Lower nocturnal blood glucose response to a potato-based mixed evening meal compared to rice in individuals with type 2 diabetes

Background & aims: Guidelines for reducing postprandial blood glucose concentrations include avoiding high glycemic index (GI) foods, such as white potatoes. However, GI testing is often undertaken in the morning with foods consumed in isolation by non-clinical cohorts. We investigated the impact of potato preparation and consumption as part of a mixed-evening meal on postprandial and nocturnal glycemic responses, and postprandial insulin response, in individuals with Type 2 Diabetes Mellitus (T2DM). Methods: In a randomized, cross-over design, 24 males and females (age 58.3 ± 9.3 y; BMI: 31.7 ± 6.8 kg/m ) with T2DM (diet or metformin controlled) completed four experimental trials after consuming a standardized breakfast (25% daily energy intake (EI)) and lunch (35% EI). Dinner (40% EI) was consumed at 1800 h being either: 1) boiled potato (BOIL); 2) roasted potato (ROAST); 3) boiled potato cooled for 24 h (COOLED); or 4) basmati rice (CONTROL). Each meal contained 50% carbohydrate, 30% fat and 20% protein. Blood samples were collected prior to, immediately post meal and at 30-min intervals for a further 120 min. A continuous glucose monitor was worn to assess nocturnal interstitial glucose concentrations. Results: No differences were detected in postprandial venous glucose area under the curve (iAUC) between CONTROL and all three potato conditions. Postprandial insulin iAUC was greater following COOLED compared to CONTROL (P = 0.003; 95% CI: 18.9–111.72 miU/mL). No significant differences between CONTROL and BOIL or ROAST were detected for postprandial insulin concentrations. All potato meals resulted in lower nocturnal glucose AUC than CONTROL (P < 0.001; 95% CI 4.15–15.67 mmol/L x h). Conclusion: Compared to an isoenergetic rice meal, boiled, roasted or boiled then cooled potato-based meals were not associated with unfavourable postprandial glucose responses or nocturnal glycemic control, and can be considered suitable for individuals with T2DM when consumed as part of a mixed-evening meal. Clinical trial registration: Australian New Zealand Clinical Trials Registry https://www.anzctr.org.au/, ACTRN 12618000480280. 2