Important determinants to take into account to optimize protein nutrition in the elderly: solutions to a complex equation

Improving sarcopenia in older adults: a systematic review and meta-analysis of randomized controlled trials of whey protein supplementation with or without resistance training

OBJECTIVES

The aim of the study was to comprehensively analyze the effects of whey protein (WP)-enriched supplement intake with or without resistance training (RT) in older patients, either from the community or hospital, who were diagnosed with sarcopenia according to the EWGSOP or AWGS criteria.

METHODS

This meta-analysis study was registered in PROSPERO (CRD42023407885). We searched the PubMed, Embase, Web of Science, and Cochrane Library databases for RCTs up to June 1, 2023. Standardized mean differences (SMD) with 95% confidence intervals (CI) were used to estimate the pooled results.

RESULTS

Ten RCT studies, including 1154 participants, were included and analyzed. The primary outcomes were the changes in muscle mass, strength, and physical performance. In WP group versus (vs.) Isocaloric placebo (PLA)/Routine consultation (RC) group, WP significantly increased the appendicular skeletal muscle mass index (SMD: 0.47, 95%CI: 0.23, 0.71), appendicular skeletal muscle mass (SMD: 0.28, 95%CI: 0.11, 0.45) and gait speed (SMD: 1.13, 95%CI: 0.82, 1.44) in older patients with sarcopenia. In WP with RT group vs. PLA/ RC group, there was significant increase in handgrip strength (SMD: 0.67, 95%CI: 0.29, 1.04). In addition, in the secondary outcomes, WP significantly reduced interleukin-6, significantly increased insulin-like growth factor-1 and albumin, promoted participants' intake of total energy and protein, enhanced activities of daily living scores in patients, and had no significant effect on BMI, weight, or fat mass.

CONCLUSION

This review confirms that WP can improve various aspects of older adult with sarcopenia, thereby enhancing their overall physical condition. More studies should be conducted to validate this result and further explore the effects of WP and RT in patients with sarcopenia.

Utilizing the influence of protein enrichment of meal components as a strategy to possibly prevent undernutrition in the elderly: an in vitro approach

Nutritional strategies are required to limit the prevalence of denutrition in the elderly. With this in mind, fortified meals can provide more protein, but their digestibility must be ensured. Using a dynamic in vitro digester, DIDGI®, programmed with the digestion conditions of the elderly, we evaluated the supplementation of each component of a meal and assessed protein digestibility, amino acid profile, micro-nutrients and vitamins bioaccessibility for a full course meal. Higher protein digestibility was evidenced for the fortified meal, with higher release of essential amino acids. Moreover the large increase of leucine released was comparable to the range advocated for the elderly to favour protein anabolism. This in vitro study underlines the interest of using dish formulations to meet the nutritional needs of seniors, which is why this work will be completed by a clinical study in nursing home.

Animal and vegetable protein intake and malnutrition in older adults: a multicohort study

OBJECTIVES

Malnutrition is a global concern in older adults, as it negatively affects morbidity and mortality. While higher animal protein intake may help prevent and treat malnutrition, it might also increase the risk of chronic diseases and death. Conversely, vegetable protein intake might have a lower anabolic effect and not be as effective to improve nutritional status. We studied whether animal and vegetable protein intake are associated with changes in nutritional status in older adults.

DESIGN

We used pooled data from two Spanish cohorts: the Seniors-ENRICA 1 and Seniors-ENRICA 2.

SETTINGS AND PARTICIPANTS

2,965 community-dwelling adults aged 62-92 years.

MEASUREMENTS

Protein intake was estimated at baseline via an electronic, validated diet history. Nutritional status was assessed at baseline and after 2.6 years with the GLIM (Global Leadership Initiative on Malnutrition) phenotypic criteria: weight loss, low body mass index, and reduced muscle mass. The odds of improvements in nutritional status were assessed with logistic regression models, extensively adjusted for potential confounders.

RESULTS

Higher animal and vegetable protein intake were associated with improvements in nutritional status [odds ratios (95% confidence intervals) per 0.25 g/kg/day were 1.15 (1.00, 1.32) and 1.77 (1.35, 2.32), respectively]. Cereal protein intake drove most of the latter association [2.07 (1.44, 2.98)]. Replacing 0.25 g/kg/day of total animal protein, meat, or fish protein (but not dairy or egg protein) with vegetable protein was associated with improvements in nutritional status [1.54 (1.13, 2.09), 1.70 (1.20, 2.41), and 1.77 (1.18, 2.64), respectively].

CONCLUSIONS

Higher animal and, especially, vegetable protein intake were associated with improvements in nutritional status in older adults. Replacing total animal protein, meat, or fish protein with vegetable protein may help improve malnutrition.

