Dietary fiber intake and its association with diabetic kidney disease in American adults with diabetes:A cross-sectional study

BACKGROUND Dietary fiber(DF)intake may have a protective effect against type 2 diabetes(T2D);however,its relationship with diabetic kidney disease(DKD)remains unclear.AIM To investigate the potential association between DF intake and the prevalence of DKD in individuals diagnosed with T2D.METHODS This cross-sectional study used data from the National Health and Nutrition Examination Survey collected between 2005 and 2018.DF intake was assessed through 24-h dietary recall interviews,and DKD diagnosis in individuals with T2D was based on predefined criteria,including albuminuria,impaired glomerular filtration rate,or a combination of both.Logistic regression analysis was used to assess the association between DF intake and DKD,and comprehensive subgroup and sensitivity analyses were performed.RESULTS Among the 6032 participants,38.4%had DKD.With lower DF intake-T1(≤6.4 g/1000 kcal/day)-as a reference,the adjusted odds ratio for DF and DKD for levels T2(6.5-10.0 g/1000 kcal/day)and T3(≥10.1 g/1000 kcal/day)were 0.97(95%CI:0.84-1.12,P=0.674)and 0.79(95%CI:0.68-0.92,P=0.002),respectively.The subgroup analysis yielded consistent results across various demographic and health-related subgroups,with no statistically significant interactions(all P>0.05).CONCLUSION In United States adults with T2D,increased DF intake may be related to reduced DKD incidence.Further research is required to confirm these findings.

The structural characteristics of dietary fibers from Tremella fuciformis and their hypolipidemic effects in mice

In this study,Tremella fuciformis residues as raw material,dietary fibers from tremella were prepared by multiple enzymes.The structure of dietary fibers from tremella was studied by Fourier transform infrared(FTIR),X-ray diffraction analysis(XRD)and scanning electron microscopy(SEM).We analyzed their lipidlowering properties in vitro(water holding,oil holding swelling cholesterol and sodium cholate binding capacitises)and the hypolipidemic effects in mice.The results showed that tremella dietary fibers presented the infrared absorption spectrum characteristics of polysaccharides and the characteristic diffraction peaks of cellulose type I.SEM results indicated that the surface of insoluble dietary fiber(IDF)was porous,while the soluble dietary fiber(SDF)was relatively compact and spongy.IDF exhibited significantly higher water holding,oil holding,and swelling binding capacities than the corresponding SDF.However,SDF exhibited significantly higher viscosity than IDF.The results showed tremella dietary fibers were significant in swelling,water holding and oil holding,cholesterol and bile acids.In vivo experiment results in mice indicated that SDF has the best effect on hyperlipidemia mice than IDF and total dietary fiber(TDF).SDF showed that the total cholesterol(TC),triglyceride(TG)and low density lipoprotein cholesterol(LDL-C)contents dropped by 28.33%,18.65%,and 48.97%,respectively,while high density lipoprotein cholesterol(HDL-C)content increased by 43.80%.Compared with the high-fat control(HCM)group,the arteriosclerosis index(AI)and liver index(LI)of the SDF group mice showed significant differences,indicating that SDF has a good auxiliary effect of lowering blood lipids.The administration of tremella fibers improved the lipid metabolism disorderly situation of hyperlipidemia mice.These results provide a reference for further research and rational development of T.fuciformis.

Dietary fibers with low hydration properties exacerbate diarrhea and impair intestinal health and nutrient digestibility in weaned piglets

