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Metabolic Responses to Venezuelan Corn Meal and Rice Bran Supplemented Arepas (Breads)
Abstract
Cereal Chem. 82(1):77-80 The metabolic responses to South American foods remain to be determined. Using glycemic index (GI) and insulinemic index (II) values as references for therapeutic potential of foods, this study investigated the glucose responses to a typical Venezuelan corn bread (arepa) and to an arepa supplemented with rice bran. Adding rice bran to the bread increased the content of resistant starch and dietary fiber measured as total, soluble, and insoluble dietary fiber. It also increased the protein content of the arepa. Three meals, white wheat bread, 100% corn meal arepa, and an arepa supplemented with 20% rice bran, were administered within a one-week period. Available starch in the foods was determined to provide 50 g of available carbohydrate per meal. To calculate the indices, bread was used as the reference. The GI and II of the two arepa meals were significantly smaller than the GI and II of white wheat bread, although the differences between the two types of arepas were not significant. It is concluded that Venezuelan arepas (corn meal bread) may have potential health benefits and that the presence of 20% rice bran in the arepa meal did not produce a significant improvement in the glucose response. Due to the presence of antioxidant elements in the supple- mented arepa and its higher protein, dietary fiber, and resistant starch content, it may have a potential preventive effect against the development of other pathologies.
... There are reports for some fruits [ 22 ], food rich in carbohydrates [ 23 ], and quinoa [ 24 ]. However, only two studies, one including arepas [ 25 ] and another with a polymeric enteral formula for people with diabetes [ 26 ], were included in the international tables because they were reported in English and had sufficient quality. ...
The allocation of glycemic index (GI) values to food composition databases is fundamental for epidemiological research and clinical practice. This study aimed to describe the methods to assign GI values to all included foods in the Venezuelan food composition table. A previous systematic 6-step method was used for the assignment to the 624 food items arranged in 14 food groups. The most recent international tables of GI were used as a primary source. 196 foods (31.4%) were assigned a GI value = 0 because they had less than 2.5g of carbohydrates. A direct match was made in 135 foods (21.6%), while 136 food items (21.8%) had a closely related assignment. Additionally, 30 mixed food items (4.8%) were calculated following the standard recipe. 48 foods (7.7%) were assigned a pre-established GI value for the subgroup to which they belong, and 9 foods (1.5%) were assigned a pre-established value of 50 for being carbohydrate contributors, whereas 70 foods (11.2%) were assigned a value of GI = 0 because they were not considered significant sources of carbohydrates. The average GI for all the groups was 51.6 ± 14.6. ‘Tubers and roots’ was the group with the highest percentage of foods with a high GI (50%). We provide the resulting database with the addition of GI values to Venezuelan foods that would be of great interest to healthcare professionals, students, and researchers in the area.
... the lipid fraction of rb has also been shown to be responsible for decreasing cholesterol in humans (MOSt et al., 2005). No differences in the glycemic index have been observed after the consumption of corn bread and corn bread supplemented with rb (ScHNELL et al., 2005). However, after the long-term consumption of whole rb or its fractions, the glucose metabolism in patients with type I and II diabetes mellitus has been shown to improve (QUrESHI et al., 2002). ...
The chemical and mechanical effects of ultrasound (US) are interesting in the food industry and this work attempts to study new applications on grapes as the raw material and then in the vinification process. Phenolic compounds extracted from grapes by means of disruption of the cell wall due to pressure alternance and cavitation were studied. The tests carried out showed an improvement in the extraction of polyphenolic substances, with a reduction in the duration of classic maceration. Also the lytic effect of the US on yeast cell structures, in order to accelerate the process of ageing over lees was evaluated, with the liberation of different fractions in the wine.
... the lipid fraction of rb has also been shown to be responsible for decreasing cholesterol in humans (MOSt et al., 2005). No differences in the glycemic index have been observed after the consumption of corn bread and corn bread supplemented with rb (ScHNELL et al., 2005). However, after the long-term consumption of whole rb or its fractions, the glucose metabolism in patients with type I and II diabetes mellitus has been shown to improve (QUrESHI et al., 2002). ...
The aim of this work was to check the efficacy of an annular ultraviolet reactor for stabilizing the growth of lactic acid bacteria (LAB), the main components of the microbiota of three raw fermented beverages, Boza, Ayran and Matsoni during cold storage. The ultraviolet (UV) dose of 260 mJ cm-2 caused a reduction of 2.6 and 1 log CFU mL-1 in the LAB loads of Boza and Ayran samples, respectively, whereas multiple UV treatments were required for Matsoni; they caused the decrease of 3 log CFU mL-1 in LAB counts. Twenty-two bacterial strains, belonging to 11 species, were identified in the natural microflora of the three beverages before and after the UV treatments. Only a minimal post-acidification process was registered up to day 30 in all the three beverages. This ultraviolet device is at disposal of beverage manufacturers, who could apply it for producing microbially-stable drinks with an extended shelf-life.
... the lipid fraction of rb has also been shown to be responsible for decreasing cholesterol in humans (MOSt et al., 2005). No differences in the glycemic index have been observed after the consumption of corn bread and corn bread supplemented with rb (ScHNELL et al., 2005). However, after the long-term consumption of whole rb or its fractions, the glucose metabolism in patients with type I and II diabetes mellitus has been shown to improve (QUrESHI et al., 2002). ...
The content of sodium, potassium, magnesium, calcium, selenium, phosphorus, nitrite and nitrate in the moss Rhodobryum ontariense and its tea was investigated for medicinal reason. The aim of this study was preliminary estimation of R. ontariense minerals' contribution to the treatment of hypertension, claimed for the moss tea by Traditional Chinese Medicine. Majority of cations were determined by EPA methods, while phosphorus was determined with an appropriate ISO method. The anions nitrite and nitrate were determined by ion chromatography. Potassium was the most abundant mineral in the investigated tea (5895.20 ± 1.22 mg/kg) and might be speculated as one of its beneficial ingredients for the treatment of elevated blood pressure conditions.
... Maize (Zea mays), also known as corn, is a major cereal grown throughout the world accounting for up to 80 % of total carbohydrates that represents either the major staple or main supplementary staple for many people across the continents (Collar 2014). Uses of maize flour in cookie making (Singh et al. 2003a, b), chapati making (Sandhu et al. 2007), arepa making (Granfeldt et al. 1995;Schnell et al. 2005) and, in general, in unleavened breadmaking (Singh et al. 2011) and ethnic goods (Collar 2014) have been successfully applied. Updated challenges and opportunities for maize in leavened breadmaking have been envisaged scarcely. ...
