This study was planned to determine the oxidative damage, biochemical changes which can be occured in kidney tissue of rats which the experimental diabetic were created and whether the protective effect of kefir to these changes.
In order to create diabetic, 65 mg/kg single dose of streptozotocin (STZ) intraperitoneally (i.p.) was induced to rats in SF treated diabetic group and kefir treated diabetic group. The same amount of saline was injected to control group and kefir kontrol group. Rats which have 250 mg/dl blood glucose and over 250 mg/dl were considered as diabetic and included to study. Kefir was given as 10 ml/kg/day during 35 days to rats in control kefir group and kefir treated diabetic group. At the start of the study, levels of blood glucose and weights of rats were measured. Blood glucose, urea, creatinine, sodium, chlorine parameters of rats were measured besides glucose, creatinine, microalbuminuria and sodium parameters in the urine by decapitating on 36th day of the study. Fractional water excretion (Fewater) and glomerular filtration rate (GFR) were calculated by results of blood and urine tests. Levels of superoxide dismutase (SOD), catalase (CAT) and glutathione (GSH) obtained from kidney tissue of groups were measured. 
Kefir was decreased the damage caused by diabetes. These results indicate that Kefir supplement may provide to better control of oxidative stress, which is related with the improvement of renal functions, suggesting its use as a non-pharmacological adjuvant to slow down the progession of diabetic nephropathy.

The effects of kefir on the renal functions of rats with experimental diabetes mellitus