Nearly 100,000 lives could be saved in the United States every year if people reduced their salt consumption by just half a teaspoon a day, comparable to the benefits of national efforts to reduce smoking, obesity and cholesterol levels, according to a new study.
Consuming half a teaspoon less of salt daily - the equivalent of 1,200 milligrams of sodium - could also prevent up to 120,000 new cases of coronary heart disease, 66,000 strokes and 99,000 heart attacks, according to the study, published by the New England Journal of Medicine online Wednesday.
The savings would also extend to the health-care system, reducing costs related to hypertension and other health problems by between $10-billion and $24-billion (U.S.) a year.
"The numbers are huge," said Kirsten Bibbins-Domingo, lead author of the study, associate professor of medicine and epidemiology at the University of California, San Francisco and co-director of the UCSF Center for Vulnerable Populations at the San Francisco General Hospital.
Although the study focused on the U.S. population, it has implications for Canadians, who also consume dangerously high amounts of sodium. The recommend daily intake for adults up to age 50 is 1,500 mg, while the upper limit is 2,300 mg. But the average intake is about 3,100 mg, which many consider a conservative estimate, while in the U.S., it's about 3,400 mg.
"This again just highlights the increasing amount of evidence that we need to, as a society, reduce the amount of salt that's added to food," said Norm Campbell, Canadian research chair in hypertension prevention and control. "That's really the issue at the end of the day."
Dr. Bibbins-Domingo and her colleagues used a sophisticated computer simulation program called the Coronary Heart Disease Policy Model to provide an accurate estimate of the benefits of population-wide sodium reduction. The model allows researchers to use census data and government information on cardiovascular risk factors and other issues affecting the population in order to measure the impact of a 1,200-mg sodium reduction across the population.
Dr. Campbell did a similar, although by his description, less sophisticated, study published in the Canadian Journal of Cardiology in 2008, which found that reducing sodium intake to recommended levels would prevent up to 17,000 cases of stroke, heart attack or heart failure a year in Canada.
While it's impossible for researchers to predict exactly how many people could avoid a heart attack, stroke or death as a result of lower salt consumption, the findings provide an accurate estimate of the major effect sodium reduction could have on the population, said Kevin Willis, director of partnerships at the Canadian Stroke Network.
"I would agree that it is very difficult to accurately model the effects, and this study has been done very carefully using very sophisticated modelling techniques, but just about anybody could predict the magnitude of this effect doing back-of-the-envelope calculations because it is so significant."
Public pressure is growing in Canada and the U.S. for governments to take action on salt consumption, which many physicians say is one of the most pressing public health issues.
Earlier this month, New York released guidelines that call for restaurant meals and packaged foods to cut sodium by 25 per cent over the next five years. It's a completely voluntary move, but city officials say they believe the food industry will get on board because of the growing consumer appetite for lower-sodium products.
Canada's federally-appointed working group is in the process of deciding on sodium-reduction targets for different food categories, and how a national reduction plan should be implemented. It expects to finish its work some time this summer, but has come under sharp criticism from some federal MPs and health organizations for its slow movement and failure to create a plan more than two years after it was created.
Group members participated in a teleconference on Wednesday, saying that the pace of discussions has heated up in recent months, particularly after a major series by The Globe and Mail on the country's serious sodium problem.