The ability of white (W) and yellow (Y) maize flour as basic ingredients to make nutritious and healthy breads meeting functional and sensory standards is investigated. Resistant starch (R) and common wheat flour (WF) were incorporated into formulations as single and associated extra ingredients, and dough machinability, bread nutritional and functional profiles, starch hydrolysis kinetics and keeping behaviour were assessed in blended maize matrices and compared with the maize and wheat flour counterparts. Simultaneous replacement of maize flour samples by R and WF at 40 % significantly modified textural profile, crumb grain features and firming kinetics, and free polyphenol pattern of breads thereof compared to the respective Y or W maize counterparts. Bigger specific volume (+28 % Y-R-WF, +36 % W-R-WF), softer crumb bread (-64 % Y-R-WF, W-R-WF), more aerated structure and homogeneous crumb grain, and lower and slower staling kinetics are observed in composite Y and W maize-based breads, respectively. Nutritional information on maize-based blended breads showed most appealing nutritional quality than WF breads, in terms of lower digestible starch (up to -21 % in Y-R-WF, W-R-WF, WR) and rapidly digestible starch (up to -37 % in W-R-WF), higher slowly digestible starch (up to three times in WR) and resistant starch contents (from five to six times in Y-R-WF, W-R-WF, W-R, Y-R) of medium-high sensorially rated bread matrices. All single and blended maize-based breads can be labelled as high-fibre breads (6 g dietary fibre (DF)/100 g food). According to health-related benefits and prebiotic dosage of resistant starch a daily intake of 100 g of single Y-R, W-R, W-R-WF and W-R-WF provides enough resistant starch to positively affect postprandial glucose and insulin levels, while 170 g covers the amount necessary to enhance health.
... the lipid fraction of rb has also been shown to be responsible for decreasing cholesterol in humans (MOSt et al., 2005). No differences in the glycemic index have been observed after the consumption of corn bread and corn bread supplemented with rb (ScHNELL et al., 2005). However, after the long-term consumption of whole rb or its fractions, the glucose metabolism in patients with type I and II diabetes mellitus has been shown to improve (QUrESHI et al., 2002). ...
The traceability of the origin of a variety using the anthocyanins profile was recently discussed for Sangiovese wines, producing an important market impact. The variability of the anthocyanin profile of Sangiovese was studied over three years in grapes and wines. In the same vineyard, five clones, two bunch exposure conditions and three ripening times were evaluated following a full factorial experimental design. HPLC profiles showed a wide range in variability, significantly affected by environmental and cultural factors. The grapes profile changes obtained in the vineyard were maintained in the wines. Also the relative proportions of the acetic and p-cumaric acids involved in the esterification were significantly affected.
... It is used like a side meal, and it is a base for daily food consumption mainly in the rural areas, but it is also consumed in the urban regions without preferential social status. Although arepa is an important product of massive consumption in these countries, and some studies have been aimed at evaluating nutrimental values (Granfeldt, Drews, & Bjorck, 1994) and metabolic response (Schnell, Pacheco de Delahaye, & Mezones, 2005), there has been limited information related to the physicochemical characterization of arepas and traditional and industrial corn flours. ...
The aim of this work is to study the physicochemical characterization of commercial instant corn flour (CICF) and traditional instant corn flour (TICF) prepared with threshed corn. The chemical analysis shows that there are a few amounts of fat, fiber, and minerals but the protein shows small variations in relation to the threshed corn. The CICF is characterized by coarse particles. Differential scanning calorimeter corroborated that the flours are gelatinized; but in the case of CICF the starch granules are partially disrupted and some of them are integer, producing structural changes which are identified using X-ray diffraction. A pasting analysis based on the pasting curves was conducted in order to study the apparent viscosity of these flours. The CICF shows quick water absorption at low temperatures and major values in peak viscosity than the threshed corn flour which may be related to presence of hydrocolloids. The TICF apparent viscosity showed a complete gelatinized starch.
... the lipid fraction of rb has also been shown to be responsible for decreasing cholesterol in humans (MOSt et al., 2005). No differences in the glycemic index have been observed after the consumption of corn bread and corn bread supplemented with rb (ScHNELL et al., 2005). However, after the long-term consumption of whole rb or its fractions , the glucose metabolism in patients with type I and II diabetes mellitus has been shown to improve (QUrESHI et al., 2002). ...
AbStrAct In the present study, wheat flour was replaced by 3, 6 and 9% of rice bran (rb) previously ex-posed to two types of heat treatment: extrusion (EXt) and steam cooking (Stc). the aim was to investigate how rb affected the properties of wheat-flour dough and partially baked wheat bread, as a final product. the results of the study indicate that neither of the rb treatments had a neg-ative influence on the rheological characteristics of the dough, but that its fermentation capaci-ty and gas retention improved, especially in case of EXt-rb, which was exposed to more inten-sive heat treatment. In the final bread product, there was also a positive increase in the specific total volume for the EXt-rb bread, and a decrease for the Stc-rb bread. Nevertheless, sensory analysis showed that the score for the rb-enriched bread decreased when rb content increased. We concluded that low concentrations of rb exposed to a more intensive heat stabilization pro-cess improves several rheological properties of the dough and the physical properties of the par-tially wheat bread.
... The main factor that affects GI is the rate or absorption of carbohydrate in the presence of food products. Regular consumption of foods with high GI values, particularly refined or processed carbohydrate, is associated with the development of certain chronic diseases, such as obesity, Type II diabetes, increased risk of cardiovascular diseases and certain forms of cancer (Marques et al., 2007;Schnell, de Delahaye, & Mezones, 2005). Foster-Powell, Holt, and Brand-Miller (2002) reported that addition of fibre to food products reduced their GI value. ...
Chempedak (Artocarpus integer) seed flour (CSF) was substituted for wheat flour at different levels (0%, 10%, 20%, 30% w/w) in bread. Assessment on the in vitro starch hydrolysis was carried out to evaluate the hydrolysis index (HI) and estimated glycaemic index (EGI) of bread substituted with different levels of CSF. Kinetics of in vitro starch hydrolysis in all bread samples (with the exception for white bread) indicated a gradual increase with respect to time intervals. Bread of 30% CSF exhibited significantly lower (p < 0.05) in vitro starch hydrolysis, as compared with the other samples. Results showed that HI value decreased significantly (p < 0.05) as the levels of CSF substitution increased. Resistant starch (RS) content in bread samples was inversely related with HI value as CSF substitution levels increased, thus lowering the EGI value.
Wheat and rice bran bread were prepared and evaluated. The rice bran was stabilized with heat treatment, and the amounts used were at 5% and 10%, while 100% wheat bread was used at the experiment control. Results showed that some nutritional parameters such as: ashes, fact and total dietetic fiber were improved, and there was an increase of insoluble dietetic fiber form 2.15 g/100 to 3.88 g/100. When the percentage of rice bran was increased in the bread, the farinography profile showed both a small decrease in the kneeing tolerant index and the dough stability There was a significant increase in the amilose content of bread (from 12 g/100 to 16 g /100) when it was stored at 4 oC for eight days; also, these results could shows a degradation and a possible resistant starch type III formation. This degradation was confirmed by the starch hydrolysis in vitro. Data showed a hydrolysis decrease proportional to the increase in amilose and total dietetic fiber in bread. A testing trial carried out on 30 people panel showed that bread containing 5% rice bran obtained the highest score. In conclusion, it is feasible to diversify the use of stabilized rice bran for preparing baked bread in moulds.
