Evaluation of interventions in online grocery shopping for sustainability
| ISRCTN | ISRCTN18800054 |
|---|---|
| DOI | https://doi.org/10.1186/ISRCTN18800054 |
| Secondary identifying numbers | AEA RCT Registry, Protocol Exchange |
- Submission date
- 25/03/2024
- Registration date
- 27/03/2024
- Last edited
- 18/03/2025
- Recruitment status
- No longer recruiting
- Overall study status
- Completed
- Condition category
- Nutritional, Metabolic, Endocrine
Plain English Summary
Background and study aims
The food system makes a large contribution to global warming and unhealthy diets cause many preventable deaths in the UK each year. To fix these problems, we need to change what we eat to benefit both people and the environment. Therefore, effective interventions are urgently needed to promote sustainable and healthier food choices. With the rise of online grocery shopping, little is known about intervening effectively in real-life online shopping environments to encourage sustainable and healthier purchasing. This study aims to investigate whether providing environmental impact scores for products and offering discounts can help people make healthier and more sustainable food choices when shopping for groceries online.
Who can participate?
Primary grocery shoppers aged 18 years or older who live in any part of the UK and purchase groceries online.
What does the study involve?
Participants will complete a screening/baseline survey administered online via Qualtrics to assess eligibility and collect data on demographic characteristics. If eligible, they will receive download instructions for a browser extension, which will be used to implement the interventions. After installing the browser extension, participants will complete their normal online grocery shopping on the website of a large UK supermarket over 8 weeks. During this period, the browser extension will collect participants’ grocery purchases. At the end of the intervention period, participants will receive an invitation to complete another online survey about their experiences using the browser extension and the interventions.
What are the possible benefits and risks of participating?
There are no risks involved in participating in this study. By participating, participants will help to identify ways to promote choices in online grocery shopping in the UK that are better for the environment.
Where is the study run from?
University of Warwick (UK)
When is the study starting and how long is it expected to run for?
June 2023 to April 2025
Who is funding the study?
Economic and Social Research Council (UK)
Who is the main contact?
Prof. Thijs van Rens, J.M.van-Rens@warwick.ac.uk
Contact information
Public, Scientific, Principal Investigator
Department of Economics
University of Warwick
Gibbet Hill Road
Coventry
CV4 7AL
United Kingdom
 ORCID ID |
0000-0001-9581-4784 |
|---|---|
| Phone | +44 (0)2476151423 |
| J.M.van-Rens@warwick.ac.uk |
Study information
| Study design | Cross-sectional randomized controlled field trial |
|---|---|
| Primary study design | Interventional |
| Secondary study design | Randomised controlled trial |
| Study setting(s) | Internet/virtual, Retail/food outlet |
| Study type | Prevention |
| Participant information sheet | 45241_PIS_15Jan24.pdf |
| Scientific title | Evaluation of interventions in online grocery shopping for sustainability and health: an adaptive design randomized controlled trial |
| Study acronym | SustainableOnlineGroceries |
| Study hypothesis | The null hypothesis is that eco-labels and price discounts have no effect on the purchase of more sustainable choices against the alternative that these interventions promote more sustainable choices. The two interventions will be independently randomized within the same study population so that these will be two independent tests. The researchers will attempt to also test the hypothesis that both interventions together are more or less effective than the sum of both (factorial design), but they do not expect that this test will be significant with the number of participants that they are able to recruit. |
| Ethics approval(s) |
Approved 26/02/2024, Humanities and Social Sciences Research Ethics Committee (Department of Economics, Coventry, CV4 8UW, United Kingdom; +44 (0)2476524760; Karen.Julian@warwick.ac.uk), ref: HSSREC 123/23-24 |
| Condition | Diet-related disease |
