Background & Objectives: Diabetes mellitus may be associated with the imbalance between protective effect of antioxidants and increased free radical production with regard to discrepancies of the findings in previous researches the present study set out to determine the changes of plasma malondialdehyde and erythrocyte antioxidant superoxide dismutase activity in patients with type II diabetes mellitus.

  Methods: This case-control study was conducted in 2005 using random sampling. 38 patients with type II diabetes mellitus who referred to 5^th Azar diabetes center and 19 age and sex matched healthy controls were selected for this study. Heparinated blood samples were taken from the cases. The separated plasma was tested for blood sugar, lipid peroxidation and blood cells (for glycolisated Hb and superoxide dismutase enzyme activity). The collected data were analyzed by SPSS (ver. 10) using t-test.

  Results: The level of plasma malondialdehyde from type II diabetes mellitus patients (6.27±0.80 nmol/ml) was significantly different from that in control group (3.56±0.98 nmol/ml)(p<0.05). Erythrocyte superoxide dismutase activity from type II diabetes mellitus patients (678.78±59.36 U/gr Hb) was significantly lower than control group (1056.47±52.98 U/gr Hb) (p<0.05).

  Conclusion: The significant difference between the increase in malondialdehyde and decrease in the activity of antioxidant enzymes in patients with type II diabetes mellitus may predispose to the development of serious complications leading to cellular damage. This suggest that diabetic patients may need more antioxidants than normal. Supplementation with medical or non-medical free radical scavengers such as vitamins E and C or foods untaining vitamin C (sitrus fruits) have a potential role in reinforcing antioxidant defence and can be important in diabetic patients.