β-Glucan fiber has been shown to improve metabolic responses during oral glucose test or when added to food products (pasta, bread, soup, drinks, cereals, and polenta) in healthy or diabetic subjects. β-Glucans are also known to slow the rate of lipid absorption, increase bile acid transport toward the lower parts of the intestinal tract, enhance excretion of bile acids, reduce plasmatic low-density lipoprotein cholesterol (LDLc), and improve weight management and gastrointestinal function. The aim of this chapter is to evaluate the metabolic effects of the addition of β-glucans to corn maize flour. Corn maize flour (CMa-F) is a product consumed in many different ways in many countries. The addition of β-glucans to degermed precooked corn maize flour produced favorably low metabolic responses in healthy young subjects. The increase in viscosity in the small intestine during the digestion period is the proposed mechanism for this effect. The addition of β-glucans to corn maize products is relevant for its therapeutic potential. The prolonged inhibitory effect on endogenous glucose production and a longer inhibition of lipolysis after ingestion of β-glucans are important for the treatment of individuals with insulin resistance and diabetes.
Chempedak seed flour is a good source of total dietary fiber (TDF) and resistant starch (RS). The importance of dietary fiber is increasing due to its beneficial effects on the reduction of cholesterol levels and the risk of colon cancer. The important amount of starch that escapes digestion and absorption in the small intestine is commonly referred to as RS. Chempedak seed and chempedak seed flour consist of valuable nutrients such as carbohydrates, protein, dietary fiber, and resistant starch. Chempedak seed flour shows potential application as a value-added ingredient in various food products. At higher chempedak seed flour substitution levels, bread samples had significant increases in moisture, crude fiber, ash, resistant starch, and total dietary fiber. Crude fat and carbohydrate content decreased significantly with higher chempedak seed flour substitution level in bread. Loaf qualities (loaf volume and specific volume) were significantly decreased at higher substitution levels of chempedak seed flour.
Corn is one of the most important cereals for the nutrition of large groups of the Latin American population and arepa is a very popular corn-based food preparation. In order to study the arepa consumption effects on glucose and insulin response when β-glucans were added to this preparation, three different meals (white bread, corn flour arepa and arepa with β-glucans were served as breakfast to fourteen young subjects in random order after an overnight fast, to determine basal and postprandial glucose and insulin levels. One way ANOVA test was carry out to compare glucose and insulin responses between test meals and between basal and postprandial (glucose and Insulin) levels of each meal. Ingestion of white bread and corn arepa increased postprandial insulin 70,1 % and 51.8% respectively, but β-glucan arepa increased only 16% postprandial insulin levels, neither white bread and corn arepa nor β-glucan arepa increased significantly postprandial plasma glucose. In conclusion this study shows that by addition of β-glucan, to corn products like arepa reduces glucose and insulin response.
The purpose of the present investigation was to study the importance of the amylose/amylopectin ratio for the content and gastrointestinal fate of resistant starch in a realistic composite starchy food. Corn-based breads (arepas) from dent corn (25% amylose) and from high amylose corn (70% amylose) were used as test products. Resistant starch concen tration was evaluated in vitro and in vivo using rats treated with an antibiotic drug (Nebacitin) to suppress hindgut fermentation. Experiments in rats with intact hindgut microflora allowed determination of resistant starch fermentability.The small intestinal digestibilityof starch in dent corn arepas was close to 96% (total starch basis), whereas the starch in high amylose arepas was poorly digested (-68%, total starch basis), as calculated from the fecal recoveryof resistant starch in Nebacitin-treated animals. The main resistant starch fraction required solubilization in alkali to render it available to the analytical amylases (nonhydrated frac tion). The total amount of resistant starch as wellas the nonhydrated starch fraction delivered to the hindgut could be accurately predicted from analysis of starch remnants in an enzymatic gravimetric dietary fiber residue. Resistant starch present in dent corn arepas was fermented -63%, whereas the fermentability of resistant starch from the high amylose product was remarkably low (
Dried lentils (Lens culinaris) and beans (Phaseolus vulgaris, black, brown, white, and red) were boiled until soft, freeze-dried, and milled. This procedure yielded precooked flours (PCF), rich in intact cells filled with starch granules. Starch content in the various bean PCFs was underestimated by enzymic assays. Potentially available starch in PCFs was evaluated after complete release of starch by mechanical disruption of cell wall structures. Total starch content, measured after solubilization in 2 N KOH, was higher than the potentially available starch, indicating that all PCFs contained important quantities of resistant starch, i.e., retrograded amylose (3-9%, dwb). Limited enzymic availability of starch in PCFs was also demonstrated by their low α-amylolysis rate. Pepsin preincubation and additional heat treatment increased the rate and extent of in vitro enzymic hydrolysis. Considerable differences in susceptibility to α-amylase attack were observed between the various legume flours.
To define the type of dietary fibre of fibre analogue with the greatest potential use in diabetic treatment, groups of four to six volunteers underwent 50-g glucose tolerance tests (GTT) with and without the addition of either guar, pectin, gum tragacanth, methylcellulose, wheat bran, or cholestyramine equivalent to 12 g fibre. The addition of each substance significantly reduced blood glucose concentration at one or more points during the GTT and generally reduced serum insulin concentrations. The greatest flattening of the glucose response was seen with guar, but this effect was abolished when hydrolysed non-viscous guar was used. The reduction in the mean peak rise in blood glucose concentration for each substance correlated positively with its viscosity (r = 0.926; P less than 0.01), as did delay in mouth-to-caecum transit time (r = 0.885; P less than 0.02). Viscous types of dietary fibre are therefore most likely to be therapeutically useful in modifying postprandial hyperglycaemia.
Previous studies examining the hypocholesterolemic effects of high-soluble-fiber diets have not been designed to control for dietary fat intake. Serum cholesterol reductions may therefore be accounted for by differences in consumption of fat. Moderately hypercholesterolemic, nonobese, Caucasian men and women, 30-50 y old were randomly assigned to low-fat, low-fat plus high-fiber, or usual-diet groups and followed for 12 mo. At 12 mo the high-fiber group consumed significantly more soluble fiber than both the low-fat and usual-diet groups (P = 0.0063 and P = 0.0001); the high-fiber group did not differ from the low-fat group in quantity of dietary fat consumed. The high-fiber group experienced a greater average reduction (13%) in serum cholesterol than did the low-fat (9%) and usual-diet (7%) groups. After adjustment for relevant covariates, the reduction in the high-fiber group was significantly greater than that in the low-fat group (P = 0.0482). Supplementation with soluble fiber reduces serum cholesterol beyond the reduction observed with low-fat diet alone.
