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Effect of Dietary Fiber on Serum Leptin Level: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.
Hassanzadeh-Rostami, Z, Faghih, S
Experimental and clinical endocrinology & diabetes : official journal, German Society of Endocrinology [and] German Diabetes Association. 2021;(4):322-333
Abstract
BACKGROUND Dietary fibers may induce satiety through affecting gastro-intestinal and peripheral appetite regulating hormones. Thus, we aimed to investigate the effect of dietary fiber consumption on serum leptin level compared to control diet, in short- and long- term trials, through a systematic review and meta-analysis. METHODS We searched PubMed, web of science, Scopus, ProQuest, EMBASE, and Cochrane Library to find randomized controlled clinical trials that evaluated effect of any type of dietary fiber on serum leptin level compared to control diet, until April 2019. Both short-term (1-4 days) and long-term (longer than 2 weeks) studies were selected. Mean differences (MD) of changes in serum leptin level and 95% confidence intervals were extracted from eligible studies, and random effects model was used to analyze data. RESULTS Thirteen studies included the systematic review and 11 entered in the meta-analysis. No significant change was seen in serum leptin level in short-term (MD=0.02, 95% CI; -0.15, 0.20, Tau2=0.0) and long-term studies (MD=-0.10, 95% CI; -0.28, 0.08, Tau2=0.0), followed by fiber consumption. However, this effect was statistically significant in obese participants (MD=-0.36, 95% CI; -0.71, -0.02, Tau2=0.0) in long-term studies. Moreover, we found no significant results in subgroups of baseline serum leptin level, intervention duration, fiber dose, and fiber type. CONCLUSIONS This meta-analysis found that taking dietary fiber for long term could lower serum leptin level, just in obese persons. However, further clinical trials are needed in this field to clarify this issue.
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Effects of soluble fiber supplementation on glycemic control in adults with type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials.
Xie, Y, Gou, L, Peng, M, Zheng, J, Chen, L
Clinical nutrition (Edinburgh, Scotland). 2021;(4):1800-1810
Abstract
BACKGROUND & AIMS Soluble dietary fiber is prompted as an important part of reducing blood glucose, ameliorating insulin resistance and controlling body weight. Thus, we performed this systematic review and meta-analysis of randomized controlled trials (RCTs) to quantify and synthesize the effects of soluble fiber supplementation on glycemic control and BMI modification in adults with type 2 diabetes. METHODS We searched MEDLINE, Embase, Web of Science, ClinicalTrials.gov, and Cochrane databases until February 13, 2020 to identify RCTs that detected the effects of soluble fiber supplementation on glycemic control in adults with type 2 diabetes. A random-effects model with the generic inverse variance method was used to analyze the pooled data. The meta-regression and subgroup analyses were conducted to identify the variables that influenced the pooled results. The robust error meta-regression model was used to conduct the dose-response test. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system was undertaken to evaluate the overall quality of the evidence. RESULTS A total of 29 RCTs (33 comparisons) involving 1517 participants were identified in this meta-analysis. Results showed that supplemental soluble dietary fiber significantly reduced glycosylated hemoglobin (HbA1c, MD -0.63%, 95% CI [-0.90, -0.37]; P < 0.00001), fasting plasma glucose (FPG, MD -0.89 mmol/L, 95% CI [-1.28, -0.51]; P < 0.00001), fasting insulin (SMD -0.48, 95% CI [-0.80, -0.17]; P = 0.003), homeostatic model assessment of insulin resistance (HOMA-IR, SMD -0.58, 95% CI [-0.86, -0.29], P < 0.0001), fructosamine (SMD -1.03, 95% CI [-1.51, -0.55]; P < 0.0001), 2-h postprandial plasma glucose (SMD -0.74, 95% CI [-1.00, -0.48]; P < 0.00001), and BMI (SMD -0.31, 95% CI [-0.61, -0.00], P = 0.05) compared with control diets in patients with type 2 diabetes. Specifically, dose-response meta-analyses presented that a daily dosage of 7.6-8.3 g was recommended. CONCLUSION Intake of soluble fiber supplementation is effective in improving glycemic control and BMI level in type 2 diabetes and is also a convenient way to help individuals meet standard dietary fiber needs. But due to the evidence of substantial heterogeneity in most pooled estimates, further long-term and high-quality RCTs are needed.
