Accepted Manuscript Influence of Dietary Approaches to Stop Hypertension (DASH) diet on blood pressure: a systematic review and meta-analysis on randomized controlled trials Parvane Saneei, Amin Salehi Abargouei, Ahmad Esmaillzadeh, Leila Azadbakht, PhD PII:
S0939-4753(14)00205-1
DOI:
10.1016/j.numecd.2014.06.008
Reference:
NUMECD 1318
To appear in:
Nutrition, Metabolism and Cardiovascular Diseases
Received Date: 22 November 2013 Revised Date:
26 May 2014
Accepted Date: 16 June 2014
Please cite this article as: Saneei P, Abargouei AS, Esmaillzadeh A, Azadbakht L, Influence of Dietary Approaches to Stop Hypertension (DASH) diet on blood pressure: a systematic review and metaanalysis on randomized controlled trials, Nutrition, Metabolism and Cardiovascular Diseases (2014), doi: 10.1016/j.numecd.2014.06.008. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Influence of Dietary Approaches to Stop Hypertension (DASH) diet on blood
RI PT
pressure: a systematic review and meta-analysis on randomized controlled trials
Parvane Saneei1, 2, Amin Salehi Abargouei1, 2, Ahmad Esmaillzadeh1, 2, Leila Azadbakht1, 2 1
Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
2
SC
Department of Community Nutrition, School of Nutrition and Food Science, Isfahan University of
M AN U
Medical Sciences, Isfahan, Iran
Running Title: DASH diet and Blood pressure Correspondence to:
AC C
Tables: 3
EP
TE D
Leila Azadbakht, PhD Department of Community Nutrition School of Nutrition and Food Science Isfahan University of Medical Sciences Isfahan, PO Box 81745-151 Iran Phone: +98 311 792-2719 Fax: +98 311 6681378 Email: [email protected]
Figures: 3
Supplementary figure: 1 Word count: 2998
Funding: Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. None of the authors had any personal or financial conflicts of interest.
1
ACCEPTED MANUSCRIPT
ABSTRACT
2
Background and Aims: Findings were not consistent on the therapeutic effect of Dietary
3
Approaches to Stop Hypertension (DASH) diet on blood pressure. We aimed to review
4
systematically and perform a meta-analysis to assess the magnitude of the effect of the DASH
5
diet on blood pressure in randomized controlled trials (RCTs) among adults.
6
Methods and Results: We conducted a systematic review and random effects meta-analysis of
7
all RCTs which evaluated the effect of the DASH diet on blood pressure including published
8
papers until June 2013, using PubMed, ISI Web of Science, Scopus and Google scholar database.
9
Subgroup analysis and meta-regression were used to find out possible sources of between-study
10
heterogeneity. Seventeen RCTs contributing 20 comparisons with 2561 participants were
11
included. Meta-analysis showed that the DASH diet significantly reduced systolic blood pressure
12
by 6.74 mmHg (95%CI: -8.25,-5.23, I2=78.1%) and diastolic blood pressure by 3.54 mmHg
13
(95%CI: -4.29,-2.79, I2=56.7%). RCTs with the energy restriction and those with hypertensive
14
subjects showed a significantly greater decrease in blood pressure. Meta-regression showed that
15
mean baseline of SBP and DBP was explained 24% and 49% of the variance between studies for
16
SBP and DBP, respectively.
17
Conclusion: The results revealed the profitable reducing effect of the DASH-like diet on both
18
systolic and diastolic blood pressure in adults; although there was a variation in the extent of the
19
fall in blood pressure in different subgroups.
20
KEYWORDS: DASH-diet, systolic blood pressure, diastolic blood pressure, randomized
21
controlled trials, meta-analysis
AC C
EP
TE D
M AN U
SC
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1
2
ACCEPTED MANUSCRIPT
INTRODUCTION
23
Hypertension is the leading cause of cardiovascular diseases and death in the world (1-2). It is
24
the most common cardiovascular disease that imposes a great burden to the healthcare system
25
(3). Currently, it affects nearly half of adults globally and its prevalence is increasing
26
dramatically among all age groups (4). Several strategies including lifestyle modifications and
27
medication use have been suggested for management of hypertension. Consumption of a healthy
28
diet has also been shown to be effective in controlling blood pressure (BP) and reducing
29
cardiovascular risks (5).
