Plain English Summary
Background and study aims
Low vegetable consumption is a considerable health problem worldwide. A diet low in vegetables is associated with an increased risk of becoming overweight or obese, and other health related chronic diseases. Supermarkets have a major influence on daily food intake, because most foods are purchased in supermarkets. Therefore, supermarkets can be a suitable setting for health interventions to stimulate vegetable purchases. Nudging is an effective strategy to stimulate vegetable purchases. Nudging is simply defined as changes in the environment to alter people’s behavior in a predictable way, without forbidding any options. In this study we investigated the effectiveness of two nudging strategies in supermarket trolleys to stimulate vegetable purchases among supermarket customers.
Who can participate?
Supermarket customers with a shopping trolley and a cash receipt can participate in this study.
What does the study involve?
The intervention in this study consists of a green inlay in shopping trolleys with social norm messages about vegetable purchases of other customers of the supermarket. This will cover the bottom half of each trolley, indicating a place to put vegetables. The intervention days of the study are the days on which the green inlay will be used in the shopping trolleys, and the control days will be the days where there are no inlays (regular shopping trolleys). Cash receipts will be collected and surveys will be conducted among customers after they have paid for their groceries.
What are the possible benefits and risks of participating?
There are no known benefits or risks to participants taking part in this study.
Where is the study run from?
Vrije Universiteit Amsterdam (The Netherlands)
When is the study starting and how long is it expected to run for?
January 2017 to June 2018
Who is funding the study?
Vrije Universiteit Amsterdam (The Netherlands)
Who is the main contact?
Marlijn Huitink
m.huitink@vu.nl
Trial website
Contact information
Type
Scientific
Primary contact
Mrs Marlijn Huitink
ORCID ID
http://orcid.org/0000-0002-5303-9668
Contact details
De Boelelaan 1085
Amsterdam
1081 HV
New Zealand
Additional identifiers
EudraCT number
ClinicalTrials.gov number
Protocol/serial number
None
Study information
Scientific title
Social norm nudges in shopping trolleys to promote vegetable purchases: a supermarket experiment in a deprived urban area in the Netherlands
Acronym
Study hypothesis
We investigated the effectiveness of two nudging strategies in shopping trolleys on the amount of vegetables purchased in a Dutch supermarket in a disadvantaged urban area. The nudges are as follows:
1. A place for vegetables
2. Social norm communication
Ethics approval
The study was conducted according to the ethical standards declared in the Helsinki declaration of 1975, as revised in 2000. Active verbal informed consent was given by all customers. The Medical Ethics Committee of the Vrije Universiteit Amsterdam confirmed that this study does not apply to the Medical Research Involving Human Subjects Act (WMO), due to the nature of the measurements (sales data and anonymous questionnaires distributed among adults). Therefore, approval was waived.
Study design
Interventional non-randomised study
Primary study design
Interventional
Secondary study design
Non randomised study
Trial setting
Other
Trial type
Other
Patient information sheet
No participant information sheet available
Condition
Vegetable sales
Intervention
The intervention consisted of three green inlays, indicating the space where customers can place their vegetables, each with a different social norm message about vegetable purchases of other customers from the participating supermarket. Customers on the intervention days received a shopping trolley with a green inlay with one of the three different social norm messages. The intervention was tested during two days (Friday evening and Saturday morning). The control days used the usual shopping trolleys with no green inlay. Cash receipts were collected and surveys conducted among customers after they had paid for their groceries.
Intervention type
Behavioural
Phase
Drug names
Primary outcome measure
Vegetables purchased (in grams and in items), assessed at the end of each study day over the two-week study period using:
1. Examination of cash receipts
2. Surveys with customers after they had paid for their groceries
Secondary outcome measures
The following were assessed using oral surveys in the supermarket after customers had paid for their groceries over the two-week study period:
1. Customer characteristics:
1.1. Sex
1.2. Age category
1.3. Highest obtained education
2. Customer grocery behaviour characteristics:
2.1. Number of persons and days for which groceries were purchases
2.2. Use of a shopping list or not
2.3. Place customers purchased vegetables most often
2.4. If customers thought that they purchased less, more or the same amount of vegetables during this shopping trip as they usually would
Overall trial start date
01/01/2017
Overall trial end date
01/06/2018
Reason abandoned (if study stopped)
Eligibility
Participant inclusion criteria
Supermarket customers in Amsterdam with a shopping trolley and a cash receipt
Participant type
All
Age group
All
Gender
Both
Target number of participants
244
Participant exclusion criteria
1. Not willing to consent to having photograph of cash receipt taken
2. Purchased groceries for more than 12 persons for one day
Recruitment start date
12/05/2018
Recruitment end date
20/05/2018
Locations
Countries of recruitment
Netherlands
Trial participating centre
Vrije Universiteit Amsterdam
De Boelelaan 1085
Amsterdam
1081 HV
Netherlands
Sponsor information
Organisation
Vrije Universiteit Amsterdam
Sponsor details
De Boelelaan 1085
Amsterdam
1081 HV
Netherlands
Sponsor type
University/education
Website
Funders
Funder type
Not defined
Funder name
Vrije Universiteit Amsterdam
Alternative name(s)
Funding Body Type
Funding Body Subtype
Location
Results and Publications
Publication and dissemination plan
Publication of a research article with submission planned in 2018
IPD sharing statement:
The data sharing plans for the current study are unknown and will be made available at a later date
Intention to publish date
11/09/2018
Participant level data
Not expected to be available
Basic results (scientific)
Publication list