Geneticists have mixed DNA from the roundworm C. elegans and pigs to produce swine with significant amounts of omega-3 fatty acids - the kind believed to stave off heart disease.

Researchers hope they can improve the technique in pork and do the same in chickens and cows.

The Food and Drug Administration has never approved food derived from genetically engineered animals. Unlike crops, the FDA treats such animals as medicine and requires extensive testing before approval.

"We understand that this research is in the very early stages," FDA spokeswoman Rae Jones said. "This technology will not likely reach meat counters for many years."