Quantitative management of human faecal bulking response to combinations of functionally distinct dietary fibers, using functional equivalents and a validated rat model

Functionally distinct dietary fibre sources may be combined in reformulated foods to restore a natural spectrum of health attributes. Effects of wheat bran (WB), psyllium husk, guar gum and Raftilose™ combinations on hydrated faecal mass (HFM), were determined. A valid rat model was fed diets supplemented with 10% WB, 10% WB with 1-6% psyllium in 1% steps, and 10% WB/5% psyllium with 1-7% guar gum or 1-6% Raftilose in 1% steps. Fully hydrated faecal pellets gave HFM values in the human range, increasing by 2.4 ± 0.29 g per gram of WB ingested, and by 15.6 ± 1.52 g per g of psyllium. Equations for incremental changes in HFM predicted intakes of fibre combinations required for adequate daily HFM, and it is shown how expressing relative effects of foods on HFM as functional equivalents would allow quantitative personalised management of HFM for reduced constipation and colorectal cancer in humans.

A Short-Term Low-Fiber Diet Reduces Body Mass in Healthy Young Men: Implications for Weight-Sensitive Sports

Athletes from weight-sensitive sports are reported to consume low-fiber diets (LOW) to induce acute reductions in body mass (BM). However, evidence supporting their efficacy is anecdotal. Therefore, we aimed to determine the effect of a LOW on acute changes in BM. Nineteen healthy males (32 ± 10 years, 1.79 ± 0.07 m, 77.5 ± 8.1 kg) consumed their habitual diet (∼30 g fiber/day) for 7 consecutive days followed by 4 days of a LOW (<10 g fiber/day) that was matched for energy and macronutrient content. Participants also matched their daily exercise load during LOW to that completed during habitual diet (p = .669, average 257 ± 141 arbitrary units). BM was significantly reduced in LOW versus habitual diet after 4 days (Δ = 0.40 ± 0.77 kg or 0.49% ± 0.91%, p < .05, effect size [ES] [95% confidence interval] = -0.53 [-1.17, 0.12]) and on the morning of Day 5 (Δ = 0.58 ± 0.83 kg or 0.74% ± 0.99%, p < .01, ES = -0.69 [-1.34, -0.03]). LOW resulted in moderately higher hunger (Δ = 5 ± 9 mm, p = .015, ES = 0.55 [-0.09, 1.20]), a decline in stool frequency from 2 ± 0 to 1 ± 0 bowel movements per day (p = .012, ES = 0.64 [-0.02, 1.29]) and stool softness decrease (p = .005). Nonetheless, participants reported the diet to be tolerable (n = 18/19) and were willing to repeat it (n = 16/19). Data demonstrate for the first time that consumption of a short-term LOW induces reductions in BM.

Low-Molecular-Weight Seaweed-Derived Polysaccharides Lead to Increased Faecal Bulk but Do Not Alter Human Gut Health Markers

Seaweeds are potentially sustainable crops and are receiving significant interest because of their rich bioactive compound content; including fatty acids, polyphenols, carotenoids, and complex polysaccharides. However, there is little information on the in vivo effects on gut health of the polysaccharides and their low-molecular-weight derivatives. Herein, we describe the first investigation into the prebiotic potential of low-molecular-weight polysaccharides (LMWPs) derived from alginate and agar in order to validate their in vivo efficacy. We conducted a randomized; placebo-controlled trial testing the impact of alginate and agar LWMPs on faecal weight and other markers of gut health and on composition of gut microbiota. We show that these LMWPs led to significantly increased faecal bulk (20–30%). Analysis of gut microbiome composition by sequencing indicated no significant changes attributable to treatment at the phylum and family level, although FISH analysis showed an increase in Faecalibacterium prausnitzii in subjects consuming agar LMWP. Sequence analysis of gut bacteria corroborated with the FISH data, indicating that alginate and agar LWMPs do not alter human gut microbiome health markers. Crucially, our findings suggest an urgent need for robust and rigorous human in vivo testing—in particular, using refined seaweed extracts.

Peak week recommendations for bodybuilders: an evidence based approach

Bodybuilding is a competitive endeavor where a combination of muscle size, symmetry, "conditioning" (low body fat levels), and stage presentation are judged. Success in bodybuilding requires that competitors achieve their peak physique during the day of competition. To this end, competitors have been reported to employ various peaking interventions during the final days leading to competition. Commonly reported peaking strategies include altering exercise and nutritional regimens, including manipulation of macronutrient, water, and electrolyte intake, as well as consumption of various dietary supplements. The primary goals for these interventions are to maximize muscle glycogen content, minimize subcutaneous water, and reduce the risk abdominal bloating to bring about a more aesthetically pleasing physique. Unfortunately, there is a dearth of evidence to support the commonly reported practices employed by bodybuilders during peak week. Hence, the purpose of this article is to critically review the current literature as to the scientific support for pre-contest peaking protocols most commonly employed by bodybuilders and provide evidence-based recommendations as safe and effective strategies on the topic.

