New research shows that for the vast majority of individuals, sodium consumption does not increase health risks except for those who eat more than five grams a day, the equivalent of 2.5 teaspoons of salt.
Fewer than five per cent of individuals in developed countries exceed that level.
The large, international study also shows that even for those individuals there is good news. Any health risk of sodium intake is virtually eliminated if people improve their diet quality by adding fruits, vegetables, dairy foods, potatoes, and other potassium rich foods.
The research, published today in The Lancet, is by scientists of the Population Health Research Institute (PHRI) of McMaster University and Hamilton Health Sciences, along with their research colleagues from 21 countries.
The study followed 94,000 people, aged 35 to 70, for an average of eight years in communities from18 countries around the world and found there an associated risk of cardiovascular disease and strokes only where the average intake is greater than five grams of sodium a day.
China is the only country in their study where 80 per cent of communities have a sodium intake of more than five grams a day. In the other countries, the majority of the communities had an average sodium consumption of 3 to 5 grams a day (equivalent to 1.5 to 2.5 teaspoons of salt).
"The World Health Organization recommends consumption of less than two grams of sodium -- that's one teaspoon of salt -- a day as a preventative measure against cardiovascular disease, but there is little evidence in terms of improved health outcomes that individuals ever achieve at such a low level," said Andrew Mente, first author of the study and a PHRI researcher.
He added that the American Heart Association recommends even less -- 1.5 grams of sodium a day for individuals at risk of heart disease.
"Only in the communities with the most sodium intake -- those over five grams a day of sodium – which is mainly in China, did we find a direct link between sodium intake and major cardiovascular events like heart attack and stroke.
"In communities that consumed less than five grams of sodium a day, the opposite was the case. Sodium consumption was inversely associated with myocardial infarction or heart attacks and total mortality, and no increase in stroke."
Mente added: "We found all major cardiovascular problems, including death, decreased in communities and countries where there is an increased consumption of potassium which is found in foods such as fruits, vegetables, dairy foods, potatoes and nuts and beans."
The information for the research article came from the ongoing, international Prospective Urban Rural Epidemiology (PURE) study run by the PHRI. Mente is also an associate professor of the Department of Health Research Methods, Evidence and Impact at McMaster University.
Most previous studies relating sodium intake to heart disease and stroke were based on individual-level information, said Martin O'Donnell, co-author of the report, a PHRI researcher and an associate clinical professor of medicine at McMaster.
"Public health strategies should be based on best evidence. Our findings demonstrate that community-level interventions to reduce sodium intake should target communities with high sodium consumption, and should be embedded within approaches to improve overall dietary quality.
"There is no convincing evidence that people with moderate or average sodium intake need to reduce their sodium intake for prevention of heart disease and stroke," said O'Donnell.
Besides Canada, this research paper involved individual and community information from the countries of Argentina, Bangladesh, Brazil, Chile, China, Columbia, India, Iran, Malaysia, occupied Palestinian territory, Pakistan, Philippines, Poland, Saudi Arabia, South Africa, Sweden, Tanzania, Turkey, United Arab Emirates, and Zimbabwe.
The study was funded by PHRI, Canadian Institutes of Health Research, Heart and Stroke Foundation of Ontario, European Research Council, as well as unrestricted grants from several pharmaceutical companies, and grants from health agencies or ministries of 18 countries.
Read the study here.