- A standard U.S. drink is usually defined as the equivalent of 0.6 ounces (17.74 ml.) of pure alcohol.
- This generally corresponds to 12 ounces (355 ml.) of beer, five ounces (148 ml.) of wine, and 1.5 ounces (44.4 ml.) of spirits.
- A study of home-poured alcoholic beverages has found considerable variation in drink size, particularly for spirits and wine.
In the U.S., a standard drink is usually defined as the equivalent of 0.6 ounces (17.74 ml.) of pure alcohol. The corresponding standard sizes are, generally, 12 ounces (355 ml.) of beer, five ounces (148 ml.) of wine, and 1.5 ounces (44.4 ml.) of spirits. A recent study of American drinkers that measures their usual alcohol consumption in the home environment has found considerable variation in drink size, particularly for spirits and wine. Results are published in the November issue of Alcoholism: Clinical & Experimental Research.
"Individual drinkers should be concerned with varying drink alcohol content because the consumption of non-standard drinks affects their ability to keep track of how much alcohol they have consumed and therefore their ability to conform to safe drinking guidelines and driving laws," said William C. Kerr, a scientist with the Alcohol Research Group at the Public Health Institute and corresponding author for the study.
"Without valid and reliable measures of how much alcohol is being consumed by a population, the ability to assess risk is compromised," added Lorraine Midanik, a professor in the school of social welfare at the University of California at Berkeley, and an affiliate senior scientist with the Alcohol Research Group. "Population estimates of alcohol use derived from self-reports are used to determine risk for various adverse health and social outcomes. Population estimates of alcohol use also help us to understand trends in the U.S. population. That is, 'are people drinking more, less or about the same alcohol over time?,' 'how are these trends related to morbidity and mortality?,' and 'what does this mean for policies that may affect alcohol consumption?'"
Kerr added that many countries have official standard drink sizes that differ from the U.S. standard. "Most of these, such as the United Kingdom standard of eight to 10 grams of alcohol are smaller than the U.S. standard," he said. "However, in no case are these standards based on studies of what drinkers actually consume. In fact, this is the first study to utilize beaker-measured drink sizes and brand-level percentage alcohol by volume information in a national sample in the U.S."
Kerr and his colleagues re-contacted 310 drinkers from the 2000 National Alcohol Survey to request their participation in a telephone survey that included specific questions about alcohol beverages consumed at home. Study participants were given a beaker to measure each alcoholic beverage that they prepared at home. Information was also gathered about the brand or type of each product in order to determine as accurately as possible the percentage of alcohol.
Results indicate that the 0.6 ounce measure of pure alcohol in a standard drink is a reasonable single standard. "The mean drink alcohol content was 0.67 ounces, which is 11.7 percent larger than the 0.6 ounce standard drink," said Kerr. "A single-drink standard is helpful for simplifying messages about safe drinking limits and driving-under-the-influence limits as compared to having different standards for each beverage."
However, there exists considerable variation in drink size, and beverages with smaller standard serving sizes - such as spirits and wine - show greater discrepancies in their alcohol content. "Wine and spirits drinks are on average larger and more variable than beer drinks," said Kerr, "with spirits drinks averaging nearly 50 percent more alcohol than the U.S. standard drink."
"Clearly there is much variation in what constitutes 'a drink' in the U.S. population," said Midanik. "The size of a drink may vary dramatically, as well as the alcohol content of the alcohol consumed. These findings should stress to researchers that obtaining information on beverage use must include specific alcohol beverage type and some measure of the size of drinks."
Kerr added that this study's closer look at individual drinks also resulted in larger estimates of monthly alcohol consumption than estimates based on standard drinks. "This discrepancy is larger for women," he said, "because a larger proportion of their drinks are wine and spirits. Also, the difference in monthly alcohol volume is larger than the difference in mean drink size because heavier drinkers appear to choose high-alcohol-content drinks on average."
"The real-world implications of these findings are that we are continuously underestimating alcohol use in the U.S. and within specific populations with our traditional survey methodology," said Midanik. "This is highly problematic given that policy, treatment and prevention efforts are based on national surveys which provide basic epidemiologic data on alcohol use and alcohol-related problems in the population. These findings also have major implications for researchers, and will hopefully provide additional refinements to our survey questions in order to provide better estimates of alcohol consumption."
"In summary," said Kerr, "our findings suggest that many readers and their friends & family are pouring themselves larger-than-standard drinks. Given that safe-drink messages are based on a specific amount of alcohol in a drink, 0.6 ounces, they might want to become more aware of the percentage of alcohol in the brands of beer, wine and spirits they choose, perhaps adjusting their drink size accordingly. At minimum, they should be aware of larger-than-standard drinks."
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, "A Drink Is a Drink? Variation in the Amount of Alcohol Contained in Beer, Wine and Spirits Drinks in a U.S. Methodological Sample," were: Thomas K. Greenfield of the Alcohol Research Group at the Public Health Institute, and the University of California, San Francisco; and Jennifer Tujague and Stephan E. Brown of the Alcohol Research Group at the Public Health Institute. The study was funded by the National Institute on Alcohol Abuse and Alcoholism.