Glycaemic index of 102 complex carbohydrate foods in patients with diabetes

Glycemic index, glycemic load, and cancer risk: a meta-analysis

BACKGROUND

Factors linked to glucose metabolism play an important role in the development of cancers, and both glycemic index (GI) and glycemic load (GL) have been investigated as potential etiologic factors.

OBJECTIVE

A meta-analysis was performed to explore the association between GI and GL and cancer risk from published studies.

DESIGN

A comprehensive, systematic bibliographic search of the medical literature was conducted to identify relevant studies. Case-control and cohort studies published before October 2007 that reported cancer risk estimates for GI and GL were included. Pooled relative risks (RRs) were estimated for breast, colorectal, endometrial, and pancreatic cancer.

RESULTS

Thirty-nine studies were included in the meta-analysis. The interquantile ranges of GL were significantly wider in case-control studies, most of which were conducted in European countries, than in cohort studies. Cohort studies that presented lower ranges of GL also reported lower risk estimates. Overall, both GL and GI were significantly associated with a greater risk of colorectal (summary RR = 1.26; 95% CI: 1.11, 1.44 and RR = 1.18; 95% CI: 1.05, 1.34, respectively) and endometrial (RR = 1.36; 95% CI: 1.14, 1.62 and RR = 1.22; 95% CI: 1.01, 1.49) cancer than of breast and pancreatic cancer. There was, however, a significant between-study heterogeneity for colorectal cancer (P < 0.0001). The association between GL and breast cancer disappeared when publication bias was taken into account. No association was found for pancreatic cancer.

CONCLUSION

This comprehensive meta-analysis of GI and GL and cancer risk suggested an overall direct association with colorectal and endometrial cancer.

Glycemic impact, glycemic glucose equivalents, glycemic index, and glycemic load: definitions, distinctions, and implications

Glycemic impact, defined as "the weight of glucose that would induce a glycemic response equivalent to that induced by a given amount of food" (American Association of Cereal Chemists Glycemic Carbohydrate Definition Committee, 2007), expresses relative glycemic potential in grams of glycemic glucose equivalents (GGEs) per specified amount of food. Therefore, GGE behaves as a food component, and (relative) glycemic impact (RGI) is the GGE intake responsible for a glycemic response. RGI differs from glycemic index (GI) because it refers to food and depends on food intake, whereas GI refers to carbohydrate and is a unitless index value unresponsive to food intake. Glycemic load (GL) is the theoretical cumulative exposure to glycemia over a period of time and is derived from GI as GI x carbohydrate intake. Contracted to a single intake of food, GL approximates RGI but cannot be accurately expressed in terms of glucose equivalents, because GI is measured by using equal carbohydrate intakes with usually unequal responses. RGI, on the other hand, is based on relative food and reference quantities required to give equal glycemic responses and so is accurately expressed as GGE. The properties of GGE allow it to be used as a virtual food component in food labeling and in food-composition databases linked to nutrition management systems to represent the glycemic impact of foods alongside nutrient intakes. GGE can also indicate carbohydrate quality when used to compare foods in equal carbohydrate food groupings.

The Canadian Trial of Carbohydrates in Diabetes (CCD), a 1-y controlled trial of low-glycemic-index dietary carbohydrate in type 2 diabetes: no effect on glycated hemoglobin but reduction in C-reactive protein

BACKGROUND

The optimal source and amount of dietary carbohydrate for managing type 2 diabetes (T2DM) are unknown.

OBJECTIVE

We aimed to compare the effects of altering the glycemic index or the amount of carbohydrate on glycated hemoglobin (HbA1c), plasma glucose, lipids, and C-reactive protein (CRP) in T2DM patients.

DESIGN

Subjects with T2DM managed by diet alone (n=162) were randomly assigned to receive high-carbohydrate, high-glycemic-index (high-GI), high-carbohydrate, low-glycemic-index (low-GI), or low-carbohydrate, high-monounsaturated-fat (low-CHO) diets for 1 y.

RESULTS

The high-GI, low-GI, and low-CHO diets contained, respectively, 47%, 52%, and 39% of energy as carbohydrate and 31%, 27%, and 40% of energy as fat; they had GIs of 63, 55, and 59, respectively. Body weight and HbA1c did not differ significantly between diets. Fasting glucose was higher (P=0.041), but 2-h postload glucose was lower (P=0.010) after 12 mo of the low-GI diet. With the low-GI diet, overall mean triacylglycerol was 12% higher and HDL cholesterol 4% lower than with the low-CHO diet (P<0.05), but the difference in the ratio of total to HDL cholesterol disappeared by 6 mo (time x diet interaction, P=0.044). Overall mean CRP with the low-GI diet, 1.95 mg/L, was 30% less than that with the high-GI diet, 2.75 mg/L (P=0.0078); the concentration with the low-CHO diet, 2.35 mg/L, was intermediate.

CONCLUSIONS

In subjects with T2DM managed by diet alone with optimal glycemic control, long-term HbA1c was not affected by altering the GI or the amount of dietary carbohydrate. Differences in total:HDL cholesterol among diets had disappeared by 6 mo. However, because of sustained reductions in postprandial glucose and CRP, a low-GI diet may be preferred for the dietary management of T2DM.

Glycaemic index and glycaemic load values of cereal products and weight-management meals available in the UK

There is currently an increased global interest in the published glycaemic index (GI) values of foods. The aim of the present work was to supplement a previous study on the glycaemic response of 140 foods available in the UK by studying a further forty-four foods. One hundred and twenty-two healthy subjects, with a mean age of 32·4 (sd 11·4) years and a mean BMI of 23·6 (sd 3·6) kg/m2, were recruited to the study. Subjects were served equivalent available carbohydrate amounts (50 or 30 g) of test foods (cereal products and weight-management meals) and a standard food (glucose) on separate occasions. Capillary blood glucose was measured from finger-prick samples in fasted subjects (0 min) and at 15, 30, 45, 60, 90 and 120 min after starting to eat each test food. For each test food, the GI value was determined, and the glycaemic load was calculated as the product of the GI and the amount of available carbohydrate in a reference serving size. The GI values of the foods tested ranged from 23 to 83. Of the forty-four foods tested, thirty-three were classified as low-GI, eight as medium-GI and three as high-GI foods. Most GI values of the foods tested compared well with previously published values for similar foods. In summary, this study provides reliable GI and glycaemic load values for a range of foods, further advancing our understanding of the glycaemic response of different foods. The data reported here make an important addition to published GI values.

Interindividual variability and intra-individual reproducibility of glycemic index values for commercial white bread

OBJECTIVE

We sought to assess the intra- and interindividual variability of glycemic index value determinations for white bread using glucose as the reference food.

