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Two major U.S. cities are taking action to help people eat healthier food. New York city officials are poised to require a warning label on high-sodium menu items at chain restaurants, while San Francisco moved to ban ads for ads for sugary sodas on public property.

Cities are getting bolder about such measures, aimed at helping people figure out how to avoid the unhealthiest foods.

New York's Health Department will propose Wednesday that all chain restaurants add a symbol resembling a salt shaker on menus next to food products that contain more than the recommended daily limit of 2,300 milligrams of sodium, equal to about 1 teaspoon of salt, the Associated Press reported.

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Sodium can raise blood pressure, which can lead to heart attack and stroke. Studies have found that the vast majority of dietary salt comes from processed and restaurant foods. Average sodium consumption is about 3,400 milligrams of sodium each day. Only about one in 10 Americans meets the 1 teaspoon guideline.

"This doesn't change the food. It enables people to identify single items that have a level of salt that is extremely high so that they can modify their menu selections accordingly,” said Dr. Mary Travis Bassett, commissioner of the New York City Department of Health and Mental Hygiene.

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Michael Jacobson, executive director for the Center for Science in the Public Interest, a Washington-based advocacy group, called it "an extremely important proposal."

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Marion Nestle, a food policy expert at New York University, said the proposal might encourage restaurants to help figure out ways to cut down on salt. "The big problem here is nobody wants to go first. Food companies don't want to start reducing their salt unless everybody else does," Nestle said. "That's why we need regulation in my view."

Also Tuesday, the San Francisco Board of Supervisors passed legislation to require health warnings on ads for sugar-sweetened drinks and banning ads on publicly owned property. The measure also forbids the use of city funds to buy sodas.

"These health warnings will help provide people information they need to make informed decisions about what beverages they consume," city supervisor Scott Wiener said in a statement.

"Requiring health warnings on soda ads also makes clear that these drinks aren't harmless - indeed, quite the opposite - and that the puppies, unicorns, and rainbows depicted in soda ads aren't reality."