LONDON (AP) -- Truth and alcohol may not mix, particularly when people are asked how much they drink.

That's the implication of a study released Wednesday that reveals a big gap between the booze Britons own up to drinking and the amount of alcohol sold nationwide. The study indicates that people routinely underestimate their alcohol consumption by around 40 percent.

That may not be particularly surprising, but the study puts a figure to the phenomenon of the drunk who claims not to have anything more than a couple of beers. Lead author Sadie Boniface said the unreported alcohol equates to nearly one bottle of wine per British adult per week -- an amount she said wasn't just disappearing.

"It has to have gone somewhere," she said in a telephone interview.

Boniface and Nicola Shelton, both with the University College London's Department of Epidemiology and Public Health, derived their figures by comparing self-reported data in a public health survey accounting for 14,041 people aged 16 and up to alcohol sales figures kept by British tax authorities.

The gap was huge. More than 20 percent of Britons' annual wine consumption -- or 2.6 million hectoliters (69 million gallons) -- was unaccounted for. Nearly half of Britons' beer consumption -- 45 million hectoliters (1.2 billion gallons) -- was unclaimed. And Britons seemed particularly reluctant to take credit for gulping down whiskey, vodka, tequila and gin. Nearly 60 percent of Britain's spirit consumption remained unreported.

Boniface said the more accurate reporting of wine versus beer and spirits might have something to do with the cultural baggage attached to them.

"If you think about drinking wine, you generally think of sitting around a fancy meal," she said. "It's thought of as much more of a civilized drinking occasion than drinking spirits might be, although that's just speculation."

The study, published in the European Journal of Public Health, considered a host of other possible reasons for the underreporting. Maybe children under the age of 16, tourists or homeless people -- all groups which wouldn't have been covered by the survey -- were buying the unclaimed booze. Maybe the whiskey was being kept on shelves rather than being sipped after dinner. Maybe the wine was being used in cooking, or thrown out when it expired, or being spilled across white carpets.

Boniface said those factors were all considered and then ruled out.

"It can't be a small minority -- such as homeless people -- that are drinking vast, vast amounts," she said. "It's a widespread problem."

Issues around self-reporting aren't new -- people routinely overestimate their height or underestimate their weight, for example. And it's long been known that alcohol intake is particularly liable to be underreported; Boniface said that many doctors mentally double the alcohol intake given to them by their patients.

But Boniface said the study fleshed out an issue which is particularly salient in the context of Britain's struggle to control a surge in boozing which has seen Britain's annual alcohol-related death toll more than double between 1992 and 2008. If authorities don't know how much Britons are drinking, she said, then how can they get a handle on the situation?

Underreporting has "huge consequences for public health," she said, "and we don't have any idea what they are."

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Online:

European Journal of Public Health: http://eurpub.oxfordjournals.org

Raphael Satter can be reached at: http://raphae.li/twitter