A recent study and editorial in The American Journal of Gastroenterology (AJG) revisit a question that sits at the heart of modern functional GI care:
When patients with disorders of gut–brain interaction (DGBI) say they’re “intolerant” to certain carbohydrates, how often is that backed by objective malabsorption—and does it matter clinically?
The answer from this work: carbohydrate malabsorption measured on standardized breath tests is common in DGBI and strongly linked to symptom burden and quality of life.
That’s important for anyone building a diagnostic pathway for chronic bloating, IBS-like symptoms, and other functional presentations—and it directly reinforces the diagnostic paradigm CDI uses in its carbohydrate malabsorption program.
The Study in Brief: 301 DGBI Patients, Standardized Carb Breath Tests
The AJG article by Mikhael‑Moussa et al. prospectively followed 301 patients with DGBI referred to a hospital physiology unit between May 2022 and December 2023.
Each patient completed:
- A glucose SIBO/IMO breath test, then
- Lactose malabsorption (25 g) and fructose malabsorption (25 g) breath tests
During each carbohydrate malabsorption breath test, patients rated five key symptoms—pain, nausea, bloating, flatulence, and diarrhea—using a visual analog scale and the Adult Carbohydrate Perception Questionnaire.
The authors defined:
- Carbohydrate intolerance as a ≥20 mm increase in at least one symptom score during the test.
- Lactose malabsorption and fructose malabsorption based on standard breath test gas patterns.
Key findings
- 59.1% of patients met criteria for carbohydrate intolerance.
- Compared with non-intolerant patients, carbohydrate-intolerant patients were:
- More likely to be female
- More likely to have ≥2 DGBI diagnoses
- More likely to show lactose malabsorption and fructose malabsorption on breath testing
- More symptomatic, with higher IBS and somatic symptom severity
- More impacted, with a lower quality of life
On multivariable analysis, two factors remained independently associated with carbohydrate intolerance:
- Lactose malabsorption on breath testing
- Somatic symptom burden
Simply put: in this DGBI cohort, objective carbohydrate malabsorption and symptom-defined intolerance go hand-in-hand, and patients in that overlap group carry a heavier overall burden of disease.
The Editorial: Malabsorption vs Intolerance
In the AJG editorial, the author drew a distinction that matters for everyday practice:
- Carbohydrate malabsorption/maldigestion
An objective physiological issue (e.g., lactose or fructose not adequately digested/absorbed), measured via standardized breath testing. - Carbohydrate intolerance
The subjective experience—pain, bloating, diarrhea, nausea—patients report when they ingest those carbohydrates.
The editorial’s core message:
- Some patients have both malabsorption and intolerance.
- Some are intolerant without clear malabsorption (highlighting gut–brain and hypersensitivity mechanisms).
- Some have malabsorption but relatively fewer symptoms.
Rather than arguing “for” or “against” breath testing, the editorial reinforces a balanced view:
- Properly standardized lactose and fructose breath tests remain clinically useful in DGBI.
- Results should be interpreted in the broader context of diet, symptoms, psychosocial factors, and patient goals—not in isolation.
For clinicians, this is essentially a green light for carbohydrate breath testing used thoughtfully inside a DGBI framework.
How This Supports CDI’s Carbohydrate Breath Testing Program
The AJG paper and editorial do not name individual labs or compare commercial platforms—that wasn’t their purpose. But they provide important class-level validation for the kind of testing CDI delivers.
1. The diagnostic paradigm CDI uses is clinically meaningful
CDI’s HMBT Program includes testing for lactose, fructose, and sucrose malabsorption, as well as glucose and lactulose for SIBO/IMO, all under a single standardized program.
The AJG study shows that, in DGBI patients:
- Lactose maldigestion and fructose malabsorption measured on breath tests are independently associated with:
- Symptom-defined carbohydrate intolerance
- Higher IBS symptom scores
- Lower quality of life
That doesn’t tell you which lab to use—but it does confirm that CDI’s breath tests for carbohydrate malabsorption measure and map something clinically real and important, not just a lab artifact.
2. Carbohydrate malabsorption belongs within a structured functional GI pathway
CDI has intentionally positioned its HMBT Program as a functional GI diagnostic engine for IBS-like, bloating, and unexplained GI symptoms—not as a single “SIBO test.”
The AJG data align with that approach:
- Carbohydrate intolerance affects a substantial proportion of DGBI patients.
- Those patients tend to be sicker and more impacted.
- Objective malabsorption is part of that picture and can be identified non-invasively.
In practice, that means it’s reasonable to treat carbohydrate malabsorption as a first-class citizen in your DGBI workups—alongside SIBO/IMO and other drivers—not as an afterthought.
3. Standardized, defensible protocols matter
CDI’s program is built around:
- A CLIA-certified lab using gas chromatography with CO₂ correction
- Consensus-aligned protocols and dosing for breath testing
- Education (Breath Testing Done Right, the CDI Primer, Modern Gastro) to help clinicians use the modality appropriately
The AJG study’s reliance on defined lactose and fructose doses (25 g each), serial sampling and structured symptom measurement, and clear definitions of malabsorption and intolerance mirrors the type of rigor CDI emphasizes when we talk about “breath testing done right,” not ad hoc or non-standard approaches.
In other words: we are implementing the same kind of standardized testing paradigm now being affirmed in top-tier GI literature.
From Evidence to Everyday Practice
For GI groups, integrative and functional medicine practices, ND/RD clinicians, and pediatric GI programs, the real challenge is not deciding whether an AJG article is interesting—it’s making the underlying evidence usable.
That’s where CDI’s Adult and Pediatric HMBT Programs come in:
- Comprehensive menu in one program
Adult hydrogen & methane breath testing for:- SIBO/IMO (glucose and lactulose)
- Carbohydrate malabsorption (lactose, fructose, sucrose)
- Rigorous lab and fast turnaround
- CLIA-certified central lab using gas chromatography with CO₂ correction
- 1 business day result turnaround once samples are received, so data arrives in time to influence the next step in care
- Workflow and follow-through layer
- MyGI Gateway for ordering, tracking, and results
- Patient prep support and outreach designed to improve completion and reduce “test never came back” waste
- Clear affordability story
- Max $299 out-of-pocket for breath tests to reduce cost-related friction and drop off, alongside strong coverage where applicable out‑of-pocket cap off, alongside strong coverage where applicable
- Education-led partnership
- Practical education and support so teams can integrate breath testing into a defensible, standardized DGBI pathway, not just “order a kit.”
The AJG study and editorial confirm what many clinicians have suspected: standardized carbohydrate breath testing remains a relevant, clinically meaningful tool in DGBI care.
CDI’s work is to make that tool:
- Easier to complete
- Faster to interpret
- Simpler to integrate into your existing workflows
- More defensible to patients, peers, leadership, and payers
Now you can move patients from “I think I’m intolerant” to clearer answers and next-step decisions—without creating operational challenges.