Background:This study aimed to investigate the hydration properties of different-source fibrous materials by com-paring their water-binding capacity(WBC),water swelling capacity(WSC),viscosity,and in vivo effects of selected samples on growth performance,nutrient digestibility,diarrhea,and intestinal health in weaned piglets.Methods:A total of 13 commercially available fibrous materials were first compared in chemical composition and in vitro hydration property.Subsequently,40 weaned piglets were randomized to five experimental dietary groups(8 piglets per group):control diet(a basal diet without dietary fiber,CON),basal diet supplemented with 5%microcrys-talline cellulose(MCC),5%wheat bran(WB),5%Moringa oleifera leaf powder(MOLP),or 5%sugar beet pulp(SBP),fol-lowed by analyzing their growth performance and diarrhea rate in a 28-d experiment.After the feeding experiment,anaesthetized piglets were killed,and their intestinal and colon content or plasma samples were analyzed in nutrient digestibility,intestinal morphology,intestinal barrier,short-chain fatty acids(SCFAs),and bacterial population.Results:In vitro studies showed low hydration properties for WB and MCC,while medium hydration properties for MOLP and SBP.In vivo studies indicated that compared with medium hydration property groups,low hydration prop-erty groups showed(1)exacerbated diarrhea,impaired intestinal health,and reduced apparent fecal digestibility of dry matter,gross energy,acid detergent fiber,and neutral detergent fiber;(2)decreased SCFAs concentration and rela-tive levels of Lactobacillus and Bifidobacterium,but increased levels of Escherichia coli and Brachyspira hyodysenteriae in colon contents.Additionally,SBP showed optimal performance in reducing diarrhea and increasing SCFAs produc-tion.Correlation analysis revealed a positive correlation of fiber hydration properties with in vitro SCFAs production,and diarrhea index and nutrient digestibility were negatively and positively correlated with SCFAs levels in the colon contents of weaned piglets,respectively.Conclusions:Different-source dietary fibers varied in their hydration properties and impacts on diarrhea,microbial composition and SCFAs production in weaned piglets.WB and MCC could exacerbate diarrhea and impair nutrient digestibility,probably because their low hydration properties were detrimental to gut microbial homeostasis and fermentation.Our findings provide new ideas for rational use of fiber resources in weaned piglets.

Impact of Inulin Extracted, Purified from (Chicory and Globe Artichoke) Roots and the Combination with Maltodextrin as Prebiotic Dietary Fiber on the Functional Properties of Stirred Bio-Yogurt

Inulin is a prebiotic dietary fiber that plays an integral role in producing functional dairy products with improved health benefits. Therefore, the objectives of this study are as follows: extract and purify inulin from chicory roots and globe artichoke roots;evaluate the physicochemical, functional properties and functional groups of the purified inulin;determine the functional properties of chicory roots inulin-maltodextrin and globe artichoke roots inulin-maltodextrin and compare it with that of the commercial inulin;examine the impact of various inulin on physiochemical, microstructural, textural, sensory characteristics and as prebiotic dietary fiber on probiotic bacteria’s viability of stirred bio-yogurt. The characteristics of the microstructure were investigated by scanning electron microscopy and, Fourier transforms infrared spectroscopy to detect the functional group. The resulting inulin exhibited a high yield and purity along with enhanced functional properties. Stirred bio-yogurt fortified with chicory roots inulin or globe artichoke roots inulin showed enhanced physicochemical, microstructural, microbiological, and overall sensorial acceptability followed by chicory roots inulin-maltodextrin or globe artichoke roots inulin-maltodextrin and the commercial inulin as compared to the control. Stirred bio-yogurt samples can offer various health benefits and wide applications as supplement of prebiotic dietary fiber in dairy industry.

Dietary fiber during gestation improves lactational feed intake of sows by modulating gut microbiota

