Yvonne Granfeldt

Food properties affecting the digestion and absorption of carbohydrates

Carbohydrate foods differ considerably in their effects on postprandial glucose and insulin responses. Qualitative differences among starchy foods are particularly intriguing because of the dominance of starch in human diets. This paper focuses on food properties in cereal (eg, pasta, bread, Arepas, and porridge) and legume products (eg, red kidney beans and lentils) that affect metabolic responses to starch. Studies in healthy subjects have found that postprandial blood glucose and insulin responses are greatly affected by food structure. Any process that disrupts the physical or botanical structure of food ingredients will increase the plasma glucose and insulin responses. The glycemic responses to bread products were reduced by the use of ingredients with an intact botanical or physical structure or a high amylose content or by enrichment with viscous dietary fiber. However, the important of a moderate increase in the amylose-amylopectin ratio and the naturally occurring levels of viscous cereal fiber is less clear. The rate of starch digestion in vitro was shown to be a key determinant of metabolic responses to most products. Assuming the sample preparation mimics chewing, in vitro enzymic procedures can be used to facilitate ranking. One such procedure, based on chewed rather than artificially disintegrated products, was recently developed and correlates well with glycemic and insulinemic indices for several starchy foods.

Determination of the glycaemic index of foods: interlaboratory study.

Objective: Practical use of the glycaemic index (GI), as recommended by the FAO/WHO, requires an evaluation of the recommended method. Our purpose was to determine the magnitude and sources of variation of the GI values obtained by experienced investigators in different international centres.Design: GI values of four centrally provided foods (instant potato, rice, spaghetti and barley) and locally obtained white bread were determined in 8–12 subjects in each of seven centres using the method recommended by FAO/WHO. Data analysis was performed centrally.Setting: University departments of nutrition.Subjects: Healthy subjects (28 male, 40 female) were studied.Results: The GI values of the five foods did not vary significantly in different centres nor was there a significant centre×food interaction. Within-subject variation from two centres using venous blood was twice that from five centres using capillary blood. The s.d. of centre mean GI values was reduced from 10.6 (range 6.8–12.8) to 9.0 (range 4.8–12.6) by excluding venous blood data. GI values were not significantly related to differences in method of glucose measurement or subject characteristics (age, sex, BMI, ethnicity or absolute glycaemic response). GI values for locally obtained bread were no more variable than those for centrally provided foods.Conclusions: The GI values of foods are more precisely determined using capillary than venous blood sampling, with mean between-laboratory s.d. of approximately 9.0. Finding ways to reduce within-subject variation of glycaemic responses may be the most effective strategy to improve the precision of measurement of GI values.

Vinegar supplementation lowers glucose and insulin responses and increases satiety after a bread meal in healthy subjects

Objective:To investigate the potential of acetic acid supplementation as a means of lowering the glycaemic index (GI) of a bread meal, and to evaluate the possible dose–response effect on postprandial glycaemia, insulinaemia and satiety.Subjects and setting:In all, 12 healthy volunteers participated and the tests were performed at Applied Nutrition and Food Chemistry, Lund University, Sweden.Intervention:Three levels of vinegar (18, 23 and 28 mmol acetic acid) were served with a portion of white wheat bread containing 50 g available carbohydrates as breakfast in randomized order after an overnight fast. Bread served without vinegar was used as a reference meal. Blood samples were taken during 120 min for analysis of glucose and insulin. Satiety was measured with a subjective rating scale.Results:A significant dose–response relation was seen at 30 min for blood glucose and serum insulin responses; the higher the acetic acid level, the lower the metabolic responses. Furthermore, the rating of satiety was directly related to the acetic acid level. Compared with the reference meal, the highest level of vinegar significantly lowered the blood glucose response at 30 and 45 min, the insulin response at 15 and 30 min as well as increased the satiety score at 30, 90 and 120 min postprandially. The low and intermediate levels of vinegar also lowered the 30 min glucose and the 15 min insulin responses significantly compared with the reference meal. When GI and II (insulinaemic indices) were calculated using the 90 min incremental area, a significant lowering was found for the highest amount of acetic acid, although the corresponding values calculated at 120 min did not differ from the reference meal.Conclusion:Supplementation of a meal based on white wheat bread with vinegar reduced postprandial responses of blood glucose and insulin, and increased the subjective rating of satiety. There was an inverse dose–response relation between the level of acetic acid and glucose and insulin responses and a linear dose–response relation between acetic acid and satiety rating. The results indicate an interesting potential of fermented and pickled products containing acetic acid.Sponsorships:Dr P Håkanssons foundation and Direktör Albert Påhlssons foundation for research and charity.

