Do alcohol product labels stating lower strength verbal description, percentage alcohol-by-volume, or their combination affect wine consumption? A bar laboratory adaptive randomised controlled trial.

BACKGROUND AND AIMS

A previous research study concluded that wine and beer labelled as lower in strength increase consumption compared with the same drinks labelled as regular strength. The label included both a verbal and numerical descriptor of strength. The present study aimed to estimate the effect of each of these label components.

DESIGN

Adaptive, parallel group randomised controlled trial, comprising an internal pilot sample (n  = 90) and a confirmatory sample (n  = 57).

SETTING

University bar laboratory in London, United Kingdom (UK).

PARTICIPANTS

A total of 147 weekly wine drinkers were sampled from a nationally representative English panel.

INTERVENTION

Participants were randomised to one of three groups to taste test wine in a bar-laboratory, varying only in the label displayed: (i) verbal descriptor only (Super Low); (ii) numerical descriptor only (4% alcohol by volume (ABV)); and (iii) verbal descriptor and numerical descriptor combined (Super Low 4%ABV) (each group n = 49).

MEASUREMENTS

The primary outcome was total volume (ml) of wine consumed.

FINDINGS

Participants randomised to the numerical descriptor label group (4%ABV: M = 155.12 ml, B = 20.30; 95% CI = 3.92, 36.69; P value = 0.016) and combined verbal and numerical descriptor label group (Super Low 4%ABV: M = 154.59 ml, B = 20.68; 95% CI = 4.32, 37.04; P value = 0.014) drank significantly greater amounts than those randomised to the verbal descriptor label group (Super Low: M = 125.65 ml).

CONCLUSIONS

This bar laboratory study estimated that a greater quantity of 'lower' strength wine was consumed when the label included a numerical strength descriptor compared with a verbal only strength descriptor.