The size of our wine glass influences how much we drink

Wine glasses have doubled in size since 1990. A mega-analysis with data by the University of Cambridge has found that bigger wine glasses leads us to drink more alcohol in restaurants. The findings support calls to limit the size of wine glasses to reduce alcohol-related harm.

Five bars and restaurants in England participated in studies between 2015 and 2018, using wine glasses of five sizes: 250, 300, 370, 450 and 510 ml, with the largest size only used in bars. The team used 300ml glasses as the reference level to compare differences in consumption.

Wine sales in bars and restaurants are served in fixed sizes when sold by the glass or sold by the bottle or carafe. Most wine in restaurants is served to pour from a bottle or a carafe and allows people to pour more than a standard serving size.

Wine sales in restaurants increased with 7,3 % when the glass size was switched from 300 ml to 370 ml and decreased with 9,6 % when it was switched from the former to 250 ml. There was no significant effect in sales when the standard 300 ml glass was switched to the largest size 450 ml. The study found no significant effect on the daily sale of wine in bars.

The largest glass may have been perceived as noticeably larger for the diners causing conscious counter behaviour, such as drinking more slowly or pouring with greater caution. The authors see this as a reflection of the “unit bias”. Glasses between 250 ml to 370 are perceived as a normal glass wine. However, larger glass sizes as 450 and 510 ml are deemed to holding more than a typical glass of wine and thereby diners may adapt their behaviour.

'We all like to think we're immune to subtle influences on our behaviour – like the size of a wine glass – but research like this clearly shows we're not,' said Professor Ashley Adamson, Director of the NIHR School of Public Health Research.

To reduce our alcohol consumption, we need to understand the factors that influence how much we consume. The findings from this study show that small changes have the potential to contribute to reducing alcohol consumption and help consumers be healthier without having to think about it.

Read “The effect of wine glass size on volume of wine sold: a mega‐analysis of studies in bars and restaurants” by Mark Pilling, Natasha Clarke, Rachel Pechey and Gareth J. Hollands Theresa M. Marteau: https://onlinelibrary.wiley.com/doi/full/10.1111/add.14998