Intolerance Lab

Visit our page for more information on Easy Affordable at Home Intolerance Testing

Fructose Intolerance FAQ

Welcome to another one of our FAQ’s. This time we are delving into Fructose intolerance and all of the ins and outs of this disruptive condition.

We will be discussing what fructose is, how fructose intolerance works, what the main symptoms are, the causative factors, the risk factors for developing it, whether there is a hereditary component, how you can get a diagnosis, how you can best manage your fructose intolerance and answering some other curiosities about the condition.

Please read on to learn all about fructose intolerance with us.

What is Fructose?

Essential fructose is a single unit sugar that is mostly found in fruits, but also in some vegetables, grains and honey.


The body can easily absorb fructose due to its single unit structure, which means enzymes are not needed to break it down further. However, the human body only has a limited capacity for fructose absorption, with the range

being 25gm to 50gm per sitting. Anything over this amount will cause digestive upset in MOST people. The extra fructose that can’t be digested travels on into the large intestine and causes all the familiar symptoms of gas, bloat, discomfort and diarrhea. This isn’t fructose intolerance though because it happens in almost everyone. When the same symptoms occur with a small amount of fructose ingestion that would not upset most people, then it’s called fructose intolerance.

What is Fructose Intolerance?

Fructose intolerance is a condition where ingested fructose can’t be absorbed in the small intestine which is where it usually gets absorbed. This can be due to a lack of the transporting molecule, so fructose can’t get to where it needs to go. Therefore it continues along the digestive tract and causes a very large amount of fermentation in the colon. Large amounts of gas, bloating, gut pains and loose stools then occur.

Lactose intolerance and gastro-oesophageal reflux disorder (GORD) are also very commonly found alongside fructose malabsorption. If you have had a diagnosis of GORD it’s a good idea to have some food intolerance testing done to rule out any possible food causes.

Our hair test is non-invasive and will give you an excellent indication of which foods may be causing issues for you. You can find out more about it HERE:

What are the common symptoms of fructose intolerance?

Fructose intolerance mainly affects the digestive system, but there are also some non-digestive symptoms. We will take a look at both here.
Digestive symptoms:
  • Bloating
  • Excessive gas
  • Wind and stomach pains
  • Diarrhea
  • Constipation
  • Heartburn
  • Reflux – also GORD as mentioned above
Non-digestive symptoms include:
  • Severe fatigue – most food intolerance can cause this, not just fructose
  • Nausea is another common one
  • Headaches and migraines are also common with fructose intolerance
  • Nutrient deficiencies such as iron can also occur due to excessive inflammation in the gut

How do you develop fructose intolerance?

Fructose intolerance can develop for several reasons. Sometimes it occurs as a side effect of something else, such as in IBS sufferers. In this case the IBS damages the digestive tract, and so many food intolerances can develop as a result of this. The same situation can happen with small intestinal bacterial overgrowth (SIBO).

People can also have a lack of fructose carrying molecules in their intestinal wall, which means that fructose can’t be directed to where it needs to go. The result of this is a build-up of fructose in the large intestine (LI), with a huge amount of fermentation occurring when it reaches the bacteria in the LI and colon. This is when we see all of the characteristic bloating, wind, pains and diarrhea.

Further factors that can be instrumental in developing fructose intolerance include having a diet filled with highly processed and high sugar foods. Giving the body over and above the amount of sugar it can naturally handle causes many different disease states, with fructose intolerance amongst them.
High-stress levels can be causative, as this degrades the digestive tract and causes elevated inflammation.

Fatty liver can also play a part in developing fructose intolerance. This is because the liver is the main processor of fructose in the body, and if it is not working properly then any additional fructose won’t be handled well.

What are the risk factors for developing fructose intolerance?

Similar to the last question, the risk factors include already existing digestive disorders.

IBS is a big one, with 70% of IBS sufferers also having fructose intolerance.

Chron’s disease, SIBO, Colitis etc also predispose you to develop fructose intolerance, due to the disturbance in your digestive tract. When the underlying condition is treated, the fructose intolerance often disappears as well.

Candida and other systemic fungal infections can also predispose you to develop fructose intolerance, but likewise, once they are treated your intolerance may also correct itself.

Is fructose intolerance genetic?

Most food intolerances can run in families, but it doesn’t always happen. More often than not with fructose intolerance, it is caused by other digestive disorders or poor gut health.

‘Hereditary Fructose Intolerance’ is a very serious and separate condition from fructose intolerance. This is genetic, and people with this condition have none of the enzymes the body needs to break down fructose. It can lead to very serious health complicationsand needs to be managed with a strict fructose-free diet.

How can you diagnose Fructose Intolerance?

A diagnosis of fructose intolerance is usually done via a Hydrogen Breath test, just the same as lactose intolerance testing. In this case, though a fructose solution is ingested, and the amount of hydrogen produced and expelled on the breath is measured. If the result is high then a diagnosis of fructose intolerance is confirmed.

