Promoting Sustainable Dietary Choices Through Label Awareness and Product Trial Incentives: Evidence from a Randomized Controlled Trial

RCT: Information and Voucher Treatments
The independent variables consist of two experimentally assigned interventions designed to influence consumers' purchasing behavior. Participants are randomly assigned to one of four conditions in a 2×2 factorial design, varying the presence of (1) an informational intervention and (2) an incentive-based experiential exposure intervention.
The four treatment conditions are:
1. Control group: Participants receive no intervention and proceed directly to the choice experiment.
2. Information treatment (Eco-Score sustainability label information): Participants are shown a screen explaining the Eco-Score sustainability label, which summarizes the environmental impact of food products based on multiple life-cycle indicators (greenhouse gas emissions, water use, land use, biodiversity impacts, transport distance, storage and packaging, and animal welfare). The screen explains the label's A+ to E− scale and that it is developed by Beelong. To illustrate how the label enables comparisons across products, the screen displays two product images side by side: one plant-based product with an A+ Eco-Score (randomly drawn from: Tofu, plant-based strips, or plant-based mince) and one conventional meat product with an E- Eco-Score (randomly drawn from: chicken or beef). Both images are independently randomized across respondents and are zoomable for closer inspection.
3. Voucher treatment (incentive-based experiential exposure intervention): Participants once receive a voucher with plant-based meat substitutes redeemable free of charge at any at any store operated by the retail collaboration partner store for the following two products per voucher: (1) Plant-Based Vegan Alternative to Mince and (2) Plant-Based Organic Vegan Alternative to Kebab. The voucher is designed to lower financial and behavioral barriers to trial, thereby inducing direct product experience with PBMS. Participants can download the voucher directly within the survey; providing an email address to receive the vouchers by email is optional.
4. Voucher + Information treatment: Participants in this group receive both the information intervention and the voucher intervention described above.
This 2×2 design allows the study to separately identify the causal effect of information provision, the causal effect of incentivized product trial, and their potential interaction. Random assignment ensures that outcome differences across groups can be interpreted causally.

Choice Experiment: Product Attributes and Naming
The survey includes a discrete choice experiment (DCE) examining how consumers evaluate key attributes of plant-based meat substitutes (PBMS) and how linguistic framing influences product preferences. Participants complete three choice rounds. In each round, two hypothetical PBMS products are presented side by side in a comparison table, varying across six experimentally randomized attributes. Participants indicate which product they would be more likely to purchase and additionally rate the purchase likelihood of each product on a 7-point scale (1 = very unlikely to 7 = very likely).
The six product attributes and their levels are:
Attribute: Levels
Product type: Tofu · Plant-based strips · Plant-based mince · Plant-based kebab · Plant-based nuggets
Price: CHF 2.50 (1.00/100g) · CHF 3.75 (1.50/100g) · CHF 5.00 (2.00/100g) · CHF 6.25 (2.50/100g) · CHF 7.50 (3.00/100g)
Protein source: Pea protein · Lentil protein · Soy protein · Lupin protein
Origin of raw materials: Switzerland · European countries · Non-European countries
Eco-Score rating: A+ · A− · B+ · B−
Organic certification: Yes · No
The Attribute levels are randomly and independently drawn for each product in each round, ensuring independent variation across attributes.
Naming treatment (2×2 between-subjects):
In addition to the attribute variation, participants are randomly assigned to one of four product naming conditions that manipulate (1) the language of product names (Hybrid vs. Swiss national language) and (2) whether names include meat-referencing terminology (e.g., "chicken" or "beef") or not. This results in the following conditions:
Condition: Language. Meat reference. Example (GER)
T1: National language, No, Pflanzliches Geschnetzeltes
T2: Hybrid, No, Plant-based Geschnetzeltes
T3: National language, Yes, Pflanzliches Poulet-Geschnetzeltes
T4: Hybrid, Yes, Plant-based Chicken Geschnetzeltes
This design allows the study to estimate both the relative importance of individual product attributes for stated purchase likelihood and whether linguistic framing independently affects consumer evaluations of PBMS.

2026-06-02

2026-06-24

RCT: Information and Voucher Treatments
The primary outcomes relate to observed food purchasing behavior, measured using individual-level purchasing data obtained from our retail collaboration partner. The data include detailed information on product purchases over time and allow us to track changes in purchasing patterns before and after the experimental intervention. Our main outcomes of interest are:
• Eco-Score of food purchases: Using product-level Eco-Score ratings, we measure the overall environmental sustainability of purchased food products, operationalized as the average Eco-Score value across purchased items or as the share of purchased products with favorable Eco-Score ratings. This is the primary outcome corresponding to the information treatment, as the treatment is expected to increase the cognitive accessibility of the Eco-Score as a decision criterion.
• Plant-based meat substitute purchases: We measure the quantity and spending on plant-based meat substitute (PBMS) products purchased by individuals. This outcome captures the adoption effect of the interventions, reflecting whether participants increase their consumption of plant-based alternatives following exposure to the treatments.
• Conventional meat purchases: We measure the quantity and spending on conventional meat products purchased by individuals. This outcome captures the substitution effect, indicating whether participants reduce meat consumption after receiving the interventions.


