The effect of dietary interventions on pain and quality of life in women diagnosed with endometriosis: a prospective study with control group

STUDY QUESTION: What is the influence of dietary interventions, namely the low fermentable oligo-, di-, mono-saccharides, and polyols (Low FODMAP) diet and endometriosis diet, on endometriosis-related pain and quality of life (QoL) compared to a control group? SUMMARY ANSWER: After adhering to a dietary intervention for 6 months, women with endometriosis reported less pain and an improved QoL compared to baseline whereas, compared to the control group, they reported less bloating and a better QoL in 3 of 11 domains. WHAT IS KNOWN ALREADY: Standard endometriosis treatment can be insufficient or may be accompanied by unacceptable side effects. This has resulted in an increasing interest in self-management strategies, including the appliance of the Low FODMAP diet and the endometriosis diet (an experience-based avoidance diet, developed by women with endometriosis). The Low FODMAP diet has previously been found effective in reducing endometriosis-related pain symptoms, whereas only limited studies are available on the efficacy of the endometriosis diet. A survey study recently found the endometriosis diet effective in improving QoL but currently no guidelines on use of the diet exist. STUDY DESIGN, SIZE, DURATION: A prospective one-center pilot study was performed between April 2021 and December 2022. Participants could choose between adherence to a diet—the Low FODMAP diet or endometriosis diet—or no diet (control group). Women adhering to a diet received extensive guidance from a dietician in training. The follow-up period was 6 months for all three groups. For all outcomes, women adhering to the diets were compared to their baseline situation and to the control group. PARTICIPANTS/MATERIALS, SETTING, METHODS: We included women diagnosed with endometriosis (surgically and/or by radiologic imaging) who reported pain scores ≥3 cm on the visual analogue score (0–10 cm) for dysmenorrhea, deep dyspareunia, and/or chronic pelvic pain. The primary endpoint focused on pain reduction for all pain symptoms, including dysuria, bloating, and tiredness. Secondary endpoints, assessed via questionnaires, focused on QoL, gastro-intestinal health, and diet adherence. MAIN RESULTS AND THE ROLE OF CHANCE: A total of 62 participants were included in the low FODMAP diet (n = 22), endometriosis diet (n = 21), and control group (n = 19). Compared to their baseline pain scores, participants adhering to a diet reported less pain in four of six symptoms (range P < 0.001 to P = 0.012) and better scores in 6 of 11 QoL domains (range P < 0.001 to P = 0.023) after 6 months. Compared to the control group, analyzed longitudinally over the 6-month follow-up period, participants applying a diet reported significant less bloating (P = 0.049), and better scores in 3 of 11 QoL domains (range P = 0.002 to P = 0.035). LIMITATIONS, REASONS FOR CAUTION: No sample size was calculated since efficacy data were lacking in the literature. In order to optimize dietary adherence, randomization was not applied, possibly resulting in selection bias. WIDER IMPLICATIONS OF THE FINDINGS: Our study suggests that women could benefit from adherence to a dietary intervention, since we found lower pain scores and better QoL after 6 months. However, caution is implied since this is a pilot study, no sample size was calculated, and data on long-term effects (>6 months) are lacking. The results of this pilot study underline the importance of further research and the drawing up of guidelines. STUDY FUNDING/COMPETING INTEREST(S): A.v.H. reports receiving a travel grant from Merck outside the scope of this study. J.W., S.V., J.T., and B.D.B. have no conflicts of interest to report. A.d.V. reports having received KP-register points for internship guidance of J.W., performing paid consultations with endometriosis patients outside the study and receiving reimbursements for educational lectures at the local hospital (Albert Schweitzer Ziekenhuis, Dordrecht, the Netherlands). A.S. reports having received expenses for travel and hotel costs as an invited speaker from ESHRE. This was outside the scope of this study. M.v.W. reports that she is a Co-Ed of Cochrane Gynecology and Fertility. V.M. reports receiving travel and speaker’s fees from Guerbet and research grants from Guerbet, Merck and Ferring. The department of reproductive medicine (V.M.) of the Amsterdam UMC, location VUmc, has received several research and educational grants from Guerbet, Merck and Ferring not related to the submitted work. TRIAL REGISTRATION NUMBER: N/A.