30
Dietary Approaches to Stop Hypertension (DASH) eating pattern, a diet rich in fruits, vegetables,
31
whole grains and low-fat dairy with a reduced content of sodium, saturated and total fat is
32
introduced as an appropriate diet for hypertension (6). Large number of studies has repeatedly
33
demonstrated that consumption of the DASH diet could decrease systolic BP (6-7); however, the
34
effects on diastolic BP have been conflicting (8-11). Furthermore, it seems that the significant
35
effect of DASH diet on blood pressure occurs only in hypertensive (8, 12-13), not in
36
normotensive adults (8-9, 14-15). In addition, it is not clear if the favorable effects of DASH diet
37
on blood pressure are due to energy restriction or its own content of beneficial nutrients. While
38
some trials on DASH diet have administered a hypo-caloric diet (10, 16-18), others prescribed no
39
energy restriction (6, 12). Therefore, it is not clear whether weight loss is the main reason for the
40
observed effects on BP or DASH diet could per se reduce BP independently. Furthermore, a
41
brief review of DASH trials has revealed that the macro- and micro-nutrient content of the
42
prescribed DASH diets in previous studies was not the same, particularly in terms of sodium
43
content (6, 12, 19-20). It remains unknown if the DASH diet with any amount of sodium could
44
influence BP or a specified amount of sodium is required to reach the favorable effects on BP.
AC C
EP
TE D
M AN U
SC
RI PT
22
3
ACCEPTED MANUSCRIPT
To the best of our knowledge, no systematic review or meta-analysis has been conducted to
46
summarize all the findings from earlier DASH trials including the magnitude of fall in systolic or
47
diastolic BP. Therefore, in the present study we aimed to review systematically the previous
48
reports and perform a meta-analysis to examine the magnitude of the effect of the DASH diet on
49
BP in randomized controlled trials (RCTs).
50
METHODS
51
We performed a systematic review and meta-analysis of RCTs that assessed the effects of DASH
52
diet on systolic and diastolic BP. This review was written in accordance with the preferred
53
reporting items for systematic reviews and meta-analyses (PRISMA) guideline (21).
54
Search strategy: A systematic search of relevant published papers until June 2013 was done
55
using PubMed, ISI Web of Science, Scopus and Google scholar databases. The following
56
keywords, selected from MeSH database, were used: ("DASH" OR "dietary approaches to stop
57
hypertension" OR “diet” OR "dietary pattern") AND ("blood pressure" OR "hypertension" OR
58
"lipid profile" OR "obesity" OR "weight" OR "triglyceride" OR "glucose" OR "diabetes" OR
59
"metabolic syndrome"). No language or time restriction was applied. In addition, the reference
60
list of the retrieved articles was searched to find other relevant articles. Two reviewers (PS and
61
ASA) independently screened the output of the search to identify potentially eligible studies.
62
Eligible studies: We included randomized controlled trials that examined the effect of DASH
63
diet on BP. The main outcomes of interest in trials were mean changes of systolic and diastolic
64
BP and their SDs in the DASH and control diets. In case of multiple publications and companion
65
papers from the same population, we included the study with the largest sample size. Post-hoc
66
analyses of other studies were not included.
AC C
EP
TE D
M AN U
SC
RI PT
45
4
ACCEPTED MANUSCRIPT
Excluded studies: We excluded studies that had reported the effect of DASH diet on BP in
68
children (22-24) and pregnant women with gestational diabetes mellitus (25-26). Some studies
69
that had compared other interventions to the DASH (like soy bean or low sodium vegetable juice
70
against the DASH) diet (as the control group) were excluded (27-30). Some studies had
71
investigated the effects of different forms of the DASH diet (in terms of macro-nutrients or
72
sodium) on BP were also excluded (31-37); since their control groups were consumed a DASH
73
diet. In three studies (9, 38-39), the DASH diet had been compared to a diet that included some
74
components of the DASH diet; as we targeted to contrast the effect of the DASH diet with a
75
control, we had to exclude these studies, too.
