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The Journal of Nutrition Vol. 128 No. 11 November 1998,
pp. 2032-2035
, 2,,
* Department of Animal Sciences, University of Illinois, Urbana, IL 61801 USA and 
Division of Nutritional Sciences, University of Illinois, Urbana, IL 61801 USA and ** Ross Products Division, Abbott Laboratories, Columbus, OH 43219 USA
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ABSTRACT |
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Abstract
Introduction
Methods
Results
Discussion
References
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The purpose of this study was to evaluate apparent digestibility in ileal-cannulated dogs fed enteral diets containing a debranched amylopectin-lipid complex (V-complex) or resistant starch. Six ileal-cannulated dogs were randomized into a replicated 3 × 3 Latin square design for determination of digestibility of three experimental treatments. Dietary treatments were as follows: 1) control; 2) V-complex; and 3) resistant starch. Diets were similar in chemical composition. Apparent digestibility of dry matter (DM), organic matter (OM) and carbohydrate by dogs fed the control diet was higher (P < 0.05) than for dogs consuming the other diets. Mean apparent digestibilities of carbohydrate for the control, V-complex and resistant starch diets were 89, 76 and 43%, respectively. Both DM and carbohydrate digestibility were lower (P < 0.05) for resistant starch compared with V-complex. Fecal dry and wet weights for dogs fed the control diet were lower (P < 0.05) than for those receiving either the resistant starch or V-complex treatments. Dogs fed the V-complex diet produced ~90 g less feces per day than dogs fed resistant starch. Dietary incorporation of V-complex to replace traditional carbohydrates may be beneficial for diabetic patients because of the decreased digestibility and subsequent glucose absorption rate. Furthermore, incorporation of resistant starch into enteral formulas may improve gastrointestinal tract health status as a result of increased fecal bulk, potential dilution of toxins in the intestinal lumen and greater production of short-chain fatty acids.
KEY WORDS:
resistant starch ·
debranched amylopectin-lipid complex ·
digestion ·
dogs
Differences in glycemic and insulin responses to dietary starch are related directly to the rate of starch digestion (Bornet et al. 1990 It is possible to modify the physical structure of starch by retrogradation so that it is partially inaccessible to enzymatic attack (Annison and Topping 1994 Animals.
Six adult (3-4 y of age) purpose-bred female dogs (Butler Farms USA, Clyde, NY) with hound bloodlines and an average weight of 25 ± 5 kg were surgically prepared with ileal cannulas. Ileal cannulation was conducted according to Walker et al. (1994) Dietary treatments.
Three dietary treatments were evaluated in the study: control , V-complex, and resistant starch. Treatments were provided as powders and reconstituted with water to produce a liquid formula with 4.18 MJ of metabolizable energy (ME)3 per L. The control diet consisted of a high nonstructural carbohydrate enteral formula designed to provide all essential nutrients as described for humans (Table 1). The entire carbohydrate fraction and ~10% of the lipid fraction in the control diet were replaced by the V-complex. The V-complex was manufactured by simultaneously debranching starch with a food-grade enzyme and allowing the resultant linear glucose oligomers to react with the added lipids. The resistant starch (high amylose corn; Crystalean, Opta Food Ingredients, Cambridge, MA) was added in place of the carbohydrate used in the control treatment.
Experimental design.
Six dogs were randomized in a replicated 3 × 3 Latin square design with 10-d periods. The Latin squares were run simultaneously. Total duration of the experiment was 30 d. Days 1 through 6 constituted the diet adaptation phase and d 7 through 10 were used for ileal and fecal collections (collection phase). Dogs were provided with ~2 L daily to supply ~8.36 MJ ME/d. One half of this amount was supplied every 12 h (0800 and 2000 h). Chromic oxide was used as a digestion marker. Beginning on d 3 of each period, dogs were dosed orally twice daily, before each feeding, with 0.5 g chromic oxide in a gelatin capsule for a total of 1 g of marker/d through d 10 of each period.
Sampling procedures.
