The effect of dietary fiber (oat bran) supplement on blood pressure in patients with essential hypertension: A randomized controlled trial

Background and aims: Insufficient dietary fiber (DF) intake is associated with increased blood pressure (BP) and the mode of action is unclear. The intake of DF supplements by participants in previous interventional studies was still far below the amount recommended by the World Health Organization. Therefore, this study aims to explore the effect of supplementing relatively sufficient DF on BP and gut microbiota in patients with essential hypertension (HTN). Methods and results: Fifty participants who met the inclusion criteria were randomly divided into the DF group (n = 25) and control group (n = 25). All the participants received education on regular dietary guidance for HTN. In addition to dietary guidance, one bag of oat bran (30 g/d) supplement (containing DF 8.9 g) was delivered to the DF group. The office BP (oBP), 24 h ambulatory blood pressure, and gut microbiota were measured at baseline and third month. After intervention, the office systolic blood pressure (oSBP; P < 0.001) and office diastolic blood pressure (oDBP; P < 0.028) in the DF group were lower than those in the control group. Similarly, the changes in 24hmaxSBP (P = 0.002), 24hmaxDBP (P = 0.001), 24haveSBP (P < 0.007), and 24haveDBP (P = 0.008) were greater in the DF group than in the control group. The use of antihypertensive drugs in the DF group was significantly reduced (P = 0.021). The b diversity, including Jaccard (P = 0.008) and Bray-Curtis distance (P = 0.004), showed significant differences (P < 0.05) between two groups by the third month. The changes of Bifidobacterium (P = 0.019) and Spirillum (P = 0.006) in the DF group were significant. Conclusions: Increased DF (oat bran) supplement improved BP, reduced the amount of antihypertensive drugs, and modulated the gut microbiota. Trial registration number: ChiCTR1900024055. (c) 2021 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved.