PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “DIETARY PROTEINS”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed2025

Large Quantities of Bacterial DNA and Protein in Common Dietary Protein Source Used in Microbiome Studies.

Diet has been shown to greatly impact the intestinal microbiota. To understand the role of individual dietary components, defined diets with purified components are frequently used in diet-microbiota studies. Defined diets frequently use purified casein as the protein source. Previous work indicated that casein contains microbial DNA potentially impacting results of microbiome studies. Other diet-based microbially derived molecules that may impact microbiome measurements, such as proteins detected by metaproteomics, have not been determined for casein. Additionally, other protein sources used in microbiome studies have not been characterized for their microbial content. We used metagenomics and metaproteomics to identify and quantify microbial DNA and protein in a casein-based defined diet to better understand potential impacts on metagenomic and metaproteomic microbiome studies. We further tested six additional defined diets with purified protein sources with an integrated metagenomic-metaproteomic approach and found that contaminating microbial protein is unique to casein within the tested set as microbial protein was not identified in diets with other protein sources. We also illustrate the contribution of diet-derived microbial protein in diet-microbiota studies by metaproteomic analysis of stool samples from germ-free mice (GF) and mice with a conventional microbiota (CV) following consumption of diets with casein and non-casein protein. This study highlights a potentially confounding factor in diet-microbiota studies that must be considered through evaluation of the diet itself within a given study.

Animals↗
PubMed1998

The timing of protein feeding and dietary protein levels affect taste preference, serum zinc concentration and glossal epithelial morphology in growing rats.

OBJECTIVE: The present study investigated the effect of timing of protein feeding on taste preference, serum zinc concentration and morphological changes of tongue epithelia. METHODS: Weanling rats were fed one of three diets: protein-free and 2.5 or 8% purified egg protein (PEP) diets for 14 days (first feeding period). Rats in each group were further subdivided into three dietary treatments, totaling nine groups and fed one of the same three diets for 14 days (second feeding period). Preference tests between 3 or 6 mmol/L NaCl vs. deionized water were conducted in both feeding periods. At the end of each period, blood and tongue were collected for the measurement of serum zinc concentrations and morphological observations. RESULTS: The rats fed the protein-free diet in the first feeding period did not discriminate 3 mmol/L NaCl from deionized water in both feeding periods, even though adequate protein was administered in the second feeding period. The rats fed the 2.5 or 8% PEP diet in the first feeding period discriminated 3 mmol/L NaCl from deionized water regardless of the protein levels in the diet during the second feeding period. Serum zinc concentration was proportionate to protein content in the diet at the end of each feeding period (p < 0.001), and low serum zinc concentration was restored by protein feeding. Abnormal changes of tongue epithelia were observed only in the rats fed the protein-free diet throughout the two feeding periods. CONCLUSIONS: The results suggest that protein nutrition immediately after weaning is important to maintain normal taste function.

Animals↗
PubMed1982

Potassium requirement of kittens as affected by dietary protein.

The dietary potassium requirements of weaning kittens given basal diets containing either a "normal" (33%) or "high" (68%) level of protein were determined. Potassium as KHCO3 was added to give concentrations of 0.1, 0.2, 0.3, and 0.4% for the 33% protein diet and 0.3, 0.4, 0.5, and 0.6% for the 68% protein diet. Excluding the highest concentrations of potassium used, body weight gains within diets were positively and linearly related to potassium concentration. Within both levels of dietary protein, concentration of potassium is plasma was linearly related to dietary potassium; however, for the same dietary potassium concentrations, kittens receiving the high protein diet had lower concentrations of potassium in plasma than kittens given he normal protein diet. Body weight gains were greater for kittens given the 68% protein diets than those receiving the 33% protein diet. The dietary potassium requirements of kittens were estimated as being in the range of 0.3% to 0.5% for 33% and 68% protein diets.

Animals↗
PubMed1987

Prior dietary protein intake and DNA-binding 7,12-dimethylbenz[a]anthracene metabolites formed by isolated rat hepatocytes.