RESEARCH DESIGN AND METHODS

A total of 23 healthy adults (aged 20-70 years) completed up to three sets of two visits per set. Each pair of visits assessed the glycemic response to 50 g available carbohydrates from commercial white bread and glucose, administered in random order. Glycemic index values were calculated by dividing the 2-h incremental area under the serum glucose response curve after each commercial white bread challenge by the mean area under the curve (AUC) for glucose.

RESULTS

The mean +/- SE ratio of the AUC after white bread intake by the AUC after glucose intake for the first set of determinations was 78 +/- 15 (n = 23; coefficient of variation [CV] 94%). When using glycemic index values calculated with the subset of participants who completed three sets of tests (n = 14), glycemic index values for each of the three sets of determinations were 78 +/- 10, 60 +/- 5, and 75 +/- 10, respectively. CVs were 50, 28, and 50%, respectively. The mean glycemic index value of these three sets was 71 +/- 6, with a CV of 30%. When an ANOVA approach was applied to these data, the interindividual CV was 17.8%, and the intra-individual variation was 42.8%.

CONCLUSIONS

These data suggest that in response to a challenge of white bread relative to glucose, within-individual variability is a greater contributor to overall variability than among-individual variability. Further understanding of all the sources of variability would be helpful in better defining the utility of glycemic index values.

Glycaemic index of selected staples commonly eaten in the Caribbean and the effects of boiling v. crushing

Integrating information about the glycaemic index (GI) of foods into the Caribbean diet is limited by the lack of data. Therefore, we determined the GI of eight staple foods eaten in the Caribbean and the effect on GI of crushing selected tubers. Groups of eight to ten healthy volunteers participated in three studies at two sites. GI was determined using a standard method with white bread and adjusted relative to glucose. The mean area under the glucose response curve elicited by white bread was similar for the different groups of subjects. In study 1, the GI of cassava (Manihot esculenta; 94 (SEM 11)) was significantly higher than those of breadfruit (Artocarpus altilis; 60 (SEM 9)), cooking ‘green’ banana (Musa spp.; 65 (SEM 11)) and sadha roti (65 (SEM 9)) (P=0·018). There was no significant difference in the GI of the foods in study 2: dasheen (Colocasia esculenta var. esculenta; 77 (SEM 10)), eddoes (Colocasia esculenta var. antiquorum; 61 (SEM 10)), Irish potato (Solanum tuberosum; 71 (SEM 8)), tannia (Xanthosoma sagittifolium; 60 (SEM 5)) and white yam (Dioscorea alata; 62 (SEM 6)), and, in study 3, crushing did not significantly affect the GI of dasheen, tannia or Irish potato. However, when the results from studies 2 and 3 were pooled, the GI of dasheen (76 (SEM 7)) was significantly greater than that of tannia (55 (SEM 5); P=0·015) with potato being intermediate (69 (SEM 6)). We conclude that dasheen and cassava are high-GI foods, whereas the other tubers studied and sadha roti are intermediate-GI foods. Given the regular usage of cassava and dasheen in Caribbean diets we speculate that these diets would tend to be high GI, although this could be reduced by foods such as sadha roti and white yam. The range of GI between the staples is sufficiently large that health benefits may be accrued by replacing high-GI staples with intermediate-GI staples in the Caribbean diet.

Glycaemic index and glycaemic load values of commercially available products in the UK

The objective of this paper is to provide glycaemic index (GI) and glycaemic load (GL) values for a variety of foods that are commercially available in the UK and to compare these with previously published values. Fasted subjects were given isoglucidic (50 or 25 g carbohydrate) servings of a glucose reference at least two to three times, and test foods once, on separate occasions. For each test food, tests were repeated in at least eight subjects. Capillary blood glucose was measured via finger-prick samples in fasting subjects (0 min) and at 15, 30, 45, 60, 90 and 120 min after the consumption of each test food. The GI of each test food was calculated geometrically by expressing the incremental area under the blood glucose response curve (IAUC) of each test food as a percentage of each subject's average IAUC for the reference food. GL was calculated as the product of the test food's GI and the amount of available carbohydrate in a reference serving size. The majority of GI values of foods tested in the current study compare well with previously published values. More importantly, our data set provides GI values of several foods previously untested and presents values for foods produced commercially in the UK.

Glycaemic and satiating properties of potato products

OBJECTIVE

To investigate glycaemic and satiating properties of potato products in healthy subjects using energy-equivalent or carbohydrate-equivalent test meals, respectively.

SUBJECTS AND SETTING

Thirteen healthy subjects volunteered for the first study, and 14 for the second. The tests were performed at Applied Nutrition and Food Chemistry, Lund University, Sweden. EXPERIMENTAL DESIGN AND TEST MEALS: All meals were served as breakfast in random order after an overnight fast. Study 1 included four energy-equivalent (1000 kJ) meals of boiled potatoes, french fries, or mashed potatoes; the latter varying in portion size by use of different amounts of water. The available carbohydrate content varied between 32.5 and 50.3 g/portion. Capillary blood samples were collected during 240 min for analysis of glucose, and satiety was measured with a subjective rating scale. Study 2 included four carbohydrate-equivalent meals (50 g available carbohydrates) of french fries, boiled potatoes served with and without addition of oil, and white wheat bread (reference). The energy content varied between 963 and 1534 kJ/portion. Capillary blood samples were collected during 180 min for analysis of glucose, and satiety was measured using a subjective rating scale.

RESULTS

Study 1: boiled potatoes induced higher subjective satiety than french fries when compared on an energy-equivalent basis. The french fries elicited the lowest early glycaemic response and was less satiating in the early postprandial phase (area under the curve (AUC) 0-45 min). No differences were found in glycaemic or satiety response between boiled or mashed potatoes. Study 2: french fries resulted in a significantly lower glycaemic response (glycaemic index (GI)=77) than boiled potatoes either with or without addition of oil (GI=131 and 111, respectively). No differences were found in subjective satiety response between the products served on carbohydrate equivalence.

CONCLUSIONS

Boiled potatoes were more satiating than french fries on an energy-equivalent basis, the effect being most prominent in the early postprandial phase, whereas no difference in satiety could be seen on a carbohydrate-equivalent basis. The lowered GI for french fries, showing a typical prolonged low-GI profile, could not be explained by the fat content per se.

Influence of bread volume on glycaemic response and satiety

The role of carbohydrates in health and disease has received a high profile in recent years, in particular the glycaemic index (GI) as a physiological classification of carbohydrate foods. A common carbohydrate source in the UK is white bread, which is considered to have a high GI value and low satiety value. In the present study, the possibility of favourably altering the GI of white bread by manipulating bread structure (loaf form) was investigated. In a randomised repeated-measures design, ten subjects were tested for glycaemic and satiety responses to four loaves of varying volume, but of consistent macronutrient content. Peak plasma glucose levels and GI values were shown to be significantly reduced by lowering loaf volume (P=0.007, P<0.001 respectively). In addition, a greater satiety index (SI) was seen with decreased loaf volume (P<0.001). In conclusion, the present study demonstrates that reducing the volume of white bread, which is generally considered to be high-GI and low-SI, can favourably alter metabolic and appetite responses. Relatively small differences in the GI of regularly consumed starch foods have been shown to have beneficial effects on health.

