What is Fructose Malabsorption? What is Fructose Intolerance?

What is Fructose Malabsorption?

What are they and how are they different?

For those of you who have never heard of this condition, it isn’t as weird as it sounds.

Formerly called Dietary Fructose Intolerance—DFI for short—Fructose Malabsorption is the small intestine’s inability to absorb fructose because of deficient enzymes.

In other words, it is similar to lactose intolerance but pertains to fructose sugar rather than lactose sugar.

In fact, more than half of people previously diagnosed with irritable bowel syndrome actually have some level of fructose malabsorption.

So if you currently suffer from IBS, odds are good that your current condition isn’t some unsolvable mystery, and fructose malabsorption may be the culprit.

However, it is important to note that a related and much more serious condition exists called Hereditary Fructose Intolerance (HFI), which I discuss later on below.

How do I know if I have Fructose Malabsorption?

Clinically, one is considered to have fructose malabsorption if they are unable to absorb more than 25 grams of fructose in one sitting.

It may not sound like much, but 25 grams of fructose at once is a lot—especially since fructose absorption is improved in the presence of glucose, giving a bit of leeway to that threshold.

What are the causes? How common is it?

Fructose Malabsorption is actually quite common and affects around one in three individuals, but, of course, at different spectrums.

On average, healthy individuals are able to absorb somewhere between 25 to 50 grams, whereas someone with fructose malabsorption may only be able to absorb around 3 grams in one sitting.

How is it possible that fructose malabsorption can affect one in three people, yet remain such a ‘fringe’ dietary condition?

It’s unlikely that someone will notice some sort of dramatic fructose sensitivity if they are at the higher range of fructose absorption, even though they are still technically considered to have fructose malabsorption. So while it’s common, most are unaware that they have it.

With respect to what causes fructose malabsorption, it still remains unclear as to what the true mechanism of induction is. Under these circumstances, a multitude of theories and thoughts have been put forth.

Overall, it is generally thought that something causes a physical change in the intestines enzyme capabilities, thus causing fructose malabsorption.

  • Excessive fructose consumption during infancy and childhood years

  • Imbalances of the gut biome—excess bad bacteria

  • High intake of refined and processed foods

  • Use of antibiotics

  • Preexisting gut issues such as irritable bowel syndrome (IBS), or gut disorders that cause intestinal damage such as Gastroenteritis, Crohn’s disease, and Celiac disease

  • Decrease in body’s fructose absorption abilities from excessive use/aging

  • Gut & related internal organ inflammation

  • Stress—acute and chronic

I do want to make a point with regards to the relationship between preexisting gut problems and the presence/diagnosis of fructose malabsorption:

If you have certain gut disorders such as IBS, Crohn’s disease, colitis, or celiac disease, you’re more likely to have dietary fructose malabsorption or intolerance.

However, whether one causes the other is unclear. In a study that involved 209 patients with IBS, about one-third had fructose intolerance. Those who were compliant with restricting fructose saw improvement in symptoms. If you’re living with Crohn’s, this nutrition guide may also help.

In addition, if you’re on a gluten-free diet but still having symptoms, you may be having trouble with fructose. It’s never a bad idea to get checked for fructose malabsorption if you have a major gut issue. (Heathline)

After all of that, I’m sure you’re now wondering…

What actually happens in the body when too much fructose is consumed?

…[f]ructose that has not been adequately absorbed is fermented by intestinal bacteria producing hydrogen, carbon dioxide, methane and short-chain fatty acids. This abnormal increase in hydrogen may be detectable with the hydrogen breath test. (Wikipedia)

…and what happens after that?

That’s our cue to move on to our next discussion…

What are the symptoms of excess fructose consumption?

  • Nausea

  • Bloating

  • Gas

  • Abdominal pain and cramping

  • Diarrhea

  • Vomiting

  • Headaches

  • Insomnia

  • Onset of depression

These symptoms can manifest anywhere from twenty minutes post-meal or even a few hours.

They’re no fun at all.

Moreover, frequent excessive fructose consumption for the FMer can have long-term—but amendable—consequences that can affect one’s health later, so correcting one’s diet as soon as possible is recommended.

Is there a way to test for Fructose Malabsorption?

Is there a way to know for certain that you have fructose malabsorption? Or could it be another sensitivity?

Aside from simply eating foods that contain fructose and waiting to see what happens, you can get the aforementioned hydrogen breath test procedure done to measure your body’s response to fructose.

The best test for diagnosing fructose intolerance is the breath test. In this test, you drink a solution that has fructose dissolved into it. The amount of methane and hydrogen you breathe out then helps to show if you’re digesting the fructose properly or not. (WebMD)

I got this test done myself in the 5th grade at my city’s children’s hospital, and unfortunately got ‘high scores.’

It’s worth noting that at the time my father also wanted to get the test done, however, we couldn’t find any hospital or clinic in the area that offered the test to adults.


I’m not sure.

This was back in 2006, so it may have simply been related to available medical services in our geographic location, or perhaps not offering the test to adults is just some kind of standard practice.

What makes this strange, however, is that from what I have read, most individuals seem to actually get diagnosed with fructose malabsorption later on in life, sometime between their 20s and 40s.

So one would think that offering the breath test for adults would be a regular practice, right?

I can’t imagine it’d be difficult to find a clinic offering this test near you with the way the internet is these days, but again, I’m not sure.

If getting a breath test isn’t possible, and you’re juggling a possible fructose malabsorption diagnosis with other possible diagnoses, an elimination diet and subsequent testing period is your best bet.

Elimination Diet

A temporary bland diet centered around meat and rice is safe for most people as you figure out what the heck is going on—I have a simple FODMAP Diet Guide here that may be helpful.

It’s important you begin a strict elimination diet because fructose and its, ‘sugar sisters,’ for lack of a better word, can be found everywhere, which can ultimately make connecting the dots and solving your digestive problems difficult.

For instance, it is very common for cold-cut meat and bacon to be cured with sodium erythorbate, a sugar that commonly causes issues for the FMer.

FMers can then begin to believe that anything from meat, to bread, and fruit bother them, and feel hopeless.

Keep an eye out for those sneaky ingredients and pesky sugar additions.

As you’ll soon find out, if you haven’t already, they’re seemingly everywhere.

Alternative Testing

If you decide to do an ‘at home’ FM test, I’d suggest picking one or a few (if you want to do a couple of tests) of these high fructose content items that easily send me over the edge:

  • Fruit Juice—Orange Juice, Grape Juice, Apple Juice, etc.

  • Agave Syrup

  • Honey

  • Dried Fruits

  • Dates

What are the Consequences of Regular Excess Fructose Consumption?

Even if you feel like your fructose-eating symptoms are relatively benign, it is still in your best interest to eliminate it from your diet—or at least until you’re no longer surpassing your guts ‘fructose absorption threshold.’

Don’t decide to band-aid your symptoms with Pepto, Immodium, and Caffeine.

While those things are fine in a pinch if you’ve accidentally eaten triggering foods, it will come back to haunt you in the long run.

Regular malabsorption can bring with it a multitude of annoying health and lifestyle complications, many of which I can personally attest to:

  • Chronic Fatigue

  • Insomnia—falling asleep and staying asleep

  • Sleeping too long—for 9-11+ hours

  • Desire to use stimulants to stay awake

  • Malabsorption of certain nutrients, such as iron, folic acid, zinc

  • Malabsorption or L-Tryptophan - can result in low serotonin levels causing depression and lethargy.

  • Unbalanced gut biome leading to SIBO, Candida, and other overgrowth conditions

  • Leaky Gut Syndrome

All of these are a topic of their own, so to keep it brief, you’re doing your body no favors by continuing to eat fructose.

While something like regular bloat or flatulence may seem to be easy to manage, all of the aforementioned conditions can have very negative impacts with respect to your day-to-day life.

In short, if you get a Fructose Malabsorption diagnosis, don’t ignore it and live in a state of mild suffering and denial.

Treat your body with the respect it deserves, and you’ll be rewarded with health, vigor, and an appreciation for food that you didn’t even know you had.

Trust me on that.


I’ve said this quite a bit throughout this article, and I’ll say it again, supplements are another topic I will dedicate a more comprehensive solo post to, but for now, I’ll go over them briefly.

I do want to mention that if you’re currently suffering from depression—no matter how mild or intense—alongside your FM diagnosis/gut issues, I would highly encourage you to pick up the nutritional supplementation books, The Mood Cure, and The Depression Cure.

I began regularly taking a zinc supplement when I was young—as directed by my doctor—because I would get white marks on my finger and toenails, which is a sign of a zinc deficiency, and it was a game-changer.

I was actually advised to start taking it early in elementary school before I was even officially diagnosed with fructose malabsorption.

It dramatically improved the quality of my skin, hair, and nails, alongside energy levels, mood, and sleep quality.

I didn’t know ‘feeling normal’ felt so good.

In the same way, even once your diet is corrected, I would still recommend regular supplementation of zinc, in addition to other minerals and amino acids like:

  • folic acid

  • iron (for women only)

  • A precursor to serotonin like L-Tryptophan or 5-HTP

  • Experimenting with a B-Complex to see if deficient—It is often said to ideally get a B-Complex with the B12 in the methylcobalamin form rather than cyanocobalamin because of improved absorption, however, I have never noticed a difference—I do eat red meat daily though, so results will vary.

