Heart rate variability is altered by dietary sodium: a randomized cross‐over study in healthy young adults

Abstract

Dietary sodium influences intermediate physiological traits in healthy young adults independent of changes in blood pressure. The purpose of this study was to test the hypothesis that dietary sodium affects cardiac autonomic function. In prospective, randomized cross‐over design separated by 1 month or more between diets, 69 normotensive healthy young adults (M/F: 26/43, ages 18–38 yr) consumed a 5‐day low (10 mmol/day), normal (150 mmol), and high sodium (400mmol) diet prior to a protocol examining cardiovascular traits including heart rate variability (HRV) by time domain and frequency domain analysis (Nevrokard). All women were studied in the low hormone phase of the menstrual cycle. Diet did not affect blood pressure, but HR (mean ± SE) was 68±1, 65±1, and 64±1 in low, normal, and high sodium conditions, resp. (RM ANOVA p < 0.01). For HRV there was a main effect of sodium on SDNN, RMSSD, HF, LFnu, HFnu, and LF/HF ratio (p < 0.01 for all). The response to low sodium was most marked and consistent with sympathetic activation, with increased LFnu and LF/HF ratio, and decreased SDNN, RMSSD, and HFnu compared to both normal and high sodium conditions (p ≤ 0.05 for all). These findings suggest that autonomic control of HRV is altered through changes in dietary sodium without changes in blood pressure. Support: UL1 TR000135, HL‐89331