Evidence that carbohydrate-to-fat ratio and taste, but not energy density or NOVA level of processing, are determinants of food liking and food reward.

This virtual (online) study tested the common but largely untested assumptions that food energy density, level of processing (NOVA categories), and carbohydrate-to-fat (CF) ratio are key determinants of food reward. Individual participants (224 women and men, mean age 35 y, 53% with healthy weight, 43% with overweight or obesity) were randomised to one of three, within-subjects, study arms: energy density (32 foods), or level of processing (24 foods), or CF ratio (24 foods). They rated the foods for taste pleasantness (liking), desire to eat (food reward), and sweetness, saltiness, and flavour intensity (for analysis averaged as taste intensity). Against our hypotheses, there was not a positive relationship between liking or food reward and either energy density or level of processing. As hypothesised, foods combining more equal energy amounts of carbohydrate and fat (combo foods), and foods tasting more intense, scored higher on both liking and food reward. Further results were that CF ratio, taste intensity, and food fibre content (negatively), independent of energy density, accounted for 56% and 43% of the variance in liking and food reward, respectively. We interpret the results for CF ratio and fibre in terms of food energy-to-satiety ratio (ESR), where ESR for combo foods is high, and ESR for high-fibre foods is low. We suggest that the metric of ESR should be considered when designing future studies of effects of food composition on food reward, preference, and intake.

The association of dietary animal and plant protein with putative risk markers of colorectal cancer in overweight pre-diabetic individuals during a weight-reducing programme: a PREVIEW sub-study.

PURPOSE: Diets with increased protein content are popular strategies for body weight regulation, but the effect of such diets for the colonic luminal environment is unclear. We aimed to investigate the associations between putative colorectal cancer-related markers and total protein intake, plant and animal proteins, and protein from red and processed meat in pre-diabetic adults (> 25 years). METHODS: Analyses were based on clinical and dietary assessments at baseline and after 1 year of intervention. Protein intake was assessed from 4-day dietary records. Putative colorectal cancer-related markers identified from 24-h faecal samples collected over three consecutive days were: concentration of short-chain fatty acids, phenols, ammonia, and pH. RESULTS: In total, 79 participants were included in the analyses. We found a positive association between change in total protein intake (slope: 74.72 ± 28.84 µmol per g faeces/E%, p = 0.01), including animal protein intake (slope: 87.63 ± 32.04 µmol per g faeces/E%, p = 0.009), and change in faecal ammonia concentration. For change in ammonia, there was a dose-response trend from the most negative (lowest tertile) to the most positive (highest tertile) association (p = 0.01): in the high tertile, a change in intake of red meat was positively associated with an increase in ammonia excretion (slope: 2.0 ± 0.5 µmol per g faeces/g/day, p < 0.001), whereas no such association was found in the low and medium tertile groups. CONCLUSION: Increases in total and animal protein intakes were associated with higher excretion of ammonia in faeces after 1 year in overweight pre-diabetic adults undertaking a weight-loss intervention. An increase in total or relative protein intake, or in the ratio of animal to plant protein, was not associated with an increase in faeces of any of the other putative colorectal cancer risk markers. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01777893.

Glycaemic and insulin index of four common German breads.

BACKGROUND/OBJECTIVES: German-style breads are recommended as a lower glycaemic index (GI) alternative, yet little data is available. Our aim was to test the GI and insulin index (II) of four breads and rolls commonly consumed in Germany. SUBJECTS/METHODS: Four German bread products were tested for their GI and II in 12 healthy subjects according to the International Standard Organization guidelines. RESULTS: Only the wholemeal rye bread with visible intact grains and sunflower seeds was identified as low GI (GI=55). Both the wholemeal spelt wheat (GI=63) and the rye wheat sourdough bread (GI=62) were classified as medium GI, whereas soft pretzel was high GI (GI=80, P<0.05 compared with other products). The II of soft pretzels (II=102) was also highest and differed significantly from wholemeal rye (II=70) and rye sourdough bread (II=72) but not from wholemeal spelt wheat (II=77). CONCLUSIONS: Contrary to popular belief, these German-style breads are medium to high GI, with the exception of the rye bread with intact grains and seeds. The results highlight the need to test, rather than 'guestimate', the GI of local products, and develop a broader range of low-GI breads.

Hypoglycaemia in cystic fibrosis in the absence of diabetes: A systematic review.

BACKGROUND: Hypoglycaemia in CF in the absence of diabetes or glucose lowering therapies is a phenomenon that is receiving growing attention in the literature. These episodes are sometimes symptomatic and likely have variable aetiologies. Our first aim was to conduct a systematic review of the literature to determine what is known about hypoglycaemia in CF. Our second aim was to assess evidence based guidelines for management strategies. METHODS: A comprehensive search of databases and guideline compiler entities was performed. Inclusion criteria were primary research articles and evidence based guidelines that referred to hypoglycaemia in CF in the absence of insulin treatment or other glucose lowering therapies. RESULTS: A total of 11 studies (four manuscripts and seven abstracts) and five evidence-based guidelines met the inclusion criteria. Prevalence rates of hypoglycaemia unrelated to diabetes varied between studies (7-69%). Hypoglycaemia was diagnosed during oral glucose tolerance testing or continuous glucose monitoring (CGM). Associations between hypoglycaemia and clinical parameters of BMI, lung function, liver disease and pancreatic insufficiency were measured in some studies. There was no unifying definition of hypoglycaemia in the absence of diabetes. Only two evidence based guidelines reported possible management strategies. CONCLUSION: The systematic review found limited data on this clinical problem and supports the need for high quality methodological studies that are able to describe the experience and the aetiology(ies) of hypoglycaemia in CF.

Assigning glycemic index to foods in a recent Australian food composition database.

This paper describes the compilation of a special edition of the AUSNUT2011-2013 food composition database that includes glycemic index (GI) values. A 6-step, systematic methodology was used to assign GI to 5644 foods included in AUSNUT2011-2013. A total of 1752 (31%) foods were assigned a GI of 0 owing to low carbohydrate content; 363 (6%) had a direct match in 1 of the 4 data tables used; 1738 (31%) were assigned the GI of a 'closely related' food item; 1526 (27%) were assigned the weighted mean GI of ingredients; 205 (4%) were assigned the median GI of their corresponding food subgroup; 49 (<1%) were assigned a GI of 0 because they were not a significant source of carbohydrate in typical diets; and 5 (<1%) were assigned a default GI. We propose that this database should be used for all future Australian GI research until a subsequent version/update is compiled.

The effect of maternal and post-weaning low and high glycaemic index diets on glucose tolerance, fat deposition and hepatic function in rat offspring.

Clinical studies have reported beneficial effects of a maternal low glycaemic index (GI) diet on pregnancy and neonatal outcomes, but the impact of the diet on the offspring in later life, and the mechanisms underlying these effects, remain unclear. In this study, Albino Wistar rats were fed either a low GI (n=14) or high GI (n=14) diet during pregnancy and lactation and their offspring weaned onto either the low or high GI diet. Low GI dams had better glucose tolerance (AUC[glucose], 1322±55 v. 1523±72 mmol min/l, P<0.05) and a lower proportion of visceral fat (19.0±2.9 v. 21.7±3.8% of total body fat, P<0.05) compared to high GI dams. Female offspring of low GI dams had lower visceral adiposity (0.45±0.03 v. 0.53±0.03% body weight, P<0.05) and higher glucose tolerance (AUC[glucose], 1243±29 v. 1351±39 mmol min/l, P<0.05) at weaning, as well as lower hepatic PI3K-p85 mRNA at 12 weeks of age. No differences in glucose tolerance or hepatic gene expression were observed in male offspring, but the male low GI offspring did have reduced hepatic lipid content at weaning. These findings suggest that consuming a low GI diet during pregnancy and lactation can improve glucose tolerance and reduce visceral adiposity in the female offspring at weaning, and may potentially produce long-term reductions in the hepatic lipogenic capacity of these offspring.

Glycemic index, glycemic load and glycemic response: An International Scientific Consensus Summit from the International Carbohydrate Quality Consortium (ICQC).

BACKGROUND AND AIMS: The positive and negative health effects of dietary carbohydrates are of interest to both researchers and consumers. METHODS: International experts on carbohydrate research held a scientific summit in Stresa, Italy, in June 2013 to discuss controversies surrounding the utility of the glycemic index (GI), glycemic load (GL) and glycemic response (GR). RESULTS: The outcome was a scientific consensus statement which recognized the importance of postprandial glycemia in overall health, and the GI as a valid and reproducible method of classifying carbohydrate foods for this purpose. There was consensus that diets low in GI and GL were relevant to the prevention and management of diabetes and coronary heart disease, and probably obesity. Moderate to weak associations were observed for selected cancers. The group affirmed that diets low in GI and GL should always be considered in the context of diets otherwise understood as healthy, complementing additional ways of characterizing carbohydrate foods, such as fiber and whole grain content. Diets of low GI and GL were considered particularly important in individuals with insulin resistance. CONCLUSIONS: Given the high prevalence of diabetes and pre-diabetes worldwide and the consistency of the scientific evidence reviewed, the expert panel confirmed an urgent need to communicate information on GI and GL to the general public and health professionals, through channels such as national dietary guidelines, food composition tables and food labels.

