Despite collating more event data than previous systematic reviews of randomised controlled trials (665 deaths in some 6,250 participants), there is still insufficient power to exclude clinically important effects of reduced dietary salt on mortality or cardiovascular morbidity in normotensive or hypertensive populations. Our estimates of benefits from dietary salt restriction are consistent with the predicted small effects on clinical events attributable to the small blood pressure reduction achieved.
Effects of weight loss and sodium reduction intervention on blood pressure and hypertension incidence in overweight people with high-normal blood pressure. The Trials of Hypertension Prevention, phase II. The Trials of Hypertension Prevention Collaborative Research Group.
To provide a firmer basis for preventing high blood pressure (BP), we tested interventions to promote weight loss, dietary sodium reduction, and their combination for lowering diastolic BP, systolic BP, and the incidence of hypertension during a 3- to 4-year period.
                We conducted a randomized, 2 x 2 factorial, clinical trial, with BP levels measured by blinded observers. Nine academic medical centers recruited 2382 men and women (age range, 30-54 years) not taking antihypertensive drugs, with a diastolic BP of 83 to 89 mm Hg, a systolic BP lower than 140 mm Hg, and a body mass index (the weight in kilograms divided by the square of the height in meters) representing 110% to 165% of desirable body weight. Counseling aimed at helping participants achieve their desirable weight or a 4.5-kg or more weight reduction (in the weight loss and combined groups) and/or sodium intake of 80 mmol/d (in the sodium reduction and combined groups) was provided.
                From baseline, participants' weight decreased by 4.3 to 4.5 kg at 6 months and by approximately 2 kg at 36 months in the weight loss and combined groups compared with weight changes in the usual care group (all groups, P < .001). Sodium excretion decreased 50 and 40 mmol/d at 6 and 36 months, respectively, in the sodium reduction group and about 15 mmol/d less at each time point in the combined group compared with the usual care group (all groups, P < .01). Compared with the usual care group, BP decreased 3.7/2.7 mm Hg in the weight loss group, 2.9/1.6 mm Hg in the sodium reduction group, and 4.0/2.8 mm Hg in the combined group at 6 months (all groups, P < .001). At 36 months, BP decreases remained greater in the active intervention groups than in the usual care group (weight loss group, 1.3/0.9 mm Hg; sodium reduction group, 1.2/0.7 mm Hg; combined group, 1.1/0.6 mm Hg). Differences were statistically significant for systolic and diastolic BP in the weight loss group and for systolic BP in the sodium reduction group. Through 48 months, the incidence of hypertension (BP > or = 140 mm Hg systolic or > or = 90 mm Hg diastolic or the use of antihypertensive drugs) was significantly less in each active intervention group than the usual care group (average relative risks, 0.78-0.82).
                In overweight adults with high-normal BP, weight loss and reduction in sodium intake, individually and in combination, were effective in lowering systolic and diastolic BP, especially in the short-term (6 months). Although the effects on average BP declined over time, reductions in hypertension incidence were achieved.