Sucrase-Isomaltase Deficiency (SID) and Congenital SID

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By Tanzil Miah

Dr Megan Rossi in a lab looking through a microscope

Congenital sucrase-isomaltase deficiency (CSID) is an inherited metabolic disorder where you are unable to digest certain high sugar foods.

In normal digestion, food particles are broken down into smaller molecules by digestive enzymes, so they can be absorbed by the lining of the gut. In CSID we lack these enzymes (sucrase-isomaltase) due to a genetic abnormality.

Acquired SID is more common, and occurs as a result of to damage to the lining of the gut. This could be caused by factors such as infection, Coeliac Disease, Irritable Bowel Disease or Chemo/Radiotherapy

Many people struggle with the digestion and absorption of carbohydrates (starchy foods), and people are often advised to reduce certain types of carbohydrates in their diet (as with the low FODMAP diet). 

In practice, not everyone responds to the low FODMAP diet. Whilst there may be many reasons for this, research suggests that there may be a number of people who are diagnosed with IBS, when actually their symptoms are due to CSID or SID.   

When gluten-free, low lactose and low FODMAP diets have not proved successful in resolving or reducing symptoms, CSID or SID may be implicated.

Signs and symptoms of SID

Common signs and symptoms associated with sucrase-isomaltase deficiency are:

  • Experiencing gut symptoms since childhood (CSID)
  • Symptoms which worsen after eating 
  • Starchy or sweet foods trigger symptoms 
  • Tummy pain
  • Bloating 
  • Diarrhoea 
  • Nausea
  • Vomiting

How is SID diagnosed?

There are various tests used to diagnose SID:

  • Genetic testing (CSID)
  • Endoscopic biopsy (taking tissue samples from the gut lining)
  • Sucrose breath tests
  • Sucrose challenge

Dietary treatment for IBS

Around 50% of our energy comes from carbohydrates or starchy foods, so reducing intake of dietary sucrose can certainly help with symptoms.  

Picture showing both food and supplement optionsSome examples of higher sucrose foods include: 

  • Potatoes, sweet potatoes
  • Bread 
  • Veggies such as black beans, carrots, chickpeas, peas, parsnips
  • Fruits such as apples, bananas, melons, oranges, pineapple
  • Flavoured dairy products 
  • Processed cheeses 
  • Processed meats / meat products (breadcrumbs, seasonings/ coatings containing starch)

Enzyme supplements

Enzyme replacement therapy can be effective in the treatment of SID. It helps break down sucrose in the diet, thereby alleviating symptoms. Inversatase and Sucrid are popular alternatives.


CSID or acquired SID may be the cause of many undiagnosed gut symptoms, particularly among those who have not responded well to dietary exclusion in the past.

However, diagnosis of metabolic conditions is complex, and often other gut conditions will need to be ruled out. If you suspect you may have CSID or SID, before you start any form of dietary exclusion, or introducing any supplements or enzymes, speak with your healthcare professional or a registered dietitian to ensure you get the right support. 

Our team at The Gut Health Clinic can help you explore whether SID is behind your symptoms, and if so, support you through the dietary management of the condition and minimise the risks associated with a restrictive diet.


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