ISRCTN - ISRCTN56596945: Promotion of fruit and vegetable consumption among low income groups using a pricing strategy

Plain English Summary

Background and study aims:
A sufficient intake of fruits and vegetables forms one of the principal components of dietary recommendations. In the USA and Europe, intake of fruits and vegetables are far below the minimum recommended levels. Increasing the intake of these products to meet dietary recommendations could reduce the burden of some diseases. There is growing opinion that making fruits and vegetables cheaper may be a good strategy to promote their purchase. Mainly consumers with a lower socio economic status perceive fruits and vegetables to be expensive and indicate they would buy more of those products if they would become cheaper. Evidence on the true effects of making healthy foods cheaper is limited and mostly restricted to small scale studies.

Who can participate?
Adults, who could speak Dutch, had a lower socio-economic status and were regular shoppers at the supermarkets that joined this study.

What does the study involve?
We conducted an experiment on the effects of providing a 50% discount on fruits and vegetables, and we tested the additional effect of nutrition education.

What are the possible benefits and risks of participating?
Participants will benefit from cheaper fruit and vegetables, and a more balanced diet. There are no known risks associated with participating in the study.

Where is the study run from?
Four supermarkets in the Netherlands.

When is the study starting and how long is it expected to run for?
The study started in September 2010 and ended in July 2011.

Who is funding the study?
Netherlands Organization for Health Research and Development (ZonMw).

Who is the main contact?
Dr Ingrid Steenhuis
ingrid.steenhuis@vu.nl

Trial website

Contact information

Type

Scientific

Primary contact

Dr Ingrid Steenhuis

ORCID ID

Contact details

VU University Amsterdam
De Boelelaan 1085
Amsterdam
1081 HV
Netherlands
ingrid.steenhuis@vu.nl

Additional identifiers

EudraCT number

ClinicalTrials.gov number

Protocol/serial number

NL22568.029.08

Study information

Scientific title

Promotion of fruit and vegetable consumption among low income groups using a pricing strategy: a randomized controlled trial

Acronym

Study hypothesis

The study examines whether price discounts and nutrition education are effective in stimulating fruit and vegetable purchases among low income groups.

Hypotheses:
1. Lowering the price of fruits and vegetables will lead to higher purchases of these products
2. Nutrition education will lead to higher purchases of fruits and vegetables, but not in the same amount as the price discounts
3. Price discounts on fruits and vegetables combined with nutrition education will provide the largest increase in fruit and vegetable purchases

Ethics approval

Medical Ethical Commitee of the VU Medical Centre Amsterdam,12 February 2009

Study design

Parallel single-center randomized controlled trial

Primary study design

Interventional

Secondary study design

Randomised controlled trial

Trial setting

Other

Trial type

Quality of life

Patient information sheet

Not available in web format, please use the contact details below to request a patient information sheet

Condition

Obesity, Healthy diet

Intervention

The trial contained four research arms:
1. Price discounts on fruits and vegetables
2. Nutrition education with a special focus on fruits and vegetables
3. Price discounts on fruits and vegetables plus nutrition education
4. Control (no intervention)

The nutrition education consisted of two elements, being recipe books and telephone counseling. This telephone counseling consisted of four different calls, taking around 20 minutes each, that were conducted by a qualified dietitian.

The pricing intervention consisted of a 50% discount on fruits and vegetables. The discounts were provided to the participants by use of specifically designed coupons. Participants were sent discount coupons for seven types of vegetables and five types of fruits every two weeks. The coupons were sent by post and participants were provided with two coupons for each item.

Intervention type

Other

Phase

Not Applicable

Drug names

Primary outcome measure

1. Purchases of fruit and vegetables (grams): measured at baseline, 1 month, 3 months, 6 months (end of intervention) and 9 months (3 month follow-up) using cash receipts and schemes listing purchased fruits and vegetables during a two-week period
2. Intake of fruit and vegetables (grams) measured at baseline, 1 month, 3 months, 6 months (end of intervention) and 9 months (3 month follow-up) using a validated shortened Food frequency questionnaire (FFQ) specifically developed for fruit and vegetable intake

Secondary outcome measures

1. The concepts of TBP (attitudes, social norm, and perceived behavioral control) were measured as proposed by Conner and Sparks (1996)
2. Behavioral intention and awareness of own consumption levels were measured in accordance with earlier studies (see Brug et al. 2006)
3. Levels of action planning and levels of coping planning were measured as proposed by Scharzer and Renner
4. Some additional concepts that previously have found to be of importance in food pricing studies were measured, being levels of habit strength (using scal of Verplanken) and price perception (using scale of Lichtenstein). Scores for all these concepts were measured by summing the scores of the relevant items and dividing this by the number of relevant items. All items were measured on a 5 point Likert scale
5. Finally, participants were asked to report some basic personal characteristics, their use of the discount coupons, their evaluation of the nutrition education, and frequency of shopping at the participating supermarket

Overall trial start date

01/09/2010

Overall trial end date

01/07/2011

Reason abandoned (if study stopped)

Eligibility

Participant inclusion criteria

1. Adults (18 years or older)
2. Familiar with the Dutch language
3. Lower socio-economic status (based on education level and working status)
4. Regular shoppers at the participating supermarkets

Participant type

Patient

Age group

Adult

Gender

Both

Target number of participants

180

Participant exclusion criteria

Does not meet inclusion criteria

Recruitment start date

01/09/2010

Recruitment end date

01/07/2011

Locations

Countries of recruitment

Netherlands

Trial participating centre

VU University Amsterdam
Amsterdam
1081 HV
Netherlands

Sponsor information

Organisation

Netherlands Organisation for Health Research and Development (ZonMw) (Netherlands)

Sponsor details

Laan van Nieuw Oost-Indië 334
Postbox 93 245
The Hague
2509 AE
Netherlands
+31 (0)70 349 51 11
info@zonmw.nl

Sponsor type

Government

Website

http://www.zonmw.nl/en/

Funders

Funder type