The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption

the progressive loss of muscle mass, commonly termed sarcopenia, accompanies the process of healthy aging ([27][1]). The underlying basis of this condition, in a very simplistic view, would be at a more advanced age skeletal muscle proteins are being lost because of an imbalance between muscle

The muscle protein synthetic response to food ingestion

The age-related loss of skeletal muscle mass and function is caused, at least in part, by a reduced muscle protein synthetic response to protein ingestion. The magnitude and duration of the postprandial muscle protein synthetic response to ingested protein is dependent on the quantity and quality of the protein consumed. This review characterises the anabolic properties of animal-derived and plant-based dietary protein sources in older adults. While approximately 60 % of dietary protein consumed worldwide is derived from plant sources, plant-based proteins generally exhibit lower digestibility, lower leucine content and deficiencies in certain essential amino acids such as lysine and methionine, which compromise the availability of a complete amino acid profile required for muscle protein synthesis. Based on currently available scientific evidence, animal-derived proteins may be considered more anabolic than plant-based protein sources. However, the production and consumption of animal-derived protein sources is associated with higher greenhouse gas emissions, while plant-based protein sources may be considered more environmentally sustainable. Theoretically, the lower anabolic capacity of plant-based proteins can be compensated for by ingesting a greater dose of protein or by combining various plant-based proteins to provide a more favourable amino acid profile. In addition, leucine co-ingestion can further augment the postprandial muscle protein synthetic response. Finally, prior exercise or n-3 fatty acid supplementation have been shown to sensitise skeletal muscle to the anabolic properties of dietary protein. Applying one or more of these strategies may support the maintenance of muscle mass with ageing when diets rich in plant-based protein are consumed.

The present study was conducted to evaluate and compare the effects of various animal and plant protein sources on piglet's performance, digestibility of amino acids and gut morphology in weaned pigs until 28 days after weaning. The plant protein sources used were soybean meal (SBM), fermented soy protein (FSP), rice protein concentrate (RPC); and animal protein sources tested were, whey protein concentrate (WPC) and fishmeal (FM). Iso-proteinous (21%) diets were formulated and lysine (1.55%) content was similar in all the diets. The level of each protein source added was 6% by replacing SBM to the same extent from the control diet containing 15% SBM. The ADG was higher (p<0.05) in the groups fed animal proteins as compared with plant proteins at all the levels of measurement, except during 15-28 days. The highest ADG was noted in WPC and FM fed diets and lowest in SBM fed diet. The feed intake was higher in animal protein fed groups than plant proteins at all phases, but the feed:gain ratio was not affected by protein sources except during overall (0 to 14 day) measurement which was improved (p<0.05) in animal protein fed diets compared to plant protein sources. The digestibilities of gross energy, dry matter and crude protein were higher in animal protein fed groups than for plant protein fed sources. The apparent ileal digestibilities of essential amino acids like Leu, Thr, and Met were significantly (p<0.05) higher in animal proteins fed animals as compared with plant protein fed animals. But the apparent fecal digestibilities of essential amino acids like Arg and Ile were significantly higher (p<0.05) in plant protein diets than animal protein sources. The villous structure studied by scanning electron microscope were prominent, straight finger-like, although shortened and densely located in FM fed group as compared with others. The lactic acid bacteria and C. perfringens counts were higher in caecal contents of pigs fed plant proteins than the animal proteins. Overall, it could be concluded that animal protein sources in the present study showed better effects on growth performance, nutrient digestibility and gut morphology than plant protein sources. (Asian-Aust. J. Anim. Sci. 2005. Vol 18, No. 9 : 1285-1293)

