2023-11-27 14:47:03
According to Santé Publique France, 90% of French people exceed the limit recommended by the World Health Organization of 5 g of salt per day. And the authority continues to encourage people to limit salt intake in the diet. Numerous randomized controlled trials have in fact shown the benefit of reducing consumption on blood pressure. But on the one hand, there is a variable individual sensitivity to salt, and on the other hand subjects under anti-hypertensive treatment have often been excluded from these trials. The effect of salt reduction in this population therefore remained poorly characterized.
The effect of salt consumption measured in normotensive and hypertensive people
An American team compared the effect of reducing salt consumption on the blood pressure of normotensive and hypertensive subjects, treated and untreated. To do this, the participants were randomized into two arms, one followed a high-salt diet for one week (addition of approximately 2,200 mg/day to the diet), then switched to a low-salt diet the following week (addition of approximately 500 mg/day). The other group followed the opposite route in parallel. Their systolic and diastolic BP were measured ambulatory over 24 hours at inclusion and at the end of each week of high- or low-salt diet. Compliance with the sodium diet was checked by urine test. Subjects with resistant hypertension were excluded.
An intra-individual variation of 4 mmHg
In total, 213 subjects aged 50 to 75 years included in the study were able to follow the two weeks of high- and low-sodium diets (median age 61 years, 65% women, 64% of African origin). Among them, 25% were normotensive, 20% had hypertension controlled under antihypertensive treatment, 31% had uncontrolled hypertension, and 25% had hypertension but were not treated.
The median intra-individual variation in mean BP, between week on a high-sodium diet and week on a low-sodium diet, was 4 mmHg (p<0.001). And this variation did not depend on whether the subjects were normotensive, hypertensive treated or not, controlled or not, nor on the class of antihypertensive taken.
When subjects switched to a low-sodium diet, a reduction in average BP was observed in 73.4% of participants. And when this drop was equal to or greater than 5 mmHg (classically used threshold), the subjects were classified as being sensitive to salt. This was the case for 46% of them.
Intergroup systolic BP reduced by 8 mmHg
At the end of the first week, mean systolic BP was 8 mmHg lower (p<0.001) in subjects who followed the low-salt diet compared to those who followed the high-salt diet. Similar results (-7 mmHg, p<0.001) were found at the end of the second week (following the crossover). And this difference was observed regardless of age, sex, ethnic origin, and with a greater effect in subjects who had a higher BP at inclusion or diabetes.
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