Beneficial effects of resistant starch on laxation in healthy adults

Consumption of Solnul™ Resistant Potato Starch Produces a Prebiotic Effect in a Randomized, Placebo-Controlled Clinical Trial

The effects of resistant starch at high doses have been well-characterized, but the potential prebiotic effects of resistant starch at doses comparable to oligosaccharide prebiotics have not been evaluated. A three-arm randomized, double-blind, placebo-controlled clinical trial was conducted to evaluate the effect of 3.5 g and 7 g daily doses of Solnul^™ resistant potato starch (RPS) on beneficial populations of gut bacteria and stool consistency after a 4-week period. The relative abundance of Bifidobacterium and Akkermansia was determined by employing 16Sv4 sequencing of stool samples. To assess the effect of RPS on laxation and bowel movements, stools were recorded and scored using the Bristol Stool Form Scale. Participants consuming 3.5 g/day of RPS experienced significantly greater changes in Bifidobacterium and Akkermansia compared to the placebo after 4 weeks. The number of diarrhea- and constipation-associated bowel movements were both significantly lower in the 3.5 g RPS arm compared to the placebo group. Participants consuming 7 g of RPS responded similarly to those in the 3.5 g arm. Our analyses demonstrate that Solnul^™ RPS has a prebiotic effect when consumed for 4 weeks at the 3.5 g per day dose, stimulating increases in beneficial health-associated bacteria and reducing diarrhea- and constipation-associated bowel movements when compared to the placebo group.

Substitution of Refined Conventional Wheat Flour with Wheat High in Resistant Starch Modulates the Intestinal Microbiota and Fecal Metabolites in Healthy Adults: A Randomized, Controlled Trial

BACKGROUND

Resistant starch (RS) confers many health benefits, mostly through the microbial production of SCFAs, but foods containing appreciable RS are limited. High-amylose wheat (HAW) is high in RS and lowers the glycemic response of foods, but whether it can improve gastrointestinal health measures is unknown.

OBJECTIVES

The objective of this study was to determine whether daily consumption of HAW food products improved markers of gastrointestinal health in healthy men and women compared with similar foods made from conventional wheat.

METHODS

Eighty healthy adults (47 women and 33 men) were enrolled in a 4-arm parallel, randomized-controlled, double-blind trial. After a 2-wk low-dietary fiber run-in period, they were randomly allocated to 1 of 4 treatment groups: low-amylose wheat (LAW)-refined (LAW-R), LAW-wholemeal (LAW-W), HAW-refined (HAW-R), and HAW-wholemeal (HAW-W) and consumed the assigned test bread (160 g/d) and biscuits (75 g/d) for 4 wk. Fecal biochemical markers were measured at baseline and 4 wk. Microbial abundance and diversity were quantified using 16S ribosomal RNA sequencing and perceived gut comfort by a semiquantitative questionnaire completed at baseline, 2 wk, and 4 wk.

RESULTS

HAW showed similar effects on fecal output and excretion of total SCFA compared with LAW, but changes were observed in secondary measures for the refined treatment groups. At 4 wk, the HAW-R group had 38% higher fecal butyrate excretion than the LAW-R group (P < 0.05), and higher fecal SCFA-producing bacteria, Roseburia inulinivorans (P < 0.001), than at baseline. In comparison with baseline, LAW-R increased fecal p-cresol concentration, and fecal abundance of a p-cresol-producing bacterium, Clostridium from the Peptostreptococcaceae family, but both were reduced by HAW-R. Amylose level did not affect measures of fecal consistency or adversely affecting digestive comfort.

CONCLUSIONS

Increasing RS intake of healthy adults by substituting refined conventional wheat with refined HAW modulates fecal metabolites and microbes associated with gastrointestinal health.This trial was registered at anzctr.org.au as ACTRN12618001060235.

Tolerability and SCFA production after resistant starch supplementation in humans: a systematic review of randomized controlled studies

BACKGROUND

Resistant starches (RSs) have been advocated as a dietary supplement to address microbiota dysbiosis. They are postulated to act through the production of SCFAs. Their clinical tolerability and effect on SCFA production has not been systematically evaluated.

OBJECTIVES

We conducted a systematic review of RS supplementation as an intervention in adults (healthy individuals and persons with medical conditions) participating in randomized controlled trials. The primary outcome was tolerability of RS supplementation, the secondary outcome was SCFA production.

METHODS

MEDLINE, Embase, and the Cochrane Central Register were searched. Articles were screened, and data extracted, independently and in duplicate.

