Effect of Modest Salt Reduction on Blood Pressure, Urinary Albumin, and Pulse Wave Velocity in White, Black, and Asian Mild Hypertensives

Abstract

Abstract-A reduction in salt intake lowers blood pressure. However, most previous trials were in whites with few in blacks and Asians. Salt reduction may also reduce other cardiovascular risk factors (eg, urinary albumin excretion, arterial stiffness). However, few well-controlled trials have studied these effects. We carried out a randomized double-blind crossover trial of salt restriction with slow sodium or placebo, each for 6 weeks, in 71 whites, 69 blacks, and 29 Asians with untreated mildly raised blood pressure. From slow sodium to placebo, urinary sodium was reduced from 165Ϯ58 (ϮSD) to 110Ϯ49 mmol/24 hours (9.7 to 6.5 g/d salt). With this reduction in salt intake, there was a significant decrease in blood pressure from 146Ϯ13/91Ϯ8 to 141Ϯ12/88Ϯ9 mm Hg (PϽ0.001), urinary albumin from 10.2 (IQR: 6.8 to 18.9) to 9.1 (6.6 to 14.0) mg/24 hours (PϽ0.001), albumin/creatinine ratio from 0.81 (0.47 to 1.43) to 0.66 (0.44 to 1.22) mg/mmol (PϽ0.001), and carotid-femoral pulse wave velocity from 11.5Ϯ2.3 to 11.1Ϯ1.9 m/s (PϽ0.01). Subgroup analysis showed that the reductions in blood pressure and urinary albumin/creatinine ratio were significant in all groups, and the decrease in pulse wave velocity was significant in blacks only. These results demonstrate that a modest reduction in salt intake, approximately the amount of the current public health recommendations, causes significant falls in blood pressure in all 3 ethnic groups. Furthermore, it reduces urinary albumin and improves large artery compliance. Although both could be attributable to the falls in blood pressure, they may carry additional benefits on reducing cardiovascular disease above that obtained from the blood pressure falls alone. Key Words: salt reduction Ⅲ blood pressure Ⅲ ethnic group Ⅲ urinary albumin Ⅲ pulse wave velocity T here is much evidence from epidemiological, migration, intervention, treatment, genetic, and animal studies that dietary salt (sodium chloride) plays an important role in regulating blood pressure (BP), and our current high salt intake is largely responsible for the rise in BP with age. 1 Many randomized trials have demonstrated that a modest reduction in salt intake lowers BP. 2 However, most previous trials were carried out in white individuals. There were only very limited number of trials in blacks 3,4 and even fewer in Asians.Increasing evidence suggests that a lower salt intake may have other beneficial effects (eg, reducing urinary albumin excretion, 5,6 decreasing arterial stiffness as measured by pulse wave velocity 7 ). The evidence for these other effects is mainly from epidemiological and animal studies. Few wellcontrolled trials have studied whether a modest reduction in salt intake has such effects in humans.The average salt intake, as measured by 24-hour urinary sodium, was 8.6 g/d (equivalent to 3.4 g sodium) for adults in the UK according a recent survey in 2008. 8 However, at the time when our study protocol was developed, it was 9.5 g/d, 9 which is very similar to the current salt intake in most countries...

Salt supplementation blunts the blood pressure response to telmisartan with or without hydrochlorothiazide in hypertensive patients with type 2 diabetes

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Effects of Intensive Low-Salt Diet Education on Albuminuria among Nondiabetic Patients with Hypertension Treated with Olmesartan

“…Blockade of the reninangiotensin-aldosterone system (RAAS) is well known to reduce urinary albumin excretion, and it is considered a mainstay of therapy in the prevention of ESRD (4,5). The antiproteinuric effect of the RAAS blockade can be magnified or reduced depending on the amount of dietary salt intake (6)(7)(8)(9)(10)(11).…”

The relationship between systolic and diastolic blood pressure: a clinically meaningful slope?

“…These data are in sharp contrast with the current literature, which shows a beneficial effect of salt restriction on arterial stiffness. 43,44 The authors provide no explanation for this puzzling finding. The examined population was very small, with approximately one dozen patients enrolled in each of the three studies.…”