Starch Intolerance - What Is It and How Do You Know If You Have It

Starch Intolerance: What Is It and How Do You Know If You Have It?

Do you suspect that starchy foods (even the gluten free ones) seem to be making you sick? 

Does it seem like even the “healthy” stuff like oatmeal, quinoa, and sweet potatoes will send you running to the bathroom and/or leave you doubled over in abdominal pain?

Have you tried a low FODMAP diet and noticed your diarrhea, bloating, cramping and/or other “gut issues” stayed the same – or even worsened?  

If you answered “yes” to any or maybe even ALL of the above questions, you could be dealing with a starch intolerance.

Let me explain…

Disclaimer:  This article was written for general educational purposes, to complement and enhance – NOT replace – medical and nutritional advice from your doctor and a gut health dietitian nutritionist!  Make sure to consult your treatment team 1-1 for customized advice tailored to your bio-individualized needs.

Affiliate disclosure:  This article contains affiliate links*.  As an Amazon Associate, I may earn a commission on qualifying purchases at no extra cost to you!

What is starch?

Starch is a type of polysaccharide found in complex carbohydrate-rich foods such as bread, potatoes, corn, rice, oatmeal, and quinoa (to name a few).

  • Polysaccharides are a type of carbohydrate molecule different from sugars, in that they’re made up of not just a few but MANY monosaccharides (single unit sugar carbohydrate molecules) joined together to form long chains.

On a molecular level, starch is made up of long chains of glucose (a monosaccharide) which is strung together to make bigger, more complex chains called amylose and amylopectin.

Types of starch

There are two types of starch molecules in food:  

  1. Amylose (resistant starch, a water-insoluble constituent found in certain prebiotic foods which feed probiotic microbes)
  2. Amylopectin (digestible starch, which makes up ~70-80% of the starch in food)

Starch in the body

Because starches are larger molecules which break down into simple sugars, it takes longer for starch molecules to digest and break down in our gut compared to their “simple” carbohydrate counterparts monosaccharides and disaccharides (the two molecular categories of sugars).

Our digestion and breakdown of starch into glucose actually begins in the mouth, where our saliva secretes an enzyme called amylase.  

Amylase in our saliva (alongside other digestive secretions in our stomach) help to break down the long starchy chains of glucose  into shorter and shorter pieces, until we’re essentially left with a disaccharide (2-unit carbohydrate molecule) called maltose.

In the intestines, maltose is supposed to get broken down via digestive enzymes into glucose, so it can pass through the gut wall to get absorbed into our bloodstream and used by our cells to make energy.

What is maltose?

Maltose is a type of disaccharide made up of 2 glucose molecules, conjoined together.

Our intestinal brush border is the part of our intestinal lining responsible for making/releasing certain digestive enzymes into our gut, to help digest certain nutrients (including maltose) into smaller units so they can get absorbed into our body.

Starch intolerance, explained

If you have a starch intolerance, it means your body isn’t properly breaking starch down into maltose (which would indicate not making amylase enzymes in your saliva), or more likely, your gut isn’t breaking down the maltose (the intermediary “stepping stone” product of starch breakdown) into glucose.  

Houston, we have a problem!

Undigested maltose disaccharide molecules are too large to get absorbed into the body, but not able to get any further broken down into glucose in cases of a sucrase-isomaltase enzyme deficiency.

So they end up with a fate very similar and parallel to undigested lactose, in cases of lactose intolerance.

More specifically, these undigested maltose molecules create an osmosis-like effect, pulling lots of water into your colon (to help dilute these big molecules)… resulting  in a digestive “aftermath” of unwanted symptoms.

Starch intolerance symptoms

If your body isn’t properly digesting and breaking down the maltose from starch, you’ll most likely experience any or all of the following (usually within ~30 to 90 minutes after eating food with starch):

  • Abdominal pain
  • Cramping
  • Nausea
  • Diarrhea
  • Gas
  • Bloating
  • Sometimes vomiting

As I mentioned earlier, the mechanism behind this reaction is pretty parallel to a lactose intolerance, except that we’re dealing with a different type of disaccharide enzyme deficiency.

(For the record, in some cases it is possible to have a starch intolerance AND a lactose intolerance, simultaneously. I wish I was kidding.)

What causes a starch intolerance?

Most often, a starch intolerance is caused by an underlying sucrase-isomaltase enzyme deficiency.

…A what?! (Let me explain!)

Sucrase and isomaltase are specific digestive enzymes which are supposed to be made and released via the brush border of your intestines, to digest sucrose and maltose, respectively, into monosaccharides (the smallest molecular unit of carbs) so they can enter your body and get used as fuel.

There are two different types of sucrase-isomaltase deficiency:

  1. Genetic (congenital) – aka “CSID” – caused by a genetic mutation – so usually lifelong, starting in infancy
  2. Secondary (acquired) – which usually develops later in life, following a case of celiac disease, colitis, and/or small intestinal bacterial overgrowth (SIBO) left unchecked for too long (these conditions would wreak havoc on your intestinal brush border, which is a key player in your digestive system involved in digestive enzyme secretion)

How to tell if you have it

If you suspect you could have a starch (and sucrose) intolerance caused by a sucrase-isomaltase enzyme deficiency,  there are a few different ways to know for sure. 

Just be prepared to put your detective hat on, with help from a qualified CSID-informed treatment team.

Option 1 – Intestinal biopsy

Consult a CSID-informed gastroenterologist about getting an intestinal biopsy to measure and assess your disaccharide enzyme production.

This test is considered the gold standard, since it’s the most accurate – but it’s also the most invasive and expensive.  So keep reading, to consider your options!