Background The feed intake of sows during lactation is often lower than their needs.High-fiber feed is usually used during gestation to increase the voluntary feed intake of sows during lactation.However,the mechanism underlying the effect of bulky diets on the appetites of sows during lactation have not been fully clarified.The current study was conducted to determine whether a high-fiber diet during gestation improves lactational feed intake(LFI)of sows by modulating gut microbiota.Methods We selected an appropriate high-fiber diet during gestation and utilized the fecal microbial transplanta-tion(FMT)method to conduct research on the role of the gut microbiota in feed intake regulation of sows during lactation,as follows:high-fiber(HF)diet during gestation(n=23),low-fiber(LF)diet during gestation(n=23),and low-fiber diet+HF-FMT(LFM)during gestation(n=23).Results Compared with the LF,sows in the HF and LFM groups had a higher LFI,while the sows also had higher peptide tyrosine tyrosine and glucagon-like peptide 1 on d 110 of gestation(G110 d).The litter weight gain of piglets during lactation and weaning weight of piglets from LFM group were higher than LF group.Sows given a HF diet had lower Proteobacteria,especially Escherichia-Shigella,on G110 d and higher Lactobacillus,especially Lactobacil-lus_mucosae_LM1 and Lactobacillus_amylovorus,on d 7 of lactation(L7 d).The abundance of Escherichia-Shigella was reduced by HF-FMT in numerically compared with the LF.In addition,HF and HF-FMT both decreased the perinatal concentrations of proinflammatory factors,such as endotoxin(ET),lipocalin-2(LCN-2),tumor necrosis factor-α(TNF-α),and interleukin-1β(IL-1β).The concentration of ET and LCN-2 and the abundance of Proteobacteria and Escheri-chia-Shigella were negatively correlated with the LFI of sows.Conclusion The high abundance of Proteobacteria,especially Escherichia-Shigella of LF sows in late gestation,led to increased endotoxin levels,which result in inflammatory responses and adverse effects on the LFI of sows.Add-ing HF during gestation reverses this process by increasing the abundance of Lactobacillus,especially Lactobacil-lus_mucosae_LM1 and Lactobacillus_amylovorus.

Mechanisms linking dietary fiber, gut microbiota and colon cancer prevention

Many epidemiological and experimental studies have suggested that dietary fiber plays an important role in colon cancer prevention. These findings may relate to the ability of fiber to reduce the contact time of carcinogens within the intestinal lumen and to promote healthy gut microbiota, which modifies the host's metabolism in various ways. Elucidation of the mechanisms by which dietary fiber-dependent changes in gut microbiota enhance bile acid deconjugation, produce short chain fatty acids, and modulate inflammatory bioactive substances can lead to a better understanding of the beneficial role of dietary fiber. This article reviews the current knowledge concerning the mechanisms via which dietary fiber protects against colon cancer.

The effects of dietary fiber level on nutrient digestibility in growing pigs

The objective of this study was to investigate the effects of total dietary fiber level on nutrient digestibility and the relationship between apparent total tract digestibility of total dietary fiber, and soluble dietary fiber, insoluble dietary fiber and available energy. Sugar beet pulp was as the only fiber source. The experiment was designed as a 6 x 6 Latin square with an adaptation period of 7 d followed by a 5-d total collection of feces and urine. Feed intake tended to decrease （P =0.] O） as total dietary fiber level increased. The apparent total tract digestibility of dry matter, crude protein and gross energy decreased （P 〈0.0]） when total dietary fiber increased but the digestibility of soluble dietary fiber and insoluble dietary fiber increased （P 〈0.01）. The digestible energy and metabolizable energy content of diets decreased （P 〈0.01） as the total dietary fiber increased.

<i>In-Vitro</i>Fermentation by Human Fecal Bacteria and Bile Salts Binding Capacity of Physical Modified Defatted Rice Bran Dietary Fiber

Defatted rice bran dietary fiber (DRBDF) was modified by micronization, ultrasound, microwave and extrusion cooking. We investigated the impacts of these physical treatments on the fermentation ability and bile salts binding capacity of DRBDF. In-vitro fermentation by human fecal bacteria of modified fibers showed that the major fermentation products were propionic, acetate and butyrate acid. Fermentation of extruded fiber gave the highest amounts of propionic and acetic acid 135.76 and 25.45 mmol/L respectively, while, the fermented product with microwaved fiber had the highest butyric acid content (10.75 mmol/L). The amount of short-chain fatty acid increased from 12 h to 24 h and propionic acid was the predominant. On the other hand,in-vitrobile salts binding showed that extruded fiber had higher affinity with sodium deoxycholate and sodium chenodeoxycholate (66.14% and 30.25% respectively) while microwaved fiber exhibited the highest affinity with sodium taurocholate (14.38%). In the light of obtained results we can affirmed that these physical treatments significantly improved the fermentation products and bile salts binding capacity of DRBDF. Extrusion compared to the other physical treatment methods used in this study has greatly and positively influenced the fermentation and bile binding capacity of DRBDF.