76
Thus, of the initial 1224 studies that were extracted from the search machines, 1143 were
77
excluded on the basis of the title or abstract. Of the remaining 81 studies, 64 were excluded for
78
the following reasons: duplicate publications and companion papers of a primary study or post-
79
hoc analysis (n=35), interventions on children (n=3), or on pregnant women with gestational
80
diabetes mellitus (n=2), the use of DASH diet as a control diet (n=4), intervention with different
81
forms of the DASH diet (n=10) and semi-experimental or before-after studies (n=8) (11, 14, 17-
82
19, 40-42). To further clarify the effect of DASH diet on blood pressure, we excluded two
83
studies that had not used random assignment (15, 43). Therefore, 17 studies were eligible for
84
inclusion in the meta-analysis (5-8, 10, 12-13, 16, 20, 44-51). Overall, 20 effect sizes were
85
extracted from 17 RCTs with a total of 2561 participants; 2 studies provided subgroup analyses
86
based on gender (7), and lean normotensive/obese hypertensive subjects (8). In addition one
87
study had provided two effect sizes for two DASH interventions with and without energy
88
restriction versus the control group (20). Two studies had reported effect sizes (ESs) separately
89
by hypertension status (12-13); hence we used ESs of subgroups in stratifying analysis by
AC C
EP
TE D
M AN U
SC
RI PT
67
5
ACCEPTED MANUSCRIPT
hypertension status. Among 20 extracted ESs, 17 were from parallel RCTs and 3 were obtained
91
in cross-over RCTs. The flow diagram of study selection process is indicated in Figure 1.
92
Data extraction: Two authors (PS and ASA) extracted data independently using a standard form
93
and then resolved differences by discussion with the third author (LA). When necessary, data
94
were requested from the authors. We extracted the following information from the papers: year
95
of publication, the name of first author, mean age (SD) of participants in each group, the number
96
of participants and their gender, health status (the presence of hypertension, metabolic syndrome,
97
diabetes), study design (parallel, crossover), prescribed energy (with energy limitation, without
98
energy limitation), type of the DASH and control diet, type of intervention performance (feeding,
99
non-feeding or diet prescription, other lifestyle interventions along with the dietary intervention),
100
changes in weight and duration of the intervention. All reported SEs, 95% confidence intervals,
101
and interquartile ranges were converted to SDs. For one study that reported P values instead of
102
effect sizes (47); the effect sizes were computed.
103
Statistical analyses: The mean and standard deviation (SD) of changes in SBP and DBP were
104
used for the meta-analysis. Using a random effects model that takes between-study variation into
105
account, the overall effect size was calculated. Between-study heterogeneity was assessed using
106
Cochran’s Q-test and I2. We used subgroup analysis and meta-regression to find out possible
107
sources of heterogeneity. Between-subgroup heterogeneity was examined through fixed effects
108
model. Sensitivity analysis was done to explore for the extent to which inferences might depend
109
on a particular study. To assess the presence of publication bias, the “Begg’s funnel plot” and
110
Egger’s test were used. Statistical analyses were conducted using STATA version 11.2 (STATA
111
Corp., College Station, Texas). P values less than 0.05 were considered statistically significant.
112
RESULTS
AC C
EP
TE D
M AN U
SC
RI PT
90
6
ACCEPTED MANUSCRIPT
Among 1224 identified publications, 17 papers were eligible for the present meta-analysis.
114
Study characteristics: Studies included in this systematic review are summarized in Table 1. In
115
total 17 RCTs (5-8, 10, 12-13, 16, 20, 44-51), included 2561 participants with individual study
116
sizes ranging from 12 to 542. The duration of intervention varied from 2 to 26 weeks in studies.
117
There were 1747 participants with hypertension, 293 without hypertension, and 521 with
118
undisclosed hypertensive status at baseline of trials. The intervention in 12 RCTs was dietary
119
advice or education to use DASH diet while 5 RCTs supplied participants with the food items of
120
the DASH diet. Eight studies have applied energy restriction and 8 others did not use energy
121
restriction; one study has applied two intervention groups: a group with energy restriction and
122
another group without energy restriction versus the control group.
123
Findings from systematic review: All 20 effect sizes extracted from 17 RCTs revealed a
124
beneficial effect of the DASH diet on SBP, as compared with the control diet. The reductions in
125
SBP in studies ranged from -1.67 to -12.7 mmHg. With regards to DBP, all effect sizes revealed
126
a favorable effect with reductions ranged from -1.20 to -10.20 mmHg. It is noteworthy that some
127
of these effect sizes were not statistically significant.
128
Findings from meta-analysis: The meta-analysis on 17 studies contributing 20 comparisons
129
indicated that the consumption of the DASH diet significantly reduced SBP by 6.74 mmHg
130
(95%CI: -8.25,-5.23) (Figure 2) and DBP by 3.54 mmHg (95%CI: -4.29,-2.79) (Figure 3).
