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.

Effect of baking process on postprandial metabolic consequences: randomized trials in normal and type 2 diabetic subjects.

OBJECTIVE: To determine the impact of the form, fibre content, baking and processing on the glycaemic, insulinaemic and lipidaemic responses of different French breads. DESIGN AND SUBJECTS: First study: Nine healthy subjects were randomized to consume in a crossover design one of six kinds of French bread (each containing 50 g available carbohydrate): classic baguette, traditional baguette, loaf of wholemeal bread (WM-B), loaf of bread fermented with yeast or with leaven, a sandwich and a glucose challenge as reference. RESULTS: The glycaemic index (GI) values ranged from 57+/-9% (mean+/-s.e.m.), for the traditional baguette, to 85+/-27% for the WM-B. No significant difference was found among the different tested bread. The insulinaemic index (II), however, of the traditional baguette and of the bread fermented with leaven were lower than the other breads (analysis of variance: P<0.01). Postprandial plasma triglycerides showed similar profiles. The traditional baguette tended to decrease postprandial free fatty acids compared to levels after the classic baguette. RESULTS: The GI of the traditional baguette was lower than that of the classic baguette (n=8, venous blood: 70+/-4 vs 75+/-4, P=0.002; capillary blood: 69+/-5 vs 83+/-6, P=0.028, respectively). CONCLUSIONS: Some varieties of French bread (the TB) have lower II, in healthy subjects, and lower GI, in type 2 diabetic subjects, than that of the other varieties. These results might be due to bread processing difference rather than fibre content. SPONSORSHIPS: Supported by grants from the National French Milling Association.

Moderate intake of n-3 fatty acids for 2 months has no detrimental effect on glucose metabolism and could ameliorate the lipid profile in type 2 diabetic men. Results of a controlled study.

OBJECTIVE: To evaluate the effect of a moderate dose of fish oil on glycemic control and in vivo insulin action in type 2 diabetic men with elevated plasma triacylglycerols and to determine the effect of the same treatment on gene expression of GLUT4, lipoprotein lipase (LPL), and hormone-sensitive lipase (HSL) in the abdominal adipose tissue. RESEARCH DESIGN AND METHODS: A total of 12 type 2 diabetic men were randomly allocated to 2 months of 6 g daily of either fish oil or sunflower oil, separated by a 2-month washout interval, in a double-blind crossover design. RESULTS: For glucose metabolism, 2 months of fish oil supplementation compared with sunflower oil led to similar fasting plasma insulin, glucose, and HbA1c. Basal hepatic glucose production did not increase after fish oil. There was no difference in insulin suppression of hepatic glucose production nor in insulin stimulation of whole-body glucose disposal measured by the euglycemic-hyperinsulinemic clamp. Fish oil did not ameliorate the low mRNA level of GLUT4 in adipose tissue of these patients. For lipid profile, fish oil lowered plasma triacylglycerol more than sunflower oil (P < 0.05) and tended to increase the amount of mRNA of both LPL and HSL in adipose tissue. CONCLUSIONS: A moderate dose of fish oil did not lead to deleterious effects on glycemic control or whole-body insulin sensitivity in type 2 diabetic men, with preserved triacylglycerol-lowering capacities.

Lack of detectable deleterious effects on metabolic control of daily fructose ingestion for 2 mo in NIDDM patients.

The effects of a daily intake of 30 g fructose on blood glucose regulation, erythrocyte insulin receptors, and lipid metabolism have been studied in type II (non-insulin-dependent) diabetic subjects. Eight well-controlled patients received, in a randomly assigned crossover design over two 2-mo study periods, 30 g of fructose in exchange for an isocaloric amount of starch. Fructose could be taken at any time during the day as part of the 1400-1600 kcal allowed diet (50% carbohydrate, 30% fat, 20% protein). No significant difference was observed concerning body weight, HbA1c, fasting plasma glucose, fasting plasma insulin, uric acid, total cholesterol, high-density lipoprotein cholesterol, and triglycerides, nor was there any change in insulin binding to erythrocytes between the fructose and the control starch period. However, the mean plasma triglyceride levels after the fructose period, although still in the normal range, were significantly higher than baseline values (P less than .05). We conclude that moderate amounts of fructose incorporated into the diet of well-controlled type II diabetic subjects have no significant deleterious effect on glycemic control, insulin receptors of erythrocytes, or lipid metabolism.

Relative sweetness of fructose compared with sucrose in healthy and diabetic subjects.

