SEATTLE -- The King County Board of Health is telling county restaurants they should phase out trans fat.

The board also decided this week that chain restaurants should be required to provide nutritional information for all menu items.

The new rules were adopted Thursday after about six hours of discussion and comments from members of the public.

The ban affects 10,000 licensed kitchens in the county.

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SURVEY: Ban Trans Fats In King County?

According to a recent study by the Harvard School of Public Health, replacing trans fats with unsaturated fats would prevent 30,000 to 100,000 premature deaths nationwide every year.

Some major restaurant chains have switched, including McDonald's, Wendy's and KFC.

Some local restaurants like Beth's Café on Aurora Avenue in north Seattle and Spud Fish and Chips at Green Lake have changed.

Dick's Hamburgers has been experimenting with alternative cooking oils, but the local chain hasn't found one that meets its standards, according to the Seattle Times.

The restriction would be phased in over nine to 18 months.

New York City, Philadelphia, Montgomery County, Maryland and Brookline, Mass. have all passed measures that will require restaurants to phase out their use of trans fats, according to the Center for Science in the Public Interest.