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Dietary Fiber Intake and Type 2 Diabetes Mellitus: An Umbrella Review of Meta-analyses
Abstract
Objective
The purpose of this study was to review previously published meta-analyses on the effectiveness of dietary fiber on type 2 diabetes.
Methods
An umbrella review of all published meta-analyses was performed. A PubMed search from January 1, 1980, to April 30, 2017, was conducted using the following search strategy: (fiber OR glucan OR psyllium) AND (meta-analysis OR systematic review). Only English-language publications that provided quantitative statistical analysis on type 2 diabetes, fasting blood glucose concentrations, or glycosylated hemoglobin were retrieved.
Results
Sixteen meta-analyses were retrieved for inclusion in this umbrella review. In the meta-analyses comparing highest versus lowest dietary fiber intake, there was a statistically significant reduction in the relative risk (RR) of type 2 diabetes (RR = 0.81-0.85), with the greatest benefit coming from cereal fibers (RR = 0.67-0.87). However, statistically significant heterogeneity was observed in all of these meta-analyses. In the meta-analyses of supplementation studies using β-glucan or psyllium fibers on type 2 diabetic participants, statistically significant reductions were identified in both fasting blood glucose concentrations and glycosylated hemoglobin percentages.
Conclusion
This review suggests that those consuming the highest amounts of dietary fiber, especially cereal fiber, may benefit from a reduction in the incidence of developing type 2 diabetes. There also appears to be a small reduction in fasting blood glucose concentration, as well as a small reduction in glycosylated hemoglobin percentage for individuals with type 2 diabetes who add β-glucan or psyllium to their daily dietary intake.
... There are some evidences that prevention of metabolic syndrome (MetS) could be developed by lower intake of harmful components of DRRD, such as SSB, trans fatty acids and red and processed meat [10][11][12]. Other investigations suggested that high consumption of fiber along with low dietary GI, could improve glycemic control and reduce fasting plasma glucose, insulin resistance, and obesity [13]. ...
Background
Insufficient evidence exists regarding the relationship between diabetes risk reduction diet (DRRD) and metabolic health status in adolescents. The current study aimed to investigate the relationship between DRRD and metabolic health status in Iranian adolescents with overweight/obesity.
Methods
In this cross-sectional study, a multistage cluster random sampling method was used to select 203 overweight/obese adolescents. Dietary intakes were evaluated using a validated 147-item food frequency questionnaire. The following parameters were measured: blood pressure, anthropometric indices, fasting glucose, insulin, and lipid profiles. Participants were classified to metabolically healthy overweight/obese (MHO) or metabolically unhealthy overweight/obese (MUO), based on 2 methods: International Diabetes Federation (IDF) criteria and a combination of IDF and Homeostasis Model Assessment Insulin Resistance (HOMA-IR).
Results
Based on IDF criteria, highest vs. lowest adherence to DRRD was associated with a lower odds of having an MUO phenotype in both crude (OR = 0.05; 95%CI: 0.02–0.12) and fully adjusted model (OR = 0.06; 95%CI: 0.02–0.20). Based on IDF/HOMA-IR criteria, similar findings were obtained. This relationship was significant in both genders and was especially significant among adolescents with obesity. In both crude and fully adjusted model, adherence to DRRD was significantly lower the likelihood of having high fasting blood glucose, triglycerides, and HOMA-IR.
Conclusion
Adolescents who adhered more strictly to DRRD were less likely to be MUO, and have high fasting blood glucose, triglycerides, and HOMA-IR. Additional large-scale prospective studies are necessary to affirm these results.
... Studies have demonstrated that a high dietary fiber intake protects against the development of DM. A high intake of dietary fiber and a high sodium intake may have a role in reducing the risk of DM 29 . Lastly, the follow-up period of our study was short, which does not reflect the long-term effects of sodium intake on DM. ...
