Emphasized warning reduces salt intake: a randomized controlled trial

Abstract

Excessive salt intake is a major cardiovascular risk factor. At variance to the developed countries, the main source of sodium in transitional and developing countries is salt added while cooking and/or at the table. The objective of this trial was to examine the impact of warning labels placed on home salt containers on daily salt intake.A sample of treated hypertensives (n = 150) was randomized in two subgroups, one receiving just a leaflet about the harmful effects of excessive salt intake (control; n = 74), and the other one receiving in addition warning stickers for household salt containers (intervention; n = 76). Arterial blood pressure (BP) and 24-hour urinary sodium excretion (Na24) were measured in all the subjects at the start of the trial, and 1 month and 2 months later. The average starting Na24 was 207 ± 71 mmol in the control group and 211 ± 85 mmol in the intervention group (P = .745). One month and 2 months later, a significant decrease was observed in the intervention group (to 183 ± 63 mmol and 176 ± 55 mmol; P < .0001), as opposed to the control group (203 ± 60 mmol and 200 ± 58 mmol; P = .1466). Initial BP was 143.7/84.1 mm Hg in the control, and 142.9/84.7 mm Hg in the intervention group (P = .667). One month and 2 months later, a significant drop in BP, by 5.3/2.9 mm Hg, was observed in the intervention group as opposed to the control group (0.4/0.9 mm Hg). Decrease in Na24 positively correlated to BP lowering (r(2) = 0.5989; P < .0001). A significant reduction in 24Na and BP is achieved with warning labels on harmful effects of excessive salt intake. Decreasing daily salt input by 35 mmol may result in an extra BP lowering by some 5-6/2-3 mm Hg.

Keywords: Arterial hypertension; blood pressure; salt consumption; sodium.