Monday, 29 January, 2001, 11:20 GMT

Coffee 'increases stress'

Office managers who want to get the best out of their workers should put a limit on how much coffee and tea they drink each day.

Researchers have found that caffeine intake may be partly to blame for office workers' poor performance.

They found that drinking 350mg of caffeine can cause lapses in concentration and increased stress.

The average cup of coffee contains about 100mg of caffeine.

Of 1,000 office workers surveyed for Volvic mineral water, 76% said they drank tea, coffee or caffeinated cola more than three times during the working day, with one in 20 consuming more than 10 drinks.

Stress specialist Dr David Lewis, who analysed the research for Volvic, is calling for traditional morning and afternoon breaks to be scrapped.

Toilet visits

He said: "Our clinical research found that a high caffeine intake (more than 350mg during the working day) acts as a powerful diuretic and causes people to visit the toilet more frequently, which can lead to performance-zapping dehydration.

"This, coupled with the powerful stimulating effects of caffeine, increases stress and causes failures in concentration."

Sarah Schenker, a dietician for the British Nutrition Foundation, said there was nothing wrong with people drinking three or four cups of coffee a day - provided that they also drank water or other decaffeinated drinks to compensate.

She said: "If you only drink caffeinated drinks then you will become mildly dehydrated. It has been shown that just 2% dehydration does affect concentration, and also makes you irritable."

The study found 93% of workers surveyed drank at least one caffeinated beverage a day.

More than half of those polled who consumed more than three servings of tea, coffee or cola a day complained of stress-related problems.

Almost eight out of 10 of those surveyed drank tea, coffee or cola either first thing or mid morning - periods of the day in which stress levels also peak for most workers.