Last Updated: 23 November 2022

The Ultimate Guide To Sucrase-Isomaltase Deficiency & IBS

Researched & Written By:
Sucrase-isomaltase deficiency (SID) and IBS can overlap in terms of symptoms, which means many people struggle to get an accurate diagnosis. People with SID and IBS-D or M share symptoms including bloating, gas, abdominal pain, and severe osmotic diarrhea following a meal. So in this guide we're going to really dig into how they compare, and what you can do with your doctor to work out where you sit. This is the ultimate guide to SID and IBS!
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Table of Contents

Sucrase-Isomaltase Deficiency

What is sucrase-isomaltase?

Sucrase-isomaltase is an enzyme made in the small intestine that helps digest certain carbohydrates, such as sucrose and starches.

Sucrose table sugar
Sucrose is commonly known as table sugar and is broken down by the enzyme sucrase

What are sucrose and starches?

Sucrose and starches make up more than 60% of the carbs eaten in Western diets.2

  • Sucrose, sometimes referred to as ‘table sugar,’ is a disaccharide composed of fructose and glucose (two monosaccharides) and requires the enzyme sucrase for digestion.
  • Dietary starch is a broad group of carbohydrates known as polysaccharides. Starches require several digestive enzymes during the digestive process in order to be properly digested. This begins in the mouth by an enzyme called amylase. 3Amylase breaks down starches into smaller chains of sugar molecules, such as the as maltose or alpha dextrins. From here, these sugar molecules get further broken down by enzymes like isomaltase.2
Sucrase isomaltase deficiency
In Sucrase-Isomaltase Deficiency sucrose and starches are not able to fully digest due to the dysfunction in enzyme production. Reproduced from 2021 study

What is sucrase-isomaltase deficiency (SID)?

In Sucrase-Isomaltase Deficiency (SID) sucrose and starches are not able to fully digest due to the dysfunction in enzyme production. This results in a number of symptoms like abdominal pain, cramping, bloating, gas, and osmotic diarrhea after ingesting a meal.45

What causes SID?

SID is usually discussed as either being congenital/genetic or acquired.

  1. The genetic version is because of genetic variations in what are called ‘sucrase-isomaltase (SI) genes.’ 2There are at least 37 mutations in the SI gene found so far. The mutations affect gene functioning in different ways which results in a broad range of enzyme activity levels. For example, sucrase activity in patients with SID can be anywhere from absent to low, while isomaltase activity can range from absent to normal. Maltase activity can also be affected.51
  2. The acquired version of SID develops after some kind of intestinal damage, like infections (ex: Giardiasis), SIBO, Crohn’s disease, ulcerative colitis, etc. This version of SID can resolve once the secondary cause (like SIBO or Crohns) is cured or under control, whereas SID from a genetic variation is lifelong. Unfortunately, the acquired form of SID has not been extensively researched.52

What are the symptoms of SID?

Since enzyme activity can vary from person to person, symptoms and their severity can also vary.

Other factors that can affect symptoms are bacteria fermentation in the colon, coexisting abnormal gut motility, and visceral hypersensitivity, to name a few.2

How do you diagnose sucrase-isomaltase deficiency?

Diagnosing SID can be done by a few different testing methods. Some of these methods include breath tests, genetic testing, or a biopsy (which is the gold standard for diagnosing).2

If you want to learn more, check out our guide to IBS tests.

Quick Summary

IBS & Sucrase-Isomaltase Deficiency

Symptom overlap & diagnostic confusion

The overlap between SID and IBS can lead to diagnostic confusion due to the similarities in symptoms and disease presentation. People with SID and IBS-D or M share symptoms including bloating, gas, abdominal pain, and severe osmotic diarrhea following a meal.2

IBS patients have higher rate of SI gene variants

Adding to the confusion, IBS patients have been shown to have a higher rate of some SI gene variants than those without IBS. A recent study found that SID was present in 35% of IBS patients, most of which had IBS-D. Another study looked at patients with diarrhea (although only some had IBS-D), and it showed that 17% of those patients had a positive sucrose breath test, suggesting that they may have SID.25

Low FODMAP diet vs sucrose & starches

Sucrose and some starches are generally allowed on a Low FODMAP diet (a diet used to treat IBS).

Patients with IBS-D and SI gene variants have demonstrated less symptom relief from a low FODMAP diet than patients with IBS-D who do not have SI gene variants.

So for someone who has IBS and doesn’t respond to a low FODMAP diet, they may want to consider trialing SID diet interventions.2

Researchers still don’t know if patients with SID are misdiagnosed with IBS or if sucrose/starch are triggers for GI symptoms in patients with IBS. It’s possible that sucrose and starch may have similar clinical consequences as FODMAPs in IBS patients. 2As always, much more research is needed.