Determination of glycaemic index; some methodological aspects related to the analysis of carbohydrate load and characteristics of the previous evening meal

Objectives:To determine the possible differences in glycaemic index (GI) depending on (1) the analytical method used to calculate the ‘available carbohydrate’ load, that is, using carbohydrates by difference (total carbohydrate by difference, minus dietary fibre (DF)) as available carbohydrates vs available starch basis (total starch minus resistant starch (RS)) of a food rich in intrinsic RS and (2) the effect of GI characteristics and/or the content of indigestible carbohydrates (RS and DF) of the evening meal prior to GI testing the following morning.Design:Blood glucose and serum insulin responses were studied after subjects consuming (1) two levels of barley kernels rich in intrinsic RS (15.2%, total starch basis) and (2) after a standard breakfast following three different evening meals varying in GI and/or indigestible carbohydrates: pasta, barley kernels and white wheat bread, respectively.Subjects:Healthy adults with normal body mass index.Results:(1) Increasing the portion size of barley kernels from 79.6 g (50 g ‘available carbohydrates’) to 93.9 g (50 g available starch) to adjust for its RS content did not significantly affect the GI or insulin index (II). (2) The low GI barley evening meal, as opposed to white wheat bread and pasta evening meals, reduced the postprandial glycaemic and insulinaemic (23 and 29%, respectively, P<0.05) areas under the curve at a standardized white bread breakfast fed the following morning.Conclusion:(1) Increasing portion size to compensate for the considerable portion of RS in a low GI barley product had no significant impact on GI or II. However, for GI testing, it is recommended to base carbohydrate load on specific analyses of the available carbohydrate content. (2) A low GI barley evening meal containing high levels of indigestible carbohydrates (RS and DF) substantially reduced the GI and II of white wheat bread determined at a subsequent breakfast meal.

Effects of GI and content of indigestible carbohydrates of cereal-based evening meals on glucose tolerance at a subsequent standardised breakfast

Objective:To evaluate the impact of four low-glycaemic index (GI) and one high-GI cereal-based evening meals on glucose tolerance at a subsequent standardised breakfast.Design:Wheat kernels, barley kernels, spaghetti, spaghetti with added wheat bran and white wheat bread (WWB) were consumed in the evening in a random order at five different occasions. At the subsequent breakfast, blood glucose, serum insulin, plasma short chain fatty acid, plasma free fatty acid (FFA) and breath hydrogen were measured.Setting:The study was performed at Applied Nutrition and Food Chemistry, Lund University, Sweden.Subjects:Fifteen healthy volunteers were recruited. One subject was later excluded owing to abnormal blood glucose values.Results:The blood glucose response (0–120 min) to the standardised breakfast was significantly lower after consuming barley kernels in the evening compared with evening meals with WWB (P=0.019) or spaghetti+wheat bran (P=0.046). There were no significant differences in insulin concentrations at breakfast. Breath hydrogen excretion at breakfast was significantly higher after an evening meal with barley kernels compared with WWB, wheat kernels or spaghetti (P=0.026, 0.026 and 0.015, respectively), and the concentration of plasma propionate at breakfast was significantly higher following an evening meal with barley kernels compared with an evening meal with WWB (P=0.041). In parallel, FFA concentrations were significantly lower after barley kernels compared with WWB (P=0.042) or spaghetti evening meals (P=0.019).Conclusions:The improved glucose tolerance at breakfast, following an evening meal with barley kernels appeared to emanate from suppression of FFA levels, mediated by colonic fermentation of the specific indigestible carbohydrates present in this product, or, to the combination of the low-GI features and colonic fermentation.Sponsorship:European Commission QLK1-2001-00431 (EUROSTARCH).

