Beneficial effects of high dietary fiber intake in patients with type 2 diabetes mellitus

Background: The effect of increasing the intake of dietary fiber on glycemi c control in patients with type 2 diabetes mellitus is controversial. Methods: In a randomized, crossover study, we assigned 13 patients with typ e 2 diabetes mellitus to follow two diets, each for six weeks: a diet conta ining moderate amounts of fiber (total, 24 g; 8 g of soluble fiber and 16 g of insoluble fiber), as recommended by the American Diabetes Association ( ADA), and a high-fiber diet (total, 50 g; 25 g of soluble fiber and 25 g of insoluble fiber) containing foods not fortified with fiber (unfortified fo ods). Both diets, prepared in a research kitchen, had the same macronutrien t and energy content. We compared the effects of the two diets on glycemic control and plasma lipid concentrations. Results: Compliance with the diets was excellent. During the sixth week of the high-fiber diet, as compared with the sixth week of the ADA diet, mean daily preprandial plasma glucose concentrations were 13 mg per deciliter (0 .7 mmol per liter) lower (95 percent confidence interval, 1 to 24 mg per de ciliter [0.1 to 1.3 mmol per liter]; P = 0.04) and mean daily urinary gluco se excretion was 1.3 g lower (median difference, 0.23 g; 95 percent confide nce interval, 0.03 to 1.83; P = 0.008). The high-fiber diet also lowered th e area under the curve for 24-hour plasma glucose and insulin concentration s, which were measured every two hours, by 10 percent (P = 0.02) and 12 per cent (P = 0.05), respectively. The high-fiber diet reduced plasma total cho lesterol concentrations by 6.7 percent (P = 0.02), triglyceride concentrati ons by 10.2 percent (P = 0.02), and very-low-density lipoprotein cholestero l concentrations by 12.5 percent (P = 0.01). Conclusions: A high intake of dietary fiber, particularly of the soluble ty pe, above the level recommended by the ADA, improves glycemic control, decr eases hyperinsulinemia, and lowers plasma lipid concentrations in patients with type 2 diabetes. (N Engl J Med 2000;342:1392-8.) (C)2000, Massachusett s Medical Society.