Health officials currently say no adult should eat more than a teaspoon of salt each day. They go on to advise that 70 percent of adults -- including people with high blood pressure, all African-Americans and everyone over 40 -- should actually limit their salt intake to a more restrictive two-thirds of a teaspoon.
Sodium increases the risk of high blood pressure, which is major cause of heart disease and stroke. Salt -- or sodium chloride -- is the main source of sodium for most people.
Overall, only 1 in 10 adults meet the teaspoon standard, said the CDC study. But for those who should be even stingier, only 1 in 18 manage to do it.
The research repeated what others have found, that the vast majority of dietary salt comes from processed and restaurant foods. And it concluded that salt was most commonly found in cold cuts and other meats, and in baked goods and other items counted as grain-based products.
"It's not a matter of Americans taking a salt shaker and adding salt to their food," said Linda Van Horn, a Northwestern University medical school professor who chairs the American Heart Association's Nutrition Committee.
Salt reduction has become a recent focus of public health campaigns. New York City, the heart association and nearly three dozen other groups have been trying to persuade food manufacturers and chain restaurants to reduce salt content by more than 50 percent over the next 10 years. The CDC and federal health agencies also have had sodium-reduction talks with food companies.
The CDC study is based on a national survey of nearly 4,000 adults ages 20 and older in the years 2005 and 2006. They had their blood pressure taken and answered questions about what they ate.
The participants tended to consume roughly 1 1/2 teaspoons of salt each day. People in the more restrictive group -- those at increased risk of high blood pressure -- were eating twice as much as they should have, the study found.
One in three U.S. adults has high blood pressure, and the government estimates that nine in 10 will develop it in their lifetime.