Systematic review of long term effects of advice to reduce dietary salt in adults

Abstract

Objective To assess the long term effects of advice to restrict dietary sodium in adults with and without hypertension. Design Systematic review and meta-analysis of randomised controlled trials. Data sources Cochrane library, Medline, Embase, and bibliographies. Study selection Unconfounded randomised trials that aimed to reduce sodium intake in healthy adults over at least 6 months. Inclusion decisions, validity and data extraction were duplicated. Random effects meta-analysis, subgrouping, sensitivity analysis, and meta-regression were performed. Outcomes Mortality, cardiovascular events, blood pressure, urinary sodium excretion, quality of life, and use of antihypertensive drugs. Results Three trials in normotensive people (n=2326), five trials in those with untreated hypertension (n=387), and three trials in people being treated for hypertension (n=801) were included, with follow up from six months to seven years. The large high quality (and therefore most informative) studies used intensive behavioural interventions. Deaths and cardiovascular events were inconsistently defined and reported. There were 17 deaths, equally distributed between intervention and control groups. Systolic and diastolic blood pressures were reduced (systolic by 1.1 mm Hg, 95% confidence interval 1.8 to 0.4 mm Hg; diastolic by 0.6 mm Hg, 1.5 to − 0.3 mm Hg) at 13 to 60 months, as was urinary 24 hour sodium excretion (by 35.5 mmol/24 hours, 47.2 to 23.9). Degree of reduction in sodium intake and change in blood pressure were not related. Conclusions Intensive interventions, unsuited to primary care or population prevention programmes, provide only small reductions in blood pressure and sodium excretion, and effects on deaths and cardiovascular events are unclear. Advice to reduce sodium intake may help people on antihypertensive drugs to stop their medication while maintaining good blood pressure control.

Sodium reduction for hypertension prevention in overweight adults: further results from the Trials of Hypertension Prevention Phase II

“…Smaller effects of sodium reduction on DBP than SBP are reported frequently from clinical trials of sodium reduction [2][3][4][5]28 with the apparent, although usually implicit, assumption that the expected effect on SBP and DBP is of the same importance, even if not in magnitude. However, this view is contrary to an increasing body of literature both from large cohort studies, especially the approximately 350 000 middle-aged men screened for the Multiple Risk Factor Intervention Trial 29 and from randomized trials focused on systolic hypertension in older persons.…”

“…The level of sodium reduction in TOHP II approximates the maximum that can be achieved and maintained by individuals making food selections in the community even when these individuals are highly motivated and extensively counseled. 4,5,[34][35][36] Even the relatively modest level of sodium reduction observed in TOHP II is unlikely to be attained in the general US population without changes in the food supply.…”

“…The benefits of sodium reduction for blood pressure (BP) control have been well documented in individuals with established hypertension [1][2][3][4][5] and also in individuals at risk of developing hypertension. [6][7][8] In particular, Phase I of the Trials of Hypertension Prevention (TOHP I) 9 demonstrated a significant effect of sodium reduction in reducing the average BP of 30-54-year-old men and women who were not hypertensive but whose diastolic BP (DBP) was initially in the high normal range (between 80 and 89 mmHg).…”

Dietary patterns among British adults: compatibility with dietary guidelines for salt/sodium, fat, saturated fat and sugars

“…However, the evidence is not without contention and results from meta-analyses have been mixed (5)(6)(7) . Graudal et al concluded in 1998 that studies did not support a general recommendation to reduce Na intake but did support use as a supplementary treatment in hypertension (8) .…”

Salt and blood pressure in children

“…This supports the Cochrane Collaboration conclusion that there was not sufficient evidence for a general dietary recommendation to reduce sodium intake. 11 Parenthetically, it is interesting to note that in countries where most sodium intake is discretionary, as parts of East Asia, sodium intake is much higher than in Britain, where most sodium is not discretionary, but consumed in our foods! The restricted focus of this report does not detract from the careful analysis and lucid presentation by He et al 5 It does, however, account for my dissent from the call for British youngsters to reduce their sodium intake.…”