Scientific Study

OBJECTIVE: To examine the relative effects of high and low glycemic index (GI) carbohydrates; and monounsaturated fats on blood glucose and lipid metabolism in NIDDM subjects. SUBJECTS: Fourteen male and seven female variably controlled NIDDM subjects recruited by advertisement. SETTING: Free living outpatients. RESEARCH DESIGN: A repeated measures; within-subject design was used such that each subject consumed three diets: (a) a high-GI diet (53% CHO -21% fat; 63 GI units (glucose= 100)); (b) a low-GI diet (51% CHO -23% fat; 43 GI units); and (c) a high-mono high-GI diet (42% CHO -35% fat; 59 GI units) in random order and cross-over fashion for four weeks. Approximately 45% energy was provided as key foods which differed in published GI values and specifically excluded legumes. Dietary fibre intake was > 30 g/d on each diet. At the end of each dietary intervention; we measured fasting plasma lipids; glucose; insulin; total glycated plasma protein; fructosamine; LDL and HDL particle size as well as 24 h urinary excretion of glucose and C-peptide. RESULTS: HDL-cholesterol was higher on the low-GI and high-mono high-GI diets compared to the high-GI diet (P < 0.05 for overall diet effect). There were no other significant differences in metabolic control between diets; even when adjusted for BMI; glucose control or gender. Body weight and saturated fat intake remained stable between dietary interventions. CONCLUSION: High-mono high-GI and high-CHO; low-GI diets are superior to high-CHO; high-GI diets with respect to HDL metabolism but no effect was noted on glucose metabolism in variably controlled NIDDM subjects.