Randomised controlled trialindependent cross-checkabstract checked★ key study I-SYS-111 in-depth review
Food changes blood pressure
Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. DASH-Sodium Collaborative Research Group.
Overview
Sacks FM et al.. N Engl J Med 2001 · PMID 11136953 · DOI 10.1056/NEJM200101043440101
Less salt and the DASH diet lowered systolic pressure by up to 11.5 mm Hg in people with high blood pressure.
Does the study support the specific claim? No · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Diet and blood pressure.
- How was the study done?
Randomised feeding trial.
- How many people, animals or samples were studied?
412 adults.
- What was actually found?
Large BP reductions.
- How large was the observed effect?
-11.5 mm Hg in hypertension.
- What do the results mean in everyday life?
What you eat changes your blood pressure.
- What are the study's limitations?
Short periods.
- What does it say about Elawady's specific claim?
Contradicts the claim.
- Do the results apply to Germany and Europe?
High.
- What can explicitly not be concluded from this study?
Long-term adherence.
Scientific in-depth review
1. Full reference
- Authors
- Sacks FM et al.
- Journal
- N Engl J Med
- Year
- 2001
- Identifier
- PMID 11136953 DOI 10.1056/NEJM200101043440101
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
NHLBI grants
2. Research question
Effect of dietary sodium and the DASH diet on blood pressure
3. Study design and population
- Study design
- Randomised controlled trial – Randomised controlled feeding trial (DASH-Sodium), crossover of sodium levels within diet arms
- Population
Adults with and without hypertension
- Country
USA
- Period
Published 2001
- Sample size
412
- Inclusion and exclusion criteria
Adults with and without hypertension; detailed criteria not stated in abstract
4. Methods and endpoints
- Exposure / intervention
DASH diet; low/intermediate sodium
- Comparator
Typical US diet; high sodium
- Endpoints
Systolic and diastolic blood pressure
- Statistical methods
Randomised comparison
5. Actual results
- Results
Reducing sodium from high to intermediate lowered SBP by 2.1 mm Hg (control diet) and 1.3 mm Hg (DASH); intermediate to low by a further 4.6 and 1.7 mm Hg. DASH with low sodium vs control with high sodium: SBP 7.1 mm Hg lower without hypertension and 11.5 mm Hg lower with hypertension.
- Absolute risks
Mean differences as reported
- Authors' conclusion
Reducing sodium and the DASH diet both lower blood pressure substantially.
6. Strengths
- Controlled feeding RCT
- Diverse population
7. Weaknesses
- 30-day periods; long-term adherence not tested
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Controlled feeding; objective outcome.
9. Assessment of the statistical interpretation
Mean differences; no ratio CIs to check.
10. Relevance to the specific claim
Direct RCT proof that the type of food changes a key laboratory/clinical marker (blood pressure) - refutes 'linking values to food is 100% wrong'.
11. Independent contrary findings
12. Transferability to Germany and Europe
High.
13. Overall methodological judgement
High-certainty refutation of the diet-marker part of the claim.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | high |
| Directness | direct |
| Reproducibility | replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |