Gov. Arnold Schwarzenegger signed legislation that will ban restaurants and other retail food establishments from using oil, margarine and shortening containing trans fats.
In a statement, Schwarzenegger noted that consuming trans fat is linked to coronary heart disease.
"Today we are taking a strong step toward creating a healthier future for California," he said.
Violations could result in fines of $25 to $1,000. Food items sold in their manufacturers' sealed packaging would be exempt.
New York City, Philadelphia, Seattle, Baltimore and Montgomery County, Md., have ordinances banning trans fats, but California is the first state to adopt such a law covering restaurants, said Amy Winterfeld, a health policy analyst for the National Conference of State Legislatures.
California and Oregon already had laws banning trans fats in meals served at schools, she added.
The legislation signed by Schwarzenegger will take effect Jan. 1, 2010, for oil, shortening and margarine used in spreads or for frying. Restaurants could continue using trans fats to deep-fry yeast dough and in cake batter until Jan. 1, 2011.
Trans fats occur naturally in small amounts of meat and dairy products. Most trans fats are created by adding hydrogen to liquid oil turning them into solid fat, like shortening, reports CBS News correspondent Sandra Hughes. Transfats are found in everything from microwave popcorn to cookies and potato chips.
Trans fats increase bad cholestrol which contributes to the development of heart disease,stroke, obesity and diabetes, according to the New England Journal of Medicine.
"I would say if we could reduce or eliminate trans fats in the American diet, it would go a long way toward reducing the burden of cardiovascular disease," Dr. Russell Berdoff of Beth Israel Medical Center told CBS News.
Stephen Joseph, a Tiburon attorney who was a consultant to New York City in developing its ban, said trans fat is a larger health risk than saturated fat because it reduces so-called good cholesterol.
Trans fats are like cigarettes, with no safe level of consumption, said Jeffrey Luther, a Long Beach doctor who is president of the California Academy of Family Physicians.
He said the California law, "when it finally takes effect, will be a tremendous benefit."
The California Restaurant Association opposed the bill. Spokesman Daniel Conway said the federal Food and Drug Administration rather than individual states should be developing regulations on trans fat use.
He said, however, that the association has no plans to challenge the law, in part because restaurants already are phasing out trans fats to satisfy customers. Several major fast-food chains have announced that they have eliminated trans fats from their menus or intend to so do in the near future.
"We're confident that California restaurants can meet the mandates of the bill," Conway said.