protein is the most important and vital part of the meal. Proteins are involved in stimulating the muscle protein synthesis. The quality of food also depends on the physical, chemical and behavioural characteristics of proteins during its processing. Long-term observational research found a link between high total and animal protein consumption and an elevated risk of cancer and diabetes. In line with the findings of observational research, plant protein is primarily liable for this positive impact. On one hand, animal proteins include all of the required amino acids found within the organic structure, making them extremely nutritious but found the culprit in imposing metabolic stress on the liver, bones, and kidney. Animal proteins have long been accused of contributing to an insufficient nutritional intake profile, which may explain the relationship with heart disease risk. It is also worth saying that because the vegan, vegetarian, and flexitarian communities have grown, plant proteins became more popular in cuisine. Due to increase in cardiovascular risk and other disease risk, many people are inclining towards the consumption of plant-based proteins. Plant proteins are employed in the manufacture of a large range of natural products. Soy protein isolates were first commercialized in 1959. People are also turning towards a plant protein diet considering the negatives of animal protein, but allergenicity is a back-pulling force. Plant proteins have lately received more attention as allergens, notably in Europe and therefore the US, furthermore as in relevancy innovative and transgenic foods. The oxidative alterations had a derogatory impact on the functioning of plant proteins eg. soy proteins in general. In both sexes, replacing 3% of energy from diverse protein sources from animal and with plant protein was related to a 10% decline in overall mortality. Plant-based protein consumption have relatively less mortality rate as compared to animal-based protein. Still, animal-based proteins are good source of essential amino acids than plant proteins. The link between protein consumption and mortality might also be explained by the consumption of other nutrients and physiologically active substances in protein-rich diets. Furthermore, a growing amount of clinical data, related to older persons, supports health benefits related to protein intakes that are at or above current dietary protein consumption guidelines but the source of proteins is still a point of debate and hence dilemma is constant of whether we are ready for revolution or not.

There is a global trend of an increased interest in plant-based diets. This includes an increase in the consumption of plant-based proteins at the expense of animal-based proteins. Plant-derived proteins are now also frequently applied in sports nutrition. So far, we have learned that the ingestion of plant-derived proteins, such as soy and wheat protein, result in lower post-prandial muscle protein synthesis responses when compared with the ingestion of an equivalent amount of animal-based protein. The lesser anabolic properties of plant-based versus animal-derived proteins may be attributed to differences in their protein digestion and amino acid absorption kinetics, as well as to differences in amino acid composition between these protein sources. Most plant-based proteins have a low essential amino acid content and are often deficient in one or more specific amino acids, such as lysine and methionine. However, there are large differences in amino acid composition between various plant-derived proteins or plant-based protein sources. So far, only a few studies have directly compared the muscle protein synthetic response following the ingestion of a plant-derived protein versus a high(er) quality animal-derived protein. The proposed lower anabolic properties of plant- versus animal-derived proteins may be compensated for by (i) consuming a greater amount of the plant-derived protein or plant-based protein source to compensate for the lesser quality; (ii) using specific blends of plant-based proteins to create a more balanced amino acid profile; (iii) fortifying the plant-based protein (source) with the specific free amino acid(s) that is (are) deficient. Clinical studies are warranted to assess the anabolic properties of the various plant-derived proteins and their protein sources in vivo in humans and to identify the factors that may or may not compromise the capacity to stimulate post-prandial muscle protein synthesis rates. Such work is needed to determine whether the transition towards a more plant-based diet is accompanied by a transition towards greater dietary protein intake requirements.

An impaired muscle protein synthetic response to feeding likely contributes to muscle loss with aging. There are few data available on the effect of the macronutrient composition of clinical supplements on the postprandial muscle protein synthetic response in older subjects. The objective of the study was to determine the impact of the macronutrient composition of a nutritional supplement on the postprandial muscle protein synthetic response in older men. A total of 45 nonsarcopenic older men (aged 69 ± 1 y; body mass index 25.7 ± 0.3 kg/m(2)) were randomly assigned to ingest 21 g of leucine-enriched whey protein with carbohydrate (9 g) and fat (3 g) (Pro-En), an isonitrogenous amount of 21 g of leucine-enriched whey protein without carbohydrate and fat (Pro), or an isocaloric mixture (628 kJ) containing carbohydrate and fat only (En). Stable isotope tracer methodology was applied to assess the basal as well as the postprandial muscle protein synthesis rates in the three groups. Ingestion of protein in the Pro-En and Pro groups significantly increased muscle protein synthesis rates when compared with the basal rates (from 0.032 ± 0.003%/h to 0.05%/h 3 ± 0.004%/h and 0.040%/h ± 0.003%/h to 0.049%/h ± 0.003%/h, respectively; P < .05), whereas ingestion of carbohydrate and fat did not increase muscle protein synthesis rates in the En group (from 0.039%/h ± 0.004%/h to 0.040%/h ± 0.003%/h; P = .60). Despite the greater postprandial rise in circulating insulin concentration in the Pro-En group, no significant differences were observed in postprandial muscle protein synthesis rates between the Pro-En and Pro groups (P = .32). Postprandial muscle protein synthesis rates were higher in the Pro-En vs En group (P = .01). The ingestion of a nutritional supplement containing 21 g of leucine-enriched whey protein significantly raises muscle protein synthesis rates in nonsarcopenic older men, but coingestion of carbohydrate and fat does not modulate the postprandial muscle protein synthetic response to protein ingestion in older men.

