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The rise in interest of plant-based protein foods has been meteoric, often leading to calls to adopt exclusively plant-based diets to reduce the intake of animal-based foods. In addition to impacts on human health, moving to an exclusively plant-based (or indeed animal-based) diet may have detrimental implications in terms of environmental sustainability. The impact of a rapid growth in global population on the sustainability of food systems poses clear consequences for the environment and thus warrants careful consideration at a national and, in some cases, global level. The requirement for high-quality dietary protein in an ageing population to offset chronic disease, such as sarcopenia, is an additional consideration. A reductionist approach to this sustainability issue is to advise a global population switch to plant-based diets. From a dietary protein perspective, the sustainability of different non-animal-derived protein sources is a complex issue. In this review, first we describe the role of dietary protein in combatting the age-related decline in skeletal muscle mass. Next, we explore the efficacy and sustainability of protein sources beyond animal-based proteins to facilitate skeletal muscle remodelling in older age. Taking a holistic approach, we discuss protein sources in terms of the muscle anabolic potential, environmental considerations with a predominant focus on greenhouse gas emissions across the food chain, the relevance of global malnutrition, and nation- and local-specific nutritional needs for dietary protein choices and food systems. Finally, we discuss implications for environmental sustainability and explore the potential of a trade-off between diet quality and environmental sustainability with food choices and recommendations., Competing Interests: Declarations. Ethics approval and consent to participate: Not applicable. Consent for publication: Not applicable. Competing interests: P.T.M receives research funding from The Hut Group and from Trinsic Collagen Ltd relating to animal-derived and non-animal derived protein nutrition. Over the past 5 years, B.P.C has received funding for research from Carbery Food Ingredients Ltd., Biomarine Ingredients Ireland, and Food for Health Ireland. BPC provides consultancy for Whole Supp Ltd. for which he has received a small shareholding. O.C.W has no current conflicts of interest to declare., (© 2024. The Author(s).)

Objective: A 24-hour day is made up of time spent in a range of physical activity (PA) behaviours, including sleep, sedentary time, standing, light-intensity PA (LIPA) and moderate-to-vigorous PA (MVPA), all of which may have the potential to alter an individual's health through various different pathways and mechanisms. This study aimed to explore the relationship between PA behaviours and the gut microbiome in older adults., Design: Cross-sectional study., Settings and Participants: Participants (n=100; age 69.0 [3.0] years; 44% female) from the Mitchelstown Cohort Rescreen (MCR) Study (2015-2017)., Methods: Participants provided measures of gut microbiome composition (profiled by sequencing 16S rRNA gene amplicons), and objective measures of PA behaviours (by a 7-day wear protocol using an activPAL3 Micro)., Results: Standing time was positively correlated with the abundance of butyrate-producing and anti-inflammatory bacteria, including Ruminococcaceae, Lachnospiraceae and Bifidobacterium, MVPA was positively associated with the abundance of Lachnospiraceae bacteria, while sedentary time was associated with lower abundance of Ruminococcaceae and higher abundance of Streptococcus spp., Conclusion: Physical activity behaviours appear to influence gut microbiota composition in older adults, with different PA behaviours having diverging effects on gut microbiota composition., Competing Interests: The authors have no conflicts of interest or competing interests to declare.

Fish protein represents one of the most widely consumed dietary protein sources by humans. The processing of material from the fishing industry generates substantial unexploited waste products, many of which possess high biological value. Protein hydrolysates, such as fish protein hydrolysates (FPH), containing predominantly di- and tripeptides, are more readily absorbed than free amino acids and intact protein. Furthermore, in animal models, FPH have been shown to possess numerous beneficial properties for cardiovascular, neurological, intestinal, renal, and immune health. Ageing is associated with the loss of skeletal muscle mass and function, as well as increased oxidative stress, compromised vascularisation, neurological derangements, and immunosenescence. Thus, there appears to be a potential application for FPH in older persons as a high-quality protein source that may also confer additional health benefits. Despite this, there remains a dearth of information concerning the impact of FPH on health outcomes in humans. The limited evidence from human interventional trials suggests that FPH may hold promise for supporting optimal body composition and maintaining gut integrity. FPH also provide a high-quality source of dietary protein without negatively impacting on subjective appetite perceptions or regulatory hormones. Further studies are needed to assess the impact and utility of FPH on skeletal muscle health in older persons, ideally comparing FPH to 'established' protein sources or a non-bioactive, nitrogen-matched control. In particular, the effects of acute and chronic FPH consumption on post-exercise aminoacidaemia, skeletal muscle protein synthesis, and intramyocellular anabolic signalling in older adults are worthy of investigation. FPH may represent beneficial and sustainable alternative sources of high-quality protein to support skeletal muscle health and anabolism in ageing, without compromising appetite and subsequent energy intake.