21 Aug 2014 Another study counters salt reduction guidelines
A long-running debate over the merits of eating less salt has again escalated when one of the most comprehensive studies yet suggested cutting back on sodium too much actually poses health hazards.
Current guidelines from US government agencies, the WHO, the American Heart Association (AHA) and other groups set daily dietary sodium targets between 1,500 and 2,300mg or lower, well below the average US daily consumption of about 3,400mg.
The new study, which tracked more than 100,000 people from 17 countries over an average of more than three years, found that those who consumed fewer than 3,000mg of sodium a day had a 27% higher risk of death or a serious event such as a heart attack or stroke in that period than those whose intake was estimated at 3,000 to 6,000mg. Risk of death or other major events increased with intake above 6,000mg.
The findings, published in the New England Journal of Medicine, are the latest to challenge the benefit of aggressively low sodium targets—especially for generally healthy people. Last year, a report from the Institute of Medicine, which advises Congress on health issues, didn’t find evidence that cutting sodium intake below 2,300mg reduced risk of cardiovascular disease.
The new report has shortcomings, and as an observational study it found only an association, not a causative effect, between very low sodium and cardiovascular risk. Still, it spurred calls to reconsider the targets.
This “adds a pretty big weight on the side that low salt intake is associated with harm,” said Suzanne Oparil, professor of medicine at the University of Alabama at Birmingham and an expert on high blood pressure. Without evidence from randomised trials to back them up, the low-sodium targets are “questionable health policy,” she said. Dr Oparil was author of an editorial that accompanied the findings.
“It’s about time that major groups who are making recommendations on sodium take a more measured approach,” said Salim Yusuf of the Population Health Research Institute, or PHRI, at McMaster University in Ontario and senior author of two papers on the new study.
The AHA, a strong proponent of the low-sodium targets, isn’t persuaded. Certain methods in the study, including how dietary sodium was estimated from urine samples, call “into question our ability to have confidence” in the findings, said Elliott Antman, AHA president.
“We hold fast to the recommendations that there is a need to reduce sodium intake in the diet,” said Dr Antman, a cardiologist at Brigham and Women’s Hospital in Boston.
The FDA said it intends to review the studies. The agency said it “continues to recognise the need to reduce the sodium content of the food supply” to help reduce sodium intake.
Participants in the study, known as the Prospective Urban Rural Epidemiology study, or Pure, consumed an average of 4,930mg of sodium a day, based on estimates derived from a single urine sample obtained when they enrolled in the study. The research was funded through a variety of public, private and corporate sources, according to PHRI.
Researchers followed participants for an average of 3.7 years. They found that 4.3% of those who consumed less than 3,000mg of sodium either died or suffered a heart attack or stroke or developed heart failure in that time, versus 3.1% with intake between 3,000 and 6,000mg. The percentage rose to 3.2% at levels above 6,000mg and to 3.3% above 7,000mg….
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Journal reference:
Oparil , Suzanne , (2014) Low Sodium Intake — Cardiovascular Health Benefit or Risk?. New England Journal of Medicine 371:7, 677-679
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