Effects of Dietary Sodium on Systolic Blood Pressure in Middle-Aged Individuals: A Randomized Order Cross-Over Trial

Presented at the AHA Scientific Sessions 2023 by: Deepak Gupta, MD - Nashville, TN, USA

Introduction and methods

Background

Dietary sodium is a major contributor to hypertension. The average sodium consumption in the US is estimated to be around 3,500 mg/day. This far exceeds the AHA, WHA and DHHS recommendations of 1,500 – 2,300 mg/day. The DASH-sodium trial showed in 2001 that sodium reduction leads to a decrease in SBP. However, it remains unclear whether dietary sodium reduction lowers BP among individuals on hypertension medications and what proportion of individuals experience lowering of BP with dietary sodium reduction. The Coronary Artery Risk Development in Young Adults (CARDIA)-SSBP study was conducted to address these questions.

Methods

The CARDIA study included individuals in the US between 50 and 75 years old. Individuals with SBP<90 or >160 mmHg or DBP <50 or > 100 mm Hg were excluded. Other exclusion criteria were resistant hypertension or contraindications to high-sodium or low-sodium diet or special dietary requirements.

After enrollment, participants (n=213) first continued their usual diet for 7 days and where then randomized to first a high-sodium diet or low-sodium diet for 7 days. Participants on the high-sodium diet then crossed over to the low-sodium diet and vise versa. The high-sodium diet consisted of the usual diet + 2,200 mg sodium added/day. The low-sodium diet consisted of standardized meals with 500 mg sodium/day.

Main results

• The median age of the participants was 61 years, 65% were female and 64% self-identified as Black. 25% had normal BP, 20% controlled hypertension, 25% untreated hypertension, and 31% had uncontrolled hypertension. The median BMI was 31 kg/m² and 21% of participants had diabetes.
• The average sodium intake (measured by 24-hour urine sodium excretion) in the usual diet of the participants was 4450 mg/day, which is already very high in sodium. Measured sodium intake was 5000 mg/day during the high sodium diet and 1270 mg/day during the low-sodium diet.
• SBP during the usual diet was 125 mm Hg. During the high-sodium diet, SBP did not significantly change with a median increase of 1 mm Hg to 126 mm Hg (P=0.14). During the low-sodium diet, SBP decreased significantly to a median of 119 mm Hg (P<0.001).
• The average group difference in SBP between with low- compared with high-sodium diet at the end of the first diet week was 8 mm Hg (95%CI 4-11 mm Hg, P<0.0001). The reduction with the low-sodium diet was consistent across subgroups and between participants who had normal BP, controlled hypertension, untreated hypertension, and uncontrolled hypertension.
• 74.4% of participants experienced any reduction in SBP with the low-sodium diet compared with the high-sodium diet.
• Adverse events were reported by 9.9% of participants while on the high-sodium diet and by 8.0% of participants while on the low-sodium diet.

Conclusion

In middle-aged individuals, a low-sodium diet significantly lowered SBP already within a week compared to the participants’ usual diet. Addition of sodium did not raise systolic BP compared with the usual diet. A reduction in SBP with the low-sodium diet was observed in approximately 75% of individuals and the reduction in SBP with a low-sodium diet was independent of hypertension status and anti-hypertensive medication use.

- Our reporting is based on the information provided at the AHA Scientific Session 2023 -

The results of this study were simultaneously published in JAMA