Malnutrition is frequently seen in patients on chemotherapy suffering from gastric/colorectal cancer and may worsen the outcome. EPA, a sort of ω-3 PUFA, can modulate immune system. EPA also antagonizes metabolic and inflammatory changes induced by the tumor. This study is to test whether EPA, in combination with enteral nutrition, can improve nutritional/immunologic status, quality of life, and reduce chemotherapy related side effects of these patients.