In the present study, the potential of including intact kernels from different cereals was evaluated as a means of developing bread with 'lente' characteristics. Postprandial glucose and insulin responses to bread products were studied in healthy subjects. In parallel, the in-vitro enzymic starch availability was investigated. Also studied were the contents of in-vitro indigestible starch. Coarse bread (CB) products composed of 80% pre-boiled kernels from wheat, rye, oats or barley and 20% white wheat flour were baked. In the case of barley, two forms for pre-treatments was used, boiling and scalding. A bread with 80% wholemeal barley flour and 20% white wheat flour (WMB) was also included and a white wheat bread (WWB) was used as reference. The glycaemic and insulinaemic indexes (GI and II, respectively) were calculated from the 95 and 120 min incremental blood glucose and insulin areas. The GIs were significantly lower with CB from wheat, rye and barley than with WWB. In contrast, the GIs with CB from oats and WMB from barley were similar to that with WWB. The GIs and IIs were generally closely correlated. However, the II with CB from oats was significantly lower than with WWB despite similar GI. The GIs, and in particular IIs, were closely correlated with the hydrolysis rate index (HI) obtained in vitro, and this procedure can be recommended as a tool for ranking of starchy food. It is concluded that the botanical structure is an important determinant of the enzymic availability and hence of the metabolic responses. The in-vitro indigestible starch content was highest in CB from barley (1.2% dry weight basis) and lowest in CB from oats (0.5%).
Dietary recommendations for the treatment of diabetic patients issued by national and international diabetes associations consistently emphasize the need to increase carbohydrate consumption. However, these recommendations have been questioned on the basis of growing evidence that, in both insulin-dependent and non-insulin-dependent diabetic patients, a high-carbohydrate diet does not offer any advantage in terms of blood glucose and plasma lipid concentrations compared with a high-fat (mainly unsaturated) diet. It has been shown repeatedly that a high-carbohydrate diet increases plasma insulin and triglyceride levels and can deteriorate blood glucose control in the postprandial period. However, much of the controversy between advocates and detractors of dietary carbohydrate can be settled by taking into account dietary fiber. Several studies have shown that the adverse metabolic effects of high-carbohydrate diets are neutralized when fiber and carbohydrate are increased simultaneously in the diet for diabetic patients. In particular, these studies demonstrated that a high-carbohydrate/high-fiber diet significantly improves blood glucose control and reduces plasma cholesterol levels in diabetic patients compared with a low-carbohydrate/low-fiber diet. In addition, a high-carbohydrate/high-fiber diet does not increase plasma insulin and triglyceride concentrations, despite the higher consumption of carbohydrates. Unfortunately, dietary fiber represents a heterogenous category, and there is still much to understand as to which foods should be preferred to maximize the metabolic effects of fiber. There are indications that only water-soluble fiber is active on plasma glucose and lipoprotein metabolism in humans. Therefore, in practice, the consumption of legumes, vegetables, and fruits--rich in water-soluble fiber--should be particularly encouraged. The mechanisms by which dietary fiber exerts its hypoglycemic and hypolipidemic activities are unknown. However, the ability of dietary fiber to retard food digestion and nutrient absorption certainly has an important influence on lipid and carbohydrate metabolism. The beneficial effects of high-fiber foods are also exerted by some foods not particularly rich in fiber. The fiber content and physical form of the food can influence the accessibility of nutrients by digestive enzymes, thus delaying digestion and absorption. The identification of these foods with a low-glycemic response would help enlarge the list of foods particularly suitable for diabetic patients. In conclusion, a diet low in cholesterol and saturated fat should be recommended to all diabetic patients to prevent cardiovascular disease. A balanced increase in consumption of fiber-rich foods and unsaturated fat is the most rational way to replace foods rich in saturated fat and cholesterol in the diabetic diet.
Three high-amylose rice varieties, IR42, IR36, and IR62, with similar chemical composition including amylose content (26.7-27.0%), were cooked under the same conditions and tested for in vitro digestibility as well as blood glucose and insulin responses in healthy human volunteers. The starch-digestion rate and the glycemic and insulin responses were the highest in IR42, followed by IR36 and, then IR62. The differences were not due to unabsorbed carbohydrate but were related to their physicochemical properties, such as gelatinization temperature, minimum cooking time, amylograph consistency, and volume expansion upon cooking. When the three varieties were cooked for their minimum cooking time, they had the same degree of gelatinization and their starch-digestion rates and glycemic responses were similar. We conclude that amylose content alone is not a good predictor of starch-digestion rate or glycemic response. Rice varieties with similar high-amylose contents can differ in physicochemical (gelatinization) properties and this, in turn, can influence starch digestibility and blood glucose response.
To compare high- and low-glycemic index (GI) diets in the treatment of non-insulin-dependent diabetes mellitus (NIDDM).
Sixteen subjects with well-controlled NIDDM and normal lipid profile, 10 of whom continued oral hypoglycemic medication, participated in the study. A diet that emphasized low-GI foods (e.g., porridge, pasta) was compared with a high-GI diet (e.g., processed cereals, potatoes). The GI of the low-GI diet was 15% lower than the high-GI diet (77 +/- 3 vs. 91 +/- 1) but otherwise similar in macronutrient composition and fiber, as determined by a 4-day weighed record. The diets were instituted under instruction from a dietitian who visited subjects at home on a weekly basis. Body weight was maintained within 1-2 kg.
Glycemic control was improved on the low-GI diet compared with the high-GI diet (statistically significant findings, P less than 0.05). Mean glycosylated hemoglobin at the end of the low-GI diet was 11% lower (7.0 +/- 0.3%) than at the end of the high-GI diet (7.9 +/- 0.5%), and the 8-h plasma glucose profile was lower (area under the curve above fasting 128 +/- 23 vs. 148 +/- 22 mmol.h-1.L-1, respectively). Mean fasting plasma glucose, total cholesterol triglycerides, and lipoproteins did not show important differences.
A low-GI diet gives a modest improvement in long-term glycemic control but not plasma lipids in normolipidemic well-controlled subjects with NIDDM.
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.
By means of 2 experiments, performed in 7 laboratories and using 6 different modifications in the insulin radioimmunoassay technique, it is shown that the use of standards diluted in human serum of low basal insulin concentration, instead of buffer, improves appreciably the interlaboratory precision. The cause lies perhaps in some serum factor, which could disturb some modifications of the radioimmunoassay more than others. There was no improvement of precision when the same insulin standard was used in all laboratories. Standard curves made up in different human fasting sera have a scatter only within the range of pipetting and counting error.
1. Bread alone and supplemented with guar gum at three levels (50, 100 and 150 g/kg) was given to eleven non-diabetic subjects, and blood glucose and serum insulin were determined preprandialy, and at 30 min and 60 min after commencement of the meal. The satiating effect, up to 120 min, of the guar bread and its acceptability to the same group of normal volunteers was also studied.
2. No significant differences in blood glucose were observed between control and guar breads at 30 min and 60 min, apart from 100 g guar/kg bread at 30 min ( P < 0·05). A significant difference in serum insulin was indicated between: control and 50 ( P < 0·02) and 150 ( P < 0·02) guar/kg breads at 30 min; control and 50 ( P < 0·05), 100 ( P < 0·001) and 150 ( P < 0·05) guar/ke breads at 60 min.
3. There were no significant differences in the satiety scores for control and guar breads. Significant increases in satiety attributed to 150 g guar/kg bread were found when compared to: 50 g guar/kg bread immediately after eating ( P < 0·05), 100 g guar/kg bread at 60 min ( P < 0·02) and 50 and 100 g guar/kg breads at 120min (both P < 0·05).
