Arginine/Omega-3 Fatty Acids/Nucleotides Nutritional Supplement in Treating Patients With Stage III or Stage IV Head and Neck Cancer Undergoing Chemotherapy and Radiation Therapy

DISEASE CHARACTERISTICS: * Diagnosis of head and neck cancer meeting the following criteria: * Epidermoid carcinoma * Stage III or IV disease * Must have percutaneous gastrostomy tube in place * Must have undergone prior surgery for head and neck cancer within the past 6-8 weeks * No cerebral metastases PATIENT CHARACTERISTICS: * WHO performance status (PS) 0-2 OR Karnofsky PS 60-100% * Life expectancy \> 3 months * WBC \> 4,000/mm³ * ANC \> 2,000/mm³ * Platelet count \> 100,000/mm³ * PTT ≥ 50% * Creatinine \< 130 μmol/L * Not pregnant or nursing * Fertile patients must use effective contraception * No severe sepsis * No requirement for parenteral nutrition * No pre-existing digestive pathology that results in bowel obstruction, nausea, vomiting, and/or abdominal pain \> grade 1 PRIOR CONCURRENT THERAPY: * See Disease Characteristics