Fructose is credited with some advantages over sucrose: it causes less of an increment in plasma glucose and insulin response, and the taste is sweeter. We reevaluated the latter property with a new methodology (the "up and down" method adapted from Dixon) in 33 healthy subjects, 17 insulin-dependent diabetes mellitus (IDDM) patients, and 12 non-insulin-dependent diabetes mellitus (NIDDM) patients. Sweetening potency was determined over 2-3 test sessions in each subject. Results are expressed in percent as the relative sweetness (R) of fructose (F) over sucrose (S), taken as reference. In the first set of experiments, with a 30-g/L sucrose-water solution at pH 7, we found that R values were similar for healthy subjects (102 +/- 8%) and diabetic subjects (106 +/- 7%) (P less than .05). No significant difference between IDDM and NIDDM patients was observed. In a second set of experiments, performed in healthy subjects only, R was increased in acid water (114%; P less than .01), in lemon juice (136%; P less than .001), in water at 2 degrees C (130%; P less than .001), and in coffee at 2 degrees C (120%; P less than .02); mean values were decreased in grapefruit juice (77%; P less than .001), in water at 43 degrees C (88%; P less than .01), and in coffee at 53 degrees C (87%; P less than .001). We found that the test methodology had a very satisfactory intrasubject reproducibility (coefficient of variation [C.V.] less than 8%) but a very wide intersubject variability (C.V. congruent to 32%).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin and glycemic responses in healthy humans to native starches processed in different ways: correlation with in vitro alpha-amylase hydrolysis.

The aim of the study was to elucidate how extracted starches submitted to food processing (or not) can influence plasma insulin and glucose responses in healthy subjects. Native starches from wheat, manihot, smooth peas, or mung beans were tested either raw, as starch gels (boiled and cooled), or cooked and cooled after a preliminary industrial processing: extrusion cooking for wheat, tapioca for manihot, and noodles for mung beans. Eighteen healthy subjects randomly assigned received three different starches under one form of conditioning. All products were submitted to in vitro alpha-amylolysis. Raw manihot starch produced the lowest (p less than 0.05) metabolic responses. Cooking significantly (p less than 0.01) increased plasma responses. However, cooked mung bean noodles gave metabolic responses similar to those of raw products. Close correlations were found between percentages of in vitro starch hydrolysis at 30 min and mean areas under the glycemic curves and the insulinemic curves (r = 0.95, p less than 0.001).

Chronic consumption of fresh but not heated yogurt improves breath-hydrogen status and short-chain fatty acid profiles: a controlled study in healthy men with or without lactose maldigestion.

BACKGROUND: Ingestion of fermented dairy products induces changes in the equilibrium and metabolism of the intestinal microflora and may thus have beneficial effects on the host. OBJECTIVE: We compared the effects of chronic consumption of yogurt with (fresh) or without (heated) live bacterial cultures (Lactobacillus bulgaricus and Streptococcus thermophilus) on plasma glucose, insulin, triacylglycerols, cholesterol, fatty acids, and short-chain fatty acids. DESIGN: Two groups of 12 healthy men with or without lactose malabsorption were selected with use of a breath-hydrogen test after a 30-g lactose load. Subjects were randomly assigned in a crossover design to 500 g/d of either fresh or heated yogurt for 2 periods of 15 d each, separated by a 15-d washout interval. RESULTS: Chronic consumption of fresh or heated yogurt had no detrimental effects on plasma glucose, insulin, or fatty acid areas under the curve in response to acute ingestion of 500 g yogurt in healthy men with or without lactose malabsorption. There were also no detectable changes in fasting plasma glucose, insulin, fatty acid, triacylglycerol, or cholesterol concentrations. In contrast, plasma butyrate was higher (P: < 0.03) and plasma propionate tended to be higher (P: = 0.059) in subjects without lactose malabsorption after fresh yogurt consumption than after heated yogurt consumption. There were no significant changes in plasma acetate. In subjects with lactose malabsorption, 15 d of fresh yogurt consumption also increased propionate production compared with values at baseline (P: < 0.04). In the same group, the production of breath hydrogen was lower after fresh yogurt consumption than after heated yogurt consumption (P: < 0.01). CONCLUSIONS: In men with lactose malabsorption, chronic consumption of yogurt containing live bacterial cultures ameliorated the malabsorption, as evidenced by lower breath-hydrogen excretion, but increased propionate concentrations. In subjects without lactose malabsorption, such yogurt tended to increase propionate and increased butyrate.

Chronic consumption of short-chain fructooligosaccharides by healthy subjects decreased basal hepatic glucose production but had no effect on insulin-stimulated glucose metabolism.

