Nudging plant-based protein purchases in a real-life online supermarket
| ISRCTN | ISRCTN16569242 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN16569242 |
| Secondary identifying numbers | 2021.0703 |
- Submission date
- 02/02/2022
- Registration date
- 14/03/2022
- Last edited
- 21/02/2024
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Other
Plain English summary of protocol
Background and study aims
For challenges of environmental sustainability and health perspective, a shift from consumption of animal-based to plant-based proteins is widely acknowledged to be necessary. Food consumption is heavily influenced by our social and physical environments, for example in terms of availability, price, and social acceptance. One of our food environments is supermarkets, where people buy protein products on a daily or weekly basis. Previous research has shown that adjustments in supermarket environments can affect purchasing behavior towards healthier choices. In addition, experiments in virtual supermarkets and canteens have shown that certain choice architecture (i.e., nudging) strategies can promote plant-based protein choices in terms of products or meals. However, the impacts of nudging strategies on plant-based protein purchases have rarely been studied in real-life settings. Moreover, while previous research found that a combination of nudges can be more effective in changing behavior than a single nudge, most nudges have been studied separately. Therefore, this study will expand existing knowledge by investigating the real-life effect of a combined nudging strategy on plant-based protein purchases relative to animal-based purchases in an online supermarket.
Who can participate?
All customers of the participating online supermarket chain.
What does the study involve?
Customers visiting the online supermarket are randomly allocated to:
1. No intervention (regular online supermarket)
2. Addition of three types of nudges (placement, social norm and properties)
During an 8-week study period sales data are collected from all customers placing a delivery order in the online supermarket. Including a 16-week follow-up measurement.
What are the possible benefits and risks of participating?
The study does not involve direct benefits or risks for the participants.
Where is the study run from?
National Institute for Public Health and the Environment (RIVM) (the Netherlands)
When is the study starting and how long is it expected to run for?
September 2021 to September 2022
Who is funding the study?
National Institute for Public Health and the Environment (RIVM) (the Netherlands)
Who is the main contact?
Nina van der Vliet
nina.van.der.vliet@rivm.nl
Contact information
Scientific
Antonie van Leeuwenhoeklaan 9
Bilthoven
3721 MA
Netherlands
 ORCID ID |
0000-0002-8990-0907 |
|---|---|
| Phone | +31 615082380 |
| nina.van.der.vliet@rivm.nl |
Study information
| Study design | A two-arm parallel-group individually randomized controlled trial |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Randomised parallel trial |
| Study setting(s) | Internet/virtual |
| Study type | Prevention |
| Participant information sheet | Not available in web format, please use contact details to request a participant information sheet. |
| Scientific title | Nudging plant-based protein purchases in a real-life online supermarket: a randomized controlled trial |
| Study acronym | SHIFT-diets |
| Study objectives | We will primarily evaluate whether the implementation of nudges will result in a between group mean-difference in the number of plant-based protein purchases in an online supermarket. As secondary outcome, we will evaluate between groups the mean-differences in the number of purchased plant-based meat replacements, animal-based meat products, plant-based dairy purchases, and animal-based dairy purchases. As a tertiary outcome we will investigate the mean-differences in retailer revenue as a relevant business related outcome. In addition, we will explore if potential effects are sustained after the intervention period has ceased and investigate potential interactions with the primary outcome for neighborhood socio-economic position (SEP), age and sex. |
| Ethics approval(s) | Approved 26/01/2022, The Medical Ethics Review Committee of VU University Medical Center (De Boelelaan 1109, kamer 08A-08, Postbus 7057, 1081 HV Amsterdam, the Nteherlands; +31 20 444 5585; metc@vumc.nl), ref: 2021.0703 |
| Health condition(s) or problem(s) studied | Promoting plant-based protein products among the general population |
| Intervention | Current interventions: Arm 1: Regular online supermarket (control). Arm 2: Online supermarket with the addition of nudges on plant based protein products. Randomization and allocation is performed by supermarket e-commerce employees, using a software tool names Blueconic. Randomization is based on participants’ browser cookies. In the control group, shoppers encounter the unadjusted online shopping environment as it currently is. Participants that are randomized to the intervention group will shop in an adjusted online supermarket website, in which a combination of three nudging strategies are present. The different nudging strategies focus on prominence, dynamic social norms and properties. Prominence nudge First, we will install a prominence nudge, meaning that at two points on the supermarket website, the product categories of plant-based protein products (plant-based meat alternatives and plant-based dairy alternatives) are placed more prominently when navigating the main category called ‘ Meat, chicken, fish and vegetarian” and when navigating the main category called ‘Dairy, butter and eggs’. Dynamic social norms nudge Secondly, we will install a dynamic social norms nudge by means of a label on products. Based on sales data of all plant-based dairy and meat alternatives in the period before starting the experiment, we will select the 50% most sold products in several product categories. Categories included for example vegetarian minced meat, vegetarian schnitzel or burgers, plant-based drink and vegetarian snacks. These products will be provided with a label in Dutch that translates to ‘Increasingly chosen’ (in Dutch: ‘Steeds vaker gekozen’). In addition to the label, on 11 product category overview pages (for example, potatoes, pasta, rice, coffee), a purple-colored frame, from now on called a ‘ toaster’ will be shown on the top right side of the page. When clicked on by the shopper, this toaster will direct shoppers to plant-based alternative category pages, that are relevant for the product page. The different toasters each will show two images of relevant plant-based meat- or dairy replacement products. Properties nudge Regarding properties, a nudging strategy will be used in the form of a tastiness product label on the frame. Besides the text ‘Increasingly chosen’ / ‘Steeds vaker gekozen’, an additional text is shown saying: ‘Have a look at these tasty products’/ ‘Bekijk ook deze lekkere producten’. This so-called frame will be installed on the top left side of three main category pages (Meat, chicken, fish and vegetarian products; freezer products; dairy products). Previous interventions: Arm 1: Regular online supermarket (control). Arm 2: Online supermarket with the addition of nudges on plant based protein products. Randomization and allocation is performed by supermarket e-commerce employees, using a software tool names Blueconic. Randomization is based on participants’ browser cookies. In the control group, shoppers encounter the unadjusted online shopping environment as it currently is. Participants that are randomized to the intervention group will shop in an adjusted online supermarket website, in which a combination of three nudging strategies are present. The different nudging strategies focus on placement (increasing availability and prominence), social norms, and properties. Placement nudges Firstly, we will use a prominence (position) nudge, entailing that plant-based protein products are placed more prominently when searching for (animal-based) protein products groceries or navigating towards animal-based protein products (for example, plant-based chicken-like pieces are presented when searching for chicken). Secondly, we will also use an availability nudge in combination with the prominence nudge, entailing multiple plant-based protein product alternatives are suggested when navigating or searching animal-based protein products, thereby increasing the availability of these products. Social norm nudge We will install a dynamic social norms nudge. When navigating or searching for animal-based products, plant-based alternatives will be suggested between the results with a label ‘Increasingly chosen' (Dutch translation: 'Steeds vaker gekozen’). In addition, there will be a frame linking to two plant-based products with the label ‘Increasingly chosen’. Properties nudge We will install a tastiness product label. On the previously described frame linking to plant-based products with the label ‘Increasingly chosen’, an additional text is installed saying: ‘Also have a look at these tasty products’ (Dutch translation: ‘Bekijk ook deze lekkere producten’). Furthermore, within other categories (e.g. pasta, rice, potatoes, vegetables, coffee), a frame will be installed that suggests plant-based products and contains the label ‘Have a look at these tasty products’ |
| Intervention type | Behavioural |
| Primary outcome measure | The number of plant-based protein products purchased measured using the online shopping website at a single time point |
| Secondary outcome measures | Measured using the online shopping website at a single time point: 1. The number of purchases from (a) meat, (b) plant-based meat substitutes, (c) dairy products, and (d) plant-based dairy products. 2. Total revenue in Euros. |
| Overall study start date | 01/09/2021 |
| Completion date | 22/09/2022 |
Eligibility
| Participant type(s) | All |
|---|---|
| Age group | Adult |
| Sex | Both |
| Target number of participants | With 80% power and a two-sided type 1 error rate of 0.05, the trial would require 768 participants in each trial arm, resulting in 1,537 participants in total. All participants will be invited to fill out a survey. Based on an expected response rate of 10%, we expect to collect data from circa 540 up to 870 questionnaires. |
| Total final enrolment | 3502 |
| Key inclusion criteria | Current inclusion criteria as of 13/06/2022: All customers placing a delivery order (i.e., shops) in a real-life online supermarket between mid May 2022 until mid September 2022. Previous inclusion criteria: All customers placing a delivery order (i.e., shops) in a real-life online supermarket between mid February 2022 until mid June 2022. |
| Key exclusion criteria | Does not meet inclusion criteria |
| Date of first enrolment | 18/05/2022 |
| Date of final enrolment | 22/09/2022 |
Locations
Countries of recruitment
- Netherlands
Study participating centres
Bilthoven
3721 MA
Netherlands
Amsterdam
1081 HV
Netherlands
Wageningen
6708 PB
Netherlands
Sponsor information
Research organisation
Antonie van Leeuwenhoeklaan 9
Bilthoven
3721 MA
Netherlands
| Phone | +31 (0)30 274 9111 |
|---|---|
| info@rivm.nl | |
| Website | http://www.rivm.nl/en/ |
"ROR" |
https://ror.org/01cesdt21 |
Funders
Funder type
Other
No information available
Results and Publications
| Intention to publish date | 15/02/2023 |
|---|---|
| Individual participant data (IPD) Intention to share | No |
| IPD sharing plan summary | Not expected to be made available |
| Publication and dissemination plan | One or two planned publications in high-impact, preferably open access, peer-reviewed journal |
| IPD sharing plan | The datasets generated during and/or analysed during the current study are not expected to be made available due to confidentiality agreements with the collaboration supermarket chain |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Statistical Analysis Plan | 07/02/2022 | No | No | ||
| Results article | 17/02/2024 | 21/02/2024 | Yes | No |
Additional files
Editorial Notes
21/02/2024: Publication reference added.
09/01/2023: The intention to publish date was changed from 01/01/2023 to 15/02/2023.
09/11/2022: The following changes were made to the trial record and the plain English summary was updated accordingly:
1. The overall trial end date was changed from 17/10/2022 to 22/09/2022.
2. Total final enrolment was added.
13/06/2022: The following changes were made to the trial record:
1. The interventions were changed.
2. The inclusion criteria were changed.
3. The recruitment start date was changed from 14/02/2022 to 18/05/2022.
4. The recruitment end date was changed from 17/06/2022 to 22/09/2022.
22/03/2022: The contact address was changed.
07/02/2022: Trial's existence confirmed by Amsterdam UMC.
