New tests find that McDonald's French fries contain higher levels of trans fats than previously disclosed. The new tests found 8 grams of trans fats in a large servinig of fries -- one-third more than McDonald's claimed.

Trans fats contribute to harmful cholesterol buildup and heart disease. Official U.S. government dietary guidelines recommend next to zero consumption of trans fats.

McDonald's has been trying to rebuild confidence in its menu after repeated criticism of its menu choices and cooking methods.

"It makes it harder to trust McDonald's if they suddenly have strikingly different trans fat numbers. said Michael Jacobson executive director of the Center for Science in the Public Interest.

McDonald's nutrition director, Cathy Kapica, said the company's new test was part of its attempt to provide customers with the best information and menu choices.