Impact of wine bottle and glass sizes on wine consumption at home: a within‐ and between‐ households randomized controlled trial

BACKGROUND AND AIMS: Reducing alcohol consumption across populations would decrease the risk of a range of diseases, including many cancers, cardiovascular disease and Type 2 diabetes. The aim of the current study was to estimate the impact of using smaller bottles (37.5‐ versus 75‐cl) and glasses (290 versus 370 ml) on consuming wine at home. DESIGN: Randomized controlled trial of households with cross‐over randomization to bottle size and parallel randomization to glass size. SETTING: UK households. PARTICIPANTS: A total of 260 households consuming at least two 75‐cl bottles of wine each week, recruited from the general population through a research agency. The majority consisted of adults who were white and of higher socio‐economic position. INTERVENTION: Households were randomized to the order in which they purchased wine in 37.5‐ or 75‐cl bottles, to consume during two 14‐day intervention periods, and further randomized to receive smaller (290 ml) or larger (350 ml) glasses to use during both intervention periods. MEASUREMENTS: Volume (ml) of study wine consumed at the end of each 14‐day intervention period, measured using photographs of purchased bottles, weighed on study scales. FINDINGS: Of the randomized households, 217 of 260 (83%) completed the study as per protocol and were included in the primary analysis. There was weak evidence that smaller bottles reduced consumption: after accounting for pre‐specified covariates, households consumed on average 145.7 ml (3.6%) less wine when drinking from smaller bottles than from larger bottles [95% confidence intervals (CI) = –335.5 to 43. ml; −8.3 to 1.1%; P = 0.137; Bayes factor (BF) = 2.00]. The evidence for the effect of smaller glasses was stronger: households consumed on average 253.3 ml (6.5%) less wine when drinking from smaller glasses than from larger glasses (95% CI = –517 to 10 ml; −13.2 to 0.3%; P = 0.065; BF = 2.96). CONCLUSIONS: Using smaller glasses to drink wine at home may reduce consumption. Greater uncertainty remains around the possible effect of drinking from smaller bottles.