Have you really had your greens? New test to tell doctors what we're eating

A simple test to check whether patients are eating their recommended five portions of fruit and vegetables a day could be introduced in Britain within five years.

Scientists have developed a prototype test which tells them what people have been eating over the past week. They believe it will be an invaluable weapon in the battle against obesity and in aiding research into cancer, heart attacks and diabetes.

The test, developed by researchers at the universities of Aberystwyth and Newcastle with Food Standards Agency funding, relies on the identification of the chemical fingerprints of substances found in urine that have been created by different foods as they pass through the body. Chemical signatures for raspberries, broccoli, orange juice and salmon have already been successfully profiled. The team is confident that, in time, virtually every food ingredient will be identifiable.

The urine sample currently has to be sent to a laboratory for examination but Professor John Draper, who led the work at Aberystwyth University, believes that the first commercial dip-stick tests could be available within five years.

He said it could be an important tool for nutrition experts and medical staff trying to monitor the eating habits of obese patients trying to lose weight. But even more important, he believes, are the potential applications for scientists trying to establish links between diet and diseases.

Thousands of research papers are published every year pointing to links between food and disease or disease prevention, yet in only a handful of cases can scientists say connections are proven, because of doubts about the reliability of records of patients' diets.

"It should mean that for the first time researchers will be able to say for certain which items of food help protect against specific diseases, and those that can seriously increase the chance of getting a particular disease," he said. It would also open the way for food retailers to advertise more foodstuffs as having health-giving properties, a ploy largely denied them until now because of doubts as to the reliability of evidence.