A randomized noninferiority trial found that a starch- and sucrose-reduced diet was noninferior to a low-FODMAP diet in improving gastrointestinal symptoms in patients with irritable bowel syndrome.

In the study, published in Nutrients, researchers randomly assigned 155 patients with irritable bowel syndrome (IBS) to follow either a starch- and sucrose-reduced diet (SSRD) (n = 77) or low-FODMAP diet (n = 78) for 4 weeks followed by a 5-month follow-up period. The primary outcome of the trial was responder rate, defined as a decrease of ≥ 50 points in the IBS Severity Scoring System (IBS-SSS) total score.

Patient characteristics included:

• Mean age: 41.0 years (SSRD) vs 43.0 years (low-FODMAP)
• Female participants: 80.5% (SSRD) vs 87.2% (low-FODMAP)
• Median disease duration: 16 years (SSRD) vs 20 years (low-FODMAP)
• IBS subtypes at baseline: IBS-C (16.8%), IBS-D (28.4%), IBS-M (34.8%), IBS-U (4.5%), unspecific functional bowel disorder (15.5%).

The study design included:

• Inclusion criteria: Rome IV IBS diagnosis, aged 18 to 70 years, and IBS-SSS > 175
• Exclusion criteria: Organic GI diseases, severe psychiatric disorders, food allergies, and current eating disorders
• Questionnaires: Rome IV, IBS-SSS, Visual Analog Scale for IBS (VAS-IBS)
• Measurements: Weight, height, waist circumference, blood pressure
• 3-day food intake records at baseline, 4 weeks, and 6 months.

At 4 weeks, responder rates were similar between the SSRD and low-FODMAP groups (79.2% vs 78.2%, P = 1.000, 95% confidence interval [CI] = –14 to 12). Both diets led to significant improvements in gastrointestinal symptoms, extraintestinal symptoms, and anthropometric measures:

• Total IBS-SSS scores decreased from baseline in both SSRD (301 to 119, P < .001) and low-FODMAP (300 to 116, P < .001) groups.
• Abdominal pain, bloating, diarrhea, and constipation improved significantly in both groups (P < .001 for most comparisons).
• Extraintestinal symptoms including fatigue, headache, and muscle/joint pain decreased (P < .05 for most comparisons).
• Weight and body mass index (BMI) reductions were more pronounced in the SSRD group (P = .006 and P = .005, respectively).

The most common comorbidities were eczema (12.3%), allergy (11.0%), and reflux/hiatus hernia (11.6%). The most frequently used medications included paracetamol (34.8%), proton pump inhibitors (31.0%), and allergy medicines (15.5%). At baseline, 50.3% of the patients were already following some type of food-restriction diet.

Detailed symptom improvements showed:

• VAS-IBS scores for abdominal pain decreased from 47 to 16 (SSRD) and 50 to 13 (low-FODMAP) at 4 weeks (P < .001 for both).
• Bloating and flatulence scores decreased from 73 to 24 (SSRD) and 73 to 19 (low-FODMAP) at 4 weeks (P < .001 for both).

Responder rates with stricter criteria at 4 weeks were:

• ≥ 100-point decrease in IBS-SSS: 67.5% (SSRD) vs 65.4% (low-FODMAP)
• ≥ 50% decrease in IBS-SSS: 55.8% (SSRD) vs 52.6% (low-FODMAP).

IBS categorization changes were observed:

• At 4 weeks, 24.7% (SSRD) and 24.4% (low-FODMAP) of patients were classified as "healthy" (IBS-SSS < 75).
• At 6 months, 40% to 50% of participants no longer met IBS criteria.

Nutrient intake changes included:

• Energy intake decreased in both groups (P < .001)
• Protein intake increased in SSRD group (P = .002)
• Fiber intake reduced in low-FODMAP group (P = .001).

Strong correlations were found between improvements in total IBS-SSS and total extraintestinal IBS-SSS (rs = 0.409, P < .001 at 4 weeks). Fatigue (rs = 0.431, P < .001) and belching/excess wind (rs = 0.419, P < .001) showed the strongest correlations with total IBS-SSS improvement at 4 weeks.

No adverse side effects were observed during the intervention; however, one of the patients in the low-FODMAP group reported worsened symptoms.

At 6-month follow-up:

• 36.4% of SSRD and 42.3% of low-FODMAP patients maintained response (P = .252).
• Weight and BMI regained, but waist circumference remained reduced in both groups.
• Diastolic blood pressure remained decreased in low-FODMAP group (P = .044).
• 52.8% of SSRD group continued with a modified SSRD, whereas 36.7% of low-FODMAP group continued with a personalized low-FODMAP diet.
• Among 34 patients who tried both diets, 64.7% preferred SSRD vs 29.4% preferring low-FODMAP (P = .032).

Sugar craving decreased more in the SSRD group (P = .050 at 4 weeks), while saturation levels were unaffected in both groups.

Limitations of the study included high dropout rates at 6 months and potential selection bias caused by recruitment methods.

One study author received consulting fees and research grants from QOL Medical LLC. The funders had no role in study design, data collection, analysis, interpretation, manuscript writing, or the decision to publish.