4. There was a positive correlation between hedonic score and relative replacement of guar ( r 0·62, P < 0·001, n 44) and from the regression line it was found that 50 and 100 g guar/kg breads produced hedonic scores close to a neutral response of 5, whereas 150 g guar/kg bread at a predictive score of 6·3 appeared to be unacceptable to our subjects.
5. Guar bread at the 100 g/kg level (59 g guar/kg bread) reduced the serum insulin by 48% at 60 min and is found to be an acceptable food product at this level of incorporation. However, more information is required to demonstrate the possible satiating potential of guar bread.
The glycemic index (GI) is a ranking of foods based on their glycemic effect compared with a standard food. It has been used to classify carbohydrate foods for various applications, including diabetes, sports, and appetite research. The purpose of these tables is to bring together all of the published data on the GIs of individual foods for the convenience of users. In total, there are almost 600 separate entries, including values for most common Western foods, many indigenous foods, and pure sugar solutions. The tables show the GI according to both the glucose and white bread (the original reference food) standard, the type and number of subjects tested, and the source of the data. For many foods there were two or more published values, so the mean +/- SEM was calculated and is shown together with the original data. These tables reduce unnecessary repetition in the testing of individual foods and facilitate wider application of the GI approach.
To test the hypothesis that replacing starch with sugar in a processed breakfast cereal that has a high glycaemic index could significantly decrease glycaemic and insulin responses.
Subjects consumed in random order three equi-carbohydrate meals based on a popular puffed rice cereal containing three levels of sucrose (0, 21 and 43 g). Postprandial glucose and insulin responses were compared using the incremental area under the curve (AUC).
Twelve healthy volunteers (5 males and 7 females) with normal glucose tolerance drawn from the university community, mean age 23 years (range: 20 to 27 year), mean body mass index 22.6 kg/m2 (range: 18.6 to 31.2 kg/m2).
Glycaemia was significantly lower after the meal containing the highest amount of sugar (glucose AUC 101.7 +/- 14.0 mmol/l.120 min) compared with the non-sweetened cereal (155.5 +/- 18.0 mmol/l.120 min, P < 0.01). There was a significant inverse correlation between the amount of sucrose incorporated and the degree of glycaemia (analysis of covariance coefficient = -1.25, P = 0.00). Similarly, the plasma insulin response was significantly lower after the highest sugar meal (insulin AUC 2267 +/- 346 microU/ml.120 min) compared with the meal without sugar (3505 +/- 365 microU/ml.120 min, P < 0.01).
We found a significant reduction in glycaemic and insulin responses when sugar replaced the rapidly digested starch in a processed breakfast cereal, i.e. the opposite of what is commonly believed. Thus sweetened breakfast cereals may not compromise glycaemic control more so than the unsweetened counterpart.
The importance of the amylose: amylopectin ratio in the postprandial glycemic and insulinemic responses to corn was studied in food products that might realistically be consumed. Healthy subjects were given test meals in the form of arepas made from ordinary (25% amylose) or high amylose (70% amylose) corn flour. The ordinary corn meal contained 45 g of potentially available starch. To exclude the possible influence of a lowered content of potentially available starch due to formation of resistant starch in the high amylose product, this product was evaluated at two levels and included either on the basis of potentially available starch (45 g) or total starch (including resistant starch) (45 g, i.e., 29 g potentially available starch), respectively. The rate of starch hydrolysis, measured in vitro employing a method based on chewing, was studied. In addition, the content of in vitro resistant starch was analyzed in all products. The meals containing high amylose corn flour produced lower areas under the glucose and insulin response curves (57 and 42% lower, respectively) than did the meals containing ordinary cornmeal. This could not be explained by a lower amount of potentially available starch. No differences were noted when subjects consumed the two high amylose meals of arepas, despite 36% lower potentially available starch in one of the meals. The rate of starch hydrolysis measured in vitro was slower in the high amylose corn products than in the ordinary corn product. Resistant starch in the ordinary product was 3 g/100 g dry matter, vs. approximately 20 g/100 g dry matter in the high amylose products. We concluded that high amylose corn products have a potential to promote favorably low metabolic responses and high resistant starch contents.
To define those patients most likely to benefit from the hypolipidemic effect of low-glycemic-index (GI) traditional starchy foods, 30 hyperlipidemic patients were studied for 3 mo. During the middle month, low-GI foods were substituted for those with a higher GI with minimal change in dietary macronutrient and fiber content. Only in the group (24 patients) with raised triglyceride levels (types IIb, III, and IV) were significant lipid reductions seen: total cholesterol 8.8 +/- 1.5% (p less than 0.001), LDL cholesterol 9.1 +/- 2.4% (p less than 0.001), and serum triglyceride 19.3 +/- 3.2% (p less than 0.001) with no change in HDL cholesterol. The percentage reduction in serum triglyceride related to the initial triglyceride levels (r = 0.56, p less than 0.01). The small weight loss (0.4 kg) on the low-GI diet did not relate to the lipid changes. Low-GI diets may be of use in the management of lipid abnormalities associated with hypertriglyceridemia.
To study the postprandial effects of changing the amylose-to-amylopectin ratio (Am:Ap) in the starch fraction of a meal, male volunteers were given hot mixed lunches ( 13% of energy as protein, 24% as fat, 6% as mono- and disaccharides, and 57% as polysaccharides) in which Am:Ap was either 0:100 or 45:55. The increase in Am:Ap resulted in a change in the shape of the glucose and insulin responses in the blood with significantly lower initial responses but a small increase for glucose and a decrease for insulin if averaged over the 6 h of the study. The rises in the concentration of free glycerol and free fatty acid that occurred after an initial drop were stronger at low Am:Ap. High-Am:Ap meals induced more satiety up to 6 h postprandially. There was no effect of Am:Ap on postprandial triacylglycerol in the blood or on breath hydrogen except for a weak trend toward a higher concentration at 6 h after the high-Am:Ap meals.
Previous studies examining the hypocholes-terolemic effects of high-soluble-fiber diets have not been designed to control for dietary fat intake. Serum cholesterol reductions may therefore be accounted for by differences in consumption of fat. Moderately hypercholesterolemic, nonobese, Caucasian men and women, 30–50 y old were randomly assigned to low-fat, low-fat plus high-fiber, or usual-diet groups and followed for 12 mo. At 12 mo the high-fiber group consumed significantly more soluble fiber than both the low-fat and usual-diet groups (P = 0.0063 and P = 0.0001); the high-fiber group did not differ from the low-fat group in quantity of dietary fat consumed. The high-fiber group experienced a greater average reduction (13%) in serum cholesterol than did the low-fat (9%) and usual-diet (7%) groups. After adjustment for relevant covariates, the reduction in the high-fiber group was significantly greater than that in the low-fat group (P = 0.0482). Supplementation with soluble fiber reduces serum cholesterol beyond the reduction observed with low-fat diet alone.