US Honeys Varying in Glucose and Fructose Content Elicit Similar Glycemic Indexes

The glycemic index of honey may vary, depending upon its floral variety and fructose-to-glucose ratio. We determined the glycemic index of four US honey varieties in 12 healthy adult men and women with a mean (+/-standard error) age of 24.5+/-1.5 years. The glycemic index of 250-mL solution servings of clover, buckwheat, cotton, and tupelo honeys providing 50 g carbohydrate were assessed relative to triplicate feedings of 50 g carbohydrate as a glucose solution. Fructose-to-glucose ratios were 1.09, 1.12, 1.03, 1.54, for clover, buckwheat, cotton, and tupelo, respectively. Blood was collected after an overnight fast and 15, 30, 45, 60, 90, and 120 minutes after intake. Ten minutes were allowed for food consumption. Areas under the glycemic response curves for each honey were expressed as percent means of each participant's average response to glucose feedings. The means (+/-standard error) of the glycemic index were 69.2+/-8.1, 73.4+/-6.4, 73.6+/-6.6, 74.1+/-8.2 for clover, buckwheat, cotton, and tupelo honeys, respectively. No statistically significant differences between the honeys were apparent, nor was a relationship between glycemic index and the fructose-to-glucose ratio detected, indicating that small differences in fructose-to-glucose ratios do not substantially impact honey glycemic index.

Potato and french fry consumption and risk of type 2 diabetes in women

BACKGROUND

Potatoes, a high glycemic form of carbohydrate, are hypothesized to increase insulin resistance and risk of type 2 diabetes.

OBJECTIVE

The objective was to examine prospectively the relation between potato consumption and the risk of type 2 diabetes.

DESIGN

We conducted a prospective study of 84,555 women in the Nurses' Health Study. At baseline, the women were aged 34-59 y, had no history of chronic disease, and completed a validated food-frequency questionnaire. The participants were followed for 20 y with repeated assessment of diet.

RESULTS

We documented 4496 new cases of type 2 diabetes. Potato and french fry consumption were both positively associated with risk of type 2 diabetes after adjustment for age and dietary and nondietary factors. The multivariate relative risk (RR) in a comparison between the highest and the lowest quintile of potato intake was 1.14 (95% CI: 1.02, 1.26; P for trend = 0.009). The multivariate RR in a comparison between the highest and the lowest quintile of french fry intake was 1.21 (95% CI: 1.09, 1.33; P for trend < 0.0001). The RR of type 2 diabetes was 1.18 (95% CI: 1.03, 1.35) for 1 daily serving of potatoes and 1.16 (95% CI: 1.05, 1.29) for 2 weekly servings of french fries. The RR of type 2 diabetes for substituting 1 serving potatoes/d for 1 serving whole grains/d was 1.30 (95% CI: 1.08, 1.57). The association between potato consumption and risk of type 2 diabetes was more pronounced in obese women.

CONCLUSIONS

Our findings suggest a modest positive association between the consumption of potatoes and the risk of type 2 diabetes in women. This association was more pronounced when potatoes were substituted for whole grains.

Association between dietary factors and plasma adiponectin concentrations in men

BACKGROUND

Adiponectin, an adipocyte-derived peptide, improves insulin sensitivity, has antiinflammatory and antiatherogenic effects, and is associated with a lower risk of ischemic heart disease (IHD) and type 2 diabetes. However, little is known about dietary predictors of plasma adiponectin concentrations in humans.

OBJECTIVE

Our objective was to examine cross-sectionally the association between dietary factors and plasma adiponectin in men.

DESIGN

Our study included 532 male participants of the Health Professionals Follow-Up Study who were selected as control subjects for an investigation of biological predictors of IHD. Diet, lifestyle, and anthropometric data were assessed by questionnaires.

RESULTS

After multivariable adjustment, adiponectin was significantly inversely related to glycemic load (-1.3 mg/L per 1-SD increase; P = 0.02) and tended to be positively associated with total fat intake (0.7 mg/L per 0.5% of energy from fat instead of carbohydrates; P = 0.06). We also found a significant nonlinear association between plasma adiponectin concentrations and alcohol intake (P for quadratic trend = 0.01). Thus, whereas nondrinkers had mean plasma adiponectin concentrations of 16.48 mg/L, those who consumed 0.1-4.9, 5.0-14.9, 15.0-29.9, or >/=30 g alcohol/d had mean concentrations of 16.79 (P = 0.77 compared with nondrinkers), 18.97 (P = 0.02), 19.11 (P = 0.01), and 18.39 (P = 0.10) mg/L, respectively.

CONCLUSIONS

Moderate alcohol intake is associated with higher adiponectin concentrations, whereas a carbohydrate-rich diet with a high glycemic load is associated with lower adiponectin concentrations in men with no history of cardiovascular disease. Although the strength of these associations was modest, our observations highlight the hypothesis that dietary factors may modulate plasma adiponectin concentrations-a potential mediator related to a reduced IHD risk.

Glycemic index of potatoes commonly consumed in North America

OBJECTIVE

To determine the effect of variety and cooking method on glycemic response and glycemic index of common North American potatoes.

DESIGN

Study 1: subjects consumed 200 g Russet or white potatoes that were either (a) precooked, refrigerated, and reheated (precooked) or (b) cooked and consumed immediately (day-cooked). Incremental area under the curve was determined. Study 2: subjects consumed 50 g carbohydrate portions of white bread or potatoes (six different varieties and two different cooking methods). Glycemic index values were calculated. In both studies meals were consumed after a 10- to 12-hour overnight fast and finger-prick capillary-blood glucose was measured before and at intervals for 2 hours after consumption.

SUBJECTS

The study groups were as follows: Study 1 comprised four men and six women, aged 20 to 44 and Study 2 comprised 11 men and one woman, aged 18 to 50.

STATISTICAL ANALYSES

Repeated measures analysis of variance with Newman-Kuels to protect for multiple comparisons (criterion of significance two-tailed P <.05).

RESULTS

Study 1: Precooked Russet potatoes elicited lower area under the curve than day-cooked (P <.05), while precooking had no effect on boiled white potatoes. Study 2: The glycemic index values of potatoes varied significantly, depending on the variety and cooking method used (P =.003) ranging from intermediate (boiled red potatoes consumed cold: 56) to moderately high (roasted California white potatoes: 72; baked US Russet potatoes: 77) to high (instant mashed potatoes: 88; boiled red potatoes: 89).

