Effects Of Non-digestible Carbohydrates Research Articles

Structure and function of non-digestible carbohydrates in the gut microbiome.

Together with proteins and fats, carbohydrates are one of the macronutrients in the human diet. Digestible carbohydrates, such as starch, starch-based products, sucrose, lactose, glucose and some sugar alcohols and unusual (and fairly rare) α-linked glucans, directly provide us with energy while other carbohydrates including high molecular weight polysaccharides, mainly from plant cell walls, provide us with dietary fibre. Carbohydrates which are efficiently digested in the small intestine are not available in appreciable quantities to act as substrates for gut bacteria. Some oligo- and polysaccharides, many of which are also dietary fibres, are resistant to digestion in the small intestines and enter the colon where they provide substrates for the complex bacterial ecosystem that resides there. This review will focus on these non-digestible carbohydrates (NDC) and examine their impact on the gut microbiota and their physiological impact. Of particular focus will be the potential of non-digestible carbohydrates to act as prebiotics, but the review will also evaluate direct effects of NDC on human cells and systems.

Current Research on the Effects of Non-Digestible Carbohydrates on Metabolic Disease

Metabolic diseases (MDs), including cardiovascular diseases (CVDs) and diabetes, occur when the body’s normal metabolic processes are disrupted. Behavioral risk factors such as obesity, physical inactivity, and dietary habits are strongly associated with a higher risk of MD. However, scientific evidence strongly suggests that balanced, healthy diets containing non-digestible carbohydrates (NDCs), such as dietary fiber and resistant starch, can reduce the risk of developing MD. In particular, major properties of NDCs, such as water retention, fecal bulking, viscosity, and fermentation in the gut, have been found to be important for reducing the risk of MD by decreasing blood glucose and lipid levels, increasing satiety and insulin sensitivity, and modifying the gut microbiome. Short chain fatty acids produced during the fermentation of NDCs in the gut are mainly responsible for improvement in MD. However, the effects of NDCs are dependent on the type, source, dose, and duration of NDC intake, and some of the mechanisms underlying the efficacy of NDCs on MD remain unclear. In this review, we briefly summarize current studies on the effects of NDCs on MD and discuss potential mechanisms that might contribute to further understanding these effects.

Pooled faecal inoculum can predict infant fiber fermentability despite high inter-individual variability of microbiota composition

Infants are known for their high inter-individual variability in gut microbiota composition in the first months of life. This poses difficulties when predicting the fate of non-digestible carbohydrates (NDCs) in the infant gut using in vitro models, since numerous experiments with individual faecal inocula of different infants are required. In this study an in vitro fermentation experiment was performed with galacto-oligosaccharides (GOS) using both individual and pooled faecal inocula of five two-week-old infants. It was shown that pooled faecal inoculum can be used to judge the fermentability of GOS, as a similar trend in total organic acid production and relative increase in Bifidobacterium was observed for the pooled faecal inoculum and four out of five individual faecal inocula. An additional fermentation using pooled faecal inoculum of five other infants of the same age confirmed these findings. Additionally, we provided evidence for both size- and isomer-specific fermentation of GOS by infant microbiota, which reveals the potential for the production of tailored NDC mixtures to meet the needs of specific subgroups of infants. Hence, the use of pooled faecal inocula contributes to increasing our knowledge on structure-specific effects of NDCs in infants efficiently.

Modulation of Intestinal Epithelial Glycocalyx Development by Human Milk Oligosaccharides and Non-Digestible Carbohydrates.

ScopeThe epithelial glycocalyx development is of great importance for microbial colonization. Human milk oligosaccharides (hMOs) and non‐digestible carbohydrates (NDCs) may modulate glycocalyx development.Methods and resultsThe effects of hMOs and NDCs on human gut epithelial cells (Caco2) are investigated by quantifying thickness and area coverage of adsorbed albumin, heparan sulfate (HS), and hyaluronic acid (HA) in the glycocalyx. Effects of hMOs (2′‐FL and 3‐FL) and NDCs [inulins with degrees of polymerization (DP) (DP3‐DP10, DP10‐DP60, DP30‐DP60) and pectins with degrees of methylation (DM) (DM7, DM55, DM69)] are tested using immunofluorescence staining at 1 and 5 days stimulation. HMOs show a significant enhancing effect on glycocalyx development but effects are structure‐dependent. 3‐FL induces a stronger albumin adsorption and increases HS and HA stronger than 2′‐FL. The DP3‐DP10, DP30‐60 inulins also increase glycocalyx development in a structure‐dependent manner as DP3‐DP10 selectively increases HS, while DP30‐DP60 specifically increases HA. Pectins have less effects, and only increase albumin adsorption.ConclusionHere, it is shown that 2′‐FL and 3‐FL and inulins stimulate glycocalyx development in a structure‐dependent fashion. This may contribute to formulation of effective hMO and NDC formulations in infant formulas to support microbial colonization and gut barrier function.

