Research reveals effect of dietary sodium on blood pressure

Dietary recommendations for sodium are debated in part because of the variable blood pressure response to sodium intake. Furthermore, the effect of dietary sodium on blood pressure in people taking antihypertensive drugs has not been adequately studied. The Doctors of the Therapeutic Clinic of the School of Medicine of the National and Kapodistrian University of Athens Theodora Psaltopoulou (Professor of Preventive Medicine and Epidemiology) and Yannis Danasis summarize the results of the recent study by DKGupta and colleagues published in the prestigious scientific journal JAMA.

The aim of this particular study was to examine the distribution of individual blood pressure response to dietary sodium intake; the difference in blood pressure between people who were allocated to eat a high- or low-sodium diet first, and whether the results differed by baseline blood pressure and use of antihypertensive drugs.

Overall, the US study involved 213 people aged 50 to 75, including people with normal blood pressure (25%), controlled hypertension (20%), uncontrolled hypertension (31%) and untreated hypertension (25%). ). Participants had a baseline visit while consuming their usual diet, and then followed high (approximately 2200 mg sodium added daily to the usual diet) and low (approximately 500 mg daily total) sodium diets for 1 week each. 118 subjects first followed a high-sodium diet, then a low-sodium diet, and 95 subjects first followed a low-sodium diet, then a high-sodium diet.

The mean age was 61 years, 65% were female, and 64% were black. The participants’ median systolic blood pressure readings were 125, 126, and 119 mm Hg for the usual diet, high-sodium diet, and low-sodium diet, respectively. The median individual change in mean blood pressure between the high- and low-sodium diets was 4 mm Hg (interquartile range, 0-8 mm Hg; statistically significant difference), regardless of hypertension status. Compared to the high-sodium diet, the low-sodium diet caused a decrease in mean blood pressure in 73.4% of subjects. The commonly used cutoff of a mean blood pressure reduction of 5 mm Hg or more between a high-sodium and a low-sodium diet classified 46% of subjects as “salt sensitive.”

At the end of the first week of dietary intervention, the mean difference in systolic blood pressure between subjects assigned to a high-sodium diet and a low-sodium diet was 8 mm Hg; which was similar across subgroups according to age, sex, race, hypertension, baseline blood pressure, presence of diabetes mellitus, and body mass index.

In conclusion, dietary sodium reduction significantly reduced blood pressure in most adults middle and old age. The reduction in blood pressure from a high- to low-sodium diet was independent of hypertension status and use of antihypertensive medication, for all patient subgroups without serious adverse events.