The 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

Sacks FM, Svetkey LP, Vollmer WM, et al.

Bottom Line

The DASH-Sodium trial demonstrated that both the DASH dietary pattern and reduced sodium intake significantly and independently lower blood pressure, with the greatest reductions achieved when the two interventions are combined.

Key Findings

1. Reducing sodium intake from a high level (150 mmol/d) to an intermediate level (100 mmol/d) and then to a low level (50 mmol/d) resulted in a dose-dependent, significant reduction in systolic and diastolic blood pressure across both dietary groups.

2. Among participants on the control diet, reducing sodium from the high to the low level lowered systolic blood pressure by an average of 6.7 mm Hg.

3. The DASH diet itself, compared to the control diet, reduced systolic blood pressure by an average of 5.9 mm Hg at the high sodium level, 7.2 mm Hg at the intermediate level, and 8.9 mm Hg at the low sodium level.

4. The combination of the DASH diet and the lowest sodium intake (50 mmol/d) produced the largest blood pressure reductions compared to the control diet at the highest sodium intake, with an average reduction of 7.1/3.3 mm Hg in those without hypertension and 11.5/6.3 mm Hg in those with hypertension.

Study Design

Design

RCT

N/A

Sample

412

Patients

Duration

30 days per level

Median

Setting

Multicenter, US

Population Adults aged 22 years or older with systolic blood pressure of 120-159 mm Hg and diastolic blood pressure of 80-95 mm Hg, free of antihypertensive medications.

Intervention DASH diet (rich in fruits, vegetables, and low-fat dairy; reduced in saturated fat, total fat, and cholesterol) combined with three levels of sodium intake (150, 100, and 50 mmol/d).

Comparator Control diet (typical of the American diet, low in fruits, vegetables, and dairy) combined with three levels of sodium intake (150, 100, and 50 mmol/d).

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

Study Limitations

• The study was conducted as a tightly controlled feeding trial, which may limit the generalizability of these findings to real-world settings where dietary adherence and food choices are more variable.

• The follow-up period for each sodium level was relatively short (30 days), potentially failing to capture the long-term sustainability or physiologic adaptation to these dietary changes.

• The study population was restricted to adults with baseline systolic blood pressure between 120 and 159 mm Hg and diastolic blood pressure between 80 and 95 mm Hg, meaning results may not be applicable to individuals with severe hypertension or those already on pharmacologic treatment.

Clinical Significance

The results provide robust, evidence-based support for nonpharmacologic lifestyle modifications—specifically the DASH diet and sodium restriction—as first-line strategies for the prevention and management of hypertension in adults, potentially reducing the need for or the dose of antihypertensive medications.

Historical Context

Following the original 1997 DASH trial which established the blood pressure-lowering effects of the DASH dietary pattern, the DASH-Sodium trial was initiated to specifically quantify the independent and additive effects of dietary sodium reduction, settling long-standing debates regarding the magnitude of sodium's impact on blood pressure in both hypertensive and normotensive populations.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

What are the physiological mechanisms by which the DASH diet's high potassium, calcium, and magnesium content independently lower blood pressure compared to a standard American diet?

Key Response

High potassium intake promotes natriuresis by inhibiting the sodium-chloride cotransporter (NCC) in the distal tubule and improves endothelial function through hyperpolarization of vascular smooth muscle cells. Calcium and magnesium act as cofactors in enzymatic reactions that regulate vascular tone and reduce peripheral resistance, providing a synergistic effect with sodium restriction.

Resident

In the DASH-Sodium trial, which subgroup of patients showed the most significant reduction in blood pressure when moving from the intermediate to the low sodium level, and how does this affect your clinical approach to stage 1 hypertension?

Key Response

The trial demonstrated that while all groups benefited, participants with hypertension (as opposed to pre-hypertension) and African Americans showed the largest reductions. Clinically, this reinforces that aggressive sodium reduction to 1,500 mg/day is a potent first-line 'non-pharmacologic' intervention that can rival the efficacy of single-agent drug therapy in these populations.