Ingestion of Non-digestible Carbohydrates From Plant-Source Foods and Decreased Risk of Colorectal Cancer: A Review on the Biological Effects and the Mechanisms of Action.

The hypothesis that links the increase in the intake of plant-source foods to a decrease in colorectal cancer (CRC) risk has almost 50 years. Nowadays, systematic reviews and meta-analysis of case-control and cohort studies confirmed the association between dietary patterns and CRC risk, in which the non-digestible carbohydrates (NDC) from plant-source foods are known to play beneficial effects. However, the mechanisms behind the physicochemical properties and biological effects induced by NDC on the decrease of CRC development and progression remain not fully understood. NDC from plant-source foods consist mainly of complex carbohydrates from plant cell wall including pectin and hemicellulose, which vary among foods in structure and in composition, therefore in both physicochemical properties and biological effects. In the present review, we highlighted the mechanisms and described the recent findings showing how these complex NDC from plant-source foods are related to a decrease in CRC risk through induction of both physicochemical effects in the gastrointestinal tract, fermentation-related effects, and direct effects resulting from the interaction between NDC and cellular components including toll-like receptors and galectin-3. Studies support that the definition of the structure-function relationship—especially regarding the fermentation-related effects of NDC, as well as the direct effects of these complex carbohydrates in cells—is crucial for understanding the possible NDC anticancer effects. The dietary recommendations for the intake of NDC are usually quantitative, describing a defined amount of intake per day. However, as NDC from plant-source foods can exert effects that vary widely according to the NDC structure, the dietary recommendations for the intake of NDC plant-source foods are expected to change from a quantitative to a qualitative perspective in the next few years, as occurred for lipid recommendations. Thus, further studies are necessary to define whether specific and well-characterized NDC from plant-source foods induce beneficial effects related to a decrease in CRC risk, thereby improving nutritional recommendations of healthy individuals and CRC patients.

Potential anti-obesogenic properties of non-digestible carbohydrates: specific focus on resistant dextrin.

Alterations in the composition and metabolic activity of the gut microbiota appear to contribute to the development of obesity and associated metabolic diseases. However, the extent of this relationship remains unknown. Modulating the gut microbiota with non-digestible carbohydrates (NDC) may exert anti-obesogenic effects through various metabolic pathways including changes to appetite regulation, glucose and lipid metabolism and inflammation. The NDC vary in physicochemical structure and this may govern their physical properties and fermentation by specific gut bacterial populations. Much research in this area has focused on established prebiotics, especially fructans (i.e. inulin and fructo-oligosaccharides); however, there is increasing interest in the metabolic effects of other NDC, such as resistant dextrin. Data presented in this review provide evidence from mechanistic and intervention studies that certain fermentable NDC, including resistant dextrin, are able to modulate the gut microbiota and may alter metabolic process associated with obesity, including appetite regulation, energy and lipid metabolism and inflammation. To confirm these effects and elucidate the responsible mechanisms, further well-controlled human intervention studies are required to investigate the impact of NDC on the composition and function of the gut microbiota and at the same time determine concomitant effects on host metabolism and physiology.

Evidence-based benefits of specific mixtures of non-digestible oligosaccharides on the immune system

Non-digestible carbohydrates (NDC) are natural constituents of many foods. They are mostly referred to as dietary fibre and are associated with many health benefits mostly connected to gut health. NDC have emerged as a promising nutritional concept to modulate immune function as well. In the world of immunology non-digestible carbohydrates are recognized now as key immunomodulating molecules. Both pharma and food industries realize the enormous potency of these immune active components. Although the mechanisms underlying the effects of NDC on the immune system are not totally clear yet many studies have reported beneficial effects on both mucosal and systemic immunity in humans. The aim of this review is to summarize the available evidence on the immune modulatory effects of specific mixtures of oligosaccharides. Both mechanistic in vitro and in vivo studies have been performed and will be discussed. Finally the potential use of these unique structures will be evaluated.

Effects of Non-Digestible Carbohydrates on the Growth of Estrogen-Dependent Human Breast Cancer (MCF-7) Tumors Implanted in Ovariectomized Athymic Mice

Non-digestible carbohydrates (NDC 4 ) have been used as a low-calorie sweetener and prebiotics that stimulate the growth of certain intestinal bacteria that support healthy colon conditions. In this study, we examined the dietary effect of commercially available NDCs on estrogen receptor positive (ER+) human breast cancer. We conducted a feeding study of fructooligosaccharides (FOSs), Fibersol 2 (F2; digestion resistant maltodextrin), Hi-Maize (HM; high amylose cornstarch), and Frutafit (FF; a range of powdered inulins) (5% in diet, w/w) to evaluate their effects on the growth of ER(+) human breast cancer (MCF-7) tumors in the presence of 17β-estradiol (E2) using an athymic xenograft model. F2, HM, and FOSs supplementation significantly reduced E2-stimulated MCF-7 tumor growth by inhibiting cellular proliferation (Ki-67) and increasing apoptosis (M30) in tumors. F2, HM, and FOSs treatments also lowered serum E2 level and reduced uterine weight compared to the control diet. NDCs treatments downregulated relative mRNA expression of the E2-responsive gene markers pS2, bcl2, bcl-xL, and cyclin D1 in MCF-7 tumors. In conclusion, the NDC intake may have a protective effect against ER(+) tumors by inhibiting cellular proliferation and increasing apoptosis.

Interactive and individual effects of dietary non-digestible carbohydrates and oils on DNA damage, SCFA and bacteria in the large bowel of rats

Dietary non-digestible carbohydrates (NDC) play an important role in large-bowel health and one form of NDC, resistant starch (RS), can promote low levels of DNA damage and other markers of colonic health. The objective of the present study was to determine whether the ability of dietary RS or other NDC to influence colonic health, particularly DNA damage, is dependent on the type of dietary oil. We compared the effects of diets containing 10 % of NDC from cellulose, wheat bran, high-amylose maize starch (HAS, a rich source of RS type 2) or a retrograded HAS (RHAS, a rich source of RS type 3) on DNA damage, SCFA production and bacterial changes in the large bowel of rats. Each carbohydrate source was combined with 10 % fish oil (FO) or Sunola oil (SO; rich in oleic acid). There was a significant interaction between NDC and oil treatments on single-strand DNA breaks in colonocytes isolated from the colon. The damage in rats consuming RHAS was greater for FO consumption than for SO consumption. There was a significant interaction between NDC and oils on caecum weights and treatment effects of NDC and oils were observed for the weights and lengths of other gut tissues. Significant differences were found in colonic SCFA pools and caecal numbers of lactobacilli, bifidobacteria, Escherichia coli and Bacteroides fragilis with the various NDC and oil treatments. The present results demonstrate that the effects of NDC and oils, particularly on colonic DNA damage, can depend on how they are combined within the diet.

Immune-Modulatory Effects and Potential Working Mechanisms of Orally Applied Nondigestible Carbohydrates

Orally applied nondigestible carbohydrates (NDC) have been associated with immune-modulating effects and other health benefits. The effects of prebiotic carbohydrates have recently received much attention, but other NDC have been reported to induce immune modulation as well. Many different effects have been shown on parameters of innate and specific immunity, mostly in animal experiments or in vitro. Data from clinical trials are limited, but promising studies have reported beneficial effects on mucosal and systemic immunity in humans. NDC are fermented to various degrees by the intestinal microbiota. Therefore, immune-modulatory properties have often been attributed to microbiota-dependent effects, especially in the case of prebiotic NDC. However, some NDC have been reported to bind to specific receptors on cells of the immune system, suggesting microbiota-independent, immune-modulatory effects play a role as well. This review aims to provide an overview of the published immune-modulatory effects in vitro and in vivo induced by NDC such as fructans, galactooligosaccharides, beta-glucans, pectins, and resistant starch. In addition, issues related to the underlying mechanisms are discussed: interaction between bacteria, their metabolites and the immune system, as well as direct effects of NDC via lectin receptors.