November 11, 2023JAMA127 citationsOpen Access
Effect of Dietary Sodium on Blood Pressure
Key Result
A 1-week low-sodium diet reduced mean systolic blood pressure by 8 mm Hg compared to a high-sodium diet in middle-aged to elderly adults, independent of hypertension status.
Study Design
Type
RCT (n=213)
Blinding
Assessor-blind
Randomization
Crossover
Multicenter
Yes
Structured PICO
Does a low-sodium diet reduce blood pressure in middle-aged to elderly adults compared to a high-sodium diet?
P
Population
213 community-based adults aged 50 to 75 years (median age 61, 65% female, 64% Black) in 2 US cities, including those with normotension (25%), controlled hypertension (20%), uncontrolled hypertension (31%), and untreated hypertension (25%).
I
Intervention
Low-sodium diet (approximately 500 mg daily total) for 1 week.
C
Comparator
High-sodium diet (approximately 2200 mg sodium added daily to usual diet) for 1 week.
O
Outcome
Average 24-hour ambulatory systolic and diastolic BP, mean arterial pressure, and pulse pressure.surrogate
Dietary sodium reduction to approximately 500 mg daily significantly lowered blood pressure across a diverse cohort of middle-aged to elderly adults, independent of baseline hypertension status or antihypertensive medication use.
Main Result
Effect estimate: Mean difference 8 mm Hg (95% CI 4-11)
p-value: p=<.001
Limitations
- 24-hour urine sodium levels on the low-sodium diet were higher than expected, suggesting dietary nonadherence or equilibrium not yet obtained
- Diets were not fully controlled, so contributions of nonsodium dietary components cannot be excluded
- Intra-individual variability in blood pressure over time may contribute to overestimation or underestimation of observed effects
- Study design does not allow assessment of blood pressure effects of longer duration diets or sustainability
- Insufficient power for subgroup analysis
- Results may not be generalizable outside of the community-based population studied
Abstract
Importance: Dietary sodium recommendations are debated partly due to variable blood pressure (BP) response to sodium intake. Furthermore, the BP effect of dietary sodium among individuals taking antihypertensive medications is understudied. Objectives: To examine the distribution of within-individual BP response to dietary sodium, the difference in BP between individuals allocated to consume a high- or low-sodium diet first, and whether these varied according to baseline BP and antihypertensive medication use. Design, Setting, and Participants: Prospectively allocated diet order with crossover in community-based participants enrolled between April 2021 and February 2023 in 2 US cities. A total of 213 individuals aged 50 to 75 years, including those with normotension (25%), controlled hypertension (20%), uncontrolled hypertension (31%), and untreated hypertension (25%), attended a baseline visit while consuming their usual diet, then completed 1-week high- and low-sodium diets. Intervention: High-sodium (approximately 2200 mg sodium added daily to usual diet) and low-sodium (approximately 500 mg daily total) diets. Main Outcomes and Measures: Average 24-hour ambulatory systolic and diastolic BP, mean arterial pressure, and pulse pressure. Results: Among the 213 participants who completed both high- and low-sodium diet visits, the median age was 61 years, 65% were female and 64% were Black. While consuming usual, high-sodium, and low-sodium diets, participants' median systolic BP measures were 125, 126, and 119 mm Hg, respectively. The median within-individual change in mean arterial pressure between high- and low-sodium diets was 4 mm Hg (IQR, 0-8 mm Hg; P < .001), which did not significantly differ by hypertension status. Compared with the high-sodium diet, the low-sodium diet induced a decline in mean arterial pressure in 73.4% of individuals. The commonly used threshold of a 5 mm Hg or greater decline in mean arterial pressure between a high-sodium and a low-sodium diet classified 46% of individuals as "salt sensitive." At the end of the first dietary intervention week, the mean systolic BP difference between individuals allocated to a high-sodium vs a low-sodium diet was 8 mm Hg (95% CI, 4-11 mm Hg; P < .001), which was mostly similar across subgroups of age, sex, race, hypertension, baseline BP, diabetes, and body mass index. Adverse events were mild, reported by 9.9% and 8.0% of individuals while consuming the high- and low-sodium diets, respectively. Conclusions and Relevance: Dietary sodium reduction significantly lowered BP in the majority of middle-aged to elderly adults. The decline in BP from a high- to low-sodium diet was independent of hypertension status and antihypertensive medication use, was generally consistent across subgroups, and did not result in excess adverse events. Trial Registration: ClinicalTrials.gov Identifier: NCT04258332.