Composition of enteral diets and meals providing optimal absorption rates of nutrients in mini pigs

BACKGROUND: Commercial enteral diets differ widely in nutrient composition. It is unknown whether the nutrient composition of the diets influences intestinal absorption. OBJECTIVE: The objective of this study was to investigate the effects of different enteral diets providing 60% of energy as carbohydrate, protein, or fat or 33.3% of energy from each nutrient on intestinal absorption in mini pigs. DESIGN: Kinetics of nutrient absorption were determined by perfusing a 150-cm jejunal segment. The kinetics of absorption were used to determine optimal relations between the absorption and recovery of each nutrient. From these data, the optimal nutrient composition of the diets providing complete absorption of the macronutrients in the shortest intestinal length was evaluated. Absorption of nutrients was further determined after oral administration of 4 corresponding meals. RESULTS: With all enteral diets, the absorption of nutrients displayed saturation kinetics. Absorption rates of carbohydrate were significantly larger than those of fat and protein. Consequently, the amounts of nutrients remaining unabsorbed per unit length of jejunum differed among the macronutrients. After administration of various test meals, the length of the small intestine required for complete absorption of the nutrients depended on the composition of the meals. The shortest intestinal length for complete absorption was needed for a diet providing 48% of energy as carbohydrate, 23% as protein, and 29% as fat. This composition closely matched the nutritional requirements. CONCLUSION: The nutrient composition of diets can optimize intestinal absorption. This may be especially important in patients with malabsorption or short-bowel syndrome.     

Two polyol,low digestible carbohydrates improve the apparent absorption of magnesium but not of calcium in healthy young men

The effects of nondigestible oligosaccharides including polyols on intestinal mineral absorption have been studied extensively in animal experiments, but their impact on mineral absorption in humans remains to be established. We investigated the effects of feeding two fermentable, low digestible carbohydrates, on the apparent absorption and balance of calcium (Ca) and magnesium (Mg) in humans. Nine healthy young men were given a control diet with dextrose or polyols, low digestible, fermentable carbohydrates (LHBC, HPFL) for 32-d periods according to a 3 x 3 Latin-square design. During the 18-d period of adaptation, the products were administered gradually in liquid form, up to a maximum of 100 g/d, which was then consumed for 14 d. Ca and Mg levels were measured in diets and in fecal and urine collections to assess apparent mineral absorption and balance. The relative apparent absorptions of Ca and Mg from the control diet were (means +/- SEM) 33.3 +/- 4.6 and 39.8 +/- 2.7%, respectively. Ingestion of both low digestible carbohydrates significantly increased the relative apparent absorption of Mg by about 25%. LHBC, but not HPFL, ingestion increased urinary Mg excretion. Apparent absorption, urinary excretion and balance of Ca were not altered by the ingestion of either low digestible carbohydrate. Ingestion of the low digestible, fermentable carbohydrates, with balanced diets, improved apparent Mg absorption without significant effects on apparent absorption or retention of Ca in healthy young men. Further human studies are therefore still needed to confirm the effects of these products in other populations.     

Objective verification of dietary intake by measurement of urine osmolality

A new method for assessing the accuracy of dietary nutrient intakes in metabolic studies is described. The theoretical basis of the method is the comparison of measurements of the urine osmole excretion rate (OER, the product of urine osmolality and urine weight) with values for OER predicted from dietary nitrogen, sodium, and potassium. The method was tested in 34 healthy male and female volunteers aged 18-78 y who made complete 24-h urine collections and consumed a diet over 6 d in metabolic-balance studies involving either overfeeding, weight maintenance, or weight loss. The coefficients of variation for equations relating measured OER to dietary nitrogen, sodium, and potassium intakes ranged from 14.1% for 1-d measurements to 6.94% for 6-d means. These results indicate that it should be possible to use measurements of the urine OER to identify dietary noncompliance in metabolic studies.     

Effect of oat bran muffins on calcium absorption and calcium, phosphorus, magnesium and zinc balance in men.

