Inclusion Of Resistant Starch Research Articles

Resistant starch: A promising ingredient and health promoter

Resistant starch (RS) consists of a glucose plant polymer that is extremely abundant in nature and easily obtained through simple technological processes in the food industry. Its molecular conformation, as well as its specific localization within the plant tissues, makes this molecule sterically inaccessible to the activity of amylolytic enzymes, which can degrade any other type of starch. Such a characteristic allows resistant starch to act as dietary fiber when ingested by humans, and it is used as a substrate by the gut microbiota. By metabolizing the resistant starch, the microbiota can produce organic fatty acids of low molecular weight, mainly butyrate, propionate, and acetate, also known as short-chain fatty acids (SCFA). Besides being a valuable energy source for colonocytes, SCFA promotes a plethora of beneficial and systemic effects on human metabolism. Researchers worldwide have been investigating the broad spectrum of benefits generated by the inclusion of resistant starch in the diet, including its effect on counteracting metabolic diseases. The worldwide abundance, easy access, and variety of industrial applications of resistant starch make it a functional food of great interest to the scientific community and for the development of new dietetic approaches capable of promoting health for the world’s population. This review will cover physiological aspects associated with RS intake and its impact on microbiota and health, especially to counteract chronic non-communicable diseases.

Nondigestible Carbohydrates Affect Metabolic Health and Gut Microbiota in Overweight Adults after Weight Loss

The composition of diets consumed following weight loss (WL) can have a significant impact on satiety and metabolic health. This study was designed to test the effects of including a nondigestible carbohydrate to achieve weight maintenance (WM) following a period of WL. Nineteen volunteers [11 females and 8 males, aged 20-62 y; BMI (kg/m2): 27-42] consumed a 3-d maintenance diet (15%:30%:55%), followed by a 21-d WL diet (WL; 30%:30%:40%), followed by 2 randomized 10-d WM diets (20%:30%:50% of energy from protein:fat:carbohydrate) containing either resistant starch type 3 (RS-WM; 22 or 26g/d for females and males, respectively) or no RS (C-WM) in a within-subject crossover design without washout periods. The primary outcome, WM after WL, was analyzed by body weight. Secondary outcomes of fecal microbiota composition and microbial metabolite concentrations and gut hormones were analyzed in fecal samples and blood plasma, respectively. All outcomes were assessed at the end of each dietary period. Body weight was similar after the RS-WM and C-WM diets (90.7 and 90.8kg, respectively), with no difference in subjectively rated appetite. During the WL diet period plasma ghrelin increased by 36% (P<0.001), glucose-dependent insulinotropic polypeptide (GIP) decreased by 33% (P<0.001), and insulin decreased by 46% (P<0.001), but no significant differences were observed during the RS-WM and C-WM diet periods. Fasting blood glucose was lower after the RS-WM diet (5.59±0.31mmol/L) than after the C-WM diet [5.75±0.49mmol/L; P=0.015; standard error of the difference between the means (SED): 0.09]. Dietary treatments influenced the fecal microbiota composition (R2=0.054, P=0.031) but not diversity. The metabolic benefits, for overweight adults, from WL were maintained through a subsequent WM diet with higher total carbohydrate intake. Inclusion of resistant starch in the WM diet altered gut microbiota composition positively and resulted in lower fasting glucose compared with the control, with no apparent change in appetite. This trial was registered at clinicaltrials.gov as NCT01724411.

Structural Basis of Resistant Starch (RS) in Bread: Natural and Commercial Alternatives.

Bread is categorized as having a high amount of rapidly digested starch that may result in a rapid increase in postprandial blood glucose and, therefore, poor health outcomes. This is mostly the result of the complete gelatinization that starch undergoes during baking. The inclusion of resistant starch (RS) ingredients in bread formulas is gaining prominence, especially with the current positive health outcomes attributed to RS and the apparition of novel RS ingredients in the market. However, many RS ingredients contain RS structures that do not resist baking and, therefore, are not suitable to result in a meaningful RS increase in the final product. In this review, the structural factors for the resistance to digestion and hydrothermal processing of RS ingredients are reviewed, and the definition of each RS subtype is expanded to account for novel non-digestible structures recently reported. Moreover, the current in vitro digestion methods used to measure RS content are critically discussed with a view of highlighting the importance of having a harmonized method to determine the optimum RS type and inclusion levels for bread-making.

