Effect of alcohol label designs with different pictorial representations of alcohol content and health warnings on knowledge and understanding of low-risk drinking guidelines: a randomized controlled trial

Abstract

Background and aims: The UK low-risk drinking guidelines (LRDG) recommend not regularly drinking more than 14 units of alcohol per week. We tested the effect of different pictorial representations of alcohol content, some with a health warning, on knowledge of the LRDG and understanding of how many drinks it equates to.

Design: Parallel randomized controlled trial.

Setting: On-line, 25 January-1 February 2019.

Participants: Participants (n = 7516) were English, aged over 18 years and drink alcohol.

Interventions: The control group saw existing industry-standard labels; six intervention groups saw designs based on: food labels (serving or serving and container), pictographs (servings or containers), pie charts (servings) or risk gradients. A total of 500 participants (~70 per condition) saw a health warning under the design.

Measurements: Primary outcomes: (i) knowledge: proportion who answered that the LRDG is 14 units; and (ii) understanding: how many servings/containers of beverages one can drink before reaching 14 units (10 questions, average distance from correct answer).

Findings: In the control group, 21.5% knew the LRDG; proportions were higher in intervention groups (all P < 0.001). The three best-performing designs had the LRDG in a separate statement, beneath the pictograph container: 51.1% [adjusted odds ratio (aOR) = 3.74, 95% confidence interval (CI) = 3.08-4.54], pictograph serving 48.8% (aOR = 4.11, 95% CI = 3.39-4.99) and pie-chart serving, 47.5% (aOR = 3.57, 95% CI = 2.93-4.34). Participants underestimated how many servings they could drink: control mean = -4.64, standard deviation (SD) = 3.43; intervention groups were more accurate (all P < 0.001), best performing was pictograph serving (mean = -0.93, SD = 3.43). Participants overestimated how many containers they could drink: control mean = 0.09, SD = 1.02; intervention groups overestimated even more (all P < 0.007), worst-performing was food label serving (mean = 1.10, SD = 1.27). Participants judged the alcohol content of beers more accurately than wine or spirits. The inclusion of a health warning had no statistically significant effect on any measure.

Conclusions: Labels with enhanced pictorial representations of alcohol content improved knowledge and understanding of the UK's low-risk drinking guidelines compared with industry-standard labels; health warnings did not improve knowledge or understanding of low-risk drinking guidelines. Designs that improved knowledge most had the low-risk drinking guidelines in a separate statement located beneath the graphics.

Keywords: Alcohol; alcohol unit; cancer; consumer knowledge; graphic labels; health warning label; low-risk drinking guidelines; pictorial labels; product labelling; standard drink.