COWS that graze as nature intended are producing healthier and better quality milk, according to a study by North-East researchers.

The study by Newcastle University scientists found that grazing cows on organic farms in the UK produce milk that contains significantly higher beneficial fatty acids, antioxidants and vitamins than their non-organic counterparts.

During the summer, one of the beneficial fats - conjugated linoleic acid, or CLA9 - was found to be 60 per cent higher.

Gillian Butler, livestock project manager for the Nafferton Ecological Farming group at Newcastle University, who led the study, said: "What is different about this research is it clearly shows that on organic farms, letting cows graze naturally, using a forage-based diet, is the most important reason for the differences in the composition between organic and conventional milk."

Scientists found that levels of nutritionally desirable fatty acids and antioxidents were highest in the summer, when cows are eating fresh grass and clove. Now the aim is to improve the nutritional composition of milk during the winter, when cows are kept indoors and fed on conserved forage.

Gordon Tweddle, who produces organic milk at the Acorn Dairy in Archdeacon Newton, near Darlington, was one of the farms that took part in the study.

Mr Tweddle said: "We have believed for some time that organic milk is better for us and our customers tell us it tastes better.

It is satisfying to have the scientific explanation as to why it is also nutritionally better."

CLA, omega-3 fatty acids, vitamin E and carotenoids have all been linked to a reduced risk of cardiovascular disease and cancer.

The study involved 25 farms across the UK in two contrasting areas of the UK - South Wales and the North-East.

Dr Madelaine Portwood, a North-East educational psychologist, said: "Organic milk is probably comparable with milk from 20 years ago. It is returning to what it was"