Dietary Sodium and Nocturnal Blood Pressure Dipping in Normotensive Men and Women

Impaired nocturnal blood pressure (BP) dipping (i.e., <10% decline in nocturnal BP) is associated with an increased risk of cerebrovascular and cardiovascular diseases. Excess sodium has been shown to impair BP regulation and increase cardiovascular disease risk, yet few studies have assessed the influence of dietary sodium on nocturnal dipping in normotensive adults. The purpose of this study was to determine the effects of dietary sodium on BP dipping in normotensive men and women. Eighty healthy normotensive adults participated in a controlled feeding study (men: n=39, 34±2 yrs; women: n=41, 41±2 yrs). Participants consumed a standardized run-in 100 mmol sodium·day(−1) diet for 7 days, followed by 7 days of low sodium (LS; 20 mmol·day(−1)) and high sodium (HS; 300 mmol·day(−1)) diets in random order. On the final day of each diet, subjects wore a 24h ambulatory BP monitor, collected a 24h urine sample, and provided a blood sample. During the run-in diet, 24h urinary sodium excretion was 79.4±5.1 mmol·24h(−1) in men and 85.3±5.5 mmol·24h(−1) in women (p>0.05). Systolic BP dipping was not different between men (11.4±1.0%) and women (11.2±0.9%) (p>0.05). During the HS diet, 24h urinary sodium excretion increased compared to the LS diet in men (LS=31.7±4.6 mmol·24h(−1) vs. HS=235.0±13.9 mmol·24h(−1), p<0.01) and women (LS=25.8±2.2 mmol·24h(−1) vs. HS=234.7±13.8 mmol·24h(−1), p<0.01). Despite this large increase in sodium intake and excretion, systolic BP dipping was not blunted in men (LS=8.9±1.0% vs. HS=9.4±1.2%, p>0.05) or women (LS=10.3±0.8% vs. HS=10.5±0.8%, p>0.05). Among normotensive men and women, HS does not blunt nocturnal BP dipping.