occurs when the molecule that transports fructose in our digestive system doesn’t work properly. The fructose can’t be absorbed in the small intestine, so when it reaches the colon the bacteria there has a field day. These bacteria ferment the fructose, and this causes excessive gas and the related bloating, wind, pains and diarrhoea.

Commonly found alongside fructose malabsorption is lactose intolerance and also gastro-oesophageal reflux disorder (GORD). If you’ve been diagnosed with GORD, but don’t know why it’s happening, it’s worth seeking out a diagnosis for food intolerances.

Our hair test is a very simple and non-invasive way of doing this, you can read more about it here:

What are the symptoms of fructose intolerance?

As we have briefly touched on already, some of the most common symptoms of fructose intolerance include:
  • Digestive bloating
  • Gas and wind pains
  • Diarrhea
Some other symptoms include:
  • Severe fatigue – due to the inflammation caused by consuming fructose
  • Nausea
  • Constipation can also be an issue
  • Heartburn and reflux
  • Headaches and migraines
  • Nutrient deficiencies such as iron

What causes you to develop fructose intolerance?

The cause of fructose intolerance is an accumulation of excessive fructose in the large intestine. The reason for this build-up can be a deficiency in ‘fructose carriers’, which are cells on the intestinal wall that direct fructose to its destination. If you don’t have enough of these cells, the gut microbiome (bacteria) have a wonderful time digesting this fructose sugar when it reaches your large intestine and creates a large amount of gas, bloating, pain and diarrhea.

Other things that can cause you to experience fructose intolerance include:

  • Irritable bowel syndrome
  • Poor gut bacterial balance and SIBO – small intestinal bacterial overgrowth
  • Poor diet, with a high intake of processed foods and high sugar foods
  • High stress levels (read more about foods and stress)
  • Any existing inflammation
  • Fatty liver

These listed causes are not necessarily long term, and once addressed the fructose intolerance may also reduce.

Are there any risk factors for developing fructose intolerance?

Yes, there are risk factors for developing fructose intolerance, with the main ones listed below:

IBS is a large risk factor, in fact, up to 70% of people with IBS also have fructose malabsorption.

Interestingly, when the IBS is treated, the fructose malabsorption may also disappear.
Other digestive conditions also predispose you to fructose intolerance, these include things like:

  • Crohn’s disease
  • Colitis
  • SIBO (you can read about this in our article titled SIBO and histamines)
  • any other bacterial disturbances such as candida, fungal infections etc.

Is fructose intolerance hereditary?

Like most food intolerances, fructose intolerance can run in families. However, this isn’t always the case, and we see it more often is caused by poor gut health and digestive disturbances.

There is a more serious genetic condition called ‘Hereditary Fructose Intolerance’, which is when the body doesn’t make any of the enzyme needed to break down fructose. This one does run in families. It is quite a rare condition and can lead to some very serious complications if the person is not following a strict fructose-free diet, including liver failure at the extreme.

How is Fructose Intolerance diagnosed?

Diagnosis of suspected fructose intolerance can be done via a breath test, very similar to lactose testing. A fructose solution is drunk by the patient, and the amount of gas released on the breath is measured over the next few hours. The results determine a diagnosis, with large amounts of gas signifying fructose intolerance.

A much more non-invasive option is to take our hair test to detect any intolerances you may have.


Can fructose intolerance be cured?

No, there is no cure. You don’t have to live with the painful symptoms though, as the condition can be very well managed.

Please read the next section for information on how to manage your fructose intolerance naturally.

How can I manage my fructose intolerance?

Fructose intolerance can be well managed through diet alone and enhanced through gut healing principles that a holistic nutritionist or naturopath can guide you through.

Following a Low FODMAP diet is the number one strategy to manage fructose intolerance initially. FODMAPS is an acronym for ‘Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols’, which are the scientific names given to groups of sugars or carbs based on their structure.

This type of diet is a great short term strategy, but it is important to follow it for a short time only and then reintroduce FODMAP foods slowly with the guidance of a FODMAP trained dietitian or nutritionist. Everyone will have a different level of tolerance to fructose-containing foods, and the end goal of a low FODMAP diet is to find your personal tolerance level. This allows you and your dietitian/nutritionist to create a personalised diet just for you.

