Fibre supplement could reduce hypertension

An Australian trial into the effect of a specialised fibre-enriched diet in patients with hypertension resulted in a significant reduction in systolic blood pressure.

The study, published in Nature Cardiovascular Research, was designed to produce evidence that specific types of fibre fermented by the gut microbiota in the colon — producing metabolites called short-chain fatty acids (SCFAs), predominantly acetate, butyrate and propionate — are instrumental in lowering BP.¹

Twenty participants with hypertension completed the phase II, randomised, placebo-controlled, double-blind trial using prebiotic acetylated and butyrylated high-amylose maize starch (HAMSAB) supplementation.²

The baseline mean ± s.d. 24-hour systolic blood pressure (SBP) was 136 ± 6 mmHg, and diastolic blood pressure (DBP) was 87 ± 7 mmHg. Participants randomised to either the placebo or HAMSAB had no significant differences in age, sex, BMI, 24-hour BP or biochemical profiles.

They received 40 g per day of HAMSAB or placebo — corn starch or regular flour with no added resistant starches — completing each arm for three weeks, with a three-week washout period between them.

HAMSAB and placebo diets were matched in macronutrient content, including protein, fat and carbohydrates. The only difference was in overall dietary fibre.

No differences in SBP were observed in the placebo arm. In the HAMSAB arm, a decrease in 24-hour SBP with a placebo-subtracted mean difference of –6.1 mmHg was observed without any adverse effects.

Fecal microbiome analysis supported the hypothesis that HAMSAB treatment fosters the expansion of microbes that produce SCFAs in conjunction with releasing high levels of the pre-conjugated acetate and butyrate.

The authors note that no change in stroke volume, cardiac output or heart rate was observed; however, HAMSAB significantly reduced total vascular resistance.

The study authors concluded that HAMSAB increased levels of acetate and butyrate, shifted the microbial ecosystem and expanded the prevalence of SCFA producers.

The reduction in SBP observed was equivalent to that achieved with conventional anti-hypertensive mono-treatment³ and is calculated to reduce coronary death by 9% and stroke death by 14%⁴.

In summary, a prebiotic intervention with HAMSAB could represent a promising option to deliver SCFAs and lower blood pressure in patients with essential hypertension.

^{1 Maslowski, K. M. & Mackay, C. R. Diet, gut microbiota and immune responses. Nat. Immunol. 12, 5–9 (2011)}

^{2 Rhys-Jones, D. et al. Microbial interventions to control and reduce blood pressure in Australia (MICRoBIA): rationale and design of a double-blinded randomised cross-over placebo controlled trial. Trials 22, 496 (2021)}

^{3 Heran, B. S., Wong, M. M., Heran, I. K. & Wright, J. M. Blood pressure lowering efficacy of angiotensin converting enzyme (ACE) inhibitors for primary hypertension. Cochrane Database Syst. Rev. CD003823 (2008)}

^{4 Stamler, J. et al. INTERSALT study findings. Public health and medical care implications. Hypertension 14, 570–577 (1989)}

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