The Glycemic and Insulinemic Index of Plain Sweet Biscuits: Relationships to in Vitro Starch Digestibility

BACKGROUND: Among the various classes of processed starchy foods, wheat-based cereal products exhibit a wide range in glycemic and insulinemic responses. Understanding starch behavior during cooking and processing may help identify strategies that lower postprandial glycemia and insulinemia. OBJECTIVE: To determine the relationship between the in vivo glycemic index (GI)/insulinemic index (II) and in vitro digestibility and composition characteristics (rapidly available glucose and slowly available glucose, RAG and SAG respectively) of 24 plain sweet biscuits (cookies). METHODS: The products were commercially available and selected on the basis of their high starch content. In vivo responses (GI and II) were measured by standardised methods over 7 studies, with 12 subjects in each study (30 males, 42 females). In vitro digestibility characteristics were measured by the Englyst procedure. RESULTS: The observed GI ranged from 38 to 60 (low to moderate) with the majority between 40 and 50, and correlated strongly with the observed insulinemic index (r = 0.76, P < 0.0001). The digestibility profile of carbohydrates was significantly correlated to in vivo responses (SAG and GI: r = -0.41; p = 0.04; SAG and II: r = -0.52; p < 0.01; RAG and GI: r = 0.5; p = 0.01; RAG and II: r = 0.34; p = 0.1) and explained in vivo responses better than fat, protein and fiber content amongst this selection of plain sweet biscuits. CONCLUSION: The findings indicate that plain sweet biscuits have a low GI and a moderate II and that these characteristics are correlated to in vitro starch digestibility and are dependent on the type of processing.