At Ignite Nutrition, we work with a lot of people who have persistent digestive symptoms — things like bloating, diarrhea, gas, and abdominal pain. It’s common for people to come to us still having symptoms even after trying all the “usual” strategies. If that sounds like you, you’re not alone. Many of our clients feel so frustrated after trying elimination diets like low FODMAP, taking probiotics, adjusting fibre, or using medications to try to ease their symptoms – but they’re still feeling stuck.
One lesser-known condition that’s been gaining attention in the digestive health world is Sucrase-Isomaltase Deficiency (SID) — also known as sucrose intolerance. While it may not be on most people’s radar, it could be a key factor in chronic gut symptoms that haven’t responded to typical treatments.
What Is Sucrase-Isomaltase Deficiency?
SID is a condition where your body has trouble breaking down sucrose (table sugar) and starches (like those in bread, pasta, rice, and potatoes). This happens when the enzymes needed to digest these carbohydrates — sucrase and isomaltase — are either not produced properly or are in short supply.
When your body can’t fully digest these carbohydrates, they ferment in the gut instead, leading to uncomfortable digestive symptoms like:
- Bloating and gas
- Cramping or abdominal pain
- Diarrhea or loose stools
- Urgency after eating
Because these symptoms are so similar to Irritable Bowel Syndrome (IBS), SID is often misdiagnosed as IBS, especially the diarrhea-predominant type (IBS-D). In fact, recent research suggests that up to 35% of people with IBS-D symptoms may actually have an underlying issue with sucrose digestion.
Many people with SID go through years of trial and error — trying medications, probiotics, and multiple elimination diets — often with only partial or short-term relief. SID remains under-recognized, in part because awareness is still growing, and diagnostic testing isn’t always accessible. But for those who’ve tried all the usual approaches with little success, it may be the something to consider.
Is It Genetic?
There is a rare, inherited form of SID called Congenital Sucrase-Isomaltase Deficiency (CSID), typically diagnosed in infants or children. But what we’re seeing more and more in adults is an acquired form of SID. This is where enzyme activity is reduced later in life due to damage to the small intestine. Things that can cause or contribute to acquired SID include:
- Gut infections (like gastroenteritis or food poisoning)
- Antibiotic use
- Inflammatory digestive conditions like celiac disease or IBD
- Chemotherapy or radiation affecting the gut
- Small Intestinal Bacterial Overgrowth (SIBO)
In these cases, the deficiency may not be permanent, but it can cause chronic or recurring symptoms if not addressed.
Could You Have SID?
Sucrase-isomaltase deficiency can be hard to detect, especially because the symptoms are so similar to other digestive issues. But there are certainly some clues you can look for to see if this might be worth investigating with your health team.
You might want to explore SID further if:
- You’ve tried the low FODMAP diet and still have bloating, gas, abdominal pain, or diarrhea
- You feel like you’re “doing everything right” with your diet but symptoms persist
- High-sugar or high-starch foods (like fruit juice, syrup, bread, pasta, potato, or rice) seem to trigger symptoms
- Symptoms tend to come on quickly — usually within 30–90 minutes of eating
- Medications or supplements like fibre, anti-diarrheals, gas-reduction medications, or antispasmodics haven’t helped much
- More serious or structural causes of digestive symptoms — like celiac disease, IBD, or abnormal imaging or bloodwork — have already been ruled out
How Is Sucrase-Isomaltase Deficiency Diagnosed?
Getting a diagnosis for SID can be tricky. Diagnosis can involve a combination of clinical assessment, symptom history, and sometimes formal testing. Unfortunately, many people with SID fall through the cracks, either because testing isn’t offered, or because their symptoms are assumed to be “just IBS.”
Testing can be limited here in Canada, but there are several tools that can help confirm a diagnosis:
- Endoscopy with enzyme testing (disaccharidase assay) – Often considered the gold standard for diagnosing SID, this test measures the activity of several digestive enzymes (including sucrase and isomaltase) directly from a small intestinal biopsy. It’s the most accurate test to detect both congenital and acquired SID.
- Genetic testing – This test looks for mutations in the SI gene that cause congenital SID (CSID). It’s especially useful in people with lifelong symptoms, a strong family history, or those who have had symptoms since childhood. While it won’t detect acquired forms of SID, it can provide clarity in suspected genetic cases.
- Sucrose Hydrogen/Methane Breath Test – This test involves drinking a sucrose-containing solution and then measuring hydrogen and methane gas in the breath over time. If the body isn’t properly digesting sucrose, it ferments in the gut, leading to gas production. While this test is non-invasive and available privately, it can be less reliable, with results affected by things like SIBO, fast transit time, or recent antibiotic use.
- 13C-sucrose breath test – This test uses a specially labeled form of sucrose that contains a carbon isotope (13C). After ingestion, the body breaks it down and produce 13CO₂, which is measured in the breath. Lower levels of 13CO₂ suggest poor sucrose digestion. While more specific than traditional breath testing, it’s not yet widely available in clinical practice in Canada and typically needs to be ordered privately.
Access to these diagnostic tests can vary widely depending on where you live. Some countries and medical centers have better availability of SID testing, while others — including many parts of Canada — have limited options. If you or your healthcare provider are considering testing, it’s a good idea to check what’s available locally or explore options for private testing where possible. Your dietitian or medical team can help guide you through this process.
How a Dietitian Can Help
If you suspect sucrase-isomaltase deficiency might be playing a role in your symptoms, this is where working with a digestive health dietitian can make a huge difference.
The dietary management of SID typically involves reducing sources of sucrose and starch — two types of carbohydrates that can be difficult to digest when enzyme activity is low. But this isn’t always as simple as cutting out sugar and bread. Everyone’s tolerance is different, and many people can still enjoy small amounts of these foods when they’re part of a balanced meal.
A dietitian will provide a clear starting point — including a list of foods to limit or modify — but we don’t stop there. We work with you to tailor the approach to your life: your cooking habits, food preferences, cultural background, and nutritional needs.
We’ll help you spot hidden sources of sugar and starch on food labels (they can be sneaky!) and make sure you’re still meeting your nutrient needs, even while cutting back on common carbohydrate foods.
If you’re unsure whether SID is really the issue, we often guide clients through a structured trial — reducing certain foods and then gradually reintroducing them to test your individual tolerance. Many people with SID can still enjoy small amounts of sugar or starch, especially when eaten alongside protein, fat, or fibre. It’s all about finding your unique balance.
In some cases, we also explore whether enzyme therapy might be helpful. Specific enzyme supplements can make it easier to digest meals that contain sugar or starch, giving you more flexibility and peace of mind when eating out or traveling.
And finally, we work closely with your doctor when needed — whether that’s helping support testing, sharing findings from your nutrition assessment, or collaborating on the best long-term plan for your gut health.
Bottom Line
Sucrase-Isomaltase Deficiency is an often-overlooked cause of digestive distress — especially in people who’ve tried the usual IBS strategies without success. While access to testing can be challenging, a trial of dietary changes and professional support can often provide helpful insights and relief.
If you’ve been struggling with unresolved symptoms, we’d love to help. Our team of gut health dietitians can work with you to explore possible food intolerances, create a realistic plan that fits your life, and help you finally get some answers.
Categorized: Gut Health & IBS
