Scientists have created pigs that produce compounds which have been widely touted as good for the heart.

Much research has suggested that omega-3 fats can cut the risk of heart disease, although the link has been challenged in a new paper.

A University of Pittsburgh-led team used gene technology to breed animals that produce the fats.

The Nature Biotechnology study raises the prospect of a new source for the fats, which humans cannot produce.

Currently, the only way for humans to realise the benefits of omega-3 fatty acids is by taking dietary supplements, eating certain types of plants or oily fish such as salmon and tuna that may also contain high levels of mercury.

The study may also help scientists to analyse the effect of the fats on cardiovascular function, not only in the pigs, but in humans as well.

To stimulate production of omega-3 fatty acids in pigs the researchers transferred a key gene into immature foetal cells that give rise to certain tissues in the fully-developed animal.

The gene – fat-1 – controls the conversion of more abundant omega-6 fats into the omega-3 form.

The researchers then used the genetically-manipulated cells to create a pig using a method called nuclear transfer cloning.

Researcher Dr Randy Prather said: "Pigs and humans have a similar physiology.

"We could use these animals as a model to see what happens to heart health if we increase the omega-3 levels in the body.

"It could allow us to see how that helps cardiovascular function."

Dr Prather said there could also be potential benefits if the animals were put into the food chain."First, the pigs could have better cardiovascular function and therefore live longer, which would limit livestock loss for farmers. Second, they could be healthier animals for human consumption."

Dr Jing Kang, who also worked on the study, said: "Livestock with a health ratio of omega-3 to omega-6 fatty acids may be a promising way to re-balance the modern diet without relying solely on diminishing fish supplies or supplements."

Professor Keith Kendrick, of the Babraham Institute, University of Cambridge, agreed that the genetically-modified pigs might help scientists assess the role of omega-3 fats in reducing cardiovascular disease.

However, he said: "I am less convinced that this is going to be a source of omega-3 for human consumption when there are other non-GM sources."

A review of 89 studies into the health benefits of omega-3 fats published by the British Medical Journal last week concluded that there was little evidence to suggest the oils had a significant impact on health.

However, the researchers admitted more work was required before any definitive conclusions could be drawn.