Sucrase isomaltase deficiency diet
Saying goodbye to table sugar and some starches via SID diet intervention, can be worth trying if a low FODMAP diet hasn't helped

Quick Summary

How To Treat Sucrase-Isomaltase Deficiency

Diet management for sucrase-isomaltase deficiency involves dietary changes, enzyme supplementation, or both, depending on the severity of the deficiency.25

Restrict foods with sucrose

Managing SID generally involves restricting foods that contain sucrose and, sometimes, starches. Since all forms of SID have impaired sucrase activity it is recommended to eliminate sucrose-containing foods first.

Sucrose naturally occurs in some foods, but is most well known for being ‘table sugar.’ So when avoiding sucrose, it’d be best to avoid anything with ‘added sugar,’ but commonly eaten fruits and vegetables may also need to be avoided.5

Restricting fruits on SID diet
Apart from 'added sugar', you may also need to avoid fruit on a diet for sucrase-isomaltase deficiency

Decrease foods with starches

If symptom relief is not adequate with sucrose avoidance alone, you may benefit from decreasing your intake of starches. Starches are found in many foods like rice, potatoes, bread, etc.5

List of foods high in sucrose and starch

Unfortunately, food databases can sometimes lack adequate nutritional information on nutrients that aren’t mandated for food labels (ex: starches), but Sucraid™, a company that sells a digestive enzyme for SID management, has compiled food lists to help guide patients with SID.

For sucrose and starch content of food and how to read food label packages for SID diet restrictions, click these links:

Try digestive enzymes supplements

Another option for symptom management in SID is enzyme supplementation. Some patients supplement their meals with sacrosidase, a manufactured enzyme made from yeast that can aid in the digestion of sucrose.

Several studies have shown that taking sacrosidase (Sucraid™) following a meal with sucrose has been shown to reduce GI symptoms and improve breath testing results in patients with the genetic form of SID.

Keep in mind that supplementing with sacrosidase is not as effective when eating starch, as sacrosidase aims to assist in digesting sucrose. 2Additionally, supplementing sacrosidase has not been tested in patients with the acquired form of SID.

Chew more thoroughly

Since sucraid doesn’t help with starch digestion, a tip that may help with tolerating starches better is to chew thoroughly when eating starchy foods. This increases the amount of digestion happening in the mouth by amylase.5

The takeaway from this research

Some patients with SID may find relief with either dietary interventions or enzyme supplementation alone, the most relief may be seen when combining the two interventions.2

The process of dietary restriction is complex and can involve several weeks of eliminating sources of sucrose and starches, followed by a gradual reintroduction of these foods into your diet. Because of this complexity, we recommend that any dietary restriction is under the guidance of a registered dietitian to ensure proper nutrition intake and successful symptom relief.

Quick Summary

Summary & Verdict

IBS ebook

Which Foods Really Trigger Your IBS?

Discover exactly which foods you should and shouldn’t eat using our IBS Food Journal.

  1. Robayo-Torres CC, Opekun AR, Quezada-Calvillo R, Villa X, Smith EO, Navarrete M, Baker SS, Nichols BL. 13C-breath tests for sucrose digestion in congenital sucrase isomaltase-deficient and sacrosidase-supplemented patients. J Pediatr Gastroenterol Nutr. 2009 Apr;48(4):412-8. doi: 10.1097/mpg.0b013e318180cd09. PMID: 19330928; PMCID: PMC3955999.

  2. Lenhart, A., Chey, W.D. & Eswaran, S. Sucrase-Isomaltase Deficiency: Hiding in Plain Sight?. Curr Treat Options Gastro 19, 500–508 (2021)

  3. Barbara E. Goodman, Insights into digestion and absorption of major nutrients in humans. 2010 Advances in Physiology Education, 44-53 34 10.1152/advan.00094.2009 20522896

  4. Kim, S.B., Calmet, F.H., Garrido, J. et al. Sucrase-Isomaltase Deficiency as a Potential Masquerader in Irritable Bowel Syndrome. Dig Dis Sci 65, 534–540 (2020)

  5. William D. Chey, MD, AGAF, FACG. FACP, Brooks Cash, MD. Anthony Lembo, MD. Daksesh B. Patel, DO. Kate Scarlata, RDN, LDN. Congenital Sucrase-Isomaltase Deficiency: What, When, and How? Gastroenterology & Hepatology, October 2020 – Volume 16, Issue 10, Supplement 5

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