IBS or CSID? Why Expert Support Matters for Sucrose and Starch Intolerance in Australia

Congenital Sucrase-Isomaltase Deficiency (CSID) (also known as Sucrase-Isomaltase Deficiency (SID), Genetic Sucrase-Isomaltase Deficiency (GSID), or Acquired Sucrase-Isomaltase Deficiency (ASID)) is a digestive enzyme disorder that affects the body’s ability to break down certain sugars and starches.

The condition occurs when the sucrase-isomaltase enzyme in the small intestine does not function properly or is present in low amounts. This enzyme is responsible for breaking down sucrose (table sugar) and parts of starch into smaller sugars that can be absorbed. When it does not work as it should, undigested carbohydrates ferment in the gut, causing gastrointestinal symptoms and nutrient malabsorption.

Although CSID is often thought of as rare, it is far more common than most people realise. Yet here in Australia, awareness remains incredibly low.

Many Australians are living with lifelong digestive symptoms such as bloating, pain, diarrhoea, constipation, gas, reflux, and fatigue, only to be told repeatedly that they have “IBS” with no real explanation or means for improvement. Because the symptoms overlap so closely with IBS, CSID is often missed or misdiagnosed, leaving people to continue suffering without answers rather than addressing the underlying cause.

As a nutrition scientist specialising in CSID and working with patients across Australia, I have seen just how misunderstood this condition is, even within the health system.

Why Expert Support Matters for IBS or CSID in Australia

CSID is not as simple as “avoiding sugar.” The sucrase-isomaltase enzyme breaks down both sucrose and starch. Many people with CSID react not only to table sugar, fruit, and desserts, but also to “healthy” foods such as brown rice, sweet potatoes, wholegrain bread, pumpkin, and carrots.

This is where things get tricky, and where most clinicians are caught off guard.

My background in biochemistry and metabolism means I understand the chemical structure of carbohydrates, which helps me explain why some are better tolerated than others and why certain foods may still cause symptoms even when enzyme supplements are used.

I understand how certain compounds in foods can influence sucrase-isomaltase enzyme activity, a factor often overlooked in standard dietary advice. Understanding these biochemical pathways allows me to create more precise, sustainable nutrition strategies for people with CSID.

I also draw on an advanced understanding of phytonutrients and their impact on gut health, the microbiome, cardiovascular health, and long-term disease prevention. This means I can guide clients toward nutrient-rich swaps that not only reduce symptoms but also support overall wellbeing and longevity.

Many of the diet plans and articles about CSID found online, even those written by health professionals, are overly restrictive or contain misinformation. Most simply remove all foods that contain sucrose and starch, without considering enzyme activity or tolerance levels. They also fail to include suitable swaps that provide similar nutrient profiles, which can lead to nutrient deficiencies and worsened gut symptoms, particularly when colourful fruits, vegetables, and nuts are excluded.

It takes an in-depth understanding of biochemistry, metabolism, and clinical nutrition to translate the science into a practical, sustainable plan that truly works. My goal is to help people identify safe swaps and tolerable portions so they can rebuild a diverse, nourishing diet rather than living in constant restriction.

Following the wrong diet can:

• worsen symptoms

• trigger nutritional deficiencies

• lead to fear and confusion around food

• create long-term gut sensitivity

  
  

It is essential that people with CSID, or suspected CSID, receive guidance from someone who actually specialises in the condition.

Diagnosis is improving in Australia

Until recently, testing for CSID was difficult to access in Australia. Now, genetic testing and biopsy enzyme analysis are becoming more widely available, with many gastroenterologists beginning to include disaccharidase enzyme testing during upper gastrointestinal (GI) endoscopies.

These developments mean more Australians are finally getting answers after years of unexplained symptoms and misdiagnosis.

Genetic Testing and Diagnosis for Sucrase-Isomaltase Deficiency in Australia

For many Australians, confirming a diagnosis of Congenital Sucrase-Isomaltase Deficiency (CSID) is now easier than ever. Genetic testing for the sucrase-isomaltase (SI) gene is available in Australia and can identify variants that affect enzyme function. This type of testing can help explain ongoing IBS-like symptoms that have not improved with standard therapies or dietary changes.

As part of my clinical practice, I can arrange or coordinate genetic testing for the sucrase-isomaltase (SI) gene, helping clients confirm their diagnosis and better understand their individual enzyme profile.

An accurate diagnosis can completely transform quality of life, especially when paired with expert dietary support that considers Australian foods, products, and cultural eating patterns.

You are not alone and you deserve care that works

CSID can feel isolating. Many people tell me they have been dismissed or had their symptoms downplayed by health professionals who are unfamiliar with the condition. Some have even been told that their biopsy or genetic test results must be wrong, despite these being considered the gold standard for diagnosis.

This lack of understanding can be deeply frustrating, especially after years of searching for answers. But with the right plan, symptom control is possible, and eating can become enjoyable again.

If you have been diagnosed with IBS that hasn’t improved with standard therapies, or suspect CSID or ASID, you deserve help from someone who understands this condition deeply and keeps up with the fast-evolving research, not outdated assumptions.

I am based in Australia and specialise in CSID, providing personalised support through a science-based, compassionate approach. If you would like to learn more or book a consultation, you can visit my CSID Book Online page.

For Dietitians and Health Professionals

If you are a dietitian or health professional who would like to upskill in CSID, I offer education, resources, and case support. This condition is more common than most realise, and understanding it properly can transform the care you provide for patients who have struggled for years without answers.

To learn more about collaboration or professional training opportunities, please get in touch.