Abstract:Dietary fiber intervention, particularly involving fructans and galacto-oligosaccharides, leads to higher fecal abundance of Bifidobacterium and Lactobacillus spp. but does not affect α-diversity. Further research is required to better understand the role of individual fiber types on the growth of microbes and the overall gut microbial community. This review was registered at PROSPERO as CRD42016053101.
“…Some, 58 but not all, 59 studies have shown that higher fiber intake enriches Lactobacillus spp. and butyrate-producing bacteria in the gut, such as Bifidobacterium, Clostridium, Anaerostipes, Eubacterium, and Roseburia species, and increases production of SCFAs.…”
The substantial burden of colorectal cancer and increasing trend in young adults highlight the importance of lifestyle modification as a complement to screening for colorectal cancer prevention. Several dietary and lifestyle factors have been implicated in the development of colorectal cancer, possibly through the intricate metabolic and inflammatory mechanisms. Likewise, as a key metabolic and immune regulator, the gut microbiota has been recognized to play an important role in colorectal tumorigenesis. Increasing data support that environmental factors are crucial determinants for the gut microbial composition and function, whose alterations induce changes in the host gene expression, metabolic regulation, and local and systemic immune response, thereby influencing cancer development. Here, we review the epidemiologic and mechanistic evidence regarding the links between diet and lifestyle and the gut microbiota in the development of colorectal cancer. We focus on factors for which substantial data support their importance for colorectal cancer and their potential role in the gut microbiota, including overweight and obesity, physical activity, dietary patterns, fiber, red and processed meat, marine omega-3 fatty acid, alcohol, and smoking. We also briefly describe other colorectal cancer-preventive factors for which the links with the gut microbiota have been suggested but remain to be mechanistically characterized, including vitamin D status, dairy consumption, and metformin use. Given limitations in available evidence, we highlight the need for further investigations in the relationship between environmental factors, gut microbiota, and colorectal cancer, which may lead to development and clinical translation of potential microbiota-based strategies for cancer prevention.
“…Some, 58 but not all, 59 studies have shown that higher fiber intake enriches Lactobacillus spp. and butyrate-producing bacteria in the gut, such as Bifidobacterium, Clostridium, Anaerostipes, Eubacterium, and Roseburia species, and increases production of SCFAs.…”
The substantial burden of colorectal cancer and increasing trend in young adults highlight the importance of lifestyle modification as a complement to screening for colorectal cancer prevention. Several dietary and lifestyle factors have been implicated in the development of colorectal cancer, possibly through the intricate metabolic and inflammatory mechanisms. Likewise, as a key metabolic and immune regulator, the gut microbiota has been recognized to play an important role in colorectal tumorigenesis. Increasing data support that environmental factors are crucial determinants for the gut microbial composition and function, whose alterations induce changes in the host gene expression, metabolic regulation, and local and systemic immune response, thereby influencing cancer development. Here, we review the epidemiologic and mechanistic evidence regarding the links between diet and lifestyle and the gut microbiota in the development of colorectal cancer. We focus on factors for which substantial data support their importance for colorectal cancer and their potential role in the gut microbiota, including overweight and obesity, physical activity, dietary patterns, fiber, red and processed meat, marine omega-3 fatty acid, alcohol, and smoking. We also briefly describe other colorectal cancer-preventive factors for which the links with the gut microbiota have been suggested but remain to be mechanistically characterized, including vitamin D status, dairy consumption, and metformin use. Given limitations in available evidence, we highlight the need for further investigations in the relationship between environmental factors, gut microbiota, and colorectal cancer, which may lead to development and clinical translation of potential microbiota-based strategies for cancer prevention.
“…There is abundant literature concerning the effects of dietary fibre on the growth of Bifidobacterium and Lactobacillus spp. (So et al, 2018), however dietary fibre can also stimulate other microbes.…”
Section: Furthermore Intestinal Bacteria Including Lactobacillus Andmentioning
Dietary fibre, such as indigestible oligosaccharides and polysaccharides, occurs in many foods and has gained considerable importance related to its beneficial effects on host health and specific diseases. Dietary fibre is neither digested nor absorbed in the small intestine and modulates the composition of the gut microbiota. New evidence indicates that dietary fibre also interacts directly with the epithelium and immune cells throughout the gastrointestinal tract by microbiota‐independent effects. This review focuses on how dietary fibre improves human health and the reported health benefits that are connected to molecular pathways, in (a) a microbiota‐independent manner, via interaction with specific surface receptors on epithelial and immune cells regulating intestinal barrier and immune function, and (b) a microbiota‐dependent manner via maintaining intestinal homeostasis by promoting beneficial microbes, including Bifidobacteria and Lactobacilli, limiting the growth, adhesion, and cytotoxicity of pathogenic microbes, as well as stimulating fibre‐derived microbial short‐chain fatty acid production.
Linked Articles
This article is part of a themed section on The Pharmacology of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.6/issuetoc
“…Based on six RCTs that reported data suitable for inclusion in the meta‐analysis (investigating polydextrose, xylo‐oligosaccharide, polysaccharopeptide, arabinoxylans and a high‐fibre diet), fibre had no effect on α‐diversity compared with control (So et al . ). Of a further seven studies reporting α‐diversity that were not included in the main meta‐analysis, two reported increases in diversity after the consumption of resistant starch type 2 (Alfa et al .…”
Section: Microbial Fermentation Of Fibrementioning
confidence: 97%
“…So et al . () did not carry out subgroup analysis by fibre type and, at present, there are few studies that have measured the effect of prebiotics on microbial diversity. The net results of selective stimulation of beneficial species, the growth of which produces an unfavourable environment for pathogenic species due to the production of metabolites which reduce intestinal pH, and the stimulation of other species, may vary between individuals due to the baseline composition, prebiotic dose and wider composition of the diet; therefore, affects on diversity may be difficult to predict (Holscher ).Diets higher in fibre are associated with a decreased risk of CVD, type 2 diabetes and colorectal cancer.RCTs demonstrate that fibre decreases transit time and increases faecal bulk, reducing constipation.…”
Section: Microbial Fermentation Of Fibrementioning
confidence: 99%
“…Currently accepted prebiotics increase bifidobacteria in the human gut (SACN 2015;So et al 2018). This is thought to benefit human health through the displacement of pathogens and modulation of the immune system (Wallace et al 2011).…”
Prebiotics are food components that are selectively used by gut bacteria, conferring a health benefit, most notably stimulating the growth of bifidobacteria. Accepted prebiotics at present are the fibre types galacto‐oligosaccharides, fructo‐oligosaccharides and inulin, some forms of which occur naturally in foods such as pulses, grains, fruit and vegetables. Prebiotics can also be isolated and produced commercially for use as functional ingredients and supplements. The aim of this paper is to provide an overview of the place of prebiotics in a healthy, balanced diet, to explore potential health effects, particularly in relation to gut health, and to consider whether there are implications of consuming a diet low in prebiotics. Dietary fibre is important for health, with high‐fibre diets reducing risk of several chronic diseases, via its effects on bowel function, gut microbiota, and cholesterol and glycaemic levels. The prebiotic effects of some fibre types may contribute to these effects. Evidence from supplementation studies carried out in humans suggests that consumption of prebiotics may confer an array of health benefits such as cholesterol lowering, relief of symptoms of gastrointestinal disorders, increased satiety and immunomodulatory effects, though more studies are needed. Findings from observational and intervention studies indicate that exclusion diets, such as low‐carbohydrate, gluten‐free and the low Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols diet, result in changes to the gut microbiota such as reduced abundance of Bifidobacterium and Lactobacillus species, though whether or not there are any long‐term health implications remains unknown. Studies investigating whether prebiotic supplements may be useful in conjunction with such diets (when these are required for medical reasons) to help restore levels of bacteria that are considered to be beneficial, are warranted. Overall, there is a need to promote high‐fibre foods across the UK population as intakes currently fall well below recommendations.
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