Glycemic index of foods in individual subjects

Effects of Far-Infrared Radiation Drying on Starch Digestibility and the Content of Bioactive Compounds in Differently Pigmented Rice Varieties

Far infrared radiation (FIR) was applied to six rice varieties with different coloring of the pericarp (purple, red or non-pigment). Changes were determined in amylose content, in gelatinization parameters, in the content of bioactive compounds, in antioxidant activity and in the in vitro digestibility of pigmented rice as affected by FIR. The highest contents of amylose, total phenolic (TPC), total flavonoid (TFC) and total anthocyanins (TAC) were found in the purple and red varieties. Overall, FIR increased TPC, TFC and TAC, including antioxidant capacity. Quercetin and apigenin contents were increased while rutin and myricetin decreased significantly (p < 0.05) in all FIR-dried samples. Dephinidin, cyanidin-3-glucosides and pelargonidin increased after FIR treatment. Mostly, FIR-treated samples were found to have greater gelatinization enthalpy, compared with unheated rice samples. FIR-dried rice showed lower starch digestibility (25−40%) than unheated rice. This research suggested that the specific genotype of rice had the greatest influence on amylose content in pigmented rice, while FIR drying had no further effect. Our results suggest that FIR could enhance the content of the bioactive compounds capable of inhibiting α-amylase, thereby lowering starch digestibility. Hence, FIR may be considered as an appropriate drying method for pigmented rice regarding health benefits.

Resistant starch levels and in vitro starch digestibility of selected cooked Philippine brown and milled rices varying in apparent amylose content and glycemic index

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Resistant starch content of rice correlates well with apparent amylose content.

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Cooked brown rices generally have more resistant starch than cooked milled rices.

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Resistant starch, hydrolysis index, and glycemic index of rice are all correlated.

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In vitro starch digestibility of cooked milled rice is greater than brown rice.

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Starch digestibility properties of cooked rice are vital in human nutrition and health.

Resistant starch (RS) content, starch digestibility, and hydrolysis index (HI) were analyzed in vitro for four selected Philippine rice varieties varying in apparent amylose content (AC) and glycemic index (GI), in cooked brown and milled rice forms. Starch digestibility curves were studied in relation to AC and reported GI values. Brown and milled rices of Improved Malagkit Sungsong 2 (IMS2), NSIC Rc160, IR64, and PSB Rc10 were cooked on separate beakers placed in automatic electric rice cookers and based on pre-determined water:rice ratios. RS levels of cooked milled rices ranged from 0.15 to 0.99% (mean = 0.45%). Their corresponding cooked brown rices had RS contents ranging from 0.24 to 1.61% (mean = 1.05%), with PSB Rc10 having the highest levels in both forms. HI ranged from 59.3 to 102.2%, with the highest noted for the waxy rice, IMS2, while corresponding brown rices had significantly lower HI spanning 49.2–66.9%. Previously reported GI values of these varieties were positively correlated with HI and estimated GI in this study. RS and non-resistant starch levels, and HI were highly correlated with AC. In vitro starch digestibility studies, as related to AC and GI, may be useful in screening for rice grain and nutritional properties aimed at developing new varieties with desirable quality and enhanced nutritional and functional properties.

A systematic review on the relations between pasta consumption and cardio-metabolic risk factors

AIMS

The traditional Italian dish pasta is a major food source of starch with low glycemic index (GI) and an important low-GI component of the Mediterranean diet. This systematic review aimed at assessing comprehensively and in-depth the potential benefit of pasta on cardio-metabolic disease risk factors.

DATA SYNTHESIS

Following a standard protocol, we conducted a systematic literature search of PubMed, CINAHL, and Cochrane Central Register of Controlled Trials for prospective cohort studies and randomized controlled dietary intervention trials that examined pasta and pasta-related fiber and grain intake in relation to cardio-metabolic risk factors of interest. Studies comparing postprandial glucose response to pasta with that to bread or potato were quantitatively summarized using meta-analysis of standardized mean difference. Evidence from studies with pasta as part of low-GI dietary intervention and studies investigating different types of pasta were qualitatively summarized.

