The Prospective Urban Rural Epidemiology (PURE) study looked at average sodium intake in over 300 communities in 18 countries. This included more than 90,000 people followed for about eight years. Researchers found that the harmful effects of sodium — increased blood pressure and risk of stroke — only showed up in communities that consumed more than 5 grams (gm) of sodium per day on average, or the equivalent of 2.5 teaspoons of salt.
“Communities with the highest sodium intake had the strongest associations with higher blood pressure and risk of adverse outcomes,” said Dr. Deepak Gupta, an assistant professor of medicine in the Division of Cardiovascular Medicine at the Vanderbilt University Medical Center, who was not involved in the study.
The World Health Organization recommends that people lower their sodium intake below 2 gm per day.The American Heart Association sets the goal as 2.3 gm of sodium per day, with an ideal limit of 1.5 gm per day. Researchers say their results suggest that moderate sodium intake may be protective, while very high and very low amounts could be harmful.
“While low sodium intake does reduce blood pressure, at very low levels it may also have other effects, including adverse elevations of certain hormones associated with an increase in risk of death and cardiovascular diseases,” said study author Andrew Mente, PhD, a researcher at Population Health Research Institute and McMaster University in Canada, in a press release. However, Gupta pointed out that because the study looked at communities, not individuals, “it is difficult to extrapolate the results to any individual person.”
The WHO and AHA sodium intake guidelines are geared toward individuals rather than communities, which makes it difficult to know if those targets are right for communities.
“We do not have a direct comparison — either at the individual level or really at any of the community levels — as to whether moderate sodium consumption levels are associated with higher blood pressure or greater cardiovascular and mortality risk,” said Gupta. These targets are also not easy to meet.
“Fewer than 5 percent of the PURE study population had an estimated daily sodium intake level less than 2 gm per day,” said Gupta. Eighty percent of the communities in China exceeded 5 gm of sodium per day, possibly due to the frequent use of soy sauce.In other countries, 84 percent of communities consumed less than 5 gm of sodium per day.
The study was published August 11, 2018, in The Lancet.