RESULTS

A total of 39 trials met eligibility criteria, including a total of 2263 patients. Twenty-seven (69%) studies evaluated the impact of RS supplementation in healthy subjects whereas 12 (31%) studies included individuals with an underlying medical condition (e.g., obesity, prediabetes). Type 2 RS was most frequently investigated (29 studies). Of 12 studies performed in subjects with health conditions, 11 reported on tolerability. All studies showed that RS supplementation was tolerated; 9 of these studies used type 2 RS with doses of 20-40 g/d for >4 wk. Of 27 studies performed in healthy subjects, 20 reported on tolerability. In 14 studies, RS supplementation was tolerated, and the majority used type 2 RS with a dose between 20 and 40 g/d. Twenty-one (78%) studies reporting SCFAs used type 2 RS with a dose of 20-40 g/d for 1-4 wk. In 16 of 23 studies (70%), SCFA production was increased, in 7 studies there was no change in SCFA concentration before and after RS supplementation, and in 1 study SCFA concentration decreased.

CONCLUSIONS

Available evidence suggests that RS supplementation is tolerated in both healthy subjects and in those with an underlying medical condition. In addition, SCFA production was increased in most of the studies.

Resistant starch wheat increases PYY and decreases GIP but has no effect on self-reported perceptions of satiety

Dietary fiber has numerous health benefits, such as increasing satiety, and is regularly included in healthy dietary recommendations. However, different types and sources of fiber vary in their chemical properties and biological effects. This double-blind, randomized, placebo-controlled, crossover study investigated the effects of resistant starch type 2 (RS2) from wheat on self-reported perceptions of satiety and associated gut hormones in 30 healthy adults ages 40-65 years of age. Participants consumed rolls made using either RS2-enriched wheat flour or a wild-type flour for one week before a test day during which they ate a mixed meal containing the same roll type. Both self-reported perceptions of satiety and plasma concentrations of gut hormones were measured following the meal to assess whether the RS2-enriched wheat enhanced satiety and suppressed hunger for a longer period than the control wheat. Exploratory analysis indicated that fasting and peak concentration of peptide YY_3-36 (PYY_3-36; q_fast = 0.02, q_peak = 0.02) increased, while peak concentration and iAUC of glucose-dependent insulinotropic peptide (GIP; q_peak < 0.001, q_iAUC < 0.001) decreased after ingesting RS2-enriched wheat. However, self-reported perceptions of hunger or fullness using visual analog scales (VAS) did not differ following the test meal.

Effects of potato resistant starch intake on insulin sensitivity, related metabolic markers and appetite ratings in men and women at risk for type 2 diabetes: a pilot cross-over randomised controlled trial

Background

The intake of certain types of resistant starch (RS) has been associated in some studies with increased whole‐body insulin sensitivity. This randomised, cross‐over pilot trial evaluated the effect of consuming cooked, then chilled potatoes, a source of RS, compared to isoenergetic, carbohydrate (CHO)‐containing control foods, on insulin sensitivity and related markers.

Methods

Nineteen adults with body mass index 27.0‐39.9 kg m⁻² consumed 300 g day⁻¹ RS‐enriched potatoes (approximately two potatoes; ~18 g RS) or CHO‐based control foods, as part of lunch, evening and snack meals, over a 24‐h period. After an overnight fast, insulin sensitivity, CHO metabolism markers, free fatty acids, breath hydrogen levels and appetite were assessed for up to 5 h after the intake of a standard breakfast. The primary endpoint was insulin sensitivity, assessed with the Matsuda index. P < 0.05 (one‐sided) was considered statistically significant.

Results

Insulin sensitivity was not significantly different between the potato and control conditions. The potato intervention resulted in higher postprandial breath hydrogen (P = 0.037), lower postprandial free fatty acid concentrations (P = 0.039) and lower fasting plasma glucose (P = 0.043) compared to the control condition. Fullness ratings were significantly lower after potato versus control (P = 0.002). No other significant effects were observed; however, there was a trend toward lower fasting insulin (P = 0.077) in the potato versus the control condition.

Conclusions

The results of this pilot study suggest RS‐enriched potatoes may have a favourable impact on carbohydrate metabolism and support the view that additional research in a larger study sample is warranted.

Impact of Agaricus bisporus Mushroom Consumption on Gut Health Markers in Healthy Adults

Eating Agaricus bisporus mushrooms may impact gut health, because they contain known prebiotics. This study assessed mushroom consumption compared to meat on gastrointestinal tolerance, short chain fatty acid (SCFA) production, laxation, and fecal microbiota. A randomized open-label crossover study was conducted in healthy adults (n = 32) consuming protein-matched amounts of mushrooms or meat twice daily for ten days. Breath hydrogen measures were taken on day one, and gastrointestinal tolerance was evaluated throughout treatments. Fecal sample collection was completed days 6⁻10, and samples were assessed for bacterial composition, SCFA concentrations, weight, pH, and consistency. There were no differences in breath hydrogen, stool frequency, consistency, fecal pH, or SCFA concentrations between the two diets. The mushroom diet led to greater overall gastrointestinal symptoms than the meat diet on days one and two. The mushroom-rich diet resulted in higher average stool weight (p = 0.002) and a different fecal microbiota composition compared to the meat diet, with greater abundance of Bacteroidetes (p = 0.0002) and lower abundance of Firmicutes (p = 0.0009). The increase in stool weight and presence of undigested mushrooms in stool suggests that mushroom consumption may impact laxation in healthy adults. Additional research is needed to interpret the health implications of fecal microbiota shifts with mushroom feeding.