CONCLUSIONS

The glycemic index of potatoes is influenced by variety and method of cooking and US Russet potatoes have only a moderately high glycemic index. Individuals who wish to minimize dietary glycemic index can be advised to precook potatoes and consume them cold or reheated.

Effect of carbohydrate source on post-prandial blood glucose in subjects with type 1 diabetes treated with insulin lispro

Our purpose was to determine if the glycemic index (GI) and proportion of carbohydrate absorbed as glucose (Pg) affected glycemic responses and occurrence of post-prandial hypoglycemia in subjects with type 1 diabetes treated with insulin lispro. Subjects (n=8) were studied on five separate occasions after 10-12 h overnight fasts following a standard dinner. After their morning insulin dose, subjects ate 50 g carbohydrate from a starchy food (Pg=1; mashed potato GI=83, white bread GI=71, spaghetti GI=41, barley GI=25) or pineapple juice (Pg=0.5; GI=46). Blood glucose was measured fasting and at 30 min intervals for 4 h. Glucose responses after different foods differed significantly from 30 to 180 min, with mean incremental area under the curve being closely related to GI (r=0.98, P<0.01). By multiple regression analysis, occurrence of post-prandial hypoglycemia was influenced (P<0.05) by subject and Pg. Time to hypoglycemia was affected by subject, fasting glucose, and GI. Thus, in subjects with type 1 diabetes treated with insulin lispro, GI predicts glycemic responses of carbohydrate foods. Pg may affect the occurrence of post-prandial hypoglycemia, while GI may affect its timing. Further studies using mixed meals are required to confirm how carbohydrate source affects glycemic responses and occurrence of hypoglycemia in normal meal setting.

Different glycemic indexes of breakfast cereals are not due to glucose entry into blood but to glucose removal by tissue

BACKGROUND

The glycemic index (GI) of a food is thought to directly reflect the rate of digestion and entry of glucose into the systemic circulation. The blood glucose concentration, however, represents a balance of both the entry and the removal of glucose into and from the blood, respectively. Such direct quantification of the postprandial glucose curve with respect to interpreting the GI is lacking in the literature.

OBJECTIVE

We compared the plasma glucose kinetics of low- and high-GI breakfast cereals.

DESIGN

On 2 occasions, plasma insulin concentrations and plasma glucose kinetics (by constant-rate infusion of [6,6-(2)H(2)]glucose) were measured in 6 healthy males for 180 min after they fasted overnight and then consumed an amount of corn flakes (CF) or bran cereal (BC) containing 50 g available carbohydrate.

RESULTS

The GI of CF was more than twice that of BC (131.5 +/- 33.0 compared with 54.5 +/- 7.2; P < 0.05), despite no significant differences in the rate of appearance of glucose into the plasma during the 180-min period. Postprandial hyperinsulinemia occurred earlier with BC than with CF, resulting in a 76% higher plasma insulin concentration at 20 min (20.4 +/- 4.5 compared with 11.6 +/- 2.1 micro U/mL; P < 0.05). This was associated with a 31% higher rate of disappearance of glucose with BC than with CF during the 30-60-min period (28.7 +/- 3.1 compared with 21.9 +/- 3.1 micro mol. kg(-)(1). min(-)(1); P < 0.05).

CONCLUSION

The lower GI of BC than of CF was not due to a lower rate of appearance of glucose but instead to an earlier postprandial hyperinsulinemia and an earlier increase in the rate of disappearance of glucose, which attenuated the increase in the plasma glucose concentration.

Glycaemic index of different coconut (Cocos nucifera)-flour products in normal and diabetic subjects

The glycaemic index (GI) of commonly consumed bakery products supplemented with increasing levels of coconut (Cocos nucifera) flour was determined in ten normal and ten diabetic subjects. Using a randomized crossover design, the control and test foods were fed in random order on separate occasions after an overnight fast. Blood samples were collected through finger prick before and after feeding and were analysed for glucose levels using a clinical chemistry analyser. The significantly low-GI (<60) foods investigated were: macaroons (GI 45.7 (sem 3.0)) and carrot cake (GI 51.8 (sem 3.3)), with 200-250 g coconut flour/kg (P<0.05). The test foods with 150 g coconut flour/kg had GI ranging from 61.3 to 71.4. Among the test foods, pan de sal (GI 87.2 (sem 5.5)) and multigrain loaf (GI 85.2 (sem 6.8)) gave significantly higher GI with 50 and 100 g coconut flour/kg respectively (P<0.05). On the other hand, granola bar and cinnamon bread with 50 and 100 g coconut flour/kg respectively gave a GI ranging from 62.7 to 71.6 and did not differ significantly from the test foods with 150 g coconut flour/kg (P<0.05). A very strong negative correlation (r -0.85, n 11, P<0.005) was observed between the GI and dietary fibre content of the test foods supplemented with coconut flour. In conclusion, the GI of coconut flour-supplemented foods decreased with increasing levels of coconut flour and this may be due to its high dietary fibre content. The results of the present study may form a scientific basis for the development of coconut flour as a functional food. However, the fat content of coconut flour-supplemented food should always be considered to optimize the functionality of coconut fibre in the proper control and management of diabetes mellitus.

Glycaemic glucose equivalent: validation as a predictor of the relative glycaemic effect of foods

BACKGROUND

Glycaemic glucose equivalent (GGE) content of a quantity of a food, based on glycaemic index, food composition and food quantity, is the theoretical weight of glucose that would induce a glycaemic response equivalent to that induced by the given amount of food.

OBJECTIVES

To test whether GGE content predicts glycaemic response to foods differing in glycaemic index, carbohydrate content and intake, over a practical range of carbohydrate intakes.

DESIGN

: Controlled randomised study.

SETTING

Clinical trials unit at the Department of Human Nutrition, University of Otago, Dunedin, New Zealand.

SUBJECTS

In all, 12 volunteers with and 12 without type II diabetes were recruited. All but one subject completed the trial.

METHOD

Yams, biscuits, white rice and porridge were consumed at 10 and 20 GGE doses, and 2-minute noodles at 24 and 48 GGE, following an overnight fast. Incremental areas under the blood glucose response curves (IAUC) over 3 h were calculated for each individual for all foods, and individual glycaemic responsiveness was determined as IAUC/GGE.

RESULTS

Within GGE dose, blood glucose responses to all foods, except rice, were similar. Doubling GGE dose approximately doubled glycaemic response. Relative glycaemic effects were accurately predicted by GGE intake after adjusting for individual glycaemic sensitivity (individual average IAUC/GGE). The accuracy of prediction of relative glycaemic effect from GGE intake was affected little by carbohydrate dose.

CONCLUSION

GGE content predicted glycaemic impact of foods over a practical range of carbohydrate intakes, and may therefore be useful for accurate dietary management of glycaemia in diabetes mellitus. The predictive validity of GGE in mixed meals now needs to be tested.

