Although most experts agree that Americans consume too much sodium and that lowering sodium is good for your heart, the debate over the specifics continue in a series of expert commentaries and an editorial published in the American Journal of Hypertension.
The commentaries were based on a May 2013 report by the Institute of Medicine, which found that reducing sodium intakes from current levels was important and that higher levels of sodium intake led to a higher risk of heart disease. However, the report said there wasn’t enough evidence that lowering daily sodium to less than 2,300 milligrams daily led to less heart disease, stroke and a reduced risk of death.
The Institute of Medicine looked at research that assessed the relationship between excessive sodium consumption and cardiovascular disease “outcomes” such as heart attacks and deaths.
Daily sodium consumption
One of the key issues in the debate is how much to limit daily sodium intake.
The average consumption of sodium per day in the U.S. is 3,400 milligrams, more than twice the American Heart Association’s recommendation of 1,500 milligrams a day.
The Dietary Guidelines for Americans recommend less than 2,300 milligrams a day for all Americans and 1,500 milligrams a day for groups that are particularly responsive to the blood-pressure-raising effects of sodium, including: African Americans; individuals with hypertension, diabetes, or chronic kidney disease; and individuals ages 51 and older. The World Health Organization recommends less than 2,000 milligrams a day for adults and lower levels for children.
Despite the lack of consensus on an exact number, there is agreement within the public health community that current American sodium intake is considerably higher than the upper level of any public health recommendation and that a reduction in intake is critical.
Use of blood pressure research
The foundation of the American Heart Association’s recommendation is research linking high sodium consumption to high blood pressure and cardiovascular disease. It also showed lowering sodium can prevent and treat hypertension in order to reduce heart attacks and strokes.
The American Heart Association said in a statement that the Institute of Medicine report was incomplete because it excluded research showing that lowering sodium could reduce blood pressure.
“The research that the IOM partially based their conclusions on showed inconsistencies in the relationship between sodium intake and health outcomes. Yet these studies were not designed to assess the impact of various levels of sodium intake on cardiovascular health,” said Elliott Antman, M.D., a spokesperson for the American Heart Association, a cardiologist at the Brigham and Women’s Hospital and professor of medicine at Harvard Medical School.
“Numerous trials, including well-controlled feeding studies, have documented that the relationship of sodium intake to BP (blood pressure) is direct and progressive,” agreed Lawrence Appel, M.D., director of the Welch Center for Prevention, Epidemiology and Clinical Research at Johns Hopkins University.
The World Health Organization’s 2012 sodium intake guidelines for adults and children, determined that blood pressure could be a suitable proxy indicator for risk of heart disease and stroke.
However, some disagree with using blood pressure as a “surrogate” or indirect link between sodium intake and heart attacks, stroke or heart-disease related death.
“This change in focus from surrogate outcomes to [cardiovascular disease] events is consistent with other guidelines and prompted by results of recent clinical trials where changes in surrogates (e.g., BP, glucose) do not always translate into anticipated changes in [cardiovascular disease],” said Salim Yusuf, M.D., professor of cardiology and clinical epidemiology & biostatistics at McMaster University.
Don’t lower sodium
Some of the commentators believe there’s not enough scientific evidence for Americans to lower their sodium intake at all.
Until healthy limits are set, “…most Americans may be wise to maintain their sodium consumption pattern that, in any event, appears impervious to change,” said Michael H. Alderman, M.D., editor of the American Journal of Hypertension.
Others suggest that because most sodium intake worldwide falls into a range of 2,600-4800 milligrams per day, our bodies are programmed to need that much salt to function.
“Saying that most people are consuming more than the recommended levels of sodium does not justify giving up on our sodium reduction efforts,” Antman said.
The CDC, which commissioned the Institute of Medicine report, agrees with the AHA and other organizations that believe Americans would benefit from reducing their current level of sodium intake.
Lowering sodium in the food supply
More than 75 percent of the sodium Americans eat comes from salt added to processed and restaurant foods, which makes it difficult for consumers to choose and control how much sodium they consume. The AHA supports federal regulations that would limit the amount of sodium the food industry adds to foods.
Other experts support such measures.
“Although we concur with the IOM committee on the need for additional research on the health effects of sodium, we firmly believe that evidence supporting population-wide reduction in sodium intake is compelling,” said Appel. “In this context, we urge policy makers to expand their efforts to lower population intake levels of sodium. Flawed evidence should not derail sound policy.”
“Given that sodium intake is high and that the benefit of lowering intake is well established, innovative policies and programs to lower population sodium intake should be pursued aggressively,” said Thomas A. Farley, M.D., commissioner of the New York City Department of Health and Mental Hygiene. “It is the shared responsibility of public health leaders, journalists, and government officials to get the message right: reducing sodium intake saves lives.”
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