The glycemic index: similarity of values derived in insulin-dependent and non-insulin-dependent diabetic patients

To see whether relative differences in the glycemic responses to different foods were similar in insulin-dependent (IDDM) and non-insulin-dependent diabetic patients (NIDDM) we determined the glycemic index (GI) of a total of 20 foods and mixed test meals in groups of IDDM and NIDDM volunteers. The mean GI values ranged from 32 in NIDDM and 41 in IDDM (pearled barley) to 105 in NIDDM and 111 in IDDM (bread with cheese and tomato). The correlation between the mean GI values in IDDM and NIDDM was highly significant (r = 0.927, p less than 0.001). The mean GI values for 15 of the 20 test meals was greater in IDDM than in NIDDM (mean of GI for all 20 foods, 76 in IDDM compared with 68 in NIDDM, p less than 0.005). However, the difference in GI between IDDM and NIDDM was t statistically significant for 19 of the 20 individual test meals. Greater within-individual variability of glycemic responses in IDDM probably accounts for the slightly greater mean GI value seen in IDDM compared with NIDDM. The addition of 32 g cheddar cheese to four foods which were also fed without cheese had no significant effect on the GI in NIDDM (mean GI of 68 without cheese compared with 72 for the meals with cheese), but had a small effect in IDDM where the mean GI was increased from 72 to 87 (p less than 0.05). However, despite small increases in glycemic response to foods with added cheese, the relative differences between foods were unaffected by the addition of cheese in both IDDM and NIDDM. It is concluded that mean GI values for foods are very similar in IDDM and NIDDM patients.     

The glycemic index: variation between subjects and predictive difference

It is not known whether the variability of the glycemic index (GI) in different subjects is due to within- or between-individual variation. In addition, it is not known how large a difference in GI between different meals is clinically important for individuals with diabetes. Therefore, insulin-dependent (IDDM) and non-insulin-dependent (NIDDM) diabetic subjects tested four foods, with each food taken by each subject on two separate occasions. For each food, most of the variation of absolute glycemic responses was due to differences between the subjects. However, when the results were expressed as the GI, there were no significant differences between the subjects, and most of the variation was due to within-individual variation. Using the within-individual variance, we estimated the so-called "predictive difference" of GI values. Its reliability was assessed by consideration of published data from eight studies where different mixed meals were taken by the same group of subjects. There were 37 cases where the difference between the GI of any two meals was greater than the predictive difference. Of these 37 pairs of meals, the GI correctly ranked the glycemic responses in 36 (97%). We conclude that GI values for the same food do not vary significantly between different individuals. For a subject with NIDDM a difference in GI of 34 will predict the ranking of glycemic responses of two meals with 95% probability. The corresponding value for a subject with IDDM is 50.     

Low glycemic response to traditionally processed wheat and rye products: bulgur and pumpernickel bread

To look at the effect of processing wheat and rye on blood glucose responses with special reference to bulgur and pumpernickel bread, groups of 9-12 Noninsulin-dependent (NIDDM) and 5-6 Insulin-dependent diabetic volunteers (IDDM) were fed test meals containing 50 g carbohydrate portions of four wheat and three rye products. Glycemic indices for IDDM and NIDDM combined, calculated as the incremental area under the blood glucose response curve, where white bread = 100, demonstrated values of 96 +/- 5 for wholemeal wheat bread, 89 +/- 6 for wholemeal rye bread, 78 +/- 3 for pumpernickel bread, 65 +/- 4 for bulgur, 63 +/- 6 for whole wheat kernels and 48 +/- 5 for whole rye kernels. Results for IDDM and NIDDM were similar (r = 0.96, p less than 0.01). It is concluded that traditional processing of cereals, such as parboiling (bulgur) or the use of wholegrains in bread (pumpernickel) may result in the low GI value associated with the unmilled cereal. Cereal foods processed in these ways may form a useful part of the diet where a reduction in postprandial glycemia is required.     

