Tesco has begun to sell 'weight watchers' wine, which is a simple German white wine that is low in alcohol and therefore lower in calories. On average between 10% and 12% of a bottle of wine will be alcohol. Now for a little maths: a gram of alcohol provides 7 calories, so a bottle of wine will contain approximately 10% of 750 grammes - i.e. about 75 grammes of alcohol. Multiply that by 7 and you find that a bottle of wine contains roughly 525 calories.

I've often wondered why the standard bottle size of wine is 750 millilitres, but let me go through another calculation with you. If you ingest alcohol at about a 10% dilution - pretty much how it comes in wine - your body can metabolise half a gramme of alcohol per pound of body weight every 24 hours. For an averagely sized man of about 150 pounds that works out at 75 grammes - which also happens to be the amount of alcohol you find in a standard bottle of wine.

The important part of these calculation is that the alcohol has to be drunk at well spaced intervals over the 24 hours. If it is, then it will completely disappear in the body, leaving no trace in the blood or urine. If it is taken all at once, then there is excess alcohol that the body cannot metabolise and that's what causes you to feel drunk.

In these socially conscious days we're increasingly aware of the effects of alcohol on driving. We can use the above information to work out a tolerable amount of alcohol that would leave you fit to drive. A bottle of wine contains 6 glasses and you can metabolise that (assuming you're about 150 pounds in weight) in 24 hours, so that's one glass of wine every three hours. If you drink two glasses of wine over a three hour dinner, then one glassful will be metabolised, and one glassful will remain in the bloodstream for the Guards to breathalyse. At today's levels of permitted alcohol that won't put you over the limit, but a third glass of wine probably would.

The average daily calorific expenditure is 3,000 calories, so a bottle of wine containing 525 calories can contribute about 17% of your daily calorific requirement. In fact in much of the world it does just that, but these days we like scientific data. There have been some interesting experiments to provide that: in one by W.O. Atwater at the American Academy of Science, volunteers were given 72 grammes of alcohol a day, where it was found to replace carbohydrates and reduced carbohydrate hunger, making it easier to do without sugar. In short, used like this, it can help you lose weight.

Wine of the Week.

Lindemans Cawarra 2002, Shiraz / Cabernet

Lindemans is one of Australia's big brands and it's been around for a long time, delivering well-made wines for very reasonable money. This one has all the big beefiness of an Australian Shiraz, but you can also find an underlying suppleness that's a factor of the Cabernet Sauvignon content. At this price level it represents a good value wine.

Available Dunnes Stores, RRP €7.99