Postprandial glycemic and insulinemic responses and satiety with various barley products were evaluated in normal subjects. Also studied were the rate of in vitro starch digestion and the content of in vitro resistant starch (RS). Products tested were boiled intact (rice extender) and milled kernels (porridge) from four barley genotypes of Glacier with different amylose-amylopectin ratios (7–44% amy lose). All barley products elicited lower metabolic responses and higher satiety scores when compared with white wheat bread. The lente behavior of the boiled flours was probably due to the viscous properties of the β-glucans. However, the boiled flours produced higher glucose and insulin responses than did the corresponding boiled kernels. The impact of amylose: amylopectin on the metabolic responses was marginal. The high-amylose products released starch more slowly from a dialysis tubing during enzymic incubation of chewed samples compared with the corresponding products with less amylose. The RS content ranged from 0.4% in waxy to 5.6% in the high-amylose flour product (starch basis).
The functional and nutraceutical properties of rice bran oil provide several unique food applications.
Unsaponfiable matter (U) was prepared from both raw and extrusion stabilized (130'C) rice bran and tested for cholesterol-lowering activity in hamsters by addition to diets containing cellulose, raw rice bran, or stabilized rice bran at either the level found in the rice bran diet (0.4%, 1X) or twice that level (2X). All diets contained 0.3% cholesterol, 10% total dietary fiber, 10.1% fat, and 3% N (same plant-to-animal N ratio). After 21 days, plasma cholesterol was significantly reduced by rice bran diets containing added U compared to the cellulose control diet, while the high density lipoprotein cholesterol-to-low density lipoprotein cho- lesterol ratio remained unchanged in all treatment groups. Liver choles- terol was significantly reduced by all rice bran-containing diets and with cellulose diets containing 2X added U when compared to the control diet. Rice bran diets plus added U resulted in cholesterol values lower ABSTRACT
Amylose from potatoes was complexed with lysolecithin and oleic acid. The degradation of complexed amylose by hog pancreatic α-amylase in-vitro was studied, as well as the in-vivo absorption in the rat. The presence of a bacterial thermostable α-amylase in the gelatinization step increased the result of a starch analysis using glucoamylase. Complexed amylose displayed a substantially reduced susceptibility to α-amylase in-vitro. However, when adding a large excess of enzyme, the complex was completely hydrolyzed after 3 h. Amylose-lysolecithin complex disappeared from the gastrointestinal tract within 120 min. The complexed amylose was hydrolyzed and adsorbed to the same extent as free amylose in-vivo but somewhat slower.
Verdaulichkeit von Amylose-Lipid-Komplexen in vitro und in vivo.
Kartoffelamylose wurde mit Lysolecithin und Ölsäure komplexiert. Der Abbau komplexierter Amylose durch Schweine-Pankreas-α-Amylase in vitro sowie die in vivo-Absorption in der Ratte wurden untersucht. Die Anwesenheit von thermostabiler Bakterien-α-Amylase während der Verkleisterungsstufe erhöhte das Ergebnis einer Stärkeanalyse bei Verwendung von Glucoamylase. Komplexierte Amylose zeigte eine wesentlich verringerte Angreifbarkeit durch α-Amylase in vitro. Wenn jedoch ein großer Überschuß an Enzym zugegeben wurde, war der Komplex innerhalb von 3 h vollständig hydrolysiert. Der Amylose-Lysolecithin-Komplex verschwand innerhalb von 120 min aus dem Magen-Darm-Trakt, woraus zu ersehen ist, daß die komplexierte Amylose hydrolysiert und in gleichem Ausmaß absorbiert wurde wie freie Amylose in vivo.
In a modified method for measuring Resistant Starch (RS) in dietary fiber residues all operations for obtaining fiber residues and determination of RS were performed in a 50 mL centrifugation tube. This minimized error sources and simplified previous methodology.
A rapid enzymic method for starch analysis, especially in cereal products, is presented. One person can analyze 30 samples per day. The method includes a 15 min gelatinization step in a boiling water bath in the presence of a thermostable α-amylase, a 30 min amyloglucosidase incubation of a subsample, and subsequent determination of glucose with a glucose oxidase/peroxidase reagent. The method was evaluated by analysis of the starch content in various raw and industrially processed wheat samples. The method showed high precision (CV=0.6–1.0%) and accuracy. Some factors which might affect the enzymic availability of starch and thus its recovery in the analysis are evaluated and discussed.
Eine schnelle Methode Zur Bestimmung von Stärke.
Es wird eine schnelle enzymatische Methode zur Bestimmung von Stärke, insbesondere in Getreideprodukten, vorgestellt. Eine Person kann 30 Proben am Tag untersuchen. Die Methode umfaße eine 15 min lange Verkleisterung in Gegenwart einer thermostabilen α-Amylase in einem kochenden Wasserbad, eine 30 min lange Behandlung eines Teiles der Probe mit Amyloglucosidase und eine nachfolgende Bestimmung der Glucose mit einem Glucoseoxidase/Peroxidase-Reagens. Die Beurteilung der Methode erfolgte durch die Bestimmung des Stärkegehaltes in verschiedenen rohen und industriell verarbeiteten Weizenproben, sie zeigte große Genauigkeit (CV = 0,6–1,0%). Einige Faktoren, welche die enzymatische Verfügbarkeit von Stärke und somit ihre Erfassung bei der Bestimmung beeinflussen, werden diskutiert.
Heat-processed foods can contain appreciable amounts of resistant starch (RS) that has the ability to survive prolonged incubation with a-amylase and other amylolytic enzymes. The occurrence of RS has important implications for dietary fibre (DF) determination and, possibly, for human bowel physiology also. Studies using cereal and potato starches have identified three key factors that influence yields of RS after heat-processing, i.e. amylose content, processing temperature and water content. The highest yields of RS (20–34% of total dry weight) were obtained from amylomaize starches, either raw or processed, and from amylopectin starches (32–46% RS) after incubation with α-(1→6)-debranching enzyme (pullulanase) followed by heat-processing. In contrast, the lowest yields of RS (0⁗2–4⁗md2%) were obtained from intact (i.e. non-debranched) amylopectin starches, with or without heat-processing. Yields of RS from wheat starch were affected primarily by processing temperature, reaching levels of about 9% in a single cycle of autoc1aving at 134°C with excess water and subsequent cooling (cf. levels of less than 1% in uncooked wheat starch) and higher levels still (about 15%) after five repeated cycles of autoclaving and cooling. A similar increase in yields of RS was seen in dilute (1%) starch suspensions that were subjected to repeated cycles of heating to 100°C, followed by cooling and storage. The time of storage after gelatinisation was only important in these dilute systems: levels of RS in freshly prepared concentrated starch gels (typically 57–67% H2O) or in white bread did not alter significantly on storage.
A method for resistant starch (RS) determination in food and food products is proposed. The main features are: removal of protein; removal of digestible starch; solubilization and enzymatic hydrolysis of RS; and quantification of RS as glucose released. Stomach and intestine physiological conditions (pH, transit time) were approximately simulated. All operations were performed in a 50ml centrifuge tube. Reference materials and food products were analysed by three laboratories. Statistical analysis included repeatability and reproducibility. This procedure is quite satisfactory for starchy foods containing appreciable quantities of RS and it may be useful for nutritional labelling of foodstuffs. For samples containing ⩽ 1% RS, differences are not significant and they can be considered as foods with a negligible RS content.
