Soluble Milk Proteins Research Articles

Development of highly soluble and functional buffalo milk protein concentrate 60 by modifying ionic environment and characterisation thereof

The ionic and protein environment of buffalo skim milk was modified by instant pH drop and its restoration for the development of highly soluble milk protein concentrate‐60 (BuMRate–60@), which resulted in depletion of 88.64% calcium, 89.18% magnesium, 91.69% potassium and 93.96% phosphorous. BuMRate–60@ displayed excellent wetting, rehydration and solubility (97.76%). The Fourier transform infrared spectrometer spectra revealed significant stretching (C‐H and O‐H), N‐H bending and a large extent of H‐bonding. Scanning electron microscopy micrographs presented particles with porous nature and dimples, while transmission electron microscopy confirmed a greater release of minerals with altered casein micelles.

Digestibility of proteins in camel milk in comparison to bovine and human milk using an in vitro infant gastrointestinal digestion system

The absence of β-lactoglobulin, high β-/αs-casein ratio and protective proteins make camel milk a promising alternative protein base for making human infant formulae. In this study, protein digestibility of camel milk was compared with that of bovine and human milk using an in vitro infant gastrointestinal digestion system. A low degree of gastric proteolysis was observed in all three kinds of milk, and a single clot was formed in camel milk. The soluble milk proteins remaining in the gastric digesta were digested rapidly and extensively in the intestinal phase, while the proteins in the camel milk clot were hydrolysed gradually. Despite several similarities, bioactive peptides unique to individual milk were identified in the three intestinal milk digesta. The results suggest that camel milk proteins are equally digestible as bovine and human milk proteins under infant gastrointestinal digestion conditions, and it may be a prospective substitute for infant formula base.

Pea Proteins Have Anabolic Effects Comparable to Milk Proteins on Whole Body Protein Retention and Muscle Protein Metabolism in Old Rats.

Plant proteins are attracting rising interest due to their pro-health benefits and environmental sustainability. However, little is known about the nutritional value of pea proteins when consumed by older people. Herein, we evaluated the digestibility and nutritional efficiency of pea proteins compared to casein and whey proteins in old rats. Thirty 20-month-old male Wistar rats were assigned to an isoproteic and isocaloric diet containing either casein (CAS), soluble milk protein (WHEY) or Pisane™ pea protein isolate for 16 weeks. The three proteins had a similar effect on nitrogen balance, true digestibility and net protein utilization in old rats, which means that different protein sources did not alter body composition, tissue weight, skeletal muscle protein synthesis or degradation. Muscle mitochondrial activity, inflammation status and insulin resistance were similar between the three groups. In conclusion, old rats used pea protein with the same efficiency as casein or whey proteins, due to its high digestibility and amino acid composition. Using these plant-based proteins could help older people diversify their protein sources and more easily achieve nutritional intake recommendations.

АЛЛЕРГЕННАЯ АКТИВНОСТЬ И ОПАСНОСТЬ ПРОМЫШЛЕННОЙ ПЫЛИ СУХИХ ПРОДУКТОВ ПЕРЕРАБОТКИ КОРОВЬЕГО МОЛОКА

The purpose of the work was to establish in a model experiment the allergenic activity and danger of the extracts obtained from the dust of dry products of cow's milk processing (DPMP), containing complexes of soluble whey (WMP) or casein milk proteins (CMP), as a stage of hygienic regulation of the content of dust DPMP in the air of the working area. Experiments on albino guinea pigs sensitized by the intradermal injection of standard doses of WMP and СМР solutions into the ear revealed the development of severe allergic reactions in the animals of the experimental groups with the prevalence of mixed mechanisms of immediate anaphylactic and delayed cell-mediated types. According to the criteria for the classification of industrial allergens, the WMP and СМР complexes have a strong allergenic activity and are differentiated to the 1-st class of allergenic hazard, which determines the classification of the DPMP dust containing them as extremely dangerous industrial allergens. This is confirmed by the established high levels of indicators of allergic-diagnostic reactions in vivo and in vitro when testing sensitized WMP and СМР animals with a solution of skim milk powder dust, indicating the presence of antigenic determinants of whey and casein milk proteins in it and a real ability to form cross-allergic reactions in the body of workers to dust from all dry milk processing products containing these proteins.

