The findings "certainly do not support the current recommendation to lower salt intake in the general population," study author Dr Jan Staessen, of the University of Leuven in Belgium, told Reuters Health.
Current salt guidelines are based on data from short-term studies of people who volunteered to be assigned to a low-salt or high-salt diet, Staessen said.
The US guidelines recommend that Americans consume less than 2,300mg of salt daily - 1,500mg in certain people who are more at risk for high blood pressure or heart disease.
Less salt not necessarily better health
While previous trials suggested a blood pressure benefit with lower salt intake, research has yet to show whether that translates into better overall heart health in the wider population.
The researchers used data from two different studies, incorporating a total of about 3,700 Europeans who had their salt consumption measured through urine samples at the start of the studies. Staessen and his colleagues broke the participants up into three groups: those with highest and lowest salt intakes, and those with average intake.
None of the participants had heart disease at the outset, and two thirds had normal blood pressure. They were followed for an average of 8 years, during which researchers determined how many of them were diagnosed with heart disease, and in a smaller group, how many got high blood pressure.
The findings are published in the Journal of the American Medical Association (JAMA).
No difference in heart risk
The chance of getting heart and blood vessel diseases did not differ in the three groups. However, participants with the lowest salt intake had the highest rate of death from heart disease during the follow up (4%), and people who ate the most salt had the lowest (less than 1%).
Across all three salt-intake groups, about one in four study participants who started out with normal blood pressure were diagnosed with high blood pressure during follow up.
The researchers did find that one measure of blood pressure, systolic blood pressure, increased as salt intake increased over time - but the change was very small, so it may not be important to health outcomes, Staessen said.
Reducing salt still a good idea
Reducing salt may still be a good idea for people who already have high blood pressure or who have had heart problems in the past, he added, but the study found no evidence that dietary salt causes those conditions to arise.
"It's clear that one should be very careful in advocating generalised reduction in sodium intake in the population at large," Staessen said. "There might be some benefits, but there might also be some adverse effects."
Dr Hillel Cohen, an epidemiologist at the Albert Einstein College of Medicine in New York, told Reuters Health that when restaurants or food companies put less salt in their products, they may put in other potentially harmful products to make up for the lost taste, or as preservatives.
Consumers shouldn't change their salt-eating behaviour based on the limited studies that have tried to determine the link between sodium and heart risks, added Cohen, who was not involved in the current research.
The authors caution that their analysis included only white Europeans, and so the results may not translate to people of other ethnicities. - (Genevra Pittman/Reuters Health, April 2011)
SOURCE: http://bit.ly/hwxtTL JAMA, online May 3, 2011.
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