CONCLUSIONS

Pasta meals have significantly lower postprandial glucose response than bread or potato meals, but evidence was lacking in terms of how the intake of pasta can influence cardio-metabolic disease risk. More long-term randomized controlled trials are needed where investigators directly contrast the cardio-metabolic effects of pasta and bread or potato. Long-term prospective cohort studies with required data available should also be analyzed regarding the effect of pasta intake on disease endpoints.

Blood Glucose Discrimination Training: The Role of Internal and External Cues

The effects of observing internal and external events on blood glucose (BG) discrimination were assessed in eight patients with type 1 diabetes using an intrasubject design. During baseline condition, participants estimated their BG, then measured and recorded it (feedback-only procedure) three times a day. Participants were then divided randomly into two groups. Both were submitted to internal cue (IC) and external cue (EC) training conditions in a balanced order, and then both cues were presented together in combined cues (CC) training conditions. Under IC, participants observed and recorded their symptoms before estimating BG. Under EC, they observed and recorded environmental events prior to BG estimation. In CC conditions, participants paid attention to both internal and external cues before the estimate–feedback routine. BG estimation accuracy improved after either IC or EC conditions. When the two types of cues were combined, only two participants improved their BG estimation accuracy. The remainder did not, probably because they had already attained high accuracy levels (ceiling effect).

Effect of ethnicity on glycaemic index: a systematic review and meta-analysis

Objectives:

Low glycaemic index (GI) foods are recommended to improve glycaemic control in diabetes; however, Health Canada considers that GI food labeling would be misleading and unhelpful, in part, because selected studies suggest that GI values are inaccurate due to an effect of ethnicity. Therefore, we conducted a systematic review and meta-analysis to compare the GI of foods when measured in Caucasians versus non-Caucasians.

Methods:

We searched MEDLINE, EMBASE and Cochrane databases for relevant articles. GI differences were aggregated using the generic inverse variance method (random effects model) and expressed as mean difference (MD) with 95% confidence intervals (95% CI). Study quality was assessed based on how well studies complied with official international GI methodology.

Results:

Review of 1288 trials revealed eight eligible studies, including 28 comparisons of GI among 585 non-Caucasians and 971 Caucasians. Overall, there was borderline significant evidence of higher GI in non-Caucasians than Caucasians (MD, 3.3 (95% CI, −0.1, 6.8); P=0.06) with significant heterogeneity (I², 46% P=0.005). The GI of eight types of rice was higher in non-Caucasians than Caucasians (MD, 9.5 (95% CI, 3.7, 23.1); P=0.001), but there was no significant difference for the other 20 foods (MD, 1.0 (95% CI, −2.5, 4.6); P=0.57). MD was significantly greater in the four low-quality studies (nine comparisons) than the four high-quality studies (19 comparisons; 7.8 vs 0.7, P=0.047).

Conclusions:

With the possible exception of rice, existing evidence suggests that GI values do not differ when measured in Caucasians versus non-Caucasians. To confirm these findings high-quality studies using a wide range of foods are required.

Is glycaemic index (GI) a valid measure of carbohydrate quality?

Recent criticisms of the glycaemic index (GI) focus on its validity with assertions that GI methodology is not valid, GI values are inaccurate and imprecise, GI does not predict what foods are healthy and that whole grain and fibre are better markers of carbohydrate quality than GI. None of the critics provide sound reasons for rejecting GI because some of their arguments are based on flagrant errors in understanding and interpretation while others are not supported by current data or are inconsistent with other nutritional recommendations. This paper addresses current criticisms of GI and outlines reasons why GI is valid: (1) GI methodology is accurate and precise enough for practical use; (2) GI is a property of foods; and (3) GI is biologically meaningful and relevant to virtually everyone. Current dietary guidelines recommend increased consumption of whole grains and dietary fibre but do not mention GI. However, this is illogical because the evidence that GI affects health outcomes is at least as good or better than that for whole grains and fibre. GI is a novel concept from a regulatory point of view and a number of problems need to be addressed to successfully translate GI knowledge into practice. The problems are not insurmountable but no progress can be made until bias and misunderstanding about GI can be overcome and there is better agreement about what is the actual state of knowledge on GI so that the real issues can be identified and addressed.