Insulinemic and glycemic indexes of six starch-rich foods taken alone and in a mixed meal by type 2 diabetics

The glycemic index concept neglects the insulin secretion factor and has not been systematically studied during mixed meals. Six starch-rich foods were tested alone and in an isoglucido-lipido-protidic meal in 18 NIDDs and compared with a glucose challenge. These test meals were randomly assigned using a three factor experiment design. All three tests contained 50 g carbohydrate; mixed meals were adjusted to bring the same amount of fat (20 g), protein (24 g), water (300 mL), and calories (475 kcal) but not the same amount of fiber. Whatever the tested meals, foods elicited a growing glycemic index hierarchy from beans to lentils, rice, spaghetti, potato, and bread (mean range: 0.21 +/- 0.12-92 +/- 0.12, p less than 0.001). Mixing the meals significantly increased the insulinemic indexes (p less than 0.05) and introduced a positive correlation between glycemic and insulinemic indexes (n = 6, r = 0.903; p less than 0.05). The glycemic index concept remains discriminating, even in the context of an iso-glucido-lipido-protidic meal. Insulinemic indexes do not improve discrimination between foods taken alone in type 2 diabetics: they only discriminate between foods during mixed meals, similarly to glycemic indexes.     

The use of the glycemic index in predicting the blood glucose response to mixed meals

There has been much interest in the use of the glycemic index (GI). A recent study reporting plasma glucose responses to mixed meals containing fat and protein concluded that the results were totally disparate from what would have been expected from published GI values of the foods fed. However, this conclusion was based upon an inappropriate assessment of the data using absolute rather than incremental blood glucose response areas. The present report demonstrates how data may be analyzed to make use of the GI values of individual foods to predict the GI of mixed meals (r = 0.987; p less than 0.02). It is concluded that the GI concept applies well to mixed meals containing fat and protein.     

Mid-arm circumference and mid-arm circumference: head circumference ratio for assessing longitudinal growth in hospitalized preterm infants.

In order to study the usefulness of upper mid-arm circumference (MAC) and mid-arm circumference:head circumference ratio (MAC:HC) measurements in assessing longitudinal growth in hospitalized preterm infants, we prospectively measured weights, lengths, occipitofrontal head circumferences (OFC), MACs, MAC:HCs, weight/length for age, nutritional intakes, and serum transthyretin and albumin levels in 50 preterm, low-birth-weight, appropriate for gestational age newborn infants during their first 4 postnatal weeks and at hospital discharge. At some time during hospitalization, weight measurements were abnormal (greater than or equal to 2SD from the gestational age mean) in 48% of the infants as compared with 24% with abnormal MAC measurements (p = 0.002). Abnormal MAC:HCs occurred in 25% of the infants as compared with 68% with abnormal weight/length for age values (p less than 0.001). During weeks 2-4, when nutritional intakes were adequate and serum transthyretin and albumin levels were normal, mean weight gain velocity was less than intrauterine rates and was significantly slower than MAC velocities, which were at or greater than intrauterine rates (p less than 0.001). At discharge, when all infants were gaining weight at intrauterine rates, weight measurements were still abnormal in 28% of the infants as compared with 10% of infants who had abnormal MACs (p = 0.005). Similarly, only 12% of infants had abnormal MAC:HCs as compared with 25% of infants with abnormal weight/length for age values at discharge (p = 0.05). The MAC and MAC:HC are useful for assessing longitudinal growth in preterm infants since they do not overestimate the prevalence of malnourishment during periods of apparent protein-calorie sufficiency.     

Application of glycemic index to mixed meals

Plasma glucose and insulin responses to six different meals were determined and compared with values predicted by published glycemic indices of the component foods. The test meals were of different ethnic origins: Indian (lentil curry with rice), Italian (spaghetti bolognaise), Chinese (stir-fried vegetables and chicken with rice), Greek (lentil stew), Western (sirloin chop and vegetables); and Lebanese (sandwich with unleavened bread and hummos). Eight healthy volunteers were given 50 g carbohydrate portions of the above meals after an overnight fast. The glycemic and insulin indices were highest for the Lebanese meal and lowest for the Greek with significant differences among the meals (ANOVA, p less than 0.05). The observed glycemic indices correlated well with the predicted glycemic indices (r = 0.88, p less than 0.01) and insulin responses parallelled the glycemic responses (r = 0.83, p less than 0.05). These results suggest that the glycemic index approach will be useful in planning diets for diabetic people.     

