Glucose and insulin responses to porridge and gruel meals intended for infants.

OBJECTIVE: The objective was to determine the glycaemic index (GI) and insulinaemic index (II) of some common products intended for infants; that is, three commercial porridges and one gruel. Also, the influence of added fruit components to porridge on postprandial metabolic responses was studied by comparing corresponding data with a matched model product without fruit. DESIGN: The volunteers were served the test products in random order following an overnight fast. A white bread was included as a reference product. Capillary blood samples were collected before and during 3 h after the meals. SETTING: The study was performed at the Department of Applied Nutrition and Food Chemistry, Lund University, Sweden. SUBJECTS: A total of 10 healthy volunteers, six men and four women, aged 24-41 y, with normal body mass indices, were recruited. RESULTS: The GIs (67-75) of the commercial porridges and gruel were significantly lower than for the white bread reference (P < 0.05). In contrast, the GI (79) of the model product (porridge without fruit) could not be distinguished from the reference. The IIs (112-149) for the commercial products and model products, respectively, were not significantly different from the reference. CONCLUSIONS: : The commercial porridges and gruel gave unexpectedly low GIs. In contrast, high IIs were noted. The inconsistency between GI and II could probably be explained by the insulinotrophic effect of the milk component in the products. The fruit and fruit juice added to some of the products had only minor effect on postprandial glycaemia. SPONSORSHIP: The Swedish Council for Forestry and Agricultural Research.

Resistant starch content in a selection of starchy foods on the Swedish market.

OBJECTIVE: The objective was to determine the resistant starch (RS) content in a selection of typical starchy foods on the Swedish market. In addition, the daily RS intake was estimated from Swedish food consumption data. DESIGN: The major forms of RS, including physically encapsulated starch, were determined with an in vitro method using chewing as a pre-step before enzymatic incubation. SETTING: The study was performed at the Department of Applied Nutrition and Food Chemistry, Lund University, Sweden. SUBJECTS: Six healthy subjects were used to chew the food products before enzymatic incubation of the samples. RESULTS: Twenty-five cereal, potato and legume products were included in the study. The highest RS concentration was noted in the legume group (9.5-11.1% total starch basis). Commercially processed potato products were found to have a higher RS content (4.8-5.9%), compared with boiled potatoes (2.0%). Among the cereal products, bread with enclosure of intact rye grains, barley flakes and semolina porridge, respectively, were identified to have a RS level in the higher range (4.5-6.0%). The daily RS intake was estimated to be 3.2 g. CONCLUSIONS: The main RS sources in the Swedish diet are bread and potato products, which contribute approximately 1.3 and 1.2 g RS per day, respectively. Based on food habits the RS intake may vary considerably, thus when added to dietary fibre intake, the contribution of RS may be of nutritional importance for certain individuals.

Milk as a supplement to mixed meals may elevate postprandial insulinaemia.

OBJECTIVE: The objective was to evaluate the impact of milk added to a high-glycaemic index (GI) white bread meal vs a low-GI spaghetti meal, respectively, on postprandial glucose and insulin responses in healthy subjects. DESIGN: The volunteers were served the bread or spaghetti meals with either milk (200 or 400 ml, respectively) or water (400 ml) following an overnight fast. Capillary blood samples were collected before and during 3 h after the meals. SETTING: The study was performed at the Department of Applied Nutrition and Food Chemistry, Lund University, Sweden. SUBJECTS: Ten healthy volunteers, seven men and three women, aged 22-30 y, with normal body mass indices, were recruited. RESULTS: There was no difference in postprandial glucose area under curve (AUC) with and without added milk in the case of the high-GI bread meals. As could be expected, glucose AUC after the bread meal+water was higher than after the spaghetti meal+water. Milk added at 200 or 400 ml to the spaghetti meal did not affect glucose AUC. However, a significantly higher insulin AUC was seen with the bread meal with 400 ml milk (+65%) and the spaghetti meal with 200 ml or 400 ml milk (+300%), respectively, compared with corresponding test meal with water CONCLUSIONS: The addition of milk to a low-GI spaghetti meal may significantly increase the postprandial insulinaemia. Even an ordinary amount of milk (200 ml) increased the insulin AUC to a low-GI spaghetti meal to the same level as seen with white bread. The mechanism for the insulinotrophic effect of milk is not known, and the potential long-term metabolic consequences need to be elucidated. SPONSORSHIP: Swedish Dairy Association.