We aimed to examine the effects of sodium and potassium intake on the risk of diabetes mellitus (DM). In a cohort of 99,552 working-age Korean adults (60,591 men; mean age 39.7 ± 6.9 and 38,961 women; mean age 38.4 ± 6.5), we longitudinally evaluated the risk of DM in relation to quartile levels of sodium intake, potassium intake, and the sodium-potassium ratio. A Cox proportional hazards model was used to assess the risk of DM by calculating adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for incident DM (adjusted HR [95% CI]). In men, sodium intake was not associated with the risk of DM (first quartile: reference, second quartile: 0.96 [0.87–1.07], third quartile: 0.94 [0.84–1.05], and fourth quartile: 1.02 [0.89–1.18]). Women did not show a significant association between sodium intake and the risk of DM (first quartile: reference, second quartile: 0.87 [0.69–1.09], third quartile: 1.02 [0.81–1.29], and fourth quartile: 1.01 [0.76–1.33]). Additionally, potassium intake and the sodium-potassium ratio were not significantly associated with the risk of DM in either men or women. In conclusion, no significant association was observed between sodium or potassium intake and the risk of DM among working-age Korean adults.
... The findings of this systematic review underscore the potential of dietary fiber as a practical and accessible intervention for improving glycemic control and metabolic health, particularly in individuals with diabetes or at risk for the condition [22]. Incorporating dietary fiber into routine dietary recommendations could serve as a complementary strategy alongside pharmacological treatments, as it not only improves key glycemic markers like HbA1c and FPG but also offers additional benefits such as weight management and modulation of gut microbiota. ...
... The trend towards a lower risk of diabetes among participants with a high intake of dietary fiber aligns with previous studies showing a consistent inverse relationship [34,35]. Benefits include improved blood glucose control, higher insulin sensitivity, lower total cholesterol and SBP, and better weight management [22,34]. ...
Background
The role of carbohydrates in diabetes risk is of particular interest due to conflicting results. This study aims to examine the prospective association between types of dietary carbohydrates (fiber, starch, total sugar, glucose, fructose, lactose, maltose, and added sugar) and the risk of diabetes. Further, this study examines the cross-sectional associations between these nutrients and cardiometabolic risk factors.
Methods
Danish Health Examination Survey (2007–2008) investigated 76,484 Danes in a representative sample using online questionnaires. Dietary information using a food frequency questionnaire was obtained from 42,836 participants. Information on incident cases of diabetes was obtained from the Danish National Diabetes Register. Cox proportional hazard models were used to estimate Hazard Ratios (95% CI). Multiple linear regression analyses were used to assess the associations between carbohydrate types and cardiometabolic risk factors measured in a subsample of 12,977 participants.
Results
During a median follow-up of 4.9 years, 970 participants developed diabetes. A higher consumption of fructose, but a lower consumption of glucose was associated with a lower risk of diabetes. In subgroup analyses, these associations were only significant among individuals with other risk factors, such as older age, obesity, low fiber consumption, sedentary behavior, smoking status, and hypertension. Participants with a higher intake of fiber tend to have a lower risk of diabetes and healthier anthropometric parameters compared to those with a lower intake.
Conclusions
Our findings suggest that a higher intake of dietary fiber and fructose is associated with a lower risk of diabetes and healthier metabolic status, while higher glucose intake is associated with a higher diabetes risk.
Graphical Abstract
... The explanation of these metabolic benefits is their high content of fibers that range from 4.6 g in fava beans up to 9.6 g fiber in navy beans and 6.2 g in 100 g cooked chickpeas [80]. These ingredients may lead to a lower risk of type 2 diabetes mellitus [81]. EFSA considers a daily intake of 25 g or more dietary fiber sufficient in reducing the complications of diabetes mellitus [82] and may help regulate post-prandial glucose levels [83]. ...
According to the US Department of Agriculture, more than 4000 types of beans are cultivated in the United States and worldwide; nevertheless, the demand for beans continues to rise. To some extent, diet can treat inflammation and consequently reduce the chances of developing comorbidities, such as diabetes. A diet based on alternative plant protein sources, such as beans, is a sustainable solution for overall health due to the overconsumption of meat that characterizes Western societies and is even more important for regions that suffer from malnutrition, such as Africa. Reviewing the nutritional profile of the different varieties of beans produced in various locations would help enhance their quality, strengthen the role of producer groups, and protecting Geographical Indications (GI), thereby increasing simplification, sustainability, and transparency towards consumers. PubMed-Medline, Web of Science, Scopus, and Cochrane Library databases were searched for relevant articles published by 30 March 2024. The results have given the green light to the reform of EFSA rules, strengthening the health claims of beans, protecting the GI for each variety, and also highlighting the public demands for functional foods based on the nutritional aspects of this product and its impact on disease management or prevention.
