Lower sodium could reduce blood pressure in most people

The study suggests that reducing salt in the diet could have health benefits for many people. Santi Nunez / Stocksy/ Adobe Stock

Half of all Americans have high blood pressure, or hypertension. Blood pressure is considered high when systolic readings (the top number, the pressure when blood is pumped out of the heart) are consistently over 130 mm Hg or diastolic readings (the bottom number, between heartbeats when the heart is filling with blood) are 80 mm Hg or higher.

Although sodium is crucial to the human body, too much contributes to high blood pressure. The sensitivity of blood pressure to sodium, however, varies from person to person. This makes it difficult to determine what counts as a healthy amount of sodium in someone’s diet. Also, most studies of low-sodium diets have excluded people taking blood pressure-lowering medications. So, it isn’t clear how much reducing sodium intake would affect people taking these medications.

An NIH-funded research team led by Dr. Deepak Gupta at Vanderbilt University Medical Center studied the effect of dietary sodium on blood pressure in 213 people, ages 50-75 (65% women and 64% Black). Participants with both normal and high blood pressures were enrolled between April 2021 and February 2023 in Chicago, Illinois and Birmingham, Alabama. Some were taking medication to control their high blood pressure.

The participants were randomly assigned to a high- or low-sodium diet for a week. Those on the high-sodium diet added 2,200 mg of sodium per day to their usual diets. Those on the low-sodium diet were provided with a week’s worth of low-sodium meals, snacks, and beverages. The diet provided an average of 500 mg of sodium per day.

The researchers measured participants’ blood pressures after a week. Then the participants switched to the other diet for a week, and their blood pressures were measured again. Blood pressures were averages of measurements taken over 24 hours during normal daily activities. The results appeared in JAMA on November 11, 2023.

Nearly 75% of participants had lower systolic blood pressure on the low-sodium diet than on the high-sodium diet, with an average drop of 7 mm Hg. Compared with their usual diets, 72% of the participants had lower systolic blood pressure on the low-sodium diet, with an average drop of 6 mm Hg. The effect of dietary sodium didn’t depend on whether a person had high blood pressure to begin with. It also wasn’t affected by whether they were on medication for high blood pressure.

These reductions in blood pressure could have significant health benefits. The findings support lowering dietary sodium to reduce blood pressure. The effect of the low-sodium diet was like that of a common first-line medication for high blood pressure. The results also suggest that less sodium could help a wide range of people, including those who are already taking blood pressure-lowering medications.

“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,” Gupta says.

—by Brian Doctrow, Ph.D.