An international study of more than 100,000 people published Wednesday in the New England Journal of Medicine suggests that while there is a relationship between salt intake and high blood pressure, if you don’t already have high blood pressure and you’re not over 60 or eating way too much salt, salt won’t have much impact on your blood pressure.
In fact, people who consumed 3,000 to 6,000 milligrams per day had a lower risk of death and cardiovascular events than those who had more than 6,000 mg or less than 3,000 mg.
Most people consume between 3,000 and 6,000 mg of salt per day, but current federal guidelines recommend 1,500-2,300 milligrams per day, and the American Heart Association recommends just 1,500. In the new study, researchers found only 4 percent of respondents in 18 countries took in the recommended sodium levels.
The American Heart Association objected to the findings.
The implication is that efforts to get industry to lower salt content in food products in order to lower blood pressure and subsequent cardiovascular disease might be misguided. A recent report from the influential Institute of Medicine also indicated that low salt levels might be problematic.
“My personal bias is that there are so many more important things we could do,” said Dr. Suzanne Oparil, a cardiologist at the University of Alabama, Birmingham, who wrote the editorial accompanying the research. “A diet that reduces sugary drinks and approaches the Mediterranean diet will give you more benefit rather than regulating the salt aspect of the diet.”
Oparil noted that some people do consume huge amounts of salt - 10-12 grams - and those people tend to eat a lot of prepared food.
“There is no question that very large amounts of salt, especially if you are not eating potassium concomitantly, will drive blood pressure up,” Oparil added. “High blood pressure is associated with cardiovascular disease, but the correlation is strongest in people with high blood pressure and people who are older.”
Dr. Elliot Antman, president of the American Heart Association, noted that the studies are observational and so can’t show cause and effect or rule out other factors that would affect the findings, like if people with poor health had already reduced their salt intake to less than 3,000 milligrams. They also are concerned about how sodium was measured - through a urine sample.
“We don’t know the diet the subjects who gave a urine specimen were eating and for how long they ate it after,” Antman said. “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.”
The study was too short to draw long-term conclusions, Antman said, because cardiovascular disease can take decades to develop.
Oparil acknowledged some weaknesses in the study, but called it massive and said it “well might be the best data we’re going to get.” The researchers plan to extend the study to measure long-term effects.
The journal also published another study Wednesday that reached different conclusions. It used a modeling approach to combine results from a wide variety of studies, and estimates that 1.6 million deaths from cardiovascular causes in 2010 were linked to sodium consumption above 2,000 mg/day.
Antman called that finding important; Oparil said it included flawed data.
The AHA said it would continue to recommend lower sodium intake and urge the government to do the same, noting that previous research suggests that reduced sodium intake is associated with reduced blood pressure.
“Looking at the totality of the data, we consider it irresponsible not to make recommendations to lower salt content,” Antman said.
For Oparil, the advice is simple: “Try to eat natural foods. Cook your own food, as opposed to eating fast food and snack foods.”
“Japan, one of the highest salt consumers, has one of the longest lifespans,” Oparil noted.
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