Low-glycemic index diets in the management of diabetes: a meta-analysis of randomized controlled trials

OBJECTIVE

The use of diets with low glycemic index (GI) in the management of diabetes is controversial, with contrasting recommendations around the world. We performed a meta-analysis of randomized controlled trials to determine whether low-GI diets, compared with conventional or high-GI diets, improved overall glycemic control in individuals with diabetes, as assessed by reduced HbA(1c) or fructosamine levels.

RESEARCH DESIGN AND METHODS

Literature searches identified 14 studies, comprising 356 subjects, that met strict inclusion criteria. All were randomized crossover or parallel experimental design of 12 days' to 12 months' duration (mean 10 weeks) with modification of at least two meals per day. Only 10 studies documented differences in postprandial glycemia on the two types of diet.

RESULTS

Low-GI diets reduced HbA(1c) by 0.43% points (CI 0.72-0.13) over and above that produced by high-GI diets. Taking both HbA(1c) and fructosamine data together and adjusting for baseline differences, glycated proteins were reduced 7.4% (8.8-6.0) more on the low-GI diet than on the high-GI diet. This result was stable and changed little if the data were unadjusted for baseline levels or excluded studies of short duration. Systematically taking out each study from the meta-analysis did not change the CIs.

CONCLUSIONS

Choosing low-GI foods in place of conventional or high-GI foods has a small but clinically useful effect on medium-term glycemic control in patients with diabetes. The incremental benefit is similar to that offered by pharmacological agents that also target postprandial hyperglycemia.

Physicochemical properties of oat β-glucan influence its ability to reduce serum LDL cholesterol in humans: a randomized clinical trial

BACKGROUND

Consumption of 3 g oat β-glucan/d is considered sufficient to lower serum LDL cholesterol, but some studies have shown no effect. LDL cholesterol lowering by oat β-glucan may depend on viscosity, which is controlled by the molecular weight (MW) and amount of oat β-glucan solubilized in the intestine (C).

OBJECTIVES

Our 2 primary objectives were to determine whether consumption of 3 g high-MW oat β-glucan/d would reduce LDL cholesterol and whether LDL cholesterol lowering was related to the log(MW × C) of oat β-glucan.

DESIGN

In a double-blind, parallel-design, multicenter clinical trial, subjects with LDL cholesterol ≥3.0 and ≤5.0 mmol/L (n = 786 screened, n = 400 ineligible, n = 19 refused, n = 367 enrolled, and n = 345 completed) were randomly assigned to receive cereal containing wheat fiber (n = 87) or 3 g high-MW (2,210,000 g/mol, n = 86), 4 g medium-MW (850,000 g/mol, n = 67), 3 g medium-MW (530,000 g/mol, n = 64), or 4 g low-MW (210,000 g/mol, n = 63) oat β-glucan/d (divided doses, twice daily) for 4 wk.

RESULTS

LDL cholesterol was significantly less with 3 g high-MW, 4 g medium-MW, and 3 g medium-MW oat β-glucan cereals than with the wheat-fiber cereal by 0.21 (5.5%; 95% CI: -0.11, -0.30; P = 0.002), 0.26 (6.5%; 95% CI: -0.14, -0.37; P = 0.0007), and 0.19 (4.7%; 95% CI: -0.08, -0.30; P = 0.01) mmol/L, respectively. However, the effect of 4 g low-MW oat β-glucan/d (0.10 mmol/L) was not significant (2.3%; 95% CI: 0.02, -0.20). By analysis of covariance, log(MW × C) was a significant determinant of LDL cholesterol (P = 0.003). Treatment effects were not significantly influenced by age, sex, study center, or baseline LDL cholesterol.

CONCLUSIONS

The physicochemical properties of oat β-glucan should be considered when assessing the cholesterol-lowering ability of oat-containing products; an extruded breakfast cereal containing 3 g oat β-glucan/d with a high-MW (2,210,000 g/mol) or a medium-MW (530,000 g/mol) lowered LDL cholesterol similarly by ≈0.2 mmol/L (5%), but efficacy was reduced by 50% when MW was reduced to 210,000 g/mol. This trial was registered at www.clinicaltrials.gov as NCT00981981.

