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Might Smaller Wine Glasses Reduce Drinking?

A new study has suggested that drinking wine from smaller glasses may help to reduce overall intake.

Published in the journal Addiction, a team from the Behaviour and Health Research Unit at the University of Cambridge conducted a randomised controlled trial of glass and bottle sizes in 260 UK households recruited from the general UK population through a research agency. Subjects were all adults, most were white and of higher socio-economic position, and each household drank at least two 75-cl bottles of wine per week.

Households were asked to buy a pre-set amount of wine in either 75-cl or 37.5-cl bottles, each for a 14-day intervention period, in random order with a cross-over separated by a 'washout' period. In parallel, they were asked to drink the study wine from one of two wine glass sizes, 290-ml or 350-ml capacity, both of the same design and again randomised as to the order.

Volume of wine consumed at the end of each 14-day intervention period was measured using photographs of purchased bottles, weighed on provided scales. Results showed that households consumed around 253 ml (6.5%) less wine per fortnight when drinking from the smaller glasses than the larger ones. Although confidence intervals were wide, and the result only of borderline significance (P=0.065), the team said that the impact of glass size both alone and in combination with bottle size was "in the hypothesised direction".

In addition, results showed that drinking from smaller bottles reduced the amount of wine consumed by around 146 ml (3.6%) per fortnight on average, though there was greater uncertainty around this effect.

Larger Glasses Increase Wine Sold in Bars

The results accorded with the team's previous research showing that using larger than standard size glasses while keeping portion size constant increased the volume of wine sold in a local restaurant by 9.4% overall - 8.2% in the restaurant itself and 14.4% in the bar area. However in that study the results were inconclusive as to whether smaller glasses had the opposite effect.

The results also parallel various studies suggesting that people tend to eat more when using larger tableware – and conversely smaller plates that make smaller portions appear bigger may reduce consumption. Although studies have not been consistent, a Cochrane Review of 86 independent comparisons from 58 studies involving 6603 participants found moderate quality evidence that people consistently consume more food and drink when offered larger‐sized portions, packages or tableware than when offered smaller‐sized versions.

The effect was seen in both adults and children and its size suggested that, if sustained reductions in exposure to larger sizes could be achieved across the whole diet, it could reduce average daily food calorie consumption by between 144 and 228 kcal (8.5% to 13.5% from a baseline of 1689 kcal) – something that would clearly be helpful in the context of the current obesity epidemic.

Association with Overweight and Obesity

The authors of the new study did not specifically assess the effect of altered wine consumption on calorie intake. However, asked whether their research might also have implications for weight control, lead author Dr Eleni Mantzari told Medscape UK: "Alcohol is a significant source of calories and we know from previous research that there is an association between calorie intake from alcohol and overweight and obesity.

"So, any reduction in alcohol intake will inevitably lead to a reduction in calories consumed from alcohol. We didn't look at calories in our study, but we found that that approximately 253-ml less wine was consumed per household per fortnight with smaller wine glasses. If we assume that mean number of calories in the wines purchased in the study was 79.7 per 100 ml, this equates to approximately 201.6 fewer calories consumed per fortnight when using the smaller glasses.”

The study authors commented that wine is the most commonly drunk alcoholic beverage in Europe, and most of it is consumed at home. "The size of wine glasses in general has increased dramatically over the last three decades," they said. If their results on the effects of wine glass size on consumption were proven reliable, with effects sustained over time, "it could be that reducing the size of wine glasses used in homes could contribute to policies for reducing drinking".

Incorporating Glass Size Into Alcohol Policy

Pricing glasses according to capacity, for example, could increase the demand for smaller glasses generally, they suggested. Regulating glass sizes in bars, restaurants, and other licensed premises could "help shift social norms for what constitutes an acceptable glass size". Also: "Were an effect of smaller bottles—in particular, those of 37.5-cl capacity—to be more certain, possible policies for shifting purchasing and consumption to smaller bottle sizes might include increasing their availability and affordability."

Asked to comment on the study, Charles Spence, professor of experimental psychology at the University of Oxford and author of Gastrophysics: The New Science of Eating, told Medscape UK: "The effects look very weak, and small." However, he agreed: "Generally-speaking, it would seem like the fixation on a 750-ml [bottle] as standard for wine is not ideal, especially given the growing number of people living/eating alone." Nonetheless, he didn't see half-sized bottles as likely to catch on. "The 375-ml wine bottle, however, even if it had had a dramatic effect on consumption, would be unlikely to get wineries to completely change their bottling lines."

A further potential disappointment for the study team is that, whilst they clearly hoped that their research would support various nudges towards reducing alcohol consumption, the bar/restaurant where they undertook their previous experiment reportedly has now permanently switched to serving wine in larger glasses.

Some authors received funding from the Wellcome Trust.

Lead Image Credit: Image Source/Getty Images