Another management tool is to seek advice from a Naturopath or holistic doctor to determine whether SIBO or another gut condition is causing your fructose intolerance. If this is the case, treating the underlying condition will also treat the fructose malabsorption you are experiencing.

Specific probiotics, enzymes and gut-healing herbs may be used by your clinician to heal your digestive tract and relieve fructose intolerance at the same time too.

Acupuncture has also been successful in some patients in treating fructose intolerance and digestive issues.


Which foods should I avoid if I am fructose intolerant?

If you are found to have a fructose malabsorption issue, it is strongly advised that you avoid any foods that are known to be high in fructose, or those foods that contain fructans, which are chains of fructose joined together. Reducing your fructose load will reduce your symptoms. Over time you may find that you can still tolerate certain foods that contain fructose, especially those low in the sugar.
Food High in FructoseFoods containing Fructans
HoneyGlobe artichoke
Pears and nashiesOnions, spring onions, shallots
Watermelon and honeydew melonWheat, rye & barley in large amounts
High fructose corn syrupAsparagus
Tinned fruit, fruit juicesGreen Beans
Coconut milk and creamBeetroot

Other fruits are vegetables are quite safe to consume, and these include:

  • Berries, bananas, oranges and rhubarb.
  • Black beans, broccoli, celery, chickpeas, green peppers, haricot beans, kidney beans, leafy greens, lentils, mushrooms, spinach.

These lists provide a good guide to get started, however it is highly individual and 2 people with fructose intolerance will most likely react differently to the same foods. It is about trial and error and figuring out which foods your body can tolerate, and which it can’t. It is called the elimination diet.

How common is fructose intolerance?

Fructose intolerance is a common condition.

It is believed that it affects up to 1 in 3 people or just over 30% of the population.

Does fructose in your diet cause diabetes?

Because fructose is a sugar, it does increase your blood sugar upon consumption, and if this is done regularly then over time it can contribute to the formation of Type 2 diabetes. Studies are supporting this, linking the consumption of high amounts of fructose to type 2 diabetes, metabolic syndrome, obesity and other metabolic disease states.

High fructose corn syrup is particularly damaging concerning diabetes and metabolic effects.

Does fructose cause you to be overweight?

If it is consumed in excess then yes absolutely. Any excess carbohydrate or sugar in the body will be stored as fat, contributing to weight gain and obesity.

In the case of fructose, a lot of the excess is also stored in the liver and causes a liver disease known as ‘fatty liver’. In years gone by only alcoholics were diagnosed with fatty liver, but now with the huge amount of processed foods and sugar being consumed daily, we are seeing even children being diagnosed with the condition.

Does fructose intolerance cause depression or anxiety?

Yes, it is believed that fructose intolerance does play a part in depression and anxiety for some people.

There is mounting evidence that shows fructose consumption can lower tryptophan levels in the body. Tryptophan is essential in the creation of serotonin and melatonin, which are two very important neurotransmitters. Without adequate levels of serotonin and melatonin, depression and other mood and nervous system disorders (hello insomnia) will occur.

What is High fructose corn syrup and is it bad for me?

High fructose corn syrup is derived from corn, as the name suggests, and is a sweetener used very heavily in processed foods and soft drinks. It has both fructose and glucose in it, just like table sugar does, but it is in liquid form.

Yes, it is bad for you, as it is pure sugar with a very high amount of fructose. This means that it skyrockets blood sugars and causes insulin resistance, is implicated in diabetes, metabolic syndrome and obesity, and gives your liver a very hard time.

Our liver is the only organ that processes fructose, and when the fructose load is too high the liver turns this excess fructose into fat. It’s stored within the liver and creates what is known as ‘fatty liver’, which is a condition that severely impairs the functioning of the liver itself.

Why is fructose intolerance on the rise?

The biggest reason why fructose intolerance has become such a big problem coincides with the massive increase in sugar consumption. Compared with 50 years ago, our diets on average have 1000 times more fructose today, mainly from high fructose corn syrup.

Processed foods and soft drinks filled with high fructose corn syrup have a big part to play in the problem, as the human body is not made to tolerate these high amounts of fructose and other sugars. If we keep ingesting high amounts of it daily then problems arise, not the least of which is fructose intolerance.