Studies conflict over sodium, death risk
July 13, 2011
by Jeff Gelski
ATLANTA — Two studies published five days apart had conflicting views on the association between sodium intake and the risk of death. According to a study published July 11 in the Archives of Internal Medicine, Americans who eat a diet high in sodium and low in potassium have a 50 percent increased risk of death from any cause and about twice the risk of death from heart attacks. The publication came after a review published July 6 in the American Journal of Hypertension said cutting down the amount of salt has no clear benefits in terms of likelihood of dying or experiencing cardiovascular disease.
Researchers from the Atlanta-based Centers for Disease Control and Prevention, Atlanta-based Emory University and the Harvard School of Public Health in Boston examined the joint effects of dietary sodium and potassium intake. They used the third National Health and Nutrition Examination Survey Linked Mortality File (1988-2006), a prospective cohort study of a nationally representative sample of 12,267 US adults, and studied all-cause, cardiovascular and ischemic heart diseases mortality.
Researchers documented 2,270 deaths, including 825 cardiovascular deaths and 443 ischemic heart disease deaths, during a mean follow-up period of 14.8 years. Higher sodium intake was associated with increased all-cause mortality while higher potassium intake was associated with lower mortality risk.
“The study’s findings are particularly troubling because US adults consume an average 3,300 mg of sodium per day, more than twice the current recommended limit for most Americans,” said Elena Kuklina, an investigator on the study and a nutritional epidemiologist with the CDC’s Division for Heart Disease and Stroke Prevention. “This study provides further evidence to support current public health recommendations to reduce sodium levels in processed foods, given that nearly 80 percent of people’s sodium intake comes from packaged and restaurant foods. Increasing potassium intake may have additional health benefits.”
The other study involved researchers from Florida Atlantic University in Boca Raton, Fla., and researchers in the United Kingdom from the University of Exeter, the University of East Anglia and the London School of Hygiene and Tropical Medicine. They searched for randomized controlled trials with follow-up of at least six months that compared dietary salt restriction to control/no intervention in adults, and reported mortality of cardiovascular disease mortality. They identified seven studies.
“Despite collating more event data than previous systematic reviews of randomized controlled trials [665 deaths in some 6,250 participants], there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or cardiovascular morbidity in ‘normotensive’ or hypertensive populations,” the researchers concluded.
The researchers added further evidence from randomized controlled trials is needed to confirm whether restriction of sodium is harmful for people with heart failure.
“The scientific evidence is overwhelming,” said Lori Roman, president of the Salt Institute, Alexandria, Va., on July 6. “A study by the world-renowned Cochrane Collaboration, published today in the American Journal of Hypertension, proves beyond any reasonable doubt that population-wide sodium reduction efforts provide no measurable benefits and may increase the risk of disease and death. In light of this, and other recent research, it is time for the government to cease its costly and wasteful efforts to reduce salt consumption until it can conclusively prove a tangible benefit for all consumers. This can only be done through a large-scale clinical trial on the impact of dietary salt reduction on health outcomes.”