Excess Dietary Protein Research Articles

Diets for patients with chronic kidney disease, still worth prescribing.

Dietary indiscretion contributes to the severity of many diseases such as inherited metabolic disorders like phenylketonuria in which excess dietary protein causes symptoms. But, dietary indiscretion also causes symptoms in more common diseases. For example, excessive carbohydrate intake will

GROWTH IN AN ARCTIC GRAZER: EFFECTS OF SEX AND DIETARY NITROGEN ON YEARLING MUSKOXEN

Abstract Muskoxen (Ovibos moschatus) are sexually dimorphic ruminants from a highly seasonal environment. Five males and 4 females were assigned at the start of spring (309 days) to supplemental diets of either 12.8% or 25.1% protein with ad libitum grass hay (9.1% protein). Males grew more rapidly than females especially in the 2nd autumn (0.29 versus 0.15 kg/day) but returned to slow growth in the next winter (0.09 kg/day). Water space (3H2O) grew from 62 to 94 kg, whereas fat increased from 1.36% to 16.52% of body mass from 312 to 522 days of age. Depth of subcutaneous fat was greater on the high nitrogen (N) supplement, which indicated deposition of excess dietary protein as lipid. Differences in protein content and 15N enrichment of the supplements did not affect density, composition, or enrichment of hair, which indicated minimal incorporation of supplemental protein into lean mass and a low requirement of N for growth. Low body fat may impair survival of muskoxen during the 1st winter, whereas gain...

Effect of dietary protein level, amino acid balance and feeding level on growth, gastrointestinal tract, and mucosal structure of the small intestine in broiler chickens

In a factorial experiment, two series of feeds containing excess dietary protein, differing in amino acid balance (i.e. balanced (BPS) and unbalanced (UPS) amino acid mixture), and with a range of protein contents (400, 300 and 200 g CP·kg -1 ) at the same energy content of 13 MJ AME·kg -1 were offered at two levels of feeding (ad libitum or 0.75 of ad libitum intake) to 4320 broiler chickens between 10 and 24 days of age. Growth rate was significantly lowered by feed restriction. There was also a significant (P < 0.001) effect of dietary protein on the combined weight of the proventriculus and gizzard but only for the birds on the restricted feeding regime. Relative pancreatic weight in- creased (P < 0.001) with an increase in dietary protein level for the birds fed restricted amounts of BPS. The crypt depth of chicks on the ad libitum feeding regime was higher (P < 0.01) for the chicks on the BPS than for those on the UPS diet. The protein content of the jejunal mucosa was higher (P < 0.001) for birds fed ad libitum on the UPS diet than on the BPS diet. Daily feed allocation had a significant (P < 0.01) effect on jejunal protein content in birds that received the BPS diet, this being reduced in birds on restricted feeding. Maltase (P < 0.001) and sucrase (P < 0.01) activities were sig- nificantly reduced in chicks offered ad libitum access to the UPS diet. At high dietary CP, the specific activity of alkaline phosphatase was lower (P < 0.001) in chicks on the UPS diet than in those fed the BPS diet.

Elderly women need dietary protein to maintain bone mass.

Excess dietary protein is considered a risk factor for osteoporosis owing to the potential for renal acid load. Researchers who conducted a recent prospective study of older adults reported that animal protein had a protective role for bone, especially in elderly women, whereas plant protein was negatively associated with bone mineral density. An interaction between protein and calcium suggested protein alone was not the important factor. Other studies confirm the beneficial effect of increasing dietary protein intake in older women to reduce bone mineral density loss and risk of fracture, suggesting that emphasis should be placed on promoting adequate protein intake in elderly women.

