Associations between dietary fiber intake and cardiovascular risk factors: An umbrella review of meta-analyses of randomized controlled trials

Abstract

Although several meta-analyses have revealed the beneficial effects of dietary fiber intake on human health, some have reported inconsistent findings. The purpose of this work was to perform an umbrella meta-analysis to evaluate the relevant evidence and elucidate the effect of dietary fiber intake on glycemic control, lipid profiles, systematic inflammation, and blood pressure. Eligible studies were searched in several electronic databases, including Web of Science, PubMed, Scopus, and the Cochrane Library, up to March 2022. A total of 52 meta-analyses involving 47,197 subjects were identified to assess the pooled effect size. Overall, higher dietary fiber intake was significantly associated with reductions in parameters involving glycemic control, including fasting plasma glucose (ES = −0.55, 95% CI: −0.73, −0.38, P < 0.001), fasting plasma insulin (ES = −1.22, 95% CI: −1.63, −0.82, P < 0.001), homeostasis model assessment of insulin resistance (HOMA-IR) (ES = −0.43, 95% CI: −0.60, −0.27, P < 0.001), and glycosylated hemoglobin (HbA1c) (ES = −0.38, 95% CI: −0.50, −0.26, P < 0.001). In terms of lipid profiles, higher dietary fiber intake was associated with significant reductions in the serum level of total cholesterol (ES = −0.28, 95% CI: −0.39, −0.16, P < 0.001) and low-density lipoprotein cholesterol (ES = −0.25, 95% CI: −0.34, −0.16, P < 0.001), but not triglycerides (ES = −0.001, 95% CI: −0.006, 0.004, P = 0.759) and high-density lipoprotein cholesterol (ES = −0.002, 95% CI: −0.004, 0.000, P = 0.087). Higher dietary fiber intake was also significantly associated with improved tumor necrosis factor-alpha serum levels (ES = −0.78, 95% CI: −1.39, −0.16, P = 0.013), while no significant effect was observed for C-reactive protein (ES = −0.14, 95% CI: −0.33, 0.05, P = 0.156). Finally, blood pressure was also significantly improved following higher dietary fiber intake (systolic blood pressure: ES = −1.72, 95% CI: −2.13, −1.30, P < 0.001; diastolic blood pressure: ES = −0.67, 95% CI: −0.96, −0.37, P < 0.001). Subgroup analysis revealed that the study population and type of dietary fiber could be partial sources of heterogeneity. In conclusion, the present umbrella meta-analysis provides evidence for the role of dietary fiber supplementation in the improvement of established cardiovascular risk factors.

Effects of Nut Consumption on Blood Lipids and Lipoproteins: A Comprehensive Literature Update

“…In a meta-analysis of 67 clinical trials to quantify the cholesterol-lowering effect of dietary fiber, 2–10 g/d of soluble fiber was associated with modest but significant reductions in total cholesterol and LDL-C [ 47 ]. According to a recent umbrella meta-analysis, total dietary fiber (independently of type) also has cholesterol-lowering properties [ 48 ]. Dietary fiber, particularly soluble fiber, exerts its hypocholesterolemic effect through several mechanisms: (1) increased intestinal viscosity, which reduces bile acid absorption and promotes cholesterol catabolism; (2) enhanced synthesis of short-chain fatty acids by gut microbiota, particularly butyrate and propionate, which reduce de novo cholesterol synthesis via 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibition; and (3) interference with micelle formation in the intestinal lumen and enhanced fecal excretion of fat, cholesterol, and bile acids [ 48 ].…”

Pilot Study to Estimate Dietary Fiber Intake in Adults Residing in Chile

“…The protocol of this study was approved by the Scientific Ethics Committee of the Universidad San Sebastian (No. [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. All participants were fully informed and expressed their willingness to participate by signing the informed consent form.…”

“…SDF forms colloid solutions in the intestine, slows digestion and causes a prolonged feeling of satiety, while FDI accelerates intestinal transit, increasing stool volume, acting as a bulking agent and laxative and its food sources are nuts, legumes, whole wheat, barley and tubers [6]. Considering the above, DF is related to the promotion of mitigating effects on cholesterol and glucose levels [7,8], the latter being related to the onset of type 2 diabetes [9,10], obesity, colon cancer [11,12], and cardiovascular diseases [13,14]; it takes part in all the Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.…”

Carbohydrates for glycemic control: functional and microbiome aspects

“…Notwithstanding these recent increments in study numbers and power, there is still evidence of substantial heterogeneity in most pooled estimates; further long-term and high-quality RCTs are needed. The main points [17,18 ▪ ], which must contribute to the heterogeneity of the pooled studies are:…”