Protein digestion and absorption: the influence of food processing

The rates of dietary protein digestion and absorption can be significantly increased or decreased by food processing treatments such as heating, gelling and enzymatic hydrolysis, with subsequent metabolic impacts, e.g. on muscle synthesis and glucose homeostasis.This review examines in vivo evidence that industrial and domestic food processing modify the kinetics of amino acid release and absorption following a protein-rich meal. It focuses on studies that used compositionally-matched test meals processed in different ways.Food processing at extremely high temperature at alkaline pH and/or in the presence of reducing sugars can modify amino acid sidechains, leading to loss of bioavailability. Some protein-rich food ingredients are deliberately aggregated, gelled or hydrolysed during manufacture. Hydrolysis accelerates protein digestion/absorption and increases splanchnic utilisation. Aggregation and gelation may slow or accelerate proteolysis in the gut, depending on the aggregate/gel microstructure.Milk, beef and eggs are heat processed prior to consumption to eliminate pathogens and improve palatability. The temperature and time of heating affect protein digestion and absorption rates, and effects are sometimes non-linear. In light of a dietary transition away from animal proteins, more research is needed on how food processing affects digestion and absorption of non-animal proteins.Food processing modifies the microstructure of protein-rich foods, and thereby alters protein digestion and absorption kinetics in the stomach and small intestine. Exploiting this principle to optimise metabolic outcomes requires more human clinical trials in which amino acid absorption rates are measured and food microstructure is explicitly considered, measured and manipulated.

Nutritional Value of Yogurt as a Protein Source: Digestibility/Absorbability and Effects on Skeletal Muscle

Yogurt is a traditional fermented food that is accepted worldwide for its high palatability and various health values. The milk protein contained in yogurt exhibits different physical and biological properties from those of non-fermented milk protein due to the fermentation and manufacturing processes. These differences are suggested to affect the time it takes to digest and absorb milk protein, which in turn will influence the blood levels of amino acids and/or hormones, such as insulin, and thereby, the rate of skeletal muscle protein synthesis via the activation of intracellular signaling, such as the mTORC1 pathway. In addition, based on the relationship between gut microbiota and skeletal muscle conditions, yogurt, including lactic acid bacteria and its metabolites, has been evaluated for its role as a protein source. However, the substantial value of yogurt as a protein source and the additional health benefits on skeletal muscle are not fully understood. The purpose of this review is to summarize the research to date on the digestion and absorption characteristics of yogurt protein, its effect on skeletal muscle, and the contribution of lactic acid bacterial fermentation to these effects.

Contribution of Proteins to the Latin American Diet: Results of the ELANS Study

Dietary protein intake is vital to life. Here we sought to characterize dietary sources of protein in eight Latin American countries. Survey data were collected for Estudio Latinoamericano de Nutrición y Salud (ELANS); participants were from Argentina, Brazil, Chile, Colombia, Costa Rica, Ecuador, Peru, and Venezuela (n = 9218, 15-65 years old). The primary aim of this analysis was to quantify per-person daily protein consumption by country and sociodemographic factors. Secondary aims: to quantify proportional intake of proteins by source, amount and processing, and to determine the adequacy of protein/essential amino acid intake. Younger groups (adolescents 15-19 years, adults 20-33 years) had the highest intake of proteins; middle-aged adults (34-49 years) had a lower intake, and older adults (50-65 years) had a strikingly lower intake. Protein consumption was higher in men than women. Animal proteins comprised nearly 70% of total daily protein intake in Argentina and Venezuela, contrasting with <60% in Peru, Chile, and Costa Rica. Brazil and Venezuela showed the highest protein intake within the highest education level. The higher the socioeconomic level, the higher the protein intake, except for Argentina, Chile, and Peru. Proportional intake of animal- and plant-based protein generally reflected the food availability by country. This study presents a pre-pandemic regional baseline and offers a perspective for future studies of changes related to government policies, climate, and dietary practices.

The value of dietary plant protein in older people

PURPOSE OF REVIEW

The current review provides an update on recent research regarding plant-based protein and their nutritional quality for older people.

RECENT FINDINGS

There is growing evidence that plant-based proteins may be a valuable strategy for older people to prevent the health risks associated with consuming animal products and to promote better protein intake, as plant-based protein sources are rich in fibres and micronutrients. Although plant-based proteins are less anabolic than animal-derived proteins due to lower digestibility and deficiencies in some essential amino acids, several innovations in food processing and nutritional strategies have been developed to improve the quality of plant-based proteins. For example, the use of protein blends or green-processes as fermentation or germination could improve the nutritional qualities of plant-based foods that could be beneficial for older people, especially to prevent sarcopenia or metabolic disorders such as diabetes, obesity and cardiovascular diseases.