ABSTRACTBackgroundProtein ingestion increases muscle protein synthesis rates. The food matrix in which protein is provided can strongly modulate the postprandial muscle protein synthetic response. So far, the muscle protein synthetic response to the ingestion of whole foods remains largely unexplored.ObjectivesTo compare the impact of ingesting 30 g protein provided as milk protein or cheese on postprandial plasma amino acid concentrations and muscle protein synthesis rates at rest and during recovery from exercise in vivo in young males.MethodsIn this randomized, parallel-group intervention trial, 20 healthy males aged 18–35 y ingested 30 g protein provided as cheese or milk protein concentrate following a single-legged resistance-type exercise session consisting of 12 sets of leg press and leg extension exercises. Primed, continuous intravenous L-[ring-13C6]-phenylalanine infusions were combined with the collection of blood and muscle tissue samples to assess postabsorptive and 4-h postprandial muscle protein synthesis rates at rest and during recovery from exercise. Data were analyzed using repeated measures Time × Group (× Leg) ANOVA.ResultsPlasma total amino acid concentrations increased after protein ingestion (Time: P < 0.001), with 38% higher peak concentrations following milk protein than cheese ingestion (Time × Group: P < 0.001). Muscle protein synthesis rates increased following both cheese and milk protein ingestion from 0.037 ± 0.014 to 0.055 ± 0.018%·h–1 and 0.034 ± 0.008 to 0.056 ± 0.010%·h–1 at rest and even more following exercise from 0.031 ± 0.010 to 0.067 ± 0.013%·h–1 and 0.030 ± 0.008 to 0.063 ± 0.010%·h–1, respectively (Time: all P < 0.05; Time × Leg: P = 0.002), with no differences between cheese and milk protein ingestion (Time × Group: both P > 0.05).ConclusionCheese ingestion increases muscle protein synthesis rates both at rest and during recovery from exercise. The postprandial muscle protein synthetic response to the ingestion of cheese or milk protein does not differ when 30 g protein is ingested at rest or during recovery from exercise in healthy, young males.

BackgroundThe rate of protein digestion and amino acid absorption determines the postprandial rise in circulating amino acids and modulates postprandial muscle protein synthesis rates. ObjectiveWe sought to compare protein digestion, amino acid absorption kinetics, and the postprandial muscle protein synthetic response following ingestion of intact milk protein or an equivalent amount of free amino acids. MethodsTwenty-four healthy, young participants (mean ± SD age: 22 ± 3 y and BMI 23 ± 2 kg/m2; sex: 12 male and 12 female participants) received a primed continuous infusion of l-[ring-2H5]-phenylalanine and l-[ring-3,5–2H2]-tyrosine, after which they ingested either 30 g intrinsically l-[1–13C]-phenylalanine–labeled milk protein or an equivalent amount of free amino acids labeled with l-[1–13C]-phenylalanine. Blood samples and muscle biopsies were obtained to assess protein digestion and amino acid absorption kinetics (secondary outcome), whole-body protein net balance (secondary outcome), and mixed muscle protein synthesis rates (primary outcome) throughout the 6-h postprandial period. ResultsPostprandial plasma amino acid concentrations increased after ingestion of intact milk protein and free amino acids (both P < 0.001), with a greater increase following ingestion of the free amino acids than following ingestion of intact milk protein (P-time × treatment < 0.001). Exogenous phenylalanine release into plasma, assessed over the 6-h postprandial period, was greater with free amino acid ingestion (76 ± 9%) than with milk protein treatment (59 ± 10%; P < 0.001). Ingestion of free amino acids and intact milk protein increased mixed muscle protein synthesis rates (P-time < 0.001), with no differences between treatments (from 0.037 ± 0.015%/h to 0.053 ± 0.014%/h and 0.039 ± 0.016%/h to 0.051 ± 0.010%/h, respectively; P-time × treatment = 0.629). ConclusionsIngestion of a bolus of free amino acids leads to more rapid amino acid absorption and greater postprandial plasma amino acid availability than ingestion of an equivalent amount of intact milk protein. Ingestion of free amino acids may be preferred over ingestion of intact protein in conditions where protein digestion and amino acid absorption are compromised.

