Sodium intake is associated with cardiovascular disease and stroke only in communities where mean sodium intake exceeds 5 grams per day, according to a new study. Greater potassium intake, however, is associated with decreased rates of stroke, cardiovascular death, and all-cause mortality in all communities.
“Our findings suggest that a population-specific strategy for sodium reduction targeted at countries or communities with sodium intake greater than 5 g/day would be preferable to a population-wide strategy of sodium reduction to reduce cardiovascular disease and premature deaths,” a research team led by Andrew Mente, PhD, of McMaster University in Hamilton, Ontario, reported in The Lancet. “In contrast, there is a strong case for increasing the consumption of foods that are rich in potassium (eg, fruits and vegetables) population wide.”
The authors noted that the World Health Organization recommends that populations consume less than 2 g/day to prevent cardiovascular disease, but no country has achieved this target.
As part of the Prospective Urban Rural Epidemiology study, investigators analyzed data from individuals in 18 countries who were aged 35 to 70 years without cardiovascular disease. They assessed blood pressure (BP) in 95,767 participants in 369 communities and cardiovascular outcomes in 82,544 participants in 255 communities.
During a median follow-up of 8.1 years, 3695 individuals died, 3543 experienced major cardiovascular events (myocardial infarction [MI], stroke, heart failure, and cardiovascular death), Dr Mente and colleagues reported. In addition, 6281 had a composite outcome of a cardiovascular event or death. The median sodium intake across 369 communities was 4.77 grams per day (range 3.22 to 7.52). Sodium intake was much higher in communities in China than those in other countries (5.58 vs 4.45 g/day). The mean intake was greater than 5 g/day in 82 (80%) of 103 communities in China and 5 g/day or less in 224 (84%) of 266 communities outside of China.
Overall, mean systolic BP increased by 2.86 mm Hg per 1 g increase in mean sodium intake, but investigators found positive associations only among communities in the highest tertile of sodium intake.
In 225 communities, the investigators found a positive association between sodium intake and mean overall cardiovascular event rate. Each 1 g/day increase in sodium intake was significantly associated with 0.66 events per 1000 years. After multivariable adjustment for known confounders, each 1 g increase in sodium intake was significantly associated with 0.73 events per 1000 years, according to researchers. The association was mainly attributable to stroke, with a rate of 1.01 events per 1000 years for each 1 g increase in sodium intake after multivariable adjustment.
Dr Mente and his team found no significant association between mean sodium intake and mean rates of MI, total mortality, or the composite outcome of major cardiovascular events or mortality, after adjusting for age, sex, and country. After multivariable adjustment, they found inverse associations between each 1 g increase and MI and total mortality, and no significant association with the composite outcome.
The association with stroke was observed only among communities in the highest tertile of sodium intake, most of which were in China, where mean sodium intake was 5.58 g/day and each 1 g increase in mean sodium intake was significantly associated with 0.42 stroke events per 1000 years. In other countries, the mean sodium intake was 4.49 g/day and each 1 g increase in mean sodium intake was inversely associated with stroke (0.46 fewer stroke events per 1000 years).
After multivariable adjustment, the investigators found inverse associations between increasing mean potassium intake and all major cardiovascular events in all regions. The authors noted that diets rich in fruits and vegetables are high in potassium and often have been linked with improved health outcomes, “suggesting that high potassium concentrations might simply be a marker of a healthy dietary pattern.” They cited previous studies showing that high potassium intake seems to diminish cardiovascular risk associated with high sodium intake. “If potassium is protective, substitution of potassium for sodium in salt might be a particularly effective intervention,” they wrote. “If, however, the health associations with potassium intake are simply, markers of a better quality diet, substitutions in salt might not necessarily reduce stroke or cardiovascular disease.”
Mente A, O’Donnell M, Rangarajan S, et al. Urinary sodium excretion, blood pressure, cardiovascular diseae, and mortality: a community-level prospective epidemiological cohort study. Lancet. 2018;392:496-506.