| Intervention | The researchers will evaluate the following two interventions: Eco-labelling: Eco-labels provide consumers with information on the environmental impact of their food purchases, graded from A (lowest impact, most sustainable) to G (highest impact, least sustainable) based on an underlying numerical score ranging from 0 (most sustainable) to 500 (least sustainable). These environmental impact scores were calculated based on the ingredients in 1kg of each product, which are then linked to the life-cycle analysis (LCA) database Agribalyse. The scores take into account the environmental impact of a product in 16 categories, including land use, water scarcity, resource use, human health, wildlife damage, and climate change. Price discounts on more sustainable alternative products: Price discounts will be offered through swaps at the first checkout screen. Participants will see a pop-up window suggesting a more sustainable alternative for a particular product in their basket, which is offered at a randomly varying price discount. The alternative products are selected to not cost £2.00 more than the original product, and price discounts will be offered at three levels: £1.00, £0.50 or no discount. The intention is that this will result in discounts being roughly equally spaced between 0 and 100% of the price difference between the original and the alternative products (explicitly offering percentage discounts is not feasible for technical reasons, because it would involve “live” scraping of the prices). The researchers will use this information to calculate the willingness to pay for more sustainable products. As an example, a participant may be prompted to swap Greek yoghurt (500 g) priced at £2.30 for dairy-free coconut yoghurt (600 g) priced at £3.60, and the pop-up will notify participants that they can buy the coconut yoghurt for £2.60, £3.10 or the full price of £3.60, depending on the trial arm that the participant was assigned to. If the shopper accepts the swap, they will be reimbursed for the price discount. Each participant will get offered a swap for a (potentially discounted) alternative product on up to three products in their shopping basket. The products for which a swap is offered are randomly chosen from a list, composed by the researchers, of not-so-sustainable products with suitable alternatives. To avoid offering alternative products with an inferior macronutrient profile, alternative products on the list will be selected so that they are in the same or a better category for fat, sugar and salt content on the traffic-light label. Participants will be randomly allocated into different arms at the start of the trial using a simple randomisation method. The two interventions will be independently randomised within the same study population so that there are effectively two independent trials. One of these will be a two-arm trial where the researchers will randomly assign half of the sample to the eco-labels group and the other half to the no eco-labels group. The other will be a three-arm trial where roughly one-third of participants will receive a £1.00 price discount, one-third will receive a £0.50 discount, and one-third will not receive a price reduction on the alternative products they are offered. Both interventions will be implemented at the same time over a duration of 8 weeks. |
| Intervention type | Behavioural |
| Primary outcome measure | The average eco-score of the basket of groceries purchased, with a lower score meaning more sustainable purchases. Using this outcome variable, the researchers will estimate the effect size of introducing eco-labels (intervention 1) and the price-elasticity for sustainable alternative products (intervention 2), allowing them to calculate the willingness to pay for sustainable groceries. They aim to measure both short- and long-term responses to price discounts to see if trying a more sustainable alternative may shift demand persistently beyond a one-time purchase. All outcomes will be measured either over the 8-week intervention period or at the end of that period. |