Effects of human milk and formula on postprandial glycaemia and insulinaemia.

BACKGROUND/OBJECTIVES: Consumption of formula in place of human milk may produce differences in postprandial glycaemia and insulinaemia that contribute to metabolic programming in the first year of life. The objective of the current study was to determine glycaemic and insulinaemic responses to human milk compared with a typical commercial formula, and then compare 11 other formulas. SUBJECTS/METHODS: On separate mornings in random order, 10 healthy breastfeeding mothers consumed 25 g available carbohydrate portions of their own milk, a formula and reference food (25 g glucose on two occasions). In the second study, 10 different healthy subjects consumed 25 g available carbohydrate portions of 11 different commercial formulas and three reference foods (25 g glucose on three occasions). Fingerpick blood samples were taken at regular intervals over 2 h, and the glycaemic index (GI) and insulin index determined according to a standardised protocol. RESULTS: There were no significant differences in postprandial glycaemia or insulinaemia after human milk vs a typical formula (P = 0.3). Both produced a low GI (mean ± s.e.m.: 38 ± 7 vs 34 ± 7, respectively) and high insulin index (87 ± 14 vs 94 ± 16). The GI and insulin indices of the other formulas ranged from 18 ± 3 to 67 ± 6 and 53 ± 9 to 209 ± 33, respectively. CONCLUSIONS: Human milk and a typical formula elicit similar postprandial glycaemic and insulinaemic responses, but there is a wide range of responses to other formulas.

A systematic methodology to estimate added sugar content of foods.

BACKGROUND/OBJECTIVES: The effect of added sugar on health is a topical area of research. However, there is currently no analytical or other method to easily distinguish between added sugars and naturally occurring sugars in foods. This study aimed to develop a systematic methodology to estimate added sugar values on the basis of analytical data and ingredients of foods. SUBJECTS/METHODS: A 10-step, stepwise protocol was developed, starting with objective measures (six steps) and followed by more subjective estimation (four steps) if insufficient objective data are available. The method developed was applied to an Australian food composition database (AUSNUT2007) as an example. RESULTS: Out of the 3874 foods available in AUSNUT2007, 2977 foods (77%) were assigned an estimated value on the basis of objective measures (steps 1-6), and 897 (23%) were assigned a subjectively estimated value (steps 7-10). Repeatability analysis showed good repeatability for estimated values in this method. CONCLUSIONS: We propose that this method can be considered as a standardised approach for the estimation of added sugar content of foods to improve cross-study comparison.

Estimating insulin demand for protein-containing foods using the food insulin index.

BACKGROUND/OBJECTIVE: The Food Insulin Index (FII) is a novel algorithm for ranking foods on the basis of insulin responses in healthy subjects relative to an isoenergetic reference food. Our aim was to compare postprandial glycemic responses in adults with type 1 diabetes who used both carbohydrate counting and the FII algorithm to estimate the insulin dosage for a variety of protein-containing foods. SUBJECTS/METHODS: A total of 11 adults on insulin pump therapy consumed six individual foods (steak, battered fish, poached eggs, low-fat yoghurt, baked beans and peanuts) on two occasions in random order, with the insulin dose determined once by the FII algorithm and once with carbohydrate counting. Postprandial glycemia was measured in capillary blood glucose samples at 15-30 min intervals over 3 h. Researchers and participants were blinded to treatment. RESULTS: Compared with carbohydrate counting, the FII algorithm significantly reduced the mean blood glucose level (5.7±0.2 vs 6.5±0.2 mmol/l, P=0.003) and the mean change in blood glucose level (-0.7±0.2 vs 0.1±0.2 mmol/l, P=0.001). Peak blood glucose was reached earlier using the FII algorithm than using carbohydrate counting (34±5 vs 56±7 min, P=0.007). The risk of hypoglycemia was similar in both treatments (48% vs 33% for FII vs carbohydrate counting, respectively, P=0.155). CONCLUSIONS: In adults with type 1 diabetes, compared with carbohydrate counting, the novel FII algorithm improved postprandial hyperglycemia after consumption of protein-containing foods.

Prospective associations of dietary insulin demand, glycemic index, and glycemic load during puberty with body composition in young adulthood.

