Acquired Sucrose Intolerance: How to Navigate Sucrase-Isomaltase Deficiency in Adults

Acquired Sucrose Intolerance: How to Navigate Sucrase-Isomaltase Deficiency in Adults

According to a 2022 study, about ~34-40% of folks with diarrhea-predominant irritable bowel syndrome (IBS-D) may actually have an underlying sucrose intolerance – aka a type of sugar malabsorption very similar to lactose intolerance, which masquerades as IBS. (1

(A sucrose intolerance occurs when your body isn’t making and releasing enough of a digestive enzyme called sucrase-isomaltase… so you’ll often notice diarrhea after eating sugar.)

There are two subtypes of sucrase-isomaltase deficiency: primary (genetic) and secondary (acquired).

But since only ~0.2% of North Americans have a genetic or “congenital” sucrase-isomaltase deficiency (CSID), this means the majority of folks with sucrose intolerance are navigating a secondary or “acquired” sucrase-isomaltase deficiency – which usually shows up later in life, versus in infancy.

In this article we’ll dive deeper into what it means to have an adult-onset acquired sucrase-isomaltase deficiency(versus CSID), and what you can do about it.

Disclaimer:  This article was written for general educational purposes, not to replace medical or nutritional advice. Make sure to consult with your doctor and a gut health dietitian nutritionist to receive custom guidance and recommendations tailored to your individual needs!

Affiliate disclosure:  This article contains several affiliate links*.  As an Amazon Associate, I may earn a small commission on qualifying purchases.

What does it mean to have an acquired sucrose intolerance? 

If you have a secondary or  “acquired sucrose intolerance”, it means your sucrase-isomaltase enzyme production has been mechanically shut off, secondary to another underlying medical condition damaging the brush border of your intestines. 

(For example:  Celiac disease and small intestinal bacterial overgrowth are two of the most common culprits of acquired sucrase-isomaltase deficiency!)

How it works:  Harmful bacteria and/or inflammation in the intestines left unchecked will damage the brush border, interfering with your body’s ability to produce the digestive enzymes sucrase and isomaltase which are responsible for the breakdown of sugar and starch.

How do I know if I have it?

If you’ve tested positive for a sucrose intolerance and it developed later in life (versus in infancy or early childhood), chances are your sucrose intolerance was acquired versus genetic.

Sucrose intolerance testing

The best way to know for sure whether or not you have a sucrose intolerance is via a sucrase enzyme activity assay from a duodenal biopsy, which must be done during an endoscopy or colonoscopy.

You can also assess for sucrose malabsorption through running a 13C-sucrose breath test, which is less invasive and which can be done at home.

I have acquired sucrose intolerance – now what? (How to address it)

Okay, so you’ve figured out by now that you have a sucrose intolerance and it was acquired secondary to another GI condition…

So, where to go from here?

Below is a general overview and step-by-step summary of what you’ll need to do in order to address your acquired sucrose intolerance holistically, from all angles.

  1. Work with a GI doctor and a functional dietitian nutritionist so you can uncover your underlying root-cause culprits (celiac, SIBO, Crohn’s, etc.).
  2. Begin a sucrose intolerance (low sucrose) elimination diet (with guidance and supervision from your dietitian).
  3. Keep a detailed food-symptom journal.
  4. Uncover other co-occurring food intolerances and food sensitivities.
  5. Lean on digestive enzyme replacement therapy as needed.
  6. Move through the 5R’s of gut repair (with help from a functional medicine dietitian).

1:  Uncover your root cause(s)

If you developed a sucrase-isomaltase deficiency as an adult, this didn’t happen for no reason.  

In order to address your sucrose intolerance holistically, it’s imperative that you pinpoint the underlying culprit(s) or “root causes”.

(As a holistic dietitian nutritionist, I believe everything happens for a reason when it comes to our health!  All conditions have a root cause – if not multiple root causes.)