Dietary fibers primarily consist of carbohydrates and are derived from plant-based sources. Two distinct categories exist depending on their solubility in water, namely soluble and insoluble dietary fibers. These substances are indigestible and/or absorbable by the human body. They play a crucial function in the maintenance of optimal health. Recent research indicates that high-fiber diets, particularly those containing soluble dietary fibers, can effectively manage weight and protect against obesity, ulcerative colitis, diabetes, cardiovascular diseases, hypertension, gastrointestinal diseases, diverticulosis, hemorrhoids, and colon cancer. Although subject to ongoing debate, a proposition suggests that fiber may have potential benefits for those diagnosed with diabetes mellitus, namely in managing their blood glucose levels following a meal and enhancing carbohydrate metabolism. This chapter explores the functional aspects of dietary fiber in nutraceuticals, emphasizing its role in promoting human health and well-being. The chapter covers the various types of dietary fiber, their sources, and their potential applications in formulating functional food products. The chapter also delves into the physiological effects of dietary fiber consumption, its impact on gut microbiota, its potential role in preventing chronic diseases, and the harmful effects of consuming excessive dietary fiber.
Background: The glycemic response to diet has been linked with noncommunicable diseases and is reduced by low-palatable, viscous, soluble fiber (1). Whether a palatable, low-viscous, soluble fiber such as resistant maltodextrin (RMD) has the same effect is unclear.
Objective: The objective was to assess evidence on the attenuation of the blood glucose response to foods by ≤10 g RMD in healthy adults.
Design: We conducted a systematic review of randomized, placebo-controlled trials with the use of fixed- and random-effects meta-analyses and meta-regression models.
Results: We found data from 37 relevant trials to April 2007. These trials investigated the attenuation of the glycemic response to rice, noodles, pastry, bread, and refined carbohydrates that included 30–173 g available carbohydrate. RMD was administered in drinks or liquid foods or solid foods. Placebo drinks and foods excluded RMD. Percentage attenuation was significant, dose-dependent, and independent of the amount of available carbohydrate coingested. Attenuation of the glycemic response to starchy foods by 6 g RMD in drinks approached ≈20%, but when placed directly into foods was ≈10%—significant (P < 0.001) by both modes of administration. Study quality analyses, funnel plots, and trim-and-fill analyses uncovered no cause of significant systematic bias. Studies from authors affiliated with organizations for-profit were symmetrical without heterogeneity, whereas marginal asymmetry and significant heterogeneity arose among studies involving authors from nonprofit organizations because of some imprecise studies.
Conclusions: A nonviscous palatable soluble polysaccharide can attenuate the glycemic response to carbohydrate foods. Evidence of an effect was stronger for RMD in drinks than in foods.
Background/objectives:
This systematic review and meta-analysis was performed to assess the effects of inulin-type fructans (ITF) on human blood lipids and glucose homeostasis associated with metabolic abnormalities, including dyslipidemia, overweight or obesity, and type-2 diabetes mellitus (T2DM).
Subjects/methods:
The MEDLINE, EMBASE and Cochrane Library databases were systematically searched for randomized controlled trials (RCTs) before January 2016. Human trials that investigated the effects of ITF supplementation on the lipid profile, fasting glucose and insulin were included using Review Manager 5.3.
Results:
Twenty RCTs with 607 adult participants were included in this systematic review and meta-analysis. In the overall analysis, the supplementation of ITF reduced only the low density lipoprotein-cholesterol (LDL-c) (mean difference (MD): -0.15; 95% confidence interval (CI): -0.29, -0.02; P=0.03) without affecting the other endpoints. Within the T2DM subgroup analysis, ITF supplementation was positively associated with a decreased fasting insulin concentration (MD: -4.01; 95% CI: -5.92, -2.09; P<0.0001) and increased high density lipoprotein-cholesterol (HDL-c) (MD: 0.07; 95% CI: 0, 0.14; P=0.05). Moreover, a reduced fasting glucose tendency was identified only in the T2DM subgroup (MD: -0.42; 95% CI: -0.90, 0.06; P=0.09). There was a potential publication bias, and few trials were available for the T2DM subgroup analysis.
