Low Sodium Diet Linked to Reductions in Cardiac Injury, Strain in DASH-Sodium Trial

Patrick Campbell

An analysis of data from DASH-Sodium sheds further light on the impact of increased sodium intake on cardiovascular risk.

Research from clinicians at Brigham and Women’s Hospital and Harvard Medical School is describing the effects of sodium reduction on cardiac biomarkers.

An analysis of the DASH-Sodium Trial, results demonstrate the impact of sodium reduction alone or combine with the DASH diet on biomarkers of cardiac injury, strain, and inflammation—suggesting an approach aimed at sodium reduction was linked to lowering a pair of mechanisms associated with subclinical cardiac damage.

"Our study represents some of the strongest evidence that diet directly impacts cardiac damage, and our findings show that dietary interventions can improve cardiovascular risk factors in a relatively short time period," said study investigator Stephen Juraschek, MD, PhD, Assistant Professor of Medicine at BIDMC and Harvard Medical School, in a statement. "The data reinforce the importance of a lifestyle that includes a reduced-sodium, DASH diet rich in fruits, vegetables and whole grains to minimize cardiac damage over time."

An investigator-initiated controlled feeding study conducted at 4 US medical centers from 1997-1999, DASH-Sodium enrolled 412 patients with elevated blood pressure who were randomized to the DASH diet or a control diet designed to reflect the typical American diet. Patients included in the study underwent measurements of cardiac biomarkers including high-sensitivity cardiac troponin I (hs-cTnI), N-terminal pro–B-type natriuretic peptide (NT-proBNP), and high-sensitivity C-reactive protein (hs-CRP), at baseline and at the end of each feeding period. These measurements represent markers of cardiac injury, cardiac strain, and inflammation, respectively.

Specific inclusion criteria for DASH-Sodium included being at least 22 years of age, mean systolic blood pressure between 120-159 mmHg, and mean diastolic blood pressure of 80-95 mmHg. Patients were excluded based on history of cardiovascular disease, renal insufficiency, dyslipidemia, or diabetes and based on use of antihypertensive agents or insulin.

To assess the impact of sodium intake, investigators further grouped patients in each diet group to one of 3 levels of sodium intake. These levels were tested using a crossover design, with each of the 3 periods lasting 4 weeks in length, and the order of assignment to each level was random. To limit variability, all meals and snacks were provided to participants who ate one main meal per day under observation and consumed the rest off-site.

At the end of the study period, investigators had data related to 1543 biomarker assessments of a possible 1648. Investigators also pointed out the limits of detection for biomarker assays were more than 1.60 ng/l for hs-cTnl, more than 5 pg/ml for NT-proBNP, and greater than 0.160 mg/l for hs-CRP.

The mean age of the study population was 48 years, 56% were women, and 56% were Black, and, at baseline, the mean systolic/diastolic blood pressure was 135/86 mmHg. Initial analyses indicated use of a FASH diet was associated with an 18% reduction in hs-CTnl (18%; 95% CI, -27 to -7), and a 13% reduction in hs-CRP (13%; 95% CI, -24 to -1), but this trend was not noted for NT-proBNP.

Further analysis indicated lowering sodium from high to low levels reduced NT-proBNP independent of diet (19%; 95% CI, -24 to -14) but was not associated with changes in hs-cTnl and increased hs-CRP (9%; 95% CI, 0.4-18). When combining DASH with low sodium, investigators found this approach was associated with a 20% reduction in hs-cTnl and a 23% reduction in NT-proBNP, but hs-CRP was not significantly changed when compared against this eon a high-sodium control diet.

"Our study has important clinical implications, and these findings should strengthen public resolve for public policies that promote the DASH dietary pattern and lower sodium intake in the United States and globally,” Juraschek said.

This study, "Effects of Diet and Sodium Reduction on Cardiac Injury, Strain, and Inflammation: The DASH-Sodium Trial,” was published in the Journal of the American College of Cardiology.