Fructose Intolerance: Types, Diagnosis, Treatment

November 11, 2022 Stan

Fructose intolerance means your body can’t properly digest fructose, a naturally occurring sugar.
Foods that contain fructose include fruits, some vegetables, wheat, and many natural sweeteners.
Try working with a dietitian to determine trigger foods and how much fructose you can safely eat.

All you wanted was a cup of applesauce with your lunch. Now your stomach hates your guts — and your guts hate the rest of you. Is the fructose in your apples to blame?

Fructose is a kind of natural sugar. You’ll find it most commonly in dried or fresh fruit, such as apples, bananas, watermelon, and pears.

But certain vegetables, such as sweet onions and red bell peppers, also contain fructose. So do many natural sweeteners and high fructose corn syrup.

Most people can eat fructose without any issues, but if you’re part of the suspected 33% of the population with fructose intolerance, a handful of grapes might leave you with bloating, gas, or diarrhea.

Below, you’ll find key details on fructose intolerance, including how to get a diagnosis and tips to manage your symptoms.

Types of fructose intolerance

According to Dr. Max Pitman, gastroenterologist at Salvo Health, there are two main types of fructose intolerance. They have different causes and symptoms that can vary from person to person.

These two types are:

Hereditary fructose intolerance

Hereditary fructose intolerance happens when you have a mutation in the ALDOB gene. This gene gives your body instructions to make the enzyme that helps break down fructose. But when it doesn’t function properly, your body doesn’t get those instructions, so you’re completely unable to digest fructose.

This kind of fructose intolerance is genetic. In other words, you can inherit it from your parents if they carry the recessive gene.

Hereditary fructose intolerance is the most serious of the two. It can cause symptoms like:

If you have hereditary fructose intolerance and keep eating fructose, it could lead to complications like:

While these issues might sound a little scary, Pitman says doctors usually recognize this type of fructose intolerance in babies — often after parents add solid foods. It’s also quite rare and only affects around 1 in every 10,000 people.

Dietary fructose intolerance

With dietary fructose intolerance, the cells lining your small intestine don’t absorb fructose as efficiently as they should. Your gut ferments the unabsorbed fructose, which can lead to GI issues. This type of fructose intolerance is also called “fructose malabsorption.”

“Dietary fructose intolerance is much more common and milder,” Pitman says.

But when you eat foods high in fructose, you could still experience uncomfortable symptoms, including:

Researchers have yet to determine the exact number of people living with this condition, but some evidence suggests dietary fructose intolerance affects as many as one in three people.

Getting a diagnosis

In some cases, doctors may have a harder time diagnosing fructose intolerance since its symptoms often overlap with irritable bowel syndrome (IBS).

So, how do you find the culprit for your stomach woes? Well, that depends on the type of fructose intolerance you’re dealing with.

Diagnosing hereditary fructose intolerance

With hereditary fructose intolerance, doctors can make a diagnosis with a genetic test.

Doctors usually diagnose this condition in early childhood. For instance, they might recognize the key signs if a baby has a bad reaction after eating high-fructose foods. This reaction can range from sluggishness to seizures.

Diagnosing dietary fructose intolerance

Dietary fructose intolerance isn’t as easy to diagnose. But if your doctor suspects you have it, they might recommend a hydrogen breath test.

Digestive issues like fructose intolerance can cause higher hydrogen levels in your gut, which come out in your breath. So, the test works like this:

You’ll give a breath sample.
You’ll drink a solution with a small amount of fructose.
You’ll give another breath sample.

If you have a lot of hydrogen in your second sample, your body most likely didn’t handle the fructose well — which can point your doctor toward a diagnosis.

Another option involves trying an elimination diet, like the low FODMAP diet.

With the low FODMAP diet, you cut out foods high in carbohydrate compounds, like fructose, lactose, or sorbitol, that could contribute to GI symptoms.

You’ll eliminate these potentially triggering foods from your diet for around four to six weeks under a doctor’s or dietitian’s supervision. Then, you’ll reintroduce foods one at a time, in gradually increasing amounts, to discover which foods may trigger your symptoms.

If you feel better when you cut out foods with fructose, you may have some degree of fructose intolerance, Pitman says.

Treatment

“There is not a specific medical treatment for fructose intolerance,” says Dr. Yolanda Scarlett, Medical Director of the GI Motility Laboratory at the University of North Carolina School of Medicine.

Scarlett says the best way to manage dietary fructose intolerance involves limiting or avoiding foods high in fructose, such as:

Most fruits: Fructose naturally occurs in most fruits, like mangoes, apples, grapes, and pears. Dried fruits like dates, raisins, figs, and prunes also have a high fructose content.
Certain vegetables: Fructose also occurs in certain vegetables, like sweet onions, red bell peppers, brussels sprouts, broccoli, cabbage, and eggplant.
Natural sweeteners: Fructose helps give natural sugar substitutes like honey, agave nectar, and molasses their sweetness.
High fructose corn syrup: High fructose corn syrup is a common sweetener in soft drinks and processed snacks. When in doubt, check the label.
Wheat: Wheat and wheat-based products, like bread and pasta, can have small amounts of fructose.

It’s also worth noting that if you have dietary fructose intolerance, you don’t necessarily have to kiss fruit goodbye. Most people with dietary fructose intolerance can handle around 10-15 milligrams (mg) of fructose per day, but your individual sensitivity level might be higher or lower.

That means, depending on your tolerance, you may be able to consume certain fruits with lower fructose levels. Just make sure to try them out in small amounts first to determine how much you can handle.

Low-fructose fruits include:

You might find that while grape juice leaves your stomach in knots, a small glass of orange juice doesn’t bother you as much.

Can a supplement help?

Beyond eliminating problem foods from your diet, you can also try xylose isomerase, an over-the-counter (OTC) digestive enzyme.

This digestive enzyme converts fructose into glucose in your small intestine.

Remember, dietary fructose intolerance happens when cells in your small intestine don’t absorb fructose as they should. So, converting fructose into glucose could potentially help your body handle it better.

One small study found that xylose isomerase helped reduce nausea and abdominal pain in people with dietary fructose intolerance after they drank a watery fructose solution. They also had less hydrogen on their breathalyzer scores, which suggests that fructose didn’t bother their digestive system as much.

However, research remains limited on these enzymes. It’s best to talk to your doctor before adding any enzyme supplements to your routine.

Insider’s takeaway

Fructose intolerance can turn your fruit smoothie into a GI nightmare. But with a diagnosis and changes to your diet and lifestyle, you can manage your symptoms and enjoy life without stomach troubles holding you back.

You might also find that some foods with fructose don’t affect you as much as others. For instance, high-fructose apple slices might give you gas, but low-fructose pineapple may not bother you at all.

The key lies in understanding which fructose-containing foods affect your body, and then adjusting based on your specific needs.

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