A committee of experts commissioned by the Institute of Medicine at the request of the Centers for Disease Control and Prevention says there is no medical rationale for anyone to aim for sodium levels below 2,300 milligrams a day. That is far above the American Heart Assn.'s recommended maximum sodium intake of 1,500 milligrams a day.
The AHA level is purported to prevent heart attacks and strokes in those at risk, which includes people over 50, African-Americans and people with high blood pressure, diabetes or chronic kidney disease -- fully half the U.S. population. But the AHA says everyone should aim for no more than 1,500 milligrams a day. They are sticking to their guns, even in the face of the Institute of Medicine's new report.
But too-low sodium consumption may actually be harmful, according to the new data analysis. "As you go below the 2,300 mark, there is an absence of data in terms of benefit and there begin to be suggestions in subgroup populations about potential harms," Dr. Brian L. Strom, chairman of the committee and a professor of public health at the University of Pennsylvania, told the NYT. He said those possible harms actually include increased rates of heart attacks and an increased risk of death overall.
It has been proven that blood pressure can drop slightly when people eat less salt. Researchers have linked that fact to other studies that showed that higher blood pressure increases the risk of heart attacks and strokes. But the expert committee's recent analysis suggests that may be too simplistic a formulation.
Current U.S. dietary guidelines, based on a 2005 Institute of Medicine report, recommend that the general population aim for sodium levels of 1,500 to 2,300 milligrams a day. However, the average U.S. sodium consumption in the United States, and around the world, is about 3,400 milligrams a day. (Much of that comes from eating processed foods.)
The committee looked at salt research conducted since 2005. A 2008 study examined by the group found that congestive heart failure patients consuming a lower level of sodium had more than three times the number of hospital readmissions and more than twice as many deaths as those in the research group who consumed more salt.
A 2011 study that followed 28,800 subjects with high blood pressure for nearly five years found that the risks of heart attacks, strokes, congestive heart failure and death from heart disease increased significantly for those consuming more than 7,000 milligrams of sodium a day -- and for those consuming fewer than 3,000 milligrams of sodium daily.
Dr. Michael H. Alderman, a dietary sodium expert at Albert Einstein College of Medicine, told the NYT that as sodium levels plunge, triglyceride levels go up, insulin resistance increases, and the sympathetic nervous system becomes more active -- all of which can increase the risk of heart disease.
"What they have done is earth-shattering," Dr. Alderman told the NYT of the current study. He predicted their report "will have a big impact."
But Dr. Elliott Antman, an AHA spokesman, stressed to the NYT: "The American Heart Assn. is not changing its position." He said the group is rejecting the Institute of Medicine's conclusions because the studies on which they were based were flawed, and that everyone should still shoot for no more than 1,500 milligrams of sodium a day (which is a little over half a teaspoon).
The Institute of Medicine committee countered that the more recent studies it examined were careful and rigorous, and that "much of the new research found adverse effects on the lower end of the sodium scale and none showed a benefit from consuming very little salt," according to the NYT.
However, 2,300 milligrams a day appears to be the maximum level before blood pressure begins creeping up.
The government's dietary guidelines are currently being revised, which is why the expert committee looked at salt. New recommendations will be issued in 2015.
In the meantime, perhaps you don't have to keep quite such a close eye on your fries.