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A recent study published in JAMA on November 11, 2023, presents groundbreaking findings regarding the impact of dietary sodium intake on blood pressure, particularly in middle-aged to elderly individuals. A decline in blood pressure (BP) going from a high- to a low-sodium diet was confirmed regardless of hypertension status and antihypertensive medications used, a crossover trial found.
This research is significant in the context of ongoing debates around dietary sodium recommendations and their variability in blood pressure response, especially among those on antihypertensive medications.
"For most middle-aged to elderly adults, dietary sodium reduction resulted in clinically meaningful BP lowering which was safely achieved within 1 week. The effect of dietary sodium reduction in BP is comparable to a commonly utilized first-line antihypertensive medication [such as] hydrochlorothiazide 12.5 mg daily," reported Deepak Gupta, MD, MSCI, of Vanderbilt University Medical Center in Nashville.
"We need to make it simple for participants to be successful with their diet," Gupta said during an AHA press conference. He cited structural barriers to lowering dietary sodium, which is added in high levels during industrial and commercial food preparation. One estimate puts roughly 70% of dietary sodium as coming from packaged, processed, and restaurant foods.
The FDA currently estimates that Americans eat on average about 3,400 mg of sodium per day. A couple of years ago, the FDA advised voluntary sodium reduction goals with the purpose of reducing average sodium intake in the U.S. to 3,000 mg/day, or 12% over 2.5 years.
The 2020-2025 Dietary Guidelines for Americans had gone further to recommend a limit of 2,300 mg of sodium daily for everyone 14 years and older.
Dr. Gupta continued, "Now, they didn't have kidney disease, they were not obese, they didn't have heart disease," acknowledged Bakris, who was not involved with the present study. Still, he maintained: "Do not underestimate the power of salt."
Study Design and Objectives
The study involved a prospectively allocated diet order with crossover among 213 participants aged 50 to 75 years, enrolled between April 2021 and February 2023 in two U.S. cities. It included individuals with varying blood pressure statuses: normotension (25%), controlled hypertension (20%), uncontrolled hypertension (31%), and untreated hypertension (25%). The participants underwent two dietary interventions:
- High-sodium diet: Approximately 2200 mg of sodium added daily to the usual diet.
- Low-sodium diet: Approximately 500 mg of total daily sodium.
What Were The Key Findings?
- Reduction in Systolic Blood Pressure: A week on a low-sodium diet resulted in an average 8 mm Hg reduction in systolic blood pressure compared to a high-sodium diet. This effect was comparable to what is commonly seen with first-line antihypertensive medication.
- Effect Across Different Hypertension Statuses: The decline in blood pressure due to a low-sodium diet was consistent across individuals, irrespective of their hypertension status or use of antihypertensive medications. About 73.4% of participants showed a decline in mean arterial pressure on the low-sodium diet. Importantly, 46% of individuals were classified as “salt sensitive,” experiencing a decline of 5 mm Hg or more in mean arterial pressure when switching from a high-sodium to a low-sodium diet.
- Adverse Events: The study reported mild adverse events, with 9.9% and 8.0% of individuals experiencing them while on the high- and low-sodium diets, respectively.
What Are The Implications of the Study?
Compared with the high-sodium diet, the low-sodium diet induced a drop in mean arterial pressure in 73.4% of individuals. Sodium reduction significantly lowered BP in the majority of middle-aged to elderly adults in this study. The decline in BP from a high-sodium diet to a low-sodium diet was independent of hypertension status and antihypertensive medication use, generally consistent across subgroups, and did not result in excess adverse events. In fact, adverse events were mild and similarly likely during the high- (9.9%) and low-sodium diet phases (8.0%). These were most commonly headaches, gastrointestinal side effects, and edema with the high-sodium diet, and cramping and weakness with the low-sodium diet.
The study's findings provide robust evidence supporting the reduction of dietary sodium as a crucial factor in managing blood pressure, a key risk factor for cardiovascular diseases. The significance of these results lies in their universality across different groups, regardless of hypertension status or medication use. This research reinforces the importance of dietary interventions in the management of blood pressure and highlights the potential of a low-sodium diet as an effective, non-pharmacological approach to controlling hypertension and reducing cardiovascular risk.