SUMMARY

The use of plant-based protein sources could help older people diversify their protein sources and more easily meet recommended nutritional intake. Recent literature highlights several health benefits associated with increased consumption of vegetable foods. However, their efficiency on postprandial muscle protein synthesis remains to be evaluated and long-term studies are needed.

Peripheral Amino Acid Appearance Is Lower Following Plant Protein Fibre Products, Compared to Whey Protein and Fibre Ingestion, in Healthy Older Adults despite Optimised Amino Acid Profile

Plant-based proteins are generally characterised by lower Indispensable Amino Acid (IAA) content, digestibility, and anabolic properties, compared to animal-based proteins. However, they are environmentally friendlier, and wider consumption is advocated. Older adults have higher dietary protein needs to prevent sarcopenia, a disease marked by an accelerated loss of muscle mass and function. Given the lower environmental footprint of plant-based proteins and the importance of optimising dietary protein quality among older adults, this paper aims to assess the net peripheral Amino Acid (AA) appearance after ingestion of three different plant protein and fibre (PPF) products, compared to whey protein with added fibre (WPF), in healthy older adults. In a randomised, single-blind, crossover design, nine healthy men and women aged ≥65 years consumed four test meals balanced in AA according to the FAO reference protein for humans, matched for leucine, to optimally stimulate muscle protein synthesis in older adults. A fasted blood sample was drawn at each visit before consuming the test meal, followed by postprandial arterialise blood sampling every 30 min for 3 h. The test meal was composed of a soup containing either WPF or PPF 1-3. The PPF blends comprised pea proteins with varying additional rice, pumpkin, soy, oat, and/or almond protein. PPF product ingestion resulted in a lower maximal increase of postprandial leucine concentration and the sum of branched-chain AA (BCAA) and IAA concentrations, compared to WPF, with no effect on their incremental area under the curve. Plasma methionine and cysteine, and to a lesser extent threonine, appearance were limited after consuming the PPF products, but not WPF. Despite equal leucine doses, the WPF induced greater postprandial insulin concentrations than the PPF products. In conclusion, the postprandial appearance of AA is highly dependent on the protein source in older adults, despite providing equivalent IAA levels and dietary fibre. Coupled with lower insulin concentrations, this could imply less anabolic potential. Further investigation is required to understand the applicability of plant-based proteins in healthy older adults.

Anti-inflammatory Streptococcus thermophilus CNRZ160 limits sarcopenia induced by low-grade inflammation in older adult rats

Background and aims

Aging is characterized, at the systemic level, by the development of low-grade inflammation, which has been identified as determining sarcopenia by blunting postprandial muscle anabolism. The causes of this “inflammageing” is still not clearly defined. An increased intestinal permeability, a microbiota dysbiosis and subsequent generation of intestinal then generalized inflammation have been hypothesized. The objective of this study was to test in vivo during aging if (1) a chronic low-grade intestinal inflammation can lead to anabolic resistance and muscle loss and (2) if a bacterial strain presenting anti-inflammatory properties could prevent these adverse effects.

Methods

Young adult (6 m) and elderly rats (18 m) received Dextran Sodium Sulfate (DSS) for 28 days to generate low-grade intestinal inflammation, and received (PB1 or PB2 groups) or not (DSS group) one of the two S. Thermophilus strains (5 × 109 CFU/day) previously shown to present an anti-inflammatory potential in vitro. They were compared to pair fed control (PF). Muscle and colon weights and protein synthesis (using 13C Valine) were measured at slaughter. Muscle proteolysis, gut permeability and inflammatory markers were assessed only in old animals by RT-PCR or proteins quantifications (ELISA).

Results

In both adult and old rats, DSS reduced absolute protein synthesis (ASR) in gastrocnemius muscle [−12.4% (PB1) and −9.5% (PB2) vs. PF, P &lt; 0.05] and increased ASR in colon (+86% and +30.5%, respectively vs. PF, P &lt; 0.05). PB1 (CNRZ160 strain) but not PB2 resulted in a higher muscle ASR as compared to DSS in adults (+18%, P &lt; 0.05), a trend also observed for PB1 in old animals (+12%, P = 0.10). This was associated with a blunted increase in colon ASR. In old rats, PB1 also significantly decreased expression of markers of autophagy and ubiquitin-proteasome pathways vs. DSS groups and improved gut permeability (assessed by Occludin, Zonula Occludens 1 and Claudin 1 expression, P &lt; 0.05) and alleviated systemic inflammation (A2M: −48% vs. DSS, P &lt; 0.05).

Conclusion

The loss of muscle anabolism associated with low-grade intestinal inflammation can be prevented by supplementation with anti-inflammatory CNRZ160 strain. We propose that the moderated gut inflammation by CNRZ160 may result in curtailed amino acids (AA) utilization by the gut, and subsequent restored AA systemic availability to support muscle protein accretion. Therefore, CNRZ160 could be considered as an efficient probiotic to modulate muscle mass loss and limit sarcopenia during aging.

