Fibre is More than Roughage
Dr David L Topping BSc, PhD, FTSE, FNSA, MAIFST
Dr David L Topping BSc, PhD, FTSE, FNSA, MAIFST David Topping is an Honorary Fellow with Australia’s Commonwealth Scientific and Industrial Research Organisation Health and Biosecurity in Adelaide. His main research focus for 40 years has been principally the relationship between fibre and gut health. He is the author of over 180 papers and book chapters. He is a Fellow of the Academy of Technology and Engineering and the Nutrition Society of Australia and is a professional member of the Australian Institute of Food Science and Technology. Here, Dr Topping presents the idea and supporting evidence that fibre supports healthy gut structure and function
Wholegrain foods made from a novel high-amylose barley variety (Himalaya 292) improve indices of bowel health in human subjects.
Bird AR, Vuaran MS, King RA, Noakes M, Keogh J, Morell MK, Topping DL. British Journal of Nutrition. 2008;99:1032–1040
Himalaya 292 is a new barley cultivar with altered starch synthesis and less total starch but more amylose, resistant starch and total and soluble non-starch polysacharide including beta-glucan. The authors of this paper conclude that “consumption of a diet that included foods made from Himalaya 292 supplied more fibre and improved indices of bowel health compared with refined cereal foods and, for some indices, similar wholemeal wheat foods at equivalent levels of intake.”
An extruded breakfast cereal made from a high amylose barley cultivar has a low glycemic index and lower plasma insulin response than one made from a standard barley
King RA, Noakes M, Bird AR, Morell MK, Topping DL. Journal of Cereal Science. 2008.48:526e- 530.
Himalaya 292 is a novel hull-less barley cultivar with lower total starch content, a higher proportion of amylose and a substantially higher
content of soluble and insoluble fibre. The authors of this paper conclude that “The data confirm that Himalaya 292 may be of value in foods designed to assist in the prevention and management of diabetes”.
Short-chain fatty acids and human colonic function: roles of resistant starch and nonstarch polysaccharides
Topping DL, Clifton PM. Physiol Rev. 2001;81(3):1031-64.
This seminal paper discusses resistant starch as a prebiotic and its contribution to fermentation and colonic physiology.
Influence of diet on the gut microbiome and implications for human health
Singh RK, Chang H, Yan D, Lee KM, Ucmak D, Wong K et al. Journal of Translational Medicine. 2017;15:73
Recent evidence suggests that the intestinal microbiome plays an important role in modulating risk of several chronic diseases, including inflammatory bowel disease, obesity, type 2 diabetes, cardiovascular disease and cancer. It is also understood that diet plays a significant role in shaping the microbiome, with experiments showing that dietary alterations can induce large, temporary microbial shifts within 24 h. This review paper examines current data on the effects of several common dietary components on intestinal microbiota, showing that consumption of particular types of food produces predictable shifts in existing host bacterial genera. Importantly, whole grains are shown to result in an increase intestinal Bifidobacteria and Lactobacilli.
Dietary modulation of the human colonic microbiota: updating the concept of prebiotics
Gibson GR, Probert HM, Loo JV, Rastall RA, Roberfroid MB. Nutr Res Rev. 2004;17(2):259-75.
In this paper, the authors define prebiotics, highlighting that prebiotics are non-digestible (by the host) food ingredients that have a beneficial effect through their selective metabolism in the intestinal tract. Key to this is the specificity of microbial changes.
Feeding a hungry microbiome: large bowel fermentation and human health
Topping DL & Conlon ML. Med Journal Aust. 2014;201 (8): 438.
This short communication presents a review that “Emerging evidence now shows that many of the actions of fibre are mediated through short chain fatty acids (SCFAs), principally acetate, propionate and butyrate, produced by the fermentation of its constituents by beneficial large-bowel bacteria. Evidence is growing that SCFAs are important for general health as well as for normal gut function.“
Microbial regulation of microRNA expression in the amygdala and prefrontal cortex
Hoban AE, Roman M. Stilling, Gerard M. Moloney, Rachel D. Moloney, Fergus Shanahan, Timothy G. Dinan, John F. Cryan and Gerard Clarke. Microbiome. 2017;5:102
Recent evidence in the scientific literature highlights that the gut microbiota may act as a key regulator of brain and behaviour. This rodent study provides mechanistic insights into how this may be occurring, by comparing germ-free mice with conventional mice, and examining differences between these 2 groups in their amygdala and prefrontal cortex miRNAs. The neural circuits that underlie anxiety- and fear-related behaviours depend heavily on functional communication between the amygdala and prefrontal cortex. The authors concluded that results of their study indicated “that appropriate regulation of miRNA expression within the amygdala and prefrontal cortex is influenced by microbiota composition and activity and relies on the presence of a functional microbiota during critical windows of neurodevelopment.”
Fiber and Prebiotics: Mechanisms and Health Benefits
Slavin J. Nutrients. 2013;5(4):1417-1435.
This review paper discusses the health benefits of fibre and more specifically, prebiotic fibres, which are defined as ‘a selectively fermented ingredient that allows specific changes, both in the composition and/or activity in the gastrointestinal microflora that confer benefits upon host well-bring and health.’ To date, all known and suspected prebiotics are carbohydrate compounds, primarily oligosaccharides, known to resist digestion in the human small intestine and reach the colon where they are fermented by the gut microflora. Studies provide evidence that inulin and oligofructose, lactulose and resistant starch meet all aspects of the definition, including the stimulation of Bifidobacterium, a beneficial bacterial genus.
Resistant Starch Research
Positive effects of resistant starch supplementation on bowel function in healthy adults: a systematic review and meta-analysis of randomized controlled trials
Shen D, Bai H, Li Z, et al. Int Journal Food Sci Nutr. 2017;68(2):149-57.
Systematic review of the effects of the intestinal microbiota on selected nutrients and non-nutrients
Shortt C, Hasselwander O, Meynier A, Nauta A, Fernández EN, Putz P, et al. Eur Journal Nutr. 2017; doi: 10.1007/s00394-017-1546-4. [Epub ahead of print]
Intakes of resistant starch and prebiotics alter levels of specific bacteria taxa that selectively metabolise specific prebiotic/carbohydrate-type substances and levels of bifidobacteria and lactobacilli are observed to increase. In controlled human studies, consistent data exist to show a correlation between the intake of fibre and an increase in bifidobacteria and short-chain fatty acids, in particular butyrate, which leads to lower intestinal pH.
Resistant starch can improve insulin sensitivity independently of the gut microbiota
Bindels LB, Segura Munoz RR, Gomes-Neto JC, Mutemberezi V, Martínez I, Salazar N, et al. Microbiome. 2017;5 (1).
Resistant starches types 2 and 4 have differential effects on the composition of the fecal microbiota in human subjects
Martinez I, Kim J, Duffy PR, et al. PloS ONE. 2010;5(11):e15046.
Dietary manipulation of oncogenic microRNA expression in human rectal mucosa: a randomized trial
Humphreys KJ, Conlon MA, Young GP, Topping DL, Hu Y, Winter JM, et al. Cancer Prev Res (Phila). 2014;7(8):786-95.
Authors of this study conclude that their findings support the idea of increased resistant starch consumption as a means of reducing risk associated with an high red meat diet.
Resistant starch intakes in the United States
Murphy MM, Douglass JS, Birkett A. Journal American Diet Assoc. 2008;108(1):67-78.
Resistant starch is starch that escapes digestion in the small intestine and may be fermented in the large intestine. In this paper, researchers estimate that resistant starch consumption by the US population is approximately 3 to 8 g per person per day, with bread, cereals/pasta and vegetables (other than legumes) contributing 21%, 19% and 19 % respectively to total resistant starch intake.
Resistant Starch Alters the Microbiota-Gut Brain Axis: Implications for Dietary Modulation of Behavior
Lyte M, Chapel A, Lyte JM, et al. PloS ONE. 2016;11(1):e0146406.
Resistant starch alters the gut microbiota profile in mice.
Fibre is more than just Roughage
Understanding the Physics of Functional Fibers in the Gastrointestinal Tract: An Evidence-Based Approach to Resolving Enduring Misconceptions about Insoluble and Soluble Fiber
McRorie JW Jr, McKeown NM. J Acad Nutr Diet. 2017;117(2):251-264.
Enduring misconceptions about the physical effects of fibre in the gut have led to misunderstandings about the health benefits attributable to insoluble and soluble fibre. This review focuses on three health benefits (cholesterol lowering, improved glycaemic control, and normalising stool form [constipation and diarrhoea]) for which reproducible evidence of clinical efficacy has been published.
The physiological roles of dietary fibre
Brownlee IA. Food Hydrocolloids. 2011;25:238-250.
The large intestine houses a varied microflora. Dietary fibre is a major energy source for these bacteria, and therefore markedly affects microfloral diversity/toxicity. Dietary fibres can also affect innate immune responses of the gut mucosa both directly and indirectly.
Review article: dietary fibre in the era of microbiome science
O’Grady J, O’Connor EM, Shanahan F. Review article: dietary fibre in the era of microbiome science. Aliment Pharmacol Ther. 2019;49:506–515.
The physical properties of dietary fibres are important for homeostasis within the gut, but the predominant health benefits extend beyond the gut to enhanced metabolic welfare, including protection against obesity and related metabolic diseases. Fibre is a form of functional food joining a growing list of examples of diet‐microbe‐host interactions which link microbe‐host metabolic and immune cascades.
Whole Grain Intake and Disease Risk Reduction
Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project
Vieira AR, Abar L, Chan, DSM, Vingeliene S, Polemiti E, Stevens C, et al. Annals of Oncology. 2017; 28(8):1788–1802.
This systematic review and meta-analysis of around 400 prospective studies as part of the World Cancer Research Fund International Continuous Update Project, examines the evidence on the relationship between food and beverage intake and colorectal cancer risk. Results demonstrated a colorectal cancer risk decrease of 17% for each 90g/day increase in intake of whole grains, leading the authors to conclude that “whole grains may have a protective role against colorectal cancer.”
Whole grain consumption and risk of cardiovascular disease, cancer, and all cause and cause specific mortality: systematic review and dose-response meta-analysis of prospective studies
Aune D, Keum N, Giovannucci E, Fadnes LT, Boffetta P, Greenwood DC, et al. British Medical Journal. 2016;14;353:i2716.
The authors conclude that their “meta-analysis provides further evidence that whole grain intake is associated with a reduced risk of coronary heart disease, cardiovascular disease, and total cancer, and mortality from all causes, respiratory diseases, infectious diseases, diabetes, and all non-cardiovascular, non-cancer causes. These findings support dietary guidelines that recommend increased intake of whole grain to reduce the risk of chronic diseases and premature mortality.”
Whole-grain intake and total, cardiovascular, and cancer mortality: a systematic review and meta-analysis of prospective studies
Chen GC, Tong X, Xu JY, Han SF, Wan ZX, Qin JB, Qin LQ. American Journal Clinical Nut. 2016;104(1):164-72.
The authors conclude that their “findings suggest significant inverse relations between whole grain intake and mortality due to any cause, CVD, or cancer. The findings support the recommendation of increasing whole-grain intake to improve public health.”
Whole Grain Intake and Mortality From All Causes, Cardiovascular Disease, and Cancer: A Meta-Analysis of Prospective Cohort Studies
Zong G, Gao A, Hu FB, Sun Q. Circulation. 201614;133(24):2370-80.
The authors conclude that their meta-analysis “demonstrated inverse associations of whole grain intake with total and cause-specific mortality, and findings were particularly strong and robust for CVD mortality.”
Whole grain, bran, and germ intake and risk of type 2 diabetes: a prospective cohort study and systematic review
de Munter JS, Hu FB, Spiegelman D, Franz M, van Dam RM. PLoS Med. 2007;4(8):e261.
The authors conclude from their cohort study and systematic review that “Whole grain intake is inversely associated with risk of type 2 diabetes, and this association is stronger for bran than for germ. Findings from prospective cohort studies consistently support increasing whole grain consumption for the prevention of type 2 diabetes.”
Diets that differ in their FODMAP content alter the colonic luminal microenvironment
Halmos EP, Christophersen CT, Bird AR, Shepherd SJ, Gibson PR, Muir JG. Gut. 2015;64(1):93-100.
FODMAPs are fermentable carbohydrates, some of which have prebiotic effects and consequent benefits to large bowel health. Diets low in FODMAPs reduce GI symptoms in around 75% of patients with irritable bowel syndrome, but also appear to reduce the proportion and concentration of faecal Bifidobacteria spp bacterial versus a habitual diet. The authors here suggest that: a) A low FODMAP diet should not be recommended for asymptomatic populations; b) Caution should be taken when recommending the low FODMAP diet long-term; and c) Liberalising FODMAP restriction to the level of adequate symptom control should be exercised to use the potential health benefits of higher FODMAP intake on the gut microbiota.
Consistent Prebiotic Effect on Gut Microbiota With Altered FODMAP Intake in Patients with Crohn’s Disease: A Randomised, Controlled Cross-Over Trial of Well-Defined Diets
Halmos EP, Christophersen CT, Bird AR, Shepherd SJ, Muir JG, Gibson PR. Clinical and Translational Gastroenterology. 2016;14(7):e164.
The authors here conclude that “In clinically quiescent Crohn's disease, altering dietary FODMAP intake is associated with marked changes in faecal microbiota, most consistent with a prebiotic effect of increasing FODMAPs as shown in an irritable bowel/healthy cohort. This strategy might be favourable for gut health in Crohn's disease, but at the cost of inducing symptoms.”
Breakfast Cereals and Nutrition Intake
Breakfast and Breakfast Cereal Choice and Its Impact on Nutrient and Sugar Intakes and Anthropometric Measures among a Nationally Representative Sample of Australian Children and Adolescents
Fayet-Moore F, McConnell A, Tuck K, Petocz P. Nutrients. 2017;9(10):1045.
There is limited evidence in Australia that compares the nutritional impact of a breakfast cereal breakfast to a non-cereal breakfast, and includes the type of cereal. This study investigated the impact of breakfast choice and the total sugar content of breakfast cereal on nutrient intakes and anthropometric measures among Australian children and adolescents.
Breakfast Choice Is Associated with Nutrient, Food Group and Discretionary Intakes in Australian Adults at Both Breakfast and the Rest of the Day
Flavia Fayet-Moore 1,*, Andrew McConnell 1, Tim Cassettari 1 and Peter Petocz 2
Breakfast choice is correlated with daily nutrient intakes, but this association may not be
solely explained by the breakfast meal. We profiled breakfast consumer groups among Australian
adults and compared the role that breakfast versus the rest of the day had on daily intakes of
the Five Food Groups, discretionary foods, and nutrients.