McDonald's working on oil with lower fats, trans fatty acids.(Chicago Tribune)

Byline: John Schmeltzer

CHICAGO _ A little more than a year after McDonald's Corp. extended its timetable to develop a healthier cooking oil, the fast-food giant is tinkering with a new formula in a handful of restaurants across the country.

Mike Donahue, vice president of corporate communications for McDonald's, said the company now is making rapid progress in conjunction with Cargill Corp. in developing an oil that is lower in trans fatty acids and saturated fats.

Trans fatty acids can lower helpful HDL cholesterol levels while raising LDL (bad) cholesterol. It is created when manufacturers add hydrogen to vegetable oil _ a process called …