Reformulating cereal bars: high resistant starch reduces in vitro digestibility but not in vivo glucose or insulin response; whey protein reduces glucose but disproportionately increases insulin

Resistant starch (RS) and whey protein are thought to be effective nutrients for reducing glycemic responses. We aimed to determine the effect of varying the sucrose, RS, and whey protein content of cereal bars on glucose and insulin responses. Twelve healthy subjects [mean ± SD age: 36 ± 12 y; mean ± SD body mass index (in kg/m2): 24.9 ± 2.7] consumed 40 g available-carbohydrate (avCHO) portions of 5 whole-grain cereal bars that contained varying amounts of RS and whey protein concentrate [WPC; 70% protein; RS:WPC, %wt:wt: 15:0 (Bar15/0); 15:0, low in sucrose (Bar15/0LS); 15:5 (Bar15/5); 10:5 (Bar10/5); and 10:10 (Bar10/10)] and 2 portion sizes of a control bar low in whole grains, protein, and RS [control 1 contained 40 g avCHO (Control1); control 2 contained total carbohydrate equal to Bar15/0LS (Control2)] on separate days by using a randomized crossover design. Glucose and insulin responses in vivo and carbohydrate digestibility in vitro were measured over 3 h. Incremental area under the curve (iAUC) over 0-3 h for glucose (min × mmol/L) differed significantly between treatments (P < 0.001) [Bar15/0LS (mean ± SEM), 169 ± 14; Control2, 164 ± 20; Bar15/0, 144 ± 15; Control1, 140 ± 17; Bar10/5, 117 ± 12; Bar15/5, 116 ± 9; and Bar10/10, 100 ± 9; Tukey's least significant difference = 42, P < 0.05], but insulin iAUC did not differ significantly. Higher protein content was associated with a lower glucose iAUC (P = 0.028) and a higher insulin-to-glucose iAUC ratio (P = 0.002) All 5 RS-containing bars were digested in vitro ∼30% more slowly than the control bars (P < 0.05); however, in vivo responses were not related to digestibility in vitro. Glucose and insulin responses elicited by high-RS, whey protein-free bars were similar to those elicited from control bars. The inclusion of RS in cereal bar formulations did not reduce glycemic responses despite slower starch digestion in vitro. Thus, caution is required when extrapolating in vitro starch digestibility to in vivo glycemic response. The inclusion of whey protein in cereal bar formulations to reduce glycemic response requires caution because this may be associated with a disproportionate increase in insulin as judged by an increased insulin-to-glucose iAUC ratio. This trial was registered at clinicaltrials.gov as NCT02537587.

Effect of Resistant Starch and Inulin on the Properties of Imitation Mozzarella Cheese

The effect of two fat replacers (inulin and resistant starch) on functional properties and microstructure of imitation Mozzarella cheeses was evaluated. Three groups of imitation Mozzarella cheeses were manufactured by adding 0, 2.4, 4.8, 7.2, 9.6, and 12% (w/w) inulin or resistant starch instead of the fat, respectively. Inclusion of the inulin up to 7.2% in cheese, fat content of it was significantly (p ≤ 0.05) decreased and the moisture and pH values of it were significantly (p ≤ 0.05) different. Inclusion of resistant starch up to 9.6% in cheese, fat content of it was significantly (p ≤ 0.01) decreased and the moisture and pH values of it were significantly (p ≤ 0.05) different. The physical properties of these cheeses were significantly different (p ≤ 0.05) among them. The textural properties were determined by instrumental texture profile. With increased levels of inulin or resistant starch from 2.4 to 12% (w/w), the hardness of the resultant imitation cheeses were significantly increased (p ≤ 0.05), while the cohesiveness and springiness decreased and the meltability and stretch ability had reduced (p ≤ 0.05), compared with the control, especially containing resistant starch stretch ability had reduced more. The microstructure of imitation Mozzarella cheese was observed by scanning electron microscopy. The scanning electron microscopy results indicated that interactions between casein and inulin or resistant starch in imitation cheeses accounted for variance properties of imitation cheese. It is concluded that inulin or resistant starch could be used to replace up to 7.2% of the fat in imitation cheese and that the preferred substitution was inulin.

Effects of alginate and resistant starch on feeding patterns, behaviour and performance in ad libitum-fed growing pigs

This study assessed the long-term effects of feeding diets containing either a gelling fibre (alginate (ALG)), or a fermentable fibre (resistant starch (RS)), or both, on feeding patterns, behaviour and growth performance of growing pigs fed ad libitum for 12 weeks. The experiment was set up as a 2×2 factorial arrangement: inclusion of ALG (yes or no) and inclusion of RS (yes or no) in the control diet, resulting in four dietary treatments, that is, ALG−RS− (control), ALG+RS−, ALG−RS+, and ALG+RS+. Both ALG and RS were exchanged for pregelatinized potato starch. A total of 240 pigs in 40 pens were used. From all visits to an electronic feeding station, feed intake and detailed feeding patterns were calculated. Apparent total tract digestibility of energy, dry matter (DM), and CP was determined in week 6. Pigs’ postures and behaviours were scored from live observations in weeks 7 and 12. Dietary treatments did not affect final BW and average daily gain (ADG). ALG reduced energy and DM digestibility (P<0.01). Moreover, ALG increased average daily DM intake, and reduced backfat thickness and carcass gain : digestible energy (DE) intake (P<0.05). RS increased feed intake per meal, meal duration (P<0.05) and inter-meal intervals (P=0.05), and reduced the number of meals per day (P<0.01), but did not affect daily DM intake. Moreover, RS reduced energy, DM and CP digestibility (P<0.01). Average daily DE intake was reduced (P<0.05), and gain : DE intake tended to be increased (P=0.07), whereas carcass gain : DE intake was not affected by RS. In week 12, ALG+RS− increased standing and walking, aggressive, feeder-directed, and drinking behaviours compared with ALG+RS+ (ALG×RS interaction, P<0.05), with ALG−RS− and ALG−RS+ in between. No other ALG×RS interactions were found. In conclusion, pigs fed ALG compensated for the reduced dietary DE content by increasing their feed intake, achieving similar DE intake and ADG as control pigs. Backfat thickness and carcass efficiency were reduced in pigs fed ALG, which also showed increased physical activity. Pigs fed RS changed feeding patterns, but did not increase their feed intake. Despite a lower DE intake, pigs fed RS achieved similar ADG as control pigs by increasing efficiency in DE use. This indicates that the energy utilization of RS in pigs with ad libitum access to feed is close to that of enzymatically digestible starch.

