Does lowering sodium intake benefit or hurt CVD risk?

HealthDay News — The association between sodium intake and cardiovascular outcomes is complex, according to research published in The New England Journal of Medicine.

“Reducing dietary sodium and, to a lesser extent, increasing dietary potassium have been included in many guidelines for the treatment of hypertension and prevention of cardiovascular disease,” wrote Suzanne Oparil, MD, of the University of Alabama at Birmingham, in an accompanying editorial.

“However, recent studies have raised questions about potential adverse effects associated with low sodium intake on important health outcomes, including cardiovascular disease and death.”

In order to inspect the effect of sodium intake on global cardiovascular mortality, Dariush Mozaffarian, MD, DrPH, of Tufts University in Boston, and colleagues collected survey data on sodium intake as determined by urinary excretion and diet in patients from 66 countries (accounting for 74.1% of the global adult population).

The effects of sodium on blood pressure, according to age, race, and the presence or absence of hypertension, were calculated from data in a new meta-analysis of 107 randomized interventions.

In 2010, 1.65 million deaths from cardiovascular causes were attributed to sodium consumption above suggested intake levels. These deaths accounted for nearly one of every 10 deaths due to cardiovascular disease reported the researchers.

In a separate study, to examine the relationship between electrolyte excretion and blood pressure, Andrew Mente, PhD, of McMaster University in Hamilton, Canada, and colleagues collected data from 102,216 patients from 18 countries. Each 1 g increment in estimated sodium excretion there were increments of 2.11 mm Hg and 0.78 mm Hg in systolic and diastolic blood pressure, respectively. Higher sodium intake correlated with a steeper slope for this association, as did hypertension and increased age.

“[The study] showed a nonlinear association of sodium and potassium excretion with blood pressure, which was most pronounced among persons consuming high-sodium diets, persons with hypertension, and older persons,” concluded the researchers.

In a third study, to identify the estimated urinary sodium and potassium excretion and composite outcome of death and major cardiovascular events, Martin O’Donnell, PhD, also of McMaster University, and colleagues analyzed data from 101,945 participants in 17 countries.

An estimated sodium excretion higher than the reference range of 4.00 to 5.99 g per day correlated with increased risk of the composite outcome (odds ratio, 1.15). Increased risk of the composite outcome was also seen for estimated sodium excretion below 3.00 g per day (OR, 1.27).

In the accompanying editorial, Oparil urged caution, stating the lack of high-quality evidence in these studies “highlight the need to collect high-quality evidence on both the risks and benefits of low-sodium diets.”