Nutritional quality and use of whey in human food for its valorization

Whey is generated during cheese making and can be up to nine times the weight of cheese. The objective of this work is to highlight the nutritional quality and the importance of whey in order to explore other ways of valuing it in human food with a view to improving the nutritional quality of locally processed foods in Benin. To achieve this goal, a literature review was carried out between January and September 2020. The results revealed that whey contains more than 90% water. It also has a high content of lactose (75% of the dry matter), a low content of fat, soluble milk proteins (approximately 20% of total milk proteins) and various minerals. It also contains other components, such as citric acid and lactic acid, non-protein nitrogenous materials such as urea and uric acid and group B vitamins, mainly vitamin B1 (thiamine), vitamin B2 (riboflavin) and vitamin B6 (pyridoxine). Whey is exploited indirectly through its constituents in the food and pharmaceutical industry and also directly through the production of some variants of cheese.

Effect of protein aggregation in wheat-legume mixed pasta diets on their in vitro digestion kinetics in comparison to "rapid" and "slow" animal proteins.

The aim of this work was to evaluate the impact of incorporating different legume flours (faba bean, lentil or split pea flours) on the pasta protein network and its repercussion on in vitro protein digestibility, in comparison with reference dairy proteins. Kinetics and yields of protein hydrolysis in legume enriched pasta and, for the first time, the peptidomes generated by the pasta at the end of the in vitro gastric and intestinal phases of digestion are presented. Three isoproteic (21%) legume enriched pasta with balanced essential amino acids, were made from wheat semolina and 62% to 79% of legume flours (faba bean or F-pasta; lentil or L-pasta and split pea or P-pasta). Pasta were prepared following the conventional pastification steps (hydration, mixing, extrusion, drying, cooking). Amino acid composition and protein network structure of the pasta were determined along with their culinary and rheological properties and residual trypsin inhibitor activity (3–5% of the activity initially present in raw legume flour). F- and L-pasta had contrasted firmness and proportion of covalently linked proteins. F-pasta had a generally weaker protein network and matrix structure, however far from the weakly linked soluble milk proteins (SMP) and casein proteins, which in addition contained no antitrypsin inhibitors and more theoretical cleavage sites for digestive enzymes. The differences in protein network reticulation between the different pasta and between pasta and dairy proteins were in agreement in each kinetic phase with the yield of the in vitro protein hydrolysis, which reached 84% for SMP, and 66% for casein at the end of intestinal phase, versus 50% for L- and P-pasta and 58% for F-pasta. The peptidome of legume enriched pasta is described for the first time and compared with the peptidome of dairy proteins for each phase of digestion. The gastric and intestinal phases were important stages of peptide differentiation between legumes and wheat. However, peptidome analysis revealed no difference in wheat-derived peptides in the three pasta diets regardless of the digestion phase, indicating that there was a low covalent interaction between wheat gluten and legume proteins.

Fast digestive, leucine-rich, soluble milk proteins improve muscle protein anabolism, and mitochondrial function in undernourished old rats.

One strategy to manage malnutrition in older patients is to increase protein and energy intake. Here, we evaluate the influence of protein quality during refeeding on improvement in muscle protein and energy metabolism. Twenty-month-old male rats (n = 40) were fed 50% of their spontaneous intake for 12 weeks to induce malnutrition, then refed ad libitum with a standard diet enriched with casein or soluble milk proteins (22%) for 4weeks. A 13C-valine was infused to measure muscle protein synthesis and expression of MuRF1, and MAFbx was measured to evaluate muscle proteolysis. mTOR pathway activation and mitochondrial function were assessed in muscle. Malnutrition was associated with a decrease in body weight, fat mass, and lean mass, particularly muscle mass. Malnutrition decreased muscle mTOR pathway activation and protein FSR associated with increased MuRF1 mRNA levels, and decreased mitochondrial function. The refeeding period partially restored fat mass and lean mass. Unlike the casein diet, the soluble milk protein diet improved muscle protein metabolism and mitochondrial function in old malnourished rats. These results suggest that providing better-quality proteins during refeeding may improve efficacy of renutrition in malnourished older patients.