Increasing dietary fiber intake in terms of kiwifruit improves constipation in Chinese patients

AIM： To investigate if increased dietary fiber, in terms of kiwifruit, is effective in Chinese constipated patients. METHODS： 33 constipated patients and 20 healthy volunteers were recruited for a 4-wk treatment of kiwi fruit twice daily. Response during wk 1-4 was defined as an increase in complete spontaneous bowl, motion （CSBM）≥ 1/wk. Secondary efficacy included response during wk 1-4, individual symptoms and scores of bowel habits and constipation. Responses were compared with the baseline run-in period. Colonic transit time and anorectal manometry were performed before and after treatment. RESULTS： Responder rate was 54.5% in the constipated group. The mean CSBM increased after treatment （2.2±2.6 vs 4.4± 4.6, P = 0.013）. There was also improvement in the scores for bothersomeness of constipation （P = 0.02）, and satisfaction of bowel habit （P = 0.001）, and decreased in days of laxative used （P = 0.003）. There was also improvement in transit time （P = 0.003） and rectal sensation （P 〈 0.05）. However, there was no change in the bowel symptoms or anorectal physiology in the healthy subjects. CONCLUSION： Increasing dietary fiber intake is effective in relieving chronic constipation in Chinese population.

Modifi cation of wheat bran insoluble and soluble dietary fibers with snail enzyme

Insoluble dietary fiber(IDF)and soluble dietary fiber(SDF)extracted from wheat bran were modifi ed by snail enzyme and their physicochemical properties(water retention capacity and oil retention capacity),functional properties(cholesterol adsorption capacity,glucose adsorption capacity and antioxidant activity)and structural characterizations were evaluated.The results showed that snail enzyme modification led to the significant increase in oil retention capacity of IDF,glucose adsorption capacity and cholesterol adsorption capacity of IDF and SDF.Enzymatic modification also markedly improved the DPPH radical scavenging capacity and reducing power of IDF and SDF.Meanwhile,scanning electron microscopy(SEM)analysis indicated the microstructures of IDF and SDF powders were signifi cantly changed.Fourier transfer-infrared spectrometry(FT-IR)showed that snail enzyme modifi cation could degrade the part of cellulose and hemicellulose of IDF and SDF.All these improved physicochemical and functional properties of IDF and SDF might depend on their structural changes.It suggested that snail enzyme modifi cation could effectively improve physicochemical and functional properties of IDF and SDF from wheat bran.

Dietary fiber in poultry nutrition and their effects on nutrient utilization,performance,gut health,and on the environment:a review

Dietary fiber(DF)was considered an antinutritional factor due to its adverse effects on feed intake and nutrient digestibility.However,with increasing evidence,scientists have found that DF has enormous impacts on the gastrointestinal tract(GIT)development,digestive physiology,including nutrient digestion,fermentation,and absorption processes of poultry.It may help maintain the small and large intestine’s integrity by strengthening mucosal structure and functions and increasing the population and diversity of commensal bacteria in the GIT.Increasing DF content benefits digestive physiology by stimulating GIT development and enzyme production.And the inclusion of fiber at a moderate level in diets also alters poultry growth performance.It improves gut health by modulating beneficial microbiota in the large intestine and enhancing immune functions.However,determining the source,type,form,and level of DF inclusion is of utmost importance to achieve the above-noted benefits.This paper critically reviews the available information on dietary fibers used in poultry and their effects on nutrient utilization,GIT development,gut health,and poultry performance.Understanding these functions will help develop nutrition programs using proper DF at an appropriate inclusion level that will ultimately lead to enhanced DF utilization,overall health,and improved poultry growth performance.Thus,this review will help researchers and industry identify the sources,type,form,and amount of DF to be used in poultry nutrition for healthy,costeffective,and eco-friendly poultry production.