Hepatocytes were isolated from noninbred Sprague-Dawley rats previously fed diets containing 7.5 or 15% protein. These hepatocytes were incubated in the presence of exogenous DNA for examination of their ability to metabolize 7,12-dimethylbenz[a]anthracene [(DMBA) CAS: 57-97-6] and release reactive DNA-binding metabolites to the medium. An increased formation of extracellular water-soluble metabolites of DMBA was observed in hepatocyte cultures from rats fed a 15% protein diet compared with that in cells from rats fed 7.5% protein. As dietary protein increased, there was a reduction in the release of DNA-binding metabolites by isolated hepatocytes. Bay-region dihydrodiol-epoxide adducts were formed with extracellular calf thymus DNA and hepatic DNA. However, most of the binding of DMBA with extracellular and intracellular DNA was due to unidentified DMBA-DNA adducts that eluted, upon reversed-phase chromatography, after the bay-region dihydrodiol-epoxide DMBA adducts were formed. The present studies show that feeding animals diets that are limiting in protein results in a decrease in DMBA detoxification and an increase in excretion of reactive DMBA metabolites from the liver. These results may explain the previously observed influence of dietary protein on the initiation of DMBA-induced mammary carcinogenesis in the rat.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Indications and implications for testing of milk urea in dairy cattle: a quantitative review. Part 2. Effect of dietary protein on reproductive performance.

DIETARY PROTEIN AND DAIRY COW FERTILITY: Feeding more dietary protein has been negatively associated with dairy cow fertility in some but not all studies. We used meta-analysis to examine the relationship between dietary crude protein and conception rate. While a higher intake of dietary crude protein significantly lowered conception rate, the potential for feeding less degradable dietary protein to modify this relationship was not demonstrated. MILK UREA CONCENTRATIONS AND DAIRY COW FERTILITY: The use of milk urea as an indicator of dietary energy and protein intake and as an indicator of reproductive performance has been questioned. We found that changes in urea concentration in body fluids explained only 25% (p = 0.08) of the variance in conception rate after conducting a meta-analysis of available studies. INTERPRETATION OF MILK UREA CONCENTRATIONS: High intakes of dietary protein may induce adaptations in urea metabolism, and the negative relationship identified between high intakes of dietary protein and fertility for Northern Hemisphere dairy herds may not necessarily apply in Australasian dairy herds. Because of the potential for cows to adapt to high protein diets, the use of a single milk urea determination on a herd will have limited value as an indicator of nutritional status and little value as a predictor of fertility.

Journal Article↗
PubMed2001

Is age-induced decline in immune response associated with hypothalamic glutamate receptor density and dietary protein?

Manipulation of dietary protein has been found to be the most useful dictator in the age-associated decline of neuroimmune activity in mammals. In the present study, we sought to clarify the effect of dietary protein on age-induced alterations of hypothalamic glutamatergic activity and immune response. The hypothalamic glutamatergic activity and immune response were found to increase and decrease, respectively, with the increase in age of rats from young (3 months) to old (18 months) maintained with normal (20%) protein diet. Intake of low (5%) protein diet (LPD) and high (40%) protein diet (HPD) under short-term period (7 days) failed to alter the age-associated loss of immune response and increase in hypothalamic glutamatergic activity. However, long-term (30 days) supplementation of LPD retarded the age-induced decline in immune response and increase in hypothalamic glutamatergic activity, whereas, HPD consumption under similar condition potentiated the age-related immunosuppression and increase in hypothalamic glutamatergic activity. These results suggest that (a) the age-associated immunosuppression may be inversely related to the hypothalamic glutamatergic activity and (b) consumption of diets having variable quantity of protein without variation of calorie content modulates immune response and hypothalamic glutamatergic activity depending upon age and duration of dietary supplementation.

