Researchers discovered that some children have trouble digesting certain sugars because of a genetic issue affecting their intestines. When doctors tested kids with stomach problems, they found that 1 in 10 had this genetic condition, called GSID. The good news is that doctors can now identify this problem using a simple genetic test combined with a diet change and a special enzyme challenge. This discovery is important because many kids with this condition were previously misdiagnosed with other stomach disorders, meaning they weren’t getting the right treatment.

The Quick Take

  • What they studied: How common is a genetic condition that prevents the body from breaking down certain sugars, and how can doctors best identify it?
  • Who participated: Two groups: 980 patients who had genetic testing for various reasons (not stomach problems), and 148 children with chronic stomach issues who were tested specifically for this genetic condition
  • Key finding: Among children with unexplained stomach problems, 10% actually had this genetic sugar-digestion issue. Among people tested for other reasons, only 0.3% had it. When doctors used a combination of genetic testing, a special diet, and an enzyme challenge, they could reliably diagnose the condition.
  • What it means for you: If your child has chronic stomach problems that haven’t been explained, this genetic test might reveal the real cause. A simple diet change avoiding certain sugars could solve the problem, but talk to your doctor before making changes.

The Research Details

This study looked back at medical records from two different groups of patients. The first group included 980 people who had genetic testing (called whole exome or clinical exome sequencing) done for reasons unrelated to stomach problems—this helped researchers understand how common this condition is in the general population. The second group included 148 children who had been diagnosed with chronic stomach problems and received specific genetic testing for the sugar-digestion gene. By comparing these two groups, researchers could see how much more common this condition is in children with unexplained stomach issues.

The researchers reviewed all the medical records and genetic test results from 2017 to 2022 for the first group, and from May 2021 to August 2022 for the second group. They looked for mutations (changes) in the SI gene, which controls an enzyme that breaks down sugars in the intestines. They also tracked which patients improved when they followed a special diet and took a replacement enzyme.

This research approach is important because it answers a real clinical problem: many children with stomach complaints are being told they have a functional disorder (meaning their stomach works differently but there’s no obvious disease) when they actually have a specific genetic condition that can be treated. By testing both a general population and a population with stomach problems, the researchers could show that this genetic condition is much more common in kids with unexplained symptoms, suggesting doctors should test for it.

This study has several strengths: it used actual patient records and genetic testing data (not just surveys), it included a large sample size, and it tested a practical diagnostic approach that worked in real patients. However, it was conducted at a single medical center, so results might differ in other locations or populations. The study was also retrospective, meaning researchers looked back at past records rather than following patients forward over time. The findings are recent (2021-2022 data) and published in a respected gastroenterology journal, which adds credibility.

What the Results Show

The most striking finding was the difference between the two groups. In the general population (people tested for genetic reasons unrelated to stomach problems), only 0.3% had this genetic condition—meaning about 3 out of 1,000 people. However, among children specifically diagnosed with chronic stomach problems, 10% carried mutations in the SI gene—meaning 1 out of 10 children. This 30-fold difference is significant and suggests that doctors should strongly consider testing children with unexplained stomach symptoms.

When doctors used a combination approach—genetic testing plus a diet that avoided sugars the body couldn’t digest, plus a challenge with a replacement enzyme—they could reliably diagnose the condition in all cases. Every child who had the genetic mutation and followed this diagnostic approach showed clinical improvement with the diet and enzyme replacement, confirming the diagnosis.

The study also showed that this genetic condition can cause symptoms that look very similar to other common stomach disorders, which explains why many children were previously misdiagnosed. The symptoms improved once the correct diagnosis was made and appropriate treatment started.

The research demonstrated that genetic testing combined with a practical diet trial is more reliable than genetic testing alone. This matters because some people carry genetic mutations but don’t have symptoms, while others with mutations do have symptoms. The combination approach helped distinguish between people who truly needed treatment and those who didn’t. The study also confirmed that sacrosidase (a replacement enzyme) was effective for managing symptoms in affected individuals.

This research builds on previous knowledge that genetic sucrase-isomaltase deficiency exists, but it’s one of the first studies to systematically determine how common it is in children with unexplained stomach problems. Previous research often focused on severe forms of the condition or on lactose intolerance (a different sugar problem). This study shows that milder forms of this genetic condition are much more common than previously recognized and are frequently confused with other stomach disorders.

The study was conducted at a single medical center, so the results might not apply to all populations or geographic areas. The study looked backward at past medical records rather than following patients forward, which means some information might be incomplete. The researchers didn’t have detailed information about all patients’ symptoms or how long they had been experiencing problems. Additionally, the study focused on children and people who underwent genetic testing, so results might differ in adults or in populations that don’t have access to genetic testing.

The Bottom Line

If your child has chronic stomach problems (like bloating, diarrhea, or abdominal pain) that haven’t been explained by standard testing, ask your doctor about SI gene testing. This test is non-invasive (just a blood or saliva sample) and can be combined with a trial diet avoiding certain sugars. If your child does have this condition, a diet low in sucrose and starch, combined with enzyme replacement therapy, appears to be effective. Confidence level: Moderate to High for diagnosis; Moderate for treatment effectiveness based on this study.

This information is most relevant for: parents of children with unexplained chronic stomach problems, children with symptoms that don’t fit typical diagnoses, and healthcare providers who evaluate children with stomach complaints. This is less relevant for adults (though the condition can occur in adults) or for people whose stomach problems have already been explained by other conditions. People with known lactose intolerance should still discuss this with their doctor, as some people have both conditions.

If your child has this condition, symptom improvement typically begins within days to weeks of starting the special diet and enzyme replacement. However, the full benefit might take several weeks to become apparent as the digestive system adjusts. Genetic testing results usually come back within 2-4 weeks.

Want to Apply This Research?

  • Track daily symptoms using a simple scale (1-10) for bloating, stomach pain, and bowel movements. Note what foods were eaten and whether enzyme replacement was taken. This creates a clear before-and-after picture to share with your doctor.
  • Use the app to log meals and identify which foods trigger symptoms. Set reminders to take enzyme replacement before meals containing sugar or starch. Create a shopping list of allowed foods to make grocery shopping easier during the elimination diet phase.
  • Over 4-6 weeks, track symptom patterns to see if they improve with diet changes and enzyme use. Use the app to document which specific foods cause problems and which are well-tolerated. Share this data with your healthcare provider to confirm diagnosis and adjust treatment as needed.

This article summarizes research findings but is not medical advice. Genetic sucrase-isomaltase deficiency requires professional diagnosis and treatment. Do not change your child’s diet or start enzyme supplements without consulting a healthcare provider. Genetic testing should only be ordered by a qualified physician. If your child has chronic stomach symptoms, schedule an appointment with a pediatrician or gastroenterologist for proper evaluation. This information is current as of the publication date but medical understanding evolves; always consult your healthcare provider for the most up-to-date recommendations.