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Our pilot study examined the potential of exhaled breath analysis in studying the metabolic effects of dietary fiber (DF). We hypothesized that a high-fiber diet (HFD) containing whole grain rye changes volatile organic compound (VOC) levels in exhaled breath and that consuming a single meal affects these levels. Seven healthy men followed a week-long low-fiber diet (17 g/d) and HFD (44 g/d) in a randomized crossover design. A test meal containing 50 g of the available carbohydrates from wheat bread was served as breakfast after each week. Alveolar exhaled breath samples were analyzed at fasting state and 30, 60, and 120 minutes after this meal parallel to plasma glucose, insulin, and serum lipids. We used solid-phase microextraction and gas chromatography-mass spectrometry for detecting changes in 15 VOCs. These VOCs were acetone, ethanol, 1-propanol, 2-propanol, 1-butanol, acetic acid, propionic acid, butyric acid, valeric acid, isovaleric acid, 2-methylbutyric acid, hexanoic acid, acetoin, diacetyl, and phenol. Exhaled breath 2-methylbutyric acid in the fasting state and 1-propanol at 120 minutes decreased (P = .091 for both) after an HFD. Ingestion of the test meal increased ethanol, 1-propanol, acetoin, propionic acid, and butyric acid levels while reducing acetone, 1-butanol, diacetyl, and phenol levels. Both DF diet content and having a single meal affected breathVOCs. Exploring exhaled breath further could help to develop tools for monitoring the metabolic effects of DF., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The bioavailability of whole-grain rye-derived phytochemicals has not yet been comprehensively characterized, and different baking and manufacturing processes can modulate the phytochemical composition of breads and other rye products. The aim of our study was to find key differences in the phytochemical profile of plasma after the consumption of 3 breads containing rye bran when compared with a plain white wheat bread control. Plasma metabolite profiles of 12 healthy middle-aged men and women were analyzed using LC quadrupole time-of-flight mass spectrometry metabolomics analysis while fasting and at 60 min, 120 min, 240 min, and 24 h after consuming a meal that contained either 100% whole-grain sourdough rye bread or white wheat bread enriched with native unprocessed rye bran or bioprocessed rye bran. White wheat bread was used as the control. The meals were served in random order after a 12-h overnight fast, with at least 3 d between each occasion. Two sulfonated phenylacetamides, hydroxy-N-(2-hydroxyphenyl) acetamide and N-(2-hydroxyphenyl) acetamide, potentially derived from the benzoxazinoid metabolites, were among the most discriminant postprandial plasma biomarkers distinguishing intake of breads containing whole-meal rye or rye bran from the control white wheat bread. Furthermore, subsequent metabolite profiling analysis of the consumed breads indicated that different bioprocessing/baking techniques involving exposure to microbial metabolism (e.g., sourdough fermentation) have a central role in modulating the phytochemical content of the whole-grain and bran-rich breads., (© 2014 American Society for Nutrition.)

Whole-grain (WG) foods rich in indigestible carbohydrates are thought to modulate the composition of the intestinal microbiota. We investigated in a randomized, parallel, 2-arm 12-wk intervention whether consumption of WG and fiber-rich rye breads compared with refined wheat breads affected the microbiota composition in Finnish individuals aged 60 ± 6 y with metabolic syndrome. Fecal samples from 51 participants (25 males, 26 females) before and after the intervention were processed for the microbiota analysis using a phylogenetic microarray and quantitative polymerase chain reactions targeting the 16S rRNA gene. The intake of whole grains calculated from food records was higher in the group consuming rye breads (75 g) than in that consuming refined wheat breads (4 g; P < 0.001), confirmed by fasting plasma alkylrecorsinol concentrations, a biomarker of whole grain intake. The intestinal microbiota composition did not significantly differ between the groups after the intervention. However, we detected a 37% decrease of Bacteroidetes (P < 0.05) in parallel to a 53% decrease in the alkylrecorsinol concentration (P < 0.001) in the group consuming refined wheat breads. In this group, the abundance of bacteria related to Bacteroides vulgatus, B. plebeius, and Prevotella tannerae decreased, whereas that of bacteria related to Collinsella and members of the Clostridium clusters IV and XI increased. In a multivariate regression analysis, the abundance of Bacteroides spp. was best explained by different fat compounds among dietary variables, whereas the main sugar-converting butyrate-producers were mostly associated with the intake of whole- and refined-grain bread and fiber. Our results indicate that the quality of grains has a minor effect on the intestinal microbiota composition in participants with metabolic syndrome and suggest that the dietary influence on the microbiota involves other dietary components such as fat.