Aging↗
PubMed2000

Cerebrospinal fluid concentrations of tryptophan and 5-hydroxyindoleacetic acid in Macaca mulatta: diurnal variations and response to chronic changes in dietary protein intake.

In rats, dietary protein is known to influence brain tryptophan (TRP) concentrations and serotonin (5HT) synthesis. However, few studies have examined this relationship in primates (including humans). We therefore studied the effect in monkeys of changes in chronic protein intake on plasma and cerebrospinal fluid (CSF) concentrations of TRP and 5-hydroxyindoleacetic acid (5HIAA), the principal 5HT metabolite. Juvenile male monkeys (Macacca mulatta) consumed for sequential 4-week periods diets differing in protein content (approximately 23%-->approximately 16%--> approximately 10%-->approximately 6% protein [%-energy/day]). Each day, food was presented as a morning meal of fruit, and an afternoon meal consisting of a pelleted, commercial diet and fruit. During week 4 on each diet, blood and CSF were sampled diurnally via indwelling catheters. Plasma and CSF TRP varied diurnally and with dietary protein content. On all diets, CSF TRP declined modestly in the morning, and increased in the afternoon; the magnitude of the increments varied directly with dietary protein content. Diurnal variations were absent for CSF 5HIAA; however, CSF 5HIAA varied directly with chronic dietary protein content. We conclude that dietary protein content can chronically influence CSF TRP concentrations in monkeys. The variation in CSF 5HIAA suggests chronic protein intake may influence serotonin synthesis and turnover, perhaps via changes in TRP concentrations.

Animals↗
PubMed1997

Urea and protein metabolism in burned children: effect of dietary protein intake.

The response of urea metabolic kinetics, the rate of whole-body protein breakdown, and muscle and skin protein synthesis rates to dietary protein intake (1.15 to 2.92 g/kg/d) was assessed in children with 20% to 40% total body surface area burn injury using a primed continuous infusion of 15N2-urea and L-13C6-phenylalanine. Plasma urea concentration, production, and excretion rates increased with dietary protein intake without evidence of approaching maximum plateau values. There was no consistent evidence of urea recycling in these subjects (urea production = excretion) at any level of protein intake. The rate of appearance (Ra) of phenylalanine (an index of whole-body protein breakdown) and rate of muscle protein synthesis were independent of dietary protein, whereas there was a significant increase in skin protein synthesis with higher protein intake. We conclude that there seems to be little benefit of high protein intake on whole-body protein breakdown and muscle protein synthesis rates in these burn patients, although high-protein diets may enhance wound healing.

Adolescent↗
PubMed1986

Further investigation of the dietary protein and monensin level interrelationship in broiler chicks: influence of Eimeria acervulina infection, increased dietary protein, and level of feed intake.

Three experiments were conducted to evaluate the influence of several dietary factors on the monensin response in commercial broiler chicks fed corn-soybean meal diets varying in crude protein (CP). All experiments were conducted between 8 and 22 days posthatching. Trial 1 had a 2 X 2 X 2 factorial design wherein diets containing 16 or 24% CP and 0 or 121 mg/kg monensin were fed in the presence and absence of Eimeria acervulina infection. The monensin-induced growth depression was greater at 16% CP than at 24% CP. Coccidial infection had no effect on the monensin X protein level interaction. Monensin supplementation markedly improved performance of chicks infected with E. acervulina. Trial 2 was conducted to determine if the monensin-induced depression in performance caused by feeding a high level of monensin (140 mg/kg) could be moderated by feeding a high protein diet. Monensin supplementation reduced growth rate 18 and 10% in chicks fed 20 and 24% CP, respectively. Increasing CP to 28% alleviated the adverse effects of monensin on weight gain. Pair-feeding was used in Trial 3 to determine the extent to which the monensin-induced growth depression observed in chicks fed low protein diets was due to reduced feed intake. As expected, reducing the dietary CP from 24 to 16% resulted in a marked increase in the growth depression caused by 121 mg/kg monensin. Pair-feeding indicated that most of monensin's adverse effects in low protein diets could be attributed to its anorexic properties.

