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Drink it straight: People take longer to consume sugary soft drinks served in straight-sided glasses

07 September 2018

People drink soft drinks more slowly from glasses which have straight sides, when compared to those that slope outwards.

That is the central conclusion of PhD research by Tess Langfield from the Behaviour and Health Research Unit at the University of Cambridge, which is being presented at the British Psychological Society’s Division of Health Psychology annual conference in Gateshead today and published online.

Tess Langfield said:

“Previous research has shown that the shape of a glass can affect the rate at which someone consumes an alcoholic beverage, but with overconsumption of sugary soft drinks being a current public health issue, we were keen to investigate whether this effect was also seen with a soft drink.”

A total of 162 participants were recruited from the student and staff population at the University of Cambridge, and given 330ml of carbonated apple juice in a glass that either sloped inwards, sloped outwards, or had a straight side. The researchers then measured how long it took them to drink the full glass.

The participants were unaware of the real purpose of the study – they were given a word search to complete on a computer and told that the aim of the research was to investigate the impact of glucose on cognitive performance, providing a cover story for the study aim.

The researchers found that those participants who had been given apple juice in an outward-sloped glass consumed it about 20 % faster than those drinking from a straight-sided glass, finishing their drink in an average time of 4 minutes 46 seconds, just over one minute quicker than those drinking from straight-sided glass.

Research on glasses with inward-sloping sides was inconclusive, but there was some data to suggest that drinking is quicker from these than from glasses with straight sides.

The results also suggested trends that those drinking from sloped glasses, whichever direction the slope was going in, took larger sips of their drink than the participants who had a glass with straight sides.

Langfield added:

“Policy makers have considered a number of interventions to reduce people’s consumption of soft drinks that have a particularly high sugar content, including a sugar tax. Our research highlights an additional promising approach, namely the use of straight-sided glasses.

These findings are in line with growing evidence showing that making small changes to the environment, such as to the shape of a glass in which drinks are being served, can influence people’s behaviour in subtle ways and often without their awareness.”

You can read the full paper by clicking here.

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