Muesli with 4g oat beta-glucans lowers glucose and insulin responses after a bread meal in healty subjects

Objective:To evaluate the impact of an extruded muesli product based on β-glucan-rich oat bran on postprandial glycaemia and insulinaemia.Subject/Design:The study is divided in two series. Blood glucose and serum insulin responses were studied after subjects consuming test meals including a serving of muesli with 3 g (series 1) and 4 g (series 2) of β-glucans, respectively. The muesli was a component in a single serving packet with muesli and yoghurt. This was served together with white wheat bread in the morning after an overnight fast. The compositions were standardized to contain 50 g available carbohydrates. As a reference meal a serving packet without β-glucans was included. The study was performed at Applied Nutrition and Food Chemistry, Lund University, Sweden. Nineteen and thirteen healthy volunteers with normal body mass index were recruited for series 1 and 2, respectively.Results:Muesli with 3 g of β-glucans, included in a mixed bread meal, gave no significant differences in glycaemic response compared to a reference meal without muesli and β-glucans. In contrast, muesli with 4 g of β-glucans significantly (P<0.05) lowered the glucose and insulin responses compared to the reference meal.Conclusions:Muesli enriched with 4 g of β-glucans reduces postprandial glucose and insulin levels to a breakfast based on high glycaemic index products. A total of 4 g of β-glucans from oats seems to be a critical level for a significant decrease in glucose and insulin responses in healthy people.

A paleolithic diet is more satiating per calorie than a mediterranean-like diet in individuals with ischemic heart disease.

BackgroundWe found marked improvement of glucose tolerance and lower dietary energy intake in ischemic heart disease (IHD) patients after advice to follow a Paleolithic diet, as compared to a Mediterranean-like diet. We now report findings on subjective ratings of satiety at meals and data on the satiety hormone leptin and the soluble leptin receptor from the same study.MethodsTwenty-nine male IHD patients with impaired glucose tolerance or diabetes type 2, and waist circumference > 94 cm, were randomized to ad libitum consumption of a Paleolithic diet (n = 14) based on lean meat, fish, fruit, vegetables, root vegetables, eggs, and nuts, or a Mediterranean-like diet (n = 15) based on whole grains, low-fat dairy products, vegetables, fruit, fish, and oils and margarines during 12 weeks. In parallel with a four day weighed food record the participants recorded their subjective rating of satiety. Satiety Quotients were calculated, as the intra-meal quotient of change in satiety during meal and consumed energy or weight of food and drink for that specific meal. Leptin and leptin receptor was measured at baseline and after 6 and 12 weeks. Free leptin index was calculated as the ratio leptin/leptin receptor.ResultsThe Paleolithic group were as satiated as the Mediterranean group but consumed less energy per day (5.8 MJ/day vs. 7.6 MJ/day, Paleolithic vs. Mediterranean, p = 0.04). Consequently, the quotients of mean change in satiety during meal and mean consumed energy from food and drink were higher in the Paleolithic group (p = 0.03). Also, there was a strong trend for greater Satiety Quotient for energy in the Paleolithic group (p = 0.057). Leptin decreased by 31% in the Paleolithic group and by 18% in the Mediterranean group with a trend for greater relative decrease of leptin in the Paleolithic group. Relative changes in leptin and changes in weight and waist circumference correlated significantly in the Paleolithic group (p < 0.001) but not in the Mediterranean group. Changes in leptin receptor and free leptin index were not significant.ConclusionsA Paleolithic diet is more satiating per calorie than a Mediterranean-like diet.Trial registrationClinicalTrials.gov NCT00419497

Validation of digital photographs, as a tool in 24-h recall, for the improvement of dietary assessment among rural populations in developing countries

BackgroundImprovement of traditional methods for dietary assessment is necessary, especially in rural areas where it is more difficult to succeed with self-reporting methods. This study presents and validates a method for improving accuracy when measuring food and nutrient intake of individuals in rural areas. It is called the “Food photography 24-h recall method” (FP 24-hR) and is a modified 24-h recall with the addition of a digital food photography record and a photo atlas.MethodsThe study was carried out in a rural area in the tropical region of Bolivia; 45 women participated. Validation of the method was made by comparing it with a reference method, the Weighed Food Record (WFR). During the FP 24-hR, digital photographs were taken by the subjects of all food consumed during a day and a 24-h recall questionnaire was conducted by an interviewer. An estimate of the amount of food consumed was made using a photo atlas and the photographs taken by the subjects. For validation, comparison was made between the calculations, by both methods, of the levels of food, and nutrient, intake.ResultsThe comparison was made in 10 food categories; most of which were somewhat underestimated from −2.3% (cassava) to −6.8% (rice), except for beverages (+1.6%) and leafy vegetables (+8.7%), which were overestimated. Spearman’s correlation coefficients were highly significant (r from 0.75 for eggs to 0.98 for potato and cassava). Nutrient intakes calculated with data from both methods showed small differences from -0.90% (vitamin C) to -5.98% (fat). Although all nutrients were somewhat underestimated, Pearson′s coefficients are high (>0.93 for all) and statistically significant. Bland Altman analysis showed that differences between both methods were random and did not exhibit any systematic bias over levels of food and nutrient intake, with acceptable 95% limits of agreement.ConclusionThe FP 24-hR exhibits acceptable differences when compared with a WFR, digital photos are useful as a memory aid for the subjects during 24-h recall and as an estimation tool. The method is suitable for assessing dietary intake among rural populations in developing countries.