Option 2 – 13C-breath test

Run a 13C-breath test for measuring and assessing your sucrose digestion.  

(This doesn’t necessarily measure starch intolerance, but as I mentioned earlier, sucrose intolerance and starch intolerance usually go hand-in-hand.) 

Option 3 – Low sucrose & low maltose elimination and reintroduction diet

This option is the most cost-effective and the least invasive = but it can also be the most difficult to execute, and can feel the most challenging depending on your level of education on the “CSID diet”.

An elimination and reintroduction diet means you’ll temporarily eliminate all foods high in sucrose and maltose for a period of time, to see if this helps reduce/eliminate your unwanted IBS-like symptoms.

Once you’re symptom-free, start reintroducing foods high in maltose and sucrose one-by-one to see what triggers symptoms.

(Disclaimer:  Restrictive diets like this can go downhill really fast, if not executed responsibly. I really don’t recommend trying this without clinical guidance and supervision from a CSID-informed gut health dietitian.)

  • Want to work together? Apply here for my 1-1 client waitlist. (But only if you live in the United States and feel like we’d potentially make a great team!)

In addition to working with a registered dietitian, I also recommend checking out the following resources to get educated:

Mastering CSID Online Course (Affiliate Link) - Learn More Here

Starch intolerance treatment plan

Low sucrose and low maltose diet (“CSID diet”)

If it turns out you DO have a starch intolerance (and subsequent sucrase-isomaltase deficiency), it’s foundational that you begin a low-sucrose, low-maltose diet for symptom management.

The challenge here is that your body still need carbs, so you’ll want to make sure you’re still getting enough you-friendly carbohydrates for energy (and of course all the other important nutrients you need) from your food.

I mentioned this already, but i highly recommend the following resources for extra help eating balanced and preventing nutritional deficiencies on a CSID diet:

Enzyme replacement therapy (as needed)

Some (but not all) folks with a starch intolerance find that taking 1 to 3 Starchway enzyme capsules at the beginning of a meal containing starch helps them to break down starchy foods more effectively.

(However, in my private nutrition practice, not all of my clients with sucrase-isomaltase deficiency find Starchway to be helpful.)

You may also want to consult your doctor about trying Sucraid® as needed, to help break down the sucrose in certain types of high-sucrose fruit.

Ancillary gut repair interventions (if applicable)

Remember that healing your gut entails more than just cutting reactive foods out of your diet, or even taking enzymes to help digest your food better.

Especially if you have acquired sucrase-isomaltase deficiency, it’s imperative that you work with your treatment team to figure out what caused this to happen – and then address it accordingly.

Clinical interventions may include a colonoscopy, a celiac test, and/or a SIBO breath test.

From there, you may benefit from functional nutrition supplements that can help you to rebalance your gut microbiome, repair your gut lining, and more.

Recommended reading: The Best Supplements for Leaky Gut (Functional Dietitian Picks)

Starch Intolerance - What Is It and How Do You Know If You Have It?

Frequently asked questions (FAQ’s)

What are the main symptoms of starch intolerance?

While this varies from one person to another, you’ll generally experience abdominal cramping, gas, bloating, diarrhea, and sometimes nausea/vomiting (often within 30 to 90 minutes after eating a food that contains starch) if you have a starch intolerance.

Is it possible to have a resistant starch intolerance?

Yes! If you can’t tolerate regular starch from food, it’s also possible that resistant starch is not the best type of prebiotic food choice for you.

But the good news is you’ve got lots of alternative options to choose from!

(Feel free to read more about other types of prebiotic foods and herbs, here.)

What is a maltose intolerance?

A maltose intolerance is the inability to break down maltose in your intestines, due to a sucrase-isomaltase enzyme deficiency.

(You can feel free to use the term “maltose intolerance”  interchangeably with “starch intolerance”.)

Can I have a corn starch intolerance?

Yes, it’s possible to have a corn starch intolerance.  

Keep a food-symptom journal to pinpoint patterns in your food intake and symptoms.

This can help you determine  whether you have a starch intolerance (caused by a sucrase-isomaltase enzyme deficiency) versus a corn allergy/sensitivity.

Is there such a thing as potato starch intolerance?

Yes, it’s possible to have a potato starch intolerance… but more likely, it’s a starch intolerance.

Keep a food-symptom journal (such a this IBS Food Diary*) to look for patterns and see if you notice other starch foods are giving you a similar reaction.

Final thoughts

A starch intolerance is the inability to digest and absorb starch from food.  Gluten free and/or low FODMAP elimination diets won’t help the starch intolerant.

Symptoms of a starch intolerance are very parallel to symptoms of a lactose intolerance. You’ll notice diarrhea, abdominal pain/cramping, bloating, gas, and/or even nausea/vomiting, following consumption of starchy foods such as potatoes, corn, rice, pasta, oatmeal, and bread.

Keep in mind, starch intolerances usually go hand-in-hand with a sucrose intolerance.

Usually, you’ll find the culprit is a sucrase-isomaltase enzyme deficiency. (You may have the genetic type, or you could have acquired it, secondary to another digestive condition.)

Either way, you can find relief on a low-starch/”low-maltose” diet. 

You may also want to consider enzyme replacement therapy (such as starchway), if applicable.

But keep in mind, one size never its all. 

If you suspect you might have a starch intolerance, consult a CSID-informed doctor and a registered dietitian. These clinicians will help you investigate this clinically with the right guidance, support, and testing.

Lastly, make sure to check out the related articles and resources below…

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Recommended resources & next steps

If this is resonating, make sure to check out these helpful resources!  They can help you to crack your code and massively uplevel your quality of life:

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