The Effect of Metabolites on Mitochondrial Functions in the Pathogenesis of Skeletal Muscle Aging

Sarcopenia is an age-related systemic disease characterized by skeletal muscle aging that generally severely affects the quality of life of elderly patients. Metabolomics analysis is a powerful tool for qualitatively and quantitatively characterizing the small molecule metabolomics of various biological matrices in order to clarify all key scientific problems concerning cell metabolism. The discovery of optimal therapy requires a thorough understanding of the cellular metabolic mechanism of skeletal muscle aging. In this review, the relationship between skeletal muscle mitochondria, amino acid, vitamin, lipid, adipokines, intestinal microbiota and vascular microenvironment has been separately reviewed from the perspective of metabolomics, and a new therapeutic direction has been suggested.

Lacticaseibacillus casei CNCM I-5663 supplementation maintained muscle mass in a model of frail rodents

The aim of this study was to identify a probiotic-based strategy for maintaining muscle anabolism in the elderly. In previous research, we found that individuals experiencing short bowel syndrome (SBS) after an intestinal resection displayed beneficial metabolic adjustments that were mediated by their gut microbes. Thus, these bacteria could potentially be used to elicit similar positive effects in elderly people, who often have low food intake and thus develop sarcopenia. Gut bacterial strains from an SBS patient were evaluated for their ability to (1) maintain Caenorhabditis elegans survival and muscle structure and (2) promote protein anabolism in a model of frail rodents (18-month-old rats on a food-restricted diet: 75% of ad libitum consumption). We screened a first set of bacteria in C. elegans and selected two Lacticaseibacillus casei strains (62 and 63) for further testing in the rat model. We had four experimental groups: control rats on an ad libitum diet (AL); non-supplemented rats on the food-restricted diet (R); and two sets of food-restricted rats that received a daily supplement of one of the strains (∼10⁹ CFU; R+62 and R+63). We measured lean mass, protein metabolism, insulin resistance, cecal short-chain fatty acids (SCFAs), and SCFA receptor expression in the gut. Food restriction led to decreased muscle mass [-10% vs. AL (p < 0.05)]. Supplementation with strain 63 tempered this effect [-2% vs. AL (p > 0.1)]. The mechanism appeared to be the stimulation of the insulin-sensitive p-S6/S6 and p-eIF2α/eIF2α ratios, which were similar in the R+63 and AL groups (p > 0.1) but lower in the R group (p < 0.05). We hypothesize that greater SCFA receptor sensitivity in the R+63 group promoted gut-muscle cross talk [GPR41: +40% and GPR43: +47% vs. R (p < 0.05)]. Hence, strain 63 could be used in association with other nutritional strategies and exercise regimes to limit sarcopenia in frail elderly people.

Targeting the gut to prevent and counteract metabolic disorders and pathologies during aging

Impairment of gut function is one of the explanatory mechanisms of health status decline in elderly population. These impairments involve a decline in gut digestive physiology, metabolism and immune status, and associated to that, changes in composition and function of the microbiota it harbors. Continuous deteriorations are generally associated with the development of systemic dysregulations and ultimately pathologies that can worsen the initial health status of individuals. All these alterations observed at the gut level can then constitute a wide range of potential targets for development of nutritional strategies that can impact gut tissue or associated microbiota pattern. This can be key, in a preventive manner, to limit gut functionality decline, or in a curative way to help maintaining optimum nutrients bioavailability in a context on increased requirements, as frequently observed in pathological situations. The aim of this review is to give an overview on the alterations that can occur in the gut during aging and lead to the development of altered function in other tissues and organs, ultimately leading to the development of pathologies. Subsequently is discussed how nutritional strategies that target gut tissue and gut microbiota can help to avoid or delay the occurrence of aging-related pathologies.

Guiding the formulation of soft cereal foods for the elderly population through food oral processing: Challenges and opportunities

As the elderly population is growing steadily, more age-friendly food products that allow them to cover their nutritional needs and are enjoyable need to be designed. Since their oral physiology is considerably altered, the study of Food Oral Processing has become an essential discipline in food development, as it takes into consideration the complex interactions between food structure, oral processing, physiology and perception. Cereals are staple foods in many countries, and their consumption as bakery products is popular among the elderly population. In addition, when fortified with pulse proteins, they can help meet the protein needs of seniors and help fight against sarcopenia. For these reasons, this chapter presents an overview of the various aspects involved in the oral processing and formulation of soft cereal foods, translating them into challenges and opportunities that are of relevance to the design of realistic soft cereal foods targeted for the elderly that are nutritious and sensory appealing. This review focuses on the healthy elderly population and does not intend to cover the needs of the dependent elderly suffering from chronical diseases.