Sodium & Blood Pressure: Med Diet Wins!

randomized-controlled-trial PMID: 37625311

Quick Summary: This study looked at how different diets affect blood pressure when combined with a low-sodium diet. The results showed that both the DASH and Mediterranean diets, along with sodium restriction, helped lower blood pressure. The Mediterranean diet was the most effective at lowering systolic blood pressure (the top number).

Does Sodium Affect Blood Pressure?

Yes, it does! This research explored how reducing sodium intake, along with different eating plans, impacts blood pressure. The study compared a control group (no specific diet), a low-sodium group, a DASH diet with low sodium, and a Mediterranean diet with low sodium.

What The Research Found

The study found that:

All intervention groups (low sodium, DASH, and Mediterranean) lowered blood pressure compared to the control group.

The Mediterranean diet was the most effective at lowering systolic blood pressure (the top number in a blood pressure reading) compared to the other groups.

Both the DASH and Mediterranean diets were more effective at lowering blood pressure than just restricting sodium.

Study Details

Who was studied: 240 adults with slightly high blood pressure (but not taking blood pressure medication).

How long: The study lasted for 3 months.

What they took: Participants were divided into four groups:

Control Group: No specific diet changes.
Low Sodium Group: Followed a low-sodium diet.
DASH Diet Group: Followed the DASH diet (focuses on fruits, vegetables, and low-fat dairy) and a low-sodium diet.
Mediterranean Diet Group: Followed the Mediterranean diet (focuses on olive oil, fish, and plant-based foods) and a low-sodium diet.

What This Means For You

If you have slightly high blood pressure, talk to your doctor about reducing your sodium intake.

Consider the DASH or Mediterranean diet: These diets, combined with sodium restriction, may help lower your blood pressure.

The Mediterranean diet might be especially helpful for lowering the top number in your blood pressure reading.

Focus on whole foods: Both diets emphasize fruits, vegetables, whole grains, and healthy fats.

Study Limitations

Sodium levels weren't exact: The study didn't measure exactly how much sodium each person ate.

Short-term study: The study only lasted 3 months, so we don't know the long-term effects.

Specific population: The results only apply to people with slightly high blood pressure who weren't taking medication.

Relied on self-reporting: Researchers relied on participants to follow the diets, which can be tricky.

Key Findings

The study found that both the DASH and Mediterranean diets (MedDiet), combined with sodium restriction, significantly reduced blood pressure (BP) compared to sodium restriction alone or control. However, the MedDiet showed superior efficacy in lowering office systolic BP (primary outcome):
- MedDiet group (MDG): -15.1 mmHg vs. control group (CG) (p<0.001).
- DASH diet group (DDG): -11.9 mmHg vs. CG (p<0.001).
- Salt restriction group (SRG): -7.6 mmHg vs. CG (p<0.001).

MDG reduced systolic BP by 7.5 mmHg compared to SRG (p<0.001) and 3.2 mmHg compared to DDG (p<0.001). No significant differences were observed in diastolic BP or 24-hour ambulatory BP between DDG and MDG, though both outperformed SRG.

Study Design

This was a randomized controlled trial (RCT) with four arms:
1. Control group (CG): No/minimal intervention (n=60).
2. Salt restriction group (SRG): Sodium-restricted diet alone (n=60).
3. DASH diet group (DDG): DASH diet with sodium restriction (n=60).
4. Mediterranean diet group (MDG): MedDiet with sodium restriction (n=60).

Sample size: 240 adults (mean age not specified) with high-normal BP or grade 1 hypertension, not on BP medication. Duration: 3 months. Outcomes were analyzed via intention-to-treat (ITT) and per-protocol methods.

Dosage & Administration

The study focused on dietary patterns rather than specific sodium doses. All intervention groups received guidance to implement sodium restriction, but exact intake targets (e.g., grams/day) were not quantified in the summary. DDG and MDG followed structured meal plans aligning with DASH or MedDiet principles, emphasizing fruits, vegetables, whole grains, and healthy fats, while limiting sodium.

Results & Efficacy

Office systolic BP:
MDG: -15.1 mmHg vs. CG (p<0.001).
DDG: -11.9 mmHg vs. CG (p<0.001).
SRG: -7.6 mmHg vs. CG (p<0.001).
Office diastolic BP:
MDG: -7.3 mmHg vs. CG (p<0.001).
DDG: -6.9 mmHg vs. CG (p<0.001).
SRG: -4.2 mmHg vs. CG (p<0.001).
24-hour ambulatory BP:
Both MDG and DDG reduced systolic BP by ~5.5 mmHg vs. CG (p<0.001), with no significant difference between diets.

The MedDiet demonstrated statistically superior systolic BP reduction compared to DASH and SRG, while both diets exceeded the efficacy of sodium restriction alone.

Limitations

Unclear sodium intake: The study did not specify exact sodium consumption levels achieved in each group, limiting reproducibility.
Control group variability: The CG received minimal intervention, but baseline BP differences (e.g., medication status) might influence outcomes.
Self-reported adherence: Dietary compliance was not objectively measured, risking bias.
Short duration: Results reflect 3-month effects; long-term sustainability and BP impacts remain unknown.
Population specificity: Findings apply only to adults with high-normal BP/grade 1 hypertension not on medication.

Clinical Relevance

For individuals with elevated BP, combining sodium restriction with either the DASH or MedDiet yields greater reductions than sodium restriction alone. The MedDiet may offer additional benefits for office systolic BP, suggesting it could be a preferred option in clinical settings. However, both diets require intensive counseling and adherence support, which may not be feasible in real-world scenarios. These results reinforce dietary interventions as a first-line approach for mild hypertension, though further research is needed to clarify optimal sodium targets and long-term outcomes. Patients should consult healthcare providers to tailor dietary strategies to their needs.