TY - JOUR
T1 - The role of diet in the prevention of hypertension and management of blood pressure
T2 - An umbrella review of meta-analyses of interventional and observational studies
AU - Aljuraiban, Ghadeer S.
AU - Gibson, Rachel
AU - Chan, Doris SM.
AU - Van Horn, Linda
AU - Chan, Queenie
N1 - Funding Information:
For each meta-analysis, the following data were extracted: first author, publication year, outcome (incidence hypertension, change in BP), intervention (any administration forms), comparison group (as defined in the RCTs), exposure, number of included primary studies, number of estimates, study design of the primary studies (RCTs, cohorts, case-control, cross-sectional), numbers of participants, number of cases (observational studies), health status of participants (normotensive, hypertensive, obesity, diabetes, or a mixture of health conditions), sex of participants, type of results (for example, high versus low or dose–response and its increment unit), heterogeneity (I2), method of analysis (random or fixed effects), estimates of effect or association and their 95% confidence interval (CI) and/or P value, risk of bias or quality score of primary studies, publication bias, and funding source and reported conflicts of interest.Two reviewers (GA and RG) independently assessed the quality of each selected meta-analysis, and a third reviewer (DC) resolved conflicting scores. Six quality aspects were evaluated for both RCTs and observational studies: 1) risk of bias, study quality, or study limitations; 2) precision of the estimate; 3) heterogeneity; 4) directness; 5) publication bias; 6) funding bias; with 7) study design for meta-analyses of RCTs only, and 8) effect size and 9) dose–response association for observational studies only. An overall score (maximum of 10 points) of 8 points, 6 to <8 points, 4 to <6 points, and <4 points represents high, moderate, low, and very low quality of evidence, respectively. A meta-analysis could be rated as high quality even when individual items such as risk of bias, heterogeneity, or publication bias did not achieve the highest score. Where the manuscript reported multiple outcomes (for example, markers of metabolic syndrome) and the authors did not separately report risk of bias or funding bias for BP or hypertension, we scored on the basis of what the authors reported for the composite of the outcomes (for example, all outcomes of metabolic syndrome). For the meta-analyses of observational studies that reported both comparing high to low dietary intake and dose–response results, NutriGrade would be scored for the results of high to low dietary intake only.This umbrella review of meta-analyses of RCTs and observational studies provides the first extensive and comprehensive overview that synthesizes and grades the strength of evidence of numerous dietary factors and changes in BP and risk of hypertension. We reviewed a total of 175 publications and reported 341 meta-analyses of RCTs and 70 meta-analyses of observational studies, using NutriGrade to assess the quality of each selected meta-analysis and AMSTAR 2 for a methodological quality of included publications. Meta-analyses of DASH dietary patterns showed that it was the most effective dietary pattern for reducing BP and its effect was comparable to antihypertensive pharmacological treatment, with similar findings for the Mediterranean diet. As part of our analyses, we found that the majority of studies investigating the relationship between dietary components and hypertension and BP were of poor-quality evidence or poorly reported. Despite this, the examined evidence supports the dietary guidelines recommended by several authoritative health bodies and highlights the relationship between BP and several other dietary factors.Meta-analyses of RCTs for DASH, very-low-carbohydrate ketogenic diet (DBP), flaxseed, nitrates (SBP), urinary potassium, multivitamins and multiminerals (DBP), steviol (DBP), products with live bacteria, nitrates (SBP), and grape and its products were graded as high confidence in the effect estimate using NutriGrade, and further research probably will not change the confidence in the effect estimate. This review shows that no meta-analyses of observational studies were graded as high, and very few were graded as moderate quality. Further research could add evidence on the confidence and may change the effect estimate of meta-analyses having low or very low quality. Likewise, the methodological quality assessed using AMSTAR 2 was graded as high in only 11 of the included publications (all RCTs), with a majority of publications graded as moderate (43% for RCTs publications and 66% for observation studies’ publications). The poor-quality assessments may be due to the lack of quantitative risk of bias assessment, selection bias, significant heterogeneity, a small number of primary studies (<5), BP considered as a surrogate marker, absence of a test for publication bias, unreported source of funding, or moderate effect sizes (for observational studies), while the poor reporting may be due to the absence of grey literature or list of excluded studies. Overall, our review found that risk of bias remains uncertain for most of the available trials owing to poor reporting. This point is particularly concerning given that the majority of the trials were conducted after the Consolidated Standards of Reporting Trials guidelines