Inconsistency between glycemic and insulinemic responses to regular and fermented milk products.

BACKGROUND: Foods with a low glycemic index are increasingly being acknowledged as beneficial in relation to the insulin resistance syndrome. Certain organic acids can lower the glycemic index of bread products. However, the possible effect of acids in fermented milk products on the glycemic index and on insulinemic characteristics has not been addressed. The metabolic effects of fermented milk or pickled products used as additives to mixed meals have also not been addressed. OBJECTIVES: One objective was to characterize the glycemic and insulinemic responses after intake of regular or fermented milk products (study 1). In addition, the acute metabolic effect of fermented milk (yogurt) and pickled cucumber as supplements to a traditional breakfast based on a high-glycemic index bread was evaluated (study 2). DESIGN: Ten healthy volunteers were served different breakfast meals after an overnight fast. Capillary blood samples were collected before and during 2 (study 1) or 3 (study 2) h after the meal. White-wheat bread was used as a reference meal in both studies. RESULTS: The lactic acid in the fermented milk products did not lower the glycemic and insulinemic indexes. Despite low glycemic indexes of 15-30, all of the milk products produced high insulinemic indexes of 90-98, which were not significantly different from the insulinemic index of the reference bread. Addition of fermented milk (yogurt) and pickled cucumber to a breakfast with a high-glycemic index bread significantly lowered postprandial glycemia and insulinemia compared with the reference meal. In contrast, addition of regular milk and fresh cucumber had no favorable effect on the metabolic responses. CONCLUSIONS: Milk products appear insulinotropic as judged from 3-fold to 6-fold higher insulinemic indexes than expected from the corresponding glycemic indexes. The presence of organic acids may counteract the insulinotropic effect of milk in mixed meals.

Nutritional properties of starch in buckwheat products: studies in vitro and in vivo.

The nutritional characteristics of buckwheat starch were studied to identify the possibility for reduced postmeal metabolic responses to various buckwheat products. The in vitro rate of starch hydrolysis and resistant starch (RS) formation in boiled buckwheat groats and in a series of breads, baked with 30-70% of buckwheat flour (BWF) or groats (BWG), respectively, were evaluated in vitro. In parallel, postprandial glucose and insulin responses and also the satiety score to BWG and wheat bread with 50% BWG as compared with the reference white wheat bread (WWB) were studied in healthy humans. The highest concentration of RS was found in boiled BWG (6% total starch basis). The RS level in bread products based on different proportions of BWF or BWG (30-70%) varied from 0.9 to 4.4%. The rate of in vitro amylolysis was significantly lower (P < 0.05) in all buckwheat products in comparison with the reference WWB. The calculated hydrolysis indices (HI) were lowest in boiled BWG (HI = 50) and in bread with 70% BWG (HI = 54). Consumption of boiled BWG or bread based on wheat flour and 50% BWG induced significantly lower postprandial blood glucose and insulin responses compared with the WWB. The calculated glycemic and insulinemic indices (GI and II) for boiled BWG were 61 and 53 and for the buckwheat bread, 66 and 74, respectively. The highest satiety score was found with boiled BWG. It is concluded that buckwheat has potential use in the design of foods with lower GI properties.

Effect of spelt wheat flour and kernel on bread composition and nutritional characteristics.

Spelt wheat seeds (Triticum aestivum subsp. spelta cv. Ostro) were used to obtain white spelt flour (64.5% yield), wholemeal spelt flour (100% yield), and scalded spelt wheat kernels. From these materials, white spelt wheat bread (WSB), wholemeal spelt wheat bread (WMSB), and spelt wheat bread with scalded spelt wheat kernels (SSKB) were made and were compared to the reference white wheat bread (WWB). The spelt wheat flours and breads contained more proteins in comparison to wheat flour and bread. Among the samples the highest rate of starch hydrolysis was noticed in WSB. During the first 30 min of incubation this particular bread was shown to have significantly more (P < 0.05) rapidly digestible starch than the WMSB and later on also more starch than in WWB and SSKB, respectively. The WMSB had the lowest hydrolysis index (HI = 95.7). However, the result did not differ significantly from that in the reference common wheat bread. On the other hand, the most refined spelt wheat flour resulted in a bread product (WSB) that was statistically withdrawn (P < 0.05) as one with the highest HI (112.6).