New England Journal of Medicine January 04, 2001

Effects on Blood Pressure of Reduced Dietary Sodium and the Dietary Approaches to Stop Hypertension (DASH) Diet

Frank M. Sacks, Laura P. Svetkey, William M. Vollmer, et al. (DASH-Sodium Collaborative Research Group)

Bottom Line

The DASH-Sodium trial demonstrated that combining the DASH diet with strict dietary sodium reduction produces substantial, independent, and additive decreases in blood pressure, achieving reductions comparable to single-agent antihypertensive therapy.

Key Findings

1. Reducing sodium intake from high (~150 mmol/day) to intermediate (~100 mmol/day) reduced systolic blood pressure by 2.1 mm Hg (P<0.001) in participants on the control diet and by 1.3 mm Hg (P=0.03) in those on the DASH diet.

2. Further reducing sodium intake from intermediate to low (~50 mmol/day) caused additional systolic blood pressure reductions of 4.6 mm Hg (P<0.001) during the control diet and 1.7 mm Hg (P<0.01) during the DASH diet.

3. The DASH diet lowered systolic blood pressure significantly more than the control diet at every sodium level, though the absolute difference between diets was greatest when sodium intake was high.

4. The maximum blood pressure lowering was achieved by combining both interventions: compared with the control diet at high sodium, the low-sodium DASH diet lowered mean systolic blood pressure by 7.1 mm Hg in normotensive participants and by 11.5 mm Hg in hypertensive participants.

Study Design

Design

Randomized Controlled Trial

Single-Blind

Sample

412

Patients

Duration

30 days per diet phase

Median

Setting

Multicenter, US

Population Adults (aged ≥22 years) with prehypertension or stage 1 hypertension (systolic BP 120-159 mmHg, diastolic BP 80-95 mmHg) who were not taking antihypertensive medications.

Intervention Participants were randomly assigned to either the DASH diet or a typical American control diet. Within their assigned diet, participants crossed over through three varying sodium levels (high: ~150 mmol/d, intermediate: ~100 mmol/d, low: ~50 mmol/d) in random order for 30 consecutive days each.

Comparator Within-group comparisons across different sodium levels, and between-group comparisons of the DASH diet versus the typical American control diet at matching sodium levels.

Outcome Systolic blood pressure measured at the end of each 30-day dietary intervention period.

Study Limitations

• This was a highly controlled feeding trial where all meals were provided to participants, limiting generalizability to real-world settings where ad libitum dietary adherence and sustained sodium restriction are notoriously difficult.

• The 30-day duration of each feeding period was relatively short, preventing the assessment of long-term sustainability of the blood pressure reductions.

• The trial measured surrogate endpoints (blood pressure) rather than hard clinical cardiovascular outcomes such as myocardial infarction, stroke, or mortality.

• Participants could not be blinded to their assigned overall dietary pattern (DASH vs. control), potentially introducing a degree of expectation bias, although the sodium levels were blinded.

Clinical Significance

The magnitude of blood pressure reduction seen with the low-sodium DASH diet (11.5 mm Hg in hypertensives) rivals or exceeds the expected effect of single-agent antihypertensive pharmacological therapy. This definitively proved that intensive dietary modification can serve as a highly effective first-line intervention for prehypertension and stage 1 hypertension, forming the bedrock for major global dietary sodium guidelines (such as targets of <1,500 to 2,300 mg/day).

Historical Context

The original 1997 DASH trial established that a diet rich in fruits, vegetables, and low-fat dairy lowered blood pressure when sodium was held constant at ~3,000 mg/day. However, the precise dose-response effect of concurrent sodium restriction was highly debated. The 2001 DASH-Sodium trial was designed to evaluate the independent and combined effects of sodium reduction alongside the DASH diet, cementing the evidence base for modern public health campaigns against high salt intake.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

How does the physiological mechanism of blood pressure reduction from the DASH diet, which is rich in potassium, calcium, and magnesium, differ from and complement the mechanism of dietary sodium restriction?

Key Response

Understanding that sodium restriction primarily decreases intravascular volume and sympathetic tone, while the DASH diet's high potassium content promotes natriuresis and vasodilation, explains why their effects are additive and synergistic in reducing blood pressure.

Resident

When counseling a newly diagnosed patient with stage 1 hypertension, how do you practically translate the DASH-Sodium findings into actionable dietary goals, and at what point would you initiate pharmacotherapy if these lifestyle modifications fail?

Key Response

Residents must apply trial data to clinical practice. The DASH-Sodium trial showed BP reductions equivalent to monotherapy, reinforcing that strict lifestyle modification should be a first-line intervention for stage 1 hypertension before starting medications, provided the patient's ASCVD risk is low.

Fellow

The DASH-Sodium trial demonstrated the largest blood pressure reductions in patients already on the control diet who then restricted sodium. How do baseline dietary habits and patient demographics, such as age, race, and baseline blood pressure, influence the anticipated magnitude of effect of the DASH-Sodium intervention?

Key Response

Fellows should appreciate effect modifiers. Older adults, Black patients, and those with higher baseline blood pressure or metabolic syndrome exhibit greater salt sensitivity, meaning they experience more pronounced blood pressure reductions from the combined DASH and low-sodium interventions.

Attending

Given the robust efficacy demonstrated in the DASH-Sodium trial, why is long-term adherence to this combined dietary approach so notoriously poor in routine practice, and what system-level or behavioral interventions can we implement to bridge this efficacy-effectiveness gap?

Key Response

Attendings deal with the reality of longitudinal care. While the trial proved biological efficacy through provided meals, translating this into real-world effectiveness is hampered by the modern food environment, cost, and behavioral fatigue, requiring multi-disciplinary care models.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The DASH-Sodium trial provided all meals to participants to ensure strict adherence. How does this highly controlled feeding study design affect the trial's internal versus external validity, and what alternative trial designs could be used to evaluate the real-world effectiveness of this intervention?

Key Response

Controlled feeding studies maximize internal validity by isolating the biological effect of the nutrients, but they severely limit external validity or real-world applicability. Pragmatic cluster-randomized trials would be the necessary next step to study real-world implementation and effectiveness.

Journal Editor

If reviewing this manuscript today, how would you critically evaluate the short duration of each feeding period, typically 30 days, and does this timeframe adequately capture long-term physiological adaptation and potential counter-regulatory mechanisms to sodium restriction?

Key Response

Editors must look for methodological limitations. While a 30-day feeding period captures acute hemodynamic changes, it may not reflect long-term neurohormonal adaptations like RAAS upregulation or the real-world challenge of adherence, which a rigorous reviewer would flag.

Guideline Committee

How does the magnitude of blood pressure reduction seen in the DASH-Sodium trial influence the ACC/AHA hypertension guidelines' strength of recommendation for lifestyle modifications, particularly concerning the threshold for initiating pharmacological therapy in Stage 1 hypertension?

Key Response

The trial provides Class I, Level A evidence for lifestyle modification. Current ACC/AHA guidelines strongly recommend the DASH diet and sodium restriction as first-line therapy for adults with elevated BP or Stage 1 hypertension with an ASCVD risk under 10 percent, directly relying on the additive efficacy shown in these findings.

Clinical Landscape

Noteworthy Related Trials

1997

DASH Trial

n = 459 · NEJM

Tested

DASH diet rich in fruits, vegetables, and low-fat dairy

Population

Adults with high-normal blood pressure or stage 1 hypertension

Comparator

Control diet typical of American consumption

Endpoint

Change in systolic and diastolic blood pressure

Key result: The DASH diet significantly lowered systolic and diastolic blood pressure compared to the control diet.

1997

TOHP Phase II

n = 2,382 · Arch Intern Med

Tested

Dietary sodium reduction counseling and/or weight loss intervention

Population

Overweight adults with high-normal blood pressure

Comparator

Usual care

Endpoint

Incidence of hypertension

Key result: Sodium reduction and weight loss independently and jointly decreased the incidence of hypertension over 3 to 4 years.

2021

SSaSS (Salt Substitute and Stroke Study)

n = 20,995 · NEJM

Tested

Salt substitute containing 75 percent sodium chloride and 25 percent potassium chloride

Population

Adults with a history of stroke or high blood pressure in rural China

Comparator

Regular salt containing 100 percent sodium chloride

Endpoint

Rate of stroke

Key result: Using a salt substitute significantly reduced the rates of stroke, major cardiovascular events, and all-cause mortality.

Tailored to your role

Want this tailored to you?

Add your specialty or training stage to get role-specific takeaways and more questions.

Personalize this analysis