Animals↗
PubMed1981

Factors determining the preservation of protein status during dietary protein deprivation.

Changes in protein content and function were investigated in man Sprague-Dawley Crl:Cd rats that were either fasted, consumed a diet containing 1.5 g fat/100 g initial body weight per day or received ad libitum an 85% carbohydrate, minimal nitrogen diet. Fasted rats became moribund after 9--10 days and were both hypoglycemic and hypoketonemic. In contrast, rats fed the fat-only and high carbohydrate, minimal nitrogen diets survived the 28-day study period. Although rats consuming the high carbohydrate, minimal nitrogen diet lost less body weight and nitrogen than either fasted animals or rats receiving the fat-only diet, they also had a loss of delayed hypersensitivity recall to tuberculin antigen and a 55% decrease in plasma essential amino acid concentrations. Rats fed the fat-only diet maintained delayed hypersensitivity recall and near normal concentrations of plasma essential amino acids despite a greater loss of body nitrogen than was observed in terminally fasted animals. Plasma albumin concentrations and total liver protein content showed comparable decreases in rats consuming the two incomplete diets. We concluded that nonprotein calories prolong survival in the rat and fat or predominantly glucose calories are sufficient at preventing mortality. However, the source or quantity of nonprotein calories consumed during periods of protein deprivation can markedly alter individual tissue protein status and function.

Amino Acids↗
PubMed1997

The effect of dietary protein on reproduction in the mare. I. The composition and evaluation of the digestibility of dietary protein from different sources.

Four rations that differed in their crude protein and essential amino-acid content were compiled. Digestibility of the crude protein and essential amino-acid contents were determined biologically in a feeding trial using 4 Anglo-Arab stallions. Their respective daily diets were: Diet 1:2 kg cubes, 5 kg tef hay (Eragrostis tef); Diet 2:2 kg cubes, 5 kg lucerne hay (Medicago sativa); Diet 3:2 kg cubes, 5 kg tef hay, 200 g fishmeal; Diet 4:2 kg cubes, 5 kg lucerne hay, 200 g fishmeal. The concentrations of the amino-acids threonine, iso-leucine, leucine and arginine were increased in the total ration when lucerne hay replaced the tef hay while fishmeal supplementation increased the methionine and lysine contents, which provided a wide-range of concentrations of digestible amino-acids in each of the 4 rations.

Animal Feed↗
PubMed1959

Plasma protein turnover and tissue exchange; influence of dietary protein and protein depletion.

The rate of plasma protein turnover is more rapid in dogs receiving adequate dietary protein than when a diet devoid of protein is fed. Both albumin and combined globulins are involved in this change. The difference in turnover is reflected in a total protein half-life of 4.8 days with protein feeding versus 7.8 days without protein in the diet and in the metabolism of 1.0 and 0.65 gm. per kilogram of body weight per day on the respective diets. Additions of dietary protein from 10 to 30 per cent caused no further increase in the rate of plasma protein turnover. With protein depletion due to plasmapheresis and a very low protein diet there is evidence of reduced protein metabolism as indicated by nitrogen retention as well as a reduction in total plasma protein breakdown and interchange of isotope between plasma and tissue proteins. Following introduction of labeled plasma protein into the circulation the net amount of isotope transferred to tissues has been computed from the difference between total plasma protein breakdown and combined C(14) excretion in urine and expired air. In animals receiving adequate dietary protein, tissue transfer amounts to 70 per cent of the total lost from the plasma proteins each day while the percentage rises to 85 in depleted dogs deprived of protein. In dogs with both plasma and tissue proteins labeled it can be estimated that, under conditions of protein feeding, an amount of C(14) approximately equal to that lost from the plasma must recycle to account for the observed decrease in Apparent plasma protein turnover rate, (t(1/2) of 15 versus 5 days). Without protein in the diet the isotope contribution of the tissues to the maintenance of plasma protein levels must be as great as or greater than that transferred in the opposite direction.