Acne vulgaris: a disease of Western civilization

BACKGROUND

In westernized societies, acne vulgaris is a nearly universal skin disease afflicting 79% to 95% of the adolescent population. In men and women older than 25 years, 40% to 54% have some degree of facial acne, and clinical facial acne persists into middle age in 12% of women and 3% of men. Epidemiological evidence suggests that acne incidence rates are considerably lower in nonwesternized societies. Herein we report the prevalence of acne in 2 nonwesternized populations: the Kitavan Islanders of Papua New Guinea and the Aché hunter-gatherers of Paraguay. Additionally, we analyze how elements in nonwesternized environments may influence the development of acne.

OBSERVATIONS

Of 1200 Kitavan subjects examined (including 300 aged 15-25 years), no case of acne (grade 1 with multiple comedones or grades 2-4) was observed. Of 115 Aché subjects examined (including 15 aged 15-25 years) over 843 days, no case of active acne (grades 1-4) was observed.

CONCLUSIONS

The astonishing difference in acne incidence rates between nonwesternized and fully modernized societies cannot be solely attributed to genetic differences among populations but likely results from differing environmental factors. Identification of these factors may be useful in the treatment of acne in Western populations.

Comparison of 4 diets of varying glycemic load on weight loss and cardiovascular risk reduction in overweight and obese young adults: a randomized controlled trial

BACKGROUND

Despite the popularity of low-glycemic index (GI) and high-protein diets, to our knowledge no randomized, controlled trials have systematically compared their relative effects on weight loss and cardiovascular risk.

METHODS

A total of 129 overweight or obese young adults (body mass index, > or =25 [calculated as weight in kilograms divided by the square of height in meters]) were assigned to 1 of 4 reduced-fat, high-fiber diets for 12 weeks. Diets 1 and 2 were high carbohydrate (55% of total energy intake), with high and low GIs, respectively; diets 3 and 4 were high protein (25% of total energy intake), with high and low GIs, respectively. The glycemic load was highest in diet 1 and lowest in diet 4. Changes in weight, body composition, and blood chemistry profile were studied.

RESULTS

While all groups lost a similar mean +/- SE percentage of weight (diet 1, -4.2% +/- 0.6%; diet 2, -5.5% +/- 0.5%; diet 3, -6.2% +/- 0.4%; and diet 4, -4.8% +/- 0.7%; P = .09), the proportion of subjects in each group who lost 5% or more of body weight varied significantly by diet (diet 1, 31%; diet 2, 56%; diet 3, 66%; and diet 4, 33%; P = .01). Women on diets 2 and 3 lost approximately 80% more fat mass (-4.5 +/- 0.5 [mean +/- SE] kg and -4.6 +/- 0.5 kg) than those on diet 1 (-2.5 +/- 0.5 kg; P = .007). Mean +/- SE low-density-lipoprotein cholesterol levels declined significantly in the diet 2 group (-6.6 +/- 3.9 mg/dL [-0.17 +/- 0.10 mmol/L]) but increased in the diet 3 group (+10.0 +/- 3.9 mg/dL [+0.26 +/- 0.10 mmol/L]; P = .02). Goals for energy distribution were not achieved exactly: both carbohydrate groups ate less fat, and the diet 2 group ate more fiber.

CONCLUSION

Both high-protein and low-GI regimens increase body fat loss, but cardiovascular risk reduction is optimized by a high-carbohydrate, low-GI diet.

The role and potential of sialic acid in human nutrition

Sialic acids are a family of nine-carbon acidic monosaccharides that occur naturally at the end of sugar chains attached to the surfaces of cells and soluble proteins. In the human body, the highest concentration of sialic acid (as N-acetylneuraminic acid) occurs in the brain where it participates as an integral part of ganglioside structure in synaptogenesis and neural transmission. Human milk also contains a high concentration of sialic acid attached to the terminal end of free oligosaccharides, but its metabolic fate and biological role are currently unknown. An important question is whether the sialic acid in human milk is a conditional nutrient and confers developmental advantages on breast-fed infants compared to those fed infant formula. In this review, we critically discuss the current state of knowledge of the biology and role of sialic acid in human milk and nervous tissue, and the link between sialic acid, breastfeeding and learning behaviour.