Choice Experiment: Product Attributes and Naming
The survey also includes a discrete choice experiment designed to measure stated preferences for plant-based products.
• Product choice: In each choice task, respondents select the product they would be most likely to purchase from two alternatives. The primary outcome in the choice experiment is the probability that a given product profile is chosen.
• Purchase likelihood ratings: After each choice task, respondents rate the likelihood that they would purchase each product on a 7-point scale ranging from "very unlikely" to "very likely." These ratings provide an additional measure of stated consumer preferences.
These outcomes allow us to estimate how different product attributes, specifically product type, price, protein source, origin of raw materials, Eco-Score rating, organic certification, and naming conventions, influence consumer preferences for PBMS and other plant-based products.

RCT: Information and Voucher Treatments
In addition to the primary outcomes, we examine the following secondary outcomes:
• Voucher redemption: We measure whether participants in the voucher treatment groups redeem the voucher provided in the experiment. This variable serves as a compliance measure and allows us to assess the extent to which participants actually engage with the experiential component of the voucher treatment, which is a necessary condition for the experiential learning mechanism to operate.
• Survey-based measures: The survey includes measures of Eco-Score familiarity and prior use, sustainability attitudes, and label awareness. These are used as covariates in heterogeneity analyses to examine whether treatment effects differ across consumer segments with varying levels of prior familiarity with the Eco-Score or differing sustainability orientations.

This study implements a randomized controlled trial (RCT) conducted in collaboration with one of Switzerland's largest grocery retailers. Participants are randomly drawn from the retailer's loyalty program and assigned to one of four experimental conditions in a 2×2 factorial design:

Control group: No intervention.
Information treatment: Participants receive information about the Eco-Score sustainability label as a decision aid, including an illustrative comparison between a conventional meat product and a plant-based alternative.
Voucher treatment: Participants receive a one-time voucher redeemable at any store of the retail collaboration partner, enabling them to obtain two plant-based meat substitute products free of charge.
Combined treatment: Participants receive both the information treatment and the voucher treatment.

The target sample size is approximately 15,000 participants, distributed evenly across the four conditions. The primary outcomes of interest are real-world food purchasing behavior, measured using individual-level loyalty program purchasing data, with a focus on plant-based meat substitute purchases and conventional meat purchases before and after the experimental intervention.

In addition, all participants complete an online survey that includes a discrete choice experiment examining how product attributes and naming conventions influence stated preferences for plant-based products.

Not available

Study participants are drawn from the population of customers enrolled in the loyalty program of our retail collaboration partner. The retailer holds the largest market share among food retailers in Switzerland, accounting for approximately 43% of the market (Statista, 2020). The target sample size for the present study is 15,000 customers. Randomization is conducted at the individual customer level. Participants will be randomly assigned to the experimental treatment conditions with the aim of achieving balanced group sizes. Specifically, randomization will be conducted such that participants are approximately evenly distributed across the four RCT treatment conditions (Control, Information only, Voucher only, Voucher + Information). In addition, participants will be independently and approximately evenly assigned to one of the four linguistic framing conditions in the discrete choice experiment (national-language without meat references, hybrid without meat references, national-language with meat references, hybrid with meat references).

The unit of randomization is the individual customer.

No

The sampling design is not clustered

The target sample size for the present study is 15,000 customers from the loyalty program of our retail collaboration partner. The final achieved sample size is expected to depend on survey response rates. Recruitment will remain open for three weeks after survey launch, after which data collection will be closed. The final sample will therefore include all eligible customers who complete the survey within this predefined recruitment period. The study uses individual-level purchasing data collected through the retailer's loyalty program and sales system, which allows us to observe food purchases over time and look into short-term, mid-term and long-term effects of the interventions. The total observation period will cover approximately one year prior to the experimental intervention and one year after the intervention. Because purchasing data are recorded continuously, each participating customer may contribute multiple purchase observations during the observation period. Consequently, the number of product-level purchase observations is expected to substantially exceed the number of participating individuals.

RCT: Information and Voucher Treatments
Participants will be randomly assigned to one of four experimental groups with the aim of achieving balanced group sizes.
• Control group: approximately 3,750 customers
• Information treatment: approximately 3,750 customers
• Voucher treatment: approximately 3,750 customers
• Voucher + Information treatment: approximately 3,750 customers
Actual sample sizes may vary slightly due to randomization and participation patterns.


Choice Experiment: Product Attributes and Naming
All participants who complete the survey will take part in the choice experiment. Respondents will be randomly assigned to one of four naming-framing conditions with the aim of achieving balanced group sizes across these conditions.