Recollections of pioneers in nutrition: fifty years in nutrition.

Objectives: To determine glycemic, insulinemic, and satiety indices of 3 types of kefir.

Methods: This study was divided into 3 phases. In phase 1, 50 g of available carbohydrate from low-fat strawberry kefir or orange kefir was tested, and in phase 2, low-fat plain kefir containing 25 g of available carbohydrates was tested for glycemic index (GI), in both cases compared with an equivalent amount of glucose. In phase 3, 1000-kJ portions of all 3 types of kefirs were compared with white bread with the same energy content to determine the insulinemic index (II) and satiety index (SI) of all 3 kefirs. In all phases, a single-meal, randomized crossover design was performed in which the test meals were given to healthy adults, 5 men and 5 women.

Results: The total incremental plasma glucose area under the curve (iAUC) for strawberry, orange, and plain kefirs was significantly lower compared with the respective high-GI control food, which was glucose solution. However, the IIs and SIs of kefir did not differ significantly from the white bread.

Conclusion: Kefir is a low- to moderate-GI food; however, its II was high. Although kefir had higher water content, the SI of kefir was not significantly different from white bread.     

Glycemic and insulinemic responses after ingestion of ethnic foods by NIDDM and healthy subjects.

In an attempt to apply the concept of glycemic index (GI) and insulinemic index (II) to local eating habits, we examined the plasma glucose and insulin responses in subjects with non-insulin-dependent diabetes mellitus (NIDDM) and healthy subjects to five mixed meals of different ethnic origins. All meals contained 50 g carbohydrate and were compared with a 50-g glucose load. The GI was highest for the Polish dish and lowest for the Syrian dish (66 +/- 5.5 vs 24 +/- 5.1). However, the II was the highest for the standard meal and lowest again for the Syrian dish (174 +/- 27 vs 66 +/- 25). A high correlation was found between the area under the glucose curve and the predicted GI in both NIDDM and healthy subjects. The GI concept is valid and potentially useful in diet planning and legume foods should be incorporated as a carbohydrate source when diets are being planned for NIDDM subjects or individuals with impaired glucose tolerance.     

Food glycemic index, as given in glycemic index tables, is a significant determinant of glycemic responses elicited by composite breakfast meals

BACKGROUND: Recent studies have concluded that the carbohydrate content and glycemic index (GI) of individual foods do not predict the glycemic and insulinemic effects of mixed meals. We hypothesized that these conclusions may be unwarranted because of methodologic considerations. OBJECTIVE: The aim was to ascertain whether the GI and carbohydrate content of individual foods influence glucose and insulin responses elicited by realistic mixed meals in normal subjects. DESIGN: With the use of a crossover design, we determined the glucose and insulin responses of 6 test meals in 16 subjects in Sydney and the glucose responses of 8 test meals in 10 subjects in Toronto and then the results were pooled. The 14 different test meals varied in energy (220-450 kcal), protein (0-18 g), fat (0-18 g), and available carbohydrate (16-79 g) content and in GI (35-100; values were rounded). RESULTS: The glucose and insulin responses of the Sydney test meals varied over a 3-fold range (P < 0.001), and the glucose responses of the Toronto test meals varied over a 2.4-fold range (P < 0.001). The glucose responses were not related to the fat or protein content of the test meal. Carbohydrate content (P = 0.002) and GI (P = 0.022) alone were related to glucose responses; together they accounted for 88% of the variation in the glycemic response (P < 0.0001). The insulin response was significantly related to the glucose response (r = 0.94, P = 0.005). CONCLUSIONS: When properly applied in realistic settings, GI is a significant determinant of the glycemic effect of mixed meals in normal subjects. For mixed meals within the broad range of nutrient composition that we tested, carbohydrate content and GI together explained approximately 90% of the variation in the mean glycemic response, with protein and fat having negligible effects.     