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.

Dietary sialic acid supplementation improves learning and memory in piglets

BACKGROUND

Sialic acid, a key component of both human milk oligosaccharides and neural tissues, may be a conditional nutrient during periods of rapid brain growth.

OBJECTIVE

We tested the hypothesis that variations in the sialic acid content of a formula milk would influence early learning behavior and gene expression of enzymes involved in sialic acid metabolism in piglets.

DESIGN

Piglets (n = 54) were allocated to 1 of 4 groups fed sow milk replacer supplemented with increasing amounts of sialic acid as casein glycomacropeptide for 35 d. Learning performance and memory were assessed with the use of easy and difficult visual cues in an 8-arm radial maze. Brain ganglioside and sialoprotein concentrations and mRNA expression of 2 learning-associated genes (ST8SIA4 and GNE) were measured.

RESULTS

In both tests, the supplemented groups learned in significantly fewer trials than did the control group, with a dose-response relation for the difficult task (P = 0.018) but not the easy task. In the hippocampus, significant dose-response relations were observed between amount of sialic acid supplementation and mRNA levels of ST8SIA4 (P = 0.002) and GNE (P = 0.004), corresponding with proportionate increases in protein-bound sialic acid concentrations in the frontal cortex.

CONCLUSIONS

Feeding a protein-bound source of sialic acid during early development enhanced learning and increased expression of 2 genes associated with learning in developing piglets. Sialic acid in mammalian milks could play a role in cognitive development.

Concentration and distribution of sialic acid in human milk and infant formulas

BACKGROUND

In animal studies, sialic acid supplementation is associated with increases of gangliosides in the brain and improved learning ability. Only limited data are available on the sialic acid content of human milk and infant formulas.

OBJECTIVE

We compared the concentrations of oligosaccharide-bound, protein-bound, and free sialic acid in milk from mothers of full-term and preterm infants and in a range of infant formulas.

DESIGN

The milk from 20 and 14 mothers of full-term and preterm infants (mean gestational age: 31 +/- 3 wk), respectively, was collected at 4 stages of lactation (colostrum, transition, 1 mo, and 3 mo) and compared with 21 different infant formulas.

RESULTS

Total sialic acid concentrations were highest in colostrum (x +/- SEM: 5.04 +/- 0.21 mmol/L in full term) and decreased by nearly 80% over the next 3 mo. Human milk from mothers of preterm infants contained 13-23% more sialic acid than did milk from mothers of full-term infants at 3 of the 4 lactation stages (P < 0.02). The sialic acid content of most formulas was <25% of that found in mature human milk (P < 0.01). Most of the sialic acid in the formulas ( approximately 70%) was bound to glycoproteins, whereas in human milk most sialic acid was bound to free oligosaccharides.

CONCLUSIONS

Human milk, including milk from mothers of preterm infants, is a rich source of oligosaccharide-bound sialic acid, which contrasts with the relatively small amounts found in infant formulas. The nutritional significance of sialic acid is presently unknown, but it is plausible that it is a conditional nutrient that contributes to sialic acid accretion in the brain.

Brain ganglioside and glycoprotein sialic acid in breastfed compared with formula-fed infants

BACKGROUND

The concentration of sialic acid in brain gangliosides and glycoproteins has been linked to learning ability in animal studies. Human milk is a rich source of sialic acid-containing oligosaccharides and is a potential source of exogenous sialic acid.

OBJECTIVE

The aim of the study was to compare the sialic acid concentration in the brain frontal cortex of breastfed and formula-fed infants.

DESIGN

Twenty-five samples of frontal cortex derived from infants who died of sudden infant death syndrome were analyzed. Twelve infants were breastfed, 10 infants were formula-fed, and 1 infant was mixed-fed; the feeding status of the remaining 2 infants was unknown. Ganglioside-bound and protein-bound sialic acid were determined by HPLC. Ganglioside ceramide fatty acids were also analyzed to determine the relation between sialic acid and long-chain polyunsaturated fatty acids.

RESULTS

After adjustment for sex with age at death as a covariate, ganglioside-bound and protein-bound sialic acid concentrations were 32% and 22% higher, respectively, in the frontal cortex gray matter of breastfed infants than in that of formula-fed infants (P < 0.01). Protein-bound sialic acid increased with age in both groups (P = 0.02). In breastfed but not in formula-fed infants, ganglioside-bound sialic acid correlated significantly with ganglioside ceramide docosahexaenoic acid and total n-3 fatty acids.

CONCLUSIONS

Higher brain ganglioside and glycoprotein sialic acid concentrations in infants fed human milk suggests increased synaptogenesis and differences in neurodevelopment.

Testing protein leverage in lean humans: a randomised controlled experimental study

A significant contributor to the rising rates of human obesity is an increase in energy intake. The ‘protein leverage hypothesis’ proposes that a dominant appetite for protein in conjunction with a decline in the ratio of protein to fat and carbohydrate in the diet drives excess energy intake and could therefore promote the development of obesity. Our aim was to test the ‘protein leverage hypothesis’ in lean humans by disguising the macronutrient composition of foods offered to subjects under ad libitum feeding conditions. Energy intakes and hunger ratings were measured for 22 lean subjects studied over three 4-day periods of in-house dietary manipulation. Subjects were restricted to fixed menus in random order comprising 28 foods designed to be similar in palatability, availability, variety and sensory quality and providing 10%, 15% or 25% energy as protein. Nutrient and energy intake was calculated as the product of the amount of each food eaten and its composition. Lowering the percent protein of the diet from 15% to 10% resulted in higher (+12±4.5%, p = 0.02) total energy intake, predominantly from savoury-flavoured foods available between meals. This increased energy intake was not sufficient to maintain protein intake constant, indicating that protein leverage is incomplete. Urinary urea on the 10% and 15% protein diets did not differ statistically, nor did they differ from habitual values prior to the study. In contrast, increasing protein from 15% to 25% did not alter energy intake. On the fourth day of the trial, however, there was a greater increase in the hunger score between 1–2 h after the 10% protein breakfast versus the 25% protein breakfast (1.6±0.4 vs 25%: 0.5±0.3, p = 0.005). In our study population a change in the nutritional environment that dilutes dietary protein with carbohydrate and fat promotes overconsumption, enhancing the risk for potential weight gain.

Dietary glycemic index: health implications

Weight loss can be achieved by any means of energy restriction, but the challenge is to achieve sustainable weight loss and prevent weight "creep" without increasing the risk of chronic disease. The modest success of low fat diets has prompted research on alternative dietary strategies, including high protein diets and low glycemic index (GI) diets. Conventional high carbohydrate diets, even when based on wholegrain foods, increase postprandial glycemia and insulinemia and may compromise weight control via mechanisms related to appetite stimulation, fuel partitioning, and metabolic rate. This paper makes the case for the benefits of low glycemic index diets over higher protein diets. Both strategies are associated with lower postprandial glycemia, and both are commonly labeled as "low glycemic load," but the long-term health effects are likely to be different. A large body of evidence, which now comprises observational prospective cohort studies, randomized controlled trials, and mechanistic experiments in animal models, provides robust support for low GI carbohydrate diets in the prevention of obesity, diabetes, and cardiovascular disease. Although lower carbohydrate, higher protein diets increase the rate of weight loss, cohort studies and meta-analyses of clinical trials suggest the potential for increased mortality.

The glycaemic index of potatoes: the effect of variety, cooking method and maturity

OBJECTIVE

The aim of this study was to determine the impact of variety, cooking method and maturity on the GI of potatoes, it was hypothesised that new potatoes may have a relatively lower GI.

DESIGN AND SUBJECTS

Ten healthy volunteers were recruited as subjects through advertising on the campus of the University of Sydney. Equal (50 g) carbohydrate portions of eight potato meals (three varieties, four cooking methods, two states of maturity) and two reference white bread meals were fed in random order to each of the subjects over a period of 10 weeks. Capillary blood samples were taken in the fasting state and then at 15, 30, 45, 60, 90 and 120 min from the start of each meal. Samples were analysed for plasma glucose concentrations and incremental areas under plasma glucose curves were calculated. The GI of the potato was calculated as the AUC of the potato expressed as a percentage of the individual's average AUC of the white bread. This was then multiplied by 0.7 to index the GI to glucose as the reference food.

RESULTS

GI values (mean +/- s.e.m.) ranged from 65+/-9 (canned new potatoes) to 10+/-15 (boiled Desiree potatoes), glucose = 100. No significant difference was found among the three varieties of potato tested (P = 0.38) or among the four different cooking methods (P = 0.55). The GI values of the canned new potato and boiled Desiree potato were significantly different (P = 0.047). The average size of the tuber was found to correlate with the GI (r = 0.83, P<0.05).

CONCLUSIONS

Potatoes, regardless of variety, cooking method and maturity, have exceptionally high GI values. New potatoes have relatively lower GI values which is attributed to differences in starch structure.

Glycemic index, postprandial glycemia and cardiovascular disease

PURPOSE OF REVIEW

Several lines of evidence indicate that exaggerated postprandial glycemia puts individuals without diabetes at greater risk of developing cardiovascular disease. In large, prospective observational studies, including meta-analyses, higher 120 min post-load blood glucose and glycated hemoglobin (a measure of average blood glucose level over time) independently predict cardiovascular mortality and morbidity in individuals without diabetes. These findings imply that the glycemic nature of dietary carbohydrates may also be relevant. We aim to provide a clearer perspective on how the glycemic impact of carbohydrates may modulate development of cardiovascular disease.

RECENT FINDINGS

In ecological studies, average dietary glycemic index (a measure of the postprandial glycemic potential of carbohydrates) and glycemic load (average glycemic index x amount of carbohydrate) predicts coronary infarct and cardiovascular disease risk factors, including HDL cholesterol, triglycerides and C-reactive protein. In short-term intervention studies of overweight and hyperlipidemic patients, low glycemic index diets lead to improvements in cardiovascular disease risk factors, including reduced LDL cholesterol and improved insulin sensitivity, as well as greater body fat loss on energy-restricted diets. Molecular studies indicate that physiological hyperglycemia induces overproduction of superoxide by the mitochondrial electron-transport chain, resulting in inflammatory responses and endothelial dysfunction.

SUMMARY

Taken together, the findings suggest that conventional high-carbohydrate diets with their high glycemic index may be suboptimal, particularly in insulin-resistant individuals. Because around one in four adults has impairments in postprandial glucose regulation, the glycemic potential of carbohydrates warrants further investigation in cardiovascular disease prevention.

Dietary glycemic index and the risk of age-related macular degeneration

BACKGROUND

Dietary factors are known risk factors for age-related macular degeneration (AMD) -- the leading cause of visual loss among persons aged > or =65 y. High-glycemic-index diets have been hypothesized as a risk factor for AMD, but prospective data are unavailable.

OBJECTIVE

The objective was to examine the association between dietary glycemic index and the 10-y incidence of AMD in the Blue Mountain Eye Study population.

DESIGN

This was a population-based cohort study with 3,654 participants (> or =49 y) examined at baseline (1992-1994); 2,335 patients were reexamined after 5 y and 1952 after 10 y. The Wisconsin System was used to grade 10-y incident early and late AMD from retinal photographs. A food-frequency questionnaire was used to collect dietary information at baseline, and an Australian database was used to calculate the mean glycemic index.

RESULTS

Over 10 y, 208 of 1,810 persons (cumulative incidence: 14.1%) developed early AMD. After age, smoking, other risk factors, and dietary constituents were adjusted for, a higher mean dietary glycemic index was associated with an increased 10-y risk of early AMD in a comparison of quartiles 1 and 4 [relative risk (RR): 1.77; 95% CI: 1.13, 2.78; P for trend = 0.03]. Conversely, a greater consumption of cereal fiber (RR: 0.68; 95% CI: 0.44, 1.04; P for trend = 0.05) and breads and cereals (predominantly lower glycemic index foods such as oatmeal) (RR: 0.67; 95% CI: 0.44, 1.02; P for trend = 0.03) was associated with a reduced risk of incident early AMD. No relation was observed with late AMD.

CONCLUSIONS

A high-glycemic-index diet is a risk factor for early AMD -- the recognized precursor of sight-threatening late AMD. Low-glycemic-index foods such as oatmeal may protect against early AMD.

High-glycemic index carbohydrate increases nuclear factor-kappaB activation in mononuclear cells of young, lean healthy subjects

BACKGROUND

High-glycemic index diets have been linked to greater risk of cardiovascular disease and type 2 diabetes. Postprandial glycemia within the normal range may promote oxidative stress and inflammatory processes underlying the development of disease.

OBJECTIVE

We explored acute differences in the activation of the inflammatory marker nuclear factor-kappaB after consumption of 2 carbohydrate meals matched for macronutrient and micronutrient composition but differing in glycemic index.

DESIGN

After an overnight fast, 10 young, lean healthy subjects were fed in random order 3 meals providing 50 g of available carbohydrate as glucose, white bread, or pasta. Venous blood samples were collected at 0, 1, 2, and 3 h, and nuclear proteins were extracted from mononuclear cells. Changes in nuclear factor-kappaB-p65 proteins were detected by Western blotting. Acute changes in other markers of oxidative stress (nitrotyrosine and soluble intercellular adhesion molecule-1) were also assessed.

RESULTS

The maximum increase in nuclear factor-kappaB activation was similar after the bread meal [mean (+/-SEM) area under the curve: 69 +/- 16% optical density x h] and the glucose challenge (75 +/- 9% optical density x h), but was 3 times higher than after the pasta meal (23 +/- 5% optical density x h) (P < 0.05). Similarly, changes in nitrotyrosine, but not soluble intercellular adhesion molecule-1, were higher after glucose and bread than after pasta (P = 0.01 at 2 h).

CONCLUSIONS

The findings suggest that high-normal physiologic increases in blood glucose after meals aggravate inflammatory processes in lean, young adults. This mechanism may help to explain relations between carbohydrates, glycemic index, and the risk of chronic disease.

Optimal dietary approaches for prevention of type 2 diabetes: a life-course perspective

In recent years, several alternative dietary approaches, including high-protein and low-glycaemic-load diets, have produced faster rates of weight loss than traditional low-fat, high-carbohydrate diets. These diets share an under-recognised unifying mechanism: the reduction of postprandial glycaemia and insulinaemia. Similarly, some food patterns and specific foods (potatoes, white bread, soft drinks) characterised by hyperglycaemia are associated with higher risk of adiposity and type 2 diabetes. Profound compensatory hyperinsulinaemia, exacerbated by overweight, occurs during critical periods of physiological insulin resistance such as pregnancy and puberty. The dramatic rise in gestational diabetes and type 2 diabetes in the young may therefore be traced to food patterns that exaggerate postprandial glycaemia and insulinaemia. The dietary strategy with the strongest evidence of being able to prevent type 2 diabetes is not the accepted low-fat, high-carbohydrate diet, but alternative dietary approaches that reduce postprandial glycaemia and insulinaemia without adversely affecting other risk factors.

Methodological challenges in the application of the glycemic index in epidemiological studies using data from the European Prospective Investigation into Cancer and Nutrition

Associations between the glycemic index (GI) or glycemic load (GL) and diseases are heterogeneous in epidemiological studies. Differences in assigning GI values to food items may contribute to this inconsistency. Our objective was to address methodological issues related to the use of current GI and GL values in epidemiological studies. We performed ecological comparison and correlation studies by calculating dietary GI and GL from country-specific dietary questionnaires (DQ) from 422,837 participants from 9 countries participating in the European Prospective Investigation into Cancer and Nutrition study and single standardized 24-h dietary recalls (24-HDR) obtained from a representative sample (n = 33,404) using mainly Foster Powell's international table as a reference source. Further, 2 inter-rater and 1 inter-method comparison were conducted, comparing DQ GI values assigned by independent groups with values linked by us. The ecological correlation between DQ and 24-HDR was good for GL (overall r = 0.76; P < 0.005) and moderate for GI (r = 0.57; P < 0.05). Mean GI/GL differences between DQ and 24-HDR were significant for most centers. GL but not GI from DQ was highly correlated with total carbohydrate (r = 0.98 and 0.15, respectively; P < 0.0001) and this was higher for starch (r = 0.72; P < 0.0001) than for sugars (r = 0.36; P < 0.0001). The inter-rater and inter-method variations were considerable for GI (weighted kappa coefficients of 0.49 and 0.65 for inter-rater and 0.25 for inter-method variation, respectively) but only mild for GL (weighted kappa coefficients > 0.80). A more consistent methodology to attribute GI values to foods and validated DQ is needed to derive meaningful GI/GL estimates for nutritional epidemiology.

Cocoa Powder Increases Postprandial Insulinemia in Lean Young Adults

We hypothesized that chocolate products elicit higher insulin responses than matched products with alternate flavoring. To test this, we used a within-subject, repeated-measures comparison of six pairs of foods, one flavored with chocolate (cocoa powder) and the other not. Healthy subjects (n = 10, 4 men, 6 women) tested each pair of foods. Postprandial glucose and insulin levels were determined at intervals over 2 h using standardized glycemic index (GI) methodology. The product categories were chocolate bars, cakes, breakfast cereals, ice creams, flavored milks and puddings. Although the GI did not differ within each pair, the insulin index (II) of the chocolate product was always higher, by a mean of 28%, than the alternate flavored product (P < 0.001). The greatest difference occurred within the flavored milk category in which the chocolate version elicited 45% greater insulinemia than the strawberry flavored milk (P = 0.021). Macronutrient composition (fat, protein, sugar, fiber or energy density) accounted for nearly all of the variation in GI among the foods, but did not explain differences in insulinemia. The presence of cocoa powder in foods leads to greater postprandial insulin secretion than alternate flavorings. Specific insulinogenic amino acids or greater cephalic phase insulin release may explain the findings.

Glycemic index and glycemic load of carbohydrates in the diabetes diet

Medical nutrition therapy is the first line of treatment for the prevention and management of type 2 diabetes and plays an essential part in the management of type 1 diabetes. Although traditionally advice was focused on carbohydrate quantification, it is now clear that both the amount and type of carbohydrate are important in predicting an individual's glycemic response to a meal. Diets based on carbohydrate foods that are more slowly digested, absorbed, and metabolized (i.e., low glycemic index [GI] diets) have been associated with a reduced risk of type 2 diabetes and cardiovascular disease, whereas intervention studies have shown improvements in insulin sensitivity and glycated hemoglobin concentrations in people with diabetes following a low GI diet. Research also suggests that low GI diets may assist with weight management through effects on satiety and fuel partitioning. These findings, together with the fact that there are no demonstrated negative effects of a low GI diet, suggest that the GI should be an important consideration in the dietary management and prevention of diabetes.

Carbohydrate nutrition and inflammatory disease mortality in older adults

BACKGROUND

Several studies suggest that carbohydrate nutrition is related to oxidative stress and inflammatory markers.

OBJECTIVE

We examined whether dietary glycemic index (GI), dietary fiber, and carbohydrate-containing food groups were associated with the mortality attributable to noncardiovascular, noncancer inflammatory disease in an older Australian cohort.

DESIGN

Analysis included 1490 postmenopausal women and 1245 men aged ge 49 y at baseline (1992-1994) from a population-based cohort who completed a validated food-frequency questionnaire. Cox proportional hazards ratios were calculated both for death from diseases in which inflammation or oxidative stress was a predominant contributor and for cardiovascular mortality.

