Primary researchers (at Bristol) : Dr Charlotte Buckley, Professor Jeff Brunstrom (Co I)

External Collaborators:

Professor Emma Stevenson (PI) & Dr Anthony Watson, Newcastle University

Professor Alex Johnstone (Co I), University of Aberdeen

Dr Mark Green (Co I), University of Liverpool

Dr Bernard Corfe (Co I) & Dr Liz Williams (Co I), University of Sheffield

The decline of muscle mass/strength is a key component of healthy ageing and can have a major impact on quality of life. Increasing protein intake at all stages of the life course may help to reduce the rate of muscle decline and the onset of associated health conditions. However, there is a lack of understanding of the social, demographic and psychological drivers of food choices surrounding protein intake during ageing. 

Protein for life is a collaborative project led by Newcastle University with academic collaborators from The Universities of Bristol, Sheffield, Liverpool and Aberdeen. This project is also supported by seven industry stakeholder partners. The multidisciplinary team of researchers will assess the factors related to protein intake of three different life stages: mid-life (40-54 years), younger old (55-69 years), and older old (70 + years).

At Bristol we will use techniques drawn from experimental psychology to develop predictive models of food choice. To understand and quantify the relative role of factors such as nutritional composition, expected satiety and other influences we will use psychophysical methods that have been developed at the University of Bristol. A range of foods are photographed and then presented to participants over a series of trials in a two-alternative forced-choice task. The expected satiety of the foods is also measured, along with an assessment of their anticipated healthiness, palatability, and calorie content. For each participant, binary logistic regression is used to estimate the relative weighting that is placed on each variable. By comparing models across groups of participants it is possible to expose subtle differences in ‘food-choice architecture.’

In an initial phase we will use a similar approach to explore the choice architecture of afternoon snack foods. To assess test-retest reliability commonly consumed snacks will be selected and assessed by healthy young volunteers on two separate occasions. Independent of any direct effect on palatability, the energy density of food is also likely to play an important role in food choice (Charbonnier et al., 2015). A potential concern is that modelling overall energy content masks subtle differences in the value that is placed on individual macronutrients. Evidence for macronutrient-specific appetites (especially for protein) is mixed (Berthoud et al., 2012; Carreiro et al., 2016). Nevertheless, one possibility is that the value that is placed on a calorie of fat, carbohydrate, and protein differs, and this may vary with age. The choice-architecture paradigm could be ideally placed to identify evidence of this kind and therefore we will explore the feasibility of modelling responses to individual macronutrients.

In a second phase we will use our methods in a larger study that will aim to quantify determinants of food choice in groups of mid-life (40-54 years), younger old (55-69 years), and older old (70 + years) healthy participants. In so doing our objective is to characterise the developmental trajectory of food-choice strategies in healthy aging, with particular focus on the relative role of energy density and protein as independent drivers of choice. Measures of trait dietary behaviours will be obtained, together with anthropometric data including an assessment of BMI and body composition, to investigate how these relate to food-choice strategies.

Project website: https://research.ncl.ac.uk/proteinforlife/