Low-sodium diet delivers rapid BP-lowering effect

In the CARDIA-SSBP study, low sodium intake led to a rapid reduction in blood pressure (BP) in middle-aged individuals.

About 75 percent of participants – including those on antihypertensives – had reduced systolic BP (SBP) within a week of adhering to a low-sodium diet. “[This] indicates that lowering BP through dietary sodium reduction can be achieved safely and rapidly,” said Dr Deepak Gupta from Vanderbilt University Medical Center, Nashville, Tennessee, US, at AHA 2023.

SBP dropped in participants with low sodium intake compared with those on a high-sodium diet (median 7 mm Hg; p<0.001) and with those following their usual diet (median 6 mm Hg). The 6-mm Hg reduction mirrored the average effect achieved with hydrochlorothiazide, a commonly used first-line antihypertensive, Gupta noted.

“High BP is the most common chronic condition in the world, and for most adults, dietary sodium intake influences BP,” said Gupta. “However, dietary sodium recommendations are debated in part due to variable BP response to sodium consumption.”

The team conducted a randomized crossover trial comprising 213 CARDIA* and non-CARDIA participants (median age 61 years, 65 percent female, 73 percent from CARDIA). They were randomized to a high-sodium (~2,200 mg added to usual daily diet) or low-sodium diet (~500 mg daily) for a week. They then switched to the opposite diet for another week. Twenty-five percent of participants were normotensive while the rest were hypertensive (20 percent controlled, 31 percent uncontrolled, 25 percent untreated).

Ambulatory BP was measured over a 24-hour period on the last day of each diet. Median SBP measurements were 125, 126, and 119 mm Hg for the usual, high- and low-sodium diet groups, respectively. Usual diets, which were typically high in sodium (median 4,450 mg daily), were adjusted to medians of 5,000 and 1,270 mg daily in the respective high- and low-sodium diet groups. [JAMA 2023;doi:10.1001/jama.2023.23651]

Adverse event (AE) rates were similar in the high- and low-sodium diet groups (9.9 percent vs 8.0 percent) and were mostly mild and self-limiting.

Any reduction is better than none

Of note, the BP drop with low sodium intake was independent of hypertension status and antihypertensive medication use, consistent across subgroups, and did not result in excess AEs.

“This reinforces the importance of reducing dietary sodium intake to help control BP, even among individuals already [on antihypertensives],” Gupta said. “Just as any physical activity is better than none for most people, any sodium reduction from the current usual diet is likely better than none.”

“Our study also supports the AHA’s position that consuming excess sodium beyond recommended levels is associated with increasing BP,” Gupta added.

The AHA recommends no more than 2,300 mg of sodium daily, with an ideal limit of <1,500 mg daily for most adults, especially for those with hypertension. [www.heart.org/-/media/files/health-topics/answers-by-heart/why-should-i-limit-sodium.pdf, accessed November 15, 2023] However, it is estimated that most individuals cross these boundaries and consume more than the recommended intake; some are even unaware that they do.

Dr George Bakris from the University of Chicago, Illinois, US, who was unaffiliated with the study, shared an anecdote in a press conference at AHA 2023. “Two patients referred to me by cardiologists [were apparently resistant to antihypertensives] … When we measured their sodium intake … they were on 10 grams a day but had no clue.”

“[I]t’s really important that we now think about doing something with these results,” said discussant Dr Cheryl Anderson from the University of California, San Diego, California, US.

Although most individuals tend to stick to dietary habits they’ve been accustomed to, “if [they can] accomplish sodium targets wherever they live, work, learn, play, or pray, it really will take a change in the food system,” Anderson said.