During the collection phase, ileal effluent and feces were collected. A 4-d collection phase was used, with ileal effluent collected three times daily. Each collection was allowed to proceed for 1 h. On d 1 of the collection phase (d 7 of the experiment), sampling took place at 0800, 1200 and 1600 h. The sampling times were advanced 1 h each day for the three remaining days to lessen diurnal variability. For example, on d 2, samples were collected at 0900, 1300 and 1700 h. Ileal effluent was collected by attaching a Whirlpak bag (Pioneer Container, Cedarburg, WI) to the cannula barrel and around the cannula hose clamp with a rubber band. Before attachment of the bag, the interior barrel of the cannula was scraped clean with a spatula and initial digesta discarded. After the collection bags were removed, the area around the cannula was washed with a warm Betadine solution (Becton Dickinson Acute-Care Division, Franklin Lakes, NJ) and dried with a paper towel. Dogs were encouraged to move around freely during the collection. Elizabethan collars were used at collection times so that dogs did not pull the bag from the cannula. Total feces excreted during a 24-h period on each of the 4 d were collected from the floors of the pens, weighed, composited and frozen at Sample handling.
Ileal samples were frozen in their individual bags at Chemical analyses.
Diets, feed refused, ileal contents and feces were analyzed for DM (dry matter), OM (organic matter) and ash content according to AOAC (1984) procedures. Crude protein (CP) concentration was calculated from Kjeldahl N values (N × 6.25) for all samples (AOAC 1984). Total lipid content was determined by acid hydrolysis followed by ether extraction according to the American Association of Cereal Chemists (1983) and Budde (1952) Calculations.
Dry matter flow (g/d) recovered as ileal effluent or excreted as feces was calculated by dividing daily chromium intake (mg) by ileal or fecal chromium concentration (mg Cr/g ileal effluent or feces), respectively. Nutrient flows were calculated by multiplying DM flows by the concentration of the nutrient in ileal or fecal DM. Ileal and total tract nutrient digestibilities were calculated as nutrient intake (g/d) minus the ileal or fecal nutrient flow (output, g/d), divided by nutrient intake (g/d).
Fecal scoring.
Fecal samples were scored for each dog during each period according to the following system: 1 = hard, dry pellets: small, hard mass; 2 = hard, formed, dry stool: remains firm and soft; 3 = soft, formed, moist: softer stool that retains shape; 4 = soft, unformed: stool assumes shape of container, pudding-like; 5 = watery: liquid that can be poured.
Statistical analyses.
Data were analyzed by the General Linear Models procedure of SAS (1994). Model sums of squares were separated into treatment, period and animal effects. When significant differences (P < 0.05) were detected, means were compared by the least-square means method of SAS (SAS 1994).
Chemical composition.
The chemical composition of the diets is reported in Table 1. Organic matter, crude protein, fat and carbohydrate concentrations were similar among diets.
Nutrient intake and digestibility.
Nutrient intake and apparent digestibility data are presented in Table 2. All of the dogs consumed the entire amount of food offered. Significant differences in intake were noted for all nutrients except crude protein and fat. Dry matter and OM intakes were higher (P < 0.05) for the resistant starch treatment than for the other treatments. Dry matter and OM intakes by dogs fed the V-complex diet were lower (P < 0.05) than for those fed the control diet. Carbohydrate intake was ~5 and 9 g/d lower (P < 0.05) for the V-complex treatment than for the control and resistant starch treatments, respectively.
Ileal digestibility.
Digestibilities of DM and OM were lowest (P < 0.05) for the resistant starch treatment. Ileal DM and OM digestibilities were ~28 and 17 percentage units lower when dogs were fed the resistant starch diet compared with the control and V-complex diets, respectively. Furthermore, digestibilities of DM and OM by dogs fed the V-complex diet were lower (P < 0.05) than for those fed the control diet. Crude protein digestibility did not differ among treatments. Digestibility of fat by dogs was lower (P < 0.05) for the V-complex treatment than for the other treatments. Carbohydrate digestibility was ~42 and 29 percentage units lower (P < 0.05) for the resistant starch diet than for the control and V-complex diets, respectively. Ileal digestibility of carbohydrate by dogs fed the V-complex diet was 13 percentage units lower (P < 0.05) than for those fed the control diet.