Effects of Postexercise Protein Intake on Muscle Mass and Strength During Resistance Training: Is There an Optimal Ratio Between Fast and Slow Proteins?

While effects of the two classes of proteins found in milk (i.e., soluble proteins, including whey, and casein) on muscle protein synthesis have been well investigated after a single bout of resistance exercise (RE), the combined effects of these two proteins on the muscle responses to resistance training (RT) have not yet been investigated. Therefore, the aim of this study was to examine the effects of protein supplementation varying by the ratio between milk soluble proteins (fast-digested protein) and casein (slow-digested protein) on the muscle to a 9-week RT program. In a double-blind protocol, 31 resistance-trained men, were assigned to 3 groups receiving a drink containing 20g of protein comprising either 100% of fast protein (FP(100), n = 10), 50% of fast and 50% of slow proteins (FP(50), n = 11) or 20% of fast protein and 80% of casein (FP(20), n = 10) at the end of training bouts. Body composition (DXA), and maximal strength in dynamic and isometric were analyzed before and after RT. Moreover, blood plasma aminoacidemia kinetic after RE was measured. The results showed a higher leucine bioavailability after ingestion of FP(100) and FP(50) drinks, when compared with FP(20) (p< .05). However, the RT-induced changes in lean body mass (p < .01), dynamic (p < .01), and isometric muscle strength (p < .05) increased similarly in all experimental groups. To conclude, compared with the FP(20) group, the higher rise in plasma amino acids following the ingestion of FP(100) and FP(50) did not lead to higher muscle long-term adaptations.

Relationship between infants cow′s milk protein allergy and gastroesophageal reflux disease

Objective To investigate the relationship between cow′s milk protein allergy (CMPA) and gastroesophageal reflux disease (GERD) and the prognosis of GERD combined with CMPA. Methods Fifty patients (24 boys and 26 girls) with GERD were enrolled in this study from January 2015 to June 2016 at Department of Pediatrics, Tangdu Hospital of the Fourth Military Medical University.All children were treated with serum milk protein soluble IgE(sIgE) and milk protein avoidance test, and those with positive results of children′s milk protein by provocation test and those with milk serum protein sIgE negative by milk protein provocation tests were diagnosed as CMPA children with GERD according to the CMPA diagnostic criteria and received diet therapy for 1 month and then their blood eosinophil ratio and 24-hour esophageal pH were monitored. Results Twenty-three cases (46%) of 50 children with GERD were diagnosed as CMPA.There was significant difference in clinical symptoms between GERD group and GERD combined with CMPA group (χ2=22.78, P 0.05). For children with GERD combined with CMPA, the patients received dietary treatment for 1 month.There was significant improvement in vomiting, runny nose/wheezing/cough and diarrhea (P 0.05). The proportions of blood eosinophils were decreased after treatment compared with those before treatment [(2.7±1.8)% vs.(8.2±2.7)%, t=10.006, P<0.01]. The results of 5 children′s 24-hour esophageal pH monitoring showed that the reflux index and the number of acid GERD episodes were lower than before, and the difference was all statistically significant before and after(all P<0.05). Conclusions The occurrence of GERD in infants is partly related to CMPA, and the treatment of CMPA can relieve the clinical symptoms of GERD. Key words: Cow′s milk protein allergy; Gastroesophageal reflux disease; Infant

Soluble Milk Protein Supplementation with Moderate Physical Activity Improves Locomotion Function in Aging Rats.

