Objective: The main objective of this study is to find out the effects of dietary salt on BP in a general adult population, and to perform a systematic review of all published and non-published available scientific literature on dietary salt in relation to BP.
Methods: Online search of electronic databases, Cochran systematic reviews, PubMed central, electronic journals, citation searching and Google scholar search were used to identify studies on the association between sodium and BP. A total of 67 papers were retrieved, 10 of which met the inclusion criteria and were included in the review. The authors selected the studies, extracted the data and performed narrative analyses. Most studies showed a positive association between total dietary salt and BP. The results of randomized control trials have shown a significant effect of sodium on BP. Some evidence showed that people with elevated BP and/or elders could be more sensitive to dietary salt.
Results: Four trials with normotensive individuals (n=2326) and six trials with stage 1 hypertensive (n=387) were included, with follow up from 28 days to 1095 days. Six, high quality (and therefore most informative) studies and four neutral quality trials used intensive behavioral interventions. Both systolic and diastolic BP were reduced at 1 to 39 months in those given a low salt diet as compared with a usual salt (systolic by 1.7 mm Hg to 12.6 mmHg, diastolic by 0.9 mm Hg, to -10.9 mmHg), as was urinary 24-hour sodium excretion (by 42 mmol per day, to 78 mmol per day). The reduction in sodium intake and the change in BP were not related.
Conclusions: Evidence suggests a small but beneficial effect of reduced dietary salt on BP, with benefits that extend to both non-hypertensive and mild to moderate hypertensive patients. A BP lowering effect of a low sodium diet may have important public health implications, although no clear dose response association could be distinguished. Furthermore, more data are needed on dietary salt from specific sources in relation to BP, and on the salt - BP relations in population subgroups.