The University of Dundee is developing a flapjack, which contains a tiny amount of a "marker" substance that helps doctors make a diagnosis.

All the patient has to do is breathe into a tube after eating the cake - and analysis of the samples can shed light on a variety of conditions.

The test may help athletes maximise their performance

Dr Wolfram Meier-Augenstein is hopeful that breath tests can be used to collect information on irritable bowel syndrome, dyspepsia, Aids and diabetes.

The process could even help pharmacologists work out how quickly drugs enter the body, and top athletes discover their optimum performance diet before a competition.

He said: "Breath tests are a simple, cheap, non-invasive form of test carrying no risk - they can even be carried out in a GP's surgery."

Passes the taste test

Existing breath tests have failed to find favour, mainly because of their unpleasant smell and taste, and Dr Meier-Augenstein said he hoped the flapjack would overcome the "yuk" factor.

"The Dundee flapjack tastes nice, has a long shelf life, so it can be kept in surgeries as an off-the-shelf test, and can be taken by patients old and young, male and female without any risk."

The principal testing ingredients of the flapjack are marked sodium acetate molecules, which are broken down into marked carbon dioxide molecules by the body.

These can be detected and measured in the breath.

The project has now secured £356,000 worth of research funding from a medical foundation.

The research group is aiming to develop more breath tests to monitor liver function, which can currently only be done with invasive liver biopsies or blood tests.