Total tract digestibility.
Total tract DM and OM digestibilities were ~25 percentage units lower for the resistant starch than for the control treatment. Dry matter and OM digestibilities by dogs fed the V-complex diet were intermediate. Crude protein digestibility by dogs fed the control diet was higher (P < 0.05) than for those fed the other diets. Total tract fat digestibility was lowest when dogs were fed the V-complex diet and followed a trend similar to that of fat digestibility at the terminal ileum. Total tract carbohydrate digestibility by dogs fed the resistant starch diet was ~34 and 45 percentage units lower than that for the V-complex and control diets, respectively, and paralleled ileal carbohydrate digestion. This suggests that no post-ileal digestion of resistant starch occurred. Carbohydrate digestibility of the V-complex treatment was intermediate.
Fecal characteristics.
Wet weight (as-is), fecal DM (55°C), dry fecal weight and fecal score data are presented in Table 3. Fecal wet weights for dogs receiving V-complex and resistant starch treatments were two- and fourfold greater, respectively, than fecal wet weight for dogs consuming the control diet. Fecal dry weight for dogs receiving the control diet was 67 and 84% lower than the dry fecal weights for dogs consuming the V-complex and resistant starch diets, respectively. Dry matter content of feces of dogs fed the resistant starch diet was ~10 percentage units higher than for those receiving V-complex or control diets. Fecal score for dogs consuming either the control or V-complex diets was higher (i.e., softer stool) than for those fed the resistant starch diet. Fecal score inversely paralleled the DM content of feces.
When starch is heated in an excess of water, gelatinization occurs (Colona and Mercier 1985
INTRODUCTION
Abstract
Introduction
Methods
Results
Discussion
References
, Jenkins et al. 1981, O'Dea et al. 1981). A factor that appears to be responsible for differences in rate of digestion is the relative amounts of amylose and amylopectin in the starch fraction. Rate of amylose digestion is slower than that of amylopectin (Goddard et al. 1984). Several explanations for the slower rate of amylose (a linear polymer) digestion have been presented. First, the glucose units of amylose participate more in hydrogen bonding than do glucose units of the branched-chain amylopectin, making them less accessible to enzymatic digestion (Thorne et al. 1983). Second, amylopectin is a larger molecule than amylose and has a larger surface area for enzymatic attack (O'Dea et al. 1980). Third, the presence of amylose-lipid complexes may reduce the rate of amylose digestion (Goddard et al. 1984, Holm et al. 1983, Seneviratne and Biliaderis 1991).
). This form of starch is often referred to as resistant starch. It is also possible to complex the amylose portion of starch with lipids so that it is less susceptible to enzymatic attack (Biliaderis and Galloway 1989, Eliasson and Krog 1985). This complex is generally referred to as V-complex because it exhibits a "V-type" X-ray diffraction pattern. V-complex has been incorporated into enteral formulas for the purpose of controlling digestion of dietary carbohydrates and subsequent glucose absorption rate. The purpose of this study was to investigate the effects of V-complex and resistant starch on the digestibility of nutrients when V-complex and resistant starch are major components of an enteral formula.
MATERIALS AND METHODS
Abstract
Introduction
Methods
Results
Discussion
References
. Dogs were housed individually in 1.2 × 3.1 m clean floor pens in a temperature-controlled room (21°C) at the animal facility of the Edward R. Madigan Laboratory (ERML) on the University of Illinois campus. An 8-h dark:16-h light cycle was used. All dogs were allowed free access to water. The surgical and animal care procedures were reviewed and approved by the Campus Laboratory Animal Care Advisory Committee, University of Illinois at Urbana-Champaign.
View this table:
Table 1.
