Studies Question Need to Watch Your Salt
By Brenda Goodman, MA
Reviewed by Brunilda Nazario, MD
Aug. 14, 2014 -- Worried about your salt intake? You may not need to be.
A trio of studies has given us a clearer picture of the relationship between salt and heart health.
Although we've been told for years to watch our salt, experts say new research questions that.
"You don't need to be freaking out about salt," says Suzanne Oparil, MD, a cardiologist and blood pressure expert at the University of Alabama at Birmingham.
Why? Two of the new studies found that for most people -- especially those younger than 55 and those who don't have high blood pressure -- there's a sweet spot for sodium in the range of 3,000 to 6,000 milligrams a day. As long as sodium intake stays in that range, there seems to be little impact on the heart or blood pressure, those studies found.
In comparison, a teaspoon of salt contains about 2,300 milligrams of sodium.
And the good news is that most of us are already there. According to the CDC, the average American gets about 3,400 milligrams a day. And 95% of Americans get less than 6,000 milligrams a day, according to the U.S. government.
Those two studies gauged the amount of sodium eaten by more than 100,000 people in 17 different countries by measuring the sodium in their urine. Researchers then looked at their blood pressure and the number of heart attacks, strokes, cases of heart failure, and deaths they had over the next 4 years.
A third study combined the results of more than 200 previous studies of sodium from around the world. The study researchers then compared average intakes to rates of heart disease and high blood pressure.
That study found higher rates of heart problems and high blood pressure linked to sodium, but experts say the conclusions are based on estimations rather than direct measurements, so the results should be viewed with caution. "They didn't really study anything, they just put together the results of a large number of observational studies and surveys. They maneuvered the data," Oparil says.
Findings Question Current Advice on Salt
The idea that many of us don't need to worry about how much salt we eat is contrary to years of efforts by public health officials to get people to eat less salt.
For that reason, Oparil says she expects the studies, which followed more than 100,000 people for nearly 4 years, will face plenty of criticism.
"A lot of the experts have a strong vested interest in the 'salt hypothesis,'" she says, or the idea that higher levels of salt in the diet lead to higher blood pressure and more heart attacks and strokes.
The new studies aren't in conflict with the idea that salt raises blood pressure.
"We're not challenging the blood pressure contention here. We're seeing it, too. We're seeing a clear association between sodium intake and blood pressure," says Martin O'Donnell, an associate professor at McMaster University in Canada who was an author of two of the studies.
But at moderate levels, less than 6,000 milligrams a day, the effect of salt on blood pressure appears to be small. Eating less, he says, doesn't seem to prevent heart attacks, strokes, or deaths.
U.S. dietary guidelines recommend that most Americans limit their salt intake to 2,300 milligrams a day. People with health concerns like high blood pressure, diabetes, or kidney disease are told to get even less, about 1,500 milligrams a day.
The American Heart Association's advice is even more conservative. They say everybody should eat less than 1,500 milligrams a day (unless they lose a lot of salt through sweat, like athletes and people who work in the heat.)
But the new studies found that very few -- less than 1% -- of people around the world are hitting those goals.
What's more, the studies found that people with low sodium intakes appeared to be at higher risk for heart attacks, strokes, and death than people who were getting a moderate amount of salt in their diets.
Experts aren't sure why low-salt diets may harm the heart.
"Making recommendations like this to everybody needs to be backed up by very robust data. What our data and other data are showing, consistent with the recommendation last year from the Institute of Medicine, is that there's a lot of uncertainty," O'Donnell says.
The 2013 report from the Institute of Medicine also concluded there wasn't enough evidence to support lowering sodium below 2,300 milligrams per day, and experts declined to identify a "healthy" range for sodium.
"Should we be making such a sweeping recommendation at a population level where there is so much uncertainty?" O'Donnell says.
O'Donnell says there are still many other important questions to answer about sodium, like whether men and women need different amounts, and whether the climate you live in changes your body's sodium requirements.
He says his team hopes to have answers on some of those within the next few years.
For its part, the American Heart Association sees no reason to change its advice.
"There are significant limitations here. We don't have confidence that there really is a signal of harm with a reduction of sodium in the diet," says Elliott Antman, MD, president of the American Heart Association.
"We are not moved by these studies with respect to our position," Antman says. "We maintain our position that there should be a lower sodium content in the American diet."
Some Still Need to Watch Salt
The advice to breathe easy on salt doesn't apply to everyone, however.
"If you are older, over age 55 or 60, if you have hypertension, or if you are obese -- any one of those things -- you need to take a look at what you're eating and try to reduce your intake of prepared foods and obviously things that have a lot of salt in them," Oparil says.
All three studies found stronger links between sodium and blood pressure in people who were older and those who already had high blood pressure.
Plus, Oparil says people who are obese become much more sensitive to salt.
She tells her patients who have high blood pressure to cut back on their restaurant meals and cook more at home. The salt that is added to prepared foods has a greater impact on your daily sodium than what's added with the shaker, she says.
She tells her patients who are overweight or obese to focus on losing weight. In her experience, weight loss has bigger effects on blood pressure than drastically cutting sodium.
And finally, she advises patients to get more potassium.
"If you eat a lot of potassium-containing foods, you greatly blunt the blood-pressure-elevating effect of sodium," she says.
The new studies also found a link between higher potassium levels and lower blood pressure. Each additional 1,000 milligrams of daily potassium was tied to a decrease of about 1 point in systolic blood pressure (the top number in blood pressure).
How much potassium do you need? For adults, Institute of Medicine recommends 4,700 milligrams of potassium a day to lower blood pressure, blunt the effects of salt, and lower the risk of kidney stones and bone loss. But most of us are only getting about half that much.
To get more of this valuable mineral in your diet, concentrate on eating more dark, leafy greens, beans, and low-fat dairy products.
Here are 12 other high-potassium standouts to add to the menu:
SOURCES: Suzanne Oparil, MD, professor of medicine and physiology, University of Alabama at Birmingham. Martin O'Donnell, MB, PhD, associate clinical professor at McMaster University, Hamilton, Canada; professor, National University of Ireland-Galway.Elliott Antman, MD, professor of medicine, Harvard Medical School, Boston; president, American Heart Association. New England Journal of Medicine, Aug. 14, 2014. News release, Institute of Medicine. Institute of Medicine, Dietary Reference Intakes: "Water, Potassium, Sodium, Chloride and Sulfate."