I personally also found the addition of potassium and magnesium to be very beneficial to my wellbeing.

For the curious, other useful supplements I would suggest if you feel so inclined:

—‘Basic Essentials’

—‘Nice-to-haves’—if one’s budget and/or desire allow it

Melatonin can also be a useful supplement to have on hand either for regular use or in case of accidental fructose consumption which can cause immediate insomnia later that night for some individuals.


If you’re going to purchase any of these online, I would also suggest you check out iHerb.com and SwansonVitamins.com before buying on Amazon, as both of these vendors carry high-quality products yet often have a cheaper price.

I’d advise against purchasing supplements in your local grocery store as they’re usually grossly overpriced. I do purchase my multi, vitamin D, and a couple of other generics from my local grocery store though—their store brand price is very low and is always sold as a two-for-one.

What Should I do if I get Diagnosed?

If you need to mourn, mourn.

It may sound silly to someone who hasn’t had to deal with an eating issue, but it can definitely feel depressing initially.

You’ve potentially lost a former source of comfort, socializing, and fun.

If you need to chat, I would encourage you to join one of my groups, reach out to me on social media, or join one (or multiple) of many other groups found in all corners of the web.

The second thing you need to do is get yourself familiar with the kitchen and find out what foods work for you.

Careful eating and spending time cooking are going to be well worth the effort.

If you’ve avoided intensive, hands-on cooking in the past, I highly recommend you put that mindset away and accept ‘more involved cooking’ as one of your newfound hobbies.

Easy microwave meals are usually packed with no-nos, and the best way to control your food is by preparing it yourself

Again, if you’ve avoided cooking in the past or even loath it, I promise you it’ll become fun and be rewarding.

As I said, think of it as a new hobby if this is a hurdle you face.

Your On-Going Treatment

If you’ve determined that fructose malabsorption is the condition plaguing your insides, you may find this to be both good and bad news.

Bad because, hey, you can’t eat some stuff.

And good because, hey, now you know you need to avoid some stuff.

Obviously, it isn’t as trivial as I just made it out to be, but now you know what was causing all those pesky bloating incidents and emergency bathroom runs.

The treatment protocol is a continual and indefinite low-fructose and/or low FODMAP diet.

Unfortunately, to date, there is no ‘cure’ for fructose malabsorption, but we can keep our fingers crossed.

The recent marketing of Xylose Isomerase supplements gives us hope, something I didn’t even know was around until two years ago or so.

If you haven’t heard of that, it’s basically Lactaid for the FMer.

It works well for me in small quantities.

Two Xylose Isomerase products I recommend are Fructaid and Eat Anything Rx.

NOTE: I do not know how Xylose Isomerase works for people with hereditary fructose intolerance, so please do your research if this is you.

Again, I linked it above, but don’t forget to check out my article here where I discuss getting started with a restricted diet, alongside some other pointers.

What Resources Are Available for Dealing With My Diagnosis?

I will make a post of all resources in full another time, but for now, this is where I would look first.

Consider These First

Xylose Isomerase Supplements

Dextrose Powder—for cooking & adding to high-fructose foods to aid absorption


Living With Dietary Fructose Intolerance: A Guide to Managing your Life With this New Diagnosis

Fructose Malabsorption: The Survival Guide: 2nd Edition

Fructose Malabsorption: The Shopping Guide

Food Intolerances: Fructose Malabsorption, Lactose and Histamine Intolerance: living and eating well after diagnosis & dealing with the elimination diet

For additional titles, search ‘fructose malabsorption’ and ‘FODMAPs’ or other related terms to see what’s out there.

Websites & Forums










I don’t use any myself, but I’ve heard good things about some of the FODMAP related apps.

Search ‘FODMAP’ and see what’s available.

What is Hereditary Fructose Intolerance?

Since there is quite a bit of overlap between HFI (Hereditary Fructose Inolterance) and FM (Fructose Malabsorption), I’ll avoid repeating myself where necessary and focus only on the facts.


Hereditary fructose intolerance is a serious type of fructose [malabsorption]. However, it is treatable and manageable.

It occurs when a person is unable to digest neither fructose nor fructose precursors, such as brown sugar.

Those with hereditary fructose intolerance lack sufficient activity of an enzyme called fructose-1-phosphate aldolase, which helps digest fructose.

The fructose then accumulates in the liver and kidneys, causing serious and potentially fatal complications, such as liver and kidney failure. (MedicalNewsToday)

Simply put, this is a serious condition and not something to be taken lightly.

If you’re diagnosed with HFI, you must adhere to the diet at all times.

Cheating is not something that can be done provided you’re willing to put up with some crappy—pun intended—consequences.