131
However, between-study heterogeneity was significant for both SBP (Cochran's Q, P
S0939-4753(14)00205-1
DOI:
10.1016/j.numecd.2014.06.008
Reference:
NUMECD 1318
To appear in:
Nutrition, Metabolism and Cardiovascular Diseases
Received Date: 22 November 2013 Revised Date:
26 May 2014
Accepted Date: 16 June 2014
Please cite this article as: Saneei P, Abargouei AS, Esmaillzadeh A, Azadbakht L, Influence of Dietary Approaches to Stop Hypertension (DASH) diet on blood pressure: a systematic review and metaanalysis on randomized controlled trials, Nutrition, Metabolism and Cardiovascular Diseases (2014), doi: 10.1016/j.numecd.2014.06.008. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Influence of Dietary Approaches to Stop Hypertension (DASH) diet on blood
RI PT
pressure: a systematic review and meta-analysis on randomized controlled trials
Parvane Saneei1, 2, Amin Salehi Abargouei1, 2, Ahmad Esmaillzadeh1, 2, Leila Azadbakht1, 2 1
Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
2
SC
Department of Community Nutrition, School of Nutrition and Food Science, Isfahan University of
M AN U
Medical Sciences, Isfahan, Iran
Running Title: DASH diet and Blood pressure Correspondence to:
AC C
Tables: 3
EP
TE D
Leila Azadbakht, PhD Department of Community Nutrition School of Nutrition and Food Science Isfahan University of Medical Sciences Isfahan, PO Box 81745-151 Iran Phone: +98 311 792-2719 Fax: +98 311 6681378 Email: [email protected]
Figures: 3
Supplementary figure: 1 Word count: 2998
Funding: Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran. None of the authors had any personal or financial conflicts of interest.
1
ACCEPTED MANUSCRIPT
ABSTRACT
2
Background and Aims: Findings were not consistent on the therapeutic effect of Dietary
3
Approaches to Stop Hypertension (DASH) diet on blood pressure. We aimed to review
4
systematically and perform a meta-analysis to assess the magnitude of the effect of the DASH
5
diet on blood pressure in randomized controlled trials (RCTs) among adults.
6
Methods and Results: We conducted a systematic review and random effects meta-analysis of
7
all RCTs which evaluated the effect of the DASH diet on blood pressure including published
8
papers until June 2013, using PubMed, ISI Web of Science, Scopus and Google scholar database.
9
Subgroup analysis and meta-regression were used to find out possible sources of between-study
10
heterogeneity. Seventeen RCTs contributing 20 comparisons with 2561 participants were
11
included. Meta-analysis showed that the DASH diet significantly reduced systolic blood pressure
12
by 6.74 mmHg (95%CI: -8.25,-5.23, I2=78.1%) and diastolic blood pressure by 3.54 mmHg
13
(95%CI: -4.29,-2.79, I2=56.7%). RCTs with the energy restriction and those with hypertensive
14
subjects showed a significantly greater decrease in blood pressure. Meta-regression showed that
15
mean baseline of SBP and DBP was explained 24% and 49% of the variance between studies for
16
SBP and DBP, respectively.
17
Conclusion: The results revealed the profitable reducing effect of the DASH-like diet on both
18
systolic and diastolic blood pressure in adults; although there was a variation in the extent of the
19
fall in blood pressure in different subgroups.
20
KEYWORDS: DASH-diet, systolic blood pressure, diastolic blood pressure, randomized
21
controlled trials, meta-analysis
AC C
EP
TE D
M AN U
SC
RI PT
1
2
ACCEPTED MANUSCRIPT
INTRODUCTION
23
Hypertension is the leading cause of cardiovascular diseases and death in the world (1-2). It is
24
the most common cardiovascular disease that imposes a great burden to the healthcare system
25
(3). Currently, it affects nearly half of adults globally and its prevalence is increasing
26
dramatically among all age groups (4). Several strategies including lifestyle modifications and
27
medication use have been suggested for management of hypertension. Consumption of a healthy
28
diet has also been shown to be effective in controlling blood pressure (BP) and reducing
29
cardiovascular risks (5).
