Dietary sodium and nocturnal blood pressure dipping in normotensive men and women

Abstract

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.

High sodium intake increases blood pressure and risk of kidney disease. From the Science of Salt: A regularly updated systematic review of salt and health outcomes (August 2016 to March 2017)

“…The outcomes examined were diverse: Six studies assessed mortality outcomes, four studies assessed morbidity outcomes, three studies assessed outcomes related to symptoms/quality of life/functional status, studies assessed BP outcomes; eight studies assessed other clinically relevant surrogate outcomes; and nine studies assessed physiologic outcomes (Table ) . A range of outcomes were captured by the studies considered lower quality, including all‐cause mortality, gastric cancer, end‐stage renal disease requiring dialysis or transplant, cardiovascular events, hypertension prevalence, headaches/migraines, quality of life, multiple sclerosis, BP, cognitive function, osteoporosis risk and prevalence, nonalcoholic fatty liver disease, type 2 diabetes, carotid atherosclerosis, bone mineral density, changes in left ventricular mass, inflammatory markers, albuminuria, and other urinary markers . Most of these studies (n = 40) found adverse effects of dietary salt on health outcomes and benefits of a sodium‐restricted diet on health, except for 7 that were neutral and one reported worsening symptoms with a sodium‐restricted diet in the elderly …”

Genetic predisposition to salt-sensitive normotension and its effects on salt taste perception and intake

“…Another potential issue in comparison of different study results is the BP measurement. While most studies still use the conventional measurements, from the studies that employ 24-h BP measurements only a limited number is investigating salt sensitivity solely in healthy, normotensive populations (48)(49)(50) .…”

Blood pressure responses to dietary sodium: Association with autonomic cardiovascular function in normotensive adults

“…The SS assessment protocol has been explained elsewhere (Brian et al, 2017; Matthews et al, 2015). In brief, participants completed a run-in week of recommended dietary sodium intake (100 mmol•day −1 ).…”

“…The change in 24hr MAP from low to high sodium was used as a continuous measurement variable for SS (de Leeuw and Kroon, 2013). Twenty-four hour urinary excretion of sodium was used to confirm participant compliance to the SS test diet and has been published elsewhere (Brian et al, 2017). …”

“…Therefore, the purpose of this study was to test whether there was an association between degree of SS and autonomic cardiovascular function in healthy normotensive adults consuming habitual sodium intake. To accomplish this, we performed autonomic testing in a cohort of subjects that were previously assessed for their degree of SS (Brian et al, 2017). Based on the available literature (Brown et al, 1989; Ferrari et al, 1984; Miyajima and Buñag, 1986; Murphy and McCarty, 1995; Nedvídek and Zicha, 1993; Reddy et al, 1991), we hypothesized that higher SS would be associated with lower parasympathetic activity (HRV), lower vagal and sympathetic baroreflex function, and higher sympathetic activity (muscle sympathetic nerve activity, MSNA).…”