Study to Evaluate the Efficacy of a Polyamine-deficient Diet for Treating Postoperative Pain After Abdominal Surgery

Inclusion Criteria: * Adult (\>18 years) * Indication for a " major " abdominal surgery as second surgical procedure : cure of eventration and restoration of digestive continuity * Intended Use of a Patient Controlled Morphine Pump (PCA) postoperatively or taking oral opioids * Possible follow-up during 7 months (post-operative consultation at 1 month and 6 months only if postoperative pain or complications) * Written informed consent form obtained from the patient * Affiliated to the social security Exclusion Criteria: * Pregnant women * Minor, adult under guardianship or benefiting from a legal protection * Oncological surgery * Surgery not painful (cholecystectomy, hernia, thyroidectomy, bariatric surgery) * Drug addicts patients, or under opiate dependency * Chronic pain patients (pain over 3 months) * Patients in nursing home or convalescence home (diet non possible in institution) * Planned hospitalisation before the intervention (during the 7 days before the surgery) * Severe undernutrition defined by the HAS criteria (weight loss \> 10% in 1 month and/or \> 15% in 6 months, albumin at inclusion \<15g/l) * Patient refusing the possibility to change his eating habits * Oral feeding impossible preoperatively * Patient not able to express himself on their pain (silent, …) * Decompensated psychiatric pathologies (severe depression syndrome,…) * Patient unable to understand the protocol and/or to give his informed consent