The most common underlying root-cause conditions linked with acquired sucrase-isomaltase deficiency are small intestinal bacterial overgrowth and/or inflammatory bowel disease such as celiac disease and/or Crohn’s disease.

(Unfortunately, most healthcare practitioners in the United States and many other parts of the world still aren’t routinely testing for SIBO or IBD, so this stuff is flying under the radar for longer than it should.)

You’ll need to consult a gastrointestinal doctor to assist with diagnostic testing, and you will also benefit from working with a gut health dietitian nutritionist to help you identify any underlying patterns. 

2:  Begin a sucrose intolerance elimination diet

If your body can’t break down sucrose on its own, you’ll feel a LOT better on a sucrose intolerance diet

(This means avoiding or limiting foods high in sucrose, while leaning more on sucrose-free / low-sucrose foods.)

Below are a few helpful resources which can make your meals more enjoyable…

CSID Made Simple Cookbook with Amazon affiliate link


Sucrose Intolerance and CSID Diet Plan PDF with Meal Planning Guide and 21 CSID Recipes


3:  Keep a food-symptom journal

Since one size doesn’t fit all, due to bio-individuality, you may also benefit from keeping a detailed food-symptom journal to get a better idea of which foods your body uniquely can and can’t tolerate.

This is especially important for folks with an acquired sucrose intolerance, since you’ll likely find that you have other additional food intolerances and food sensitivities aside from just sucrose.

Digital food-symptom logging apps

If you prefer a digital food-symptom journal, you may find the MySymptoms app helpful.  

Many of my clients also enjoy using the food-symptom journal in our Healthie client portal which may be an option for you too, if you’re working 1-1 with a registered dietitian.

Paperback elimination diet workbook

On the other hand, if you’re old-school (like me) and you prefer a paperback food-symptom journal, I recommend ordering a copy of this CSID Elimination Diet Workbook* which was created by amazing CSID dietitian colleague!

CSID Elimination Diet Workbook - with Amazon affiliate link

4:  Pinpoint co-occurring food intolerances and sensitivities 

The purpose of the food-symptom journaling is to help you see patterns and correlations more clearly, so you’ll have a better idea of which foods work best for YOUR body.  

Food intolerances

When you have a food intolerance, your digestive system is unable to break down a specific constituent found in certain foods – usually because of missing digestive enzymes.

So you’ll feel bloated, crampy, nauseous and possible even have diarrhea shortly after eating/drinking something that you can’t digest.

(It’s usually pretty easy to pinpoint food intolerances, since the reactions will occur within ~30-90 minutes of eating.)

For example, folks with co-occuring methane SIBO usually feel better on a custom version of a low FODMAP diet (in addition to reducing their sucrose intake).

I also often see people with sucrose intolerance notice that they also have a fructose intolerance and/or lactose intolerance if they have methane or hydrogen SIBO, while those with hydrogen sulfide SIBO can’t tolerate high sulfur foods.

Food allergies

Or if you have celiac disease, you may find that going 100% gluten free gives you relief (since in this case, you would have a gluten allergy). 

  • Please don’t cut gluten out of your diet until after you have tested for celiac disease, or you’ll get a false negative test result!

These are all just general examples of how different types of food intolerances can potentially leave clues about what’s going on in your body at a deeper level.

However, unfortunately the gut is VERY complex, so food intolerances don’t always give us the full picture when it comes to adverse food reactions. 

Enter: food sensitivities.

Food sensitivities

In my experience, people with inflammatory bowel disease (especially Crohn’ and colitis) also tend to have a slew of underlying food sensitivities, which are different from food intolerances in that they involve the immune system. 

Food sensitivity reactions aren’t as clear or cookie-cutter, since they can be delayed, dose-dependent, and more broad-spectrum.  

(Read more about the key differences between food allergies vs. food intolerances vs. food sensitivities here!)

If you’re navigating a type of inflammatory bowel disease and need help identifying food sensitivities, it may be in your best interest to consult a certified LEAP therapist about running a Mediator Release food sensitivity test to identify other more hidden food sources of diet-induced inflammation and diarrhea, if you’re still not feeling close to 100% better after addressing food intolerances.