Metabolic balance studies were conducted in adult human males to investigate the effect of oat bran on the nitrogen, calcium, phosphorus, magnesium and zinc balance, on the intestinal absorption of calcium and on the endogenous fecal calcium, using 47CaCl2 as the tracer. A 40-d control period preceded a 32-d experimental period in which subjects consumed four oat bran muffins daily as part of a constant metabolic diet. No significant changes in the calcium, magnesium or zinc balances were observed, but the nitrogen and phosphorus balances increased. The net or apparent absorption of nitrogen, magnesium and phosphorus expressed per milligram of intake increased significantly in the oat bran period due to the added content of these nutrients in the oat bran muffins. The intake of the oat bran muffins led to a significant increase in urinary phosphorus and significant decreases in urinary calcium and 47Ca excretions. The intestinal absorption of calcium, determined with 47Ca, did not change, whereas the endogenous fecal calcium increased slightly but significantly.     

Carbohydrate intake is the main determinant of growth in infants born <33 weeks' gestation when protein intake is adequate

OBJECTIVE: We investigated the relative contribution of macronutrients to postnatal growth in preterm infants born <33 wk of gestation. METHODS: An audit of daily parenteral and enteral intakes of protein, carbohydrate, fat, energy, and growth (daily weight, weekly length, and head circumference) from birth to discharge home in 138 infants at <33 wk of gestation admitted to an Australian tertiary hospital was done. A mixed-model analysis of variance with random effects (slope and intercept) for subject and controlling for time, sex, gestational age, and total energy was used to determine the relative contribution of macronutrients to growth. RESULTS: A higher energy intake (kilocalories per day) had a positive influence on growth. With total energy held constant, the contribution of carbohydrate to total energy had a positive relation to weight, length, and head circumference gains; protein had no relation and fat was negatively associated. For every 1% increase in energy from carbohydrate, there was a 2.3-g/d increase in weight (95% confidence interval 1.6-3.0, P < 0.0001), a 0.013-cm/d increase in length (95% confidence interval 0.003-0.022, P = 0.007), and a 0.015-cm/d increase in head circumference (95% confidence interval 0.009-0.022, P < 0.0001). CONCLUSION: A re-examination of the macronutrient balance in the diet of preterm infants is required in relation to optimizing growth.     

Various macronutrient intakes additively stimulate protein synthesis in liver and muscle of food-deprived chicks

We investigated the influence of refeeding food-deprived chicks with either protein, carbohydrate, fat or combinations thereof on the rates of liver and muscle protein synthesis. After 2 d of food-deprivation, chicks were given individual or mixed protein, carbohydrate and fat. At 30 min after refeeding, the protein fractional synthesis rate (K(s)) was measured by a large dose injection of L-[2,6-(3)H]phenylalanine. When chicks were food-deprived for 2 d, liver K(s) was 67% lower and muscle fractional synthesis rate was half that of well-fed controls. Upon refeeding starved chicks a complete diet, K(s) in the liver and muscle returned to the level of fed controls within 30 min. When food-deprived chicks were refed protein alone or two of the three macronutrients, liver and muscle K(s) were significantly higher than those in the starved group. There was no effect of refeeding with carbohydrate or fat alone. Plasma glucose concentration was significantly greater than in fed or starved groups in chicks refed the complete diet, carbohydrate or carbohydrate mixed with either protein or fat. Refeeding chicks with the various macronutrients did not affect the plasma insulin or insulin-like growth factor-I concentrations. These results suggest that intakes of individual macronutrients additively increase liver and muscle protein synthesis and that the acute increase in muscle protein synthesis after refeeding chicks diets containing the three macronutrients was mainly regulated by the change in ribosomal efficiency.     

Validation of a semiquantitative food frequency questionnaire to assess energy and macronutrient intakes of Cuban Americans

OBJECTIVE: To assess the validity of a 131-item semiquantative food frequency questionnaire (FFQ) by comparison with multiple food records in Cuban Americans. DESIGN: The Willet FFQ was administered and food consumptions of three random days (two weekdays and one weekend day) were collected. SETTING: Cuban Americans residing in Miami. PARTICIPANTS: Twenty adult Cuban American volunteers who participated in a larger epidemiological study to evaluate the dietary risk of type 2 diabetes and cardiovascular disease. RESULTS: There were no significant differences in the mean intakes of energy, macronutrients, cholesterol and alcohol estimated by the Willett FFQ and the 3-day food records. For most of the macronutrients the correlation coefficients ranged from 0.14 to 0.71. The correlation coefficient was highest for polyunsaturated fatty acid (r = 0.71, P<0.001) and lowest for protein (r = 0.14, P=0.56). Correlation coefficients for carbohydrate (r = 0.42) and monounsaturated fatty acid (r = 0.43) were only marginally significant (P=0.06). CONCLUSION: Compared with 3-day food records, the Willett FFQ is a reasonable instrument to assess the intakes of most macronutrients and alcohol among Cuban Americans. Further studies should be conducted to validate the usefulness of the Willett FFQ in Cuban Americans for other nutrients.     