Second-meal effect: low-glycemic-index foods eaten at dinner improve subsequent breakfast glycemic response

The effects of the glycemic index (GI) of carbohydrate eaten the previous night on the glycemic response to a standard test meal eaten subsequently in the morning (breakfast) was studied. On separate evenings normal subjects ate low- or high-GI test meals of the same nutrient composition. The dinners consisted of single foods in two experiments and mixed meals containing several foods in the third. The differences between the observed glycemic responses to low- and high-GI dinners were predicted by their GIs. The glycemic responses to breakfast were significantly lower on mornings after low-GI dinners than after high-GI dinners. Eating, at dinner, foods with different fiber contents but the same GI had no effect on postbreakfast glycemia. We conclude that the GI predicts the difference between glycemic responses of mixed dinner meals; breakfast carbohydrate tolerance is improved when low-GI foods are eaten the previous evening.     

Food habits and nutrient intakes of Nigerian University students in traditional halls of residence.

Dietary intake analysis, over 7 days, of 120 randomly selected Nigerian University students aged 17-26 years, disclosed deviations from internationally accepted standards. The students were in residence at the University, where all meals were provided. Food preferences and habits were determined by questionnaire, and nutrient intake was calculated from weighed meals eaten over a 7-day period. Food intake of 95% of the students did not differ from that at home; 73% missed breakfast. The energy intake of the men (14.79 +/? 1.49 MJ/day) was significantly (p less than 0.01) higher than that of women (13.82 +/? 0.68 MJ/day); the differences increased in the older students. The energy ingested exceeded that recommended by the FAO/WHO. Protein intakes was 95.6 +/? 20.69 g/day and 102.2 +/? 10.9 g/day for women and men, respectively, also substantially above the FAO/WHO recommendations. Thiamin and vitamin A intakes were above and riboflavin intake of men and of the 20-26-year-old women was below requirements. The intakes of iron were above, and of calcium were below the FAO recommendation of 0.5 g/day.     

Glycemic index of processed wheat products

Our aim was to determine the in vivo glycemic and insulin responses and in vitro starch digestibility of seven processed wheat products (shortbread biscuits, custard, quick-cooking wheat, wholemeal bread, water biscuits, puffed wheat, and puffed crispbread). The degree of starch gelatinization in the foods was measured. Fifty-gram carbohydrate portions of the foods were fed to eight volunteers after an overnight fast. The calculated glycemic indices (GI) (mean +/- SEM) ranged from 43 +/- 10 for custard to 81 +/- 9 for puffed crispbread. Insulin responses paralleled the glycemic responses. The GI correlated positively with the percentage of starch digested in vitro (p less than 0.05). The degree of starch gelatinization ranged from 0.4 to 60% and correlated positively with the percentage starch digested in vitro (p less than 0.05). Differences in the glycemic and insulin responses to wheat products may be explained in part by the extent of processing and the degree of gelatinization achieved.     

Prediction of glycemic response to mixed meals in noninsulin-dependent diabetic subjects

Recent studies suggest the glycemic response of different mixed meals cannot be predicted from the glycemic index (GI) of individual carbohydrate foods. Postprandial glucose levels following five different mixed meals in six noninsulin-dependent diabetic volunteers were therefore assessed. Each meal comprised 50% carbohydrate, 30% fat, and 20% protein, varying only in type of carbohydrate. The carbohydrate exchanged in each meal (potato, white bread, rice, spaghetti, or lentils and barley) contributed 37% of total meal calories. The correlation between predicted glucose response and postprandial glucose area was highly significant; estimated meal GI was virtually proportional to the actual mean glycemic response. These results demonstrate that the relative glycemic effects of mixed meals can be predicted from the GI of their carbohydrate components, again stressing the importance of type of carbohydrate in regulating postprandial blood-glucose levels.     

