Even modest reductions in salt intake can dramatically lower heart disease risk, new research shows.
In an extended follow-up of two rigorously designed trials, people who reduced their dietary sodium while participating in the studies saw 25 percent reductions in heart disease and stroke risk 10 to 15 years later, compared with people who ate their usual diets.
Most people in the intervention arm of the studies -- where participants reduced the sodium in their diet -- lowered their sodium intake by 25 percent to 30 percent, researcher Nancy Cook, ScD, of Brigham and Women's Hospital and Harvard Medical School, tells WebMD.
"This was not salt restriction, it was salt reduction," she says. "These people ate normal diets, but we taught them how to look out for hidden salt and avoid it."
The findings are the strongest evidence yet linking dietary salt intake to heart disease, Cook says. It is the first intervention trial to assess cardiovascular risk long term.
Participants were between the ages of 30 and 54 when recruited for the two salt-reduction studies, which were conducted between 1987 and 1995. All also had slightly elevated blood pressures, but none had heart disease at recruitment.
During the initial trials, roughly half of participants were taught to identify, select, and prepare low-salt foods and asked to reduce the salt in their diets. The rest were not asked to lower the salt in their diets. One study lasted for 18 months and the other study lasted for 36 to 48 months.
Ten to 15 years after the end of the original trials, participants in the intervention arms of the two studies were found to have lower cardiovascular risk and a slightly lower risk of death from all causes than participants who ate their usual diets.
"Americans consume much more sodium than is necessary, and it comes mostly from processed foods and the foods we eat in restaurants," Cook says, adding that initiatives aimed at lowering dietary sodium will have a bigger impact if they target the food industry and not individuals.
Calling for Change
Last summer, the American Medical Association (AMA) called for a minimum 50 percent reduction in sodium in processed foods, fast foods, and non-fast-food restaurant meals within a decade. The group also called on the FDA to work harder to educate consumers about the health risks associated with a high-sodium diet.
Texas cardiologist J. James Rohack, MD, who was on the AMA board that issued the directives, says 150,000 lives could be saved in the U.S. annually if everyone cut their sodium consumption in half.
Most people eat much more salt than they realize, he says, because restaurant meals and processed foods have replaced home cooking in the American diet. The American Heart Association recommends that healthy adults should not exceed 2,300 milligrams of sodium a day. This is equal to about 1 teaspoon of table salt, but sodium is found in many processed and pre-packaged foods.
"The average American is eating three times as much salt as is healthy every day -- the equivalent of 2 to 3 teaspoons instead of no more than 1," he says. "The assumption tends to be, 'If I don't use my salt shaker much, I'm probably OK,' but that just isn't true."
This article was reviewed by Louise Chang, MD.
SOURCES: Cook, N.R. British Medical Journal online, April 19, 2007. Nancy R. Cook, ScD, associate professor, department of medicine, Brigham and Women's Hospital, Harvard Medical School, Boston. J. James Rohack, MD, FACC, FACP, board member, American Medical Association; director, Center for Healthcare Policy, Scott and White Health Plan. "Reducing the Population Burden of Cardiovascular Disease by Reducing Sodium Intake," AMA publication, June 2006. American Heart Association web site.