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Lancet (London, England) Feb 2019Previous systematic reviews and meta-analyses explaining the relationship between carbohydrate quality and health have usually examined a single marker and a limited... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Previous systematic reviews and meta-analyses explaining the relationship between carbohydrate quality and health have usually examined a single marker and a limited number of clinical outcomes. We aimed to more precisely quantify the predictive potential of several markers, to determine which markers are most useful, and to establish an evidence base for quantitative recommendations for intakes of dietary fibre.
METHODS
We did a series of systematic reviews and meta-analyses of prospective studies published from database inception to April 30, 2017, and randomised controlled trials published from database inception to Feb 28, 2018, which reported on indicators of carbohydrate quality and non-communicable disease incidence, mortality, and risk factors. Studies were identified by searches in PubMed, Ovid MEDLINE, Embase, and the Cochrane Central Register of Controlled Trials, and by hand searching of previous publications. We excluded prospective studies and trials reporting on participants with a chronic disease, and weight loss trials or trials involving supplements. Searches, data extraction, and bias assessment were duplicated independently. Robustness of pooled estimates from random-effects models was considered with sensitivity analyses, meta-regression, dose-response testing, and subgroup analyses. The GRADE approach was used to assess quality of evidence.
FINDINGS
Just under 135 million person-years of data from 185 prospective studies and 58 clinical trials with 4635 adult participants were included in the analyses. Observational data suggest a 15-30% decrease in all-cause and cardiovascular related mortality, and incidence of coronary heart disease, stroke incidence and mortality, type 2 diabetes, and colorectal cancer when comparing the highest dietary fibre consumers with the lowest consumers Clinical trials show significantly lower bodyweight, systolic blood pressure, and total cholesterol when comparing higher with lower intakes of dietary fibre. Risk reduction associated with a range of critical outcomes was greatest when daily intake of dietary fibre was between 25 g and 29 g. Dose-response curves suggested that higher intakes of dietary fibre could confer even greater benefit to protect against cardiovascular diseases, type 2 diabetes, and colorectal and breast cancer. Similar findings for whole grain intake were observed. Smaller or no risk reductions were found with the observational data when comparing the effects of diets characterised by low rather than higher glycaemic index or load. The certainty of evidence for relationships between carbohydrate quality and critical outcomes was graded as moderate for dietary fibre, low to moderate for whole grains, and low to very low for dietary glycaemic index and glycaemic load. Data relating to other dietary exposures are scarce.
INTERPRETATION
Findings from prospective studies and clinical trials associated with relatively high intakes of dietary fibre and whole grains were complementary, and striking dose-response evidence indicates that the relationships to several non-communicable diseases could be causal. Implementation of recommendations to increase dietary fibre intake and to replace refined grains with whole grains is expected to benefit human health. A major strength of the study was the ability to examine key indicators of carbohydrate quality in relation to a range of non-communicable disease outcomes from cohort studies and randomised trials in a single study. Our findings are limited to risk reduction in the population at large rather than those with chronic disease.
FUNDING
Health Research Council of New Zealand, WHO, Riddet Centre of Research Excellence, Healthier Lives National Science Challenge, University of Otago, and the Otago Southland Diabetes Research Trust.
Topics: Dietary Carbohydrates; Dietary Fiber; Humans; Noncommunicable Diseases; Primary Prevention
PubMed: 30638909
DOI: 10.1016/S0140-6736(18)31809-9 -
The Proceedings of the Nutrition Society Feb 2020Dietary fibre comprises many different, mainly plant-based, compounds that are not fully digested in the human gut. Insoluble fibres include cellulose, hemi-celluloses... (Review)
Review
Dietary fibre comprises many different, mainly plant-based, compounds that are not fully digested in the human gut. Insoluble fibres include cellulose, hemi-celluloses and lignin and soluble fibres include pectins, β-glucan and hydro-colloids. In the UK, the daily recommended amount has increased to 30 g but only 13 % of men and 4 % of women meet this recommendation. Currently the mean intake for adults is 21 g for men and 17 g for women. There is a wealth of epidemiological evidence based on systematic reviews of trials and cohorts to support the higher fibre recommendation. This includes evidence of reductions in the risk for CVD (both heart disease and stroke) and lower risk of type 2 diabetes, lower blood pressure, lower LDL-cholesterol, as well as some cancers. Beneficial effects of fibre operate via a diverse range of mechanisms throughout the digestive system including the mouth, stomach and small and large intestine; some of which are still not completely understood. The updated recommendation for fibre is a long way from a typical British diet and requires several daily portions of fruit and vegetables and wholegrain foods. Improving dietary fibre intakes will require a variety of actions and policies from stakeholders; however, there is currently more of a focus on reducing sugar than increasing fibre. In order to increase the number of adults meeting the fibre recommendation, social marketing and labelling of high-fibre foods are warranted as well as reformulation and wider availability of wholegrain versions of popular foods.
Topics: Cardiovascular Diseases; Diabetes Mellitus, Type 2; Diet; Dietary Fiber; Female; Health Behavior; Health Promotion; Humans; Male; Nutrition Policy
PubMed: 31266545
DOI: 10.1017/S0029665119000673 -
Nutrients Oct 2018A major challenge in affluent societies is the increase in disorders related to gut and metabolic health. Chronic over nutrition by unhealthy foods high in energy, fat,... (Review)
Review
A major challenge in affluent societies is the increase in disorders related to gut and metabolic health. Chronic over nutrition by unhealthy foods high in energy, fat, and sugar, and low in dietary fibre is a key environmental factor responsible for this development, which may cause local and systemic inflammation. A low intake of dietary fibre is a limiting factor for maintaining a viable and diverse microbiota and production of short-chain fatty acids in the gut. A suppressed production of butyrate is crucial, as this short-chain fatty acid (SCFA) can play a key role not only in colonic health and function but also at the systemic level. At both sites, the mode of action is through mediation of signalling pathways involving nuclear NF-κB and inhibition of histone deacetylase. The intake and composition of dietary fibre modulate production of butyrate in the large intestine. While butyrate production is easily adjustable it is more variable how it influences gut barrier function and inflammatory markers in the gut and periphery. The effect of butyrate seems generally to be more consistent and positive on inflammatory markers related to the gut than on inflammatory markers in the peripheral tissue. This discrepancy may be explained by differences in butyrate concentrations in the gut compared with the much lower concentration at more remote sites.
Topics: Animals; Bacteria; Butyrates; Diet, Healthy; Dietary Fiber; Gastrointestinal Microbiome; Humans; Inflammation; Inflammation Mediators; Intestinal Absorption; Intestines; Nutritive Value; Permeability; Recommended Dietary Allowances; Signal Transduction
PubMed: 30322146
DOI: 10.3390/nu10101499 -
Nutrition Research Reviews Dec 2017Research into the analysis, physical properties and health effects of dietary fibre has continued steadily over the last 40-50 years. From the knowledge gained,... (Review)
Review
Research into the analysis, physical properties and health effects of dietary fibre has continued steadily over the last 40-50 years. From the knowledge gained, countries have developed guidelines for their populations on the optimal amount of fibre to be consumed each day. Food composition tables from many countries now contain values for the dietary fibre content of foods, and, from these, combined with dietary surveys, population intakes have been determined. The present review assessed the uniformity of the analytical methods used, health claims permitted, recommendations and intakes, particularly from national surveys across Europe and around the world. It also assessed current knowledge on health effects of dietary fibre and related the impact of different fibre types on health. The overall intent was to be able to provide more detailed guidance on the types of fibre which should be consumed for good health, rather than simply a total intake figure, the current situation. Analysis of data indicated a fair degree of uniformity in the definition of dietary fibre, the method used for analysis, the recommended amount to be consumed and a growing literature on effects on digestive health and disease risk. However, national dietary survey data showed that intakes do not reach recommendations and very few countries provide guidance on the types of fibre that are preferable to achieve recommended intakes. Research gaps were identified and ideas suggested to provide information for more detailed advice to the public about specific food sources that should be consumed to achieve health benefits.
Topics: Adolescent; Adult; Child; Child, Preschool; Dietary Fiber; Digestion; Europe; Female; Health Knowledge, Attitudes, Practice; Health Promotion; Humans; Infant; Male; Nutrition Policy
PubMed: 28676135
DOI: 10.1017/S095442241700004X -
Food Chemistry May 2024Dietary fiber (DF) was established as a key dietary constituent some decades ago, as were some of its mechanisms of action and health effects. Although there is... (Review)
Review
Dietary fiber (DF) was established as a key dietary constituent some decades ago, as were some of its mechanisms of action and health effects. Although there is consolidated evidence on many features regarding DF, at the same time there are still many aspects to be explored in the field, e.g., deeper explorations of the contribution of phenolic compounds linked to cell walls to the biological activities of DF, or of the relevance of the gut-brain axis. At the same time, increasing DF intake should be seen as a major public health problem since worldwide intakes are quite far from recommendations. The awareness of this fact by public bodies should lead, among others, to the assessment of effective strategies for promoting DF intake among general population or specific groups; and to consider potential regulatory modifications in order to clarify several aspects potentially misleading for consumers.
Topics: Humans; Dietary Fiber; Diet; Phenols; Public Health
PubMed: 38039615
DOI: 10.1016/j.foodchem.2023.138076 -
Food & Function Apr 2016In the past few years, new strategies to control blood pressure levels are emerging by developing new bioactive components of foods. Fiber has been linked to the... (Review)
Review
In the past few years, new strategies to control blood pressure levels are emerging by developing new bioactive components of foods. Fiber has been linked to the prevention of a number of cardiovascular diseases and disorders. β-Glucan, the main soluble fiber component in oat grains, was initially linked to a reduction in plasma cholesterol. Several studies have shown afterward that dietary fiber may also improve glycaemia, insulin resistance and weight loss. The effect of dietary fiber on arterial blood pressure has been the subject of far fewer studies than its effect on the above-mentioned variables, but research has already shown that fiber intake can decrease arterial blood pressure in hypertensive rats. Moreover, certain fibers can improve arterial blood pressure when administered to hypertensive and pre-hypertensive subjects. The present review summarizes all those studies which attempt to establish the antihypertensive effects of dietary fiber, as well as its effect on other cardiovascular risk factors.
Topics: Animals; Blood Pressure; Dietary Fiber; Humans; Hypertension; Rats
PubMed: 26923351
DOI: 10.1039/c5fo00950b -
Nutrition Reviews Apr 2017Digestive health is an expanding area in nutrition research due to the interest in how food components such as fiber affect gastrointestinal tolerance, stool form,... (Review)
Review
Digestive health is an expanding area in nutrition research due to the interest in how food components such as fiber affect gastrointestinal tolerance, stool form, defecation frequency, transit time, and gut microbial composition and metabolic activity. In children, however, digestive health studies that intervene with dietary fiber are limited due to legal and ethical concerns. To better understand if fiber improves digestive health in children, a literature review was conducted to answer the following research question: What are the effect(s) of fiber-containing foods and/or supplements on digestive health outcomes in children? A search of the PubMed database identified a total of 12 studies that fit the inclusion criteria established for this review. Most of the evidence in children shows beneficial effects of partially hydrolyzed guar gum, glucomannan, and bran on digestive health outcomes; however, the existing evidence is not conclusive. Furthermore, limited data exists on the effect of whole-grain sources of dietary fiber, such as oats. Additional well-designed intervention trials are needed to determine whether outcomes of digestive health such as stool form, gastrointestinal tolerance, and stool frequency are improved by increasing the fiber content of children's diets with whole-grain sources.
Topics: Child; Child Health; Dietary Fiber; Gastrointestinal Diseases; Humans
PubMed: 28586481
DOI: 10.1093/nutrit/nuw068 -
Advances in Nutrition (Bethesda, Md.) Dec 2022Nondigestible carbohydrates (NDCs) are food components, including nonstarch polysaccharides and resistant starches. Many NDCs are classified as dietary fibers by the US... (Review)
Review
Nondigestible carbohydrates (NDCs) are food components, including nonstarch polysaccharides and resistant starches. Many NDCs are classified as dietary fibers by the US FDA. Because of their beneficial effects on human health and product development, NDCs are widely used in the food supply. Although there are dietary intake recommendations for total dietary fiber, there are no such recommendations for individual NDCs. NDCs are heterogeneous in their chemical composition and physicochemical properties-characteristics that contribute to their tolerable intake levels. Guidance on tolerable intake levels of different NDCs is needed because overconsumption can lead to undesirable gastrointestinal side effects, further widening the gap between actual and suggested fiber intake levels. In this review, we synthesize the literature on gastrointestinal effects of NDCs that the FDA accepts as dietary fibers (β-glucan, pectin, arabinoxylan, guar gum, alginate, psyllium husk, inulin, fructooligosaccharides and oligofructose, galactooligosaccharides, polydextrose, cellulose, soy fiber, resistant maltodextrin/dextrin) and present tolerable intake dose recommendations for their consumption. We summarized the findings from 103 clinical trials in adults without gastrointestinal disease who reported gastrointestinal effects, including tolerance (e.g., bloating, flatulence, borborygmi/rumbling) and function (e.g., transit time, stool frequency, stool consistency). These studies provided doses ranging from 0.75-160 g/d and lasted for durations ranging from a single-meal tolerance test to 28 wk. Tolerance was NDC specific; thus, recommendations ranged from 3.75 g/d for alginate to 25 g/d for soy fiber. Future studies should address gaps in the literature by testing a wider range of NDC doses and consumption forms (solid compared with liquid). Furthermore, future investigations should also adopt a standard protocol to examine tolerance and functional outcomes across studies consistently.
Topics: Adult; Humans; Gastrointestinal Tract; Carbohydrates; Dietary Fiber; Feces; Alginates
PubMed: 36041173
DOI: 10.1093/advances/nmac094 -
Gastroenterology Clinics of North... Dec 2017Dietary fiber, specifically prebiotics, is the primary source of energy for the gut microbiota and thus has the potential to beneficially modify microbiota composition.... (Review)
Review
Dietary fiber, specifically prebiotics, is the primary source of energy for the gut microbiota and thus has the potential to beneficially modify microbiota composition. Prebiotics have been used in both in vitro studies and with animal models of colitis with largely positive results. Human studies are few and have been conducted with only a few select prebiotics, primarily fructan-containing fibers. Although disease activity and inflammatory markers have improved, more needs to be learned about the specific prebiotic compounds and how they can be used to best improve the gut microbiota to counter changes induced by inflammatory bowel disease.
Topics: Animals; Dietary Fiber; Gastrointestinal Microbiome; Humans; Inflammatory Bowel Diseases; Prebiotics
PubMed: 29173521
DOI: 10.1016/j.gtc.2017.08.004 -
International Journal of Food Sciences... Nov 2023Diet is a critical regulator for physiological metabolism and tissue homeostasis, with a close relation to health and disease. As an important organ for digestion and... (Review)
Review
Diet is a critical regulator for physiological metabolism and tissue homeostasis, with a close relation to health and disease. As an important organ for digestion and absorption, the intestine comes into direct contact with many dietary components. The rapid renewal of its mucosal epithelium depends on the continuous proliferation and differentiation of intestinal stem cells (ISCs). The function and metabolism of ISCs can be controlled by a variety of dietary patterns including calorie restriction, fasting, high-fat, ketogenic, and high-sugar diets, as well as different nutrients including vitamins, amino acids, dietary fibre, and probiotics. Therefore, dietary interventions targeting ISCs may make it possible to prevent and treat intestinal disorders such as colon cancer, inflammatory bowel disease, and radiation enteritis. This review summarised recent research on the role and mechanism of diet in regulating ISCs, and discussed the potential of dietary modulation for intestinal diseases.
Topics: Humans; Intestines; Diet; Stem Cells; Inflammatory Bowel Diseases; Dietary Fiber; Intestinal Mucosa
PubMed: 37758199
DOI: 10.1080/09637486.2023.2262780