Ultrahigh-Viscosity Hydroxypropylmethylcellulose Blunts Postprandial Glucose after a Breakfast Meal in Women

Objective: To determine the effects of two water-soluble dietary fibers, ultrahigh-viscosity hydroxypropylmethylcellulose (UHV-HPMC, nonfermentable) and psyllium fiber (fermentable), on postprandial glucose and second meal effects.

Methods: In a single-blind crossover design, 12 healthy adult subjects were given standardized, premeasured breakfast and lunch meals with either 4 g of the fiber supplements or a placebo. Blood glucose was measured with a continuous blood glucose monitoring system (DexCom Seven Plus, San Diego, CA).

Results: Subjects consuming UHV-HPMC had significantly (p < 0.05) lower blood glucose area under the curve (AUC) 2 hours after breakfast than those receiving a placebo. Subjects consuming psyllium also tended to have lower glucose levels than the placebo group. Peak glucose concentration following breakfast was significantly (p < 0.01) less with UHV-HPMC when compared with the placebo. No significant differences in AUC or peak glucose concentration between treatments following the second meal (lunch) were detected, suggesting no residual effect from the fiber supplements.

Conclusions: Supplementation with viscous water-soluble fibers may be an effective means of reducing the glycemic response of a meal in healthy adults.     

Glycemic index of American-grown jasmine rice classified as high

The primary objective was to determine the glycemic index (GI) of jasmine rice grown in the United States (US). Secondary objective was to compare the GI of US grown jasmine rice to those grown in Thailand. Twelve healthy subjects were served all four brands of jasmine rice and a reference food (glucose), each containing 50?g of available carbohydrate. Fingerstick blood glucose was measured at 0, 15, 30, 45, 60, 90, and 120?min after consumption following a fasting state. The GI was calculated using the standard equation. The GI values for test foods ranged from 96 to 116 and were all classified as high GI foods. No difference in GI was found between American-grown and Thailand-grown jasmine rice. Although not statistically significant, observations show glycemic response among Asian American participants may be different. GI should be considered when planning meals with jasmine rice as the main source carbohydrate.     

Influence of training status on glycemic index

The glycemic index (GI) represents the relative postprandial blood glucose response to the ingestion of a food containing carbohydrate. Although regular physical exercise may influence glucose metabolism, it is not yet known if chronically performed exercise also affects the GI. The objective of this study was, therefore, to determine the GI of common meals (three breakfast cereals: B, C, D) in healthy, nonsmoking young males 2 who were either endurance-trained (n = 12) or sedentary (n = 11). Glucose was used as the reference food. The GI value between the endurance-trained and sedentary subjects differed significantly (p < 0.01). Pair-wise comparisons between endurance-trained and sedentary subjects within the different test meals were significant for test meal D (p = 0.002), marginally non-significant for meal C (p = 0.052) and not significant for meal B (p = 0.204). These results suggest that the GI of some complex foods may depend on the training status of healthy young subjects.     

Immunological Response in Egg-Sensitive Adults Challenged with Cheese Containing or Not Containing Lysozyme

Objective: Lysozyme is an enzyme that hydrolyzes bacterial peptidoglicans. For this reason, it is used in cheese manufacturing in order to prevent a defect of long-ripened hard cheese called “late blowing” due to the outgrowth of spores of Clostridium tyrobutyricum and Clostridium butyricum. Moreover, germination of Listeria monocytogenes spores into vegetative cells is also sensitive to lysozyme. The enzyme can be an allergenic molecule, and for this reason there are concerns about its use in food industry. The immunological and clinical response of consumption of lysozyme-containing cheese has been evaluated in 25 egg-sensitive subjects with or without lysozyme sensitization.

