Abstract
Background & aims:
Increased fruit and vegetable consumption (FVC) beneficially impacts hypertension, yet researchers have not synthesized the effects of FVC interventions on blood pressure (BP) among overweight or obese individuals. Therefore, we aimed to examine if diets with increased FVC decrease BP in overweight and obese persons and explore effects of moderators, study methods, participants, intervention, and source characteristics.
Methods:
A thorough literature search was conducted in CINAHL, ProQuest Dissertation & Theses, Scopus, PubMed, The Cochrane Library, and Web of Science. Last search was conducted on February 28, 2020. Inclusion criteria consisted of randomized controlled trials, an increased FVC intervention, and a body mass index (BMI) ≥25. Studies were independently coded and evaluated for bias using Cochrane Collaboration's tool for assessing study bias. The Grading of Recommendations Assessment, Development and Evaluation tool was used to evaluate the body of evidence, which was found to be moderate. Data was analyzed using Stata 16SE Software. We used a random effects model, comparing mean differences. Moderator analysis was conducted using meta-regression for continuous variables and meta-analytic ANOVA analog for categorical variables. Publication bias was assessed using funnel plot symmetry, Begg and Mazumdar's rank and correlation, Egger's test of the intercept, and Duval and Tweedie's trim and fill.
Results:
Ten studies met criteria, which included 6862 participants. Overall, effects of FVC interventions on systolic blood pressure (SBP) was 2.16 mmHg (p < 0.001) and -0.55 mmHg (p = 0.39) for diastolic blood pressure (DBP). Moderator analyses showed greater drops in SBP from samples recruited from the community and medical schools (vs. health care/programs), interventions that used the DASH diet, and measured intake with food diaries. When concealed allocation was used and fidelity checked, there were less decreases in SBP than when it was not used. The amount of FVC significantly moderated the effects of SBP and DBP with greater increased FVC leading to greater decreases in SBP and DBP.
Discussion:
Our findings are encouraging in that FVC improves blood pressure. However, outcomes are limited by the small number of studies that met inclusion criteria, significant heterogeneity, possible publication bias, and several studies had quality concerns. Tests for publication bias indicated none and most heterogeneity among studies was explained with moderator analysis our findings should be interpreted with caution.
Conclusions:
Increased FVC decreased SBP and DBP in obese and overweight individuals which may lower the risk of cardiovascular events. In the future, researchers might conduct higher quality studies and report quality indicators. Researchers might examine the effects of interventions for specific subgroups (overweight vs obese, younger vs older) and explore the impacts of diet-assisted technologies.
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