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