Food carbohydrates consist of mono-, di-, oligo- and polysaccharides, the latter composed of starch and non-starch polysaccharides (NSP). The glycaemic response to both sugars and starches is dependent on the types of sugars present and the form of the starches, and ‘complex carbohydrates’ do not necessarily produce slower or lower glycaemic responses than the sugars. Carbohydrates not absorbed in the small intestine are fermented more or less extensively by the large intestinal microflora. There is a fundamental difference nutritionally between digestible and undigestible (‘unavailable’) carbohydrates. NSP, resistant starch (RS) and oligosaccharides are the main forms of undigestible carbohydrates. Dietary fibre is generally conceived as more or less synonymous with ‘unavailable’ carbohydrates. The nutritional effects of dietary fibre are related to its undigestibility in the small intestine, and to the physical and chemical properties of its constituent polysaccharides. Food structures built of dietary fibre as plant cell-walls, and also of other food components, are increasingly recognized as nutritionally important. Food databases should include as much specific and detailed information as possible on food carbohydrates. For food labelling, carbohydrates have to be divided into a number of nutritionally meaningful classes. A first classification should then aim at differentiating the digestible and undigestible carbohydrates, i.e. dietary fibre.
From the mid-1970s several groups realized progressively that the same amounts of carbohydrates in different foods produce quite different blood glucose curves after ingestion. The glycaemic index (GI) was introduced by Jenkins to express the rise of blood glucose after eating a food against a standard blood glucose curve after glucose (or white bread) in the same subject. The GI ranges from about 20 for fructose and whole barley to about 100 for glucose and baked potato. A table is given of representative GI values. There appears to be no general correlation between GI and per cent resistant starch in foods. Questions about methodology for GI are discussed and the factors in food that affect glycaemic response are briefly reviewed. The GI is affected by the physical form of a food, by processing and by associated fat in the food, which reduces the GI, presumably by delayed gastric emptying. As a rule the degree of insulin response to carbohydrate-containing foods is similar to the glycaemic response. Most investigators have found that the GI of a meal of mixed foods can be predicted from the (weighted) GI of its constituent foods. The GI concept is proving useful in dietary design for the management of diabetes mellitus, especially the non-insulin-dependent type. It may prove useful for prevention of diabetes and perhaps also in pre-event meals for athletes, as a factor in dental cariogenesis, in determining satiety, and conceivably regular low GI foods could delay ageing by reducing glycosylation of body proteins.
To study the postprandial effects of changing the amylose-to-amylopectin ratio (Am:Ap) in the starch fraction of a meal, male volunteers were given hot mixed lunches (13% of energy as protein, 24% as fat, 6% as mono- and disaccharides, and 57% as polysaccharides) in which Am:Ap was either 0:100 or 45:55. The increase in Am:Ap resulted in a change in the shape of the glucose and insulin responses in the blood with significantly lower initial responses but a small increase for glucose and a decrease for insulin if averaged over the 6 h of the study. The rises in the concentration of free glycerol and free fatty acid that occurred after an initial drop were stronger at low Am:Ap. High-Am:Ap meals induced more satiety up to 6 h postprandially. There was no effect of Am:Ap on postprandial triacylglycerol in the blood or on breath hydrogen except for a weak trend toward a higher concentration at 6 h after the high-Am:Ap meals.
There is controversy regarding the clinical utility of classifying foods according to their glycemic responses by using the glycemic index (GI). Part of the controversy is due to methodologic variables that can markedly affect the interpretation of glycemic responses and the GI values obtained. Recent studies support the clinical utility of the GI. Within limits determined by the expected GI difference and by the day-to-day variation of glycemic responses, the GI predicts the ranking of the glycemic potential of different meals in individual subjects. In long-term trials, low-GI diets result in modest improvements in overall blood glucose control in patients with insulin-dependent and non-insulin-dependent diabetes. Of perhaps greater therapeutic importance is the ability of low-GI diets to reduce insulin secretion and lower blood lipid concentrations in patients with hypertriglyceridemia.
Different starchy foods produce different glycemic responses when fed individually, and there is evidence that this also applies in the context of the mixed meal. Methods of processing, and other factors unrelated to the nutrient composition of foods may also have major effects on the glycemic response. The reason for differences in glycemic response appears to relate to the rate at which the foods are digested and the many factors influencing this. The glycemic index (GI) is a system of classification in which the glycemic responses of foods are indexed against a standard (white bread). This allows the results of different investigators to be pooled. GI values also depend upon a number of nonfood-related variables. The method of calculation of the glycemic response area is most important, but the method of blood sampling and length of time of studies also may have effects. Variability of glycemic responses arises from day-to-day variation in the same subject and variation between different subjects. There is less variability between the GI values of different subjects than there is within the same subject from day to day. Therefore, the mean GI values of foods are independent of the glucose tolerance status of the subjects being tested. Potentially clinically useful starchy foods producing relatively flat glycemic responses have been identified, including legumes, pasta, barley, bulgur, parboiled rice and whole grain breads such as pumpernickel. Specific incorporation of these foods into diets have been associated with reduced blood glucose, insulin, and lipid levels. Low-GI foods may influence amino acid metabolism although the implications of these are unknown. In addition, low GI foods increase colonic fermentation. The physiologic and metabolic implications of this relate to increased bacterial urea utilization, and to the production and absorption of short chain fatty acids in the colon. The application of the GI to therapeutic diets should be in the context of the overall nutrient composition of the diet. High-fat or high-sugar foods may have a low GI, but it may not be prudent to recommend these foods solely on the basis of the GI. It is therefore suggested that the most appropriate use of the GI is to rank the glycemic effects of starchy foods which would already have been chosen for possible inclusion in the diet on the basis of their nutritional attributes, i.e. low-fat, unrefined carbohydrate.
Twelve men consumed a diet containing 34% of calories as 70% amylose or amylopectin starch to determine if the structure of starch could influence metabolic factors associated with abnormal states. Each starch was fed to subjects for 5 wk in a crossover design. No significant differences were observed in glucose or insulin levels when a glucose tolerance was given after 4 wk on each starch. However, glucose and insulin responses were significantly lower when a meal containing amylose compared with amylopectin was consumed after 5 wk on each starch. Summation of 0.5 through 2-h levels of insulin but not glucose were significantly lower after amylose compared with levels after amylopectin. Mean fasting triglyceride and cholesterol levels were significantly lower during the period when amylose was consumed. Long-term intake of dietary amylose may be valuable in decreasing insulin response while maintaining proper control of glucose tolerance and low levels of blood lipids.
The glycaemic index is a measure of the extent to which the carbohydrate in a food can raise the blood glucose concentration and helps to identify foods which may be beneficial to a diabetic patient. This paper reviews the results that have been obtained so far with the glycaemic index approach, the factors that affect the glycaemic response, the problems that are associated with its measurement and its value in planning diabetic diets. Individual variation and variation among individuals in glycaemic responses are also discussed.