Number of days required for assessing usual nutrient and antioxidant intakes in a sample from a U.S. healthy college population

ObjectiveThe primary aim of this study was to determine the number of days required to assess usual antioxidant intake with a defined level of accuracy in a sample of healthy college students. The secondary aim of this study was to increase the validity of the calculation of days by first determining the prevalence of misreporting energy intake in 30-d food records (FRs).MethodWe examined the percentage of misreporting, the within- and between-person variations of nutrient intake, and the minimum days required to estimate a person's true intake with a correlation coefficient r ≥ 0.9. Sixty students from the University of Connecticut completed a 30-d FR, which was analyzed using the Nutrition Data System for Research software combined with Flavonoid and Proanthocyanidin Provisional Table.ResultsTwenty-seven percent (44 average reporters) included in the dietary analysis misreported after applying the Goldberg cutoff equation. The within-person variation was greater than the between-person variation with the variance ratios ranging from 1.10 to 10.51. After adjusting for energy and sex, a 7-d FR was adequate to achieve r ≥ 0.9 for fat, carbohydrate, protein, lycopene, and proanthocyanidin, whereas α-tocopherol, total carotenoids, and flavonoids required 8 d. The remaining antioxidants required between 10 and 45 d.ConclusionsOverall, micronutrients and antioxidants had a greater daily variation than macronutrients and the majority required more than 7 d to assess usual intakes for this population.     

Effects of malnutrition during early lactation on development and feeding behavior under the self-selection paradigm

Selection of food can be affected by several factors, and with the method of self-selection, qualitative changes in nutritional balance may be detected. The goal of the present study was to evaluate feeding preferences in weaning rats using three macronutrients (protein, carbohydrate, and fat), through a free-choice method, evaluating the alteration in their feeding patterns as compared with the previous nutritional status during the early lactation period. We analyzed the effects of protein restriction during lactation over the nitrogen balance after the weaning. The dams were assigned to one of two diet conditions (nourished or malnourished). At weaning, two pups from each litter were housed individually in metabolic cages, and they were maintained on self-selection under a free-choice paradigm and were provided with separate sources of macronutrients. The parameter for evaluating the nutritional effectiveness of the diets was nitrogen balance. We observed that protein intake tended to increase and consumption of carbohydrate and fat tended to decrease progressively during the 3 wk of experiment. In selecting their own food, growing rats and malnourished rats consumed a larger amount of protein than the other rats. Nourished rats selecting their diet had a larger nitrogen balance than nourished rats receiving a composed diet; no nitrogen balance difference was found between the self-selecting groups. Rats can choose an adaptive form when recovering from protein malnutrition.     

3-0 methylglucose absorption in vivo correlates with nutrient absorption and intestinal surface area in experimental short bowel syndrome

BACKGROUND: Inert carbohydrate probes are widely used to study intestinal permeability and examine the passive uptake of markers. This study examined the use of quantifying 3-0 methylglucose (3-0 MG) absorption as a marker of intestinal surface area and active nutrient transport capability. METHODS: Using a rat model, varying degrees of short bowel syndrome (SBS) were induced: sham operation (intestinal transection only), 50% resection (R50), 75% resection (R75), and 90% resection (R90; n = 6 to 8 in each group). Animals were pair fed, and over days 5 and 6 postoperation, a balance study was done to quantify absorption of dietary fat, protein, and carbohydrate. On day 7, animals were gavaged with the test solution containing 3-0 MG, lactulose, and mannitol, followed by a 16-hour urine collection. Urine recovery of probes was quantified using high-performance liquid chromotography. Animals were then killed, and the gross and microscopic intestinal morphology was determined. RESULTS: As expected, increased resection resulted in reduced absorption of dietary nutrients and 3-0 MG, which reached significance in the R90 resected animals. 3-0 MG absorption was significantly correlated with intestinal surface area and the absorption of dietary protein and fat (p < .01 for all comparisons). Interestingly, 3-0 MG absorption was not significantly correlated with the absorption of dietary carbohydrate. CONCLUSIONS: 3-0 MG absorption is a useful marker of functional intestinal surface area and of the absorption of dietary fat and protein in experimental SBS. 3-0 MG may be a useful marker of nutrient absorptive capacity in patients with SBS; further study is indicated.     

