Influence of Reapportionment of Daily Salt Intake on Orcadian Blood Pressure Pattern in Normotensive Subjects

Abstract

The aim of this study was to investigate whether there is variation in blood pressure when we reapportion the percentage of total daily salt intake consumed at each of three regular meals. The study was conducted on seven clinically healthy normotensive female subjects who, in Stages LH and DH, consumed two-thirds of the normal daily salt intake (12g/day) at lunchtime or at dinnertime, respectively. The total daily amounts of nutrients and dietary salt were similar in Stage-R (regulated salt intake), Stage-LH (a high-salt intake at lunchtime), and Stage-DH (a high-salt intake at dinnertime). The blood pressure response to the variation of sodium content in the meals was examined by means of noninvasive automated blood pressure monitoring (ABPM-630; readings every 15 or 30min over 48 h) and chronobiologic analysis. A significant shift of blood pressure circadian rhythm was observed in Stage-LH. Additionally, the 24-h mean level of blood pressure significantly increased when the prevailing salt intake was at lunch, and significantly decreased when the prevailing intake was at dinner. These opposite responses corroborate the view that the blood pressure susceptibility of human beings to salt intake varies during the day, showing its maximal expression at midday. Such a time-dependent sensitivity may be exploited for better nutritional prevention and treatment of arterial hypertension by reapportioning the salt intake so that two-thirds is consumed at dinner. © 1994, Center for Academic Publications Japan. All rights reserved.