Implications of replacing animal-sourced foods in the diet of the older population, focusing on protein intake and muscle mass : A multi-methods study of the available evidence and empirical data from Kigali, Rwanda

Abstract

Bakgrunn: Inntak av animalske matvarer som inneholder proteiner av høy kvalitet, kan bidra til å forbedre proteininntaket og bevare muskelmassen hos eldre. På den annen side oppfordres forbrukere til å erstatte animalske proteiner med plantebaserte matvarer i kostholdet på grunn av den høyere miljøbelastningen. Dagens retningslinjer er basert på forskning fra høyinntektsland. Det er imidlertid ikke undersøkt hvilke konsekvenser det kan ha for det totale proteininntaket og muskelmassen å erstatte animalske matvarer fra kostholdet til eldre voksne. Målsetting: Målet med denne doktorgradsavhandlingen var å undersøke de kostholdsmessige og ernæringsmessige konsekvensene av å erstatte animalske matvarer i kostholdet til den eldre befolkningen, med særlig fokus på proteininntaket og kroppssammensetningen hos middelaldrende og eldre voksne. Vi ville også forstå dette med perspektiver fra et lavinntektsland. Metoder: I artikkel I ble det brukt en systematisk oversikt og metaanalysemetodikk for å evaluere dokumentasjonen for effekten av å redusere inntaket av kjøtt og/eller meieriprodukter på proteininntaket og kroppssammensetningen. I artikkel II ble det gjennomført en tverrsnittsundersøkelse av kostholdet for å vurdere inntaket av animalske matvarer og sammenhengen med proteininntak og muskelmasse hos eldre voksne. I artikkel II ble det gjennomført en kvalitativ studie for å undersøke eldre menneskers oppfatning av kjøttinntaket i kosten. Resultater: I de kvantitative studiene observerte vi at det å erstatte animalske matvarer i kostholdet var proporsjonalt forbundet med en reduksjon i det totale proteininntaket. Metaanalysen viste ingen evidens for effekten av å redusere inntaket av kjøtt og/eller meieriprodukter på kroppssammensetningen. Derimot viste kostholdsundersøkelsen at inntak av animalske matvarer var positivt assosiert med skjelettmuskelmasse. Tre temaer ble identifisert i den kvalitative studien, og de var knyttet til opplevd tilgjengelighet og pris på kjøtt samt motiver og barrierer for kjøttforbruk. Konklusjon: Funnene i denne avhandlingen viste at ASF spiller en uerstattelig rolle i kostholdet til eldre voksne i både høy- og lavinntektsmiljøer. Det var konsistente bevis for at det å erstatte animalske matvarer i kostholdet kan ha en negativ innvirkning på det proteininntaket hos eldre voksne. Det var imidlertid blandede resultater når det gjaldt effekten på muskelmassen.Background: The proportion of the older population is increasing both in high- and low-income countries. This population is at high risk of different forms of nutrition-related disorders, including muscle wasting and functional decline. Consumption of animal-sourced foods (ASFs), providing high-quality proteins, can contribute to improving protein intake and preserving muscle mass in older adults. On the other hand, consumers are being encouraged to replace ASFs with plant-based foods in their diets, a shift known as protein transition, because of their higher environmental burden. Current discourse on potential implications of this dietary shift on dietary intake and body composition of older population are based on research conducted mostly in high-income countries. The implications of replacing ASFs in the diet of older adults on their total (absolute) protein intake and muscle mass, particularly in low-income countries, have not been investigated. Data integrating both low- and high-income settings are needed to enrich scientific understanding and stimulate an inclusive discourse on the impact of protein transition on global aging. Objective: The aim of this PhD thesis was to investigate the implications of replacing ASFs in the diet on dietary intake and body composition of the older population, focusing on protein intake and muscle mass. Methods: In paper I, a systematic review and meta-analysis methodology were applied to evaluate evidence for the effect of reducing meat and/or dairy in the diet on the protein intake and body composition in middle-aged and older adults (aged ≥ 45 years). In Paper II, a cross-sectional (dietary) survey was conducted in Gasabo district, Rwanda, to assess the associations between ASF consumption and protein intake and muscle mass in community-dwelling older adults (aged ≥ 55 years). In Paper III, a qualitative study was also conducted in Gasabo district, Rwanda, to explore perceptions of dietary meat consumption in community-dwelling older adults (aged ≥ 55 years). Results A total of 1,475 middle-aged and older adults (aged ≥ 45 years), mostly from HICs, were enrolled in the RCTs summarized in Paper I, while Paper II included 334 older adults (median age: 65 years) from Gasabo district. The findings of these two papers (quantitative studies) showed that replacing or lacking ASFs in the diet was proportionally associated with a decrease in total protein intake. In Paper I, there was no evidence of the effect of reducing meat and/or dairy consumption on muscle mass. In contrast, Paper II found that ASF consumption was positively associated with skeletal muscle mass. Paper III included 64 older adults. Three themes were identified in Paper III, relating to the perceived accessibility and affordability of meat, as well as the motives for and barriers to meat consumption. Conclusion: The findings of Papers I and II show that ASFs play an important role in the diet of older populations in both high-and low-income settings. There was consistent evidence that replacing ASFs in the diet was associated with a decrease in total (absolute) protein intake of the study populations. There was, however, mixed evidence of the effect on muscle mass. Similarly, in Paper III, although ASF consumption was perceived to be low and declining among older adults compared to past decades, the motives for ASF consumption were perceived to be related to the role played by ASFs in sensorially and nutritionally improving diet quality, as well as in strengthening social relationships.Doktorgradsavhandlin