Soolim Jeong1, Joseph D. Vondrasek2, Braxton A. Linder1, Zach J. Hutchison1, Jordan E. Kinnel3, Meral N. Culver1, McKenna A. Tharpe1, Sofia O. Sanchez1, Joseph C. Watso4, Gregory J. Grosicki2, Austin T. Robinson1. 1Auburn University, Auburn, AL. 2Georgia Southern University, Savannah, GA. 3Tuskegee University, Tuskegee, AL. 4Florida State University, Tallahassee, FL.

BACKGROUND: Dietary sodium (Na+) elevates blood pressure (BP) and blunts nocturnal BP dipping, which is prognostic of future target organ damage and cardiovascular outcomes. Dietary fiber is associated with reduced resting BP. However, the combined effects of dietary Na+ and fiber on ambulatory BP measures, such as nocturnal BP and night-to-day dip ratio (nighttime/daytime BP), are unclear. Therefore, we assessed associations between dietary Na+ indexed to fiber (Na+/fiber) and soluble fiber (Na+/soluble fiber) on ambulatory BP in young adults. METHODS: Sixty-two participants (30 M/32 F, 39 White adults/23 Black adults, age 21.2 ± 2.6 years, BMI 24 ± 3 kg/m2; mean ± SD) were included in the current analysis. Participants completed a food and fluid log for ≥ two weekdays and ≥ one weekend day. We used Nutrition Data System for Research to quantify average daily Na+, fiber, and soluble fiber intake. For ambulatory BP (Suntech Oscar2), participants wore a brachial cuff programmed to measure BP every 20 minutes during awake hours and every 30 minutes during sleep. Primary BP outcomes were average awake and asleep systolic BP (SBP) and diastolic BP (DBP), and night-to-day SBP and DBP dip ratio. Associations between variables were made using Spearman’s Rho (ρ) correlations controlled for sex, BMI, and race with α set at ≤ 0.05. RESULTS: When controlling for sex and BMI, dietary Na+ was correlated with awake SBP (ρ = 0.36, p = 0.005) and asleep SBP (ρ = 0.26, p = 0.044) but not BP dipping ratios (ps ≥ 0.542). Dietary Na+/fiber was also correlated with asleep SBP (ρ = 0.26, p = 0.046) and DBP (ρ = 0.25, p = 0.050) but not BP dipping ratios (ps ≥ 0.243). Dietary Na+/soluble fiber was correlated with SBP dip ratio (ρ = 0.27, p = 0.036) and asleep SBP (ρ = 0.32, p = 0.012). When controlling for race, in addition to sex and BMI, dietary Na+ remained correlated to awake SBP (ρ = 0.36, p = 0.005) and asleep SBP (ρ = 0.29, p = 0.028). Dietary Na+/soluble fiber remained correlated with asleep SBP (ρ = 0.28, p = 0.030). However, controlling for race attenuated the associations between Na+/fiber on asleep BP and Na+/soluble fiber on BP dipping (ps ≥ 0.130). CONCLUSIONS: Our cross-sectional data in healthy young adults indicate that dietary sodium indexed to soluble fiber is independently associated with elevated nocturnal blood pressure.

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