Positive effects of resistant starch supplementation on bowel function in healthy adults: a systematic review and meta-analysis of randomized controlled trials

Animal experimental studies have found that resistant starch can significantly improve bowel function, but the outcomes are mixed while conducting human studies. Thus, we conducted a systematic review and meta-analysis of randomized controlled trials to evaluate the relationship between resistant starch supplementation and large intestinal function. Three electronic databases (PubMed, Embase, Scopus) were searched to identify eligible studies. The standardized mean difference (SMD) or weighted mean difference (WMD) was calculated using a fixed-effects model or a random-effects model. The pooled findings revealed that resistant starch significantly increased fecal wet weight (WMD 35.51 g/d, 95% CI 1.21, 69.82) and butyrate concentration (SMD 0.61, 95% CI 0.32, 0.89). Also, it significantly reduced fecal PH (WMD -0.19, 95% CI -0.35, -0.03), but the increment of defecation frequency were not statistically significant (WMD 0.04stools/g, 95% CI -0.08, 0.16). To conclude, our study found that resistant starch elicited a beneficial effect on the function of large bowel in healthy adults.[Formula: see text].

Resistant starch for modulation of gut microbiota: Promising adjuvant therapy for chronic kidney disease patients?

The gut microbiota has been extensively studied in all health science fields because its imbalance is linked to many disorders, such as inflammation and oxidative stress, thereby contributing to cardiovascular disease, obesity, diabetes and chronic kidney disease (CKD) complications. Novel therapeutic strategies that aim to reduce the complications caused by this imbalance have increased in recent years. Studies have shown that prebiotic supplementation can beneficially modulate the gut microbiota in CKD patients. Prebiotics consist of non-digestible dietary soluble fiber, which acts as a substrate for the gut microbiota. Resistant starch (RS) is a type of dietary fiber that can reach the large bowel and act as a substrate for microbial fermentation; for these reasons, it has been considered to be a prebiotic. Few studies have analyzed the effects of RS on the gut microbiota in CKD patients. This review discusses recent information about RS and the potential role of the gut microbiota, with a particular emphasis on CKD patients.

Resistant starch alters colonic contractility and expression of related genes in rats fed a Western diet

BACKGROUND AND AIM

Dietary fiber shortens gut transit time, but data on the effects of fiber components (including resistant starch, RS) on intestinal contractility are limited. We have examined RS effects in male Sprague-Dawley rats fed either a high-amylose maize starch (HAMS) or a wholemeal made from high-amylose wheat (HAW) on ileal and colonic contractility ex vivo and expression of genes associated with smooth muscle contractility.

METHODS

Rats were fed diets containing 19 % fat, 20 % protein, and either low-amylose maize starch (LAMS), HAMS, wholemeal low-amylose wheat (LAW) or HAW for 11 week. Isolated ileal and proximal colonic sections were induced to contract electrically, or by receptor-independent (KCl) or receptor-dependent agents. Colonic gene expression was assessed using an Affymetrix microarray.

RESULTS

Ileal contractility was unaffected by treatment. Maximal proximal colonic contractility induced electrically or by angiotensin II or carbachol was lower for rats fed HAMS and LAW relative to those fed LAMS (P < 0.05). The colonic expression of genes, including cholinergic receptors (Chrm2, Chrm3), serotonin receptors (Htr5a, Htr7), a protease-activated receptor (F2r), a prokineticin receptor (Prokr1), prokineticin (Prok1), and nitric oxide synthase 2 (Nos2), was altered by dietary HAMS relative to LAMS (P < 0.05). HAW did not significantly affect these genes or colonic contractility relative to effects of LAMS.

CONCLUSIONS

RS and other fiber components could influence colorectal health through modulation of stool transit time via effects on muscular contractility.

Health benefits of prebiotic fibers

This chapter describes the various compounds that can act as prebiotic fibers: their structure, occurrence, production, and physiological effects (health effects) will be presented. The basis for the description is the latest definitions for dietary fibers and for prebiotics. Using as much as possible data from human studies, both the fiber and the prebiotic properties will be described of a variety of compounds. Based on the presented data the latest developments in the area of prebiotics, fibers and gut and immune health will be discussed in more detail as they show best what the potential impact of prebiotics on health of the human host might be.

Health properties of oca (Oxalis tuberosa) and yacon (Smallanthus sonchifolius)

Andean roots and tubers are underexploited crops; many contain compounds beneficial to health, so a greater knowledge of their properties is important for encouraging their consumption.

