Alcohol units haven't got bigger, drinks have

Your alcohol consumption has just gone up without you touching a drop. In fact, the average male has seen his weekly consumption go up by a quarter from about 16 units to about 20.

How come? The Office of National Statistics has just recalculated the way it estimates how much alcohol is in our drinks. It has done this because the last few years have seen stronger drinks being served in larger glasses with the result that while we might still be drinking the same number of 'drinks' a night or per week, each one of those drinks is stronger.

The main factors the ONS has taken into account are:

• increases in the size of glass in which wine is served on licensed premises;
• the increased alcoholic strength of wine;
• better estimates of the alcoholic strengths of beers, lagers and ciders.

Applying the changes to 2005 data suggest that the number of units in wine has been underestimated. So, to a lesser extent, have the number of units in beer, lager and cider.

Overall, the change in method increases the UK's average weekly alcohol consumption by about one third, from 10.8 units to 14.3 units.

Since a higher proportion of women's than of men's consumption is wine, the increase is greater for women: men's consumption increases by about one quarter, from 15.8 to 19.9 units, women's by just under one half, from 6.5 to 9.4 units.

So how has it happened?

In the UK one unit of alcohol is 10ml (or 8 grams) of pure alcohol. Typically we've taken half a pint of beer or a small glass of wine as including one unit of alcohol. But this was based on English bitter which is usually around 3.5% alcohol by volume (abv) rather than continental lagers which are frequently 5% abv or even 9%. Similarly wine used to be 9% abv and served in 125ml glasses. But these days most wine is now about 11-13% and most pubs and bars serve it in 175 ml glasses or even 250ml (which is a third of a bottle!)

Alison Rogers, Chief Executive of the British Liver Trust, said: 'Drinkers remain unclear about how many are in an average pint or glass of wine. What is clear is that over the last 30 years alcohol has not only become cheaper but stronger. Red wines in particular are now commonly hitting an abv of 14%. This is costing us dearly in terms of our health and, in more and more cases, our lives. '

The changes will be introduced on government surveys like the General Household Survey (GHS), the Health Survey for England (HSE) and the ONS Omnibus Survey.

So there you are, Christmas is just around the corner and already you're drinking more than you realise. Check the strength of your booze.