Methodology for adding glycemic index to the National Health and Nutrition Examination Survey nutrient database

Generating valid estimates of dietary glycemic index (GI) and glycemic load (GL) has been a challenge in nutritional epidemiology. The methodologic issues may have contributed to the wide variation of GI/GL associations with health outcomes observed in existing literature. We describe a standardized methodology for assigning GI values to items in the National Health and Nutrition Examination Survey (NHANES) nutrient database using the new International Tables to develop research-driven, systematic procedures and strategies to estimate dietary GI/GL exposures of a nationally representative population sample. Nutrient databases for NHANES 2003-2006 contain information on 3,155 unique foods derived from the US Department of Agriculture National Nutrient Database for Standard Reference versions 18 and 20. Assignment of GI values were made to a subset of 2,078 carbohydrate-containing foods using systematic food item matching procedures applied to 2008 international GI tables and online data sources. Matching protocols indicated that 45.4% of foods had identical matches with existing data sources, 31.9% had similar matches, 2.5% derived GI values calculated with the formula for combination foods, 13.6% were assigned a default GI value based on low carbohydrate content, and 6.7% of GI values were based on data extrapolation. Most GI values were derived from international sources; 36.1% were from North American product information. To confirm data assignments, dietary GI and GL intakes of the NHANES 2003-2006 adult participants were estimated from two 24-hour recalls and compared with published studies. Among the 3,689 men and 4,112 women studied, mean dietary GI was 56.2 (men 56.9, women 55.5), mean dietary GL was 138.1 (men 162.1, women 116.4); the distribution of dietary GI was approximately normal. Estimates of population GI and GL compare favorably with other published literature. This methodology of adding GI values to an existing population nutrient database utilized systematic matching protocols and the latest comprehensive data sources on food composition. The database can be applied in clinical and survey research settings where there is interest in estimating individual and population dietary exposures and relating them to health outcomes.

A comparative study on starch digestibility, glycemic index and resistant starch of pigmented ('Njavara' and 'Jyothi') and a non-pigmented ('IR 64') rice varieties

In vitro starch digestibility and glycemic indices of three rice varieties- 'Njavara', 'Jyothi' (pigmented rice verities) and 'IR 64' (non-pigmented rice) with similar amylose content were studied. Starch digestibility studies showed differences in glycemic response in three types of rice. The rate of starch hydrolysis was maximum (67.3%) in 'Njavara' rice compared to other two rice varieties. 'Njavara' exhibited the lowest kinetic constant (k) indicating inherent resistance to enzymatic hydrolysis. The glycemic load (GL) and glycemic index (GI) of 'Njavara' were similar to 'Jyothi' and 'IR 64'. Resistant starch content was high in pigmented rice varieties compared to 'IR 64'. The resistant starch content of dehusked and cooked rice increased with the storage time at refrigeration temperature (4°C). 'Njavara' is an easily digestible rice and can be used for baby and geriatric foods.

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.

Effect of blood sampling schedule and method of calculating the area under the curve on validity and precision of glycaemic index values

To evaluate the suitability for glycaemic index (GI) calculations of using blood sampling schedules and methods of calculating area under the curve (AUC) different from those recommended, the GI values of five foods were determined by recommended methods (capillary blood glucose measured seven times over 2·0 h) in forty-seven normal subjects and different calculations performed on the same data set. The AUC was calculated in four ways: incremental AUC (iAUC; recommended method), iAUC above the minimum blood glucose value (AUCmin), net AUC (netAUC) and iAUC including area only before the glycaemic response curve cuts the baseline (AUCcut). In addition, iAUC was calculated using four different sets of less than seven blood samples. GI values were derived using each AUC calculation. The mean GI values of the foods varied significantly according to the method of calculating GI. The standard deviation of GI values calculating using iAUC (20·4), was lower than six of the seven other methods, and significantly less (P<0·05) than that using netAUC (24·0). To be a valid index of food glycaemic response independent of subject characteristics, GI values in subjects should not be related to their AUC after oral glucose. However, calculating GI using AUCmin or less than seven blood samples resulted in significant (P<0·05) relationships between GI and mean AUC. It is concluded that, in subjects without diabetes, the recommended blood sampling schedule and method of AUC calculation yields more valid and/or more precise GI values than the seven other methods tested here. The only method whose results agreed reasonably well with the recommended method (ie. within ±5 %) was AUCcut.

