Sodium intake and blood pressure: new insights

Low dietary sodium intake reduced systolic blood pressure (BP) irrespective of the use of anti-hypertensive agents or hypertension status in the CARDIA-SSBP trial. However, the BP-reducing effect of low sodium intake appears to be higher in individuals with diabetes or higher baseline BP.

“Compared with a standard Western diet, with a daily dietary sodium intake of about 3,500 mg, a low-sodium diet with an intake of 1,150 mg per day resulted in a systolic BP reduction of 6.7 mmHg,” stated Dr Deepak Gupta (Vanderbilt University Medical Centre, TN, USA) [1]. “Since the publication of these results in 2001, sodium intake has not changed much. There are, however, still gaps in our understanding of the relation between dietary sodium and BP.” For example, Dr Gupta mentioned the association between anti-hypertensive medication and salt sensitivity, and the extent to which lowering dietary sodium affects BP among patients with diabetes.

The CARDIA-SSBP study (NCT04258332) included 228 participants between 50–75 years with systolic BP between 90–160 mmHg and diastolic BP between 50–100 mmHg [1,2]. The investigators used a cross-over design in which participants were randomised to a high-sodium diet, comprising their usual diet plus 2,200 mg sodium per day, or a low-sodium diet (i.e. 500 mg sodium/day). After 7 days, participants switched to the other study group.

After 1 week, participants in the low-sodium group had a mean reduction of 8 mmHg in 24-hour ambulatory systolic BP compared with participants in the high-sodium group (95% CI 4–11 mmHg; P<0.0001). “These results were irrespective of anti-hypertensive medication use or whether participants had controlled or uncontrolled hypertension,” added Dr Gupta. “We did see greater reductions in participants with higher baseline BP and in those with diabetes.” An analysis of the within-individual salt sensitivity showed that systolic BP was reduced with low-sodium intake in 74.4% of the participants, and that systolic BP was increased in 21.6% of the participants taking the low-sodium diet as compared with the high-sodium diet (see Figure).

Figure: 24-hour change in systolic BP calculated as high minus low-sodium diet per individual [2]



BP, blood pressure; SBP systolic blood pressure.
Delta 24-hour BP was calculated as high minus low-sodium diet.

In summary, dietary sodium reductions were associated with reductions in systolic BP, whereas the addition of sodium to a standard Western diet had no clear effect on systolic BP. A meaningful BP reduction was achieved in most individuals in this middle-aged to elderly population within 1 week. “The effect of this intervention is comparable with a first-line anti-hypertensive medication,” according to Dr Gupta.

1. 
   
   1. Sacks FM, et al. N Engl J Med 2001;344(1):3–10.
   2. Gupta DK, et al. Effects of dietary sodium on systolic blood pressure in middle-aged individuals: a randomised order cross-over trial. LB04, AHA Scientific Sessions 2023, 11–13 November, Philadelphia, PA, USA.

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Posted on 29 January 202413 June 2024