Inclusion of purified dietary fiber during gestation improved the reproductive performance of sows

Background: This study aimed to investigate the impacts of guar gum and cellulose as the source of dietary fiber during gestation on the reproductive performance of sows.Methods: A total of 210 sows(parities 3–6) were randomly allocated into six diets(n = 35) throughout gestation to feed graded levels of dietary fiber(DF), including a corn-soybean meal-based control diet with no wheat bran inclusion(CON, 12.5% DF), a wheat bran-rich diet(DF1, 17.4% DF), and another 4 diets(DF2, 17.7% DF;DF3, 18.1%DF;DF4, 18.4% DF;DF5, 18.8% DF) in which wheat bran were equally substituted by 1%, 2%, 3% and 4% purified FIBER MIX(guar gum and cellulose, 1:4). All sows received similar DE and other nutrients throughout gestation.Results: DF treatment during gestation resulted in normal fecal score(1 to 5 with 1 = dry and 5 = watery) in sows compared with those received the CON diet(P < 0.05). The number of total born piglets had a tendency to be affected by dietary treatment(P = 0.07), and correlation analysis revealed a linear response of total born to dietary fiber levels during gestation(P < 0.01). Sows received the DF2, DF3, and DF5 diets during gestation had a greater ADFI during lactation compared with those in the CON group(P < 0.05) without affecting the daily body weight gain of suckling piglets. Gut microbiota compositions were dramatically changed by the gestation stage and some of those were changed by DF inclusion. Fecal acetate, propionate, and butyrate of sows were markedly increased in late gestation, and butyrate contents in feces of gestating sows were significantly affected by DF levels(P < 0.01).Serum concentrations of pro-inflammatory TNF-α were decreased and anti-inflammatory IL-10 was increased on day30 of gestation by DF levels(P < 0.05).Conclusions: In summary, increasing dietary fiber levels by guar gum and cellulose during gestation improved the reproductive performance of sows, which might be related to changes in immunity and gut microbiota of sows.

Research Status and Progress on Modification of Dietary Fiber at Home and Abroad

Studies have shown that modified dietary fiber has better physical and chemical properties and functions,and can better play its physiological effects.This paper systematically and comprehensively expounded the application progress of chemical separation method,microbial fermentation method,physical method,enzyme method and steam explosion method in dietary fiber modification,and expounded the development prospect of modified dietary fiber,so as to provide reference for further study on development and application of dietary fiber.

Mini-review on edible mushrooms as source of dietary fiber:Preparation and health benefits

Dietary fiber and high-fiber food products have attracted great attention because of their significant health benefits to consumers.Mushrooms are valuable resources for food,medicine and nutraceuticals.Edible mushroom is considered as a novel source of dietary fiber.The dietary fiber content and composition in edible mushroom vary greatly with its morphological stages including fruit body,mycelium and sclerotium.The focus of this mini-review is on the preparation of dietary fiber from edible mushroom with emphasis on the sclerotium which has the highest level of non-starch polysaccharides.The possible health benefits of mushroom dietary fiber in relationship with boosting the immune system,anticancer functions as well as the control of blood lipids and glucose levels are also discussed.©2013 Beijing Academy of Food Sciences.Production and hosting by Elsevier B.V.All rights reserved.

Application of dietary fiber in clinical enteral nutrition: A meta-analysis of randomized controlled trials

AIM: To evaluate the effects of dietary fiber (DF) as a part of enteral nutrition (EN) formula on diarrhea, infection, and length of hospital stay. METHODS: Following electronic databases were searched for randomized controlled trials about DF: Chinese Biomedicine Database (CBM), MEDLINE, EMBASE and Cochrane Controlled Trials Register. RevMan 4.1 was used for statistical analysis. RESULTS: Seven randomized controlled trials with 400 pat-ients were included. The supplement of DF in EN was compared with standard enteral formula in five trials. Combined analysis did not show a significant reduction in occurrence of diarrhea, but there were valuable results for non-critically ill patients. Combined analysis of two trials observing the infection also did not show any valid evidence that DF could decrease the infection rate, though the length of hospital stay was reduced significantly. CONCLUSION: Based on the current eligible randomized controlled trials, there is no evidence that the value of DF in the diarrhea can be proved. Though length of hospital stay was shortened by the use of DF, there is no available evidence in preventing infection by DF. Further studies are needed for evaluating the value of DF in EN.