Cheating on your diet can and will do serious harm to your body.

Your strict and daily adherence to your diet is mandatory for your health.

While the symptoms of eating fructose are similar, again, the consequences are very serious.

What are the causes? How common is it?

Mutations in the ALDOB gene cause hereditary fructose intolerance. The ALDOB gene provides instructions for making the aldolase B enzyme. This enzyme is found primarily in the liver and is involved in the breakdown (metabolism) of fructose so this sugar can be used as energy. Aldolase B is responsible for the second step in the metabolism of fructose, which breaks down the molecule fructose-1-phosphate into other molecules called glyceraldehyde and dihydroxyacetone phosphate.

ALDOB gene mutations reduce the function of the enzyme, impairing its ability to metabolize fructose. A lack of functional aldolase B results in an accumulation of fructose-1-phosphate in liver cells. This buildup is toxic, resulting in the death of liver cells over time. Additionally, the breakdown products of fructose-1-phosphase are needed in the body to produce energy and to maintain blood sugar levels. The combination of decreased cellular energy, low blood sugar, and liver cell death leads to the features of hereditary fructose intolerance. (MedlinePlus)

The incidence of hereditary fructose intolerance is estimated to be 1 in 20,000 to 30,000 individuals each year worldwide. (MedlinePlus)

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition. (MedlinePlus)

What are the symptoms of excess fructose consumption?

  • Nausea

  • Bloating

  • Diarrhea

  • Vomiting

  • Abdominal pain

  • Strong dislike of sweets

  • Hyperventilation

How Does One Test for Hereditary Fructose Intolerance?

[Doctors] may perform several tests to diagnose hereditary fructose intolerance. These tests are [usually] done on infants when they start to show symptoms. Some tests that can confirm this condition are:

[Babies] will also have a physical examination. Your doctor might check to see if the spleen or liver are larger than normal or if your baby is jaundiced. (WebMD)

What are the Consequences of Regular Excess Fructose Consumption?

  • Low blood sugar.

  • Leaky Gut

  • Problems with growth and development—i.e. stunted growth and/or delayed growth

  • Jaundice

  • Liver or kidney failure—leading to a risk of death

  • Gout

  • Internal bleeding

  • A decrease of phosphate and glucose in the blood

  • An increase in fructose in the urine and blood

What Treatment Options Are Available?

The only current treatment protocol for HFI is a strict, fructose-free diet.


If you happen to be diagnosed with HFI, I would strongly urge you to connect with others who share your condition, be it on web forums, through Facebook groups, and so on.

They will be your best resource for living with this condition.

Please see the resources section above for everything else.

Pour Conclure

I hope the answers I have written here are sufficient with regards to explaining fructose malabsorption and hereditary fructose intolerance.

I welcome any feedback— please let me know if I missed anything, something wasn’t clear, or if anything can be improved.

Likewise, if you have any questions or comments in general, or just want to chat, please leave a comment below or hit me up at one of my socials.

Until next time, friends.

Your pal,

Alexander Smout

If you’d like to spread the word…

Share Health and Vitalité

Disclaimer: None of this is to be deemed as health, fitness, or medical advice in any way, shape, or form. You are reading opinions only. Please consult your physician for personalized medical advice, diagnosis, or treatment.

Questions & Comments: Please feel free to ask questions and leave comments as it relates to the topic(s), or if you’d just like to say hello—I want to hear from you!

Where to Subscribe if You're Not Reading This at my Primary Website: HealthandVitalite.com

Publications: Medium · Steemit · Hive

Socials: Twitter · BitClout · Gab · Instagram · MeWe

Video: YouTube · BitChute

Groups: Facebook · Telegram · MeWe · Minds

What’s Available If You're Interested in Working With Me

-Group Coaching Through Subscription to My Substack Newsletter

>> Details can be found here.


Living With Dietary Fructose Intolerance: A Guide to Managing your Life With this New Diagnosis by Judy Smith

Fructose Malabsorption: The Survival Guide by Debra & Bob Ledford

What to know about fructose intolerance by Medical News Today

What Is Fructose Intolerance? by Dan Brennan, MD

Hereditary fructose intolerance from MedlinePlus

What Is Fructose Intolerance? from Cleveland Clinic

What is Fructose Malabsorption? Is It The Same As Fructose Intolerance? by Amy Burkhart

What Is Fructose Malabsorption? by Natalie Olsen, R.D., L.D., ACSM EP-C and medically reviewed by Natalie Butler, R.D., L.D.

Fructose Malabsorption from Wikipedia

Fructose malabsorption: how to diagnose and manage it by Susan Hunter

Leave a comment

Please note, comments must be approved before they are published