Salt restriction in hypertension—the effect of dietary advice and self monitoring of chloride concentration in urine

Abstract

The aims of this present study were firstly to examine whether diet compliance and blood pressure effect could be enhanced by self monitoring with a titrator strip (Quantab 1176) measuring the urine chloride concentration. This was achieved by an open, randomized parallel group design. The study also sought to evaluate the blood pressure effect of a moderately salt restricted diet by using a pre-test-post-test design with a run-in period and controlling for relevant confounding factors (weight, training and alcohol consumption). Furthermore, the study aims were to validate the measurement of chloride concentration in the morning urine by the Quantab titrator strip. We compared Quantab 1176 measurement of chloride concentration in the morning urine with 24 h sodium excretion, determined by the clinical chemical laboratory, was performed.

Twenty men and 14 women (mean age 53 years) with essential hypertension (mean: 165/96 mmHg) were observed during a run-in period of 4 weeks before randomization to either dietary advice combined with self monitoring of morning urine chloride concentration for 12 weeks, or dietary advice alone.

The reduction in diastolic blood pressure of 6 mmHg was not different in the two groups (between groups p = 0.44). Within group changes of systolic blood pressure were 10 mmHg and 6 mmHg (p = 0.006 and p = 0.04) in the diet plus Quantab group, and the diet only group respectively (between groups p = 0.30). No significant difference in 24 h sodium excretion could be detected between the groups. The morning urine chloride concentration correlated moderately to the 24 h urine sodium excretion (r = 0.66, p < 0.001).

It is concluded that self monitoring was not effective either to enhance the salt restriction diet compliance or the blood pressure effect in this study. A diastolic blood pressure reduction of 6 mmHg was attained by simple dietary advice.

Key Words:

• controlled clinical trial
• hypertension
• self monitoring
• sodium-restricted diet