In a randomized double-blind placebo-controlled trial in single centre , patients referred for elective colorectal cancer surgery received either an n-3 FA-enriched oral nutritional supplement ( ONS ) ( Supportan , 200 ml twice daily ) providing 2.0 g eicosapentaenoic acid ( EPA ) and 1.0 g docosahexaenoic acid ( DHA ) per day , or a standard isocaloric and isonitrogenous ONS , for 7 days before and 7 days after surgery .