Americans consume, depending on which study you look at, an average of 3,000 to 4,000 milligrams of sodium per day, significantly higher than the 2,300 mg limit the government recommends for a healthy person, and more than double the 1,500 mg target advised for high-risk populations, which include people older than 50, African-Americans, and anyone with high blood pressure, diabetes or chronic kidney disease.
Lack of concern and awareness are the primary reasons behind the high sodium intake, according to a survey done this year by the nonprofit International Food Information Council. Though 83 percent of Americans believe certain people should be concerned with their sodium intake, just 42 percent are concerned about their own consumption and 62 percent are unaware that sodium guidelines even exist.
We ingest much of our sodium without realizing it. Seventy-seven percent of our sodium consumption comes from processed and restaurant foods.
The American Public Health Association this month called on the Food and Drug Administration to start regulating sodium in the food supply within a year, with the goal of reducing it by 75 percent within 10 years. It follows a similar regulatory call to action last year by the Institute of Medicine, an influential medical advisory group that is part of the National Academy of Sciences, which called voluntary efforts at sodium reduction a failure.
Yet some studies question whether that's such a good idea. This month a review of 167 studies published in the American Journal of Hypertension concluded that research does not support cutting sodium has population-wide benefit, as it reduces blood pressure by less than 1 percent in Caucasians with normal blood pressure and actually increases cholesterol, triglycerides and some hormones. One headline this summer in the popular science magazine Scientific American declared: "It's Time to End the War on Salt."
Though some hope blanket recommendations will stem the high sodium tide wrought by processed food and obesity, the public's ambivalence may reflect long-standing controversy on how much sodium is too much, how much it affects blood pressure, and whether it's wise to set guidelines for the entire population when individuals' response to sodium varies.
What we know
Sodium, an element we get primarily through salt (a mineral made up of 40 percent sodium and 60 percent chloride), is essential in our bodies for regulating blood volume, promoting nutrients across cell membranes and managing muscle contractions. When healthy people have too much, the excess is filtered out through urination.
Studies have shown reducing sodium can reduce blood pressure — which, when it's too high, raises the risk of coronary heart disease, the leading cause of death in the U.S., and stroke, heart failure and chronic kidney disease.
About 30 percent of Americans have high blood pressure, considered to be at 140 over 90 millimeters of mercury, or mmHg, and above, and another third are pre-high blood pressure, defined as lower than 140 over 90 mmHg but higher than 120 over 80 mmHg, according to the CDC. Because blood pressure rises as we age, some 90 percent of Americans eventually develop high blood pressure.
The FDA, which this month hosted a public meeting on the subject, has not made any final decisions in terms of regulatory action limiting sodium in food, a spokeswoman said.
The American Heart Association advocates that 70 percent of us should be aiming to consume 1,500 mg a day of sodium, which also is the amount the Institute of Medicine says is needed to adequately meet the average active person's salt needs (you need more if you're a competitive athlete or work in a hot environment).
For young, healthy people with normal blood pressure, "the data is not strong" to suggest that consuming a high-sodium diet now leads to higher blood pressure later in life, said Dr. Gordon Tomaselli, president of the American Heart Association and chief of cardiology at Johns Hopkins Medical Center. Still, if eating less sodium leads to modest reductions in blood pressure in people without high blood pressure, it's good for heart health, he said.
"The best blood pressure for anyone is the lowest blood pressure you can get without symptoms," Tomaselli said. If blood pressure gets too low, symptoms could include dizziness, nausea and fatigue.
Some researchers say that reducing sodium doesn't offer a significant enough blood pressure drop to warrant a populationwide guideline, and it doesn't have the same effect in everyone.
Dr. John Laragh, director of the cardiovascular center at New York-Presbyterian Hospital/Weill Cornell Medical Center, said reducing sodium is a worthy treatment tool for specific hypertensive patients, but he believes only 40 percent of high blood pressure is salt-related. The other 60 percent is caused by renin, a hormone secreted by the kidneys that helps regulate blood pressure. So 60 percent
of hypertensives won't respond to sodium reduction, and might even respond poorly, as low-sodium can cause renin to spike and, ironically, raise blood pressure.