Nutritional correlates of dietary glycaemic index: new aspects from a population perspective

The role of dietary glycaemic index (GI) and glycaemic load (GL) in disease aetiology is of increasing interest. However, nutritional factors related to dietary GI and GL are not well understood from a population perspective. We aimed to investigate the relation ship between GI and GL and dietary intake at the food and nutrient level. Study subjects were 1071 non-diabetic adults from the Insulin Resistance Atherosclerosis Study, Exam I, 1992–4. Usual dietary intake was assessed with a 114-item modified Block food frequency questionnaire. Published GI values were assigned to food line items. Correlation and regression analyses were conducted. Intake of white bread, beer, meats and fries/fried potatoes was positively associated with average GI, as was fat, starch and alcohol intake (before and after energy adjustment). Intake of fruits and low-fat milk was inversely associated with GI, as were intakes of mono- and disaccharides, and fibre. GL was positively correlated with carbohydrate foods and inversely with non-carbohydrate foods. Gender-specific regression models identified eight food groups explaining 63 % (men) and 55 % (women) total GI variation after adjusting for demographics; 70 % of variation in GL was explained by eleven (men) and nine (women) food groups, respectively. Although the GI of a food is an indicator of the ability of carbohydrates to raise blood glucose, dietary GI, unlike GL, appears to reflect more dimensions of diet than just carbohydrates, such as the combination of foods consumed. This may have implications for the interpretation of dietary GI in epidemiologic studies.

Methodology for adding glycemic index and glycemic load values to 24-hour dietary recall database

OBJECTIVES

We describe a method of adding the glycemic index (GI) and glycemic load (GL) values to the nutrient database of the 24-hour dietary recall interview (24HR), a widely used dietary assessment. We also calculated daily GI and GL values from the 24HR.

METHODS

Subjects were 641 healthy adults from central Massachusetts who completed 9067 24HRs. The 24HR-derived food data were matched to the International Table of Glycemic Index and Glycemic Load Values. The GI values for specific foods not in the table were estimated against similar foods according to physical and chemical factors that determine GI. Mixed foods were disaggregated into individual ingredients.

RESULTS

Of 1261 carbohydrate-containing foods in the database, GI values of 602 foods were obtained from a direct match (47.7%), accounting for 22.36% of dietary carbohydrate. GI values from 656 foods (52.1%) were estimated, contributing to 77.64% of dietary carbohydrate. The GI values from three unknown foods (0.2%) could not be assigned. The average daily GI was 84 (SD 5.1, white bread as referent) and the average GL was 196 (SD 63).

CONCLUSION

Using this methodology for adding GI and GL values to nutrient databases, it is possible to assess associations between GI and/or GL and body weight and chronic disease outcomes (diabetes, cancer, heart disease). This method can be used in clinical and survey research settings where 24HRs are a practical means for assessing diet. The implications for using this methodology compel a broader evaluation of diet with disease outcomes.

Dietary glycemic index and glycemic load, carbohydrate and fiber intake, and measures of insulin sensitivity, secretion, and adiposity in the Insulin Resistance Atherosclerosis Study

OBJECTIVE

We studied the association of digestible carbohydrates, fiber intake, glycemic index, and glycemic load with insulin sensitivity (S(I)), fasting insulin, acute insulin response (AIR), disposition index, BMI, and waist circumference.

RESEARCH DESIGN AND METHODS

Data on 979 adults with normal (67%) and impaired (33%) glucose tolerance from the Insulin Resistance Atherosclerosis Study (1992-1994) were analyzed. Usual dietary intake was assessed via a 114-item interviewer-administered food frequency questionnaire from which nutrient intakes were estimated. Published glycemic index values were assigned to food items and average dietary glycemic index and glycemic load calculated per subject. S(I) and AIR were determined by frequently sampled intravenous glucose tolerance test. Disposition index was calculated by multiplying S(I) with AIR. Multiple linear regression modeling was employed.