BACKGROUND: Puberty is a so-called critical period for overweight development and is characterized by physiological insulin resistance during mid-puberty. This study addressed the hypothesis that habitual consumption of a diet inducing higher levels of postprandial glycemia or insulinemia during puberty may have an unfavorable effect on the body composition in young adulthood. METHODS: Multivariate regression analysis was performed on 262 participants of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study with at least two 3-day weighed dietary records during puberty (baseline: girls 9-14 years; boys 10-15 years) and anthropometric measurements in young adulthood (18-25 years). A published dietary glycemic index was assigned to each carbohydrate-containing food. Similarly, each food was assigned a food insulin index (insulinemic response to a 1 MJ portion of food relative to 1 MJ of glucose) using 121 values measured at Sydney University. RESULTS: Dietary glycemic index or glycemic load during puberty was not related to body composition in young adulthood. In contrast, a higher dietary insulin index and a higher dietary insulin load during puberty were associated with higher levels of percentage of body fat (%BF) in young adulthood, even after adjustment for early life, socioeconomic and nutritional factors; %BF in energy-adjusted tertiles of dietary insulin index were 22.9 (95% confidence intervals (CI): 21.6, 24.1), 24.5 (23.2, 25.7), 24.7 (23.5, 25.9) %, P (for trend)=0.01; %BF in energy-adjusted tertiles of dietary insulin load were 22.8 (95% CI: 21.5, 24.0), 24.5 (23.2, 25.7), 24.8 (23.6, 26.0) %, P (for trend)=0.01. Adjustment for baseline %BF attenuated these relationships (P (for trend)=0.1 and=0.08, respectively). Dietary insulin demand was not related to body mass index. CONCLUSION: This study suggests a prospective adverse influence of dietary insulin demand during puberty on %BF in young adulthood. Postprandial increases in insulinemia rather than increases in glycemia appear to be implicated in an unfavorable development of body composition.

Dietary glycemic index, glycemic load, insulin index, fiber and whole-grain intake in relation to risk of prostate cancer.

OBJECTIVE: Insulin may play a role in prostate cancer tumorigenesis. Postprandial blood glucose and insulin responses of foods depend importantly on the carbohydrate quality and quantity, represented by glycemic index (GI), glycemic load (GL), fiber and whole-grain content, but are also influenced by intake of protein and other characteristics. The recently developed insulin index (II) quantifies the postprandial insulin secretion, also taking into account these additional characteristics. METHODS: We investigated the association between dietary GI, GL, II, fiber, and whole grains and risk of total prostate cancer (n = 5,112) and subgroups of prostate cancer as defined by stage or grade in 49,934 male participants of the Health Professionals Follow-up Study. Multivariate adjusted hazard ratios (HR) and 95% confidence intervals (95% CI) were estimated using Cox proportional hazards regression. RESULTS: Dietary GI, GL, II, or fiber was not associated with risk of total or subgroups of prostate cancer. We observed a positive association between dietary intake of whole grains and total prostate cancer (HR highest versus lowest quintile 1.13, 95% CI 1.03-1.24), which was attenuated after restriction to PSA-screened participants (HR 1.03, 95% CI 0.91-1.17). CONCLUSIONS: These results suggest that long-term exposure to a diet with a high insulin response does not affect prostate cancer incidence.

Effects of PGX, a novel functional fibre, on acute and delayed postprandial glycaemia.

BACKGROUND: Viscous fibre in food has established health benefits, but few functional fibre preparations are both effective and palatable. Our objective was to determine the most effective dose, formulation and timing of consumption of a novel fibre supplement (PolyGlycopleX (PGX)) in reducing postprandial glycaemia. SUBJECTS/METHODS: Three trials were undertaken, each with 10 subjects (8M and 8F; age 24.4 ± 2.6 years). Granular supplement was tested at four doses (0, 2.5, 5.0 and 7.5 g) with breakfast (study 1). Granular and capsule forms of the supplement were given in a single dose (5 g for granules and 4.5 g in capsules) at -60, -45, -30, -15 and 0 before, and +15 min after a bread meal (study 2). Capsules at increasing doses (1.5, 3, 4.5 and 6 g) were consumed with the evening meal to determine effects on glucose tolerance at breakfast (study 3). Incremental area under the blood glucose curve was determined. RESULTS: Granular PGX at breakfast time at doses of 2.5, 5 and 7.5 g reduced the incremental area under the curve by up to 50% in a linear dose-response fashion (P<0.001). The granular form of PGX (5 g), but not the capsules, reduced glycaemia by up to 28% when consumed from -45 to +15 min (P<0.001). Capsules containing 3, 4.5 and 6 g PGX consumed with the evening meal reduced glycaemia at breakfast by up to 28% (P<0.001). CONCLUSIONS: PGX has biologically important, dose-related effects on acute and delayed (second meal) postprandial glycaemia.

