EFFECTS OF SODIUM RESTRICTION ON BLOOD-PRESSURE, RENIN, ALDOSTERONE, CATECHOLAMINES, CHOLESTEROLS, AND TRIGLYCERIDE - A METAANALYSIS

Context.-One of the controversies in preventive medicine is whether a general reduction in sodium intake can decrease the blood pressure of a population and thereby reduce the number of strokes and myocardial i nfarctions. In recent years the debate has been extended by studies in dicating that reduced sodium intake has adverse effects. Objective.-To estimate the effects of reduced sodium intake on systolic and diastol ic blood pressure (SBP and DBP), body weight, and plasma or serum leve ls of renin, aldosterone, catecholamines, cholesterols, and triglyceri de, and to evaluate the stability of the blood pressure effect in rela tion to additional trials. Data Sources.-MEDLINE search from 1966 thro ugh December 1997 and reference lists of relevant articles. Study Sele ction.-Studies randomizing persons to high-sodium and low-sodium diets were included if they evaluated at least one of the effect parameters . Data Extraction.-Two authors independently recorded data. Data Synth esis.-In 58 trials of hypertensive persons, the effect of reduced sodi um intake as measured by urinary sodium excretion (mean, 118 mmol/24 h ) on SEP was 3.9 mm Hg (95% confidence interval [CI], 3.0-4.8 mm Hg) ( P<.001) and on DBP was 1.9 mm Hg (95% CI, 1.3-2.5 mm Hg) (P<.001). In 56 trials of normotensive persons, the effect of reduced sodium intake (mean, 160 mmol/24 h) on SEP was 1.2 mm Hg (95% CI, 0.6-1.8 mm Hg) (P <.001) and on DBP was 0.26 mm Hg (95% CI, -0.3-0.9 mm Hg) (P=.12). The cumulative analysis showed that this effect size has been stable sinc e 1985. In plasma, the renin level increased 3.6-fold (P<.001), and th e aldosterone level increased 3.2-fold (P<.001); the increases were pr oportional to the degree of sodium reduction for both renin (r=0.66; P <.001) and aldosterone (r=0.64; P<.001). Body weight decreased signifi cantly, and noradrenaline, cholesterol, and low-density lipoprotein ch olesterol levels increased. There was no effect on adrenaline, triglyc eride, and high-density lipoprotein cholesterol. Conclusion.-These res ults do not support a general recommendation to reduce sodium intake. Reduced sodium intake may be used as a supplementary treatment in hype rtension. Further long-term studies of the effects of high reduction o f sodium intake on blood pressure and metabolic variables may clarify the disagreements as to the role of reduced sodium intake, but ideally trials with hard end points such as morbidity and survival should end the controversy.