RESULTS

Over a 13-y period, 84 women and 86 men died of inflammatory diseases. Women in the highest GI tertile had a 2.9-fold increased risk of inflammatory death compared with women in the lowest GI tertile [multivariate hazard ratio in energy-adjusted tertile 3 (tertile 1 as reference): 2.89; 95% CI: 1.52, 5.51; P for trend: 0.0006, adjusted for age, smoking, diabetes, and alcohol and fiber consumption]. Increasing intakes of foods high in refined sugars or refined starches (P = 0.04) and decreasing intakes of bread and cereals (P = 0.008) or vegetables other than potatoes (P = 0.007) also independently predicted a greater risk, with subjects' GI partly explaining these associations. In men, only an increased consumption of fruit fiber (P = 0.005) and fruit (P = 0.04) conferred an independent decrease in risk of inflammatory death. No associations were observed with cardiovascular mortality.

CONCLUSION

These data provide new epidemiologic evidence of a potentially important link between GI and inflammatory disease mortality among older women.

The Australian paradox: a substantial decline in sugars intake over the same timeframe that overweight and obesity have increased

Ecological research from the USA has demonstrated a positive relationship between sugars consumption and prevalence of obesity; however, the relationship in other nations is not well described. The aim of this study was to analyze the trends in obesity and sugar consumption in Australia over the past 30 years and to compare and contrast obesity trends and sugar consumption patterns in Australia with the UK and USA. Data on consumption of sugar in Australia, the UK and USA were obtained from the Food and Agriculture Organization for the years 1980-2003. The prevalence of obesity has increased 3 fold in Australians since 1980. In Australia, the UK and USA, per capita consumption of refined sucrose decreased by 23%, 10% and 20% respectively from 1980 to 2003. When all sources of nutritive sweeteners, including high fructose corn syrups, were considered, per capita consumption decreased in Australia (-16%) and the UK (-5%), but increased in the USA (+23%). In Australia, there was a reduction in sales of nutritively sweetened beverages by 64 million liters from 2002 to 2006 and a reduction in percentage of children consuming sugar-sweetened beverages between 1995 and 2007. The findings confirm an "Australian Paradox"--a substantial decline in refined sugars intake over the same timeframe that obesity has increased. The implication is that efforts to reduce sugar intake may reduce consumption but may not reduce the prevalence of obesity.

Food intake, postprandial glucose, insulin and subjective satiety responses to three different bread-based test meals

The effect of bread consumption on overall food intake is poorly understood. The aim of this study was to measure postprandial food intake after a set breakfast containing three different breads. Ten males and 10 females aged 20.1-44.8 years, BMI 18.4-24.8 kg/m(2), consumed two slices of White Bread, Bürgen Wholemeal and Seeds Bread or Lupin Bread (all 1300 kJ) with 10 g margarine and 30 g strawberry jam. Fullness and hunger responses and were measured before and during the test breakfasts. Glucose and insulin responses (incremental area under each two-hour curve (iAUC)) were calculated. Food intake was measured and energy and nutrient intake determined at a buffet meal two hours later. Subjects consumed significantly less energy after the Bürgen Bread meal compared to the White Bread meal (2548 ± 218 vs. 3040±328kJ, Bürgen Bread vs. White Bread, P<0.05). There were higher fullness responses for the Lupin Bread (P<0.01), and the Bürgen Bread (P<0.05) compared with the White Bread. Lupin Bread and Bürgen Bread produced smaller postprandial glucose responses (79 ± 7, 74 ± 4, 120 ± 10 mmol/L min iAUC, Lupin, Bürgen and White Bread respectively, P<0.01). Differences in insulin responses were also observed (6145 ± 1048, 6471 ± 976, 9674 ± 1431 pmol/L min iAUC, Lupin, Bürgen and White Bread respectively, P<0.01). Equal-energy portions of three different commercially available breads differed in their short-term satiation capacity. Further studies are needed to demonstrate any potential benefit for weight management.