Contrary to expectations, the salt intake of Americans has remained consistent over the past five decades, according to a study conducted by researchers at the Harvard School of Public Health.

Adam M. Bernstein, a research fellow in nutrition at HSPH, and Walter C. Willett, chair of the HSPH nutrition department, found that Americans consume around 3,700 milligrams of sodium per day—about 50 percent over the recommended amount. The study indicates that sodium intake has remained steady over the past 50 years.

The duo analyzed the results of 38 past studies from 1957 to 2003 that examined the amount of sodium excreted in urine samples over 24 hours to gauge the overall daily intake of sodium.

The researchers said that this method is more reliable than that used by the National Health and Nutrition Examination Survey, which tabulates people’s reported intakes instead of performing direct measurements. The survey concluded that the salt intake of Americans increased over the past few decades.

Bernstein and Willett initially expected to see a similar increase in salt intake over time, given that people consume more processed foods than in previous decades. But their recent study indicates the opposite trend.

Bernstein said that one possible explanation for the unexpected result is the greater use of table salt in the past, which balances out the greater consumption of processed foods today.

High sodium intake is linked to an increased risk of heart disease, high blood pressure, obesity, and even stomach cancer. The American Heart Association and the Institute of Medicine recommend a daily sodium intake of 2,300 milligrams, or the equivalent of one teaspoon of salt per day. Bernstein said that he would recommend 1,500 milligrams of sodium per day for young adults.

He added that he disagrees with the notion that Americans require a certain amount of salt in their diets because some populations around the world—such as those in the Amazon or Japan—have traditionally consumed much lower levels of salt compared to the average American.

This article has been revised to reflect the following correction:

CORRECTION: October 27, 2010

An earlier version of the Oct. 27 news article "Salt Intake Remains the Same" incorrectly stated that the Harvard researchers analyzed the results of 28 past studies. In fact, they analyzed 38 studies.