Background Dietary Patterns and the Time Course of the Blood Pressure Response to Low Sodium Intake
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See related article, pp 923–929
Among the clinical trials that have contributed the most to our understanding of the quantitative relationship between nutrients and blood pressure (BP), the DASH trial (Dietary Approaches to Stop Hypertension)1 and the related DASH-Sodium trial2 have a particular standing because of their rigorous design, organizational complexity, and achievements. The organizational setting of these trials was demanding because food preparation was done in special research kitchens according to a preestablished protocol and because the subjects, over 400 people with prehypertension or stage 1 hypertension in each of the trials, had to consume at least 1 meal a day at the study site. A brief recapitulation of the design and the main findings of DASH and DASH-Sodium studies is useful to appropriately frame the novel analyses of the DASH-Sodium trial published in this issue of the journal,3 which focuses on the time course of the response to the low-salt diet.
In the seminal DASH trial,1 the control diet (lasting 8 weeks) was the typical American diet of the nineties, that is, a diet low in K, Ca, Mg, and fiber, with fat providing 37% of the total calories (16% saturated fats) and protein providing 15%. The sodium content of this diet was fixed at 3 g. This was compared with a second diet of the same duration and sodium content (3 g) that included more fruits and vegetables and, hence, a higher K, Mg, and fiber intake. The third (key) diet was a combination diet or DASH diet which, like the second diet, included a high amount of fruits and vegetables but also exchanged high-fat for low-fat dairy products to reduce fats to 27% of the total calories (saturated fats to 6%). In the DASH diet, sodium content was also fixed at 3 …