Testing the effects of nudging for reduced salt intake among online food delivery customers: a research protocol for a randomized controlled trial
Authors: Li Beisi , Cui Ying , Song Chao , Li Wenyue , Nakagawa Jun , Snider Paige , Liu Ailing , Long Ying , Galea Gauden 
Published: July 2021

ABSTRACTBackgroundChinese people on average consume almost twice as much salt as recommended by the World Health Organization. In recent years, dining out and ordering food online are increasingly popular, especially for urban residents. The aim of this study is to evaluate the effectiveness of different settings on a digital food delivery App in nudging consumers towards reduced salt options through a randomized controlled trial in China.Methods and AnalysisThis is a randomized controlled trial with matched restaurants randomized to five parallel intervention groups plus a control group. Participating restaurants are recruited via open invitation and targeted invitation on a voluntary basis and are free to withdraw from the study at anytime. Each enrolled restaurant can select 1-3 of their most popular dishes to participate in this study. The recruitment ends at the end of June 2021. As of June 30, 285 restaurants enrolled for intervention groups and successfully completed interface set-up requirements. The primary outcome of this study is to investigate the differences in customer ordering behaviors regarding salt preference that result from changing the default settings and/or in combination with health messages before placing the order. The primary outcome will be measured by the difference between the number of regular salt orders and the number of reduced salt orders amongst the five intervention groups, and between each intervention group and the control group. We will collect order data at the end of the 2-month study period from the food delivery App. The secondary outcome is to measure if reduced the salt version of the participating dishes has less salt content than the regular version. The secondary outcome will be measured by lab testing salt content of randomly sampled dishes during the study period. In addition, we will also conduct pre- and post- intervention surveys with participating restaurants to assess their knowledge, attitude, and practice regarding salt reduction, and their perceptions on how such intervention affects their business, if at all. We will not include findings from the pre- and post-intervention interviews as an outcome but will use them to inform future restaurant- based salt reduction promotions.DiscussionThe study will test whether changing in the choice architecture on the digital food ordering platform will promote healthier ordering behavior among consumers. Results on whether user interface modifications can promote purchases of reduced salt dishes may provide evidence to inform future sodium reduction strategies and health promotion interventions on online food ordering platforms, with the potential to apply to offline dining settings. The results may also inform current government efforts to roll out national guidelines on promoting nutrition labeling by restaurants. Despite these strengths in study design, securing the agreement of the food delivery App, recruiting individual restaurants and maintaining compliance to the interface set up through the period of the study proved to be and remains challenging.Trial RegistrationRegistered at the Chinese Clinical Trial Registry at http://www.chictr.org.cn/searchprojen.aspx (No. ChiCTR2100047729)Protocol versionVersion MAY112021.01Strengths and LimitationsThis study presents an innovative and timely intervention package for promoting salt reduction for online meal ordering platform.Our study is one of first in China and globally that tests nudging interventions on online food ordering behavior on a large-scale commercial platform and in a real-world setting.Recruiting restaurants and ensuring their compliance remain challenging.