Conclusions:
In summary, the use of ITF may have benefits for LDL-c reduction across all study populations, whereas HDL-c improvement and glucose control were demonstrated only in the T2DM subgroup. Thus, additional, well-powered, long-term, randomized clinical trials are required for a definitive conclusion. Overall, ITF supplementation may provide a novel direction for improving the lipid profile and glucose metabolism.European Journal of Clinical Nutrition advance online publication, 14 September 2016; doi:10.1038/ejcn.2016.156.
Background:
The proportion of the US adult population who meet fiber intake recommendations is very low. Information about food groups consumed and diet quality for the adults who consume recommended amounts of fiber are scarce.
Objective:
To examine food groups consumed and Healthy Eating Index (HEI-2010) scores for US adults meeting the fiber adequate intake (AI) based on National Health and Nutrition Examination Survey (NHANES) data 2001-2010.
Design:
A secondary analysis of NHANES data from 2001 to 2010. Participants included adults aged 19 and older (n=24,807) with complete day 1 dietary records. Variables measured were food group sources of fiber and HEI-2010 scores. Sample-weighted data were used to calculate least square means (LSM)±standard error of the mean (SEM) by fiber intake quartile along with HEI-2010 scores. Significance was set at P<0.05.
Results:
Major fiber food sources for US adults meeting the AI were grain products, vegetables, legumes, and fruits. The top grain products consumed were grain mixtures, ready-to-eat (RTE) cereals, and breads/rolls. The mean HEI-2010 score for adults meeting the AI for fiber was significantly (P<0.001) higher compared with all adult participants. The mean HEI-2010 score increased with increasing fiber intake in both groups.
Conclusions:
Adults who meet the AI for fiber have a higher quality diet. Fiber may be an important dietary component that predicts diet quality.
Many individual studies on oat β-glucan (OBG) confirmed its functionality in improving type 2 diabetes mellitus (T2DM), but disagreements were identified among those results. To derive a pooled estimate of these results, relevant articles, published before 5 September 2015, were collected from four electronic databases (Pubmed, Cochrane Library, Scopus, and Web of Science) and subjected to meta-analysis in the present work. In total, four articles, dealing with 350 T2DM patients combined, met the inclusion criteria. Compared to control, T2DM patients administrated OBG from 2.5 to 3.5 g/day for 3 to 8 weeks presented significantly lowered concentrations in fasting plasma glucose (FPG) by -0.52 (95% CI: -0.94, -0.10) mmol/L (p = 0.01) and glycosylated hemoglobin (HbA1c) by -0.21% (95% CI: -0.40, -0.02) (p = 0.03). However, OBG intake did not significantly lower the fasting plasma insulin (FPI) concentration. In conclusion, mediate-term OBG intake (3-8 weeks) favored the glycaemic control of T2DM patients but did not improve their insulin sensitivity. Regrettably, data upon the effects of long-term OBG intake on glycaemic control and insulin sensitivity were scarce, which is of much importance and should be addressed in future research.
The present study aimed to comprehensively assess if oats intake is beneficial for diabetic patients. The literature search was conducted in PubMed database up to 23 August 2015. Fourteen controlled trials and two uncontrolled observational studies were included. Compared with the controls, oats intake significantly reduced the concentrations of glycosylated hemoglobin A1c (HbA1c) (MD, −0.42%; 95% CI, −0.61% to −0.23%), fasting blood glucose (FBG) (MD, −0.39 mmol/L; 95% CI, −0.58 to −0.19 mmol/L), total cholesterol (TC) (MD, −0.49 mmol/L; 95% CI, −0.86 to −0.12 mmol/L), low-density lipoprotein cholesterol (LDL-C) (MD, −0.29 mmol/L; 95% CI, −0.48 to −0.09 mmol/L). Oatmeal significantly reduced the acute postprandial glucose and insulin responses compared with the control meal. The present study has revealed a beneficial effect of oats intake on glucose control and lipid profiles in type 2 diabetic patients. Further investigations of oats intake in patients with type 1 diabetes and the safety of oats consumption are required.
