Impact on alcohol selection and online purchasing of changing the proportion of available non-alcoholic versus alcoholic drinks: A randomised controlled trial
Authors: Clarke Natasha , Blackwell Anna KM , Ferrar Jennifer , De-Loyde Katie , Pilling Mark A , Munafò Marcus R , Marteau Theresa M , Hollands Gareth J 
Published: March 2022

AbstractBackgroundIncreasing the availability of non-alcoholic options is a promising population-level intervention to reduce alcohol consumption, currently unassessed in naturalistic settings. This study in an online retail context aimed to estimate the impact of increasing the proportion of non-alcoholic (relative to alcoholic) drinks, on selection and purchasing of alcohol.Methods and ResultsAdults (n=737) residing in England and Wales who regularly purchased alcohol online were recruited between March-July 2021. Participants were randomly assigned to one of three groups: ‘25% non-alcoholic/75% alcoholic’; ‘50% non-alcoholic/50% alcoholic’; ‘75% non-alcoholic/25% alcoholic’, then selected drinks in a simulated online supermarket, before purchasing them in an actual online supermarket. The primary outcome was the number of alcohol units selected (with intention to purchase); secondary outcomes included actual purchasing. 607 participants (60% female, mean age = 38 years [range: 18-76]) completed the study and were included in the primary analysis. In the first part of a hurdle model, a greater proportion of participants in the ‘75% non-alcoholic’ group did not select any alcohol (13.1%) compared to the ‘25% non-alcoholic’ group (3.4%; 95% confidence interval [CI] - 2.09, -0.63; p < 0.001). There was no evidence of a difference between the ‘75% non-alcoholic’ and the ‘50% non-alcoholic’ (7.2%) groups (95% CI 0.10, 1.34; p = 0.022) or between the ‘50% non-alcoholic’ and the ‘25% non-alcoholic’ groups (95% CI -1.44, 0.17; p = 0.121). In the second part of a hurdle model in participants (559/607) selecting any drinks containing alcohol, the ‘75% non-alcoholic’ group selected fewer alcohol units compared to the ‘50% non-alcoholic’ (95% CI -0.44, -0.14; p < 0.001) and ‘25% non-alcoholic’ (95% CI - 0.54, -0.24; p < 0.001) groups, with no evidence of a difference between the ‘50% non-alcoholic’ and ‘25% non-alcoholic’ groups (95% CI -0.24, 0.05; p = 0.178). Overall, across all participants, 17.46 units (95% CI 15.24, 19.68) were selected in the ‘75% non-alcoholic’ group; 25.51 units (95% CI 22.60, 28.43) in the ‘50% non-alcoholic’ group; and 29.40 units (95% CI 26.39, 32.42) in the ‘25% non-alcoholic’ group. This corresponds to 8.1 fewer units (a 32% reduction) in the ‘75% non-alcoholic’ compared to the ‘50% non-alcoholic’ group, and 11.9 fewer alcohol units (41% reduction) compared to the ‘25% non-alcoholic’ group; 3.9 fewer units (13% reduction) were selected in the ‘50% non-alcoholic’ group than in the ‘25% non-alcoholic’ group.For all other outcomes, alcohol selection and purchasing were consistently lowest in the ‘75% non-alcoholic’ group.Study limitations include the setting not being entirely naturalistic due to using a simulated online supermarket as well as an actual online supermarket, and that there was substantial dropout between selection and purchasing.ConclusionsThis study provides evidence that substantially increasing the proportion of non-alcoholic drinks – from 25% to 50% or 75% - meaningfully reduces alcohol selection and purchasing. Further studies are warranted to assess whether these effects are realised in a range of real-world settings.Trial registrationISRCTN:11004483; OSF:https://osf.io/qfupwAuthor summaryWhy was this study done?Excessive alcohol consumption contributes to the global burden of non-communicable diseases, including cancer, heart disease and stroke. Interventions that change physical and economic environments have the potential to reduce alcohol consumption.Interventions targeting physical environments include availability interventions that involve changing the proportion of healthier options that are available, relative to less healthy options.A previous online study found that increasing the availability of non-alcoholic compared to alcoholic drinks reduced the hypothetical selection of alcoholic drinks, but there is an absence of evidence from naturalistic settings.What did the researchers do and find?This study evaluated the impact of increasing the proportion of non-alcoholic (relative to alcoholic) drinks, on selection and actual purchasing of alcohol.In a randomised controlled trial, 737 participants were randomly assigned to one of three groups with varying proportions of alcoholic versus non-alcoholic drinks ‘25% non-alcoholic/75% alcoholic’; ‘50% non-alcoholic/50% alcoholic’; ‘75% non-alcoholic/25% alcoholic’).Participants selected drinks from 64 options in a simulated online supermarket which was designed to look and function similarly to an online supermarket. Participants were then required to immediately purchase the same drinks in an actual online supermarket.It was found that increasing the proportion of non-alcoholic drinks – from 25% to 50% or 75% – reduced the amount of alcohol selected and bought, in this online supermarket setting.What do these findings mean?This study provides evidence that increasing the proportion of non-alcoholic drinks could reduce alcohol selection and purchasing, highlighting the potential for availability interventions to reduce alcohol sales at population level.Further studies are warranted to assess whether these effects are realised in a range of real-world settings