Effects of dietary fiber on human health

Dietary fiber(DF)is believed to provide important health benefits and it has become a research hotspot.DF exists in most natural foods,including fruits(16.74%-91.24%),vegetables(6.53%-85.19%),grains(9.76%-69.20%)and so on.DF has different physicochemical properties such as water holding capacity(WHC)(2.01-25.03 g/g),water swelling capacity(WSC)(0.95-23.90 mL/g),oil holding capacity(OHC)(0.65-29.00 g/g),glucose adsorption capacity(GAC)(0.17-4.65 mmol/g),cholesterol adsorption capacity(CAC)(0.03-37.10 mg/g)and viscosity,which make it exhibits different physiological functions such as reducing the risk of obesity,diabetes,cancer,and intestinal diseases.On the basis of consulting related databases,the physicochemical properties of DF and its derived physiological functions are reviewed.It is found that DF has effect on the prevention and treatment of obesity due to good WHC,WSC,OHC and CAC.Good GAC can relieve the symptoms of diabetes.The physicochemical properties of WHC and WSC can reduce the risk of cancer.The WHC,WSC and viscosity are beneficial to intestinal health.

Effect of wheat bran insoluble dietary fiber with different particle size on the texture properties, protein secondary structure, and microstructure of noodles

This study was conducted to explore how the insoluble dietary fiber(IDF)of wheat bran with different particle size affects the texture properties,water distribution,protein secondary structure and microstructure of noodles.The results suggested that IDF addition increased the cooking loss and decreased the sensory evaluation because of the damage on dough structure,while as the IDF particle size decreased,the sensory score increased from 78.8 to 82.3 and cooking loss decreased from 8.65%to 7.65%,which could be attributed to that small particle-sized IDF limited the damage on protein network structure,decreased the T22 and t-structure,and increased the β1-structure.Moreover,IDF particle size had a significant correlation with protein secondary structures,texture properties and evaluation score of noodles.In conclusion,adding appropriate particle sizewould be an effectiveway of enhancing the nutritional and textural properties of noodles.

Study on the effect of wheat bran dietary fiber on the rheological properties of dough

The aim of the study was to determine the influence of wheat bran dietary fiber on wheat flour dough rheological properties.In this paper,wheat bran dietary fiber(WBDF)with different levels(0,3%,6%,9%,12%)were added to wheat flour and the characterization of dough rheological properties was conducted by rapid visco-analyzer,farinograph,as well as rotational rheometer.The results from pasting properties showed a gradual reduction in peak viscosity,trough viscosity,final viscosity and setback with increasing WBDF content.At high WBDF concentration,the significant increase of water absorption,formation time as well as weakening degree implied the harder formation of gluten network structure and the competition for water between gluten and WBDF particles.Such conclusion was in line with the findings from dynamic rheology tests,in which the doughs containing WBDF were more sensitive to strain regardless of their rigid and stiff texture.This study revealed vulnerable dough structure induced by WBDF,as well as the strengthened elastic property,elaborating the harmful effects ofWBDF on the rheological properties of doughs.