Chronic diazinon exposure: pathologies of spleen, thymus, blood cells, and lymph nodes are modulated by dietary protein or lipid in the mouse

Little is known about the immunotoxicity of the organophosphate pesticide, diazinon. This study aims at detailing the pathologies in the thymus, spleen, blood cells, and lymph nodes (brachial, mesenteric, and hind quarter gluteal nodes) during chronic oral exposure (300 mg diazinon kg −1 food for 45 days), and explore the combined toxicity with excess dietary protein (40%) or lipid (20% corn oil). Animals were allowed to recover on normal food for 2 weeks. All experimental treatments caused organ pathologies, including necrotic degeneration of the trabeculae (spleen and thymus), hyperplasia of the cortex and medulla (thymus and lymph nodes), hyperplasia of white and red pulp (spleen), and sometimes haemorrhage (all tissues). Blood smears often showed crenated/hypochromic red cells and vacuolated white cells with abnormal nuclei. The severity of lesions during exposure was generally in the following order: lipid<protein<diazinon alone<protein plus diazinon<lipid plus diazinon. Post-exposure recovery was limited, especially in the thymus and for lipid treatments. Quantitative image analysis revealed treatment and organ-specific changes in the proportions of fixed lymphocytes, PAS-positive carbohydrates, DNA, and protein staining. Histochemical changes were greatest after exposure. We conclude that the immunotoxicity of diazinon is exacerbated by excess dietary protein or lipid. The limited recovery and post-exposure histochemical changes imply deleterious effects on metabolism with oxidative stress after exposure.

Protein catabolism in mosquitoes: ureotely and uricotely in larval and imaginal Aedes aegypti

Catabolism of excess dietary protein by Aedes aegypti was investigated during larval development, during and after metamorphosis. Activity profiles were established for xanthine dehydrogenase (XDH, uricotelic pathway) and arginase (ureotelic pathway). Both enzymes are active at all times during the life-cycle. During the aquatic larval and pupal instars, XDH and arginase activities increase with body size. Maximal activities of these two enzyme systems coincide with the time of metamorphic restructuring. Both enzymes are found in the fatbody tissue: XDH activity is found in 80% of the tissue, while arginase activity is distributed equally between abdominal fatbody and the thorax. This might indicate a role for arginase other than catabolic, such as energy metabolism. Arginase activity is high in the aquatic instars and low in sugar-fed females but increases after blood-feeding. XDH activity, also high in larvae and pupae, increases markedly after a blood meal. Larval excretion is characterized by the ureotelic pathway. The pupae as closed systems excrete neither uric acid nor urea; urate accumulates during larval and pupal periods, is conserved throughout metamorphosis, and is finally voided with the meconium by the teneral imago. This presents a form of transient storage–excretion.

Protein supplementation of human milk for promoting growth in preterm infants

For term infants, human milk provides adequate nutrition to facilitate growth, as well as potential beneficial effects on immunity and the maternal-infant emotional state. However, the role of human milk in preterm infants is less well defined as it contains insufficient quantities of some nutrients to meet the estimated needs of the infant. Preterm infants require higher protein intakes than term infants to attain adequate growth rates, and have relatively higher protein turnover rates. Inadequate protein intakes may be partly responsible for low serum albumin and blood urea concentrations in preterm infants. The main objective was to determine if addition of protein to human milk leads to improved growth and neurodevelopmental outcomes without significant adverse effects in preterm infants. The standard search strategy of the Cochrane Neonatal Review Group was used. This includes searches of the Oxford Database of Perinatal Trials, MEDLINE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, and journal handsearching mainly in the English language. All trials utilizing random or quasi-random allocation to supplementation of human milk with protein or no supplementation in preterm infants who remained in hospital were eligible. Data were extracting using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk and weighted mean difference. Protein supplementation of human milk results in increases in short term weight gain (WMD 3.6 g/kg/day, 95% CI 2.4 to 4.8 g/kg/day), linear growth (WMD 0.28 cm/week, 95% CI 0.18 to 0.38 cm/week) and head growth (WMD 0.15 cm/week, 95% CI 0.06 to 0.23 cm/week). There are insufficient data to evaluate long term neurodevelopmental and growth outcomes. There are too few infants studied to be certain that adverse effects of protein supplementation are not increased. Blood urea levels are increased (WMD 1.0 mmol/l, 95% CI 0.8 to 1.2 mmol/l). Protein supplementation of human milk in relatively well preterm infants results in increases in short term weight gain, linear and head growth. Urea levels are increased, which may reflect adequate rather than excessive dietary protein intake. Further research should be directed towards the evaluation of specific levels of protein intake in preterm infants and the clinical effects of supplementation with protein, including long term growth and neurodevelopmental outcomes. This may best be done in the context of refinement of available multicomponent fortifier preparations.

Does excess dietary protein improve growth performance and carcass characteristics in heat-exposed chickens?

The effects of two environmental temperatures (22 and 32 C, constant) and five dietary protein contents (10 to 33% CP) were investigated in 4- to 6-wk-old broiler chickens. High ambient temperature reduced growth rate, feed efficiency, and breast muscle proportion and increased abdominal fat proportion. Irrespective of ambient temperature, increasing dietary protein content improved growth performance and carcass characteristics. At 32 C, there was a greater heterogeneity of the data, and bird responses were lower than at 22 C. We concluded that under conditions of chronic heat exposure, diets containing the highest protein levels, 28% and 33% compared with 20% CP, slightly improved chick performance. However, the effect was low and, in our experimental conditions, modifying dietary protein supply (variations in the total quantity of protein) is not sufficient to help broilers to withstand hot conditions.

Evaluation and management of urea cycle disorders using stable isotope infusions

Diagnosing partial urea cycle deficiencies based on clinical and laboratory data is difficult and there is often poor correlation between genotype, in vitro enzyme activity, and phenorypic expression. We have used stable isotope infusions to measure total body glutamine and urea flux for the evaluation of patients with urea cycle disorders. We have previously determined the rate of total body urea production by measuring blood 13C-urea isotopic enrichment during an infusion with the stable isotope 13C-urea, and the proportional contribution of peripheral nitrogen to urea synthesis by measuring the incorporation of 15N from 15N glutamine into 15N urea. The ratio of the isotopic enrichments of 15N urea/15N-glutamine (15N-U/G) allowed us to distinguish carriers for omithine transcarbamylase deficiency (OTCD) both from their affected offspring and from normal control subjects (Lee et. al., submitted). Collectively these data suggest that the flux from 15N glutamine to 15N urea is a sensitive measure of urea cycle activity and is capable of differentiating female carriers for OTCD from normal controls.We have now applied this method to the 1) diagnosis of asymptomatic at risk partial OTCD females, 2) titration of dietary protein tolerance for managing a severe OTCD male patient, and 3) comparison of differences in the bioavailability of enteral vs. systemic sources of nitrogen for total body urea production. By determining the 15N-U/G ratio in 5 at-risk females in two OTCD sibships in whjch mutations were not found in the index case, we were able to measure normal and abnormal urea production and determine carrier status. In the second case, we determined total body glutamine flux at 1.2 gm/kg/day and at 0.8 gm/kg/day protein intake in a 7 month null activity OTCD male to titrate protein tolerance and guide dietary therapy. In the third case, we tested the hypothesis that intestinally generated ammonia and alanine are more effective immediate precursors for urea synthesis than peripherally generated glutamine and as a consequence individuals who have a compromised urea cycle activity would metabolize excessive dietary protein more effectively than peripherally generated protein. By comparing the transfer of 15N from oral and intravenous 15NH4Cl to urea, we found that individuals who have partial urea cycle activity metabolize excessive dietary protein more efficiently, underlying the observation thai these patients are particularly susceptible to stress and fasting. In conclusion this approach may also lead to improvements in the nutritional management of patients with urea cycle defects and those who are severely catabolic during critical illness.

Crude Protein and Rumen Undegradable Protein Effects on Reproduction and Lactation Performance of Holstein Cows

We conducted a study to determine the effects of excess dietary crude protein (CP) and rumen undegradable protein (RUP) on reproduction and lactation performance of Holstein cows. During each of three yearly replicates, cows were blocked by previous mature equivalent milk production and randomly assigned at calving (n=47; partum group) or at 42±21 d postpartum (n=134; postpartum group) to the following dietary treatments: 1) ryegrass pasture supplemented with a corn and soybean meal grain mix (high CP, moderate RUP); 2) ryegrass pasture mornings and corn silage evenings, supplemented with grain as in diet 1 (moderate CP, moderate RUP control diet), and 3) ryegrass pasture mornings and corn silage evenings, supplemented with a grain mix containing corn, soybean meal, corn gluten meal, and blood meal (moderate CP, high RUP). Dietary CP and RUP concentrations were approximately 23.1, 5.8; 17.7, 5.0; and 17.2, 6.8% of dry matter for diets 1 to 3, respectively. Plasma urea N concentrations were highest in cows fed diet 1 (25.0 mg/dl), intermediate in cows on diet 2 (20.1 mg/dl), and lowest in cows on diet 3 (18.5 mg/dl). Cows fed excess dietary protein (diet 1) exhibited lower first breeding pregnancy rates (24.1 vs. 41.0%) and lower overall pregnancy rates (53.4 vs. 75.4%) than did cows fed diet 2, increasing time nonpregnant by an average of 15.1 d per cow. Reproductive performance was similar between cows fed diets 2 and 3. Mean fat-corrected milk (FCM) yield was not affected by protein concentration (diet 1 vs. 2); however, partum group cows that received supplemental RUP (diet 3) produced more 3.5% FCM than controls in early lactation. Feeding grain diets that contained excess dietary protein impaired the reproductive performance of dairy cows grazing ryegrass.

Growth Responses, Tissue Composition, and Liver Enzyme Changes in Juvenile Sunshine Bass, Morone chrysops × M. saxatilis, Associated with Dietary Protein and Lipid Level

ABSTRACT Four isocaloric, semi-purified diets containing low (30%) or high (50%) protein with either 12 or 18% lipid were fed at 4% of body weight to juvenile sunshine bass, Morone chrysops ×M. saxatilis, for 12 weeks (initial weight = 3.4 g). Fish fed the high protein diets gained significantly more weight and had better feed conversions than fish fed low protein diets. There were no significant differences in muscle or total body moisture and lipid or in intraperitoneal fat associated with either dietary protein or lipid levels. However, muscle protein and liver lipid increased significantly at high protein and lipid levels, respectively. Liver alanine amino transferase activities increased significantly at the high dietary protein and lipid levels, indicating that excess dietary protein was being used for non-protein processes. Fruc-tose-1,6-diphosphatase and pyruvate kinase activities indicated that excess dietary protein was not being used to synthesize glucose or glyco-gen. Malic enzyme activities decreased in response to increased dietary lipid, but did not respond to changes in dietary protein, indicating that excess protein was not being used for lipid synthesis. It is hypothesized the excess dietary protein is used for energy production.

Nutrition and chronic renal failure in rats: what is an optimal dietary protein?

In chronic uremia (CRF), malnutrition is an important determinant of morbidity in adults and impaired growth in children. Causes of malnutrition include anorexia and abnormal protein and amino acid metabolism. To determine how different levels of dietary protein and CRF interact to influence growth and nutritional status, CRF and sham-operated, pair-fed control rats were fed isocaloric diets containing 8, 17, or 30% protein for 21 d to mimic dietary regimens recommended for CRF patients: the minimum daily requirement; the recommended daily allowance; or an excess of dietary protein. Serum creatinine did not differ between groups of CRF rats but blood urea nitrogen was lowest in CRF rats fed 8% protein (P < 0.001). CRF rats eating 30% protein gained less weight and length compared to their controls or CRF rats fed 8 or 17% protein (P < 0.05); they also had acidemia. CRF rats fed 8% protein had the highest efficiency of utilization of protein for growth, while 17% protein promoted the highest efficiency of utilization of food and calories for growth. Notably, CRF rats eating 30% protein had the lowest protein efficiency; their calorie intake was also the lowest because of anorexia. Plasma branched-chain amino acids were progressively higher in control rats eating 8, 17, or 30% protein. CRF rats fed 8 or 17% protein had lower branched-chain amino acid concentrations compared with CRF rats fed 30% protein. In CRF, it is concluded that excessive dietary protein impairs growth but a low-protein diet does not impair nutritional responses and permits utilization of protein for growth if calories are sufficient.

Dietary management of hepatic encephalopathy in cirrhotic patients: survey of current practice in United Kingdom

Editorial by Seymour In the early 1950s it was shown that some patients with cirrhosis given “nitrogenous substances,” including excess dietary protein, developed hepatic “precoma.” 1 These largely uncontrolled observations...

Comment on Recent Symposium Overview: Does Excess Dietary Protein Adversely Affect Bone

Comment on Recent Symposium Overview: Does Excess Dietary Protein Adversely Affect Bone

Clinical nutrition of small psittacines and passerines

There is an increasing volume of work on the nutritional requirements of small psittacine and passerine species and this, together with the extensive nutritional studies of poultry, provides a basis for nutritional guidelines for pet birds. Most of the small psittacine and passerine species are granivorous, but not all the nutritional requirements can be met by an unsupplemented seed diet. Macronutrient and energy requirements can usually be met by a seed-based diet, but during reproduction and growth, the requirement for macronutrients, particularly protein, is considerably increased. Diets should be designed to provide a minimum of 10% to 14% of dietary protein for adult birds and 15% to 20% for growing birds. There is no advantage in providing excess dietary protein, and levels of 25% and greater have been shown to have detrimental effects in growing birds. With respect to micronutrients, imbalances in calcium, phosphorus, and vitamin D are some of the more commonly observed nutritional disorders, particularly in reproducing and growing birds. Seed-based diets tend to have a low calcium-phosphorus ratio, which should be adjusted to an optimal ratio of 2:1 through supplementation. Further mineral imbalances that have been documented in pet birds include iodine insufficiency, which causes goiter, and iron, which is more often associated with symptoms of toxicity. The other micronutrient imbalance that most commonly affects birds is vitamin A, and both insufficiency and toxicity are frequently observed. Seed-based diets do not contain enough s-carotene to prevent vitamin A deficiency, and oversupplementation with very rich sources, such as cod liver oil, can result in hypervitaminosis A. This article reviews the latest information on the specific macro- and micronutrient requirements of small psittacines and passerines. It provides guidelines on the minimum and maximum requirements for maintenance, growth, and reproduction and discusses the clinical conditions commonly associated with malnutrition in birds.

Excess Dietary Protein Can Adversely Affect Bone

The average American diet, which is high in protein and low in fruits and vegetables, generates a large amount of acid, mainly as sulfates and phosphates. The kidneys respond to this dietary acid challenge with net acid excretion, as well as ammonium and titratable acid excretion. Concurrently, the skeleton supplies buffer by active resorption of bone. Indeed, calciuria is directly related to net acid excretion. Different food proteins differ greatly in their potential acid load, and therefore in their acidogenic effect. A diet high in acid-ash proteins causes excessive calcium loss because of its acidogenic content. The addition of exogenous buffers, as chemical salts or as fruits and vegetables, to a high protein diet results in a less acid urine, a reduction in net acid excretion, reduced ammonium and titratable acid excretion, and decreased calciuria. Bone resorption may be halted, and bone accretion may actually occur. Alkali buffers, whether chemical salts or dietary fruits and vegetables high in potassium, reverse acid-induced obligatory urinary calcium loss. We conclude that excessive dietary protein from foods with high potential renal acid load adversely affects bone, unless buffered by the consumption of alkali-rich foods or supplements.