| Secondary outcome measures | 1. Basket eco-score for 16 impact categories of the Product Environmental Footprint (PEF): climate change, water use, resource use: minerals and metals, resource use: fossils, land use, ozone depletion, human toxicity: cancer, human toxicity: non-cancer, ionising radiation and human health, particulate matter, eutrophication: marine, acidification, eutrophication: terrestrial, eutrophication: freshwater, ecotoxicity: freshwater). This outcome will give some insight into what type of improvements can be expected from more sustainable grocery shopping because of the interventions. It is likely that the largest sustainability gains can be realised on the impact category climate change (greenhouse gas emissions). 2. The nutritional value of the basket of groceries purchased, as measured by the Food Standard Agency’s (FSA) Nutrient Profiling Model. The researchers will use the changes in the nutritional composition of groceries purchased to model the health impact of their interventions if these were delivered at scale in the UK using the PRIMEtime model, a multi-state life table model, to calculate the impact of the interventions on diet-related diseases. 3. Total cost of the shopping basket: The total cost of the shopping basket per household expressed in £ will be used to understand the impact on grocery costs. 4. Total number of products in the basket. This is primarily to check whether shoppers respond to eco-labels by buying more (less sustainable) products elsewhere (e.g. by adding them to their order on the mobile or by buying them at a different supermarket). All outcomes will be measured either over the 8-week intervention period or at the end of that period. |
| Overall study start date | 01/06/2023 |
| Overall study end date | 14/04/2025 |
Eligibility
| Participant type(s) | Population |
|---|---|
| Age group | Adult |
| Lower age limit | 18 Years |
| Sex | Both |
| Target number of participants | 2760 |
| Participant inclusion criteria | 1. Be 18 years or older and located in the UK 2. Be the primary grocery shopper of their household 3. Frequently buy groceries online (at least once per month, self-reported) 4. Usually shop at the supermarket(s) included in this study 5. Usually use a laptop or desktop with the Google Chrome browser for online grocery shopping or be willing to do so for the duration of the study 6. Consent to participate and be willing to download and install the plug-in and use it for the duration of the study |
| Participant exclusion criteria | Has participated in the pilot study or previous wave(s) of the study |
| Recruitment start date | 15/04/2024 |
| Recruitment end date | 30/11/2024 |
Locations
Countries of recruitment
- England
- United Kingdom
Study participating centre
Gibbet Hill Road
Coventry
CV4 7AL
United Kingdom
Sponsor information
Government
Polaris House
North Star Avenue
Swindon
SN2 1UJ
England
United Kingdom
| Phone | +44 (0)1793 413114 |
|---|---|
| esrcenquiries@esrc.ukri.org | |
| Website | https://www.ukri.org/councils/esrc/ |
"ROR" |
https://ror.org/03n0ht308 |
Funders
Funder type
Research council
Government organisation / National government
- Alternative name(s)
- ESRC
- Location
- United Kingdom
Results and Publications
| Intention to publish date | 31/03/2025 |
|---|---|
| Individual participant data (IPD) Intention to share | Yes |
| IPD sharing plan summary | Published as a supplement to the results publication |
| Publication and dissemination plan | Planned publication in a high-impact peer-reviewed journal |
| IPD sharing plan | The datasets generated and analysed during the current study will be published as a supplement to the results publication |
Study outputs
| Output type | Details | Date created | Date added | Peer reviewed? | Patient-facing? |
|---|---|---|---|---|---|
| Other files | Reports on PPI engagements | 27/03/2024 | No | No | |
| Other files | Survey questionnaires | 15/01/2023 | 27/03/2024 | No | No |
| Other files | Sustained scoring methodology - Consumer | 27/03/2024 | No | No | |
| Other files | Topic Guide for SALIENT Common Process Evaluation | 27/03/2024 | No | No | |
| Participant information sheet | 15/01/2024 | 27/03/2024 | No | Yes | |
| Protocol file | 27/03/2024 | No | No | ||
| Statistical Analysis Plan | 04/04/2024 | 04/04/2024 | No | No |
Additional files
- 45241_PIS_15Jan24.pdf
- 45241_PROTOCOL.pdf
- 45241 Reports on PPI engagements.pdf
- Reports on PPI engagements
- 45241 Survey questionnaires 15Jan2023_clean.pdf
- Survey questionnaires
- 45241 Topic Guide for SALIENT Common Process Evaluation.pdf
- Topic Guide for SALIENT Common Process Evaluation
- 45241 Sustained scoring methodology - Consumer.pdf
- Sustained scoring methodology - Consumer
- ISRCTN18800054_SAP_04Apr24.pdf
Editorial Notes
18/03/2025: The overall end date was changed from 31/03/2025 to 14/04/2025.
04/04/2024: Statistical analysis plan uploaded.
26/03/2024: Study's existence confirmed by the Humanities and Social Sciences Research Ethics Committee.
