Low protein

About: Low protein is a research topic. Over the lifetime, 8139 publications have been published within this topic receiving 213225 citations.

Brain proteolipids. Isolation, purification and effect on ionic permeability of membranes.

Abstract: Proteolipid apoproteins have been isolated from a whole bovine brain homogenate by chloroform/methanol extraction, and fractionated by chromatography on modified (lipophilic) Sephadex, followed by ion-exchange chromatography on CM-Trisacryl. The various final, highly hydrophobic, fractions are homogeneous (sodium dodecyl sulfate/polyacrylamide gel electrophoresis). Transmembrane ion transfers were studied by 22Na + flux and electrical conductance measurements. Single channel events were observed at low protein concentrations, in particular with one of the final homogeneous apoproteolipids of molecular mass 24 kDa.

Dietary protein and bone health.

Abstract: The effects of dietary protein on bone health are paradoxical and need to be considered in context of the age, health status and usual diet of the population. Over the last 80 years numerous studies have demonstrated that a high protein intake increases urinary Ca excretion and that on average 1 mg Ca is lost in urine for every 1 g rise in dietary protein. This relationship is primarily attributable to metabolism of S amino acids present in animal and some vegetable proteins, resulting in a greater acid load and buffering response by the skeleton. However, many of these early studies that demonstrated the calciuric effects of protein were limited by low subject numbers, methodological errors and the use of high doses of purified forms of protein. Furthermore, the cross-cultural and population studies that showed a positive association between animal-protein intake and hip fracture risk did not consider other lifestyle or dietary factors that may protect or increase the risk of fracture. The effects of protein on bone appear to be biphasic and may also depend on intake of Ca- and alkali-rich foods, such as fruit and vegetables. At low protein intakes insulin-like growth factor production is reduced, which in turn has a negative effect on Ca and phosphate metabolism, bone formation and muscle cell synthesis. Although growth and skeletal development is impaired at very low protein intakes, it is not known whether variations in protein quality affect the achievement of optimal peak bone mass in adolescents and young adults. Prospective studies in the elderly in the USA have shown that the greatest bone losses occur in elderly men and women with an average protein intake of 16-50 g/d. Although a low protein intake may be indicative of a generally poorer diet and state of health, there is a need to evaluate whether there is a lower threshold for protein intake in the elderly in Europe that may result in increased bone loss and risk of osteoporotic fracture.

Nutritional status and intake regulation in sheep. II. The influence of sustained duodenal infusions of casein or urea upon voluntary intake of low-protein roughages by sheep

Abstract: In each of two experiments, casein dissolved in 1% disodium hydrogen orthophosphate given daily to sheep per duodenum increased the intake of the roughages offered. Results in each experiment were compared with those of infusions of equivalent volumes of phosphate solution alone. In experiment 1, casein (4.5 g nitrogen/day) infused per duodenum resulted in a 42% increase in intake of a chaffed oaten hay (0.56% nitrogen) diet. Mean retention time of food in the alimentary tract was not altered, but the digestibility of the dry matter and the rate of cotton thread digestion in the rumen were depressed. Urea (4.5 g nitrogen/day) given per duodenum gave a 12% increase in intake, associated with a greater rate of cotton thread digestion in the rumen, and a consistently shorter mean retention time of residues in the alimentary tract. Evidence suggested a greater amount of dry matter in the gut when casein was given but not when urea was given. Nitrogen balance was improved from negative values to positive values by both casein and urea infusions. In experiment 2, a diet of wheaten straw supplemented with 3% urea was offered. Under these conditions, casein (6 g nitrogen/day) improved nitrogen balance and produced an average increase of 11% in daily dry matter intake. Rates of cotton thread digestion, digestibility of dry matter, mean retention time, and number of rumination chews were all unaltered by casein infusion. Results from both experiments are discussed in relation to current hypotheses of the mechanisms for regulating roughage intake in ruminants. A possible role of protein status of the animal in influencing the amount of dry matter which is held in the alimentary tract under ad libitum feeding conditions is suggested.