Five major fast food chains have significantly decreased trans fats in the oils they use to cook food, according to new research from the University of Minnesota School of Public Health.

The latest research findings suggest that major fast food chains may have been responsive to health concerns from the public and that potential future marketplace shifts to watch for in response to current nutrition concerns include changes to sodium and energy content of fast food restaurant items.

By using the School of Public Health's Nutrition Coordinating Center's proprietary database -- which catalogs the nutritional values of more than 18,000 foods -- researchers looked at trans fat and saturated fat levels in french fries from five major fast food chains: McDonald's, Burger King, Wendy's, Jack in the Box and Dairy Queen.

The researchers found that three of the restaurants -- McDonald's, Burger King, and Wendy's -- significantly decreased the trans and saturated fatty acid composition of French fries between 1997 and 2008. For these three restaurants, saturated fats either went down or stayed level. While the remaining two restaurants didn't show a decrease in trans fats during the time period studied, current nutritional information illustrates that the chains have decreased both trans and saturated fatty acid composition since 2008.

The findings were presented at the National Nutrient Database Conference in Grand Forks, North Dakota.

"While it took time for major fast food chains to decrease trans fats in their foods, I'm pleased to see that they have done it. I'm also pleased to see that they haven't raised levels of saturated fats to replace trans fats," said Lisa Harnack, Ph.D., an associate professor of epidemiology in the School of Public Health and director of the Nutrition Coordinating Center. "This is good news, as the average American gets about 10 percent of calories from fast food. But moderation is still key when considering fast food. Calories and sodium are high and portion sizes are often too large."

Throughout the past decade, trans fats began receiving a great deal of negative attention after research demonstrated that they can elevate the risk of heart disease by increasing "bad" LDL cholesterol and decreasing "good" HDL cholesterol levels. Health authorities worldwide recommend that consumption of trans fat be reduced to trace amounts. In 2006, Congress passed a law requiring that trans fat content be listed on food labels.

The study was funded by the National Institutes for Health.