Excess Dietary Protein May Not Adversely Affect Bone

Too little protein is always harmful for the skeleton. Increasing dietary protein increases endogenous calcium excretion. The ability to adapt depends upon the adequacy of an individual’s calcium intake. At a population level, the effect of protein is often minimized because calcium intake rises with increasing protein intake. A dietary calcium-to-protein ratio ≥20:1 (mg:g) probably provides adequate protection for the skeleton. Excess protein will not harm the skeleton if the calcium intake is adequate.

Does Excess Dietary Protein Adversely Affect Bone? Symposium Overview

Does Excess Dietary Protein Adversely Affect Bone? Symposium Overview

Excessive dietary protein and suboptimal caloric intake have a negative effect on the growth of children with chronic renal disease before and during growth hormone therapy

Although diet and nutrition are an integral part of the management of individuals with chronic renal failure (CRF), little has been written on the effect of nutrition on the growth response to growth hormone (GH) in CRF. We studied the GH axis and nutritional status of 31 prepubertal children aged 8.7 ± 0.5 years with a height standard deviation score (SDS) of −3.2 ± 0.2 (mean ± SEM) with CRF. Sixteen CRF patients on hemodialysis and 15 on peritoneal dialysis were studied. Forty-four age-matched normal short children without GH deficiency served as controls. Spontaneous 12-hour GH and stimulated GH values were significantly higher and GH binding protein (GHBP) was significantly lower in the CRF patients than in the normal short children. Both before the initiation of GH therapy and after the first year of treatment, the growth velocity (SDS) was inversely correlated with dietary protein intake and positively correlated with caloric intake. GH was administered at a dosage of 28 and 21 IU/m 2/wk to the CRF group and the normal short children, respectively, divided into seven daily doses. The growth response of the normal short children was significantly greater than that of the CRF patients. GH therapy induced a smaller increment in GHBP and IGF-I in the CRF patients versus the normal short children (8.8 ± 2.2 and 10.2 ± 2.7 v 24.8 ± 1.3 and 27.6 ± 2.5 nmol/L, respectively, P < .01). The 1-year growth velocity of the CRF children was most closely correlated with dietary protein and caloric intake. The nutritional status of CRF patients is concluded to be a major factor in growth both before and during GH therapy.

Threonine Requirement and Threonine Imbalance in Broiler Chickens

Three experiments were conducted to determine the effect of excess dietary protein on threonine requirement of broiler chicks to 14 d of age (Experiments 1 and 2) and to determine the threonine requirement from 16 to 28 d of age (Experiment 3). Two dietary protein levels were used in Experiments 1 and 2:20% CP in a threonine-limiting basal diet containing wheat, peanut meal, and selected amino acids and 25% CP in the same basal diet supplemented with a mixture of amino acids lacking threonine. A threonine-limiting 25% CP diet based on corn, soybean meal, and amino acids was also included in Experiment 2. The threonine requirement of chicks from 16 to 28 d of age was determined using a single CP level (20%) in Experiment 3. Threonine requirements were estimated by broken line regression analysis of weight gain and feed efficiency. Threonine requirements based on weight gain were 7.7 and 6.7 g/k g of diet in Experiments 1 and 2, respectively, for chicks receiving the 20% CP diets. The requirements increased to 8.6 and 8.2 g/kg, respectively, for chicks fed the 25% CP diets based on wheat, peanut meal, and amino acids. The requirement for maximum weight gain of chicks fed 25% CP based on corn, soybean meal, and amino acids was 7.7 g/kg of diet. However, chicks ate more of this diet, and on an intake basis, the requirement of the chicks fed the 25% CP diets based on wheat and peanut meal or corn and soybean meal did not differ. Requirements based on feed efficiency were equal to, or less than, those based on weight gain in Experiments 1 and 2. Body moisture and fat contents were affected by dietary CP level (P < .01), ingredient composition (P < .01), and threonine content (P < .05). Estimates of threonine requirements based on regression analysis of plasma threonine concentrations were higher than those based on weight gain or feed efficiency. The threonine requirements of chicks fed a 20% CP diet from 16 to 28 d of age were 6.3 and 6.9 g/kg of diet based on weight gain and feed efficiency, respectively.