Could Probiotic Supplements Be an Effective Intervention to Reduce Hypertension? A Systematic Literature Review

Introduction: Pathogenesis of high blood pressure or hypertension is associated with microbial imbalance or dysbiosis of the gut microbiome. Previous research suggests probiotic consumption may reduce elevated blood pressure, possibly through manipulation of the gut microbiome, and may offer a future potential therapy for hypertension.
Aim: The aim of this research was to critically evaluate current research evidence to assess whether probiotic supplements may reduce high blood pressure and formulate recommendations regarding their use as an intervention to support hypertensive clients in a Nutritional Therapy context. The objectives were to outline the possible association between gut dysbiosis and hypertension, and to explore possible mechanisms by which probiotics may influence blood pressure.
Methods: A systematic review of the literature based upon PRISMA protocol was conducted. Four databases were searched: Cochrane Library (Central), CINAHL, Medline and TRIP from January 2014 until July 2020. Five eligible randomised controlled trials, including 453 participants, were identified and critically appraised to assess the quality of their evidence [1].
Results: Of the three highest quality studies, two supported probiotic supplements to be effective in reducing blood pressure, one study reported no effect. The remaining two studies were appraised to be of lesser methodological quality so were given less weighting for quality of evidence. This research study found moderate evidence that probiotic supplementation can significantly reduce blood pressure in individuals with borderline hypertension. No effect was reported in normotensives.
Conclusion: Probiotic supplementation may offer a convenient and effective adjunct for hypertensives to reduce high blood pressure alongside other dietary/lifestyle/medical interventions.
Recommendation: Further large-scale trials of longer duration on hypertensives are recommended to establish functional pathways, bacterial strain, dosage and required timescale.

Keywords:Probiotic Supplement; Hypertension; Dysbiosis; Blood Pressure; Gut microbiome

Abbreviations:ACE: Angiotensin-converting Enzyme; ACEI: ACE inhibitor; BASE: Bielefeld Academic Search Engine; BP: Blood pressure; CA: Critical appraisal; CINAHL: Cumulative Index of Nursing and Allied Health Literature; CONSORT: Consolidated Standards of Reporting of Trials; CFU: Colony Forming Units; CVD: Cardiovascular disease; DASH: Dietary Approaches to Stop Hypertension; DBP: Diastolic Blood Pressure; EC: Exclusion criteria; F/B: Firmicutes/Bacteroidetes; FMT: Faecal microbiota transplantation; GF: Germ free; GM: Gut microbiome; GPCR: G protein-coupled receptors; GRADE: Grading of Recommendations, Assessment, Development and Evaluation; HBP: High Blood Pressure; HT: Hypertensive(s); HTN: Hypertension; IC: Inclusion criteria; ITT: Intention-to-treat; LR: Literature review; MA: Meta-analysis; MECIR: Methodological Expectations of Cochrane Intervention Reviews; MeSH: Medical Subject Heading; Met-S: Metabolic syndrome; mmHg: millimetres of Mercury; NHS: National Health Service; NICE: National Institute for Health and Care Excellence; NO: Nitric oxide; NS: Narrative synthesis; NT: Normotension/normotensive; Pre- HT: Pre-hypertensive; Pre-HTN: Pre-hypertension; PRISMA: Preferred Reporting Items for Systematic Reviews and Meta-analyses; RAAS: Renin- Angiotensin-Aldosterone System; RCT: Randomised controlled trial; RO: Research objective; RoB: Risk of bias; RQ: Research question; SBP: Systolic Blood Pressure; SCFA: Short-chain fatty acid; SHR: Spontaneously hyperte