Americans are repeatedly told to cut back on salt to reduce the risk of heart disease. But there are new questions being raised about the possible risks of reducing sodium too much.
So, how low should we go? Currently, the government recommends that Americans should aim for 2,300 milligrams per day. And people older than 50, as well as those with high blood pressure, diabetes or kidney disease are advised to reduce sodium even further, down to 1,500 mg per day.
But a panel of experts convened by the Institute of Medicine concludes in a new report that "the evidence on direct health outcomes does not support recommendations to lower sodium intake ... to or even below 1,500 mg per day."
Why? We asked the committee chairman, Brian Strom, a dean and professor of public health at the University of Pennsylvania, to summarize the panel's findings for us. "The net conclusion is that people who are eating too much sodium should lower their sodium, but it is possible that if you lower it too much you may do harm."
Strom says a lot more research is needed to better understand how ultra-low-sodium diets may be beneficial or harmful. Strom pointed to an Italian study of people with congestive heart failure as an example of research that has hinted that diets too low in sodium may be problematic for certain people.
"The people on the low-sodium diet actually did worse [compared to those on medium-sodium diets]," says Strom. "They had more hospital re-admissions and they had a higher mortality rate." He says it's unclear if the results would be the same for Americans with congestive heart failure, since treatments here are different than they are in Italy. But, he says, the findings raise questions.
The American Heart Association, which recommends a low-sodium (1,500 mg) diet for all Americans, released a statement stating that it disagrees with the key findings of the new report.
And some preventive health experts are critical, too. The World Health Organization has concluded that elevated blood pressure is the leading cause of preventable death, which suggests that staving off high blood pressure with low-sodium diets is an important strategy.
"Sodium reduction remains a critically important component of public health efforts designed to ... prevent cardiovascular disease," Lawrence Appel of Johns Hopkins University writes in an email.
Appel points out that the studies that suggest that low-sodium diets are harmful tend to focus on "sick populations in which illness leads to low sodium intake rather than the reverse."
Some groups of Americans, including older adults and African-Americans, are especially sensitive to the blood-pressure lowering effects of cutting sodium, Appel says. So the strategy of aiming for low-salt diets has "tremendous potential to reduce racial disparities in blood pressure-related cardiovascular disease."
The bottom line, according to Bonnie Liebman, director of nutrition for the Center for Science in the Public Interest, is that Americans are eating way too much salt, on average about 3,400 milligrams a day.
"And we know that much is harmful," she says. "It increases blood pressure, which increases the risk of heart attack and stroke."
And she says focusing on the potential risks of a very-low-sodium diet distracts from the more important conversation about how to get Americans to start consuming less.
To better understand just how much salt is found in the typical lunch out, I met Liebman at a food court.
Our first stop was McDonalds, where it turns out burgers have about twice as much salt as the fries: 1,000 mg, and up to 2,000 if you get the Angus bacon burger, Liebman says.
Put the burger and fries together and you've already reached the recommended daily sodium intake. Liebman says it's a similar story at every chain, from Subway to Chipotle to Pizzeria Uno. (McDonalds has pledged to reduce sodium 15 percent across its menu by 2015.)
So even though the new study raises questions about potential harms of ultra-low-sodium diets, with a food supply like ours, most of us consume way too much salt, not too little.
STEVE INSKEEP, HOST:
Sometimes too much of a good thing is bad. Sometimes too little of a bad thing is not so great either. Most of us have heard the dietary advice to cut back on salt. And a new report out today affirms that modest reductions are a good idea, but how low do we need to go? Experts conclude that cutting sodium too much is risky.
NPR's Allison Aubrey reports.
ALLISON AUBREY, BYLINE: For years, people over the age of 50, as well as those who have elevated blood pressure or other risk factors for heart disease, have been told to aim for a very low sodium diet - down to 1500 milligrams per day. That's less than a teaspoon. But now, a panel of experts convened by the Institute of Medicine - made up of physicians, researchers and nutrition scientists - is questioning whether a diet that low in sodium is beneficial.
Brian Strom of the University of Pennsylvania chaired the panel.
DR. BRIAN STROM: The net conclusion is that people who are eating too much sodium should lower their sodium, but it is possible that if you lower it too much you might do harm.
AUBREY: Strom says that the panel reviewed a lot of studies evaluating the relationship between sodium and health outcomes. And he says some research from Italy stands out, when it comes to suggesting that ultra-low-sodium diets may be harmful. In the Italian study, people with congestive heart failure were put on either a low-sodium diet or a medium-sodium diet.
STROM: The people who were on the low-sodium diet actually did worse. They had more hospital re-admissions and they had a higher mortality rate.
AUBREY: Strom says the Italian study is not entirely conclusive, but the panel agreed that studies like this raise questions about whether current low-sodium recommendations should be moderated.
Now groups such as the American Heart Association, which recommends a low-sodium diet for all Americans, says it disagrees with the key findings of the new report.
DR. STEPHEN HAVAS: I think it's very unfortunate and it's going to confuse the American public.
AUBREY: That's Stephen Havas, a preventive medicine doctor from Northwestern University. He points out that most Americans are consuming excessive amounts of salt, way more than the experts are talking about here. He says quibbling over whether the ideal intake is 2300 milligrams or 1500 milligrams distracts us from the more important conversation, about how to get Americans to start consuming just a little less. Right now, the typical American consumes more than 3400 milligrams a day
HAVAS: We have lots of evidence showing that the more sodium people consume, the more likely it is that they will develop high blood pressure.
AUBREY: And this matters.
BONNIE LIEBMAN: I don't think people have no idea how much sodium they're eating.
AUBREY: To better understand just how much salt is found in the typical lunch out, I met nutrition advocate Bonnie Liebman at a food court. Our first stop was McDonald's, where I was surprised to learn that the French fries are not the saltiest item on the menu. Turns out a Quarter Pounder with cheese has more than three times as much salt as a medium fry.
LIEBMAN: Most burgers have a thousand milligrams. You can get up to 2,000 if you get the Angus burger with bacon.
AUBREY: Put the burger and fries together and you've already reached the recommended daily sodium intake.
Liebman says it's important not to pick on fast food. McDonald's, after all, has pledged to reduce sodium 15 percent across its menu by 2015. And as we stroll down the food court - from Subway to Chipotle to Pizzeria Uno - Liebman says it's a similar story at every chain.
LIEBMAN: Expect at least a thousand milligrams in a sandwich. It doesn't matter if it comes from Panera or Au Bon Pain.
AUBREY: So even though the new report raises questions about potential harms of ultra-low-sodium diet, with a food supply like ours, most of us should be concerned with eating too much salt, not too little.
Allison Aubrey, NPR News. Transcript provided by NPR, Copyright NPR.