RESULTS

No association was observed between glycemic index and S(I), fasting insulin, AIR, disposition index, BMI, or waist circumference after adjustment for demographic characteristics or family history of diabetes, energy expenditure, and smoking. Associations observed for digestible carbohydrates and glycemic load, respectively, with S(I), insulin secretion, and adiposity (adjusted for demographics and main confounders) were entirely explained by energy intake. In contrast, fiber was associated positively with S(I) and disposition index and inversely with fasting insulin, BMI, and waist circumference but not with AIR.

CONCLUSION

Carbohydrates as reflected in glycemic index and glycemic load may not be related to measures of insulin sensitivity, insulin secretion, and adiposity. Fiber intake may not only have beneficial effects on insulin sensitivity and adiposity, but also on pancreatic functionality.

Glycemic index, glycemic load, and dietary fiber intake and incidence of type 2 diabetes in younger and middle-aged women

BACKGROUND

Increasing evidence suggests an important role of carbohydrate quality in the development of type 2 diabetes.

OBJECTIVE

Our objective was to prospectively examine the association between glycemic index, glycemic load, and dietary fiber and the risk of type 2 diabetes in a large cohort of young women.

DESIGN

In 1991, 91249 women completed a semiquantitative food-frequency questionnaire that assessed dietary intake. The women were followed for 8 y for the development of incident type 2 diabetes, and dietary information was updated in 1995.

RESULTS

We identified 741 incident cases of confirmed type 2 diabetes during 8 y (716 300 person-years) of follow-up. After adjustment for age, body mass index, family history of diabetes, and other potential confounders, glycemic index was significantly associated with an increased risk of diabetes (multivariate relative risks for quintiles 1-5, respectively: 1, 1.15, 1.07, 1.27, and 1.59; 95% CI: 1.21, 2.10; P for trend = 0.001). Conversely, cereal fiber intake was associated with a decreased risk of diabetes (multivariate relative risks for quintiles 1-5, respectively: 1, 0.85, 0.87, 0.82, and 0.64; 95% CI: 0.48, 0.86; P for trend = 0.004). Glycemic load was not significantly associated with risk in the overall cohort (multivariate relative risks for quintiles 1-5, respectively: 1, 1.31, 1.20, 1.14, and 1.33; 95% CI: 0.92, 1.91; P for trend = 0.21).

CONCLUSIONS

A diet high in rapidly absorbed carbohydrates and low in cereal fiber is associated with an increased risk of type 2 diabetes.

High-fiber cereal reduces postprandial insulin responses in hyperinsulinemic but not normoinsulinemic subjects

OBJECTIVE

The objective of this study was to compare the plasma glucose and insulin responses elicited by two ready-to-eat breakfast cereals (one being high and the other being low in cereal fiber) and to see if the differences in response depended on subjects' fasting plasma insulin.

RESEARCH DESIGN AND METHODS

Nondiabetic men (n = 77) were studied on two occasions after 10- to 14-h overnight fasts. They consumed 25 g of available carbohydrate from high- or low-fiber breakfast cereals in random order with blood taken at intervals for 2 h. Data from the 42 men with high fasting plasma insulin (FPI) on screening (>40 pmol/l) were compared with those from the 35 men with normal FPI (< or =40 pmol/l).

RESULTS

Hyperinsulinemic men had significantly higher waist circumference and BMI, lower HDL cholesterol, and a trend toward higher triglycerides (P = 0.07) than control subjects. In all 77 subjects, the incremental area under the glucose response curve (AUC) after high-fiber cereal was 11.8 +/- 5.5% (P = 0.036) less than after low-fiber cereal with the reductions being equivalent in the hyperinsulinemic (12.6 +/- 8.3%) and control (10.9 +/- 9.1%) groups. However, insulin peak rise was reduced by the high-fiber cereal only in hyperinsulinemic men (351 +/- 29 vs. 485 +/- 55 pmol/l) but not in control subjects (211 +/- 20 vs. 220 +/- 20 pmol/l; cereal x group interaction P = 0.044). Insulin AUC after the high-fiber cereal, expressed as a percentage of that after low-fiber cereal, was negatively related to FPI (P = 0.009) but not to age, BMI, or waist circumference.