中国成年居民营养素摄入状况的评价

目的使用ISU方法计算营养素的日常摄入量(UI),评估中国成年居民的营养素摄入状况。方法使用"2002年中国居民营养与健康状况调查"数据,采用美国爱荷华州立大学(Iowa State Unirersity,ISU)方法计算43 672名成年居民的碳水化合物、蛋白质、钙、铁、锌、硒、镁、维生素B1和维生素B2的UI,并将UI与平均需要量(EAR)比较,评估这些营养素摄入不足的比例;将宏量营养素供能比的UI与可接受宏量营养素分布范围(AMDRs)或适宜摄入量(AI)比较,评估宏量营养素摄入是否合理。结果我国成年居民碳水化合物和蛋白质供能比UI均值均在推荐范围之内,脂肪供能比UI均值稍高于AI上限;碳水化合物供能比低于AI下限的比例约为40%,蛋白质供能比低于AMDRs下限的比例约为20%,脂肪供能比高于AI上限比例约为50%。我国成年居民钙、锌、硒、镁、维生素B1和维生素B2摄入不足比例均较高,其中钙摄入不足的比例超过95%,维生素B1和维生素B2摄入不足的比例均达到了80%以上。结论我国成年居民宏量营养素供能比例不合理,膳食钙、锌、硒、镁、维生素B1和维生素B2摄入不足状况较为严重。     

Short-term orlistat treatment does not affect mineral balance and bone turnover in obese men

Orlistat is a gastrointestinal lipase inhibitor that is used to reduce dietary fat absorption and to enhance weight loss in subjects consuming a hypocaloric diet. To assess whether orlistat has an effect on the metabolism of six minerals, a 21-d, double-blind, randomized, parallel-group, placebo-controlled mineral balance study was conducted in obese (body mass index > 30 kg/m(2)) men. Subjects consumed a hypocaloric diet with a constant daily mineral content and received daily oral treatment with orlistat (120 mg three times daily) (n = 14) or placebo (three times daily) (n = 14) for 21 d. After a 14-d equilibration period, calcium, phosphorus, magnesium, iron, copper and zinc balances were assessed for d 15-21. In addition, the effect of diet and orlistat treatment on bone metabolism was estimated from measurement of biomarkers of bone formation and bone resorption. Serum and urine electrolytes were also measured at baseline and at the end of treatment. Orlistat inhibited fat absorption by approximately 33% (P < 0.05). There were no significant differences in mineral apparent absorption, urinary mineral loss or mineral balance between the orlistat and placebo groups. Markers of bone turnover and serum and urine electrolytes did not differ between the orlistat and placebo groups. Orlistat was well tolerated; adverse events were of mild or moderate intensity, and the majority of these events were unrelated or remotely related to study treatment. In obese men consuming a hypocaloric diet, the administration of orlistat had no significant effect on the balance of six selected minerals. In addition, biomarkers of bone turnover, as well as serum and urine electrolytes, were not affected by orlistat treatment.     