ObjectiveTo conduct a systematic review and meta‐analysis evaluating the effects of animal versus plant protein intake on bone mineral density (BMD), bone mineral content (BMC) and select bone biomarkers in healthy adults. [Registered on International Prospective Register of Systematic Reviews: PROSPERO CRD42015017751].MethodsThis study is a sub‐analysis of a larger systematic review following the methodologies in the Cochrane handbook. Searches across five databases were conducted through June 21, 2016 for randomized controlled trials (RCTs) in healthy adults that examined the effects of animal versus plant protein intake on 1) total body (TB), total hip (TH), lumbar spine (LS) or femoral neck (FN) BMD or TB BMC for at least one year, or 2) select bone formation and resorption biomarkers for at least six months. Random effect meta‐analyses were performed using Stata when data are sufficient.ResultsSeven RCTs were included in qualitative and quantitative synthesis. All included studies were parallel RCTs in healthy peri‐menopausal (n=1 study) and post‐menopausal (n=6) women. All plant protein sources were soy protein; animal protein sources were from milk (n=5), egg white (n=1) or not stated (n=1). Protein interventions ranged from 18–40g. There were no significant differences in BMD or BMC outcomes across studies between soy and animal protein groups, nor when examining collagen type‐1 cross‐linked N‐telopeptide (NTX, n=4)) or deoxypyridinoline (n=1). Though one study found soy protein significantly decreased collagen type‐1 cross‐linked C‐telopeptide (CTx) and bone‐specific alkaline phosphatase (BSAP) compared to milk protein, there were no further studies examining CTx, and BSAP did not significantly differ between groups in other studies (n=4).Meta‐analysis results showed on average, the difference between groups were close to zero and not significant for BMD outcomes (LS: n=4, WMD: 0.001 g/cm2, 95% CI: CI −0.006, 0.009, I2: 2.6%; TB: n=3, WMD: 0.001 g/cm2, 95% CI: −0.005, 0.007, I2: 0.0%; FN: n=3, WMD: −0.000 g/cm2, 95% CI: −0.006, 0.005, I2: 0.0%) and NTx (N=3, WMD: 0.644 nmol BCE, 95% CI −3.004, 4.293, I2: 0.0%;), and there was a nonsignificant, small effect size for BSAP (n=3, SMD: −0.06, 95% CI −0.29, 0.18, I2=0.0%). All outcomes had wide confidence intervals and no to low statistical heterogeneity. While overall risk of bias was low, half of the studies provided inadequate randomization information and had &lt;80% compliance.ConclusionsResults suggest there is no significant difference between plant and animal protein's effects on bone health outcomes in post‐menopausal women. However, studies were limited in number and findings among post‐menopausal women may not be generalizable to other populations. Future studies are needed examining the effects of different protein sources in different populations on BMD, BMC and biomarker outcomes.Support or Funding InformationFunding source: National Osteoporosis Foundation

The Muscle Protein Synthetic Response to the Ingestion of a Plant-Based Protein Blend Is Not Different From Milk Protein in Healthy, Young Males

BackgroundAnimals and plants are the main sources of dietary proteins, and there are important differences in the type of protein that they supply. The differences include molecular structure, amino acid profile, digestibility, and technical functionality in food, i.e. the ability to gel, emulsify, bind water etc. These inherent differences influence their bioavailability from a human nutrition perspective, as well as the sensory quality of foods containing animal or plant proteins. These fundamental differences mean that designing plant-based foods to mimic animal foods requires much more than simple substitution of one ingredient with another. Scope and approachWe survey some of the nutritional and technological functionality data for animal- and plant-derived food proteins and discuss the nature and implications of the differences between them. Key findings and conclusionsPlant-based foods typically provide less complete protein nutrition because of lower digestibility and source-specific deficiencies in essential amino acids, compared with animal proteins. Such differences may not be as essential for adults as they are for infants and young children, due to their developmental requirements. Plant proteins can be subjected to various processes to bring their functionality closer to that of animal proteins (e.g. hydrolysis to improve solubility), but some processes that improve functionality also diminish amino acid bioaccessibility or bioactivity, creating negative nutritional consequences. Much more research and innovation are required to enhance the potential of plant proteins. In the short to medium term, nutritional and functional synergies between plant and animal proteins may offer a path to creating nutritious and attractive foods.