Tolerance and the effect of high doses of wheat bran extract, containing arabinoxylan-oligosaccharides, and oligofructose on faecal output: a double-blind, randomised, placebo-controlled, cross-over trial

Wheat bran extract (WBE) is a food-grade soluble fibre preparation that is highly enriched in arabinoxylan-oligosaccharides. In this placebo-controlled cross-over human intervention trial, tolerance to WBE as well as the effects of WBE on faecal parameters, including faecal output and bowel habits, were studied. After a 2-week run-in period, twenty healthy volunteers consumed WBE (15 g/d in the first week, 30 g/d in the second week), oligofructose (15 g/d in the first week, 30 g/d in the second week) and placebo (for 2 weeks) in a random order, with 2-week washout periods between each treatment period. Subjects collected a 72 h stool sample for analysis of faecal output, stool pH and stool moisture concentration. Additionally, the volunteers completed questionnaires scoring occurrence frequency and distress severity of eighteen gastrointestinal (GI) symptoms. An overall GI symptom measure was calculated to analyse the overall effect of WBE and oligofructose on GI symptoms. Intake of both 30 g/d WBE and 30 g/d oligofructose lowered stool pH, indicative of increased colonic fermentation, and increased stool moisture concentration as compared with placebo intake. Intake of 30 g/d oligofructose increased the overall GI symptom measure by 1·9-fold as compared with placebo intake. Intake of WBE at doses up to 30 g/d did not affect the overall GI symptom measure. WBE exerts beneficial effects on stool characteristics and is well tolerated at up to 30 g/d. Oligofructose exerts comparable beneficial effects on stool characteristics. However, intake of 30 g/d oligofructose appears to cause GI discomfort to some extent.

Gastrointestinal effects of resistant starch, soluble maize fibre and pullulan in healthy adults

Fibre has been shown to exert a number of benefits on gastrointestinal (GI) health, yet its intake is low. Addition of novel fibres to food products may increase fibre intake and improve gut health. The objective of the present study was to evaluate the influence of three novel fibres on GI outcomes in healthy human subjects. A total of twenty healthy participants (ten men and ten women) with normal BMI (23 (sem 2) kg/m2) participated in the present randomised, double-blind, cross-over study with five treatment periods. Participants consumed a maltodextrin control or 20–25 g/d fibre from soluble maize fibre (SCF) or resistant starch (RS), alone or in combination with pullulan (SCF+P and RS+P). The treatment periods were 7 d with a 3-week washout between the periods. Stool samples were collected on day 7 of each period, and GI tolerance was assessed via a questionnaire on days 1 and 6. There were no treatment differences in stool weight or consistency. SCF significantly reduced stool pH and increased total SCFA production compared with RS and control. RS+P significantly increased the percentage of butyrate compared with all the other treatments. Overall, GI symptoms were minimal. SCF+P led to the highest GI score on day 1, while RS+P had the highest score on day 6. Both SCF treatments caused a significant shift in the gut microbial community. These functional fibres are generally well tolerated, have minimal effects on laxation and may lead to beneficial changes in SCFA production in healthy adults.

Consumption of breads containing in situ-produced arabinoxylan oligosaccharides alters gastrointestinal effects in healthy volunteers

Arabinoxylan oligosaccharides (AXOS) are studied as food compounds with prebiotic potential. Here, the impact of consumption of breads with in situ-produced AXOS on intestinal fermentation and overall gastrointestinal characteristics was evaluated in a completely randomized, double-blind, controlled, cross-over study. Twenty-seven healthy volunteers consumed 180 g of wheat/rye bread with or without in situ-produced AXOS (WR(+) and WR(-), respectively) daily for 3 wk. Consumption of WR(+) corresponded to an AXOS intake of ~2.14 g/d. Refined wheat flour bread without AXOS (W(-)) (180 g/d) was provided during the 3-wk run-in and wash-out periods. At the end of each treatment period, participants collected urine for 48 h as well as a feces sample. Additionally, all participants completed a questionnaire about stool characteristics and gastrointestinal symptoms during the last week of each period. Urinary phenol and p-cresol excretions were significantly lower after WR(+) intake compared to WR(-). Consumption of WR(+) significantly increased fecal total SCFA concentrations compared to intake of W(-). The effect of WR(+) intake was most pronounced on butyrate, with levels 70% higher than after consumption of W(-) in the run-in or wash-out period. Consumption of WR(+) tended to selectively increase the fecal levels of bifidobacteria (P = 0.06) relative to consumption of W(-). Stool frequency increased significantly after intake of WR(+) compared to WR(-). In conclusion, consumption of breads with in situ-produced AXOS may favorably modulate intestinal fermentation and overall gastrointestinal properties in healthy humans.