CONCLUSIONS

The high-fiber cereal reduced glucose responses to the same extent in normal and hyperinsulinemic men, but reduced insulin responses only in hyperinsulinemic subjects.

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.

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.

Bedtime uncooked cornstarch supplement prevents nocturnal hypoglycaemia in intensively treated type 1 diabetes subjects

OBJECTIVES

The present study tests two interrelated hypotheses: (1) that bedtime ingestion of uncooked cornstarch exerts a lower and delayed nocturnal blood glucose peak compared with a conventional snack; (2) that bedtime carbohydrate supplement, administered as uncooked cornstarch, prevents nocturnal hypoglycaemia without altering metabolic control in intensively treated type 1 diabetes (IDDM) patients.

DESIGN AND SUBJECTS

The above hypotheses were tested separately (1) by pooling and analysing data from two overnight studies of comparable groups of patients with non-insulin dependent diabetes mellitus (NIDDM) (14 and 10 patients, respectively), and (2) by a double-blind, randomized 4-week cross-over study in 12 intensively treated IDDM patients.

SETTING

Sahlgrenska University Hospital, Göteborg. Sweden.

INTERVENTIONS

(1) Ingestion of uncooked cornstarch and wholemeal bread (0.6 g of carbohydrates kg-1 body weight) and carbohydrate-free placebo at 22.00 h. (2) Intake of uncooked cornstarch (0.3 g kg-1 body weight) and carbohydrate-free placebo at 23.00 h.

MAIN OUTCOME MEASURES

(1) Nocturnal glucose and insulin levels; (2) frequency of self-estimated hypoglycaemia (blood glucose [BG] levels < 3.0 mmol L-1) at 03.00 h, HbA1c and fasting lipids.

RESULTS

Bedtime uncooked cornstarch ingestion led to a lower (2.9 +/- 0.5 vs. 5.2 +/- 0.6 mM, P = 0.01) and delayed (4.3 +/- 0.6 vs. 2.0 +/- 0.0 h, P < 0.01) BG peak, compared with a conventional snack, in NIDDM patients. Four weeks of bedtime uncooked cornstarch supplement, as compared with placebo, led to a 70% reduction in the frequency of self-estimated hypoglycaemia at 03.00 h (P < 0.05), without affecting HbA1c or fasting lipids in IDDM patients.

CONCLUSIONS

Uncooked cornstarch, ingested at bedtime, mimicked the nocturnal glucose utilization profile following insulin replacement, with a peak in blood glucose after 4 h. In IDDM patients, bedtime uncooked cornstarch supplement diminished the number of self-estimated hypoglycaemic episodes, without adversely affecting HbA1c and lipid levels. Hence, bedtime uncooked cornstarch ingestion may be feasible to prevent a mid-nocturnal glycaemic decline following insulin replacement in IDDM and, based on the nocturnal blood glucose profile, may also be preferable compared with conventional snacks.

Glycemic index and insulin response to a liquid nutritional formula compared with a standard meal

OBJECTIVE

To determine the glycemic index and metabolic responses to a nutritional formula, and to compare these responses to those following an oral glucose meal and a standard test meal.

METHODS

Six male and six female healthy non-diabetic volunteers aged 18 to 48 years met screening examination and laboratory assessment criteria. Three test meals were administered, each containing 50 g of carbohydrate: nutritional formula (NF), standard test meal (ST) and a glucose test meal (GT). Each subject underwent the three test meals on separate days in randomized sequence. Blood samples were taken at intervals over 5 hours for determination of glucose, insulin and triglycerides.

RESULTS

The glycemic index was similar for the NF (60.8 +/- 13.1) and for the ST (57.8 +/- 12.9) meals. The incremental area under the curve for glucose was similar for NF and ST, but each was significantly lower than for the GT meal. The total area under the curve for insulin was significantly greater for the NF meal than for the ST meal. The serum triglyceride responses were similar for NF and ST meals.

CONCLUSION

In healthy non-diabetic subjects, the blood glucose and triglyceride responses are similar for a nutritional formula compared to an isoenergetic standard test meal. However, the insulin response differs. This information is important in managing tube-fed patients.