Co-ingesting milk fat with micellar casein does not affect postprandial protein handling in healthy older men

The postprandial rise in essential amino acid (EAA) concentrations modulates the increase in muscle protein synthesis rates after protein ingestion. The EAA content and AA composition of the dietary protein source contribute to the differential muscle protein synthetic response to the ingestion of different proteins. Lower EAA contents and specific lack of sufficient leucine, lysine, and/or methionine may be responsible for the lower anabolic capacity of plant-based compared with animal-based proteins. We compared EAA contents and AA composition of a large selection of plant-based protein sources with animal-based proteins and human skeletal muscle protein. AA composition of oat, lupin, wheat, hemp, microalgae, soy, brown rice, pea, corn, potato, milk, whey, caseinate, casein, egg, and human skeletal muscle protein were assessed using UPLC–MS/MS. EAA contents of plant-based protein isolates such as oat (21%), lupin (21%), and wheat (22%) were lower than animal-based proteins (whey 43%, milk 39%, casein 34%, and egg 32%) and muscle protein (38%). AA profiles largely differed among plant-based proteins with leucine contents ranging from 5.1% for hemp to 13.5% for corn protein, compared to 9.0% for milk, 7.0% for egg, and 7.6% for muscle protein. Methionine and lysine were typically lower in plant-based proteins (1.0 ± 0.3 and 3.6 ± 0.6%) compared with animal-based proteins (2.5 ± 0.1 and 7.0 ± 0.6%) and muscle protein (2.0 and 7.8%, respectively). In conclusion, there are large differences in EAA contents and AA composition between various plant-based protein isolates. Combinations of various plant-based protein isolates or blends of animal and plant-based proteins can provide protein characteristics that closely reflect the typical characteristics of animal-based proteins.

Previous studies have shown the health benefits of daily total protein intake(1), yet temporal protein patterns in the population have rarely been investigated. The currently available studies have examined the associations between total protein intake at eating occasions (EOs) with cardiometabolic(2) and muscular health(3) but have not accounted for different protein sources. This study aimed to describe temporal patterns of total, plant, and animal protein intake at EOs in Australian adults, and to examine these patterns according to their sociodemographic and eating pattern characteristics (e.g., meal and snack frequencies, amount of protein intake). Using the 2011–12 Australian National Nutrition and Physical Activity Survey data, this study included adults aged ≥ 19 years who completed one 24-hour dietary recall (n = 6741). Total, animal and plant protein intake at self-reported EOs was estimated using the AUSNUT 2011–13 nutrient database and Australian Dietary Guidelines (ADG) food classification system(4). Plant protein included grains, nuts, and other plant-based, protein-containing foods, while animal protein consisted of meats, dairy, and other animal-source foods. Separate latent variable mixture models were used to identify temporal patterns of total, animal, and plant protein based on hourly intakes of total, animal, and plant protein, respectively. Pearson’s Chi-square test (for categorical variables) and one-way analysis of variance (for continuous variables) were used to examine the differences in participant characteristics between latent classes of temporal protein patterns. Three latent classes for men’s and women’s intake of total, animal, and plant proteins were identified. Class 1 was characterised by high probabilities of consuming protein at the usual Australian mealtime (e.g., dinner at 18:00–19:00h), and participants in this class were significantly older than the other two classes (all, p &lt; 0.001). Class 2 had a high probability of eating protein an hour later than the mealtime of Class 1 and the highest protein intake from meals (all, p &lt; 0.001), except for men’s total protein and women’s plant protein. Participants in Class 2 of total (all, p &lt; 0.001), animal (all, p &lt; 0.001), and plant protein (women only, p = 0.02) were characterised by high income and employment status. Participants in Class 3 had the lowest meal frequency (all, p &lt; 0.001) and the lowest total, animal, and plant protein intakes from meals (all, p &lt; 0.001), but the highest intakes from snacks (p &lt; 0.001), except for women’s animal protein intake. Most adults in Class 3 of total (men only, p &lt; 0.001) and animal protein (all, p &lt; 0.001) also had high education level, lived in urban areas, and were not married. Three temporal protein patterns with distinct characteristics were identified in this study. Future studies need to investigate whether these temporal protein intake patterns are associated with health outcomes.