The demographic profile of the 354 participants who completed all seven diet acceptability questionnaires was similar to the 412 participants (14
) who were enrolled in the trial (data not shown), resulting in an 86% response rate. Incomplete or nonrespondents (n=58) had similar demographic characteristics as complete respondents (n=354) with respect to age, BMI, sex, race, and hypertension status (data not shown), but were less likely to have had some college education (70% of incomplete or nonrespondents had some college education compared with 85% of complete respondents, P
<0.01). Participants assigned to the DASH (n=180) and control diets (n=174) had similar baseline characteristics. Women made up 61% of the DASH group and 55% of the control group, and African Americans made up 56% of the DASH group and 59% of the control group. Mean age was 47.8 years for the DASH group and 49.2 years for the control group, and mean BMI was 28.9 and 29.5, respectively. Forty-one percent of DASH participants and 39% of control participants had hypertension, and at least some college education was attained by 89% of the DASH group and 81% of the control group.
Adherence was high. Mean attendance at onsite week-day meals was 92% at each sodium level for DASH participants and 91%, 93%, and 91% for control participants at higher, intermediate, and lower sodium levels, respectively. Based on daily self-reported checklists that included both weekday and weekend days, DASH and control participants on average were compliant (defined as missing no meals, eating only study foods, and eating no extra nonstudy foods) 91% and 92% of the time, respectively. These percentages were virtually identical for all three sodium levels in each diet group. In addition, 24-hour urine collections showed that across all sodium levels participants on the DASH diet had higher mean excretions of potassium (3,003 to 3,237 vs 1,560 to 1,599 mg/day [77 to 83 vs 40 to 41 mmol/day]), phosphorus (785 to 831 vs 645 to 670 mg/day [253 to 268 vs 208 to 216 mmol/day]), and urea nitrogen (11.8 to 12.6 vs 9.6 to 10.1 g/day [0.42 to 0.45 vs 0.34 to 0.36 mol/day]) than participants receiving the control diet. The mean sodium levels achieved by the participants based on 24-hour urinary excretions, which reflect a range of energy levels, were similar in each diet group: 3,312, 2,461, and 1,495 mg/day (144, 107, and 65 mmol/day) for the DASH group and 3,266, 2,415, and 1,403 mg/day (142, 105, and 61 mmol/day) for the control group at higher, intermediate, and lower sodium levels, respectively.
Salt and Overall Diet Acceptability by Sodium Level
Participants in each diet group successfully distinguished between the three different levels of sodium (). Participants in each diet group consistently gave the highest acceptability ratings to the intermediate sodium level (range in P values for differences between intermediate and either lower or higher sodium levels in all eight possible comparisons: 0.01 to 0.0001). Overall, differences in salt acceptability scores were not dramatic between sodium levels for either diet: approximately one point. There was no difference in salt acceptability between the higher and lower sodium level, except with the DASH diet, where the higher sodium level received a poorer score than the lower sodium level for willingness to continue with this level of saltiness (4.3 vs 4.9, P=0.02).
Ratings from the salt and diet acceptability questionnaire administered at end of 30 days of receiving a given sodium level
For the overall diet, participants in both diet groups gave the highest acceptability scores to the intermediate salt level, although statistical significance was achieved in only three of eight possible comparisons with the intermediate level (intermediate vs lower sodium P values: 0.01 to 0.0004). For liking the overall diet, DASH and control participants gave the next highest acceptable rating to the higher sodium level (P=0.04 and 0.02, respectively, for higher vs lower sodium). There were no significant differences between higher and lower sodium levels for willingness to continue. Differences in overall diet acceptability scores were generally small between sodium levels for both diets: approximately one-half point.
Change in Salt Acceptability with Time
We found no significant change in acceptability of sodium level with either the DASH or control diet during the 4 weeks that participants were on each of the three sodium levels (data not shown).
