In the biggest change to the menu since it started selling Diet Coke, Dick's has begun experimenting with different oils for its fries.

Over the past four months, cooks have conducted side-by-side tastings of potatoes fried in Primex — the oil that has created the crispy magic since Dick's opened in 1954 — vs. nontrans-fat oils.

It's a risky enterprise for a reputation built on flavors that never change.

"Our goal is to remain the same so our customers will have the same experience they had in '54, '64 or '74," said Ken Frazier, general manager for the five Dick's Drive-Ins. "Consistency is an absolute for us."

He has not found an acceptable alternative. Soon he may have to.

To reduce the risk of heart disease, the King County Board of Health is expected to vote July 19 on whether to require all restaurants and food services to stop using trans fats. Primex is a trans fat.

The ban would affect 10,000 places licensed to serve food in the county, including 2,200 restaurants as well as meal programs, fair booths and farmers markets.

Bans already have been approved in New York City, Philadelphia and Montgomery County, Md.

"I don't care if you eat French fries," said Seattle City Councilmember Sally Clark, a member of the health board. But when they're fried in trans fat, she said, "I end up paying for your heart disease. It's costing us money."

The board is also considering legislation that would require chain restaurants to post nutritional information on their menus and menu boards.

A menu board, for example, would have to list how many calories are in each sandwich, along with the price.

Phased in after vote

If approved, the trans fat ban will be phased in nine to 18 months after the vote, depending on the type of food.

Several board members have said they support a ban.

Trans fats are vegetable oils that have been chemically hydrogenated to prevent them from becoming rancid.

The process turns the liquid oil into a solid, such as shortening or hard margarine, and helps extend its shelf life and reduce flavor transferring — for instance, when you fry chicken in oil that's been used to fry fish. It's also commonly found in baked goods and commercially prepared foods.

Trans fats have been found to raise the risk of heart disease, and a study by the Harvard School of Public Health estimates that replacing them with unsaturated fats would prevent 30,000 to 100,000 premature deaths a year.

"When you go into the grocery store, the label on the package gives us information," said Board of Health Chair and County Councilmember Julia Patterson, D-SeaTac.

In 2006, the federal government began requiring packaged foods to break out the amount of trans fat in its labels. "We don't have that information when we eat out at restaurants," Patterson said.

Several national restaurant chains have either phased out trans fats or announced plans to do so, including Burger King, McDonald's, Wendy's and KFC.

Starbucks plans to eliminate trans fats by the end of the year at its North American stores.

"It's something that public health agencies have a responsibility to protect people from, just like lead in paint or lead in gasoline," said Margo Wootan, nutrition director at the Center for Science in the Public Interest in Washington, D.C. "It's a food additive that harms people's health."

The Washington Restaurant Association is worried a ban may be inflexible.

"What I don't want to see is the industry basically being penalized for doing the right thing, which is to set up arbitrary dates and say you need to comply by a certain date when we're not even sure products will be available," said Trent House, director of government affairs for the association.

For Dick's, Frazier said, there were no alternatives until a year ago.

He said new oils have since been developed but "the availability is limited because it can't possibly meet the current demand. All these things have to come online slowly."

Menu information

The proposed menu labeling law would apply to chain restaurants with 10 or more locations nationally.

In addition to posting calories on menu boards, restaurants also would have to print information on menus about the amount of trans fat, saturated fat, carbohydrates and sodium in each dish.

New York City passed similar labeling legislation, and the state restaurant association there has filed a lawsuit to stop the law from taking effect.

"There isn't a lot of research out there that says menu labeling will have that much of an impact" on people's health, said House, of the Washington Restaurant Association.

He estimates about 55 chains operate in King County, but does not know the number of locations.

He wants the Board of Health to instead work on serving as a resource for information, such as helping restaurants determine healthy choices to recommend to customers.

But Wootan says there's no substitute for menu labeling. "People go into Starbucks and order a coffee and pastry and they think of it as a snack," she said.

"One café mocha and a scone has about 1,000 calories." (About 950 calories for a venti mocha with whole milk and a cranberry-orange scone, according to Starbucks' Web site.)

Sharon Pian Chan: 206-464-2958 or schan@seattletimes.com