Effects of social norms vs health claims on purchasing behaviour: Reducing high-salt foods and promoting fruit and vegetables.
Carla Almeida, Catarina Carvalho, Eduarda Lopes et al.
✦ AI-curated · Sources linked
In 30 seconds
This randomized crossover study examined whether health-claim or social-norm messages influenced food purchases in 12 Portuguese supermarkets. Messages were delivered through audio and posters during six weeks, with periods focused on salt reduction and on promoting fruit and vegetables. Health-claim messaging was associated with greater purchases of fruit, vegetables, legumes, and soup (high vs low sales tertile: OR = 2.9, 95% CI: 1.09-7.74). Social-norm messaging was associated with higher sales of unsalted or low-salt products (>P50 vs <P50: OR = 3.8, 95% CI: 1.61-8.90). Neither message type significantly affected high-salt product sales.
Key findings
- Health claims were associated with higher purchases of fruit, vegetables, legumes, and soup (high vs low tertile: OR = 2.9, 95% CI: 1.09-7.74).
- Social norms were associated with higher sales of unsalted or low-salt products (>P50 vs <P50: OR = 3.8, 95% CI: 1.61-8.90).
- No significant effects were observed for high-salt product sales.
Why it matters
The findings suggest that message framing may relate differently to purchasing across food categories: health claims aligned with purchases of fruit, vegetables, legumes, and soup, while social norms aligned with lower-salt choices. This distinction may inform the design and evaluation of supermarket-based public health communications, although the reported associations do not establish that either message caused the purchasing changes.
What to keep in mind
The study was conducted in 12 supermarkets in Portugal, and the abstract reports sales associations rather than evidence that messages caused changes in individual dietary intake.