THE debate over the value of organic food was reignited yesterday by a study suggesting that it could have major health benefits.

A team of scientists found rats fed on organic food were slimmer, slept better, and had stronger immune systems than those which ate conventionally-grown produce.

The researchers admitted they could not explain the results, but they were seized on by pro-organic food campaigners, who said the findings were part of a growing body of evidence that suggested conventionally-grown food was not as healthy.

The Danish team, aided by a Newcastle University scientist, experimenting with 36 rats, fed one group with organic food, anotherwith conventional produce with high levels of fertiliser and pesticide, and a third with minimally-fertilised food.

All the rats were given potatoes, carrots, peas, green kale, apples, and rapeseed oil and the level of nutrients was monitored to make sure they were the same for each group.

The scientists found that the rats fed organically-produced food were measurably healthier, in that they slept better, had stronger immune systems, and were less obese.

Dr Kirsten Brandt, of Newcastle University's school of agriculture helped devise the experiment.

She was careful not to overstate the findings however, she said: "The difference was so big that it is very unlikely to be random.

"We gave the food to the rats and then we measured what they were doing. If we want to understand how and why, we need another study.

"We don't know if they slept better because they were less stressed and had a better immune system. These things may be related or not."

Peter Melchett, policy director of the Soil Association, said previous studies found animals fed organically had greater fertility, produced healthier offspring, and recovered better from illness.

He said when the country was farmed organically in previous centuries, there was a lower cancer rate and fewer people suffered allergies. "It is common sense, and it is good to see science is catching up, " he said.