Diet composition and body composition in preschool children

BACKGROUND: In studies of adult humans and in animal models, dietary intakes of the macronutrients, particularly fat, are related to body composition; however, data on children are more scarce. OBJECTIVE: We sought to determine whether diet composition is related to percentage body fat in children aged 1.5-4.5 y. DESIGN: In 77 preschool children, a 4-d weighed-food record was used to determine intakes of total energy and energy from each macronutrient. An oxygen-18 dilution method was used to calculate percentage body fat. Habitual physical activity level was determined by calculating the ratio of total energy expenditure (from stable isotope analyses) to predicted basal metabolic rate. Dietary intake and body-composition data were analyzed to evaluate whether diet composition was related to body fat. Further analyses incorporating physical activity level were performed. RESULTS: Percentage body fat was not significantly correlated with dietary intake variables (total energy or percentage of energy from fat, carbohydrate, or protein) and did not differ significantly among 3 increasing levels of each dietary intake variable by analysis of variance. In multiple regression analysis, physical activity level was related to body fat whereas diet composition was not. CONCLUSIONS: We found no relations between dietary intakes of total energy, fat, carbohydrate, or protein and percentage body fat in children. The relation between fat intake and body fat may develop over time and may not be evident in preschool children. Energy expenditure, in particular physical activity level, may have a greater influence on body composition in early childhood.     

Absorption and retention from an iso-osmolal casein hydrolysate infant formula

Pregestimil^®, the control formula, and Nutramigen^®, a casein hydrolysate formula, further modified to reduce osmolality from 443 to 300 m0sm/kg water, were well accepted and tolerated while supporting adequate growth and maintaining normal serum albumin levels in six recovering malnourished infants. Stool characteristics were similar in both groups. An apparent nitrogen absorption of 88±4% of intake was observed for both products with apparent nitrogen retention rates of 39±8 and 43±6% for the control and test products, respectively. Mean fat absorptions exceeded 93% of intake for both products and carbohydrate absorption was practically complete as confirmed by the absence of significant peaks in the breath hydrogen determinations. Dry stool weights and fecal excretions of energy, fat and carbohydrate were modestly but significantly higher with reformulated Nutramigen^® than with Pregestimil^®, however, no clinical effects were noted in this infant population.     

Apparent small intestinal absorption of nitrogen and minerals from soy and meat-protein-based diets. A study on human ileostomy subjects

The apparent absorption of nitrogen and minerals was studied in 8 ileostomy subjects. Four different test diets containing 60 g of meat, rice and bread protein, or a 25% replacement of the protein with soy flour, soy concentrate or soy isolate, were randomly assigned to the subjects in 2-d periods. All animal protein was replaced by soy isolate for a fifth 2-d period in two of the subjects. Ileostomy contents were collected in 2-h intervals during the day and in one portion during night and immediately deep-frozen. The fiber components and the phytic acid in the diet were almost completely recovered in the ileostomy contents, whereas unabsorbed starch was less than 2% of the intake. A significantly lower protein digestibility was observed when the diets containing soy protein were fed. No difference in protein digestibility was found between the different soy protein products. A 25% replacement by soy protein had no obvious effect on apparent mineral absorption. A low protein digestibility was also observed when soy was the main source of protein, and a negative apparent absorption of zinc was found in both subjects. Although 25% of soy protein in the diet does not seem to impair mineral absorption significantly, small intestinal net absorption of nitrogen is less from the soy diets than from the meat diet.     

Energy, macronutrient and fatty acid intake of French elderly community dwellers and association with socio-demographic characteristics: data from the Bordeaux sample of the Three-City Study

Few data are available regarding dietary habits of the elderly, in particular about fatty acid consumption, whereas these are major risk or protective factors of several age-related diseases. The aim of the present study was to characterise the dietary intake of a French elderly population in terms of energy, macronutrients and fatty acids based on their socio-demographic characteristics. The study population (age range 67.7-94.9 years) consisted of 1786 subjects from Bordeaux (France), included in the Three-City cohort. Dietary assessment was performed by a 24 h recall, allowing the estimation of energy, protein, carbohydrate, total fat, SFA, MUFA and PUFA intakes. Socio-demographic characteristics (age, sex, marital status, educational level and income), practice of sports and BMI were registered. Total energy intake (EI) was lower in women and in older participants ( > or = 85 years) but higher in single subjects. Higher EI was associated with higher income, but not with educational level. Mean contribution of macronutrients to EI (protein 18%, carbohydrate 46% and total fat 31%) was higher in women than men, except for alcohol. The oldest individuals consumed less protein and more mono- and disaccharides. Excess saturated fat intake (43% of total fat), associated with a relative deficit in MUFA consumption (36% of total fat), was observed. The mean 18:2n-6:18:3n-3 ratio was 9.9 and decreased with higher educational level. The present results suggest that being female, older age, being widowed and low income level could be considered as risk factors of inadequate dietary intake.     

