More than 40 percent of the sodium children consume comes from what are typically their favourite foods, including pizza, sandwich meats, cheese, chicken nuggets and pasta dishes, said the report by the US Centres for Disease Control and Prevention.
Kids aged 6-18 eat an average of about 3,300 milligrams of sodium a day before salt is added at the table, the report said. That is far higher than the 2,300 milligrams per day recommended by the 2010 Dietary Guidelines for Americans.
"Too many children are consuming way too much sodium, and the result will be risks of high blood pressure and heart disease in the future," said CDC director Tom Frieden.
"Most sodium is from processed and restaurant food, not the salt shaker. Reducing sodium intake will help our children avoid tragic and expensive health problems."
Read: Obesity prevention keeps kids' blood pressure down
The data was based on findings from the CDC's 2009-2010 National Health and Nutrition Examination Survey.
Lunch and dinner tended to be the most salty meals of the day, said the report.
"Most sodium is already in food before you buy it or order it. About 65 percent comes from store foods, 13 percent from fast food and pizza restaurant foods, and nine percent from school cafeteria foods."
Parents and caregivers are urged to give kids plenty of fruit and vegetables, alongside wholesome, unprocessed foods as often as possible, the CDC said in a statement.
Schools could help by reducing sodium in food and putting lower-sodium alternatives in vending machines and cafeterias, it added.
"The dangerously high levels of sodium children are consuming demand action from the Food and Drug Administration," said the Centre for Science in the Public Interest, a consumer group.
"We are sentencing all too many children to premature death from heart disease and stroke."
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