Patients who had notably high or notably low sodium intake levels were at an increased risk of both all-cause mortality and cardiovascular disease, compared with patients who had usual sodium intake levels, a new meta-analysis suggests.
In fact, the sodium "sweet spot" may be between 2,645 mg/day and 4,945 mg/day, a range that the report’s investigators noted was "associated with the most favorable health outcomes, within which variation in sodium intake is not associated with variation in mortality."
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Patients who had notably high or notably low sodium intake levels were at an increased risk of both all-cause mortality and cardiovascular disease, compared with patients who had usual sodium intake levels.
Researchers explored the association between sodium intake and health outcomes, basing measurements on the average sodium levels of participants from surveys included in the meta-analysis. Data for the analysis included surveys that tracked sodium intake in population samples from prospective cohort studies and randomized controlled studies. The investigators categorized the measurements as low (less than 2,645 mg/day), usual (between 2,645 mg/day and 4,945 mg/day), and high sodium (more than 4,945 mg/day) intake levels.
"In none of the primary or supplementary analyses was a low sodium intake associated with beneficial effects on [all-cause mortality] or [cardiovascular disease]," the investigators wrote.
When tracking populations with sodium levels outside the usual range, the investigators noticed a U-shaped correlation between sodium intake and health outcomes. The distribution is "in accordance with the generally accepted relationship between a low level of nutrient intake and risk of inadequacy, and a high level of nutrient intake and risk of adverse event," the authors wrote.
Notably, this estimate is higher than the 2004 Institute of Medicine (IOM) recommendations that are currently used by the Centers for Disease Control and Prevention, which set tolerable sodium intake levels at no more than 2,300 mg/day for healthy individuals younger than 50 years, and to 1,500 mg/day for those older than 50 years and other groups at greater risk. However, a study from the IOM in 2013 concluded that the effect of lowered sodium intake on direct health outcomes does not support recommendations to lower sodium intake within these subgroups to or even below 1,500 mg/day.
The results come from a meta-analysis of 274,683 patients in 25 studies. Dr. Niels Graudal of Copenhagen University Hospital led the study. The survey sample included several subsets of data, as well as participants from a wide variety of demographics. The report was published April 2 in the American Journal of Hypertension (doi: 10.1093/ajh/hpu028).
When comparing usual-intake vs. low-intake groups, the researchers found that risk of all-cause mortality was significantly lower in the usual-intake group, but stroke and heart disease risks were the same for both groups.
Compared with high-intake groups, usual-intake groups had significantly lower risks of all-cause mortality, cardiovascular disease, stroke, and heart disease. In addition, there was no significant difference in risk between the high end and low end of the usual-sodium group, suggesting that both ends of the middle category were equally healthful.
The investigators cautioned that the meta-analysis included only two randomized controlled trials, and thus their results were based primarily on observational studies.
The authors of the study declared no conflicts of interest. The A.P. Møller Foundation for the Advancement of Medical Science supported the study.