Aging is associated with a loss of muscle mass and functional capacity. Present study was designed to compare the impact of specific dairy proteins on muscular function with or without a low-intensity physical activity program on a treadmill in an aged rat model. We investigated the effects of nutritional supplementation, five days a week over a 2-month period with a slow digestible protein, casein or fast digestible proteins, whey or soluble milk protein, on strength and locomotor parameters in sedentary or active aged Wistar RjHan rats (17–19 months of age). An extensive gait analysis was performed before and after protein supplementation. After two months of protein administration and activity program, muscle force was evaluated using a grip test, spontaneous activity using an open-field and muscular mass by specific muscle sampling. When aged rats were supplemented with proteins without exercise, only minor effects of different diets on muscle mass and locomotion were observed: higher muscle mass in the casein group and improvement of stride frequencies with soluble milk protein. By contrast, supplementation with soluble milk protein just after physical activity was more effective at improving overall skeletal muscle function in old rats compared to casein. For active old rats supplemented with soluble milk protein, an increase in locomotor activity in the open field and an enhancement of static and dynamic gait parameters compared to active groups supplemented with casein or whey were observed without any differences in muscle mass and forelimb strength. These results suggest that consumption of soluble milk protein as a bolus immediately after a low intensity physical activity may be a suitable nutritional intervention to prevent decline in locomotion in aged rats and strengthen the interest to analyze the longitudinal aspect of locomotion in aged rodents.

Soluble Milk Proteins Improve Muscle Mass Recovery after Immobilization-Induced Muscle Atrophy in Old Rats but Do not Improve Muscle Functional Property Restoration.

Effect of 3 different dairy protein sources on the recovery of muscle function after limb immobilization in old rats. Longitudinal animal study. Institut National de la Recherche Agronomique (INRA). The study took part in a laboratory setting. Old rats were subjected to unilateral hindlimb immobilization for 8 days and then allowed to recover with 3 different dietary proteins: casein, soluble milk proteins or whey proteins for 49 days. Body weight, muscle mass, muscle fibre size, isometric, isokinetic torque, muscle fatigability and muscle oxidative status were measured before and at the end of the immobilization period and during the recovery period i.e 7, 21, 35 and 49 days post immobilization. In contrast to the casein diet, soluble milk proteins and whey proteins were efficient to favor muscle mass recovery after cast immobilization during aging. By contrast, none of the 3 diary proteins was able to improve muscle strength, power and fatigability showing a discrepancy between the recovery of muscle mass and function. However, the soluble milk proteins allowed a better oxidative capacity in skeletal muscle during the rehabilitation period. Whey proteins and soluble milk proteins improve muscle mass recovery after immobilization-induced muscle atrophy in old rats but do not allow muscle functional property restoration.

Effect of supplementing meals with soluble milk proteins on plasma leucine levels in healthy older people: A randomized pilot study

BACKGROUND: The muscle protein synthetic response to food intake is reduced in aging, contributing to a progressive muscle loss. This anabolic resistance results from a decreased sensitivity to anabolic signals, especially leucinemia, a potent activator of protein synthesis. Nutritional strategies are needed to reach the anabolic threshold of leucinemia and stimulate muscle anabolism. OBJECTIVES: This study sought to evaluate the effect of supplementing meals with soluble milk proteins (SMP) on postprandial leucinemia in elders. METHODS: During 3 successive experimental sessions, 6 healthy older men (66.7 ± 0.7y) consumed a standardized lunch (27 g of proteins; 2.2 g of leucine) supplemented with a beverage containing 0 g, 5 g or 8.2 g of SMP (0 g, 0.6 g and 1.1 g of leucine, respectively). RESULTS: The supplementation with 5 g or 8.2 g of SMP induced an increase of 1.9 × and 2.5 × in plasma leucine levels, compared to the control meal (without additional SMP). The leucine area under the curve over 3h20 had an increase of 2.1 × and 2.3 ×, respectively, as compared to the control meal. CONCLUSIONS: Ingesting SMP in addition to a meal strongly increased postprandial plasma leucine, and could be an effective strategy to reach anabolic thresholds and optimize the anabolic effect of each meal.

Milk-soluble formula increases food intake and reduces Il6 expression in elderly rat hypothalami.