30
Dietary Approaches to Stop Hypertension (DASH) eating pattern, a diet rich in fruits, vegetables,
31
whole grains and low-fat dairy with a reduced content of sodium, saturated and total fat is
32
introduced as an appropriate diet for hypertension (6). Large number of studies has repeatedly
33
demonstrated that consumption of the DASH diet could decrease systolic BP (6-7); however, the
34
effects on diastolic BP have been conflicting (8-11). Furthermore, it seems that the significant
35
effect of DASH diet on blood pressure occurs only in hypertensive (8, 12-13), not in
36
normotensive adults (8-9, 14-15). In addition, it is not clear if the favorable effects of DASH diet
37
on blood pressure are due to energy restriction or its own content of beneficial nutrients. While
38
some trials on DASH diet have administered a hypo-caloric diet (10, 16-18), others prescribed no
39
energy restriction (6, 12). Therefore, it is not clear whether weight loss is the main reason for the
40
observed effects on BP or DASH diet could per se reduce BP independently. Furthermore, a
41
brief review of DASH trials has revealed that the macro- and micro-nutrient content of the
42
prescribed DASH diets in previous studies was not the same, particularly in terms of sodium
43
content (6, 12, 19-20). It remains unknown if the DASH diet with any amount of sodium could
44
influence BP or a specified amount of sodium is required to reach the favorable effects on BP.
AC C
EP
TE D
M AN U
SC
RI PT
22
3
ACCEPTED MANUSCRIPT
To the best of our knowledge, no systematic review or meta-analysis has been conducted to
46
summarize all the findings from earlier DASH trials including the magnitude of fall in systolic or
47
diastolic BP. Therefore, in the present study we aimed to review systematically the previous
48
reports and perform a meta-analysis to examine the magnitude of the effect of the DASH diet on
49
BP in randomized controlled trials (RCTs).
50
METHODS
51
We performed a systematic review and meta-analysis of RCTs that assessed the effects of DASH
52
diet on systolic and diastolic BP. This review was written in accordance with the preferred
53
reporting items for systematic reviews and meta-analyses (PRISMA) guideline (21).
54
Search strategy: A systematic search of relevant published papers until June 2013 was done
55
using PubMed, ISI Web of Science, Scopus and Google scholar databases. The following
56
keywords, selected from MeSH database, were used: ("DASH" OR "dietary approaches to stop
57
hypertension" OR “diet” OR "dietary pattern") AND ("blood pressure" OR "hypertension" OR
58
"lipid profile" OR "obesity" OR "weight" OR "triglyceride" OR "glucose" OR "diabetes" OR
59
"metabolic syndrome"). No language or time restriction was applied. In addition, the reference
60
list of the retrieved articles was searched to find other relevant articles. Two reviewers (PS and
61
ASA) independently screened the output of the search to identify potentially eligible studies.
62
Eligible studies: We included randomized controlled trials that examined the effect of DASH
63
diet on BP. The main outcomes of interest in trials were mean changes of systolic and diastolic
64
BP and their SDs in the DASH and control diets. In case of multiple publications and companion
65
papers from the same population, we included the study with the largest sample size. Post-hoc
66
analyses of other studies were not included.
AC C
EP
TE D
M AN U
SC
RI PT
45
4
ACCEPTED MANUSCRIPT
Excluded studies: We excluded studies that had reported the effect of DASH diet on BP in
68
children (22-24) and pregnant women with gestational diabetes mellitus (25-26). Some studies
69
that had compared other interventions to the DASH (like soy bean or low sodium vegetable juice
70
against the DASH) diet (as the control group) were excluded (27-30). Some studies had
71
investigated the effects of different forms of the DASH diet (in terms of macro-nutrients or
72
sodium) on BP were also excluded (31-37); since their control groups were consumed a DASH
73
diet. In three studies (9, 38-39), the DASH diet had been compared to a diet that included some
74
components of the DASH diet; as we targeted to contrast the effect of the DASH diet with a
75
control, we had to exclude these studies, too.
