Background and aims: A whey protein/guar preload (Omniblend Innovation) has been developed recently to reduce postprandial glycaemia. The preload comprises 5g guar, 20g (whey) protein and 3g lactose (total 90kcal) in a sachet, which is added to a ‘shake and take’ cup containing 150ml water. Our previous trial suggested that this supplement slowed gastric emptying (GE), but the latter was assessed using a stable isotope breath test technique which limits the capacity to discriminate between slowing of GE and a delay in intestinal absorption. Our aim was to determine the effects of this guar/whey protein preload on GE (using the ‘gold standard’ technique, scintigraphy), and the glycaemic/ insulinaemic responses to an oral glucose load in healthy older people. Materials and methods: Ten healthy older participants (6F, 4M; age: 74.0 ± 1.6 yr; BMI: 26.0 ± 0.7 kg/m2) with normal glucose tolerance underwent concurrent measurements of GE, plasma glucose and insulin for 180 min on two occasions. Participants were studied after an overnight fast, were seated with their back against a gamma camera and a cannula inserted into an antecubital vein for blood sampling. In random order, each received a test drink comprising 50g glucose made up to 300ml with water containing 20MBq 99mTc-calcium-phytate with or without the guar/whey protein preload (90kcal) made up to 150ml with water, ingested 15 min before the test drink. Blood samples were taken immediately before the preload, before the glucose test drink and at 15-30 min intervals thereafter until t=180 min. The early insulin secretory response was estimated by the ratio of the change in insulin (ΔI0-30) to that of glucose at 30 min (ΔG0-30) represented as ΔI0-30/ΔG0-30. Data are mean values ± SEM. Results: The guar/whey protein preload reduced both the iAUC0-120 (P<0.05) and peak glucose (control: 9.4 ± 0.5mmol/L vs preload: 8.6 ± 0.5 mmol/L; P=0.01) (Figure), but had no effect on the GE 50% time (control: 86.4 ± 8.0 min vs preload: 85.4 ± 4.0 min; P=NS). The rise in plasma insulin tended to be higher (e.g. iAUC0-30 control: 435.5 ± 70.3 vs preload: 637.5 ± 118.1 U/L.min; P=0.08), and the ΔI0-30/ΔG0-30 ratio was greater (control: 10.3 ± 2.2 vs preload: 18.5 ± 2.5; P=0.01), after the preload. Conclusion: In healthy older people, the glucose-lowering effect of the whey protein/guar preload appears unrelated to changes in GE and may reflect increased insulin secretion and/or slowing of small intestinal absorption.