Malnutrition in the elderly is accompanied by several metabolic dysfunctions, especially alterations in energy homeostasis regulation and a loss of insulin responsiveness. Nutritional recommendations aim to enrich food with high protein and energy supplements, and protein composition and lipid quality have been widely studied. Despite the numerous studies that have examined attempts to overcome malnutrition in the elderly through such nutritional supplementation, it is still necessary to study the effects of a combination of protein, lipids, and vitamin D (VitD). This can be done in animal models of elderly malnutrition. In the present study, we investigated the effects of several diet formulae on insulin responsiveness, inflammation, and the hypothalamic expression of key genes that are involved in energy homeostasis control. To mimic elderly malnutrition in humans, elderly Wistar rats were food restricted (R, -50%) for 12 weeks and then refed for 4 weeks with one of four different isocaloric diets: a control diet; a diet where milk soluble protein (MSP) replaced casein; a blend of milk fat, rapeseed, and DHA (MRD); or a full formula (FF) diet that combined MSP and a blend of MRD (FF). All of the refeeding diets contained VitD. We concluded that: (i) food restriction led to the upregulation of insulin receptor in liver and adipose tissue accompanied by increased Tnfα in the hypothalamus; (ii) in all of the refed groups, refeeding led to similar body weight gain during the refeeding period; and (iii) refeeding with MSP and MRD diets induced higher food intake on the fourth week of refeeding, and this increase was associated with reduced hypothalamic interleukin 6 expression.

Fast-digestive protein supplement for ten days overcomes muscle anabolic resistance in healthy elderly men

Adequate protein intake is crucial to maintain muscle protein content in elderly subjects, but quality of dietary proteins should be considered. The aim was to determine whether soluble milk protein offers an original strategy to increase muscle anabolism in elderly subjects via a synergistic effect of fast-digesting proteins together with a unique essential AA content. We investigated the effect of a 10-day adequate-protein (AP) or high-protein (HP) diet together with the protein source as caseins (CAS) or soluble milk proteins (PRO) on specific muscle protein fractional synthesis rates (FSRs) in healthy elderly men (71.8±2.4yr, n=31). The isotopic study consisted of two periods of 4h each: a post-absorptive and a postprandial period. The fed state was defined by consumption of either 15g or 30g of PRO or CAS, given fractionally every 20min for 4h. Soluble milk proteins are produced using a membrane process directly from pasteurized milk. Specific muscle protein FSRs were measured during both postabsorptive and postprandial period using a continuous infusion of l-[1-(13)C]leucine. FSR of sarcoplasmic muscle proteins and actin did not increase significantly in the postprandial state compared to postabsorptive state, whereas myosin FSR rate was increased by feeding whatever the protein source in HP groups (0.024±0.005 vs 0.053±0.011%h(-1), P<0.05 and 0.026±0.004 vs 0.050±0.005%h(-1), P<0.004 for PRO HP and CAS HP) but only with the PRO meal in the AP groups (0.031±0.003 vs 0.062±0.009%h(-1), P<0.03 for PRO AP). Mitochondrial muscle protein FSR was also increased by feeding, irrespective of the protein quantity, but only in PRO meal groups (P<0.02). Fast-digesting soluble milk proteins improved postprandial muscle protein synthesis, especially mitochondrial muscle proteins and myosin fractional synthesis rates, in elderly subjects.

Interlaboratory Study of ELISA Kits for the Detection of Egg and Milk Protein in Processed Foods.

The labeling of seven specific allergenic ingredients (egg, milk, wheat, buckwheat, peanut, shrimp, and crab) is mandatory in Japan. To ensure proper labeling, two kinds of ELISA kits using polyclonal antibodies have been developed. However, we developed two novel ELISA kits using monoclonal antibodies with improved specificity, the Allergeneye ELISA Egg (AE-Egg) and Allergeneye ELISA Milk (AE-Milk) Kits, to detect egg and milk proteins in processed foods, respectively. Five types of processed food containing 10 mg/kg of egg or milk soluble protein were prepared for an interlaboratory study of the performance of these kits. The kits showed a relatively high reproducibility level of interlaboratory precision (AE-Egg RSDR, 3.7-5.7%; AE-Milk RSDR, 6.8-10.5%) and satisfied the recovery rate stipulated by Japanese guidelines (AE-Egg, 61.6-89.3%; AE-Milk, 52.1-67%) for all processed foods. Our results suggest that the AE-Egg and AE-Milk Kits are precise and reliable tools for detecting egg or milk proteins in processed foods.