Acceptability of DASH Compared with Control Diet
At all sodium levels, compared with the control diet, participants on the DASH diet liked their overall diet more (by 0.9, 0.7, and 0.8 points for lower, intermediate, and higher sodium levels, respectively, P<0.05 to <0.005), and were more willing to continue that diet (by 0.9, 1.1, and 1.2 points, respectively, P<0.01 to <0.0001). Range in mean ratings (unadjusted for run-in) was 5.6 to 6.6 for the DASH diet and 5.2 to 6.1 for the control diet. Participants on the DASH diet also rated more highly at all sodium levels the components of the DASH diet compared with control diet participants. For fruits and vegetables, mean ratings ranged from 7.3 to 7.4 for the DASH diet and 5.4 to 5.7 for the control diet. For dairy, mean ratings ranged from 6.3 to 6.4 for the DASH diet and 5.3 to 5.5 for the control diet. Specifically, compared with control diet participants and adjusted for run-in, DASH diet participants rated higher: the amount of fruits and vegetables by 2.3, 2.0, and 2.1 points for lower, intermediate, and higher sodium levels (all P<0.0001); willing to continue that level of fruits and vegetables by 1.9, 1.9, and 2.0 points, respectively (all P<0.0001); amount of dairy by 1.4, 1.4, and 1.2 points, respectively (all P<0.0001); and willing to continue that amount of dairy by 1.7, 1.4, and 1.2 points, respectively (all P≤0.0001). Interaction terms of diet with sodium level were not significant.
Results of Subgroup Analyses
There were no significant differences in ratings between subgroups defined by obesity, age, sex, and hypertension status. There were significant differences in acceptability by race.
Salt Acceptability According to Sodium Levels by Race Subgroups
Within-race subgroup comparisons showed similar patterns to those reported in , namely, for both races and both diets, the intermediate salt level was almost always rated higher than either the lower or higher sodium level (significant for 75% [12 out of 16] of the comparisons, see , upper half).
Salt acceptability and overall diet acceptability ratings and differences between sodium levels as reported by African Americans and non-African Americansa
African Americans and non-African Americans receiving the DASH diet did not differ in salt acceptability (, upper half), but there were race differences for the control diet. Among those receiving the control diet, the second most acceptable salt level for African Americans was the higher sodium level, whereas non-African Americans receiving the control diet ranked the lower sodium level as the second most acceptable. Of six possible comparisons, racial differences in salt acceptability ratings (liking and willingness to continue) for the control diet were significant for four comparisons (lower vs intermediate and lower vs higher; average difference among six scores was about one point). Differences between African Americans and non-African Americans in overall diet acceptability ratings on the control diet (liking and willingness to continue) were smaller than those for salt acceptability; just two out of six possible between-race subgroup comparisons—lower vs intermediate—attained statistical significance (average difference in scores was about one-half point).
Acceptability of the DASH Diet and Its Components by Race Subgroups
At all sodium levels, African Americans and non-African Americans liked the DASH diet to a similar extent (, lower half). Diet acceptability scores ranged from 5.5 to 6.5 for African Americans and 5.8 to 6.7 for non-African Americans. In contrast, diet acceptability scores on the control diet ranged from 5.8 to 6.8 for African Americans but only 4.0 to 5.0 for non-African Americans (range in P values for between-race differences: 0.03 to <0.0001). Thus, the higher acceptability of the DASH diet compared with the control diet was seen only in non-African Americans.
Acceptability scores for the number of servings of the key food groups that define the DASH dietary pattern (eg, fruits and vegetables, low-fat dairy products) in both African Americans and non-African Americans were almost always higher on the DASH diet than control diet (significant for more than 75% [19 out of 24] of the comparisons, see ). Scores were similar between African Americans and non-African Americans receiving the DASH diet at all three sodium levels (about 0.1 point different for fruits and vegetables and about 0.3 point different for dairy servings). Compared with non-African Americans, African Americans were more accepting of and gave higher scores to the number of servings of fruits and vegetables and dairy products provided in the control diet. All 12 between-race comparisons were significant (range in P values: 0.0004 to <0.0001). Thus, the magnitude of acceptability for the DASH diet features compared with the control diet was greater for non-African Americans than for African Americans.
Diet component acceptability ratings by sodium level and differences between diet groups: African Americans and non-African Americansa