In 2012, New York Mayor Michael Bloomberg proposed that to reduce obesity, the city would prohibit the sale of any sugar-containing beverage in containers greater than 16 ounces. A new study looks at a similar approach to improving public health in the U.K., by reducing the size of a glass of wine. It found that size matters – sort of.
The UK has a long history with alcohol, as the phrase gin mill might attest. And while I would most commonly associate the UK with beer and picking up a pint, as it turns out, white wine is “the favorite tipple.” Researchers take it as a given, as does the WHO,
“that no level of alcohol consumption is currently considered safe for health with even light and moderate consumption contributing to the development of many cancers…”
Other research suggests that mild to moderate alcohol consumption is healthful. They point out that increasing the price of alcoholic drinks and market regulations have reduced consumption, as we have seen with sugary beverages; however, “more interventions are needed to reduce consumption further.” Noting that when presented with smaller portions or packaging, “people consume less,” could this “portion size effect” be applied to alcohol?
To find an answer, they found 21 pubs in London willing to remove their largest-size glass of wine from the menu and had electronic point-of-sales systems that could capture the relevant sales data.  Sales data was captured for four weeks prior to the study, for the following four weeks when the largest glass of wine was removed from the menu, and for an additional four weeks once the larger size returned.
Pilot studies in student bars suggested that 80+ pubs were needed to power statistical significance. With the recruitment of 21, the researchers determined that the study “was therefore considered opportunistic, providing preliminary evidence to inform future research.”
As depicted to the left, removing the largest glass of wine (250 ml or 175 ml, depending upon the pub) reduced consumption by 7%. The economics-minded amongst us would now be concerned about a substitution effect – was the larger glass of wine replaced with smaller glasses or other forms of alcohol? There was no change in the sales of beer or cider. Data on the sale of hard liquor was not available.
There was an increase in the sales of smaller glasses of wine, but not in larger portion sizes, e.g., carafes or bottles. None of the pubs experienced a loss of revenue. These facts, taken together, suggest that the decrease in wine consumed may have been due to a slight price increase - after all, a larger glass of wine is usually slightly less expensive than the equivalent amount sold as two glasses.  The researchers alternatively suggest that:
“People have the tendency to consume a specific number of “units” (e.g., number of glasses or bottles, number of cookies or slices of cake), regardless of portion or package size … This helps explain why smaller serving sizes reduce alcohol consumption: people tend to order a pre-set number of glasses, and with less alcohol in each glass they drink less overall.”
Given that the study was “opportunistic” and underpowered to draw any statistically significant conclusions, the data dots may be connected in any way you wish. This “wiggle room” allowed the researchers to conclude that a reduction in the maximum size of a glass of wine was a
“promising intervention for decreasing alcohol consumption across populations merits consideration as part of alcohol licensing regulations.”
One last caveat from history
The researchers, in discussing strengths and limitations, noted that
“Interventions that reduce serving or package sizes are generally less supported by the public than information-based interventions, such as health warning labels.”
If history is a guide, we might consider Mayor Bloomberg’s proposed maximum size of a sugary beverage. The City’s Board of Health regulation was overturned in court because it “exceeded the scope of its regulatory authority,” having not been previously approved by the City Council. A New York Times poll conducted just before the actions by the Board of Health found that 60% were not in favor of such a ban. Despite the adverse health effects of alcohol, which are more clearly linked to excessive use, the American public historically has not been in favor of reducing their supply of alcohol. Only one amendment to our constitution, the 18th, establishing Prohibition, has been repealed. Only one.
 Finding those 21 pubs was a hard sell. They asked 1,778 licensed “premises” for a recruitment rate of 1%. The researchers also sought pubs that would discontinue their largest size of beer – they had no takers. The pubs that did participate were located in “more deprived areas.” (You have to love the British phrasing) Deprivation, in this instance, would be our “disadvantaged communities.”
 The researchers did note that a smaller glass of wine had a more significant profit margin, but only when discussing changes in revenue, not in consideration of decreased consumption.
Source: Impact on wine sales of removing the largest serving size by the glass: An A-B-A reversal trial in 21 pubs, bars, and restaurants in England PLOS Medicine DOI: 10.1371/journal.pmed.1004313