SPONSORSHIP

Health Research Council of New Zealand contract 00/453.

Glycaemic glucose equivalent: combining carbohydrate content, quantity and glycaemic index of foods for precision in glycaemia management

The glycaemic index (GI) is the blood glucose response to carbohydrate in a food as a percentage of the response to an equal weight of glucose. Because GI is a percentage, it is not related quantitatively to food intakes, and because it is based on equi-carbohydrate comparisons, GI-based exchanges for control of glycaemia should be restricted to foods providing equal carbohydrate doses. To overcome these limitations of GI, the glycaemic glucose equivalent (GGE), the weight of glucose having the same glycaemic impact as a given weight of food, is proposed as a practical measure of relative glycaemic impact. To illustrate the differences between GGE and GI in quantitative management of postprandial glycaemia, published values for carbohydrate content, GI and serving size of foods in the food groupings, breads, breakfast cereals, pulses, fruit and vegetables, were used to determine the GGE content per equal weight and per serving of foods. Food rankings and classifications for exchanges based on GGE content were compared with those based on GI. In all of the food groupings analysed, values for relative glycaemic impact (as GGE per 100 g food and per serving) within each of the categories, low, medium and high GI were too scattered for GI to be a reliable indicator of the glycaemic impact of any given food. Correlations between GI and GGE content per serving were highest in food groupings of similar carbohydrate content and serving size, including breads (r = 0.73) and breakfast cereals (r = 0.8), but low in more varied groups including pulses (r = 0.66), fruit (r = 0.48) and vegetables (r = 0.28). Because of the non-correspondence of GI and GGE content, food rankings by GI did not agree with rankings by GGE content, and placement of foods in GI-based food exchange categories was often not appropriate for managing glycaemia. Effects of meal composition and food intake on relative glycaemic impact could be represented by GGE content, but not by GI. Because GGE is not restricted to equicarbohydrate comparisons, and is a function of food quantity, GGE may be applied, irrespective of food or meal composition and weight, and in a number of approaches to the management of glycaemia. Accurate control of postprandial glycaemia should therefore be achievable using GGE because they address the need to combine GI with carbohydrate dose in diets of varying composition and intake, to obtain a realistic indication of relative glycaemic impact.

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 centrexfood 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.

Glycemic index in chronic disease: a review

AIM

The intent of this review is to critically analyze the scientific evidence on the role of the glycemic index in chronic Western disease and to discuss the utility of the glycemic index in the prevention and management of these disease states.

BACKGROUND

The glycemic index ranks foods based on their postprandial blood glucose response. Hyperinsulinemia and insulin resistance, as well as their determinants (eg high energy intake, obesity, lack of physical activity) have been implicated in the etiology of diabetes, coronary heart disease and cancer. Recently, among dietary factors, carbohydrates have attracted much attention as a significant culprit, however, different types of carbohydrate produce varying glycemic and insulinemic responses. Low glycemic index foods, characterized by slowly absorbed carbohydrates, have been shown in some studies to produce beneficial effects on glucose control, hyperinsulinemia, insulin resistance, blood lipids and satiety.

METHOD

Studies on the short and long-term metabolic effects of diets with different glycemic indices will be presented and discussed. The review will focus primarily on clinical and epidemiological data, and will briefly discuss in vitro and animal studies related to possible mechanisms by which the glycemic index may influence chronic disease.

Dietary glycemic load and atherothrombotic risk

Hyperglycemia and hyperinsulinemia are central features of the metabolic syndrome and type 2 diabetes mellitus, which contribute to the pathogenesis of coronary heart disease (CHD). Recent data indicate that increased dietary glycemic load (GL) due to replacing fats with carbohydrates or increasing intake of rapidly absorbed carbohydrates (ie, high glycemic index) can create a self-perpetuating insulin resistance state and predicts greater CHD risk. In this paper, we discuss the historic development of the GI and GL concepts and summarize metabolic experiments and epidemiologic observations relating to clinical utilities of these measures. On balance, increased consumption of low-GI foods leads to improvements in glycemia and dyslipidemia in metabolic studies, and a low-GL diet has been associated with lower risk of type 2 diabetes and CHD in prospective cohort studies. We conclude that decreasing dietary GL by reducing the intake of high-glycemic beverages and replacing refined grain products and potatoes with minimally processed plant-based foods such as whole grains, fruits, and vegetables may reduce CHD incidence in sedentary individuals and populations with a high prevalence of overweight. Because of advances in food-processing technologies and changes in ingredients in our food supply, the composition and physiologic effects of foods are likely to change over time. Future efforts should continue to quantify and monitor the metabolic impacts of different foods, and such information should be routinely incorporated into long-term prospective studies to allow for the assessment of the interactive effects of diets and other metabolic determinants on chronic disease risk.

Glucose and insulin responses to a new zero-energy fiber source

OBJECTIVE

Consumption of a number of soluble fiber sources reduces glucose and insulin responses in humans. These fibers provide some available energy. Z-trim, a completely insoluble, noncaloric fiber/fat replacer produced from grain, was developed by ARS scientist George Inglett but until this report had not been tested in humans. The objective was to test the effects of consumption of various doses of this new fiber on glucose and insulin responses in humans.

DESIGN

Men and women (12 each) matched for age and body mass index (41 years, BMI 27) were given glucose or glucose with three levels of fiber in a Latin-square design. Blood samples were obtained before and 30, 60, 120 and 180 minutes after solutions containing glucose alone (1 g/kg body weight) and glucose plus 0.08, 0.17 and 0.33 g/kg body weight of Z-trim were consumed. Plasma glucose, insulin and glucagon were determined by enzyme or radioimmunoassays. A repeated-measures analysis of variance was conducted.

RESULTS

Glucose responses were lower for women than for men (p = 0.02) regardless of the test solution. At 30 minutes, glucose levels of men were 0.7-1.1 mmol/L lower after the two higher levels of fiber than after glucose alone. Insulin peak responses were delayed by high amounts of Z-trim. Fasting and response levels of glucagon were higher (p < 0.002) in women than in men. The decline in glucagon usually seen after a glucose load was moderated by the addition of fiber.

CONCLUSION

Although high levels of this new fiber may beneficially affect glucose metabolism of middle-aged people, it is less effective than soluble fiber.

Whole-grain intake and the risk of type 2 diabetes: a prospective study in men

BACKGROUND

Certain dietary components may play a role in the prevention of type 2 diabetes.

OBJECTIVE

We examined prospectively the associations between whole- and refined-grain intake and the risk of type 2 diabetes in a large cohort of men.

