SummaryThe purpose of this study was to evaluate the effect of xylooligosaccharide (XOS) on the blood sugar, lipids and oxidative status in type 2 diabetes mellitus (DM). A total of 26 outpatient subjects of Taichung Veterans General Hospital, Taiwan, with HbA1c levels between 7.0 and 10.0% and triglyceride Ͻ 400 mg/dL were enrolled in the present study. Subjects were supplemented with 4 g/d XOS ( n ϭ 12) or a placebo ( n ϭ 14) for 8 wk in a randomized double-blind clinical design . The results showed that the anthropometric values and nutrient intakes did not change during the experimental period. XOS supplementation not only reduced the glucose, HbA1c and fructosamine concentrations, but also decreased the levels of total cholesterol, low density lipoprotein (LDL) cholesterol, oxidized low density lipoprotein (ox-LDL) and apolipoprotein B. The activity of catalase of the erythrocyte sample decreased in the XOS group, but not the activities of superoxide dismutase and glutathione peroxidase. In conclusion, the dietary supplementation with XOS for 8 wk was effective in improving the blood sugar and lipids in type 2 diabetes, indicating that XOS-containing diets might be beneficial to DM subjects. Key Words xylooligosaccharide, sugar, lipids, type 2 diabetes, antioxidant status Dietary non-digestible oligosaccharides have gained increasing attention because they showed beneficial effects for maintaining optimum health. Xylooligosaccharides (XOS) are composed of  -1,4-linked D -xylopyranose residues. It has been demonstrated that XOS can be extensively utilized by several species of Bifidobacteria in the colon and can stimulate the growth of Bifidobacteria ( 1 , 2 ). Hsu et al. ( 3 ) reported that XOS significantly lowered the serum triacylglycerol (TG) level and increased the Bifidobacteria population in SpragueDawley rats. Campbell et al. ( 4 ) suggested that XOS showed some beneficial effects for improving gastrointestinal health by increasing the Bifidobacteria population and providing short-chain fatty acid (SCFA). SCFAs, such as acetate, propionate and butyrate, were produced by microbial fermentation and absorbed readily by the colonic mucosa. Propionate might mediate the hepatic carbohydrate metabolism, and improve the glucose tolerance and insulin sensitivity in healthy female volunteers ( 5 ). Laurent et al. ( 6 ) found that acetate and propionate decreased the plasma free fatty acid level, while they did not change the hepatic glucose production or fasting blood glucose.The aim of diet therapy in type 2 diabetes mellitus (DM) is not only to decrease body weight, but also to exert specific actions toward the main pathophysiologic disorders, such as hyperglycemia, hyperlipidemia and insulin resistance. Daily intake of 8 g fructooligosaccharide (FOS) for 14 d was reported to significantly reduce fasting blood glucose, total cholesterol and low density lipoprotein (LDL) cholesterol levels of diabetic subjects ( 7 ). On the other hand, Alles et al. ( 8 ) concluded that 15 g/d FOS supplementation for 20 d d...