Methods: A total of 25 egg-sensitive subjects were enrolled in this study. All the subjects were already treated for egg-sensitization and presented a positive skin prick test. All the subjects had a body mass index ≤25 kg/m² and were in the age range of 20–50 years. Each subject was studied twice and received randomly 30 g of Grana Padano (containing lysozyme) or TrentinGrana cheese (lysozyme-free) of two different aging periods: 16 or 24 months. A washout period of 1 week between each cheese intake was adopted. Blood samples were taken in fasting conditions and 1 hour after cheese intake and IgA, total IgE, and lysozyme-, ovomucoid-, and ovalbumin-specific IgE were measured.

Results: No adverse reactions were observed in both groups of patients after cheese samples were given. Lysozyme did not determine any variation of specific IgE compared with basal level. In lysozyme-sensitive patients a significant relationship between IgA and lysozyme-specific IgE was observed when lysozyme-containing cheese was given, confirming that lysozyme can pass the gut barrier.

Conclusions: Neither adverse events nor immunological responses were observed after ingestion of cheese containing lysozyme. However, the immunological properties of peptides deriving from cheese protein hydrolysis need to be clarified, as does the effect of lysozyme on bacterial proteolytic activity.     

Glycaemic responses to cereal-based Indian food preparations in patients with non-insulin-dependent diabetes mellitus and normal subjects

The in vivo glycaemic responses to six cereal-based foods traditionally consumed in South India were evaluated in patients with non-insulin-dependent diabetes mellitus (NIDDM) and healthy volunteers. All foods contained 50 g carbohydrate and were compared with a 50 g glucose load. Also studied were the in vitro starch digestibility and nutrient composition of the foods. The postprandial responses to the foods at 30, 60 and 120 min were significantly (P < 0.05) lower than those to the reference glucose, in both groups. The peak glucose responses for three foods, i.e. chapatti, idli and poori, occurred 60 min postprandially in both groups. The glycaemic index (GI) values ranged from 67 to 90 in NIDDM and from 44 to 69 in healthy subjects with no significant differences within the groups. Significant relationships were observed between peak responses and area under the curve for foods in patients with NIDDM and in vitro rate of starch hydrolysis (r 0.83, r 0.85, P < 0.05). The GI values predicted using in vitro data were found to be similar to the GI values observed in patients with NIDDM. The GI concept is useful for identifying foods in the habitual Indian diet with attributes of the desired glycaemic effect such as delayed peak rise and low area under the curve.     

Glycemic response and glycemic index of semolina spaghetti enriched with barley β-glucan

Objective

The postprandial glycemic response and glycemic index (GI) of spaghetti made with semolina and the addition of two β-glucan barley concentrates, Glucagel (GG) and Barley Balance (BB), was studied.

Methods

For each type of β-glucan concentrate, six spaghetti samples containing increasing percentages (0%, 2%, 4%, 6%, 8%, and 10%) of β-glucan were made. Nine healthy subjects were recruited for measuring the glycemic response and GI. Subjects were served portions of the test foods (50 g of available carbohydrates) and a reference food (50 g of glucose) on separate occasions. Capillary blood glucose was measured up to 120 min after consuming the spaghetti. The total glycemic response was calculated geometrically as the incremental areas under the curve (IAUC) using the trapezoid rule. The GI was calculated geometrically by expressing the IAUC for the test food as a percentage of each subject’s average IAUC for the glucose.

Results

The IAUC for spaghetti with and without β-glucan was significantly less compared with glucose. The GG spaghetti had IAUC values similar to the spaghetti without β-glucan concentrate. The BB spaghetti showed IAUC values lower than that of the spaghetti without β-glucan. In particular, the spaghetti with 10% BB had an IAUC 52% lower (P ≤ 0.017) than the spaghetti with β-glucan. The GI values for spaghetti with GG were statistically similar to the control. The GI of BB spaghetti decreased with increasing BB concentrations. In particular, the GI of 10% BB spaghetti was 54% lower (P ≤0.02; GI = 29) than that of the control (GI = 64).

Conclusion

The BB concentrate significantly decreases the IAUC and GI of spaghetti at a dose of 10%. GI at the same concentrations does not.