Whole grain consumption reduces insulin demand, lipid peroxidation and plasma homocysteine concentrations in patients with coronary artery disease

ABSTRACT

BACKGROUND: Although current dietary guidelines recommend to increase the consumption of whole grain, these recommendations are mainly derived from the belief that replacing fats with carbohydrate may reduce risk of coronary artery disease (CAD) by improving serum lipids. Our objective was to evaluate whether the isocalorical replacement of refined rice with whole grain reduce CAD risk factors such as insulin demand and lipid peroxidation in CAD patients. METHODS: Thirty-eight male patients with CAD were provided with 70 g powder of whole grain (220 kcal) for 16 weeks, replacing cooked refined rice as a carbohydrate source of breakfast. An oral glucose tolerance test (OGTT) was performed in all subjects to determine the effect of whole grain consumption on serum concentrations of insulin and glucose in CAD patients with different degree of glucose tolerance. RESULTS: With the substitution of whole grain for refined rice, serum glucose concentrations decreased by 24% without altering body weight and energy intake. Estimates of daily fiber and vitamin E intakes increased by 24% and 50%, respectively. Whole grain consumption in CAD patients without diabetes decreased fasting glucose (22%) and the area under the curve (AUC) for insulin (26%) and glucose (19%) during an OGTT. CAD patients with diabetes also showed reductions in fasting glucose (27%) and AUC for glucose (25%) during the OGTT, compared with baseline values. Whole grain consumption reduced plasma malondialdehyde and homocysteine and urinary 8-epi-prostaglandin F 2alpha concentrations by about 30%. Lipid-corrected concentrations of alpha-carotene, retinol, alpha- and gamma-tocopherol and lycopene increased by 22-46%, compared with baseline values. Whole grain consumption decreased the percentage composition of w6 fatty acids of serum phospholipid increased by 14%. CONCLUSION: The replacement of refined rice with whole grain as a carbohydrate source of a meal showed significant beneficial effects on glucose, insulin and homocysteine concentrations and lipid peroxidation in CAD patients. These effects are likely to substantially reduce the risk factors of CAD and diabetes in CAD patients.