Long story short:  Make sure you’re working with qualified practitioners who can help you, and leave no stone unturned until you feel realigned!

4:  Leverage enzyme replacement therapy 

Below are examples of the most common types of digestive enzymes my clients have benefited from when navigating an acquired sucrose intolerance.

Keep in mind: the types and amount of enzymes you may need will be unique to you!

Make sure to consult your doctor and dietitian about whether any of the following enzymes may be beneficial for you on your gut-healing journey. 


Whether you have CSID or acquired sucrase-isomaltase deficiency, you may benefit from a special digestive enzyme called Sucraid, which you can take before meals to aid in the digestion and breakdown of sucrose in your intestines.

(Feel free to check out my advice and perspectives on Sucraid here!)


Depending on the degree of damage to your intestines, you may also potentially benefit from taking general brush border digestive enzymes, or a special enzyme called Starchway which aids in the breakdown of starch.


If you also have a lactose intolerance, consider trying lactase enzyme supplements before consuming dairy that contains lactose.

FODMAP enzymes

Lastly, if you find it difficult to eat foods high in FODMAPs (short-chain carbohydrates which are “fermentable oligosaccharides, disaccharides, monosaccharides and/or polyols”), you may even want to give a FODMAP enzyme such as FODZYME* a try.

I know this sounds like a lot… and it is.

But believe it or not, we’re still only at the level of symptom management when we talk about removing the foods that trigger symptoms and supplementing with digestive enzymes.

That’s right… there is a lot more to the gut-healing and gut repair journey, for those who want a root-cause approach.  (Your gut is COMPLEX!)

Keep reading at your own discretion, only if you want the rest of the story when it comes to gut repair.

6:  Work your way through the 5R’s of gut repair

This last step is the component of gut repair that most people are completely missing the boat on… which is why most people with gut issues spend the majority of their lives in a perpetual state of trying to avoid whatever foods are making them sick.

(Disclaimer: if you have CSID, the genetic version of a sucrose intolerance, you DO unfortunately need to spend your entire life avoiding foods that contain sucrose and stay within your window of tolerance, since we cannot change your genetics.)

But if you have an acquired sucrose intolerance, please know that it is possible (in some cases) to heal and repair the damage to your intestines,

The key is to tackle the underlying root causes from all angles, via a holistic, multi-dimensional approach.

This is where the 5R protocol for gut repair comes into play!  

The 5R’s (remove, replace, reinoculate, repair, and rebalance) is a unique holistic approach which encourages us to rebalance the gut microbiome and lean on special fuctinal foods and supplements which help promote healing in your intestinal lining.

When the 5R approach is properly executed consistently over the course of months/years, your gut may potentially be able to start producing the right enzymes (and breaking down food properly) again at some point down the road without too much assistance.

(By no means is it a quick fix, but the most important thing to keep in mind is that this is possible for you!)

Read more about the 5R protocol for gut repair here.

Recap and final thoughts 

Having an acquired sucrose intolerance is different from CSID in that rather than being caused by a genetic mutation, this subtype of sucrose intolerance is caused by an underlying medical condition such as SIBO, Crohn’s or celiac disease which has been wreaking havoc in the brush border of your intestines.

While an acquired sucrose intolerance is no picnic, when you’re addressing it from all angles and using a holistic, root-cause approach, it is possible to restore more “normal” function in your intestines in some cases.

The key steps to take in addressing this common IBS “imposter” is to work with qualified healthcare professionals who can help you to:

  1. Figure out the root cause of your sucrase-isomaltase deficiency
  2. Lean into a customized sucrose intolerance diet
  3. Keep a detailed food-symptom journal 
  4. Get clear on any co-occurring food intolerances and food sensitivities that could be inflaming your intestines
  5. Lean on enzymes as needed
  6. Work with a functional medicine dietitian to help you implement and execute a 5R protocol for gut repair (if you’d like to move past symptom management)

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