Four-Month Course of Soluble Milk Proteins Interacts With Exercise to Improve Muscle Strength and Delay Fatigue in Elderly Participants

BackgroundThe benefit of protein supplementation on the adaptive response of muscle to exercise training in older people is controversial. ObjectiveTo investigate the independent and combined effects of a multicomponent exercise program with and without a milk-based nutritional supplement on muscle strength and mass, lower-extremity fatigue, and metabolic markers. DesignA sample of 48 healthy sedentary men aged 60.8 ± 0.4 years were randomly assigned to a 16-week multicomponent exercise training program with a milk-based supplement containing, besides proteins [total milk proteins 4 or 10 g/day or soluble milk proteins rich in leucine (PRO) 10 g/day], carbohydrates and fat. Body composition, muscle mass and strength, and time to task failure, an index of muscle fatigue, were measured. Blood lipid, fibrinogen, creatine phosphokinase, glucose, insulin, C-reactive protein, interleukin-6, tumor necrosis factor-α soluble receptors, and endothelial markers were assessed. ResultsBody fat mass was reduced after the 4-month training program in groups receiving 10 g/day of protein supplementation (P < .01). The training program sustained with the daily 10 g/day PRO was associated with a significant increase in dominant fat free mass (+5.4%, P < .01) and in appendicular muscle mass (+4.5%, P < .01). Blood cholesterol was decreased in the trained group receiving 10 g/day PRO. The index of insulin resistance (homeostasis model assessment–insulin resistance) and blood creatine phosphokinase were reduced in the groups receiving 10 g/day PRO, irrespective of exercise. The inflammatory and endothelial markers were not different between the groups. Training caused a significant improvement (+10.6% to 19.4%, P < .01) in the maximal oxygen uptake. Increased maximum voluntary contraction force was seen in the trained groups receiving 10 g/day of proteins (about 3%, P < .05). Time to task failure was improved in the trained participants receiving a 10 g/day supplementation with PRO (P < .01). ConclusionsSoluble milk proteins rich in leucine improved time to muscle failure and increase in skeletal muscle mass and strength after prolonged multicomponent exercise training in healthy older men.

Effects of soluble milk protein or casein supplementation on muscle fatigue following resistance training program: a randomized, double-blind, and placebo-controlled study.

BackgroundThe effects of protein supplementation on muscle thickness, strength and fatigue seem largely dependent on its composition. The current study compared the effects of soluble milk protein, micellar casein, and a placebo on strength and fatigue during and after a resistance training program.MethodsSixty-eight physically active men participated in this randomized controlled trial and underwent 10 weeks of lower-body resistance training. Participants were randomly assigned to the Placebo (PLA), Soluble Milk Protein (SMP, with fast digestion rate) or Micellar Casein (MC, with slow digestion rate) group. During the 10-week training period, participants were instructed to take 30 g of the placebo or protein twice a day, or three times on training days. Tests were performed on quadriceps muscles at inclusion (PRE), after 4 weeks (MID) and after 10 weeks (POST) of training. They included muscle endurance (maximum number of repetitions during leg extensions using 70% of the individual maximal load), fatigue (decrease in muscle power after the endurance test), strength, power and muscle thickness.ResultsMuscle fatigue was significantly lower (P < 0.05) in the SMP group at MID and POST (-326.8 ± 114.1 W and -296.6 ± 130.1 W, respectively) as compared with PLA (-439.2 ± 153.9 W and -479.2 ± 138.1 W, respectively) and MC (-415.1 ± 165.1 W and -413.7 ± 139.4 W, respectively). Increases in maximal muscle power, strength, endurance and thickness were not statistically different between groups.ConclusionsThe present study demonstrated that protein composition has a large influence on muscular performance after prolonged resistance training. More specifically, as compared with placebo or micellar casein, soluble milk protein (fast digestible) appeared to significantly reduce muscle fatigue induced by intense resistance exercise.