Impact of fibers on physical characteristics of fresh and staled bake off bread

The technological functionality of different fibers (high methylated ester pectin, resistant starch, insoluble-soluble fiber blend) was tested in partially baked breads stored either under sub-zero or low temperatures, in order to assess their possible role as breadmaking ingredients in bake off technologies (BOT). Fiber-containing formulations affected bread specific volume and crumb hardness, and those characteristics were also dependent on both the breadmaking process (conventional or BOT) and the storage conditions of the par-baked bread (low or sub-zero temperatures). The inclusion of resistant starch (RS) and fiber blend in the bread formulation induced a reduction in the specific volume of the bread and an increase of hardness. Crumb image analysis indicated that breadmaking process affected significantly the number of alveoli. The storage of par-baked breads at low temperatures accelerates crumb hardening during staling, and that effect was greatly dependent on the duration of the storage, being that effect magnified in the case of breads containing fiber blend. Therefore, formulations should be carefully checked with the specific breadmaking process to be followed. Special attention should be paid to the storage conditions of the partially baked bread, since they significantly affect the technological quality of fresh breads and their behaviour during staling.

Dietary Resistant Starch Increases Hypothalamic POMC Expression in Rats

Resistant starch (RS) is fermentable dietary fiber. Inclusion of RS in the diet causes decreased body fat accumulation and altered gut hormone profile. This study investigates the effect of feeding RS on the neuropeptide messenger RNA (mRNA) expressions in the arcuate nucleus (ARC) of the hypothalamus and whether vagal afferent nerves are involved. The rats were injected intraperitoneally with capsaicin to destroy unmyelinated small vagal afferent nerve fibers. The cholecystokinin (CCK) food suppression test was performed to validate the effectiveness of the capsaicin treatment. Then, capsaicin-treated rats and vehicle-treated rats were subdivided into a control diet or a RS diet group, and fed the corresponding diet for 65 days. At the end of study, body fat, food intake, plasma peptide YY (PYY) and glucagon-like peptide 1 (GLP-1), and hypothalamic pro-opiomelanocortin (POMC), neuropeptide Y (NPY), agouti-related peptide (AgRP) gene expressions were measured. RS-fed rats had decreased body fat, increased POMC expression in the hypothalamic ARC, and elevated plasma PYY and GLP-1 in both the capsaicin and vehicle-treated rats. Hypothalamic NPY and AgRP gene expressions were not changed by RS or capsaicin. Therefore, destruction of the capsaicin-sensitive afferent nerves did not alter the response to RS in rats. These findings suggest that dietary RS might reduce body fat through increasing the hypothalamic POMC expression and vagal afferent nerves are not involved in this process. This is the first study to show that dietary RS can alter hypothalamic POMC expression.

Resistant starch prevents colonic DNA damage induced by high dietary cooked red meat or casein in rats

In previous studies we have shown that high levels of dietary protein (as casein) result in increased levels of colonic DNA damage, measured by the comet assay, and thinning of the colonic mucus layer in rats when dietary resistant starch (RS) is negligible. Feeding RS abolishes these effects. This study aimed to establish whether a diet high in protein as cooked red meat would have similar effects and whether RS was protective. Rats were fed a diet containing 15% or 25% casein, or 25% cooked lean red beef, each with or without the addition of 48% high amylose maize starch (a rich source of RS) for 4 weeks. As expected, high dietary casein caused a 2-fold increase in colonic DNA damage compared with a low casein diet and reduced the thickness of the colonic mucus layer by 41%. High levels of cooked meat caused 26% greater DNA damage than the high casein diet but reduced mucus thickness to a similar degree to casein. Addition of RS to the diet abolished the increase in DNA damage and the loss of colonic mucus thickness induced by either high protein diet. Caecal and faecal short chain fatty acid pools were also increased by inclusion of RS in the diet. Because DNA damage is an early step in the initiation of cancer, these findings suggest that increased DNA damage due to high dietary protein as cooked red meat or casein could increase colorectal cancer risk but inclusion of resistant starch in the diet could significantly reduce that risk.