Kiwifruit Skin and Flesh Contributions to Fecal Bulking and Bacterial Abundance in Rats

Changes in fecal bulk and bacterial abundance due to separately consumed skin and flesh of four kiwifruit cultivars was determined using a rat model designed to estimate the fecal bulking potential of human foods. Dry matter contribution by skin to 100 g of fresh kiwifruit was less than 5% in all cultivars, whereas flesh dry matter contributed up to 20% of fresh fruit weight. Dietary fiber was 35-49% of skin compared with 8-23% of flesh on a dry weight basis. The skin significantly increased whole fruit fecal bulking, but the total bulk per 100 g kiwifruit was less than 10% of daily fecal bulk recommended for optimal gut health. Kiwifruit (skin or flesh) substantially increased the abundance of Lachnospiraceae and Lactobacillus spp. within the gut. Fermentation and prebiosis therefore probably play a greater role than fermentation-resistant dietary fiber in gut health benefits of kiwifruit.

Modifying wheat bran to improve its health benefits

Consumption of wheat bran (WB) has been associated with improved gastrointestinal health and a reduced risk for colorectal cancer, cardiovascular diseases and metabolic disorders. These benefits are likely mediated by a combination of mechanisms, including colonic fermentation of the WB fiber, fecal bulking and the prevention of oxidative damage due to its antioxidant capacities. The relative importance of those mechanisms is not known and may differ for each health effect. WB has been modified by reducing particle size, heat treatment or modifying tissue composition to improve its technological properties and facilitate bread making processes. However, the impact of those modifications on human health has not been fully elucidated. Some modifications reinforce whereas others attenuate the health effects of coarse WB. This review summarizes available WB modifications, the mechanisms by which WB induces health benefits, the impact of WB modifications thereon and the available evidence for these effects from in vitro and in vivo studies.

The Effect of Water Loading on Acute Weight Loss Following Fluid Restriction in Combat Sports Athletes

Novel methods of acute weight loss practiced by combat sport athletes include “water loading,” the consumption of large fluid volumes for several days prior to restriction. We examined claims that this technique increases total body water losses, while also assessing the risk of hyponatremia. Male athletes were separated into control (n = 10) and water loading (n = 11) groups and fed a standardized energy-matched diet for 6 days. Days 1–3 fluid intake was 40 and 100 ml/kg for control and water loading groups, respectively, with both groups consuming 15 ml/kg on Day 4 and following the same rehydration protocol on Days 5 and 6. We tracked body mass (BM), urine sodium, urine specific gravity and volume, training-related sweat losses and blood concentrations of renal hormones, and urea and electrolytes throughout. Physical performance was assessed preintervention and postintervention. Following fluid restriction, there were substantial differences between groups in the ratio of fluid input/output (39%, p < .01, effect size = 1.2) and BM loss (0.6% BM, p = .02, effect size = 0.82). Changes in urine specific gravity, urea and electrolytes, and renal hormones occurred over time (p < .05), with an interaction of time and intervention on blood sodium, potassium, chloride, urea, creatinine, urine specific gravity, and vasopressin (p < .05). Measurements of urea and electrolyte remained within reference ranges, and no differences in physical performance were detected over time or between groups. Water loading appears to be a safe and effective method of acute BM loss under the conditions of this study. Vasopressin-regulated changes in aquaporin channels may potentially partially explain the mechanism of increased body water loss with water loading.

Vegetable dietary fibres made with minimal processing improve health-related faecal parameters in a valid rat model

Structural components in tissues of minimally processed vegetables substantially increase faecal bulk and hydration capacity much more than fermentable fibres.

Fiber: composition, structures, and functional properties

Kiwifruit dietary fiber consists of cell-wall polysaccharides that are typical of the cell walls of many dicotyledonous fruits, being composed of pectic polysaccharides, hemicelluloses, and cellulose. The kiwifruit pectic polysaccharides consist of homo- and rhamnogalacturonans with various neutral, (arabino)-galactan side chains, while the hemicelluloses are mostly xyloglucan and xylan. The proportions of pectic polysaccharide, hemicellulose, and cellulose in both green 'Hayward' and 'Zespri® Gold' are similar and are little affected by in vitro exposure to gastric and small intestinal digestion. The hydration properties of the kiwifruit-swelling and water retention capacity-are also unaffected by foregut digestion, indicating that the functional properties of kiwifruit fiber survive in the foregut. However, in the hindgut, kiwifruit fiber is fermented, but whole kiwifruit consumed in association with slowly fermented fiber leads to distal displacement of fermentation, indicating that hindgut benefits of kiwifruit may result from its interaction with other dietary sources of fiber.