Blood glucose rise following prenatal vitamins in gestational diabetes

Optimal outcome of gestational diabetes mellitus (GDM) is directly related to glucose control of the mother. If prenatal vitamins cause a large glycemic excursion, then the best prenatal vitamin would be one that produces the lowest blood glucose. Nine GDM women participated in two, 8-day test periods. Each subject ingested one of six prenatal vitamin-mineral preparations, a placebo, or a sucrose capsule, in random order. Blood glucose was determined by the One Touch System at 0, 30, and 60 minutes. The sucrose capsule contained 1 g sucrose (equivalent to highest glucose/carbohydrate content of any prenatal vitamin). The placebo contained 1 g table salt in the same color capsule. Relative glycemic index (RGI, defined as the area under glucose curve for the test substance divided by the area under glucose curve for 1 g sucrose) and maximum rise of blood glucose above time 0 were calculated for each preparation. RGI was significantly elevated for all vitamins: TRN 3.86, Natalins Rx 3.00, Filibon Forte 2.16, Prenatal Formula 2.10, Materna 1.66, Placebo 1.33, Stuartnatal 1 + 1 1.16. Two thousand mg vitamin C (n = 4) resulted in an RGI of 1.37. In conclusion, ingestion of prenatal vitamins produces a rise in blood glucose greater than that seen following ingestion of sucrose equal to the carbohydrate content of prenatal vitamins. The cause of the blood glucose rise is not known, but it would appear prudent to prescribe a prenatal vitamin with a low RGI.

Influence of the amount of starch on the glycaemic index to rice in non-insulin-dependent diabetic subjects

To test whether the glycaemic index is altered by the amount of carbohydrate, meals containing 25 and 50 g carbohydrate as white rice and white bread were taken by seven non-insulin-dependent diabetic subjects. The glycaemic indices to parboiled white rice corresponding to 25 and 50 g carbohydrate were similar, being 55 (SE 10) and 60 (SE 8) respectively. The incremental areas of blood glucose (above basal) to parboiled white rice were significantly lower than to white bread after both an amount corresponding to 25 g carbohydrate (85 (SE 24) mM x 180 min v. 181 (SE 55) mM x 180 min; P less than 0.01) and to 50 g carbohydrate 226 (SE 29) mM x 180 min v. 423 (SE 76) mM x 180 min; P less than 0.01). Similar insulin response areas to 25 g carbohydrate given as parboiled white rice and white bread were found, whereas 50 g carbohydrate as white bread caused a significantly higher insulin response area than parboiled white rice (P less than 0.05). In conclusion, the glycaemic index of parboiled white rice is not affected by the amount of carbohydrate ingested, at least under the present study conditions.

Influence of non-carbohydrate foods on glucose and insulin responses to carbohydrates of different glycaemic index in type 2 diabetic patients

In order to study the influence of non-carbohydrate foods on responses to carbohydrates during mixed meals, 30 Type 2 (non-insulin-dependent) diabetic patients followed a standardized diet for 5 consecutive days. On days 2, 3, 4, and 5, four different lunches were eaten in a randomized order. Lunches consisted of rice or glucose (50 g carbohydrate) eaten either alone, or as part of a mixed meal (32 g protein, 20 g fat). Glucose and insulin levels prior to the lunches did not differ significantly. Glucose and insulin responses differed (p less than 0.001), responses to rice being lower than responses to glucose, and responses to the meal plus rice lower than responses to the meal plus glucose. The ratios of glucose responses to rice and glucose (glycaemic index) were similar (alone, 47 +/- 4%; meal, 47 +/- 4%; NS). The ratios of the insulin responses did not differ (78 +/- 8 vs 96 +/- 7%; NS). The blood glucose responses to mixed meals were lower than responses to the carbohydrates eaten alone, the ratios being similar (rice, 52 +/- 3%; glucose, 58 +/- 5%; NS). Serum insulin responses were however higher, and the ratios differed (172 +/- 13 vs 138 +/- 14%; p = 0.05). These results suggest that the glycaemic index of isolated carbohydrate foods can predict the relative response to mixed meals in the same individuals with Type 2 diabetes. They also support the insulin secretagogue effect of non-carbohydrate foods, which may vary according to the source of carbohydrate in the meal.