The great virtue -- or perhaps drawback -- of McDonald's and KFC is that the food is pretty much the same the world over. But a new study suggests the fries and the chicken served in the United States may have much more artery-clogging trans fat.
The chief reason, researchers say, is the type of frying oil used: partially hydrogenated vegetable oil, which is high in these fats.
A Danish study of the fast-food chains' products around the world found remarkably wide variations in trans fat content from country to country, from city to city within the same nation and from restaurant to restaurant in the same city.
At a New York City McDonald's, a large fries and chicken nuggets combo was found to contain 10.2 grams of trans fat, compared with 0.33 grams in Denmark and about 3 grams in Spain, Russia and the Czech Republic.
At KFCs in Poland and Hungary, a large hot wings and fries order had 19 or more grams of trans fats, versus 5.5 grams for wings and fried potato wedges in New York and less than a gram in Germany, Russia, Denmark and Aberdeen, Scotland.
"I was very surprised to see a difference in trans fatty acids in these uniform products," said one of the researchers, Dr. Steen Stender, a cardiologist at Gentofte University Hospital in Hellerup, Denmark, and former head of the Danish Nutrition Council.
McDonald's Corp., which promised in September 2002 to cut trans fat in half, and KFC parent Yum Brands Inc. said the explanation is local taste preferences.
But nutrition experts and consumer activists said it is about money: Frying oil high in trans fats costs less.
In the study, researchers tested products from the chains' outlets in dozens of countries in 2004 and 2005, analyzing McDonald's chicken nuggets, KFC hot wings and the two chains' fried potatoes. The findings were reported in Thursday's New England Journal of Medicine.
Partially hydrogenated vegetable oil is liquid oil that has been treated with hydrogen to harden it and give it a longer shelf life. Switching to liquid vegetable oils such as canola, corn, olive or soy eliminates the trans fat. This has been done in Denmark under a 2004 law that allows only a minuscule amount of trans fat in processed foods.
Trans fat raises bad (LDL) cholesterol and lowers good (HDL) cholesterol. Eating just 5 grams of it per day increases the risk of heart disease 25%, research shows.
"Per gram, it is more harmful than any other kind of fat," Stender said.