An investigation, aimed at determining the nature and relative utilization of carbohydrates of recently evolved high yielding varieties of rice was carried out. The amylose content and the starchâ€"iodine blue value were deter mined in relation to the cooking quality of these varieties. The rates of in vitro digestibility using a-amylase were compared. The significance of in vitro experi ments was further tested in vivo in human subjects with two of the varieties which differed greatly in in vitro o-amylolysis. These studies revealed that the amylose content in these varieties ranged from 15 to 22% of the starch. The Hamsa variety showed highest value for amylose while the amylose content of IR-8 was exceptionally low â€" 15% of its starch. The in vitro digestibility trials using pancreatic a-amylase indicated that the rate of o-amylolysis of Hamsa variety was higher compared with any other variety analyzed whereas that of IR-8 rice was markedly lower. Studies carried out with Hamsa and IR-8 varieties of rice on human subjects indicated that with Hamsa more subjects showed higher blood glucose values compared with IR-8. J. Nutr. 101: 879-884, 1971.
Serial measurements of serum cholesterol and triglyceride (TG) concentrations were performed in diabetic men fed high-carbohydrate, high-fiber (HCF) as well as high-carbohydrate, low-fiber (HCLF) diets. Fourteen lean men were first fed control diets for 1 wk and then fed weight-maintaining HCF diets (70% carbohydrate) that were restricted in fat and cholesterol. Average insulin doses dropped from 27 U/day on control diets to 12 U/day on HCF diets and fasting plasma glucose values were 26 mg/dl lower on HCF diets. On HCF diets, serum cholesterol values were lower by 32% (64 mg/dl, p < 0.001) than values on control diets. Fasting serum TG values were slightly lower on HCF diets but average postprandial TG values were significantly lower (p < 0.001) on HCF diets than on control diets. In another study, 11 men were fed two weight-maintaining 70% carbohydrate diets in an alternating sequence; one diet was high in plant fiber (HCF) and the other was low in plant fiber (HCLF). Insulin doses averaged 20 U/day on control diets and fell to 11 U/day (p < 0.01) on HCF diets or 12 U/day (p < 0.01) on HCLF diets. Fasting serum TG values were similar on the control and HCF diets; on HCLF diets fasting serum TG values were higher by 28% (37 mg/dl) than values on control diets (p < 0.01). Incorporation of generous amounts of plant fiber into the diet prevented the hypertriglyceridemic response to these high-carbohdrate diets. These studies also indicate that dietary maneuvers can be very effective in lowering serum cholesterol values in patients with diabetes mellitus.
The effects of acute and chronic dietary fiber (cellulose and pectin) supplementation on both intestinal glucose absorption and oral glucose tolerance were studied in rats. The effect of intraluminal fiber on intestinal glucose absorption was evaluated in perfused jejunal loops as was the effect of a single cellulose or pectin-supplemented meal on serum glucose responses to a carbohydrate load. Neither pectin nor cellulose impaired jejunal glucose absorption, but pectin did decrease serum glucose responses to an oral carbohydrate load. Chronic fiber supplementation significantly decreased intestinal glucose absorption in rats who had received for 5 wk a fiber-free diet supplemented with either cellulose (10%) or pectin (5%). Chronic supplementation with cellulose or pectin impaired intestinal glucose absorption and decreased serum glucose responses. These results suggest that differences in glucose homeostasis observed after ingestion of single high-fiber meals may be caused by viscosity-related delays in the rate of gastric emptying, whereas differences noted after chronic supplementation of dietary fiber are related to adaptive changes in the intestine.
The determine the effect of different foods on the blood glucose, 62 commonly eaten foods and sugars were fed individually to groups of 5 to 10 healthy fasting volunteers. Blood glucose levels were measured over 2 h, and expressed as a percentage of the area under the glucose response curve when the same amount of carbohydrate was taken as glucose. The largest rises were seen with vegetables (70 +/- 5%), followed by breakfast cereals (65 +/- 5%), cereals and biscuits (60 +/- 3%), fruit (50 +/- 5%), dairy products (35 +/- 1%), and dried legumes (31 +/- 3%). A significant negative relationship was seen between fat (p less than 0.01) and protein (p less than 0.001) and postprandial glucose rise but not with fiber or sugar content.
1. Experiments were carried out in human volunteers to investigate the mechanism by which guar gum improves glucose tolerance.
2. Guar reduced both plasma glucose and insulin responses to an oral glucose load, and delayed gastric emptying. However, there was no correlation between changes in individual blood glucose responses and changes in gastric emptying rates induced by guar.
3. With a steady-state perfusion technique, glucose absorption was found to be significantly reduced during perfusion of the jejunum with solutions containing guar, but returned to control values during subsequent guar-free perfusions.
4. Preperfusing the intestine with guar did not affect electrical measurements of unstirred layer thickness in the human jejunum in vivo..
5. Experiments in vitro established that glucose diffusion out of a guar/glucose mixture was delayed under conditions of constant stirring.
6. We conclude that guar improves glucose tolerance predominantly by reducing glucose absorption in the small intestine. It probably does this by inhibiting the effects of intestinal motility on fluid convection.
A two-stage perfusion technique was used to study the effect of guar gum on the inulin-accessible space and the uptake of water and glucose in rat intestine. Pre-perfusion of test loops with low concentrations of guar, dispersed in saline, modified the rate of equilibration of inulin with the mucosal fluid space during a subsequent perfusion. The glucose absorption rate in such loops was reduced at a concentration of 50 mM, but not at 100 or 150 mM glucose. Fluid absorption was inhibited by pre-treatment with guar gum at all glucose concentrations tested. These results suggest that guar forms a layer closely associated with the mucosal surface which modifies the viscosity of the immediate fluid compartment, so that its resistance to diffusion is increased by means of an unstirred layer effect.
The rise of blood glucose in normal and diabetic subjects after meals varies markedly and depends on many factors, including the source of the carbohydrate, its method of preparation, and the composition of the total meal. Classification of carbohydrates as simple or complex does not predict their effects on blood glucose or insulin. Rapidly absorbed carbohydrates, which produce large blood glucose and insulin responses, may be in the form of both sugars and starches. Sugars added to foods have no different effect on blood glucose from those of sugars alone. The natural sugars in fruit and fruit juices raise blood glucose approximately as much as does sucrose and less than do most refined starchy carbohydrate foods. The optimum amount of sugars in the diet is not known. However, undue avoidance of sugars is not necessary for blood glucose control and is not advised because it may result in increased intakes of fat and high-glycemic-index starch.
Although fiber has been increasingly recognized as an important dietary constituent, controversy and confusion still exist about the physiologic effects of fiber. Specifically, the independent ability of dietary fiber to lower serum lipid levels is controversial. The purpose of this article is to review available evidence regarding the impact of soluble fibers on serum lipid levels. Soluble fibers appear to have a greater potential to alter serum lipid levels than do insoluble fibers. Significant reduction in the level of serum total cholesterol by soluble fiber was found in 68 of the 77 (88%) human studies reviewed. Of the studies measuring low-density lipoprotein cholesterol, 41 of 49 (84%) reported significant reductions. No significant changes were reported in 43 of the 57 (75%) studies that reported high-density lipoprotein cholesterol and/or in 50 of the 58 (86%) studies that measured triglyceride levels.