Before surging obesity rates made villains of trans fats and sugars, salt was the big nutritional bad guy in the American diet, linked to hypertension, heart disease and stroke.
Then waistlines expanded and expanded some more, and the focus shifted.
Now, aware that Americans' salt consumption has risen by 50 percent over the past 40 years largely because of an increased reliance on a diet of processed and restaurant foods, public health experts and politicians are attempting to put the spotlight back on salt and its harmful health effects.
Last month, New York City Mayor Michael Bloomberg asked restaurants and foodmakers to consider voluntarily reducing the salt content in their foods by 25 percent over five years. A few days later, San Francisco Mayor Gavin Newsom, who suggested last fall that the city find a way to scale back sugar consumption, said he was looking into Bloomberg's proposal, too.
Meanwhile, a UCSF doctor released a study suggesting that regulating the salt content in foods could save up to $24 billion a year in health care costs.
"We're living in such a high-salt environment now. It requires a public health approach to reducing salt rather than an individual approach," said Dr. Kirsten Bibbins- Domingo, co-director of UCSF's Center for Vulnerable Populations at San Francisco General Hospital and lead author of the salt study.
"Salt was one of those things we put on the back burner and ignored for a while," she said. "But we're recognizing that reducing salt by even a small amount will have a widespread beneficial effect."
Good and bad of salt
Salt is a dietary mineral made up mostly of sodium, which the body needs in small amounts. It maintains the proper balance of fluids in the body, for one thing. But it's easy to get too much sodium, especially for people who already have high blood pressure.
Black people and people older than 50 tend to be particularly sensitive to too much sodium. Public health experts say 50 to 70 percent of Americans should be controlling their sodium intake and keeping it below 2,300 milligrams, or about a teaspoon of salt, a day.
Doctors have known about the relationship between sodium and high blood pressure for more than 100 years, which is why salt was one of the first major targets in campaigns to prevent heart disease. But more recent research has shown that other factors - especially obesity - play a larger role in causing high blood pressure and, in turn, heart disease and stroke.
Losing 20 pounds, for example, can lower systolic blood pressure by 15 to 20 points, research has shown. Americans consume an average of about 3,400 milligrams - or roughly a teaspoon and a half - of salt a day, but cutting sodium to the recommended maximum of 2,300 milligrams can shave two to eight points off the systolic blood pressure.
With that in mind, it makes some sense to focus on helping people lose weight - by cutting out trans fats and scaling back carbohydrates - rather than reducing their salt intake, said Eric Hernandez, a registered dietitian with the Community Health Resource Center, a nonprofit affiliate of California Pacific Medical Center.
"In the hierarchy of nutrition and risky foods, there are others ahead of salt," Hernandez said.
Ironically, Hernandez pointed out, the relatively recent focus on weight loss has probably contributed to people increasing the amount of salt they eat, especially in the form of premade meals designed to be low-fat and low-calorie. When food manufacturers take out the fat, they often add salt to make them taste better.