A study published in Circulation shows that lowers sodium intake may lower the risk for cardiovascular disease (CVD). The researchers note that recent studies have raised the possibility of adverse effects of low sodium, particularly less than 2,300 mg/24 hr, on CVD. However, they note that these findings might have resulted from suboptimal measurement of sodium and potential biases related to indication or reverse causation.
The researchers examined data from phases I and II of the Trials of Hypertension Prevention (TOHP), in which multiple 24-hr urine specimens among pre-hypertensive individuals were collected. During extended post-trial surveillance, 193 cardiovascular events or CVD deaths occurred among 2,275 participants not in a sodium reduction intervention. Median sodium excretion was 3,630 mg/24 hr, with 1.4% of the participants having intake <1,500 mg/24 hr and 10% having intake <2,300 mg/24 hr, consistent with national levels.
Compared to those with sodium excretion of 3,600–4,800 mg/24 hr, risk for those with sodium <2,300 mg/24 hr was 32% lower after multivariable adjustment. In addition, the researchers found a linear 17% increase in risk per 1,000 mg/24 hr.
In an editorial from the same issue of Circulation, Lyn M. Steffen, University of Minnesota’s School of Public Health, commented on this study’s findings. “Although the study was not originally designed to test the effectiveness of lower sodium intake on CVD risk, multiple 24-hr urine samples—the ‘gold standard’ measure of sodium intake—were used to characterize usual sodium intake. In most observational studies, sodium intake has commonly been represented by a ‘spot urine’ or overnight urine collection, which is not an accurate estimate of usual sodium intake and thus, previously published study results may be biased.”
The study’s researchers concluded that the results “are consistent with overall health benefits of reducing sodium intake to the 1,500–2,300 mg/day range in the majority of the population, in agreement with current dietary guidelines.”