Food packaging could be embedded with computer chips that instantly link your phone to an on-line sustainable food guide, a UK conference has heard.

The guides would help consumers navigate their way through the ethical and ecological decisions about what they eat, the proponents argue.

The UK should lead Europe on this approach, food policy expert Professor Tim Lang said.

He was speaking at the British Association Science Festival.

Ethical impact

The criteria used to judge food sustainability are still up for debate.

"Do I eat green beans from Kenya, because they are good for me, or do I say no because there are four litres of water embedded in each stem of green bean?" asked Professor Lang, from City University, London.

He said scientists and policy-makers now realised the environmental, ethical, and health impacts of the food we ate.

Producers needed to find a way to present this information to the consumer, he told the conference.

He outlined a number of criteria that consumers should consider when buying food: how much energy and water are used to produce each calorie of food; what is the impact of the food item on climate, biodiversity, and the labour-force of the country it was grown in, and what are the health and financial costs of food.

Criteria agreement

"Packaging could be the point of entry for [this] information," said Professor Lang.

Information on socio-economic and environmental criteria could be presented simply through "food flowers" - diagrams where each petal represents a different impact, with the shaded area of a petal showing how highly a food item scores.

The more detailed information could be accessed from a website and uploaded from food packaging to our mobile phones.

There would, however, need to be universal agreement on which issues should be reflected in the labels.

"That needs governments to agree with companies, to agree with civil society to agree what those criteria are," explained Professor Lang.