Dietary fiber is a nutritional concept based not on physiological functions but on defined chemical and physical properties. Recent definitions of dietary fiber differentiate inherent plant cell wall-associated fiber from isolated or synthetic fiber. For the latter to be defined as fiber, beneficial physiological effects should be demonstrated, such as laxative effects, fermentability, attenuation of blood cholesterol levels, or postprandial glucose response. Grain fibers are a major natural source of dietary fiber worldwide, while inulin, a soluble indigestible fructose polymer isolated from chicory, and polydextrose, a synthetic indigestible glucose polymer, have more simple structures. Inulin and polydextrose show many of the same functionalities of grain fiber in the large intestine, in that they are fermentable, bifidogenic, and laxative. The reported effects on postprandial blood glucose and fasting cholesterol levels have been modest, but grain fibers also show variable effects. New biomarkers are needed to link the physiological functions of specific fibers with long-term health benefits., (© 2011 International Life Sciences Institute.)

Background Wholegrain consumption has been associated with beneficial health effects including reduction of diabetes and cancer risk; however, the underlying mechanisms are not fully understood. Objective The aim of this study was to characterize the effects of wholegrain rye intake on circulating metabolites in a human intervention study using untargeted metabolomics. Methods The intervention consisted of 2 successive 4-wk periods in a randomized crossover design, where 15 adults consumed wholegrain rye bread (WGR) or white wheat bread enriched with fermented rye bran (WW+RB), following a 4-wk rye-free period with white wheat bread (WW). Fasting plasma samples were collected at the end of each period and analyzed using liquid chromatography-mass spectrometry. Metabolic profiles were compared to identify compounds discriminating WGR from the WW+RB and WW periods. Because peripheral serotonin is produced mainly in the gut, a hypothesis of its altered biosynthesis as a response to increased cereal fiber intake was tested by measuring intestinal serotonin of mice fed for 9 wk on a high-fat diet supplemented with different sources of fiber (rye bran flour, ground wheat aleurone, or powdered cellulose). Results Five endogenous metabolites and 15 rye phytochemicals associated with WGR intake were identified. Plasma concentrations of serotonin, taurine, and glycerophosphocholine were significantly lower after the WGR than WW period (Q  < 0.05). Concentrations of 2 phosphatidylethanolamine plasmalogens, PE(18:2/P-18:0) and PE(18:2/P-16:0), were lower after the WGR period than the WW+RB period (Q  < 0.05). The concentration of serotonin was significantly lower in the colonic tissue of mice that consumed rye bran or wheat aleurone compared with cellulose (P  < 0.001). Conclusions Wholegrain rye intake decreases plasma serotonin in healthy adults when compared with refined wheat. Intake of rye bran and wheat aleurone decreases colonic serotonin in mice. These results suggest that peripheral serotonin could be a potential link between wholegrain consumption and its associated health effects. Data used in the study were derived from a trial registered at www.clinicaltrials.gov as NCT03550365. [ABSTRACT FROM AUTHOR]

Abstract: Glycemic responses to most of the conventional breads are high, including breads made of wholemeal flour. Baking technology is known to affect these responses. The aim of the present study was to investigate effects of xylanase enzyme treatment and sourdough fermentation in wholemeal wheat bread baking on postprandial glucose and insulin responses and on in vitro protein digestibility. The wheat breads were made of 100% flour from peeled kernels by a straight dough or sourdough fermentation method, and with or without using xylanase during mixing of dough. Standard white wheat bread was used as a reference. All test bread portions contained 50g available carbohydrate and were served in random order to eleven insulin resistant subjects. Blood samples for measuring glucose and insulin concentrations were drawn over 4h. The sourdough wholemeal wheat bread resulted in the lowest postprandial glucose and insulin responses among the four tested breads (treatment×time; p=0.000 and p=0.022, respectively). There were differences in solubility and depolymerisation of protein and arabinoxylan among the breads but these did not fully explain the in vivo findings. In conclusion, the health effects of wholemeal wheat bread can be further improved by using sourdough process in breadmaking. [Copyright &y& Elsevier]