Background There has been controversy concerning the merits of enteral and parenteral nutrition compared with no supplementary nutrition in the management of patients with acute pancreatitis. Aim To perform a systematic review of the data from randomized controlled trials (RCTs) in acute pancreatitis that have compared enteral nutrition versus no supplementary nutrition, parenteral nutrition versus no supplementary nutrition, and enteral nutrition versus parenteral nutrition. Methods A search was undertaken in the MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials. Results Fifteen RCTs were included. Enteral nutrition, when compared with no supplementary nutrition, was associated with no significant change in infectious complications: ratio of relative risks (RR) 0.56, 95% confidence interval (CI) 0.07-4.32, P=0.58, but reduced mortality: ratio of RR 0.22, 95% CI 0.07-0.70, P=0.01. Parenteral nutrition, when compared with no supplementary nutrition, was associated with no significant change in infectious complications: RR 1.36, 95% CI 0.18-10.40; P=0.77, but reduced mortality: RR 0.36, 95% CI 0.13-0.97, P=0.04. Enteral nutrition, when compared with parenteral nutrition, was associated with reduced risk of infectious complications: RR 0.41, 95% CI 0.30-0.57, P<0.001, but no significant change in mortality: RR 0.60, 95% CI 0.32-1.14, P=0.12. Conclusion The use of either enteral or parenteral nutrition, in comparison with no supplementary nutrition, is associated with reduced mortality in acute pancreatitis. Enteral nutrition is associated with a lower risk of infectious complications when compared with parenteral nutrition.