DESIGN

Men from the Health Professionals Follow-up Study without a history of diabetes or cardiovascular disease in 1986 (n = 42898) were followed for </=12 y. Intakes of whole and refined grains, measured every 4 y by use of food-frequency questionnaires, were used to predict subsequent type 2 diabetes risk through multivariate analysis.

RESULTS

We ascertained 1197 cases of incident type 2 diabetes. After adjustment for age; physical activity; cigarette smoking; alcohol consumption; family history of diabetes; and fruit, vegetable, and energy intakes, the relative risk of type 2 diabetes was 0.58 (95% CI: 0.47, 0.70; P for trend < 0.0001) comparing the highest with the lowest quintile of whole-grain intake. The association was moderately attenuated when additionally adjusted for body mass index (relative risk: 0.70; 95% CI: 0.57, 0.85; P for trend = 0.0006). Intake of refined grains was not significantly associated with risk of type 2 diabetes. After further adjustment for magnesium intake, cereal fiber intake, and glycemic load, the association between whole grains and type 2 diabetes was attenuated and the trend no longer significant.

CONCLUSIONS

In men, a diet high in whole grains is associated with a reduced risk of type 2 diabetes in men that may be mediated by cereal fiber. Efforts should be made to replace refined-grain with whole-grain foods.

Depression of the glycemic index by high levels of beta-glucan fiber in two functional foods tested in type 2 diabetes

OBJECTIVES

To determine the extent to which beta-glucan reduces the glycemic index (GI) of oat products and whether high levels of beta-glucan impair palatability.

DESIGN

The study design was an open-label, randomized cross-over study with six treatment segments.

SETTING

Free-living outpatients.

SUBJECTS

Sixteen volunteers with type 2 diabetes (10 men, six women, 61+/-2 y, body mass index 29+/-2 kg/m(2), HbA1c 7.4+/-0.4%) were recruited from the St Michael's Hospital diabetes clinic.

INTERVENTIONS

Volunteers were given, in random order, 50 g available carbohydrate portions of: white bread; a commercial oat bran breakfast cereal (4.4 g% beta-glucan); and a prototype beta-glucan-enriched breakfast cereal and bar, both high in beta-glucan (8.1 and 6.5 g% beta-glucan, respectively) and sweetened with fructose. Capillary blood samples were taken fasting and then 30, 60, 90, 120, 150 and 180 min after the start of the meal. Palatability was recorded using two different methods.

RESULTS

The glycemic indices of the prototype beta-glucan cereal (mean+/-s.e.m.; 52+/-5) and beta-glucan bar (43+/-4.1) were significantly lower than the commercial oat bran breakfast cereal (86+/-6) and white bread (100; P<0.05). All foods were highly palatable and not significantly different. It was found that the GI of the test foods used in this study decreased by 4.0+/-0.2 units per gram of beta-glucan compared to our estimate of 3.8+/-0.6 for studies reported in the literature.

CONCLUSION

Addition of beta-glucan predictably reduces the GI while maintaining palatability. In a 50 g carbohydrate portion each gram of beta-glucan reduces the GI by 4 units, making it a useful functional food component for reducing postprandial glycemia.

SPONSORSHIP

Nestec, Switzerland.

Lower diet glycaemic index in African than South Asian men in Trinidad and Tobago

In Trinidad and Tobago (T&T), diabetes is over two times more common in South Asian (SA) than African (AF) men, with a smaller difference in women. In the USA, high diet glycaemic index (GI) was associated with increased risk of developing diabetes. In T&T, dietary intake data are unavailable. The objective of this study was to conduct a pilot survey of the dietary habits of 50 AF and 50 SA subjects in order to develop a valid nutrition survey instrument for use in T&T. We hypothesized that diet GI would be lower in AF than SA subjects. We collected 24 h dietary recalls from a sample of adults from T&T (26 AF and 33 SA women, and 17 AF and 25 SA men), excluding subjects of mixed or other ethnic backgrounds and those with diabetes or other chronic disorders. AF women were of similar age, but taller and heavier than SA women. There was no significant difference in diet between AF and SA women. AF men were taller than SA men, but of similar age (34 +/- 2 years versus 33 +/- 2 years) and body mass index (24.1 +/- 0.8 kg/m2 versus 23.3 +/- 0.9 kg/m2, respectively). Intakes of energy, fat, protein, carbohydrate and fibre, and diet glycaemic load did not differ significantly, but AF men had a lower diet GI than SA men (56 +/- 1 versus 59 +/- 1, P < 0.05). Although not conclusive, these results are consistent with previous data suggesting that diet GI may contribute to the development of type 2 diabetes. The data collected during this survey will be useful in developing a food frequency questionnaire for use in T&T to allow this hypothesis to be tested more rigorously in this population.

Postprandial glucose, insulin, and incretin responses to grain products in healthy subjects

BACKGROUND

Various botanical and structural characteristics of starchy food modify the postprandial glucose and insulin responses in humans.

OBJECTIVE

We investigated what factors in grain products affect human glucose and insulin responses and elucidated the mediating mechanisms.

DESIGN

Ten men and 10 women [mean age: 28 +/- 1 y; mean body mass index (in kg/m(2)): 22.9 +/- 0.7] with normal glucose tolerance were recruited. The test products were whole-kernel rye bread, whole-meal rye bread containing oat beta-glucan concentrate, dark durum wheat pasta, and wheat bread made from white wheat flour. Paracetamol, a marker of the rate of gastric emptying, was added to the breads during baking. Each product provided 50 g available carbohydrate and was served in random order with breakfast (except for the beta-glucan rye bread, which was served at the last visit). Fasting and 8 postprandial blood samples were collected at intervals of 15-30 min for 3 h to determine plasma glucose, glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide 1 (GLP-1), serum insulin, and paracetamol concentrations. The in vitro starch hydrolysis, the structural characteristics (by light microscopy), and the molecular weight of beta-glucan in the test products were analyzed.

RESULTS

Glucose responses and the rate of gastric emptying after consumption of the 2 rye breads and pasta did not differ from those after consumption of white wheat bread. However, insulin, GIP, and GLP-1 responses, except for GLP-1 responses to the rye bread containing oat beta-glucan concentrate, were lower after the consumption of rye breads and pasta than after consumption of white wheat bread.

CONCLUSIONS

Postprandial insulin responses to grain products are determined by the form of food and botanical structure rather than by the amount of fiber or the type of cereal in the food. These effects may be mediated through GIP and GLP-1.

