Effects of a Low-GI Diet

August 12/Health & Medicine Week -- "Low glycemic index (GI) carbohydrates have been linked to increased satiety. The drive to eat may be mediated by postprandial changes in glucose, insulin and gut peptides," scientists in Sydney, Australia, report.

"To investigate the effect of a low- and a high-GI diet on day-long (10 hour) blood concentrations of glucose, insulin, cholecystokinin (CCK) and ghrelin (GHR), subjects (n = 12) consumed a high- and a low-GI diet in a randomized, crossover design, consisting of four meals that were matched for macronutrients and fiber, and differed only in carbohydrate quality (GI). Blood was sampled every 30-60 minutes and assayed for glucose, insulin, CCK and GHR. The high-GI diet resulted in significantly higher glucose and insulin mean incremental areas under the curve (IAUC, P = 0.027 and P = 0.001 respectively). CCK concentration was 59% higher during the first seven hours of the low-GI diet (394 +/- 95 pmol/l min) versus the high-GI diet (163 +/- 38 pmol/l min, P = 0.046), but there was no difference over 10 hours (P = 0.224). GHR concentration was inversely correlated with insulin concentration (Pearson correlation -0.48, P = 0.007) but did not differ significantly between the low- and high-GI diets. Mixed meals of lower GI are associated with lower day-long concentrations of glucose and insulin, and higher CCK after breakfast, morning tea and lunch. This metabolic profile could mediate differences in satiety and hunger seen in some, but not all, studies," wrote R.C. Reynolds and colleagues, University of Sydney.

Reynolds and colleagues published their study in European Journal of Clinical Nutrition ("Effect of the Glycemic Index of Carbohydrates on Day-long Profiles of Plasma Glucose, Insulin, Cholecystokinin and Ghrelin." European Journal of Clinical Nutrition, 2009;63(7):872-878).

For more information, contact R.C. Reynolds, University of Sydney, School Molecular & Microbial Bioscience G08, Human Nutrition Unit, Sydney, NSW 2006, Australia.

From the August 17, 2009, Prepared Foods E-dition