Examining Individual Factors Influencing Adherence and Response to Wholegrains and Nuts in a Series of Interventional N-of-1 Studies

Abstract Objectives Inter-individual variations in response to dietary interventions are common, which can be affected by physiological and behavioural factors. N-of-1 studies, where a series of measurements are collected on an individual level over time, can provide insights into the factors which affect response for a single volunteer. The MI-DIET study is a series of N-of-1 studies to investigate what factors, at an individual level, influence a) adherence to a wholegrain and nuts intervention and b) blood pressure response. Methods 14 volunteers with mildly elevated blood pressure (120/80–140/90mmHg), and who were low consumers of wholegrain foods, were recruited. Each volunteer carried out a 24-week N-of-1 study, composed of three 8-week periods (observation, intervention and follow-up). Throughout the study, volunteers responded to semi-personalised morning and evening questionnaires using a wrist-worn device (PRO-Diary, CamNtech Ltd.), which also monitored activity levels via actigraphy, and took their blood pressure daily using a wireless monitor (QardioArm, Qardio Inc.). During the intervention period, participants were provided with and asked to consume 3–4 portions of wholegrains and a handful of nuts each day, in line with the Dietary Approaches to Stop Hypertension (DASH) diet. Results To date, 11 volunteers have completed the study, and 2 volunteers have withdrawn. Each volunteer's data is analyzed on an individual level using N-of-1 dynamic modelling analysis. Results to date include a significant association between menstrual cycle day and blood pressure in one volunteer (p < 0.01), while consumption of chocolate or cakes was associated with fewer portions of wholegrains being consumed by another volunteer (p < 0.05). Conclusions Collecting repeated measurements on an individual level can identify relevant predictors of compliance and response to a dietary intervention for a given person. Subsequent aggregated analysis of variables measured across multiple volunteers will enable us to further understand factors which may underpin differential response to dietary interventions. Funding Sources Biotechnology and Biological Sciences Research Council (BBSRC) UK and Unilever Foods Innovation Centre, Wageningen, The Netherlands: Collaborative Training Partnership (CTP) PhD.