What are the major correlates of macronutrient selection in Western populations?

In order to better understand the factors that may influence and regulate the intake of the macronutrients carbohydrate, fat and protein a 7 d diet diary technique was employed to study eating behaviour in the natural environment of free-living human subjects. In general, factors that promote energy intake tend to promote fat and protein intake to a greater extent than carbohydrate intake. This increased intake occurs as the result of: environmental factors such as social facilitation and the time of day, week or lunar phase; subjective factors such as hunger and elation; individual difference factors such as obesity, restraint and ageing. There are indications that the intake of macronutrients is regulated by negative feedback systems. In the short term, the amount of protein remaining in the stomach at the onset of a meal appears to have a restraining effect on intake, especially protein intake. Over several days, macronutrient intake appears to be affected by a nutrient-specific delayed negative feedback. Protein intake during 1 d is negatively associated with protein intake 2 and 3 d later, while carbohydrate intake is negatively related to later carbohydrate intake, and fat intake to later fat intake; both peaking after a 2 d delay. Studies of the intakes of twins suggested that many aspects of the control of macronutrient intake are influenced by inheritance; these factors include the overall amounts ingested, the before-meal stomach contents and the responsiveness of the subject to the negative impact of the stomach contents. The results indicate that macronutrient intakes are regulated by multiple persistent processes that are to a large extent inherited.     

Gastrointestinal and cardiac response to low-calorie semistarvation diets

Effects of low-calorie semistarvation diets on gastrointestinal and cardiac organ systems were studied. Male Sprague Dawley rats were divided into two groups, Group I, control (C) and Group II, semistarvation (SS), and maintained on a diet designed after low-calorie modified-fasting regimens in popular use. C animals consumed this diet ad libitum; SS animals received 23% of the total calories of C but the same ratio of calories from protein, carbohydrate, and fat and the same quantity and quality of all essential nutrients. Final weights of total body, heart, liver, and small intestine were lower in SS than in C animals. Protein depletion in SS compared with C animals was evident for heart, pancreas, and intestinal mucosa. Unless aggressively supplemented, low-calorie SS diets may deplete protein stores of the gastrointestinal organs of digestion and absorption and contribute to decrease in body nitrogen stores, specifically cardiac muscle.     

Effect of amounts consumed on the digestion of cassava by young children

To determine whether increasing proportions of cassava could be consumed and satisfactorily digested, eight recovering malnourished children (20-38 mo old) received 25, 50 and 75% of their diet energy as freeze-dried cassava flour during 9-d periods, with intervening casein control diets. Enough casein was added to all cassava diets to bring protein energy to 8% of the total. When compared to the control diet, the 25% diet had no significant effect on consumption time or measures of protein and energy digestion. With the 50% diet, fecal wet and dry weights were moderately higher than with the 25% diet (196 +/- 44 and 24 +/- 4 vs. 121 +/- 36 and 16 +/- 3 g/d, respectively), as were fecal energy (89 +/- 16 vs. 63 +/- 16 kcal/d) and calculated carbohydrate (11 +/- 2 vs. 5 +/- 1 g/d); apparent nitrogen absorption (mostly from casein) was slightly lower (79 +/- 5 vs. 83 +/- 6%) and consumption time slightly higher (5-25, median 10, vs. 4-18, median 6 min/feeding). When energy from cassava was increased to 75%, fecal weights (240 +/- 49 and 31 +/- 5 g/d), energy (124 +/- 27 kcal/d) and carbohydrate (16 +/- 4 g/d) were all higher than when cassava provided 50 or 25% of energy. Consumption required 8-34, median 17 min/feeding and apparent nitrogen absorption was 76 +/- 6% of intake.(ABSTRACT TRUNCATED AT 250 WORDS)     

The contribution of the large intestine to energy supplies in man

Herbivores obtain a considerable proportion of energy requirements from carbohydrate by the chain of anaerobic carbohydrate fermentation producing short-chain fatty acids that are absorbed then metabolized. The evidence for this sequence occurring in the large intestine of man is reviewed and estimated to produce 5 to 10% of human energy requirements. Further small amounts of energy may come from large intestinal absorption of fat and the bacterial breakdown products of protein.