were first reported in 1993 and published in 1996 [210]. We also found high heterogeneity, which may be due to the differences in trial designs, comparison groups, study populations, and analysis methods.The effect and association of dietary patterns, food groups, single foods, beverages, macronutrients, and micronutrients with risk of hypertension and change in BP were previously examined in several published meta-analyses, but this umbrella review categorically supports recommended dietary guidelines involving the DASH and Mediterranean patterns, restricting sodium, with moderate alcohol intake, as indicated by mostly moderate-quality RCTs. To achieve high-quality evidence and provide strong recommendations, future studies should consider several topics with only low quality of evidence observed (that is, small number of studies, reported bias, etc.). Future studies should focus on exposures likely to be biologically associated with risk of hypertension and change in BP but currently showing that the quality of evidence is still low. Future research should also focus on new dietary factors that have not yet been investigated (or published) so far. It is worth noting that this paper primarily focuses on dietary variables and comparisons across studies, rather than the actual differences between BP levels on the basis of baseline variability. Nonetheless, the majority of the studies examined the intervention effect on the basis of the difference of changes of BP from baseline. Hence, Wilder's principle [250]—the expected difference in BP from the initial reading is higher if the initial BP reading is high—may be at play. In this regard, future studies should explore the potential influence of Wilder's principle by observing the actual differences between BP levels on the basis of baseline variability.
Publisher Copyright:
© 2023 The Authors
PY - 2024/1
Y1 - 2024/1
N2 - High blood pressure (BP) is a major pathological risk factor for the development of several cardiovascular diseases. Diet is a key modifier of BP, but the underlying relationships are not clearly demonstrated. This is an umbrella review of published meta-analyses to critically evaluate the wide range of dietary evidence from bioactive compounds to dietary patterns on BP and risk of hypertension. PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials were searched from inception until October 31, 2021, for relevant meta-analyses of randomized controlled trials or meta-analyses of observational studies. A total of 175 publications reporting 341 meta-analyses of randomized controlled trials (145 publications) and 70 meta-analyses of observational studies (30 publications) were included in the review. The methodological quality of the included publications was assessed using Assessment of Multiple Systematic Reviews 2 and the evidence quality of each selected meta-analysis was assessed using NutriGrade. This umbrella review supports recommended public health guidelines for prevention and control of hypertension. Dietary patterns including the Dietary Approaches to Stop Hypertension and the Mediterranean-type diets that further restrict sodium, and moderate alcohol intake are advised. To produce high-quality evidence and substantiate strong recommendations, future research should address areas where the low quality of evidence was observed (for example, intake of dietary fiber, fish, egg, meat, dairy products, fruit juice, and nuts) and emphasize focus on dietary factors not yet conclusively investigated.
AB - High blood pressure (BP) is a major pathological risk factor for the development of several cardiovascular diseases. Diet is a key modifier of BP, but the underlying relationships are not clearly demonstrated. This is an umbrella review of published meta-analyses to critically evaluate the wide range of dietary evidence from bioactive compounds to dietary patterns on BP and risk of hypertension. PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials were searched from inception until October 31, 2021, for relevant meta-analyses of randomized controlled trials or meta-analyses of observational studies. A total of 175 publications reporting 341 meta-analyses of randomized controlled trials (145 publications) and 70 meta-analyses of observational studies (30 publications) were included in the review. The methodological quality of the included publications was assessed using Assessment of Multiple Systematic Reviews 2 and the evidence quality of each selected meta-analysis was assessed using NutriGrade. This umbrella review supports recommended public health guidelines for prevention and control of hypertension. Dietary patterns including the Dietary Approaches to Stop Hypertension and the Mediterranean-type diets that further restrict sodium, and moderate alcohol intake are advised. To produce high-quality evidence and substantiate strong recommendations, future research should address areas where the low quality of evidence was observed (for example, intake of dietary fiber, fish, egg, meat, dairy products, fruit juice, and nuts) and emphasize focus on dietary factors not yet conclusively investigated.
UR - http://www.scopus.com/inward/record.url?scp=85176320499&partnerID=8YFLogxK
U2 - 10.1016/j.advnut.2023.09.011
DO - 10.1016/j.advnut.2023.09.011
M3 - Article
SN - 2161-8313
VL - 15
JO - Advances in Nutrition
JF - Advances in Nutrition
IS - 1
M1 - 100123
ER -