Fellow

The DASH-Sodium trial utilized a controlled feeding design. How does the 'dose-response' relationship of sodium observed in this study challenge the 'J-shaped curve' hypothesis seen in some observational cohorts regarding sodium intake and cardiovascular mortality?

Key Response

The trial showed a linear, step-wise reduction in BP down to 1,500 mg/day without evidence of an adverse floor effect on BP. Observational studies suggesting a J-shaped curve (increased risk at low sodium levels) are often criticized for 'reverse causality' or 'confounding by illness,' whereas the DASH-Sodium trial provides high-quality experimental evidence that lower sodium levels are physiologically beneficial for BP control.

Attending

Given that the DASH-Sodium trial achieved results via strictly provided meals, how should we adapt our teaching for medical students regarding the 'real-world' efficacy of these interventions versus their 'trial' efficacy?

Key Response

This highlights the 'efficacy-effectiveness gap.' While the trial proves a biological effect (efficacy), real-world success (effectiveness) is limited by socioeconomic factors, food deserts, and the ubiquity of processed foods. Teaching should focus on 'prescribing' specific dietary patterns and advocating for systemic policy changes (e.g., food industry regulations) rather than just individual-level advice.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

Evaluate the strengths and limitations of the randomized, crossover design used in the DASH-Sodium trial compared to a longitudinal parallel-group design in terms of statistical power and assessment of long-term metabolic adaptation.

Key Response

The crossover design increases statistical power by allowing subjects to serve as their own controls, reducing the impact of inter-individual variability. However, it is limited by potential 'carryover effects' if the washout period is insufficient and cannot assess long-term compensatory mechanisms like the activation of the renin-angiotensin-aldosterone system (RAAS) that might occur over years of sodium restriction.

Journal Editor

If the DASH-Sodium trial were submitted today, how would the inclusion of 'standardized feeding' affect the manuscript's priority compared to a pragmatically designed 'behavioral counseling' dietary trial?

Key Response

Standardized feeding is the gold standard for internal validity (proving the diet causes the BP drop), making it highly prestigious for a top-tier journal. However, a modern editor might flag the lack of 'external generalizability' and demand a discussion on how these results translate to free-living populations who must source and prepare their own meals.

Guideline Committee

The 2017 ACC/AHA Hypertension Guidelines recommend a sodium intake of <1,500 mg/day. How does the DASH-Sodium trial provide the foundational evidence for this specific threshold compared to previous guidelines that suggested 2,300 mg/day?

Key Response

The DASH-Sodium trial was pivotal because it explicitly tested three distinct levels of sodium (3,300, 2,400, and 1,500 mg/day). It proved that the 1,500 mg level provided significantly greater BP reduction than the 2,400 mg level (the previous standard), regardless of the dietary pattern, justifying the downward shift in guideline targets for blood pressure optimization (Level of Evidence: A).

Clinical Landscape

Noteworthy Related Trials

1997

TOHP Phase II

n = 2,382 · BMJ

Tested

Sodium reduction and weight loss

Population

Overweight adults with high-normal blood pressure

Comparator

Usual care

Endpoint

Systolic and diastolic blood pressure

Key result: Moderate reduction in sodium intake and weight loss significantly lowered systolic and diastolic blood pressure.

2001

Sacks et al. DASH-Sodium Trial

n = 412 · NEJM

Tested

DASH diet combined with varying sodium levels

Population

Adults with elevated blood pressure

Comparator

Control diet with varying sodium levels

Endpoint

Change in systolic blood pressure

Key result: Both the DASH diet and reduced sodium intake significantly lowered blood pressure, with the greatest reductions seen when the DASH diet was combined with low sodium intake.

2003

PREMIER Trial

n = 810 · JAMA

Tested

Established behavioral lifestyle intervention

Population

Adults with hypertension or high-normal blood pressure

Comparator

Advice-only control group

Endpoint

Change in systolic and diastolic blood pressure

Key result: Combining behavioral weight loss, physical activity, and DASH diet adherence resulted in superior blood pressure reduction compared to advice alone.

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