Effects of dietary protein restriction on muscle fiber characteristics and m TORC1 pathway in the skeletal muscle of growing-finishing pigs

Background： To investigate the effects of dietary crude protein（CP） restriction on muscle fiber characteristics and key regulators related to protein deposition in skeletal muscle, a total of 18 growing-finishing pigs（62.30 ± 0.88 kg）were allotted to 3 groups and fed with the recommended adequate protein（AP, 16 % CP） diet, moderately restricted protein（MP, 13 % CP） diet and low protein（LP, 10 % CP） diet, respectively. The skeletal muscle of different locations in pigs, including longissimus dorsi muscle（LDM）, psoas major muscle（PMM） and biceps femoris muscle（BFM） were collected and analyzed.Results： Results showed that growing-finishing pigs fed the MP or AP diet improved（P 〈 0.01） the average daily gain and feed： gain ratio compared with those fed the LP diet, and the MP diet tended to increase（P = 0.09） the weight of LDM. Moreover, the ATP content and energy charge value were varied among muscle samples from different locations of pigs fed the reduced protein diets. We also observed that pigs fed the MP diet up-regulated（P 〈 0.05） muscular m RNA expression of all the selected key genes, except that myosin heavy chain（My HC） IIb,My HC IIx, while m RNA expression of ubiquitin ligases genes was not affected by dietary CP level. Additionally, the activation of mammalian target of rapamycin complex 1（m TORC1） pathway was stimulated（P 〈 0.05） in skeletal muscle of the pigs fed the MP or AP diet compared with those fed the LP diet.Conclusion： The results suggest that the pigs fed the MP diet could catch up to the growth performance and the LDM weight of the pigs fed the AP diet, and the underlying mechanism may be partly due to the alteration in energy status, modulation of muscle fiber characteristics and m TORC1 activation as well as its downstream effectors in skeletal muscle of different locations in growing-finishing pigs.

Effect of dietary fiber on constipation:A meta analysis

AIM:To investigate the effect of dietary fiber intake on constipation by a meta-analysis of randomized controlled trials(RCTs).METHODS:We searched Ovid MEDLINE(from 1946 to October 2011),Cochrane Library(2011),PubMed for articles on dietary fiber intake and constipation using the terms:constipation,fiber,cellulose,plant extracts,cereals,bran,psyllium,or plantago.References of important articles were searched manually for relevant studies.Articles were eligible for the meta-analysis if they were high-quality RCTs and reported data on stool frequency,stool consistency,treatment success,laxative use and gastrointestinal symptoms.The data were extracted independently by two researchers(Yang J and Wang HP) according to the described selection criteria.Review manager version 5 software was used for analysis and test.Weighted mean difference with 95%CI was used for quantitative data,odds ratio(OR)with 95%CI was used for dichotomous data.Both I2 statistic with a cut-off of ≥ 50% and the χ2 test with a P value < 0.10 were used to define a significant degree of heterogeneity.RESULTS:We searched 1322 potential relevant articles,19 of which were retrieved for further assessment,14 studies were excluded for various reasons,five studies were included in the analysis.Dietary fiber showed significant advantage over placebo in stool frequency(OR = 1.19;95%CI:0.58-1.80,P < 0.05).There was no significant difference in stool consistency,treatment success,laxative use and painful defecation between the two groups.Stool frequency were reported by five RCTs,all results showed either a trend or a significant difference in favor of the treatment group,number of stools per week increased in treatment group than in placebo group(OR = 1.19;95%CI:0.58-1.80,P < 0.05),with no significant heterogeneity among studies(I2= 0,P = 0.77).Four studies evaluated stool consistency,one of them presented outcome in terms of percentage of hard stool,which was different from others,so we included the other three studies for analysis.Two studies reported treatment success.There was significant heterogeneity between the studies(P < 0.1,I2 > 50%).Three studies reported laxative use,quantitative data was shown in one study,and the pooled analysis of the other two studies showed no significant difference between treatment and placebo groups in laxative use(OR = 1.07;95%CI 0.51-2.25),and no heterogeneity was found(P = 0.84,I2= 0).Three studies evaluated painful defecation:one study presented both quantitative and dichotomous data,the other two studies reported quantitative and dichotomous data separately.We used dichotomous data for analysis.CONCLUSION:Dietary fiber intake can obviously increase stool frequency in patients with constipation.It does not obviously improve stool consistency,treatment success,laxative use and painful defecation.