We aimed to study the effects of chronic ingestion of short-chain fructooligosaccharides (FOS), an indigestible carbohydrate, on hepatic glucose production, insulin-mediated glucose metabolism, erythrocyte insulin binding, and blood lipids in healthy subjects. Twelve healthy volunteers received either 20 g FOS/d or sucrose for 4 wk in a double-blind crossover design. FOS did not modify fasting plasma glucose and insulin concentrations. Mean (+/- SEM) basal hepatic glucose production was lower after FOS than after sucrose consumption (2.18 +/- 0.10 compared with 2.32 +/- 0.09 mg.kg-1, min-1, respectively; P < 0.02, paired Student's t test). However, neither insulin suppression of hepatic glucose production nor insulin stimulation of glucose uptake measured by hyperinsulinemic clamp was significantly different between the two dietary periods. Erythrocyte insulin binding was also comparable. Serum triacylglycerols, total and high-density- lipoprotein cholesterol, apolipoproteins A-I and B, and lipoprotein(a) were not modified by FOS. To try to understand why FOS did not increase serum lipids, the in vitro production of short-chain fatty acids from FOS was evaluated by using human fecal inoculum and compared with that from lactulose, which was found to increase serum lipids. FOS produced an acetate-propionate ratio two times lower than that of lactulose. We conclude that 4 wk of 20 g FOS/d decreased basal hepatic glucose production but had no detectable effect on insulin-stimulated glucose metabolism in healthy subjects. The colonic fermentation pattern of undigestible carbohydrates may be relevant to predicting their metabolic effects.

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

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

Carbohydrate intake affects insulin binding to human erythrocytes in normal weight subjects but not in subjects with family obesity.

The effects of different carbohydrate intakes on insulin binding to human erythrocytes were studied in thirty nine obese and twelve normal weight subjects belonging to twelve families with a strong penetrance of obesity("family experiment"), and in nine normal weight subjects with no family or personal history of obesity or diabetes ("diet experiment"). In the "family experiment," the mean insulin binding in obese subjects was significantly lower than in control normal weight siblings and parents. This difference cannot be related to an increase in carbohydrate or caloric intakes, since there was no difference in daily food intake between the obese and the control subjects. In the "diet experiment," the volunteers were studied four times: twice with their spontaneous diet, one with a normocaloric carbohydrate rich diet and once with a normocaloric fat rich diet. Both the carbohydrate and fat rich diets resulted in a significant lowering of binding when compared to the period of spontaneous diet. In the two experiments, the decrease in binding is due to a decrease in the number of receptors per erythrocyte. The possibility of a common underlying mechanism is discussed.

Negative regulation of leptin by chronic high-glycemic index starch diet.

The response of plasma leptin to a high-glycemic index (high-GI) starch diet after a short (3 weeks) and prolonged (12 weeks) period was determined in Sprague-Dawley rats. Age-matched rats were fed an identical isocaloric diet except that the carbohydrates were from either mung bean starch (low-GI) or waxy cornstarch (high-GI). After a single test meal of the high-GI starch diet, postprandial plasma glucose (P < .05) and insulin (P < .01) peaks and plasma glucose (P < .014) and insulin (P < .05) areas were higher versus the low-GI starch diet (n = 8 per group). Other age-matched control rats were fed the same diets for a longer period. After 3 weeks, ob mRNA levels were decreased by 50% (P < .005) in the epididymal adipose tissue of high-GI-fed rats versus low-GI-fed rats, without a significant decrease in plasma leptin. After 12 weeks of the high-GI starch diet, both plasma leptin and ob mRNA were decreased by 34% (P < .005) and 41% (P < .05), respectively, compared with the low-GI diet. Both relative epididymal adipose tissue weight (adjusted per 100 g body weight) and total fat mass, as measured by dual-energy x-ray absorptiometry (DEXA), were unchanged by the high-GI starch diet. Basal nonfasting plasma insulin, glucose, and triglycerides were not altered by the high-GI starch diet, whereas free fatty acids were significantly elevated and associated with a trend (P < .13) for increased plasma free glycerol. Plasma leptin levels were negatively correlated with free fatty acid levels (r = .56, P < .05). Despite low leptin, rats fed on the high-GI diet did not increase their food intake, suggesting increased leptin sensitivity. These findings might precede weight gain and the increase in fat mass. Chronic nutritional factors might alter plasma leptin via several overlapping factors independently of energy intake.

Glycaemic and insulinaemic responses to a new hydrogenated starch hydrolysate in healthy and type 2 diabetic subjects.

