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Randomized Controlled Trial
. 2025 Jun;61(12):1889-1903.
doi: 10.1111/apt.70161. Epub 2025 May 4.

Clinical Trial: Effect of a 28-Day Low FODMAP Diet on Gastrointestinal Symptoms Associated With Endometriosis (EndoFOD)-A Randomised, Controlled Crossover Feeding Study

Jane E Varney  1 , Daniel So  1 , Peter R Gibson  1 , Dakota Rhys-Jones  1 , Yuet Sang Jimmy Lee  1 , Jane Fisher  2 , Judith S Moore  1 , Roni Ratner  3 , Mark Morrison  4 , Rebecca E Burgell  1 , Jane G Muir  1
Affiliations
Randomized Controlled Trial

Clinical Trial: Effect of a 28-Day Low FODMAP Diet on Gastrointestinal Symptoms Associated With Endometriosis (EndoFOD)-A Randomised, Controlled Crossover Feeding Study

Jane E Varney et al. Aliment Pharmacol Ther. 2025 Jun.

Abstract

Background: Gastrointestinal symptoms affect most women with endometriosis, but therapeutic interventions are poorly defined.

Aims: To compare the effects of a 28-day low fermentable oligo-, di- and mono-saccharides and polyols (FODMAP) or control diet on gastrointestinal symptom severity in individuals with endometriosis and poorly controlled gastrointestinal symptoms.

Method: In this single-blinded randomised, controlled cross-over feeding trial, we randomised women aged ≥ 18 years to 28 days of either a low FODMAP (< 5 g/day FODMAPs) or control diet (20 g/day FODMAPs), both modelled on Australian Dietary Guidelines, before a ≥ 28-day washout and crossover to the alternate diet. The primary outcome was the proportion of responders defined according to the response in overall gastrointestinal symptoms on a 100-mm visual analogue scale. Secondary outcomes included gastrointestinal symptoms, quality of life and psychological status.

Results: Of 35 women randomised (mean age 31; 95% confidence interval 29, 33 years), 21 (60%) responded to the low FODMAP diet compared with 9 (26%) to the control diet (p = 0.008). In the 4th week of the dietary intervention, overall symptom scores were 35 (21, 42) mm on the low FODMAP diet and 58 (55, 65) mm on the control diet (p < 0.001). Abdominal pain, bloating, stool form and quality of life for both gastrointestinal and endometriosis-associated scales were significantly better for the low FODMAP diet compared with the control diet, but not overall for perceived stress, anxiety or depression.

Conclusions: The low FODMAP diet ameliorates gastrointestinal symptoms related to endometriosis and improves quality of life. Confirmation of these findings in a real-world setting is required.

Trial registration: The trial is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12621000153819).

Keywords: diet; endometriosis; gastroenterology; nutrition; quality of life.

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Conflict of interest statement

J.G.M., J.E.V. and P.R.G. work in a department that financially benefits from the sales of a digital application (Monash University FODMAP diet app), patient booklets, cookbooks and online courses, all of which relate to the low FODMAP diet therapy. J.G.M. and J.E.V.'s salaries are paid by the above‐stated FODMAP commercial activities. P.R.G. and R.E.B. are consultants or advisory board members for Anatara and Atmo Biosciences and have received speaker honoraria from Dr Falk Pharma. R.E.B. has also received speaker honoraria from Bayer. P.R.G. is also a consultant or advisory board member for Topas and Comvita. P.R.G. has received research grants for investigator‐driven studies and/or speaker honoraria from Atmo Biosciences and Mindset Health. P.R.G. and D.S. are shareholders in Atmo Biosciences. D.S. has received consulting and speaking honoraria from Procter & Gamble and is an employee of Atmo Biosciences. Research funding for this project came from a competitively awarded grant from the Australian Government's Medical Research Future Fund. The funder had no role in study design, data collection, analysis, interpretation or report writing. No other relationships or activities could appear to have influenced the submitted work.

Figures

FIGURE 1
FIGURE 1
Overview of the trial design. Gastrointestinal (GI). Visual analogue scale (VAS). Patient‐Reported Outcomes Measurement Information System (PROMIS). Quality of life (QOL). Gastrointestinal Quality of Life Index (GIQLI). Endometriosis Health Profile Questionnaire (EHPQ). Depression Anxiety Stress Scale‐21 (DASS 21).
FIGURE 2
FIGURE 2
Participant flow through the study. Intention to treat (ITT). Per protocol (PP).
FIGURE 3
FIGURE 3
Proportion of participants who responded to the control diet versus low FODMAP diet. Responders are defined as participants reporting a decrease of > 20 mm VAS‐IBS from baseline to the end of each dietary intervention and/or VAS‐IBS < 30 mm at the conclusion of the intervention.
FIGURE 4
FIGURE 4
The effect of dietary periods on gastrointestinal symptoms. (A) Overall gastrointestinal (GI) symptom severity, as assessed via a 100‐mm visual analogue scale (VAS) on day 7 baseline versus day 28 of the control diet or low FODMAP diet arms. Bars represent median values per intervention period, dots represent individual values per participant, and lines chart the difference in individual scores. Differences were considered significant where p ≤ 0.017. (B) Change in overall gastrointestinal symptom severity on day 28 of each dietary intervention compared to the day 7 baseline. Differences were considered significant where p ≤ 0.05. (C) Comparison of the mean of weekly averages of overall gastrointestinal symptoms as assessed daily via a 100‐mm visual analogue scale (VAS). Results across the time points for the low FODMAP diet and control diet were statistically different (p = 0.034; 2‐way analysis of variance). NS, not significant.
FIGURE 5
FIGURE 5
Gastrointestinal symptoms were assessed via visual analogue scale (VAS) daily and consolidated over the 7 days of the baseline and the final 7 days of the control diet and the low FODMAP diet (n = 25) for (A) abdominal pain/discomfort; (B) abdominal bloating; (C) wind; (D) tiredness and lethargy; (E) nausea; (F) satisfaction with stool consistency. Bars represent median values per intervention period; dots represent individual values per participant. Differences were considered significant where p < 0.006. NS, Not significant.
FIGURE 6
FIGURE 6
Comparison of stool characteristics according to the Bristol Stool Chart (BSC) between baseline, the control diet and the low FODMAP diet (n = 25). Data collected daily at baseline were consolidated over the 7 days, and comparisons were made with daily data collected over the final 7 days of each dietary intervention. Bars represent median proportions and were analysed via linear mixed models, visually shown relative to 100%. Differences were considered significant where p ≤ 0.017. NS, not significant.
FIGURE 7
FIGURE 7
Paired ratings and their differences for depression, anxiety and stress, measured via the Depression, Anxiety and Stress Scale (DASS‐21) for the intention‐to‐treat cohort during baseline, low FODMAP and control diets. Values considered within normal limits are denoted by the green shading. The paired comparisons were performed with the Wilcoxon signed‐rank test, and p‐values are shown if ≤ 0.05. Using the Bonferroni correction for comparisons across 3 dietary groups, p‐values < 0.017 were considered statistically significant.
FIGURE 8
FIGURE 8
Comparison of Gastrointestinal Quality of Life Index (GIQLI) scores on day 7 of the baseline and day 28 of the control diet and the low FODMAP diet. Bars represent median scores per intervention period; dots represent individual values per participant. Differences were considered significant where p ≤ 0.01. NS, not significant.
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