“Fast proteins” with a unique essential amino acid content as an optimal nutrition in the elderly: Growing evidence

Adequate protein intake is crucial to maintain body protein content in elderly subjects, but quality of dietary proteins should be also considered since amino acid composition and rate of protein digestion modulate amino acid availability. This study investigates whether the efficacy of optimal protein intake levels for protein retention in the elderly is influenced by protein quality. We investigated the effect of a 10-day adequate-protein (AP) or high-protein (HP) diet together with the protein source as caseins (CAS) or soluble milk proteins (PRO) on whole-body (WB) protein synthesis (PS) and protein breakdown (PB) in 4 groups of healthy elderly men (mean ± SEM: 71.8 ± 24.4 yr). The study consisted of two periods of 4 h each: a post-absorptive period and a postprandial period. The fed state was defined by consumption every 20 min and for 4 h, of either 15 g or 30 g of PRO or CAS. Steady-state WB and splanchnic leucine kinetics were measured using a continuous infusion of L-[1-13C]leucine in the postabsorptive state and L-[1-13C]leucine infusion plus oral L-[5,5,5-2H3]leucine in the postprandial state. WB PS was stimulated by feeding only with HP diets, whereas WB PB corrected for splanchnic extraction showed a similar pattern of post-feeding decrease in all groups. Consequently, net leucine balance was greater in the postprandial state after HP meals than after AP meals, with PRO meals leading to a better postprandial leucine balance (3.63 ± 0.16 μmol kg FFM(-1) min(-1)vs. 2.77 ± 0.21 μmol kg FFM(-1) min(-1) for PRO HP and CAS HP, respectively; P = 0.005). Postprandial protein retention was better improved in elderly men by an increase in protein intake when the protein supplementation was provided as fast-digesting proteins that induce high leucine availability.

Protein feeding pattern, casein feeding, or milk-soluble protein feeding did not change the evolution of body composition during a short-term weight loss program

Studies have shown that timing of protein intake, leucine content, and speed of digestion significantly affect postprandial protein utilization. Our aim was to determine if one can spare lean body mass during energy restriction by varying the quality and the timing of protein intake. Obese volunteers followed a 6-wk restricted energy diet. Four groups were compared: casein pulse, casein spread, milk-soluble protein (MSP, = whey) pulse, and MSP spread (n = 10-11 per group). In casein groups, caseins were the only protein source; it was MSP in MSP groups. Proteins were distributed in four meals per day in the proportion 8:80:4:8% in the pulse groups; it was 25:25:25:25% in the spread groups. We measured weight, body composition, nitrogen balance, 3-methylhistidine excretion, perception of hunger, plasma parameters, adipose tissue metabolism, and whole body protein metabolism. Volunteers lost 7.5 ± 0.4 kg of weight, 5.1 ± 0.2 kg of fat, and 2.2 ± 0.2 kg of lean mass, with no difference between groups. In adipose tissue, cell size and mRNA expression of various genes were reduced with no difference between groups. Hunger perception was also never different between groups. In the last week, due to a higher inhibition of protein degradation and despite a lower stimulation of protein synthesis, postprandial balance between whole body protein synthesis and degradation was better with caseins than with MSP. It seems likely that the positive effect of caseins on protein balance occurred only at the end of the experiment.

Spreading intake of a leucine-rich fast protein in energy-restricted overweight rats does not improve protein mass

ObjectiveEnergy restriction decreases fat mass and fat-free mass. Our aim was to prevent the latter using type and timing of protein nutrition as tools. MethodsYoung male Wistar rats were given a high-energy diet for 5 wk and then energy restricted and fed a high-protein diet containing caseins, milk-soluble proteins (MSP), or a casein–MSP mixture (n = 9 per group) as the only source of protein for 3 wk. Food intake was spread over 12 h, whereas in a previous experiment rats consumed their daily ration within 2 to 3 h. Weight and food intake were recorded. The body composition was measured by dual-energy x-ray absorptiometry before and after energy restriction. After 3 wk, the hind-limb muscles, the kidney, intestine, liver, and spleen weights, metabolic plasma parameters, and the liver and extensor digitorum longus muscle protein synthesis rates were measured in the postprandial state. ResultsThe food intake was similar in all groups. Energy restriction induced a significant decrease in body weight and fat mass (P < 0.001) and stopped the slow growth of lean body mass, with no differences between groups. Among all tissues, a significant effect was detected only for the intestine (P = 0.0012), with a higher weight in the casein group. Postprandial liver and muscle protein synthesis rates were not different between groups. ConclusionWhen using a high-protein diet spread over 12 h, the nature of the protein intake has no influence on the sparing of lean body mass during energy restriction in young overweight rats.