This is a randomised double-blinded placebo-controlled phase IV trial with two parallel treatment groups receiving either immune nutrition diet (IND) or conventional diet for 2weeks peri-radical cystectomy. Patients will be stratified according to the gender, body mass index, and the type of urinary diversion (orthotopic neobladder or ileal conduit). The primary end-point is to determine, in intention to treat analysis, the influence of IND on 90-day postoperative morbidity. Secondary study end-points will be the effect of IND on infectious as well as non-infectious complications over 90 days, compliance and adverse effects of IND. Finally, an ancillary study will be performed to evaluate whether the IND costs could counterbalance, by its benefits, the health care costs.It is envisaged to finish patients' recruitment within 24 months