76
Thus, of the initial 1224 studies that were extracted from the search machines, 1143 were
77
excluded on the basis of the title or abstract. Of the remaining 81 studies, 64 were excluded for
78
the following reasons: duplicate publications and companion papers of a primary study or post-
79
hoc analysis (n=35), interventions on children (n=3), or on pregnant women with gestational
80
diabetes mellitus (n=2), the use of DASH diet as a control diet (n=4), intervention with different
81
forms of the DASH diet (n=10) and semi-experimental or before-after studies (n=8) (11, 14, 17-
82
19, 40-42). To further clarify the effect of DASH diet on blood pressure, we excluded two
83
studies that had not used random assignment (15, 43). Therefore, 17 studies were eligible for
84
inclusion in the meta-analysis (5-8, 10, 12-13, 16, 20, 44-51). Overall, 20 effect sizes were
85
extracted from 17 RCTs with a total of 2561 participants; 2 studies provided subgroup analyses
86
based on gender (7), and lean normotensive/obese hypertensive subjects (8). In addition one
87
study had provided two effect sizes for two DASH interventions with and without energy
88
restriction versus the control group (20). Two studies had reported effect sizes (ESs) separately
89
by hypertension status (12-13); hence we used ESs of subgroups in stratifying analysis by
AC C
EP
TE D
M AN U
SC
RI PT
67
5
ACCEPTED MANUSCRIPT
hypertension status. Among 20 extracted ESs, 17 were from parallel RCTs and 3 were obtained
91
in cross-over RCTs. The flow diagram of study selection process is indicated in Figure 1.
92
Data extraction: Two authors (PS and ASA) extracted data independently using a standard form
93
and then resolved differences by discussion with the third author (LA). When necessary, data
94
were requested from the authors. We extracted the following information from the papers: year
95
of publication, the name of first author, mean age (SD) of participants in each group, the number
96
of participants and their gender, health status (the presence of hypertension, metabolic syndrome,
97
diabetes), study design (parallel, crossover), prescribed energy (with energy limitation, without
98
energy limitation), type of the DASH and control diet, type of intervention performance (feeding,
99
non-feeding or diet prescription, other lifestyle interventions along with the dietary intervention),
100
changes in weight and duration of the intervention. All reported SEs, 95% confidence intervals,
101
and interquartile ranges were converted to SDs. For one study that reported P values instead of
102
effect sizes (47); the effect sizes were computed.
103
Statistical analyses: The mean and standard deviation (SD) of changes in SBP and DBP were
104
used for the meta-analysis. Using a random effects model that takes between-study variation into
105
account, the overall effect size was calculated. Between-study heterogeneity was assessed using
106
Cochran’s Q-test and I2. We used subgroup analysis and meta-regression to find out possible
107
sources of heterogeneity. Between-subgroup heterogeneity was examined through fixed effects
108
model. Sensitivity analysis was done to explore for the extent to which inferences might depend
109
on a particular study. To assess the presence of publication bias, the “Begg’s funnel plot” and
110
Egger’s test were used. Statistical analyses were conducted using STATA version 11.2 (STATA
111
Corp., College Station, Texas). P values less than 0.05 were considered statistically significant.
112
RESULTS
AC C
EP
TE D
M AN U
SC
RI PT
90
6
ACCEPTED MANUSCRIPT
Among 1224 identified publications, 17 papers were eligible for the present meta-analysis.
114
Study characteristics: Studies included in this systematic review are summarized in Table 1. In
115
total 17 RCTs (5-8, 10, 12-13, 16, 20, 44-51), included 2561 participants with individual study
116
sizes ranging from 12 to 542. The duration of intervention varied from 2 to 26 weeks in studies.
117
There were 1747 participants with hypertension, 293 without hypertension, and 521 with
118
undisclosed hypertensive status at baseline of trials. The intervention in 12 RCTs was dietary
119
advice or education to use DASH diet while 5 RCTs supplied participants with the food items of
120
the DASH diet. Eight studies have applied energy restriction and 8 others did not use energy
121
restriction; one study has applied two intervention groups: a group with energy restriction and
122
another group without energy restriction versus the control group.
123
Findings from systematic review: All 20 effect sizes extracted from 17 RCTs revealed a
124
beneficial effect of the DASH diet on SBP, as compared with the control diet. The reductions in
125
SBP in studies ranged from -1.67 to -12.7 mmHg. With regards to DBP, all effect sizes revealed
126
a favorable effect with reductions ranged from -1.20 to -10.20 mmHg. It is noteworthy that some
127
of these effect sizes were not statistically significant.
128
Findings from meta-analysis: The meta-analysis on 17 studies contributing 20 comparisons
129
indicated that the consumption of the DASH diet significantly reduced SBP by 6.74 mmHg
130
(95%CI: -8.25,-5.23) (Figure 2) and DBP by 3.54 mmHg (95%CI: -4.29,-2.79) (Figure 3).
131
However, between-study heterogeneity was significant for both SBP (Cochran's Q, P
