Background & Objectives: Chemotherapeutics induce side effects in patients with cancer . In animal models the intake of ω₃ fatty acids during chemotherapy can increase the impact of chemotherapy drugs and reduce their side effects . This study was aimed to determine the fish oil�intake on side effects of chemotherapy drugs in patients with gastric cancer.

  Methods: A double blind clinical trial study on 30 adult volunteer patients (15 experiments and 15 controls) with gastric cancer was conducted during chemotherapy in Ardabil, Iran, during 2010-2011 . Experimental and control groups were selected by randomized allocation. About 3 grams ω-3 fatty acid supplementation (1.8 g Eicosapentaenoic acid & 1.2 g Docosapentaenoic acid ) and placebo were given to experimental and control groups for 6 weeks, respectively . Then, the results of data were collected at the beginning, 4 and 6 weeks after intervention of ω3/placebo in both groups and analyzed by using descriptive statistics , Chi -Square , Independent sample t-test and Cochran^,s Q test.

  Results: The results of this study showed that there were significant differences of nausea in both group of patients at the end of 6 weeks (p<0.05). A bdominal cramp and nausea significant ly decreased in experimental group during the study (p<0.05). Hair loss , vomiting and diarrhea were reduced in experimental group during the study, but these differences were not statistically significant . There were no significant differences in vomiting , diarrhea and hair loss between two groups at the end of intervention.

  Conclusion: The present study showed that the intakes of fish oil strongly reduce side effects of chemotherapy drugs such as nausea and abdominal cramp. So, this oil supplementation appears to be harmless and useful in patients with gastric cancer during chemotherapy .