August 14, 2014
How Much Salt Is Too Much? And Is Too Little Also Bad? The Debate Continues In Three New Studies
redOrbit Staff & Wire Reports - Your Universe Online
Consuming too much salt has long been associated with risk of high blood pressure, but cutting back too much on sodium could also be hazardous to your health, according to research appearing in the latest edition of the New England Journal of Medicine (NEJM).
Lead author Dr. Martin O’Donnel of McMaster University in Hamilton, Ontario and his colleagues concluded in their study that consuming less than three grams of sodium per day increased the risk of death or major cardiovascular event by 27 percent versus those who consumed four to six grams each day, said Reuters reporter Gene Emery.
The study followed over 100,000 people from 17 different countries for an average of over three years, added Ron Winslow of the Wall Street Journal. The controversial findings “are the latest to challenge the benefit of aggressively low sodium targets – especially for generally healthy people.”
While the study “has shortcomings, and as an observational study it found only an association, not a causative effect, between very low sodium and cardiovascular risk,” Winslow said that it has “spurred calls to reconsider” recommendations from the American Heart Association and other health groups that most people consume between 1,500 and 2,300 milligrams (though US daily recommendations call for about 3,400 milligrams of salt).
NBC News reporters Judy Silverman and Lisa Tolin noted the study suggests that efforts to reduce the salt content in foods in order to help prevent high blood pressure and the cardiovascular ailments associated with it could be misguided. American Heart Association president Dr. Elliott Antman, however, has taken issue with the fact that sodium was measured through urine samples and noted that it might have ignored other potential health issues.
“We don’t know the diet the subjects who gave a urine specimen were eating and for how long they ate it after. It was one point in time, and the researchers followed them for 3.7 years and try to draw a relationship between one-spot urine and events that occurred over the next 3.7 years,” he told NBC News. Dr. Antman also noted that the study was too short to draw long-term conclusions, since it can take decades for cardiovascular disease to surface.
University of Alabama at Birmingham professor Dr. Suzanne Oparil, the author of an editorial accompanying the study, told reporters that the study, while flawed, provides evidence supporting the notion that consuming too little salt could be dangerous. She added that low-sodium targets are “questionable health policy” without evidence from randomized trials to support such claims.
A second study, also published this week in the New England Journal of Medicine, examined the effect of sodium on blood pressure and found that people consuming a moderate amount of salt did not benefit from reducing their consumption as those consuming higher amounts.
“Previously it was believed that the lower you go the better. What these studies show collectively is that there is an optimal level, and lower is not necessarily better,” McMaster University’s Dr. Andrew Mente, lead author of that study, told Reuters. “If people are eating a very high level of sodium and they reduce their intake, you get a large reduction in blood pressure. But if you're eating a moderate level of sodium – about what most North Americans eat – and you reduce it to a lower level, you're not really getting much in return as far as blood pressure reduction is concerned.”
A third NEJM paper, however, reported that one-tenth of all cardiovascular deaths occur to people consuming more than 2,000 milligrams of sodium per day. What that means, said lead author Dr. Dariush Mozaffarian of Tufts University, is that approximately 1.65 million people each year die as the result of heart disease and stroke directly caused by excessive sodium consumption.
Dr. Mozaffarian and his co-authors looked at data from 205 surveys of sodium intake representing approximately 75 percent of the global adult population, and discovered that the average sodium intake in 2010 was 3.95 grams per day – nearly double the daily recommendation set by the World Health Organization (WHO), according to Honor Whiteman of Medical News Today.
“All worldwide regions had sodium intakes above the WHO recommendation. These ranged from 2.18 g per day in sub-Saharan Africa to 5.51 g per day in Central Asia,” Whiteman said. “The researchers found that 4 out of 5 global deaths attributable to excess sodium intake occurred in low- and middle-income countries.”
“The bulk of the available evidence to date suggests that reduced sodium intake is associated with reduced blood pressure, which itself is associated with a reduction in cardiovascular events,” Dr. Antman said in a statement. “Along with improving overall diet, controlling weight, and increasing physical activity, lowering sodium intake is key to lowering blood pressure in the general population and improving blood pressure control in those with hypertension.”