BACKGROUND: Industrialists are searching for a sugar replacement in confectioneries such as hard candies, gum and chocolate. Lycasin HBC is a suitable candidate. Nevertheless, no information on its plasma glucose and insulin responses exists. Therefore, we aimed to evaluate the glycaemic and insulinaemic indices of Lycasin HBC in healthy subjects and in subjects with type 2 diabetes mellitus. METHODS: Six healthy and six type 2 diabetic men participated in the study. Each subject absorbed, after an overnight fast, a challenge of either 50 g of glucose or 50 g of Lycasin HBC using a randomised double-blind crossover design. Blood samples for measuring plasma glucose and insulin concentrations were collected during a 3 hour period. RESULTS: The calculated glycaemic index of Lycasin HBC was 47 +/- 10% in healthy subjects and 25 +/- 6% in patients with type 2 diabetes mellitus. The insulinaemic index of Lycasin HBC was 23 +/- 4% and 39 +/- 14%, respectively. As glucose levels oscillate in a very limited range in normal healthy subjects, the insulinaemic index must be considered here. On the other hand, it is the glycaemic rather than the insulinaemic index that must be assessed in diabetic subjects due to impairment of insulin secretion. CONCLUSIONS: The tested Lycasin HBC showed a low insulinaemic index in healthy subjects (23 +/- 4%) and a low glycaemic index (25 +/- 6%) in type 2 diabetic patients. Thus, it might be considered as an interesting sucrose substitute in confectionery for individuals with or without diabetes.

The organoleptic characteristics of fructose and sucrose have no differential influence on their consumption by healthy subjects.

Fructose and sucrose have different organoleptic characteristics. We studied their net impact on the rate of sugar consumption in 8 healthy families. Each family, consisting of the two parents and their 1 to 4 children, received the two sugars in a randomised cross-over blind random design. Each sugar was given for a period of one month preceded by an adaptation period of 15 days. We found no significant difference between the amount of fructose or sucrose consumed (2232 +/- 1361 vs. 2260 +/- 1272 g/family/30 days, respectively). All the subjects consumed only moderate amounts from the two sugars (17.9 +/- 8.5 vs. 18.1 +/- 7.7 for fructose and sucrose, respectively). There were no correlations between either the number or the age of children in a family and the consumed quantities per subject. The palatability of the tested sugars were comparable to a lesser or greater extent: 4 families found fructose similar to their usual sugar (sucrose) while the others found it different. Fructose was well tolerated by all the subjects without any gastro-intestinal disturbances. We concluded that fructose and sucrose were nearly equally accepted and consumed in comparable amounts by normal healthy subjects. Thus, the type of sugar used has no effect on the rate of its consumption. Several factors, independent of flavour, might contribute to the development of sugars preferences.

Comparative effects of several simple carbohydrates on erythrocyte insulin receptors in obese subjects.

The effects of simple carbohydrates on erythrocyte insulin receptors, plasma insulin and plasma glucose were studied during four hypocaloric, hyperproteic, diets. One diet contained no carbohydrate; the other three contained 36 g of either glucose, galactose or fructose. These diets were given for a 14-day period to groups of moderately obese subjects. The hypocaloric carbohydrate-free diet produced a decrease in plasma insulin and glucose concentrations concomitant with an increase in the number of insulin receptors. A similar increase in insulin receptor number was found when the diet was supplemented with glucose or galactose, but not with fructose. The presence of fructose in the diet prevented any increase in insulin receptor number.

Effects of metformin treatment on erythrocyte insulin binding in normal weight subjects, in obese non diabetic subjects, in type 1 and type 2 diabetic patients.

We have evaluated the effects of metformin administration on erythrocyte insulin receptors in 21 subjects: 5 normal weight subjects, 5 obese non diabetics, 5 insulin-dependent diabetics (Type I) and 6 obese non insulin-dependent (Type II) diabetics. Plasma glucose, plasma insulin and erythrocyte insulin receptors were studied after 15 days of metformin (850 mg, t.d.) or placebo administered in a double blind random order. Maximum specific insulin binding to erythrocytes increased after metformin in the normals (p less than 0.01), in the obese non diabetics (p less than 0.01) and in the obese Type 2 diabetics (p less than 0.005), but not in Type I diabetics. Scatchard analysis showed that the receptor number per cell increased by 37% in the normals, by 17% in the obese non diabetics and by 182% in Type 2 diabetics. Receptor affinity increased in obese subjects but did not increase in normals and in diabetics. Only in Type II diabetics was there a significant decrease in plasma glucose. Metformin, thus, increased binding in normals by moderately increasing the capacity of cell receptors, in obese non diabetics by increasing the affinity, whereas in obese Type II diabetics it dramatically increases receptor capacity. This is consistent with the fact that metformin has a hypoglycaemic effect mainly in Type II diabetics, but not in non diabetics (whether obese or not), and could be due to a direct effect on the cell membrane.