Salt isn’t as bad for your health as you think, unless you’re eating very high amounts each day, suggests a new study.
These results put the study’s authors at odds with years of public health messages trying to convince people to go “low sodium” in order to lower their blood pressure and reduce their risk of stroke and other health problems.
Sodium intake sweet spot
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.
Concerns over study results
Sodium isn’t the only nutrient that affects heart health.
Researchers also found that communities with higher levels of potassium intake had lower rates of stroke, heart disease, and death.
Potassium is found in foods such as sweet potatoes, leafy greens, tomatoes, white beans, kidney beans, yogurt, oranges, bananas, and cantaloupe.
Eating more of these may offset the effects of sodium in the diet.
“Much of the attention was on sodium,” said Gupta, “but seemingly the most robust results were those demonstrating the seemingly protective effect of higher potassium intake.”
Gupta added that from a public health perspective, “targeting the communities with the highest sodium consumption first makes sense. However, in clinical practice we most often make recommendations for the individual patient sitting in front of us.”
The research drew some of the same criticisms as a 2016 study by the same group of researchers, with some scientists calling the earlier study “bad science.”
The Guardian reports that the main complaint was that the study estimated sodium intake using a single morning urine sample, rather than more accurate sampling over 24 hours.
Also concerning was the inclusion of people who are ill in the study. If they die during the study, it may have more to do with their current illness than their sodium intake.
Gupta called for “further research on personalizing dietary sodium intake recommendations.”
The Centers for Disease Control and Prevention reports that about half of the sodium in Americans’ diets comes from processed or packaged foods such as breads, sandwiches, soups, snack foods, and cold cut meats.
Restaurant meals are also a big source of sodium. At the extreme end is the Cheesecake Factory’s Breakfast Burrito, which contains 4.6 gm of sodium, about twice the recommended daily allowance, according to the Center for Science in the Public Interest.
To minimize sodium in the diet, the American Heart Association recommends that people read food labels closely, limit salt added to home-prepared meals, and choose low-sodium options when dining out.