Fast food from McDonald's is healthiest in Denmark and worst in the United States, a Danish study comparing levels of the deadliest kind of fat, trans fatty acids, showed.

The study, conducted by researchers at Gentofte University Hospital in Denmark and published in this week's edition of the New England Journal of Medicine, compared meals bought at McDonald's and KFC in 20 countries around the world.

A large meal of chicken nuggets and french fries at McDonald's in the United States contained 10.1 grams of trans fatty acids, while the same meal in France contained 5.9 grams and just 0.33 grams in Denmark, Steen Stender, who headed the research project, said.

"Many people think that wherever you go in the world you get the same thing at McDonald's, but in fact that is not the case," Stender said.

The low Danish levels are the result of low-fat legislation introduced in 2004. Under the new law, no more than 2 percent of fats in foods sold to customers can be industrially produced trans fats. Food producers violating the law risk two years in prison.

For a meal of chicken nuggets and potato wedges at KFC, the lowest level of trans fatty acids was registered in Germany, with 0.4 grams, compared with the highest level in Hungary, which had 24.1 grams.

Trans fatty acids clog the arteries and are linked to increased risk of heart disease.

"Studies show that five grams of trans fat per day increase the risk of heart disease by 25 percent," Stender said.

Food manufacturers add trans fatty acids to cut costs, as they prolong the shelf life of prepackaged foods. In the case of fast-food restaurants, french fries can be fried in the same oil several times and the frying fat can be stored longer.

Editor: Donald