Postmastication digestion factors influence glycemic variability in humans

The glycemic response (GR) to food is influenced by both intrinsic and extrinsic factors. A consistent observation in GR studies is the wide within- and between-individual variations. The authors hypothesize that between-individual variations in the GR, insulin response (IR) and gastric emptying occur even when food particle size is standardized. Volunteers were tested on 2 nonconsecutive days after an overnight fast in randomized order. On 1 day, the volunteers consumed large (>2000 μm) rice particles, and on the second day, small rice particles (500-1000 μm). Subsequently, gastric emptying using the sodium [(13)C] acetate breath test (for 240 minutes) and GR and IR (for 120 minutes) from finger-prick blood samples were measured. The incremental area under the curve (IAUC) for the GR for small particles varied 45% more compared with whole rice. The small particles elicited a significantly greater GR IAUC than the large particles. The standard deviations associated with the IR IAUC for the small particles was 140% greater than that of the large particles. The total IAUC for IR was also significantly greater for the small particles than the large particles. The between-individual variations associated with gastric emptying times were similar for both samples. The gastric emptying latency phase, lag, and half time were significantly shorter for the small particles. Ingesting small particles causes faster gastric emptying and produces greater glycemic and IRs. Between-individual variations in GR and IR can be observed even when all the food associated factors including ingested particle size (mastication) are controlled for in humans.