It's not so easy to know when to say when, especially when the amount of booze poured in bars, restaurants and clubs varies so widely.
Most alcohol research tends to deal in the standard drink -- whatever contains 0.6 ounces or 1.2 tablespoons of pure alcohol, be it 1.5 ounces of 80 proof liquor, 5 ounces of wine, 12 ounces of beer or assorted spirits of other strengths.
But just as the portions in many a fast-food restaurant are "super-sized," a new study finds that the same thing holds true in bars and restaurants, at least in northern California.
William Kerr and colleagues with the Alcohol Research Group, part of the non-profit Public Health Institute in Oakland, Calif., went on a government sponsored pub crawl of epic proportions in the spring of 2007, hitting 80 establishments in 21 towns in 10 counties, ordering up 480 drinks.
Not that anyone did much drinking. These were scientific samples and each was carefully measured, with test tube samples taken for analysis later on 357 drinks.
They either took the word of the beverage's brand label or relied on direct analysis of a sample to determine the alcohol concentration of each serving of beer, wine or spirits.
Kerr said one key finding was that "the typical wine, beer or mixed spirits drink in bars is larger than a standard drink, often by 50 percent or more." So much for those watered down drinks.
And within beverage types, the alcohol content can vary widely, no matter what labels may say.
Specifically, the average glass of wine was 43 percent larger than a standard drink, and no difference was found between the reds and whites. The average draft beer was 22 percent larger than the standard 12 ounces. The team did no testing of bottled beer.
The one consistent measure was a shot of whiskey -- shot glasses apparently are pretty uniform. But mixed drinks with liquor were 42 percent larger than the presumed standard serving, a pitfall other researchers have noted before because many cocktail recipes involve several spirits.
Kerr said a lot of factors go into making retail drinks stronger, including glass size, the percent of alcohol by volume in a beverage -- say 15 percent wine versus 11 percent wine, or 6 percent beer versus the 4.2 percent typical in a light draft.
"But probably the most important factor is the intentions of management and the bartender, " Kerr said.
He explained the variance with wine as an example, noting that the types of wine served in bars and restaurants tended to have higher alcohol by volume -- an average of 14 percent, rather than the 12 percent assumed with the standard drink.
"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 cost of a whole bottle. So a larger pour (serving) was needed to make the customer more comfortable with the price for the glass."
Kerr said while some patrons may like the bigger servings, "most on-premises drinkers are not trying to drink as much as possible on every occasion, and this is particularly true for those who intend to drive or engage in other activities."
So, if both the serving size and the alcoholic content by volume are, say, 25 percent higher in each drink, and a patron has three or four of those drinks, then their intake will be much higher -- about two additional standard drinks for every four they buy.
As Kerr points out, "this could have significant and possibly damaging consequences."
That is particularly true as doctors are encouraged to adopt a new screening standard for alcohol problems, asking patients how many days in the past year they had four or more (women) or five or more drinks for men. The assumption is that any day spent drinking that much is cause for concern.
Kerr's study shows that millions of people may truthfully tell their docs they've not had that many drinks in a day, yet if they do their drinking at a bar or restaurant or even at parties where the host pours generously, they may actually be drinking in a danger zone.
The research, sponsored by the National Institute on Alcohol Abuse and Alcoholism, will be published in September in the journal Alcoholism: Clinical and Experimental Research, but was released online lastweek.