Animals↗
PubMed2005

A rapid self-administered food frequency questionnaire for the evaluation of dietary protein intake.

BACKGROUND: Dietary calcium and proteins are important determinants of bone health. Among the various methods to evaluate dietary intakes, food frequency questionnaires provide a self-administered, quick and simple estimation of dietary intakes. OBJECTIVES: To validate a simple, rapid, self-administered food frequency questionnaire for the estimation of dietary protein intake. DESIGN AND METHODS: A self-administrable food frequency questionnaire comprising 20 items was developed. The accuracy of dietary protein evaluation by this questionnaire was verified by comparing it to the results of a diary performed over a 4-day-period in 29 normal healthy subjects (mean age+/-SD, 40.1+/-12.3), and to the mean of three last 24-h recalls, administered at 6-week intervals in 43 healthy men (mean age+/-SD, 51.2+/-5.1). RESULTS: As compared with the values from both reference methods, the slope coefficient of linear regression analysis was statistically different from zero, but the percent of variance explained by the frequency questionnaire results amounted to 35% (diary) and 18% (24-h recall), respectively. Bland and Altman graphs as well as the Pitman's test did not show any difference in variability between the reference methods and the new food frequency questionnaire. This indicates a reliable estimate of group average dietary protein intakes. CONCLUSION: This rapid, self-administered food frequency questionnaire could be a useful tool for the evaluation of dietary protein intakes in groups of subjects.

Adult↗
PubMed1991

Interaction between dietary proteins and lipids in the regulation of serum and liver lipids in the rabbit. Effect of fish protein.

Purified diets varying in dietary protein, namely casein (CA), soy protein (SP), fish protein (FP), and lipid origin (corn oil (CN), coconut oil (CO)) were fed to rabbits to evaluate the effects of protein and fat source, as well as protein-lipid interactions, on serum total, lipoprotein and hepatic lipid levels. Dietary proteins and lipids exerted a separate effect on serum total cholesterol (C), very low-density lipoprotein cholesterol (VLDL-C), and low-density lipoprotein cholesterol to high density lipoprotein cholesterol (LDL-C/HDL-C) ratio. Hence, CA increased serum cholesterol compared to SP, while coconut oil enhanced serum and VLDL-C, and decreased LDL-C/HDL-C compared to corn oil. Dietary proteins interacted with dietary lipids to modulate HDL-C levels. Thus, FP maintained a high level of HDL-C regardless of lipid origin, compared to CA and SP whose HDL-C levels were decreased by corn oil, compared to coconut oil. A dietary protein-lipid interaction was also observed in the regulation of liver cholesterol levels. Coconut oil, compared to corn oil, decreased liver cholesterol in rabbits fed FP, whereas hepatic cholesterol concentration was unaltered by dietary lipid source in CA- and SP-fed rabbits. These results demonstrate that dietary proteins act synergistically with dietary lipids to regulate cholesterol metabolism in the rabbit.

Animals↗
PubMed1993

Effects of dietary protein on renal ischemia induced tubular necrosis.

Previously we have shown that the amount of protein in a dietary regimen prior to the induction of renal ischemia will significantly affect the degree of postischemic acute renal failure (Andrews PM, Bates SB: Kidney Int 30:299-303, 1986). The present investigation was undertaken to determine what effect dietary protein regimen has on the histopathology of renal ischemia. Rats were pair-fed for 2 weeks on either 0% or 5% (restricted), 20% (normal), or 60% (high) purified protein isocaloric diets. Ischemia was induced by 45 min of renal pedicle clamping. Light and electron microscopic evaluation of kidney morphology immediately following renal ischemia (prior to blood reflow) revealed that the extent of morphological damage to cells lining proximal convoluted tubules and the thick ascending segments of Henle's loop increased with increasing concentration of dietary protein. However, all dietary protein groups also exhibited heterogeneity in the extent of damage to different nephrons within the same kidney.

Animals↗