Observational studies indicate a significant relation between
dietary sodium and level of blood pressure. However, the role of
salt sensitivity in the development of resistant
hypertension is unknown. The present study examined the effects of dietary
salt restriction on office and 24-hour ambulatory blood pressure in subjects with resistant
hypertension. Twelve subjects with resistant
hypertension entered into a randomized crossover evaluation of low (50 mmol/24 hours x 7 days) and high
sodium diets (250 mmol/24 hours x 7 days) separated by a 2-week washout period.
Brain natriuretic peptide; plasma
renin activity; 24-hour urinary
aldosterone,
sodium, and
potassium; 24-hour ambulatory blood pressure monitoring; aortic pulse wave velocity; and augmentation index were compared between dietary treatment periods. At baseline, subjects were on an average of 3.4+/-0.5
antihypertensive medications with a mean office BP of 145.8+/-10.8/83.9+/-11.2 mm Hg. Mean urinary
sodium excretion was 46.1+/-26.8 versus 252.2+/-64.6 mmol/24 hours during low- versus high-
salt intake. Low- compared to high-
salt diet decreased office systolic and diastolic blood pressure by 22.7 and 9.1 mm Hg, respectively. Plasma
renin activity increased whereas
brain natriuretic peptide and
creatinine clearance decreased during low-
salt intake, indicative of intravascular volume reduction. These results indicate that excessive
dietary sodium ingestion contributes importantly to resistance to
antihypertensive treatment. Strategies to substantially reduce dietary
salt intake should be part of the overall treatment of resistant
hypertension.