The effects of omega-3 fatty acids plus vitamin E and vitamin C plus zinc supplementations on glycemic control in postmenopausal women with type 2 diabetes

Outcomes of diabetes mellitus play an essential role in the pathogenesis of atherosclerosis and its complications. Persons with type 2 diabetes mellitus have lower plasma vitamins E and C levels. Lower levels of these vitamins may increase the risk of oxidative stress. In this study we assessed the effects of omega-3 fatty acids plus vitamin E and vitamin C plus zinc supplementations on glycemic control in postmenopausal women with type 2 diabetes, compared with a control group. In this 12-week double-blind placebo-controlled clinical trial, 75 postmenopausal women with type 2 diabetes from among those consulting the Iranian Diabetes Association, Tehran, participated. The subjects were randomly assigned to one of three groups, to take, daily for 12 weeks, 1.8 g omega-3 fatty acids plus 400 mg vitamin E (group 1), 5 mg zinc plus 300 mg vitamin C (group 2), or a placebo (group 3). Analysis of variance and repeated measure analysis of variance were used for inter-group comparisons and the changes in the three groups and adjustment of the other variables, respectively. At baseline, there were no significant differences in glycemic parameters among the three groups. Changes in HOMA-IR in group 1 were significantly higher than those in group 2 and the placebo group (-0.9±0.6 vs. 0.9±0.5 and 0.4±0.4, respectively) (p=0.012). After intervention, changes in fasting plasma insulin (-1.6±1.3 vs. 0.6±0.8 and 1.6±0.7 mU/l, respectively) (p=0.038) were higher in group 1, while they were lower in the other 2 groups. The supplementation caused a significant decrease in the mean changes in fasting plasma glucose in group 1 and a significant increase in group 2 (-11.1±14.1 vs. 27.9±10.9 mg/dl, respectively)(p= 0.039). Simultaneous reductions in HOMA-IR and plasma insulin as the most important cardiovascular risk factors in group 1 taking daily 1.8 g omega-3 fatty acids plus 400 mg vitamin E is encouraging, because it can have practical clinical implications. Duration of diabetes may have influenced effectiveness of the treatments.