in this randomized double blind placebo controlled clinical trial , 65 men with type 2 diabetes , aged 33 - 63 years , were enrolled into the study between april 2 and june 27 , 2008 . ethical approval was obtained from the medical ethics committee of tehran university of medical sciences and informed consent was obtained from all individuals . the participants were instructed not to take any -3 fatty acids and antioxidant supplements during , and 2 weeks preceding the study . exclusion criteria included onset of nephropathy , myocardial infarction , coronary bypass grafting and inflammatory diseases . venous blood samples were obtained from all participants at 8:00 - 9:00 a.m. , after 10 hours of fasting , at the baseline and after intervention . subjects received 500 mg epa and/or 200 mg vitamin c or placebo depending on their groups . for a period of 8 weeks , 15 participants received daily epa supplements with vitamin c ( group 1 ) , 16 took epa supplements and vitamin c placebo ( group 2 ) , 17 took epa supplement placebo and vitamin c ( group 3 ) , and 17 received epa supplement placebo and vitamin c placebo ( group 4 ) . the vitamin c and their placebo soft gels were obtained from darou pakhsh pharma chem . plasma glucose was determined by a glucose analyzer ( ysi , yellow springs , oh ) . hba1c levels were measured by immuneturbidimetric immunoassay ( unimate ; roche diagnostics , indianapolis , in ) with a normal range of 4.5 - 6.1% . bmi was calculated from this formula : [ weight ( kg)/hight ( m ) ] . blood pressure ( bp ) was measured twice in a seated position after 15 minutes of rest using a standard mercury sphygmomanometer . microsoft excel was used for data handling and spss ( version 10 ; spss inc . , sixty - nine diabetic men with a mean age of 48 years ( range : 33 - 63 years ) were recruited . mean  sd plasma levels of fbs , hba1c , tc , ldl - c , hdl - c , tg and bp are presented in table 2 . there were significant decreases in fbs , hba1c , ldl - c and tg in groups 1 ( p < 0.01 ) , 2 ( p < 0.01 ) , 3 ( p < 0.01 ) and 4 ( p < 0.01 ) , but significant decreases in tc was shown in groups 1 ( p < 0.01 ) , 2 ( p < 0.01 ) and 3 ( p < 0.01 ) , not in group 4 . there was a significant increase in hdl - c in all groups ( p < 0.01 ) . there were significant differences in fbs between groups 1 and 2 ( p < 0.05 ) , groups 1 and 3 ( p < 0.05 ) and groups 2 and 4 ( p < 0.05 ) . ldl - c was significantly different between group 1 and other groups ( p < 0.01 ) . there were significant differences in hdl - c level between group 3 and other groups ( p < 0.05 ) , and tg level was significantly different between groups 1 and 2 ( p < 0.01 ) , groups 2 and 3 ( p < 0.05 ) , groups 2 and 4 ( p < 0.01 ) , and groups 3 and 4 ( p < 0.01 ) , but no difference in hba1c , tc and bp was seen between the groups after 8 weeks of intervention ( table 3 ) . characteristics of subjects [ mean ( sd ) ] comparisons of parameters in the groups before and after 8 weeks of supplementation [ mean ( sd ) ] multiple comparisons of parameters among groups after 8 weeks of supplementation [ mean ( sd ) ] this randomized double - blind placebo controlled clinical trial in diabetic patients demonstrated a decrease in all variables in four groups except for tc in group 4 and an increase in hdl - c in all groups , although bp did not change in any group , following 8 weeks of supplementation . these results suggest that epa with or without vitamin c can improve the cardiovascular markers in plasma , but alone or along with vitamin c can not reduce the blood pressure . these findings are consistent with the results of some previous studies.1516 others however , reported no effect or a harmful effect17 for increased -3 fatty acid intake . potential mechanisms for the cardio - protective effects of -3 fatty acids include anti - thrombotic , anti - inflammatory and anti - arrhythmic effects , as well as its effects on lowering blood pressure ( bp ) , and reducing plasma triglycerides ( tg ) levels.18 in addition , higher epa quantities in the phospholipid cell membranes could increase insulin sensitivity.19 some studies showed that fish oil rich in epa and dha lowers blood pressure . metaanalyses of controlled trials on fish oil supplementation suggested that the bp - lowering effect in hypertension is both dose- ( > 3 g / d ) and time - dependent.2021 many epidemiologic and interventional studies have assessed the relations and effects of the intake of -3 fatty acids2223 on cvd biomarkers in a variety of populations . healthy subjects and those at high risk for chd , including diabetic patients and patients who had suffered a myocardial infarction ( mi ) have been evaluated . reductions in cvd have been observed with two servings of fish per week , 1.8 g / day of epa as an ethyl ester and 1 g / day of an 85% epa + dha concentrate in the form of an ethyl ester.2425 the results of the present study also showed significant differences in fbs between groups 1 and 2 ( p < 0.05 ) , groups 1 and 3 ( p < 0.05 ) and groups 2 and 4 ( p < 0.05 ) . furthermore , there were significant differences in ldl - c between group 1 and other groups ( p < 0.01 ) . a significant difference in hdl - c was seen between group 3 and other groups ( p < 0.05 ) and in tg between groups 1 and 2 ( p < 0.01 ) , groups 2 and 3 ( p < 0.05 ) , groups 2 and 4 ( p < 0.01 ) , and groups 3 and 4 ( p < 0.01 ) , too . individual fatty acids have large effects on physiologic functions that are determined by a collection of chain length , number and position of double bonds , and isomerism around these bonds . one of the possible mechanisms is that -3 fatty acids vary from -6 fatty acids in their effects on plasma lipids , bp , and other biomarkers of cvd risk such as lipoprotein ( a ) , inflammatory markers , fasting plasma glucose and insulin , and clotting factors.26 in many studies , mechanisms potentially responsible for these effects have been examined . epa constitutes part of the cell membrane , replacing other mostly unsaturated fatty acids there , and so modifying cellular function . hence , a number of variations of cell function can be observed upon inclusion of epa into the cell membrane . among them are the shift of the eicosanoid system towards vasodilatation and less inflammation , a lowering of blood tg and anti - arrhythmic effects.27 clinical trial data provide evidence on the favorable effects of -3 fatty acids in reducing the risk of chd . the gissi - prevention trial is one of the largest clinical trials to test the efficacy of -3 fatty acid supplementation for secondary prevention of chd.28 the trial included 11,324 subjects with a recent mi who were assigned to either -3 fatty acid supplements ( 850 mg / d ) , tocopherol ( 300 mg / d ) , both or none for 3.5 years along with a mediterranean diet . the mediterranean diet emphasizes less meat consumption with more bread , vegetables , fruit , and fish intake . -3 fatty acid supplementation decreased all - cause death by 20% and stroke by 15% . on the other hand , evidence from three epidemiologic studies , the nhanes i follow - up study29 and the jphc study cohort i30 did not show any significant decrease in chd incidence with increasing intakes of fish . in conclusion , this study showed that 8 weeks of taking epa + vitamin c supplementation improved the plasma levels of cardiovascular markers but did nt reduce bp . mmsm did the laboratory procedures and statistical analysis and prepared the first version of manuscript . sad , sak , mre , aasy , ga , and rg supervised the project with association of md .
background : eicosapentaenoic acid ( epa ) is the principal -3 fatty acids in marine oils . fasting blood sugar ( fbs ) , hba1c and some of the plasma lipids and lipoproteins has been negatively related to the intake of -3 fatty acids and ascorbic acid , in some studies . 
 therefore , the purpose of this study was to assess the effects of epa and/or vitamin c on glycemic indices , blood pressure , and plasma lipids in type 2 diabetic iranian males.methods:sixty five men with type 2 diabetes were enrolled into the study between april 2 and june 27 , 2008 . 
 venous blood samples were obtained from all participants after 10 hours of fasting , at the baseline and after the intervention . 
 subjects received 500 mg epa and/or 200 mg vitamin c and/or placebo depending on their groups . for eight weeks , 
 15 participants received epa supplements with vitamin c ( group 1 ) , 16 took epa supplements and vitamin c placebo ( group 2 ) , 17 took epa placebo and vitamin c ( group 3 ) , and 17 received epa placebo and vitamin c placebo ( group 4 ) , daily.results:there were significant decreases in fbs , hba1c , ldl - c and tg in groups 1 , 2 , 3 and 4 ( p < 0.01 ) , but significant decreases in tc were shown only in groups 1 , 2 and 3 ( p < 0.01 ) . 
 there was a significant increase in hdl - c in all groups ( p < 0.01).conclusions : in summary , it is concluded that , eight weeks of taking epa + vitamin c supplementation improved the plasma levels of cardiovascular markers but did nt reduce bp .