New York City’s sodium labeling warnings on menu items went into effect today, making America’s most populated city the first US city to require chain restaurants to post the warnings.

Under the new rule, food service establishments with 15 or more locations nationwide are required to post icons—a triangle with a salt shaker inside—next to menu items that pack 2,300 milligrams or more of sodium, the total recommended daily limit.

According to the New York City Department of Health, this includes combo items, such as an order-by-number meal that might include a soup and a sandwich or a burger and french fries. The rule also requires chain food service establishments to post a warning statement where customers place their orders. The statement explains that items with the icon have more than the recommended daily limit of sodium and that high sodium intake can increase blood pressure and risk of heart disease and stroke. The city’s Board of Health unanimously passed the rule in September.

“The vast majority of adults in New York City consume more sodium than recommended, and too few understand the link between high sodium intake and hypertension, heart disease, and stroke,” says Dr. Mary Bassett, New York City health commissioner. “These warnings are needed in restaurants because the majority of sodium in our diet is not coming from what we decide to add with the salt shaker at the table, it’s already in the food when we buy it. These icons will help New Yorkers make more informed choices when dining out.”

According to the Health Department, the average New York City adult consumes almost 40 percent more sodium than the recommended limit per day. With chain restaurants constituting about one-third of all restaurant traffic in the city, health officials hope the new warnings will facilitate education and inform consumers of the risks certain products pose.