In a recent study published in JAMA, researchers evaluate individual blood pressure (BP) responses to dietary sodium variations and account for baseline BP and antihypertensive medication use in a various population.

Study: Effect of Dietary Sodium on Blood Pressure: A Crossover Trial. Image Credit: Brainslav Nenin / Shutterstock.com

Background 

In america, adults, especially the middle-aged and elderly, often devour a mean of three.5 grams of sodium day by day, which exceeds the U.S. Department of Health and Human Services, World Health Organization (WHO), and American Heart Association recommendations.

This habit, related to increased sodium-related deaths, affects blood pressure variably, thus making personalized dietary sodium management difficult. Moreover, many studies often exclude those on antihypertensive medications, further complicating understanding.

Additional research is required to know individual variability in BP responses to dietary sodium, especially amongst those on antihypertensive medications. Refining the definition and impact of salt sensitivity in diverse populations with various hypertension statuses can be crucial.

Concerning the study 

The Coronary Artery Risk Development in Young Adults (CARDIA) study was designed to explore the results of dietary sodium on blood pressure. All participants who were a part of this community-based, prospective, multicenter observational cohort provided their informed consent and were compensated for his or her participation.

The study, conducted between 2021 and 2023, included a various group of participants from various U.S. cities, balanced across sex, race, age, and education. The cohort included individuals between 50 and 75 years of age and included each CARDIA and non-CARDIA participants from Birmingham, Alabama, and Chicago, Illinois. 

Participants adhered to a high- and low-sodium weight loss program for one week and were monitored through 24-hour ambulatory blood pressure and urine collections. The diets, customized to every participant’s caloric needs, followed U.S. dietary guidelines specializing in potassium and calcium. The study protocol required 4 visits to the University of Alabama at Birmingham or Northwestern University field centers, each week apart.

A comprehensive evaluation of subgroups based on various demographic and clinical aspects was performed. The researchers also sought to discover any antagonistic events participants might experience through the dietary intervention.

Study findings 

In the current study, 281 individuals consented to participate, with 232 meeting the eligibility criteria. Of those individuals, 228 attended the initial baseline visit, and 213 accomplished each phases of the study involving low- and high-sodium diets.

Participants’ day by day diets were high in sodium, which was further increased by the high-sodium weight loss program and reduced by the low-sodium weight loss program. The high-sodium weight loss program increased sodium intake in comparison with the low-sodium and usual diets. This aspect of the study underscored the everyday dietary patterns and their modification potential.

The study’s primary final result, the salt sensitivity for BP (SSBP) for mean arterial pressure, revealed a median increase of 4 mm Hg when comparing the results of low- to high-sodium diets. This response remained consistent across various participant subgroups, no matter differences in baseline diastolic blood pressure. Interestingly, the SSBP didn’t vary in response to the sequence through which the diets were administered.

SSBP across individuals with different hypertension statuses was also explored, including those with normotension, controlled hypertension, untreated hypertension, and uncontrolled hypertension. The response to dietary sodium alterations remained similar across these groups, thus indicating a universal effect of sodium intake on blood pressure.

Investigation into the connection between different classes of antihypertensive drugs and SSBP found no significant associations. This remark suggests that the impact of dietary sodium on blood pressure just isn’t significantly influenced by these medications.

A major finding of the study was that the vast majority of the cohort experienced a decline in mean arterial pressure when switching from a high- to low-sodium weight loss program. Using established criteria for salt sensitivity, about 46% of participants were categorized as salt sensitive, whereas a smaller portion of the cohort exhibited inverse salt sensitivity.

Upon comparing the participants’ usual weight loss program with the low-sodium weight loss program, there was a notable reduction in day by day sodium intake. This reduction was related to a decrease in systolic blood pressure in most participants. Comparatively, while increasing sodium intake, the high-sodium weight loss program didn’t lead to significant changes in blood pressure.

A parallel-group evaluation revealed that individuals who began with a low-sodium weight loss program exhibited significantly lower systolic blood pressure by the tip of the primary week in comparison with those that began with a high-sodium weight loss program. This effect remained consistent across different subgroups, including sex, age, race, baseline blood pressure, and diabetes status.

The high-sodium weight loss program was related to symptoms reminiscent of headaches, gastrointestinal discomfort, and edema, whereas the low-sodium weight loss program was related to cramping and weakness. Nevertheless, these events were relatively infrequent, as they affected lower than 10% of participants on either weight loss program. This means that dietary changes in sodium intake, each high and low, were generally well-tolerated by the study’s diverse cohort.