Watch free video Salt Warning Rule at Chain Restaurants

New York City begins a new era in nutritional warnings this week, when chain restaurants will have to start putting a special symbol on highly salty dishes.

The first-of-its-kind rule, which takes effect Tuesday, will require a salt-shaker emblem on some sandwiches, salads and other menu items that top the recommended daily limit of 2,300 milligrams — about a teaspoon — of sodium.