Virtual food components: functional food effects expressed as food components

BACKGROUND

The ability to communicate food benefits is essential for the successful development of functional foods and their role in improving public health. However, the functional efficacy of foods often cannot be represented by food composition. The concept of virtual food components (VFCs)-food data that express health-related effects, properties or functions of foods in the format of food components-is therefore proposed.

OBJECTIVE

To develop protocols for designing VFC data sets that communicate functional efficacies of foods to end users, in order to facilitate evidence-based food choice, and allow data management systems to provide a more complete description of nutritional effects of foods than has been possible with values for actual food components alone.

METHOD

A framework within which to develop VFCs was constructed, linking food choice to health end points. It involves scientific validation, generation of relative indices, their translation into a meaningful language based on equivalents to known and understood reference foods, followed by data consolidation and ecological validation. Criteria used to evaluate VFCs were importance, independence, validity, accuracy, robustness, sensitivity, linearity/additivity, relevance, comprehensiveness, acquirability, completeness, meaningfulness, acceptability and safety. The developmental framework and evaluative criteria were applied to glycaemic glucose equivalents (GGE), a VFC representing postprandial glycaemia, and to wheat bran equivalents for faecal bulk (WBE(fb)), a VFC representing faecal bulking efficacy.

RESULTS

VFCs were used to identify foods according to health-related effects that cannot be accurately predicted from food composition data, and were used in a nutrition management system to concurrently show nutrient intake and physiological effects in the same units. The proposed evaluative criteria identified points requiring further research, and showed that lack of integrity-tested VFC data is an immediate challenge.

CONCLUSION

VFCs are a means of communicating relative functional efficacy of foods as a continuous variable, and provide end users with a more accurate and complete view of the health effects of foods than can be provided by health claims or food composition data alone.

Adequate intake values for dietary fibre based on faecal bulking indexes of 66 foods

OBJECTIVE

To determine an adequate daily intake value for dietary fibre (AIdf) based on faecal bulking indexes (FBIs) for 66 foods of known total dietary fibre (TDF) content.

DESIGN

FBIs of 66 foods were measured and expressed as wheat bran equivalents (WBEfb) per 100 g of food. A daily WBEfb requirement for humans was calculated from faecal bulk generated per gram of wheat bran TDF in humans, using a critical faecal mass of 200 g/day for protection against large bowel disease. TDF content was regressed against WBEfb content for all 66 foods assayed, and an AIdf value obtained by substituting the calculated human WBEfb requirement into the regression equation.

METHOD

FBI was measured using a validated rat assay, with eight large (400+/-50 g) rats per group, preadapted to dietary fibre, and fed adequate restricted diets containing test foods at inclusion rates consistent with human intakes. The critical faecal mass was based on epidemiological studies, and the faecal bulk generated per gram of wheat bran TDF was the mean of 27 published values.

RESULTS

WBEfb requirements for humans were calculated to be 90 g/day, corresponding to a faecal output of 200 g/day. The regression equation relating WBEfb measured in the FBI assay to TDF in all 66 foods was TDF=0.491WBEfb + 3.19, R2=0.81 Substituting the human WBEfb requirement of 90 g into the regression equation gave an AIdf value of 40.9 g TDF/day.

CONCLUSION

The AIdf value of 40.9 g TDF/day based on faecal bulking supports the AIdf of 38 g TDF/day recently set by the Institute of Medicine (USA), for young men, based on protection against heart disease. The AIdf value is obtained from the relation between the effects of foods and their content of mixed function, plant cell wall dietary fibres within the food matrices, and should not be used to guide intakes of extrinsic functional polysaccharides.