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.

Dietary glycemic index influences lipid oxidation but not muscle or liver glycogen oxidation during exercise.

The glycemic index (GI) of dietary carbohydrates influences glycogen storage in skeletal muscle and circulating nonesterified fatty acid (NEFA) concentrations. We hypothesized that diets differing only in GI would alter intramuscular lipid oxidation and glycogen usage in skeletal muscle and liver during subsequent exercise. Endurance-trained individuals (n = 9) cycled for 90 min at 70% Vo(2peak) and then consumed either high- or low-GI meals over the following 12 h. The following day after an overnight fast, the 90-min cycle was repeated. (1)H and (13)C magnetic resonance spectroscopy was used before and after exercise to assess intramuscular lipid and glycogen content of the vastus muscle group and liver. Blood and expired air samples were collected at 15-min intervals throughout exercise. NEFA availability was reduced during exercise in the high- compared with the low-GI trial (area under curve 44.5 +/- 6.0 vs. 38.4 +/- 7.30 mM/h, P < 0.05). Exercise elicited an approximately 55% greater reduction in intramyocellular triglyceride (IMCL) in the high- vs. low-GI trial (1.6 +/- 0.2 vs. 1.0 +/- 0.3 mmol/kg wet wt, P < 0.05). There was no difference in the exercise-induced reduction of the glycogen pool in skeletal muscle (76 +/- 8 vs. 68 +/- 5 mM) or in liver (65 +/- 8 vs. 71 +/- 4 mM) between the low- and high-GI trials, respectively. High-GI recovery diets reduce NEFA availability and increase reliance on IMCL during moderate-intensity exercise. Skeletal muscle and liver glycogen storage or usage are not affected by the GI of an acute recovery diet.

Effect of the glycemic index of carbohydrates on day-long (10 h) profiles of plasma glucose, insulin, cholecystokinin and ghrelin.

BACKGROUND: Low glycemic index (GI) carbohydrates have been linked to increased satiety. The drive to eat may be mediated by postprandial changes in glucose, insulin and gut peptides. OBJECTIVE: To investigate the effect of a low and a high GI diet on day-long (10 h) blood concentrations of glucose, insulin, cholecystokinin (CCK) and ghrelin (GHR). DESIGN: Subjects (n=12) consumed a high and a low GI diet in a randomized, crossover design, consisting of four meals that were matched for macronutrients and fibre, and differed only in carbohydrate quality (GI). Blood was sampled every 30-60 min and assayed for glucose, insulin, CCK and GHR. RESULTS: The high GI diet resulted in significantly higher glucose and insulin mean incremental areas under the curve (IAUC, P=0.027 and P=0.001 respectively). CCK concentration was 59% higher during the first 7 h of the low GI diet (394+/-95 pmol/l min) vs the high GI diet (163+/-38 pmol/l min, P=0.046), but there was no difference over 10 h (P=0.224). GHR concentration was inversely correlated with insulin concentration (Pearson correlation -0.48, P=0.007), but did not differ significantly between the low and high GI diets. CONCLUSIONS: Mixed meals of lower GI are associated with lower day-long concentrations of glucose and insulin, and higher CCK after breakfast, morning tea and lunch. This metabolic profile could mediate differences in satiety and hunger seen in some, but not all, studies.

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.

Physiological validation of the concept of glycemic load in lean young adults.

Dietary glycemic load, the mathematical product of the glycemic index (GI) of a food and its carbohydrate content, has been proposed as an indicator of the glucose response and insulin demand induced by a serving of food. To validate this concept in vivo, we tested the hypotheses that 1). portions of different foods with the same glycemic load produce similar glycemic responses; and 2). stepwise increases in glycemic load for a range of foods produce proportional increases in glycemia and insulinemia. In the first study, 10 healthy subjects consumed 10 different foods in random order in amounts calculated to have the same glycemic load as one slice of white bread. Capillary blood samples were taken at regular intervals over the next 2 h. The glycemic response as determined by area under the curve was not different from that of white bread for nine foods. However, lentils produced lower than predicted responses (P < 0.05). In the second study, another group of subjects was tested to determine the effects of increasing glycemic load using a balanced 5 x 5 Greco-Latin square design balanced for four variables: subject, dose, food and order. Two sets of five foods were consumed at five different glycemic loads (doses) equivalent to one, two, three, four and six slices of bread. Stepwise increases in glycemic load produced significant and predictable increases in both glycemia (P < 0.001) and insulinemia (P < 0.001). These findings support the concept of dietary glycemic load as a measure of overall glycemic response and insulin demand.