Introduction
Gastrointestinal (GI) symptoms are common in endometriosis, affecting >75% of sufferers. These symptoms overlap with numerous GI disorders, most notably irritable bowel syndrome (IBS). Common pathophysiological mechanisms such as visceral hypersensitivity might explain this overlap. Gastrointestinal symptoms associated with endometriosis are poorly targeted by existing treatments, thus many women manipulate diet to manage symptoms. However, limited evidence supports any given dietary approach. A low FODMAP diet (LFD) is effective for managing GI symptoms in IBS, but only preliminary data support this approach in endometriosis.
Aim
To assess the efficacy of a LFD in women with endometriosis and poorly controlled GI symptoms.
Method
Design
A 12 week, single blinded crossover RCT was conducted in females aged 18 to menopause with endometriosis and poorly controlled GI symptoms (VAS >30mm) (Fig 1).
Exclusions
Recent laparoscopic surgery, other GI disorders, irregular menstrual cycle
Dietary interventions
In this feeding study, most food was supplied to participants for 28 days. Diets were matched for macronutrients, so only differed in FODMAP content. Median (95% CI) FODMAP content (g/day) of the supplied LFD and control diet was 4.60 (3.5-5.8) vs 22.5 (21.6-25.3), p < 0.01.
Analysis
Clinical data were analysed as intention to treat. Continuous endpoints were analysed using a linear mixed model. A chi-square test was used for categorical endpoints. Significance was set to <0.017 to account for multiple comparisons.
Results
34 participants were randomised, 8 withdrew and 26 completed the protocol. Median (95% CI) FODMAP intake (g/day) was not different between baseline (habitual diet) and the control diet (p=0.687), but lower on the LFD than control diet, 4.0 (3.3-4.6) vs 19.9 (18.0-20.4), p<0.001. Compared to the control diet, participants on the LFD reported less severe overall GI symptoms (Fig 2A); adequate control of GI symptoms on a greater proportion of days (Fig 2B); less severe abdominal pain and bloating (Fig 2C+2D); better QOL (Fig 2E) and reductions in perceived stress (Fig 2F). Participants reported normal stool form (Bristol Stool Chart 3-5) on 43% of days at baseline, 56% of days on the control diet (p=0.203) and 71% of days on the LFD (p=0.002).
Conclusions
A LFD diet reduces the severity of GI symptoms (including abdominal pain) in patients with endometriosis, and these changes are accompanied by a normalisation in stool form, improvements in QOL and reductions in stress. In IBS, FODMAPs distend the intestinal lumen and trigger pain and discomfort in the presence of visceral hypersensitivity. It is plausible that similar mechanisms were at play in this study. Given high rates of coexisting endometriosis and IBS, active screening for endometriosis in female patients with IBS, and IBS in patients with endometriosis is warranted.

Figure 1 - Study Design

Figure 2 - Clinical endpoints - A) Overall abdominal symptoms, B) Adequate control of GI symptoms, C) Abdominal pain / discomfort, D) Abdominal bloating, E) Quality of life, F) Stress

Daniel So

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