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The Role of Dietary Fibre in Modulating Gut Microbiota Dysbiosis in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.
Ojo, O, Feng, QQ, Ojo, OO, Wang, XH
Nutrients. 2020;(11)
Abstract
BACKGROUND The prevalence of type 2 diabetes is on the increase worldwide, and it represents about 90% of adults who are diagnosed with diabetes. Overweight and obesity, lifestyle, genetic predisposition and gut microbiota dysbiosis have been implicated as possible risk factors in the development of type 2 diabetes. In particular, low intake of dietary fibre and consumption of foods high in fat and sugar, which are common in western lifestyle, have been reported to contribute to the depletion of specific bacterial taxa. Therefore, it is possible that intake of high dietary fibre may alter the environment in the gut and provide the needed substrate for microbial bloom. AIM: The current review is a systematic review and meta-analysis which evaluated the role of dietary fibre in modulating gut microbiota dysbiosis in patients with type 2 diabetes. METHODS This is a systematic review and meta-analysis of randomised controlled trials which relied on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework. Electronic searches were conducted using EBSCOHost with links to Health Sciences Research Databases, EMBASE and Google Scholar. The reference lists of articles were also searched for relevant studies. Searches were conducted from date of commencement of the database to 5 August 2020. The search strategy was based on the Population, Intervention, Comparator, Outcomes, Studies (PICOS) framework and involved the use of synonyms and medical subject headings (MesH). Search terms were combined with Boolean operators (OR/AND). RESULTS Nine studies which met the inclusion criteria were selected for the systematic review and meta-analysis, and four distinct areas were identified: the effect of dietary fibre on gut microbiota; the role of dietary fibre on short-chain fatty acids (SCFAs); glycaemic control; and adverse events. There was significant difference (p < 0.01) in the relative abundance of Bifidobacterium with a mean difference of 0.72 (95% CI, 0.56, 0.89) between the dietary fibre group compared with placebo. In relation to the meta-analysis for SCFAs, while there was significant difference (p = 0.02) between the dietary fibre group and placebo with a standardised mean difference of 0.5 (95% CI, 0.08, 0.91) regarding total SCFAs, the differences were not significant (p > 0.05) in relation to acetic acid, propionic acid and butyric acid. There was only significant improvement (p = 0.002) with respect to glycated haemoglobin with a mean difference of -0.18 (95% CI, -0.29, -0.06) between the dietary fibre group and placebo group. Differences between the two groups were not significant (p > 0.05) in relation to fasting blood glucose and homeostatic model assessment of insulin resistance (HOMA-IR). Furthermore, there were no significant differences between the two groups in subjects who reported adverse events. It is possible that the promotion of SCFA producers in greater diversity and abundance by dietary fibre in this review led to improvement in glycated haemoglobin, partly due to increased glucagon-like peptide-1 (GLP-1) production. In addition, Bifidobacterium lactis has been reported to increase glycogen synthesis, decrease expression of hepatic gluconeogenesis genes, improve translocation of glucose transport-4 and promote glucose uptake. It is also possible that the reduction in body weight of participants in the intervention group compared with control may have contributed to the observed improvement in glycated haemoglobin. CONCLUSION This systematic review and meta-analysis have demonstrated that dietary fibre can significantly improve (p < 0.05) the relative abundance of Bifidobacterium, total SCFAs and glycated haemoglobin. However, dietary fibre did not appear to have significant effect (p > 0.05) on fasting blood glucose, HOMA-IR, acetic acid, propionic acid, butyric acid and adverse events.
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Can dietary viscous fiber affect body weight independently of an energy-restrictive diet? A systematic review and meta-analysis of randomized controlled trials.
Jovanovski, E, Mazhar, N, Komishon, A, Khayyat, R, Li, D, Blanco Mejia, S, Khan, T, L Jenkins, A, Smircic-Duvnjak, L, L Sievenpiper, J, et al
The American journal of clinical nutrition. 2020;(2):471-485
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Abstract
BACKGROUND The role of dietary fiber in obesity management remains debatable. Evidence suggests that intake of viscous fiber may have the potential to facilitate weight loss. OBJECTIVE We aimed to summarize and quantify the effects of viscous fiber on body weight, BMI, waist circumference, and body fat, independent of calorie restriction, through a systematic review and meta-analysis of randomized controlled trials. METHODS Trials ≥4 wk in duration that assessed the effect of viscous fiber supplemented to an ad libitum diet along with comparator diets were included. MEDLINE, EMBASE, and the Cochrane library were searched through 24 July, 2019. Two independent reviewers extracted relevant data. Data were pooled using the generic inverse variance method and random-effects models and expressed as mean differences with 95% CIs. Interstudy heterogeneity was assessed (Cochran Q statistic) and quantified (I2 statistic). The overall certainty of evidence was explored using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. RESULTS Findings from 62 trials (n = 3877) showed that viscous fiber reduced mean body weight (-0.33 kg; 95% CI: -0.51, -0.14 kg; P = 0.004), BMI (in kg/m2) (-0.28; 95% CI: -0.42, -0.14; P = 0.0001), and waist circumference (-0.63 cm; 95% CI: -1.11, -0.16 cm; P = 0.008), with no change in body fat (-0.78%; 95% CI: -1.56%, 0.00%; P = 0.05) when consumed with an ad libitum diet. Greater reductions in body weight were observed in overweight individuals and those with diabetes and metabolic syndrome. The certainty of evidence was graded moderate for body weight, high for waist circumference and body fat, and low for BMI. CONCLUSIONS Dietary viscous fiber modestly yet significantly improved body weight and other parameters of adiposity independently of calorie restriction. Future trials are warranted to address the inconsistency and imprecision identified through GRADE and to determine long-term weight-loss sustainability.This systematic review and meta-analysis was registered at clinicaltrials.gov as NCT03257449.
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Dietary fibre intake and the risk of diverticular disease: a systematic review and meta-analysis of prospective studies.
Aune, D, Sen, A, Norat, T, Riboli, E
European journal of nutrition. 2020;(2):421-432
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BACKGROUND A high intake of dietary fibre has been associated with a reduced risk of diverticular disease in several studies; however, the dose-response relationship between fibre intake and diverticular disease risk has varied, and the available studies have not been summarised in a meta-analysis. We conducted a systematic review and meta-analysis of prospective cohort studies to clarify the association between dietary fibre intake, fibre subtypes, and the risk of diverticular disease. METHODS PubMed and Embase databases were searched up to August 9th 2018. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using a random-effects model and nonlinear associations were modelled using fractional polynomial models. RESULTS Five prospective cohort studies with 19,282 cases and 865,829 participants were included in the analysis of dietary fibre and diverticular disease risk. The summary RR was 0.74 (95% CI 0.71-0.78, I2 = 0%) per 10 g/day. There was no evidence of a nonlinear association between dietary fibre intake and diverticular disease risk, pnonlinearity = 0.35, and there was a 23%, 41% and 58% reduction in risk for an intake of 20, 30, and 40 g/day, respectively, compared to 7.5 g/day. There was no evidence of publication bias with Egger's test, p = 0.58 and the association persisted in subgroup and sensitivity analyses. The summary RR per 10 g/day was 0.74 (95% CI 0.67-0.81, I2 = 60%, n = 4) for cereal fibre, 0.56 (95% CI 0.37-0.84, I2 = 73%, n = 2) for fruit fibre, and 0.80 (95% CI 0.45-1.44, I2 = 87%, n = 2) for vegetable fibre. CONCLUSIONS These results suggest that a high fibre intake may reduce the risk of diverticular disease and individuals consuming 30 g of fibre per day have a 41% reduction in risk compared to persons with a low fibre intake. Further studies are needed on fibre types and risk of diverticular disease and diverticulitis.
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Grain and dietary fiber intake and bladder cancer risk: a pooled analysis of prospective cohort studies.
