Moderate alcohol consumption the night before glycaemic index testing has no effect on glycaemic response. Eur J Clin Nutr. 2009;63:692-694. [PMID: 18398423 DOI: 10.1038/ejcn.2008.27]

Assessment of Glycemic Response to Model Breakfasts Varying in Glycemic Index (GI) in 5-7-Year-Old School Children

Reduced Glycemic Index (GI) of breakfast has been linked to improved cognitive performance in both children and adult populations across the morning. However, few studies have profiled the post-prandial glycemic response (PPGR) in younger children. The aim of this study was to assess PPGR to breakfast interventions differing in GI in healthy children aged 5-7 years. Eleven subjects completed an open-label, randomized, cross-over trial, receiving three equicaloric test beverages (260 kcal) consisting of 125 mL semi-skimmed milk and 50 g sugar (either glucose, sucrose, or isomaltulose). On a fourth occasion, the sucrose beverage was delivered as intermittent supply. PPGR was measured over 180 min using Continuous Glucose Monitoring (CGM). The incremental area under the curve (3h-iAUC) was highest for the glucose beverage, followed by intermittent sucrose (-21%, p = 0.288), sucrose (-27%, p = 0.139), and isomaltulose (-48%, p = 0.018). The isomaltulose beverage induced the smallest Cmax (7.8 mmol/L vs. >9.2 mmol/L for others) and the longest duration with moderate glucose level, between baseline value and 7.8 mmol/L (150 vs. <115 min for others). These results confirm that substituting mid-high GI sugars (e.g., sucrose and glucose) with low GI sugars (e.g., isomaltulose) during breakfast are a viable strategy for sustained energy release and glycemic response during the morning even in younger children.

Potential contributions of the methodology to the variability of glycaemic index of foods

Glycaemic index (GI) testing provides a useful point of comparison between carbohydrate sources. For this comparison to be meaningful, the methods used to determine GI values need to be rigorous and consistent between testing events. This requirement has led to increasing standardization of the GI methodology, with an international standard developed in joint consultation with FAO/WHO (ISO 26642:2010) currently the most up to date document. The purpose of this review is to compare the international standard to methods of published studies claiming to have performed a GI test. This analysis revealed that the international standard permits a wide range of choices for researchers when designing a GI testing plan, rather than a single standardized protocol. It has also been revealed that the literature contains significant variation, both between studies and from the international standard for critical aspects of GI testing methodology. The primary areas of variation include; what glucose specification is used, which reference food is used, how much reference food is given, what drink is given during testing, the blood sampling site chosen and what assay and equipment is used to measure blood glucose concentration. For each of these aspects we have explored some of the methodological and physiological implications of these variations. These insights suggest that whilst the international standard has assisted with framing the general parameters of GI testing, further stan-dardization to testing procedures is still required to ensure the continued relevance of the GI to clinical nutrition.

The effect of the fat and carbohydrate contents in the evening meal preceding GI testing on GI

A crossover study was designed to determine whether the fat and carbohydrate contents of evening meals consumed the night preceding glycaemic index (GI) testing had an effect on the GI. Twenty participants consumed two different evening meals in which the energy contributions from fat, carbohydrate and protein were in the ratio 50:30:15 and 25:60:15, respectively. Each participant completed eight tests that involved two evening meals with different macronutrient compositions followed the next morning by two treatments, glucose beverage or fruit bread, all carried out in duplicate. The GI of fruit bread was determined on the mornings following each of the evening meals. The GIs (95% CI) were 68 (60, 76) and 59 (52, 67) after the high-carbohydrate and high-fat meals, respectively, and were not different (P=0.11). Thus, varying the fat and carbohydrate contents of the evening meal before GI testing the next morning did not affect the GI.