Most alcohol research tends to assume that alcoholic drinks contain the same amount of pure alcohol: 0.6 ounces or 18 milliliters. Why is this important? Because researchers need accuracy to do their job well, and consumers need to know what they're drinking, especially if they are then going to drive.
A new study has found that the average size of wine, mixed drinks and beer served in Northern California bars, restaurants and other drinking establishments tends to be larger than the assumed standard, and the alcohol content can vary widely.
"There are a number of factors that influence the alcohol content of drinks," explained William C. Kerr, senior scientist with the Alcohol Research Group at the Public Health Institute and first author of the study. "These include glass size; percent alcohol by volume (%ABV) of the beer, wine or spirit, for example a 15-percent wine versus an 11-percent wine, or a six-percent beer compared to a 4.2-percent light beer; accidental pour variability; and probably most important, the intentions of management and the bartender."
Given that alcohol-content information is rarely available in American bars and restaurants, he added, this kind of study gives consumers a better basis for estimating their alcohol intake.
Kerr and his colleagues visited 80 establishments (41.8% bars, 39.8% restaurants) in 21 towns in 10 different counties during March, April and May of 2007. A total of 480 drinks -- comprised of beer, wine and spirits -- were purchased and measured, and 337 drink samples were analyzed within 36 hours of the visit. Either the brand name or analysis of the drink itself was used to determine its alcohol concentration.
Kerr said there were three key findings. "First, the typical wine, beer or mixed spirits drink in bars is larger than a standard drink, often by 50 percent or more," he said. "Second, within these beverage types, the alcohol content can vary widely. Third, particular beverage types and drink types vary in average alcohol content and variability."
More specifically, the average glass of wine was 43 percent larger than a standard drink, with no difference found between red and white. The average draft beer was 22 percent larger than the standard. While bottled beer (not measured in this study) and shots of spirits were equal to one standard drink, drinks mixed with spirits were 42 percent larger than the standard.
Kerr explained some of the variance, using wine as an example. "The types of wines served in these establishments tended to be higher in %ABV, averaging 14 percent instead of the 12-percent ABV quoted in the standard drink definition," said Kerr. "The average pour was also over six ounces. We think the typical high price of a glass of wine relative to the wholesale bottle price is an important factor. Often the glass price was equal to the wholesale purchase cost of the whole bottle. With a high price, the larger pour was needed to make the customer more comfortable with the price. Conversely, with less expensive wine, the cost of the wine was low so that again a large pour will give the customer the perception of value and add little additional cost."
It is the combination of higher alcohol-content drinks and the lack of awareness and disclosure that make this "abundance" problematic, said Kerr.
"While some consumers are clearly happy when they get more alcohol, most on-premise drinkers are not trying to drink as much as possible on every occasion," he said. "This is particularly true for those who plan to drive or engage in other activities, and for those who are sensitive to alcohol's effects but still like to drink in moderation. It is very difficult for individuals to judge the number of ounces in a wine glass or the %ABV of their wine beer or spirits drinks. If both volume and %ABV are each about 25 percent higher than expected, for example, and the consumer has three or four of these drinks, then their intake will be much higher than planned -- about two additional standard drinks for four of these drinks -- and this could have significant and possibly damaging consequences."
Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the ACER paper, "Alcohol Content Variation of Bar and Restaurant Drinks in Northern California," were: Deidre Patterson, Mary Albert Koenen, and Thomas K. Greenfield of the Alcohol Research Group. The study was funded by the National Institute on Alcohol Abuse and Alcoholism.
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