Yu, EYW, Wesselius, A, Mehrkanoon, S, Brinkman, M, van den Brandt, P, White, E, Weiderpass, E, Le Calvez-Kelm, F, Gunter, M, Huybrechts, I, et al
The American journal of clinical nutrition. 2020;(5):1252-1266
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BACKGROUND Higher intakes of whole grains and dietary fiber have been associated with lower risk of insulin resistance, hyperinsulinemia, and inflammation, which are known predisposing factors for cancer. OBJECTIVES Because the evidence of association with bladder cancer (BC) is limited, we aimed to assess associations with BC risk for intakes of whole grains, refined grains, and dietary fiber. METHODS We pooled individual data from 574,726 participants in 13 cohort studies, 3214 of whom developed incident BC. HRs, with corresponding 95% CIs, were estimated using Cox regression models stratified on cohort. Dose-response relations were examined using fractional polynomial regression models. RESULTS We found that higher intake of total whole grain was associated with lower risk of BC (comparing highest with lowest intake tertile: HR: 0.87; 95% CI: 0.77, 0.98; HR per 1-SD increment: 0.95; 95% CI: 0.91, 0.99; P for trend: 0.023). No association was observed for intake of total refined grain. Intake of total dietary fiber was also inversely associated with BC risk (comparing highest with lowest intake tertile: HR: 0.86; 95% CI: 0.76, 0.98; HR per 1-SD increment: 0.91; 95% CI: 0.82, 0.98; P for trend: 0.021). In addition, dose-response analyses gave estimated HRs of 0.97 (95% CI: 0.95, 0.99) for intake of total whole grain and 0.96 (95% CI: 0.94, 0.98) for intake of total dietary fiber per 5-g daily increment. When considered jointly, highest intake of whole grains with the highest intake of dietary fiber showed 28% reduced risk (95% CI: 0.54, 0.93; P for trend: 0.031) of BC compared with the lowest intakes, suggesting potential synergism. CONCLUSIONS Higher intakes of total whole grain and total dietary fiber are associated with reduced risk of BC individually and jointly. Further studies are needed to clarify the underlying mechanisms for these findings.
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Role of dietary fibre in older adults with asymptomatic (AS) or symptomatic uncomplicated diverticular disease (SUDD): Systematic review and meta-analysis.
Eberhardt, F, Crichton, M, Dahl, C, Nucera, R, Jenkins, J, Marx, W, Marshall, S
Maturitas. 2019;:57-67
Abstract
Dietary fibre and probiotics may play a role in the management of diverticular disease. This systematic review synthesises the evidence on the effects of dietary fibre modifications, with or without the use of probiotics, on the incidence in older adults of asymptomatic (AS) or symptomatic uncomplicated diverticular disease (SUDD), as well as on gastrointestinal function and symptoms. Five electronic databases were searched for studies through to December 2018. The body of evidence was appraised using the Cochrane Risk of Bias tool and GRADE. Nine studies were included, with mean sample ages ranging from 57 to 70 years, and three meta-analyses were performed. Only one study, with high risk of bias, measured the effect of dietary fibre on the incidence of diverticulitis. Dietary fibre supplementation improved stool weight (MD: 42 g/day, P < 0.00001; GRADE level of evidence: low), but had no significant effect on gastrointestinal symptoms (SMD: -0.13, P = 0.16; GRADE level of evidence: low) or stool transit time (MD: -3.70, P = 0.32 GRADE level of evidence: low). There was "very low" confidence for the body of evidence supporting symbiotics for AS or SUDD. A high dietary fibre intake, in line with dietary guidelines, may improve gastrointestinal function and is recommended in patients with AS or SUDD. Dietary fibre supplementation should be considered on an individualised basis to improve bowel function, while any recommendation on symbiotic supplements requires further well-designed research. Future studies should also measure the impact on the incidence of diverticulitis.
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Effects of β-Fructans Fiber on Bowel Function: A Systematic Review and Meta-Analysis.
de Vries, J, Le Bourgot, C, Calame, W, Respondek, F
Nutrients. 2019;(1)
Abstract
The aim of this systematic review and meta-analysis was to assess the effects of β-fructan supplementation on bowel function in healthy volunteers and patients. The search process was based on the selection of publications listed in the Pubmed and EUPMC database until December 2017, plus two unpublished studies, to identify studies evaluating the impact of β-fructans on bowel movement and stool parameters. Forty-seven publications were selected for inclusion. Primary parameter was frequency of bowel movements, evaluated by the number of defecations per day during the study period. Secondary outcomes were stool consistency, stool dry and wet weights, and transit time. Short-chain (DP < 10) β-fructans contributed to increased stool frequency (0.36 defecation +/- 0.06 per day; p < 0.001), while no significant effect was reported with long-chain (DP ≥ 10) β-fructans (-0.03 +/- 0.11, p = 0.82). A minimal increase in stool wet weight was also statistically demonstrated with short-chain β-fructans. Moreover, the meta-analysis highlighted significant differences in stool consistency in contrast to fecal dry weight after β-fructan supplementation. This systematic review and meta-analysis indicates that short-chain β-fructan supplementation has a positive effect on bowel function by significantly increasing the frequency of bowel movements.