Our hair intolerance test will also give you a fructose intolerance result in a much less invasive way. You can find out more info HERE.

Is there a cure for fructose intolerance?

Unfortunately no, there is no known cure.

However, there are ways to manage fructose intolerance so that you can be symptom-free and live a wonderful quality of life. We will have a look at some of them in the next section.

How do you manage fructose intolerance?

Dietary intervention is the best way to manage fructose intolerance, and in fact, the symptoms can be removed through this method alone. Supporting nutritional efforts with gut-healing protocols can add to the benefits and healing as well.

The first step is to learn about FODMAPS, which stand for Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols. These are the fancy scientific names given to different sugars based on their structures.

Following a low FODMAP diet has positive effects and is the first-line treatment option for the fructose intolerant. However, despite its success at removing symptoms, it should only be followed strictly for a short time, up to 6 weeks. After this time its important to reintroduce some low fructose foods back into the diet, and find your tolerance level of each food. This needs to be done with a qualified nutritionist or FODMAP trained dietitian, which removes the overwhelm and helps give you a clear path to follow.

Further to this, it’s important to seek advice from a holistic health practitioner to determine the underlying cause of your fructose intolerance. If it is a digestive issue such as SIBO, IBS etc, then treating this condition with the guidance of your chosen practitioner will help reduce and potentially remove your fructose intolerance symptoms as well.

Other tools such as acupuncture, specific strains of probiotics and enzymes have helped to manage the condition, but these need to be used under the guidance of your holistic practitioner.

Foods to avoid for the Fructose Intolerant

When diagnosed with fructose intolerance, it’s advised that you avoid all foods that are high FODMAP foods, particularly those with high fructose or fructan content. This will help to greatly reduce your symptoms.
This first list is foods known to be high in fructose:
  • Apples, pears and nashie pears
  • Melons – watermelon, honeydew
  • Mangos
  • All tinned fruits and fruit juices
  • Honey
  • High fructose corn syrup and all foods containing this. Check the labels
These foods are high in fructans
  • Garlic
  • Artichokes
  • Onions, leeks, spring onions, shallots
  • Asparagus
  • Green beans
  • Beetroots
  • Cucumbers
  • Gluten-containing grains wheat, rye and barley also contain fructans and can cause issues if eaten in large amounts
These lists are not exhaustive, but they do provide an excellent starting point. It’s imperative to keep in mind that fructose intolerance is highly individual, and your tolerance level to particular foods will be different from your friend who also has fructose intolerance. Trial and error and finding your tolerance levels is very important on this journey.

Is fructose intolerance common?

Yes, it is a very common condition. Just over 30% of the population is believed to be affected by it.

Does consuming fructose cause Diabetes?

It can contribute to developing Type 2 diabetes. A diet with high amounts of fructose has scientifically been linked to metabolic conditions including Type 2 diabetes, Syndrome X, Obesity and other disease states.

As far as foods go, the worst offender concerning diabetes is by far high fructose corn syrup. It is found predominantly in junk food and soft drinks, who’s consumption has no positive effects on health and wellbeing and is known to contribute to metabolic disease states.

Does fructose cause obesity?

Most things consumed in excess will contribute to ill health, and as fructose is a type of sugar then yes it will contribute to weight gain if overeaten. The same is true of any carbohydrate that is eaten to excess.

Consuming a high fructose load also contributes to fatty liver, which is a disease state that interrupts the function of your liver as it becomes infiltrated with fatty deposits. Eating large amounts of processed or sugary foods and also wheat products is the biggest factor in developing fatty liver.

Are depression and anxiety linked to fructose intolerance?

Yes! It can downgrade the production of serotonin and melatonin, which are the neurotransmitters that create healthy moods and wellbeing. It does this by lowering tryptophan levels in the body, which are an essential part of creating enough serotonin and melatonin. Without adequate levels of these neurotransmitters, many mood and nervous system issues arise.

The facts on High fructose corn syrup (HCF)

HCF is a liquid sweetener derived from corn. It is cheap to make and is heavily used in the processed foods industry. Soft drinks and sugary snack manufacturers are the biggest users of HCF. It contains glucose and fructose just as table sugar does.

It is bad for the body because it is pure sugar without any of the vitamins and minerals that come with sugar found in its natural form. It has a very high amount of fructose, so it has highly damaging effects on blood sugar. It’s implicated in insulin resistance, the development of type 2 diabetes, metabolic diseases and diabetes. As previously mentioned it is also known to cause fatty liver, severely impacting the function of the liver.

Why is fructose intolerance so common?

Compared to fifty years ago we are consuming up to 1000 times more fructose today, and it’s believed that this is mainly due to high fructose corn syrup consumption. Our bodies cannot tolerate such a high sugar and fructose load, and the development of fructose intolerance is an effect of this.