Glycaemic and insulin index of four common German breads.

BACKGROUND/OBJECTIVES: German-style breads are recommended as a lower glycaemic index (GI) alternative, yet little data is available. Our aim was to test the GI and insulin index (II) of four breads and rolls commonly consumed in Germany. SUBJECTS/METHODS: Four German bread products were tested for their GI and II in 12 healthy subjects according to the International Standard Organization guidelines. RESULTS: Only the wholemeal rye bread with visible intact grains and sunflower seeds was identified as low GI (GI=55). Both the wholemeal spelt wheat (GI=63) and the rye wheat sourdough bread (GI=62) were classified as medium GI, whereas soft pretzel was high GI (GI=80, P<0.05 compared with other products). The II of soft pretzels (II=102) was also highest and differed significantly from wholemeal rye (II=70) and rye sourdough bread (II=72) but not from wholemeal spelt wheat (II=77). CONCLUSIONS: Contrary to popular belief, these German-style breads are medium to high GI, with the exception of the rye bread with intact grains and seeds. The results highlight the need to test, rather than 'guestimate', the GI of local products, and develop a broader range of low-GI breads.

Effects of human milk and formula on postprandial glycaemia and insulinaemia.

BACKGROUND/OBJECTIVES: Consumption of formula in place of human milk may produce differences in postprandial glycaemia and insulinaemia that contribute to metabolic programming in the first year of life. The objective of the current study was to determine glycaemic and insulinaemic responses to human milk compared with a typical commercial formula, and then compare 11 other formulas. SUBJECTS/METHODS: On separate mornings in random order, 10 healthy breastfeeding mothers consumed 25 g available carbohydrate portions of their own milk, a formula and reference food (25 g glucose on two occasions). In the second study, 10 different healthy subjects consumed 25 g available carbohydrate portions of 11 different commercial formulas and three reference foods (25 g glucose on three occasions). Fingerpick blood samples were taken at regular intervals over 2 h, and the glycaemic index (GI) and insulin index determined according to a standardised protocol. RESULTS: There were no significant differences in postprandial glycaemia or insulinaemia after human milk vs a typical formula (P = 0.3). Both produced a low GI (mean ± s.e.m.: 38 ± 7 vs 34 ± 7, respectively) and high insulin index (87 ± 14 vs 94 ± 16). The GI and insulin indices of the other formulas ranged from 18 ± 3 to 67 ± 6 and 53 ± 9 to 209 ± 33, respectively. CONCLUSIONS: Human milk and a typical formula elicit similar postprandial glycaemic and insulinaemic responses, but there is a wide range of responses to other formulas.

Effects of PGX, a novel functional fibre, on acute and delayed postprandial glycaemia.

BACKGROUND: Viscous fibre in food has established health benefits, but few functional fibre preparations are both effective and palatable. Our objective was to determine the most effective dose, formulation and timing of consumption of a novel fibre supplement (PolyGlycopleX (PGX)) in reducing postprandial glycaemia. SUBJECTS/METHODS: Three trials were undertaken, each with 10 subjects (8M and 8F; age 24.4 ± 2.6 years). Granular supplement was tested at four doses (0, 2.5, 5.0 and 7.5 g) with breakfast (study 1). Granular and capsule forms of the supplement were given in a single dose (5 g for granules and 4.5 g in capsules) at -60, -45, -30, -15 and 0 before, and +15 min after a bread meal (study 2). Capsules at increasing doses (1.5, 3, 4.5 and 6 g) were consumed with the evening meal to determine effects on glucose tolerance at breakfast (study 3). Incremental area under the blood glucose curve was determined. RESULTS: Granular PGX at breakfast time at doses of 2.5, 5 and 7.5 g reduced the incremental area under the curve by up to 50% in a linear dose-response fashion (P<0.001). The granular form of PGX (5 g), but not the capsules, reduced glycaemia by up to 28% when consumed from -45 to +15 min (P<0.001). Capsules containing 3, 4.5 and 6 g PGX consumed with the evening meal reduced glycaemia at breakfast by up to 28% (P<0.001). CONCLUSIONS: PGX has biologically important, dose-related effects on acute and delayed (second meal) postprandial glycaemia.

Effect of the glycemic index of carbohydrates on day-long (10 h) profiles of plasma glucose, insulin, cholecystokinin and ghrelin.

BACKGROUND: 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. OBJECTIVE: To investigate the effect of a low and a high GI diet on day-long (10 h) blood concentrations of glucose, insulin, cholecystokinin (CCK) and ghrelin (GHR). DESIGN: 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 fibre, and differed only in carbohydrate quality (GI). Blood was sampled every 30-60 min and assayed for glucose, insulin, CCK and GHR. RESULTS: 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 7 h of the low GI diet (394+/-95 pmol/l min) vs the high GI diet (163+/-38 pmol/l min, P=0.046), but there was no difference over 10 h (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. CONCLUSIONS: 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.