A bilberry drink with fermented oatmeal decreases postprandial insulin demand in young healthy adults

Backgroundin traditional medicine, blueberries have been used to facilitate blood glucose regulation in type 2 diabetes. Recent studies in diabetic mice have indicated facilitated glycaemic regulation following dietary supplementation with extracts from European blueberries, also called bilberries, (Vaccinium myrtillus). The purpose of the present study was to investigate the impact of fermented oat meal drinks containing bilberries or rosehip (Rosa canina) on glycaemic and insulinaemic responses.Methodsglycaemic and insulinaemic responses in young healthy adults were measured in two series. In series 1, two drinks based on oat meal (5%), fermented using Lactobacillus plantarum 299v, and added with fruit (10%); bilberries (BFOMD) or rose hip (RFOMD) respectively, were studied. In series 2, BFOMD was repeated, additionally, a drink enriched with bilberries (47%) was tested (BBFOMD). As control a fermented oat meal drink (FOMD) was served.Resultsin series 1 the bilberry- and rosehip drinks, gave high glucose responses similar to that after the reference bread. However, the insulin index (II) after the BFOMD was significantly lower (II = 65) (P < 0.05). In series 2 a favourably low insulin demand to BFOMD was confirmed. FOMD gave high glucose response (GI = 95) but, significantly lower insulin response (II = 76). BBFOMD gave remarkably low insulin response II = 49, and tended to lower glycaemia (GI = 79) (P = 0.0684).Conclusiona fermented oat meal drink added with bilberries induced a lower insulin response than expected from the glycaemic response. The mechanism for the lowered acute insulin demand is still unclear, but may be related to some bio-active component present in the bilberries, or to the fermented oat meal base.

Subjective satiety and other experiences of a Paleolithic diet compared to a diabetes diet in patients with type 2 diabetes.

BackgroundWe found marked improvement of glycemic control and several cardiovascular risk factors in patients with type 2 diabetes given advice to follow a Paleolithic diet, as compared to a diabetes diet. We now report findings on subjective ratings of satiety at meal times and participants’ other experiences of the two diets from the same study.MethodsIn a randomized cross-over study, 13 patients with type 2 diabetes (3 women and 10 men), were instructed to eat a Paleolithic diet based on lean meat, fish, fruits, vegetables, root vegetables, eggs and nuts, and a diabetes diet designed in accordance with dietary guidelines, during two consecutive 3-month periods. In parallel with a four-day weighed food record, the participants recorded their subjective rating of satiety. Satiety quotients were calculated as the intra-meal quotient of change in satiety during a meal and consumed energy or weight of food and drink for that specific meal. All participants answered the same three open-ended questions in a survey following each diet: “What thoughts do you have about this diet?”, “Describe your positive and negative experiences with this diet” and “How do you think this diet has affected your health?”.ResultsThe participants were equally satiated on both diets. The Paleolithic diet resulted in greater satiety quotients for energy per meal (p = 0.004), energy density per meal (p = 0.01) and glycemic load per meal (p = 0.02). The distribution of positive and negative comments from the survey did not differ between the two diets, and the comments were mostly positive. Among comments relating to recurring topics, there was no difference in distribution between the two diets for comments relating to tastelessness, but there was a trend towards more comments on the Paleolithic diet being satiating and improving blood sugar values, and significantly more comments on weight loss and difficulty adhering to the Paleolithic diet.ConclusionsA Paleolithic diet is more satiating per calorie than a diabetes diet in patients with type 2 diabetes. The Paleolithic diet was seen as instrumental in weight loss, albeit it was difficult to adhere to.Trial registrationClinicalTrials.gov: NCT00435240