Aims/hypothesis:
Intake of dietary fibre has been associated with a reduced risk of type 2 diabetes, but few European studies have been published on this. We evaluated the association between intake of dietary fibre and type 2 diabetes in the European Prospective Investigation into Cancer and Nutrition (EPIC)-InterAct study and in a meta-analysis of prospective studies.
Methods:
During 10.8 years of follow-up, 11,559 participants with type 2 diabetes were identified and a subcohort of 15,258 participants was selected for the case-cohort study. Country-specific HRs were estimated using Prentice-weighted Cox proportional hazards models and were pooled using a random effects meta-analysis. Eighteen other cohort studies were identified for the meta-analysis.
Results:
In the EPIC-InterAct Study, dietary fibre intake was associated with a lower risk of diabetes (HRQ4 vs Q1 0.82; 95% CI 0.69, 0.97) after adjustment for lifestyle and dietary factors. Similar inverse associations were observed for the intake of cereal fibre and vegetable fibre, but not fruit fibre. The associations were attenuated and no longer statistically significant after adjustment for BMI. In the meta-analysis (19 cohorts), the summary RRs per 10 g/day increase in intake were 0.91 (95% CI 0.87, 0.96) for total fibre, 0.75 (95% CI 0.65, 0.86) for cereal fibre, 0.95 (95% CI 0.87, 1.03) for fruit fibre and 0.93 (95% CI 0.82, 1.05) for vegetable fibre.
Conclusions/interpretation:
The overall evidence indicates that the intake of total and cereal fibre is inversely related to the risk of type 2 diabetes. The results of the EPIC-InterAct Study suggest that the association may be partially explained by body weight.
Aims:
With the increase in the number of systematic reviews available, a logical next step to provide decision makers in healthcare with the evidence they require has been the conduct of reviews of existing systematic reviews. Syntheses of existing systematic reviews are referred to by many different names, one of which is an umbrella review. An umbrella review allows the findings of reviews relevant to a review question to be compared and contrasted. An umbrella review's most characteristic feature is that this type of evidence synthesis only considers for inclusion the highest level of evidence, namely other systematic reviews and meta-analyses. A methodology working group was formed by the Joanna Briggs Institute to develop methodological guidance for the conduct of an umbrella review, including diverse types of evidence, both quantitative and qualitative. The aim of this study is to describe the development and guidance for the conduct of an umbrella review.
Methods:
Discussion and testing of the elements of methods for the conduct of an umbrella review were held over a 6-month period by members of a methodology working group. The working group comprised six participants who corresponded via teleconference, e-mail and face-to-face meeting during this development period. In October 2013, the methodology was presented in a workshop at the Joanna Briggs Institute Convention. Workshop participants, review authors and methodologists provided further testing, critique and feedback on the proposed methodology.
Results:
This study describes the methodology and methods developed for the conduct of an umbrella review that includes published systematic reviews and meta-analyses as the analytical unit of the review. Details are provided regarding the essential elements of an umbrella review, including presentation of the review question in a Population, Intervention, Comparator, Outcome format, nuances of the inclusion criteria and search strategy. A critical appraisal tool with 10 questions to help assess risk of bias in systematic reviews and meta-analyses was also developed and tested. Relevant details to extract from included reviews and how to best present the findings of both quantitative and qualitative systematic reviews in a reader friendly format are provided.
Conclusions:
Umbrella reviews provide a ready means for decision makers in healthcare to gain a clear understanding of a broad topic area. The umbrella review methodology described here is the first to consider reviews that report other than quantitative evidence derived from randomized controlled trials. The methodology includes an easy to use and informative summary of evidence table to readily provide decision makers with the available, highest level of evidence relevant to the question posed.
