Recently, the clinical use in artificial nutrition of omega-3 series polyunsaturated fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) present in many fish oils has been significant. EPA is a precursor to certain eicosanoid series that compensate the proinflammatory effects of the eicosanoids in arachidonic acid (omega-6 series). The objective is immunomodulation to attenuate the inflammatory response of patients without negatively impacting on the immune function. The use of enteral diets enriched with omega-3 series fatty acids (fish oil) in post-operation cancer patients showed a reduction in the number of days in hospital and infectious complications.