Consumption of a High-fiber Diet Improves Systolic Blood Pressure and Vascular Endothelial Function and May Reduce Oxidative Stress in Middle-aged to Older Adults.

Aging is the primary risk factor for the development of cardiovascular diseases (CVD), largely due to increases in systolic blood pressure (SBP) and oxidative stress-related impairments in vascular endothelial function. Higher intake of dietary fiber is associated with reduced CVD risk. In healthy late middle-aged to older (MA/O) adults, limited evidence indicates high-fiber diet interventions improve SBP, but whether a high-fiber diet improves endothelial function with aging is unknown. We tested the hypothesis that a high-fiber diet would, in addition to reducing SBP, improve endothelial function and reduce oxidative stress in healthy MA/O adults. We performed a controlled feeding study in which 14 MA/O adults (8F/6M; age: 69 ± 5 years) consumed an isocaloric high-fiber diet (30-35 g/day) for 7 days. Diets also contained 60% total carbohydrates, 15% protein, 25% fat, and 12-15% sugar. Baseline (pre) measures were performed under habitual diet conditions (26 ± 6 g fiber/day). On days 0 (pre) and 7 (post) of the diet, endothelial cells were collected via venous endovascular biopsy, and endothelial function was assessed by brachial artery flow-mediated dilation (FMD) following 20 minutes of intravenous infusion of saline (volume control) or the antioxidant ascorbic acid (0.06 g/kg fat-free mass in 100 mL saline at 5 mL/min; N=12), to determine whether any improvements in endothelial functional following the high-fiber diet were due to reduced oxidative stress. Consumption of a high-fiber diet reduced SBP (pre vs. post: 120 ± 3 vs. 116 ± 3 mmHg, p<0.01) and improved endothelial function by ~30% (pre vs. post: 4.1 ± 0.5 vs. 5.3 ± 0.7 %, p=0.03). Abundance of nitrotyrosine (NT), a marker of oxidative stress, in endothelial cells from a subset of subjects (N=6) was lower after the high-fiber diet (pre vs. post: 0.43 ± 0.16 vs. 0.29 ± 0.12 A.U., p=0.08). At baseline, infusion of ascorbic acid increased FMD by 2.2 ± 0.7 %Δ units (p=0.01 vs. saline), indicating tonic suppression of endothelial function by oxidative stress under habitual diet conditions. Ascorbic acid still increased FMD post-high-fiber diet but to a lesser extent (+1.2 ± 0.6 %Δ units, p=0.06 vs. saline), and differences in FMD pre vs. post high-fiber diet were abolished by ascorbic acid (6.3 ± 0.9 vs. 6.6 ± 0.9 %, p=0.68). These data suggest that the high-fiber diet improved FMD in part by reducing oxidative stress. High-fiber diet consumption improves SBP in healthy MA/O adults with normal baseline levels and induces clinically significant improvements in FMD possibly via reductions in vascular oxidative stress and tonic oxidative stress-related suppression of endothelial function. These results suggest that a high-fiber diet may reduce CVD risk, at least in part, by mitigating increases in SBP and oxidative stress-related impairments in endothelial function with aging. © FASEB.

Citation

Abigail G Casso, Marissa L Burnsed-Torres, Kara L Lubieniecki, Matthew J Rossman, Emily C Adam, Hannah M Lally, Michel Chonchol, Kevin P Davy, Douglas R Seals, Vienna E Brunt. Consumption of a High-fiber Diet Improves Systolic Blood Pressure and Vascular Endothelial Function and May Reduce Oxidative Stress in Middle-aged to Older Adults. FASEB journal : official publication of the Federation of American Societies for Experimental Biology. 2022 May;36 Suppl 1

PMID: 35556012

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