Dietary carbohydrates, physical inactivity, obesity, and the 'metabolic syndrome' as predictors of coronary heart disease

Several decades of epidemiological and clinical research have identified physical inactivity, excessive calorie consumption, and excess weight as common risk factors for both type 2 diabetes mellitus and coronary heart disease. This trio forms the environmental substrate for a now well-recognized metabolic phenotype called the insulin resistance syndrome. Recent data suggest that a high intake of rapidly absorbed carbohydrates, which is characterized by a high glycemic load (a measure of carbohydrate quality and quantity), may increase the risk of coronary heart disease by aggravating glucose intolerance and dyslipidemia. These data also suggest that individuals who are obese and insulin resistant are particularly prone to the adverse effects of a high dietary glycemic load. In addition, data continue to accumulate suggesting the important beneficial effects of physical activity, even at moderate levels, and weight reduction on improving insulin sensitivity and reducing the risk of coronary heart disease. Future metabolic studies should continue to quantify the physiological impact of different foods on serum glucose and insulin, and such information should routinely be incorporated into large-scale and long-term prospective studies, in which the possible interaction effects between diet and other metabolic determinants such as physical activity and obesity can be examined. Until more definitive data are available, replacing refined grain products and potatoes with minimally processed plant-based foods such as whole grains, fruits, and vegetables, and reducing the intake of high glycemic load beverages may offer a simple strategy for reducing the incidence of coronary heart disease.

Dietary glycemic load assessed by food-frequency questionnaire in relation to plasma high-density-lipoprotein cholesterol and fasting plasma triacylglycerols in postmenopausal women

BACKGROUND

In metabolic studies, both greater carbohydrate intakes and higher glycemic indexes (GIs) raise fasting triacylglycerol concentrations. In epidemiologic studies, dietary glycemic load (GL) is positively associated with risk of coronary artery disease and type 2 diabetes.

OBJECTIVE

We examined both the physiologic relevance of GI and GL and the ability of dietary questionnaires to measure these variables.

DESIGN

In the Nurses' Health Study, we measured plasma triacylglycerol concentrations in fasting blood samples from 185 healthy postmenopausal women and HDL-cholesterol concentrations in an additional 95 nonfasting samples. Dietary carbohydrate, GI, and GL were assessed by use of semiquantitative food-frequency questionnaires. The cross-sectional associations between these 3 variables and plasma triacylglycerol and HDL were assessed, with adjustment for potential confounding factors.

RESULTS

For the lowest and highest quintiles of GL, the multivariate-adjusted geometric mean triacylglycerol concentrations were 0.98 and 1.75 mmol/L (87 and 155 mg/dL; P for trend < 0.001). Both overall GI (P for trend = 0.03) and carbohydrate (P for trend < 0.01) contributed independently to the strong positive association between GL and fasting triacylglycerol concentrations. GL was also inversely associated with HDL-cholesterol concentrations. For the lowest and highest quintiles of GL, the mean HDL-cholesterol concentrations were 1.50 and 1.34 micromol/L (58 and 52 mg/dL; P for trend = 0.03). The relation between GL and fasting triacylglycerol concentrations differed significantly by body mass index (BMI; in kg/m(2)) categories (P < 0.001 for interaction). For the lowest to the highest quintiles of GL, the mean triacylglycerol concentrations were 0.92 and 2.24 mmol/L (81 and 198 mg/dL) in women with BMIs > 25 (P for trend < 0.001) and 1.02 and 1.42 mmol/L (90 and 126 mg/dL) in women with BMIs < or = 25 (P for trend < 0.001).

CONCLUSION

These data support the physiologic relevance of the GL as a potential risk factor for coronary artery disease in free-living women, particularly those prone to insulin resistance. These findings also document the ability of a semiquantitative food-frequency questionnaire to assess dietary GIs and GLs.

Glycemic index in the diet of European outpatients with type 1 diabetes: relations to glycated hemoglobin and serum lipids

BACKGROUND

Little is known about the variation of the glycemic index (GI) in the diet of European outpatients with type 1 diabetes and how the GI of a commonly consumed diet is associated with metabolic control.

OBJECTIVE

The present study examined the calculated dietary GI of European outpatients with type 1 diabetes for possible relations to glycated hemoglobin (Hb A(1c)) and serum lipid concentrations.

DESIGN

The relation of the GI (calculated from a 3-d dietary record) to Hb A(1c), serum cholesterol (total, LDL, and HDL), and fasting triacylglycerol was analyzed in 2810 people with type 1 diabetes from the EURODIAB Complications Study.

RESULTS

The GI was independently related to Hb A(1c) (P = 0.0001). Compared with the highest GI quartile (median GI: 89), adjusted Hb A(1c) in the lowest GI quartile (median GI: 75) was 11% lower in patients from southern European centers and 6% lower in patients from northern, western, and eastern European centers. Of the serum lipids, only the HDL cholesterol in patients from these European centers was independently related to the GI (P = 0.002). In southern European centers, the consumption of pasta, temperate-climate fruit, white bread, and potatoes largely determined the patients' dietary GI, whereas in the northern, western, and eastern European centers, consumption of bread, potatoes, and temperate-climate fruit was most relevant.

CONCLUSIONS

This study in European patients with type 1 diabetes showed that a lower dietary GI is related to lower Hb A(1c) concentrations, independently of fiber intake. The consumption of bread and pasta had the biggest effect on the overall dietary GI of European outpatients.

Characteristics of some wheat-based foods of the Italian diet in relation to their influence on postprandial glucose metabolism in patients with type 2 diabetes

The present study was aimed at evaluating in patients with type 2 diabetes: (1) the glycaemic response to four starchy foods based on wheat, typical of the Italian diet; (2) the importance of some food characteristics in relation to their effects on postprandial glucose response. Seventeen patients with type 2 diabetes (eleven men and six women) participated in the study. All patients consumed, in random order and on alternate days, 50 g available carbohydrate provided by 90 g white bread and, according to a randomised procedure, an equivalent amount of carbohydrate provided by one (n 8) or two (n 9) of three other different test foods (g): pizza 85, potato dumplings 165, hard toasted bread 60. Foods had a similar nutrient composition. Plasma glucose response, measured for 180 min, was significantly lower after the potato dumplings than after white bread at 90 (P < 0.05), 120 (P < 0.01), and 150 (P < 0.05) min. No difference was observed in postprandial plasma insulin response after the various test foods. The percentage of starch hydrolysed after 5 h in vitro hydrolysis with alpha-amylase was about 30 % lower for potato dumplings than for the other foods. However, no differences in the resistant starch content, the rate of diffusion of simple sugars added to a dialysis tube containing the food, and the viscosity of digesta were observed among the test foods. Scanning electron microscopy of potato dumplings showed a compact structure compatible with impaired accessibility of starch to digestive enzymes. In conclusion, carbohydrate-rich foods typical of the Italian diet which are often consumed as an alternative to pasta dishes are not equivalent in terms of metabolic impact in diabetic patients. Due to their low blood glucose response, potato dumplings represent a valid alternative to other starchy foods in the diabetic diet. Food structure plays an important role in determining starch accessibility to digestion, thus influencing the postprandial blood glucose response.

An examination of the possibility of lowering the glycemic index of oat and barley flakes by minimal processing

Differences in glycemic responses to various starchy foods are related to differences in the rate of starch digestion and absorption. In this study, the importance of the degree of gelatinization and the product thickness for postprandial glycemic and insulinemic responses to rolled oats and barley were studied in healthy subjects (5 men and 5 women). Thick (1.0 mm) rolled oats were made from raw or preheated (roasted or steamed) kernels. In addition, thin (0.5 mm) rolled oats were made from roasted or roasted and steamed (processed under conditions simulating commercial production) oat kernels. Finally, steamed rolled barley kernels (0.5 or 1.0 mm) were prepared. All thin flakes elicited high glucose and insulin responses [glycemic index (GI), 88-118; insulinemic index (II), 84-102], not significantly different from white wheat bread (P: > 0.05). In contrast, all varieties of thick oat flakes gave significantly lower metabolic responses (GI, 70-78; II, 58-77) than the reference bread (P: < 0.05). Thick barley flakes, however, gave high glucose and insulin responses (GI, 94; II, 84), probably because the botanical structure underwent more destruction than the corresponding oat flakes. We conclude that minimal processing of oat and barley flakes had a relatively minor effect on GI features compared with the more extensive commercial processing. One exception was thick oat flakes, which in contrast to the corresponding barley flakes, had a low GI.

Mechanisms of the effects of grains on insulin and glucose responses

Consumption of a number of grains and grain extracts has been reported to control or improve glucose tolerance and reduce insulin resistance. The inability of the body to maintain normal glucose levels or to require excessive levels of insulin to do so has been called glucose intolerance, impaired glucose tolerance and insulin resistance. These conditions are associated with obesity and may be preliminary steps in the progression to type 2 diabetes mellitus. Although dietary goals recommend the consumption of three servings of whole grains per day, average consumption in the United States is less than one serving per day. There are a number of mechanisms by which grains may improve glucose metabolism and delay or prevent the progression of impaired glucose tolerance to insulin resistance and diabetes. These mechanisms are related to the physical properties and structure of grains. The composition of the grain, including particle size, amount and type of fiber, viscosity, amylose and amylopectin content all affect the metabolism of carbohydrates from grains. Increasing whole grain intake in the population can result in improved glucose metabolism and delay or reduce the risk of developing type 2 diabetes mellitus. Whole grains can provide a substantial contribution to the improvement of the diets of Americans. A number of whole grain foods and grain fiber sources are beneficial in reduction of insulin resistance and improvement in glucose tolerance. Form, amount and method of cooking of these foods as well as the health characteristics, age and gender of the group of subjects studied are all important factors in the effectiveness of the foods in altering these responses. Dietary recommendations of health organizations suggest consumption of three servings a day of whole grain foods; however, Americans generally fall below this standard. Recent research using various grains and grain products effective in improving insulin resistance or lowering glycemic index will be discussed below by possible mechanisms of action.

Apparent digestibility and glycaemic responses to an experimental induced viscosity dietary fibre incorporated into an enteral formula fed to dogs cannulated in the ileum

The purpose of this study was to evaluate the apparent digestibility and postprandial glycaemic responses of ileal-cannulated dogs when fed an experimental induced viscosity dietary fibre (IVF) incorporated into a liquid enteral formula. Dietary treatments were: (1) control; (2) Glucerna; (3) Glytrol; (4) IVF; and (5) Jevity. Diets varied in concentrations of crude protein (CP), fat, starch and total dietary fibre (TDF). Dry matter and starch intakes by dogs fed the Glucerna and Glytrol treatments were lower (P<0.05) than for those consuming the other diets. However, daily intakes of CP and fat followed a reverse trend. Digestibility of nutrients at the ileum was high (>80%) for all dietary treatments. Mineral absorption proximal to the ileum and from the total tract was not significantly different among treatments. Mean incremental area under the serum glucose response curves for dogs fed Glytrol, Glucerna, and IVF treatments were lower (P<0.05) than the control treatment. Induced viscosity fibre appears to have no negative effects on nutrient digestion throughout the gastrointestinal tract. Its ability to moderate serum glucose concentrations would make it a potentially good choice for a diabetic liquid formula.

Glycaemic index concept and metabolic diseases

Glycaemic response is not just a function of a compound belonging to the class of simple sugars or to the class of starches, or in other words, the size of the molecule. Glycaemic response to carbohydrates depends on several factors, particularly the chemical nature of the glucids, their origin, their mode of preparation, the physical form under which food is consumed, the presence of other nutrients (lipids, proteins) and fiber. Glycaemic and insulinemic indexes can be used to semi-quantitatively classify types of food as a function of their power to raise glucose and insulin levels. A recent mera-analysis of a dozen clinical trials has shown the utility of replacing high glycaemic index carbohydrates with low glycaemic index carbohydrates to improve different metabolic parameters in patient subgroups at risk (DDM, NIDDM, high triglyceride levels, etc.). In addition, this knowledge can eliminate the need to systematically forbid all sugars and sweet foods, and thus in an apparent paradox, to respect both food behavior and enjoyment alongside compliance with dietary advice.

Hypoglycemic effect and protein nutritive quality of soy and methionine-supplemented whole durum pasta products

New low cost, high-protein and high-fiber pasta products processed from whole durum meal (WD) solely, WD supplemented with 7% or 12% defatted soy flour (SF), or 12% SF plus 0.3% methionine were evaluated in comparison with the regular pasta made of pure durum semolina (DS). Their protein nutritive quality was biologically evaluated by rat growth studies using diets containing 9% protein, through the parameters: food efficiency ratio (FER), protein efficiency ratio (PER), net protein utilization (NPU), digestibility coefficient (DC) and biological value (BV). The original products were administered to diabetic hypercholesterolemic albino rats, (injected with alloxane) to study their effects on the levels of blood glucose and plasma lipid fractions. The results indicate that diets based on pasta made of WD supplemented with SE or SF plus methionine had superior protein quality and succeeded in supporting normal growth of rats in contrast to the diets based on pasta made of unsupplemented WD or DS. These assays demonstrated that the values of FER, PER, NPU and BV of WD-pasta increased with increasing SF supplementation. However, high-fiber pasta made of unrefined WD solely or with SF had lower DC values compared to that of the regular DS-pasta. DC values decreased as the added SF increased. Adding methionine evidently affected FER, PER, BV and NPU values. Administration of high-protein and high-fiber pasta samples made of WD solely, supplemented with SF or SF plus methionine significantly reduced the elevated blood glucose as well as plasma cholesterol and plasma lipid fractions in hypercholesterolemic diabetic rats. Overall, considering nutritional evaluation, protein cost as well as hypoglycemic and hypocholesterolemic effects the pasta composed of 12% SF-WD and supplemented with 0.3% methionine represented the best high-fiber; high-protein and high-quality product.