July 11, 2011 -- A diet high in sodium and low in potassium increases the risk of death from heart disease and other causes, according to a new study.
"Americans who eat a diet high in sodium and low in potassium have a 50% increased risk of death from any cause and about about twice the risk of death from heart disease," says researcher Elena V. Kuklina, MD, PhD. She is a nutritional epidemiologist with the CDC division for heart disease and stroke prevention.
Morton Satin, vice president of science and research for the Salt Institute, disagrees with the study. "It's highly flawed and reveals more of this dogmatic anti-salt agenda."
Research about sodium and heart disease has produced conflicting results. Studies have shown that high sodium intake or low potassium intake is linked with a higher risk for high blood pressure, the researchers write. The link is stronger for potassium.
However, the research about a link between intake of sodium and potassium and getting or dying from cardiovascular disease has been less consistent.
The researchers decided to focus on the sodium-potassium ratio. Recent research has suggested the ratio may be more important in explaining the risk for high blood pressure or cardiovascular disease than either alone.
The study is published in the Archives of Internal Medicine.
Analyzing Diet and Heart Risk
Kuklina and her colleagues followed 12,267 U.S. adults. They participated in the Third National Health and Nutrition Examination Survey from 1988 to 1994. They answered questions about their diet and had physical exams.
None of those studied was on a reduced salt diet at the start. Anyone with a history of heart problems or stroke was excluded.
The researchers followed them for nearly 15 years. "Using death certificate data, we looked to see if they died and from what causes," Kuklina says.
During the follow-up, 2,270 people died, including 1,268 from cardiovascular disease.
A higher sodium-potassium ratio was associated with an increased risk of death from heart disease as well as other causes.
A sodium intake of 1,500 milligrams a day maximum and potassium intake of 4,700 milligrams a day is considered adequate under the Dietary Guidelines.
Higher sodium intake was linked to an increased risk of death from any cause. Those in the highest sodium group ''had a 73% higher risk of death from all causes," compared to those in the lowest sodium group, Kuklina says. Those in the highest group took in more than 5,000 milligrams a day. Those in the lowest consumed 2,176 milligrams a day.
Those who consumed 4,069 milligrams of potassium a day had a 49% lower risk of death from all causes compared to those who took in 1,793 milligrams a day, she says. The higher the potassium intake, the lower the risk of death from heart disease.
The researchers did not find a significant link between sodium intake and cardiovascular disease death by itself, they say. However, they do not think this undermines the relationship between sodium and high blood pressure, which they say is ''well established."
When they looked at the sodium-potassium ratio, they found those who had the worst ratio -- the highest sodium and lowest potassium -- had twice the risk of death from heart disease and a 50% increased risk of death from any cause during the follow-up.
Eat More Veggies?
Satin points to studies that have found salt reduction is often not linked with much blood pressure reduction.
In his view, paying attention to potassium intake may be enough. "The general public should ignore this study and focus on eating more salads, vegetables, and fruits," he says. He reasons that if people do that, the sodium will take care of itself.
Not so, says New York City Health Commissioner Thomas Farley, MD, MPH. He co-authored a commentary to accompany the study.
"Sodium and potassium were independently associated with mortality," he says. For that reason, he tells WebMD, people would have to lower sodium to reduce their risk of death from all causes.
One way to balance sodium and potassium, he says, is to avoid processed foods. He says as salt is added to processed foods, ''potassium tends to be washed out."
A sweet potato has about 694 milligrams of potassium. Eight ounces of yogurt has 531 milligrams, and a baked potato has 610 milligrams.