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Different dietary fibre sources and risks of colorectal cancer and adenoma: a dose-response meta-analysis of prospective studies.
Oh, H, Kim, H, Lee, DH, Lee, A, Giovannucci, EL, Kang, SS, Keum, N
The British journal of nutrition. 2019;(6):605-615
Abstract
Dietary fibre is believed to provide important health benefits including protection from colorectal cancer. However, the evidence on the relationships with different dietary fibre sources is mixed and little is known about which fibre source provides the greatest benefits. We conducted a dose-response meta-analysis of prospective cohorts to summarise the relationships of different fibre sources with colorectal cancer and adenoma risks. Analyses were restricted to publications that reported all fibre sources (cereals, vegetables, fruits, legumes) to increase comparability between results. PubMed and Embase were searched through August 2018 to identify relevant studies. The summary relative risks (RR) and 95 % CI were estimated using a random-effects model. This analysis included a total of ten prospective studies. The summary RR of colorectal cancer associated with each 10 g/d increase in fibre intake were 0·91 (95 % CI 0·82, 1·00; I2 = 0 %) for cereal fibre, 0·95 (95 % CI 0·87, 1·03, I2 = 0 %) for vegetable fibre, 0·91 (95 % CI 0·78, 1·06, I2 = 43 %) for fruit fibre and 0·84 (95 % CI 0·63, 1·13, I2 = 45 %) for legume fibre. For cereal fibre, the association with colorectal cancer risk remained statistically significant after adjustment for folate intake (RR 0·89, 95 % CI 0·80, 0·99, I2 = 2 %). For vegetable and fruit fibres, the dose-response curve suggested evidence of non-linearity. All fibre sources were inversely associated with incident adenoma (per 10 g/d increase: RR 0·81 (95 % CI 0·54, 1·21) cereals, 0·84 (95 % CI 0·71, 0·98) for vegetables, 0·78 (95 % CI 0·65, 0·93) for fruits) but not associated with recurrent adenoma. Our data suggest that, although all fibre sources may provide some benefits, the evidence for colorectal cancer prevention is strongest for fibre from cereals/grains.
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Should Viscous Fiber Supplements Be Considered in Diabetes Control? Results From a Systematic Review and Meta-analysis of Randomized Controlled Trials.
Jovanovski, E, Khayyat, R, Zurbau, A, Komishon, A, Mazhar, N, Sievenpiper, JL, Blanco Mejia, S, Ho, HVT, Li, D, Jenkins, AL, et al
Diabetes care. 2019;(5):755-766
Abstract
OBJECTIVE Evidence from randomized controlled trials (RCTs) suggests that viscous dietary fiber may offer beneficial effects on glycemic control and, thus, an improved cardiovascular disease risk profile. Our purpose was to conduct a systematic review and meta-analysis of RCTs to synthesize the therapeutic effect of viscous fiber supplementation on glycemic control in type 2 diabetes. RESEARCH DESIGN AND METHODS MEDLINE, Embase, and Cochrane Central Register of Controlled Trials were searched through 15 June 2018. We included RCTs ≥3 weeks in duration that assessed the effects of viscous fiber on markers of glycemic control in type 2 diabetes. Two independent reviewers extracted data. Data were pooled using the generic inverse variance method and expressed as mean differences (MD) with 95% CIs. Heterogeneity was assessed (Cochran Q statistic) and quantified (I 2 statistic). The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to evaluate the overall certainty of the evidence. RESULTS We identified 28 eligible trial comparisons (n = 1,394). Viscous fiber at a median dose of ∼13.1 g/day significantly reduced HbA1c (MD -0.58% [95% CI -0.88, -0.28]; P = 0.0002), fasting blood glucose (MD -0.82 mmol/L [95% CI -1.32, -0.31]; P = 0.001), and HOMA-insulin resistance (IR) (MD -1.89 [95% CI -3.45, -0.33]; P = 0.02) compared with control and in addition to standard of care. The certainty of evidence was graded moderate for HbA1c, fasting glucose, fasting insulin, and HOMA-IR and low for fructosamine. CONCLUSIONS Viscous fiber supplements improve conventional markers of glycemic control beyond usual care and should be considered in the management of type 2 diabetes.