Chemical composition of diets
4°C.
4°C. After completion of the experiment, all effluent collected was composited for each dog in each period, mixed well and refrozen at 4°C. Ileal effluent and feces were dried at 55°C in a forced-air oven. After drying, ileal effluent and feces were ground through a 2-mm screen in a Wiley mill (Arthur H. Thomas, Philadelphia, PA) in preparation for chemical analyses.
. The carbohydrate concentration of each diet was determined as follows: (OM,%) (CP,% + Fat,%). Chromium content of ileal digesta and feces was measured by the technique of Williams et al. (1962). Concentration of chromium was determined using atomic absorption spectrophotometry.
RESULTS
Abstract
Introduction
Methods
Results
Discussion
References
View this table:
Table 2.
Nutrient intake and digestibility data for dogs fed enteral diets1
View this table:
Table 3.
Fecal characteristics of dogs fed enteral diets1
DISCUSSION
Abstract
Introduction
Methods
Results
Discussion
References
) in which amylose and amylopectin molecules associate to form a gel (Miles et al. 1985). Starch gels are unstable and age with time, displaying a "B-type" X-ray diffraction pattern (Colona et al. 1992) also referred to as retrograded starch. Retrogradation can be increased by repeated heating and cooling of starch in cycles (Sievert et al. 1991). This leaves a fraction (termed resistant starch) that resists amylolytic degradation. A "V-type" X-ray diffraction pattern is observed when amylose chains complex with fatty acids and (or) monoglycerides (Biliaderis and Galloway 1989). The V-complex tested in this experiment was manufactured according to the principle that the hydrophobic core of the amylose molecule (linear, -[1-4] polyglucose) can trap the hydrocarbon chain of lipid molecules to form a lipid-amylose complex (Seneviratne and Biliaderis 1991). The carbohydrate portion of the V-complex is digested at a slower rate than that for free carbohydrates as determined by in vitro and in vivo assays (Biliaderis and Galloway 1989, Holm et al. 1983, Larsson and Miezis 1979, Seneviratne and Biliaderis 1991). Eliasson and Krog (1985) reported greater resistance to digestion of amylose-lipid complexes when amylose was complexed with long-chain, saturated monoglycerides (mix of 30% palmitic acid and 65% stearic acid) compared with complexes with shorter-chain unsaturated monoglycerides. A mix of monostearate and monopalmitate was complexed with debranched amylopectin to manufacture the V-complex that was incorporated into the experimental diet in this experiment. Also, during the manufacture of V-complex, the side chains of amylopectin were cleaved by a debranching enzyme and then complexed with lipid. This formed a shish kebab-like structure, unlike the helical structure formed when amylose is complexed with lipid.
). Rats fed wheat starch (11.5% resistant starch) for 4 wk digested 37.1% of the resistant starch in the total tract (Ranhotra et al. 1991). In rats, total tract digestibility of resistant starch of ordinary corn bread and high amylose corn bread were 60 and 10%, respectively (Granfeldt et al. 1993). In this study, total tract carbohydrate digestibility by dogs fed the resistant starch treatment was ~47 and 34 percentage units lower than for the control and V-complex treatments, respectively. Ileal and total tract digestibilities of carbohydrate for the V-complex treatment were intermediate. Molis et al. (1992) reported higher digestibility of complexed starch (88% high amylose cornstarch + 12% monoglycerides) than of retrograded starch (30% resistant starch) when fed to human subjects. It appears that the debranched amylopectin-lipid complex may have limited the availability of that portion of the carbohydrate to enzymatic action in the small intestine of dogs. Previous research has indicated low in vitro and in vivo digestibility of carbohydrate complexed with fatty acids (Holm et al. 1983, Seneviratne and Biliaderis 1991). Both ileal and apparent total tract digestibility of fat was lowest for the V-complex diet, possibly because a portion of the fat in the V-complex diet was trapped within a highly crystalline and poorly digested portion of the debranched amylopectin complex. Eliasson and Krog (1985) reported low total tract digestibility of fat when a portion of the dietary fat was complexed with amylose. This effect was more pronounced with the use of long-chain, saturated monoglycerides than with shorter-chain or more unsaturated fatty acids.
). Potentially fermentable substrates vary in their fecal bulking capacity. For example, Ranhotra et al. (1991) reported a 6- to 18-fold increase in fecal wet weight of rats fed wheat starch containing 11.5% resistant starch compared with rats fed wheat starch containing 0.5% resistant starch. Fecal dry weight for rats fed raw potato starch (3.5% resistant starch) and a resistant starch-enriched preparation (9.7% resistant starch) were 2.5 and 4.0 times higher than for those fed raw pea starch (0.2% resistant starch; Berggren et al. 1995). Increased fecal bulk for rats fed retrograded amylose as 10% of the diet was reported by Gee et al. (1992). In this study, fecal wet and dry weights for dogs consuming the control diet were ~75% less than for dogs fed the resistant starch or V-complex diets. Furthermore, fecal dry weights for dogs receiving the resistant starch diet were 59 g/d greater than for those consuming the V-complex diet. Feces of dogs fed the resistant starch diet were better formed than feces of dogs receiving either the control or V-complex diets. Fecal wet and dry weight data suggest that the fecal bulking capacity of the ingredients present in the resistant starch and V-complex diets was considerably greater than that present in the control diet.
-amylases, -glucosidases and -dextrinases), thereby influencing the overall rate of hydrolysis of amylose and amylopectin (Holm et al. 1983, McGilvery and Goldstein 1979). Furthermore, the rate of amylose and amylopectin digestion differs considerably. Hydrogen bonding among amylose units is considerably greater than that for amylopectin, thereby making amylose less available for enzymatic digestion (Tovar et al. 1990). In addition, because amylopectin is a larger molecule, it has a greater surface area for enzymatic digestion (O'Dea et al. 1980). Englyst et al. (1992) classified starch from several carbohydrate-containing foods as rapidly digestible, slowly digestible and resistant. A highly significant positive correlation was observed between the glycemic index and both the rapidly digestible starch and rapidly available glucose for thirty-nine carbohydrate-containing foods (Englyst et al. 1996). It is possible that the starch fraction of the diets in this study differed in concentration of rapidly digestible, slowly digestible and resistant starch. Patil et al. (1998) reported that dogs consuming a V-complex-containing diet had lower carbohydrate digestibility and subsequently lower serum glucose and insulin responses than dogs fed a carbohydrate-maltodextrin-containing control diet. Increased fecal wet and dry weight as a result of V-complex and resistant starch ingestion suggest good fecal bulking capacity of the experimental ingredients. Thus, V-complex and resistant starch may have a number of potential health benefits. A reduction in carbohydrate digestibility will lower the postprandial rise in serum glucose and insulin, which is important for individuals with diabetes and coronary heart disease. Furthermore, the delivery of carbohydrate to the colon may help to protect against colon carcinogenesis by increasing stool bulk and/or providing an indirect source of short-chain fatty acids (e.g., butyrate) (Kritchevsky 1986). In addition, when present in substantial amounts, nondigestible carbohydrate may lower the energy density of food, which may have implications in weight control. Last, incorporation of resistant starch into liquid diets and its ability to improve stool characteristics would be beneficial to people such as the institutionalized elderly or hypermetabolic hospitalized patients who are consuming liquid enteral formulas on a daily basis.
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FOOTNOTES |
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Manuscript received 5 December 1997. Initial reviews completed 28 January 1998. Revision accepted 9 July 1998.
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LITERATURE CITED |
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Abstract
Introduction
Methods
Results
Discussion
References
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-Amylase (EC 3.2.1.1) susceptibility rather than viscosity or gastric emptying rate controls plasma responses to starch in health humans.
Br. J. Nutr.
1990;
63:207-220[Medline]-amylases on amylose-lipid complex superstructures.
J. Cereal Sci.
1991;
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