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ObjectiveHealth warning and calorie labels on alcohol have the potential to reduce consumption at population level but remain unevaluated using robust designs with behavioural outcomes. The aim of the current study is to estimate the impact on selection and actual purchasing of (a) health warning labels (text-only and image-and-text) on alcoholic drinks and (b) calorie labels on alcoholic and non-alcoholic drinks.DesignParallel-groups randomised controlled trial.SettingParticipants selected drinks in a simulated online supermarket, before purchasing them in an actual online supermarket.ParticipantsAdults in England and Wales who regularly consumed and purchased beer or wine online (n= 644).InterventionsParticipants were randomised to one of six groups in a between-subjects 3 (Health warning labels (HWLs): i. image-and-text HWL, ii. text-only HWL, iii. no HWL) x 2 (Calorie labels: present vs absent) factorial design.Main outcome measuresThe number of alcohol units selected (with intention to purchase); secondary outcomes included alcohol units purchased and calories selected and purchased.Results608 participants completed the study and were included in the primary analysis. There was no evidence of an overall difference for either (a) HWLs, or (b) calorie labels on the number of alcohol units selected [HWLs: F(2,599) = 0.406, p = .666; calorie labels: F(1,599) = 0.002, p = .961]. There was also no evidence of an overall difference on any secondary outcomes, including the number of alcohol units purchased [HWLs: F(2,462) = 1.85, p = .159; calorie labels: F(1,462) = 0.193, p = .661].In pre-specified subgroup analyses comparing the ‘calorie label only’ group (n = 101) to the ‘no label’ group (n = 104) there was no evidence that calorie labels reduced the number of calories selected [unadjusted means: 1913 calories vs 2203 calories, p = .643]. Amongst the 75% of participants who went on to purchase drinks, those in the ‘calorie label only’ group (n = 74) purchased fewer calories than those in the ‘no label’ group (n = 79) [unadjusted means: 1532 calories vs 2090, p = .028].ConclusionThere was no evidence that health warning labels reduced the number of alcohol units selected or purchased in an online purchasing setting. There was some evidence suggesting that calorie labels on alcoholic and non-alcoholic drinks may reduce calories purchased. Further evaluation is warranted in suitably powered studies in real world settings.Trial registrationPre-registered protocol (https://osf.io/ch2sm/) and prospective ISCRTN registration: https://www.isrctn.com/ISRCTN10313219FundingThis study was funded by Wellcome [Grant number 206853/Z/17/Z]. |
