The HepatoPancreaticoBiliary Resection Arginine Immunomodulation (PRIMe) Trial

Inclusion Criteria: * Patients age 18 and over at time of diagnosis * Resectable presumed liver, pancreas, or bile duct malignancy (i.e., liver metastases, HCC, cholangiocarcinoma, pancreatic or periampullary adenocarcinoma, NETs)as determined by surgeon in clinic * Anticipated hospital stay at least three days post-surgery * Ability to tolerate oral intake and comply with protocol requirements Exclusion Criteria: * Documented significant immunodeficiency due to underlying illness (e.g. HIV/AIDS) and/or medication (e.g. systemic corticosteroids, azathioprine, cyclosporin A). Subjects may be on physiologic doses of replacement prednisone or equivalent doses of corticosteroid (\<7.5 mg daily) * Subjects with resting hypotension (BP \<90/50 at rest) * History of autoimmune disease, such as but not restricted to, inflammatory bowel disease, systemic lupus erythematosus, ankylosing spondylitis, scleroderma, or multiple sclerosis * Serious, active, intercurrent chronic or acute illness, or other active illness considered by the investigator as an unwarranted high risk for an investigational product * Active infection of any site and/or active herpes requiring ongoing treatment * Known pregnancy or nursing mothers * Subjects with an allergy to the nutritional supplement or comparator including milk, fish and/or shellfish allergies * Subjects with religious or other objections to consuming fish or shellfish * Subjects with severe asthma defined as asthma not controlled with inhaled corticosteroids and additional controllers or by oral corticosteroid treatment (arginine can cause allergic response or make swelling in airways worse) * Subjects with a known inherited guanidinoacetate methyltransferase deficiency (due to an inability to convert arginine to creatine) * Subject with known current liver cirrhosis * Subjects with documented myocardial infarction or life-threatening arrhythmia * Subjects with known current cardiac failure or coronary artery disease causing unstable angina