Increasing oats and beta-glucan extract intake has been associated with improved glycemic control, which is associated with the reduction in the development of diabetes. This study aims to assess the different effects between oat (whole and bran) and beta-glucan extract intake on glycemic control and insulin sensitivity. PubMed, Embase, Medline, The Cochrane Library, CINAHL and Web of Science were searched up to February 2014. We included randomized controlled trials with interventions that lasted at least four weeks that compared oats and beta-glucan (extracted from oats or other sources) intake with a control. A total of 1351 articles were screened for eligibility, and relevant data were extracted from 18 studies (n = 1024). Oat product dose ranged from 20 g d(-1) to 136 g d(-1), and beta-glucan extract dose ranged from 3 g d(-1) to 10 g d(-1). Compared with the control, oat intake resulted in a greater decrease in fasting glucose and insulin of subjects (P < 0.05), but beta-glucan extract intake did not. Furthermore, oat intake resulted in a greater decrease in glycosylated hemoglobin (HbA1c) (P < 0.001, I(2) = 0%) and fasting glucose (P < 0.001, I(2) = 68%) after removing one study using a concentrate and a different design and fasting insulin of type 2 diabetes (T2D) (P < 0.001, I(2) = 0%). The intake of oats and beta-glucan extracted from oats were effective in decreasing fasting glucose (P = 0.007, I(2) = 91%) and fasting insulin of T2D (P < 0.001, I(2) = 0%) and tented to lower HbA1c (P = 0.09, I(2) = 92%). Higher consumption of whole oats and oat bran, but not oat or barley beta-glucan extracts, are associated with lower HbA1c, fasting glucose and fasting insulin of T2D, hyperlipidaemic and overweight subjects, especially people with T2D, which supports the need for clinical trials to evaluate the potential role of oats in approaching to the management of glycemic control and insulin sensitivity of diabetes or metabolic syndrome subjects.
Background:
A number of health benefits are associated with intake of soluble, viscous, gel-forming fibers, including reduced serum cholesterol and the attenuation of postprandial glucose excursions.
Objective:
We assess the effects of psyllium, which is a soluble, gel-forming, nonfermented fiber supplement, on glycemic control in patients who were being treated for type 2 diabetes mellitus (T2DM) and in patients who were at risk of developing T2DM.
Design:
A comprehensive search was performed of available published literature (Scopus scientific database) and clinical records stored by Procter & Gamble with the use of key search terms to identify clinical studies that assessed the glycemic effects of psyllium in nondiabetic, pre-T2DM, and T2DM patients.
Results:
We identified 35 randomized, controlled, clinical studies that spanned 3 decades and 3 continents. These data were assessed in 8 meta-analyses. In patients with T2DM, multiweek studies (psyllium dosed before meals) showed significant improvement in both the fasting blood glucose (FBG) concentration (-37.0 mg/dL; P < 0.001) and glycated hemoglobin (HbA1c) [-0.97% (-10.6 mmol/mol); P = 0.048]. Glycemic effects were proportional to baseline FBG; no significant glucose lowering was observed in euglycemic subjects, a modest improvement was observed in subjects with pre-T2DM, and the greatest improvement was observed in subjects who were being treated for T2DM.
Conclusions:
These data indicate that psyllium would be an effective addition to a lifestyle-intervention program. The degree of psyllium's glycemic benefit was commensurate with the loss of glycemic control. Because the greatest effect was seen in patients who were being treated for T2DM, additional studies are needed to determine how best to incorporate psyllium into existing prevention and treatment algorithms with concomitant hypoglycemic medications.
It is the position of the Academy of Nutrition and Dietetics that the public should consume adequate amounts of dietary fiber from a variety of plant foods. Dietary fiber is defined by the Institute of Medicine Food Nutrition Board as “nondigestible carbohydrates and lignin that are intrinsic and intact in plants.” Populations that consume more dietary fiber have less chronic disease. Higher intakes of dietary fiber reduce the risk of developing several chronic diseases, including cardiovascular disease, type 2 diabetes, and some cancers, and have been associated with lower body weights. The Adequate Intake for fiber is 14 g total fiber per 1,000 kcal, or 25 g for adult women and 38 g for adult men, based on research demonstrating protection against coronary heart disease. Properties of dietary fiber, such as fermentability and viscosity, are thought to be important parameters influencing the risk of disease. Plant components associated with dietary fiber may also contribute to reduced disease risk. The mean intake of dietary fiber in the United States is 17 g/day with only 5% of the population meeting the Adequate Intake. Healthy adults and children can achieve adequate dietary fiber intakes by increasing their intake of plant foods while concurrently decreasing energy from foods high in added sugar and fat, and low in fiber. Dietary messages to increase consumption of whole grains, legumes, vegetables, fruits, and nuts should be broadly supported by food and nutrition practitioners.