Dietary fibre content and nutrient claims relative to the faecal bulking efficacy of breakfast cereals

The correspondence between the dietary fibre contents of 28 breakfast cereals and their faecal bulking efficacies was measured and used to assess criterion values controlling nutrient claims for dietary fibre. A valid, standardised rat assay was used to measure faecal bulking efficacy as the content of wheat bran equivalents for faecal bulk (WBEfb) in the cereals. Regression analysis of WBEfb content against dietary fibre content allowed the adequacy of criterion fibre values for claims of 'source of fibre,' 'high in fibre' and 'very high in fibre' to be assessed relative to a daily reference requirement of 63 WBEfb, based on human data. Faecal bulking by breakfast cereals was much lower than implied by the dietary fibre claims associated with them. Many more were claimed to be 'high' or 'very high' in dietary fibre (n = 13) than were 'high' or 'very high' in faecal bulking efficacy (n = 4). Conversely, dietary fibre requirements per serving predicted from WBEfb requirements, as necessary to maintain adequate faecal bulk in the current Australian diet, were much higher (4.4 g) than the criterion fibre content (1.5 g) for the most modest claim, 'source of fibre'. After removing four high-bran cereals (>15% dietary fibre) from the analysis, a modest correlation of r = 0.62 between dietary fibre content and faecal bulk was obtained. It is concluded that, with respect to breakfast cereals, fibre values specified for nutrient claims are too low, dietary fibre content is not a reliable guide to faecal bulking efficacy and direct measures of faecal bulking capacity would be more useful than dietary fibre content in describing faecal bulking efficacy for evidence-based food choice.

Faecal bulking efficacy of Australasian breakfast cereals

Faecal bulk may play an important role in preventing a range of disorders of the large bowel, but as yet there is little information available on the relative faecal bulking capacities of various foods. Breakfast cereals are often promoted as a good source of potential bulk for 'inner health' because they provide dietary fibre, but their relative abilities to provide faecal bulk per se have not been described. The faecal bulking efficacy of 28 representative Australasian breakfast cereals was therefore measured. A rat model developed for the purpose, and shown to give similar responses as humans to cereal fibres, was used to measure faecal bulking efficacy as increases in fully hydrated faecal weight/100 g diet, based on precise measurements of food intake, faecal dry matter output and faecal water-holding capacity (g water held without stress/g faecal dry matter). Compared to a baseline diet containing 50% sucrose, increments in hydrated faecal weight due to 50% breakfast cereal ranged from slightly negative (Cornflakes, -2 g/100 g diet) to about 80 g/100 g diet (San Bran). Most breakfast cereals increased hydrated faecal weight by between 10 and 20 g/100 g diet from a baseline of 21 +/- 1.5 g/100 g diet, but four products containing high levels of wheat bran had an exceptionally large impact on hydrated faecal weight (increment > 20 g/100 g diet), and the changes resulted more from relative changes in dry matter output than in faecal water retention/gram. However, as faecal water retention was about 2.5 g water/g faecal dry matter on average, increases in dry matter represented large increases in faecal water load. Faecal bulking indices (FBI) for most of the breakfast cereals were less than 20 (wheat bran = 100). The content of wheat bran equivalents for faecal bulk (WBE(fb)) in the breakfast cereals was calculated from FBI. Most breakfast cereals contributed, per serve, less than 10% of a theoretical daily reference value for faecal bulk (DRV(fb) = 63 WBE(fb)/day), which was based on data from human clinical trials and dietary fibre recommendations. Based on the WBE(fb) contribution/serving that would be required to meet the DRV(fb) from the number of servings of dietary fibre sources in the CSIRO 12345+ food and nutrition plan, the results suggest that although some high bran breakfast cereals may contribute substantially to, and many are reasonable sources of, faecal bulk, for most of them, one or two servings at breakfast cannot be relied on to effectively redress shortfalls in faecal bulk elsewhere in the diet.

Wheat bran equivalents based on faecal bulking indices for dietary management of faecal bulk

Wheat bran equivalents for faecal bulking (WBEfb) are defined as the gram quantity of wheat bran that would augment faecal bulk to the same extent as a given quantity of a specified food, and its development as a food datum for the dietary management of distal colonic bulk is discussed in this paper. The WBEfb content of a food is derived from the faecal bulking index (FBI), which is a standardised physiological measure of the relative faecal bulking efficacy of foods on an equal edible weight basis. The FBI is defined as the increment in hydrated faecal matter per gram of a food consumed as a percentage of the increment due to the same weight of reference food (1 mm hard red wheat bran; FBI = 100). The FBI values allow the contribution of hydrated solids to the distal colon to be related to that of any reference of known FBI such as wheat bran, the suitability of which as a reference material is discussed. By expressing the increment in bulk as WBEfb, the relative impact of any quantity of an individual food on faecal bulk may be determined, and the effect of foods in mixed diets approximated by summation. Examples are given of the dietary management of distal colonic bulk using WBEfb, with one cup of wheat bran containing 27.5 g of dietary fibre - about the mean recommended daily fibre intake for adults--used as theoretical adequate daily intake of potential faecal bulk. The FBI and WBEfb are proposed as examples of the types of evidence-based data sets that may complement food composition data in selecting foods for physiological function.