🟢 Strong clinical evidence (randomised controlled trial)

Study at a glance

• Participants: 223 adults
• Condition: Irritable Bowel Syndrome (IBS)
• Study type: Randomised, double-blind, sham-controlled trial
• Duration: 8 weeks

What was done

Participants with IBS took a food-specific IgG blood test. They were then randomly assigned to follow either:

• A personalised diet removing foods identified by the test, or
• A sham diet removing different foods

Neither the participants nor the researchers knew which diet was being followed until the study was completed.

What improved

After 8 weeks:

• People following the IgG-guided diet were more likely to achieve a meaningful reduction in abdominal pain compared to the control (sham) diet
• A meaningful improvement was defined as at least a 30% reduction in abdominal pain sustained over time

Additional findings:

• Overall IBS symptoms improved, including bloating and bowel-related symptoms
• The benefit appeared to be greater in certain IBS subtypes, particularly constipation-predominant and mixed IBS
• Participants who followed the diet more closely experienced greater improvement

In practical terms, this means more people achieved clinically meaningful symptom relief when following the IgG-guided diet compared to a non-targeted diet.

Key takeaway

Following a diet based on IgG test results made people with IBS more likely to achieve a meaningful improvement in abdominal pain compared to a control diet.

What this means

This study provides strong clinical evidence that removing foods identified by IgG testing may help reduce IBS symptoms. Because the study was blinded and included a control group, the results are less likely to be explained by placebo effects alone.

Important to know

This study included people who tested positive to at least one food, and results may vary between individuals. As with all dietary approaches, following the plan consistently was important for achieving the best results.

🟢 Evidence strength

Strong clinical evidence (randomised controlled trial)

Full citation

Singh et al. 2025 IBS IgG trial

Singh P, Chey WD, Takakura W, Cash BD, Lacy BE, Quigley EMM, Randall CW, Lembo A.
A novel, IBS-specific IgG ELISA-based elimination diet in irritable bowel syndrome: a randomized, sham-controlled trial.
Gastroenterology. 2025;168(6):1128–1136.e4.

Weblink:
View study

Explore other studies

• The Science Behind Food Sensitivity Testing (overview)
• Summary table of all studies
• IBS symptom improvement study (Atkinson et al. 2004)
• IBS diet comparison study (IgG vs FODMAP)
• Crohn's disease symptom improvement study
• Migraine improvement study (Alpay et al. 2010)
• Migraine inflammation study
• Professional athletes study
• Chronic symptoms survey study (York / Hardman & Hart)