The study also found from lab tests that "CLA isomers and CLA in milk fat caused the death of cancer cells, demonstrating the potential of CLA in reducing cancer tumours".
Scientists from Ireland's Teagasc food research centre worked alongside those from Dublin City University and University College Cork on the project.
The study is one of the most significant in a series of studies suggesting that cows' diets play an important role in the nutritional quality of their milk.
Some studies on animals have shown CLA to be effective in fighting and preventing certain cancers, while trials on both humans and animals have also shown CLA can help to reduce body fat in the long term.
At Teagasc, cows were fed 100g of sunflower oil per day and left to graze on grass. The results found that a six-month cheddar cheese made from their milk contained 1.84g of CLA per 100g, more than double that of the cheese made from the milk of a 'control herd' - kept indoors with no oil.
Project leader Dr Catherine Stanton, from the biotechnology department at Teagasc, said the research was very important because it shows that CLA levels could be elevated significantly and that "you can do it through very simple management approaches".
She added that the CLA had no effect on the flavour of the cheese, which remained completely stable throughout the six-month ripening period.
Stanton told www.DairyReporter.com that CLA-enriched dairy products have great potential for producers in the current wave of consumer health trends.
"We have the information and the know-how, it's more a case of if the consumers are ready for it. You have to ask, do they know anything about it [CLA], and I think the answer to that at the moment is no."
But, she expects consumer awareness to improve. Stanton is currently co-ordinating another project with European researchers on the production of CLA-enriched foods through natural means. The findings are set to be published widely next year.
"I think CLA is one of the next things that will be given a wider audience," she said likening the situation to omega-3 and probiotics that are already catching the public radar.
CLA has so far been used mainly by the supplements industry, with its use in food still very rare across Europe. Spain has so far led the way in Europe through CLA-enriched dairy foods and cookies.
"We need more human studies and education for consumers," said Stanton, adding that manufacturers themselves would inevitably have to pick up some of the promotional costs.
One problem will be how to present CLA in both a way that consumers understand and so that it complies with unspoken functional food codes, especially in relation to CLA's suggested anti-cancer properties.
At a talk on functional dairy at the recent Drinktec expo, Dr Michael de Vrese, of Germany's Federal Research Centre for Nutrition and Food, said it was still generally forbidden to claim a product may directly prevent a particular disease, although risk reduction claims will be tolerated in the European Union.
There are 28 different types of CLA, though the type most commonly found in dairy and meat products is generally referred to as 'cis-9, trans-11 CLA'.