Intestinal metabolism of rye lignans in pigs

Application of the INFOGEST Standardized Method to Assess the Digestive Stability and Bioaccessibility of Phenolic Compounds from Galician Extra-Virgin Olive Oil

The INFOGEST standardized method was applied to assess the potential bioaccessibility and bioaccessibility of the phenolic compounds from a Galician extra-virgin olive oil (EVOO). The in vitro digestion model involves three steps and generates two fractions after each one: an aqueous fraction (namely, water phase (Wp)) and an oily fraction (namely, oily phase (Op)). The results showed that secoiridoids were the most abundant family in the Galician EVOO polar fraction, representing 98% of the total phenolic compounds. After oral digestion, phenolic acids and simple phenols were mainly detected in Wp, while lignans and flavonoids were mostly found in Op. After gastric digestion, extensive hydrolysis of secoiridoids was observed to generate free tyrosol, hydroxytyrosol, and hydroxytyrosol acetate. The instability of secoiridoids after intestinal digestion was again responsible for the release of simple phenols, which were mainly recovered in Wp together with flavonoids. In contrast, lignans were stable to duodenal conditions and remained in Op.

Rye Bran Modified with Cell Wall-Degrading Enzymes Influences the Kinetics of Plant Lignans but Not of Enterolignans in Multicatheterized Pigs

Background: Whole-grain intake is associated with a lower risk of chronic Western-style diseases, possibly brought about by the high concentration of phytochemicals, among them plant lignans (PLs), in the grains.Objective: We studied whether treatment of rye bran with cell wall-degrading enzymes changed the solubility and kinetics of PLs in multicatheterized pigs.Methods: Ten female Duroc × Danish Landrace × Yorkshire pigs (60.3 ± 2.3 kg at surgery) fitted with permanent catheters were included in an incomplete crossover study. The pigs were fed 2 experimental diets for 1-7 d. The diets were rich in PLs and based on nontreated lignan-rich [LR; lignan concentration: 20.2 mg dry matter (DM)/kg] or enzymatically treated lignan-rich (ENZLR; lignan concentration: 27.8 mg DM/kg) rye bran. Plasma concentrations of PLs and enterolignans were quantified with the use of targeted LC-tandem mass spectrometry. Data were log transformed and analyzed with mixed-effects, 1-compartment, and asymptotic regression models.Results: The availability of PLs was 38% greater in ENZLR than in LR, and the soluble fraction of PLs was 49% in ENZLR compared with 35% in LR diets. PLs appeared in the circulation 30 min after intake of both the ENZLR and LR diets. Postprandially, consumption of ENZLR resulted in a 4-times-greater (P < 0.0001) plasma PL concentration compared with LR. The area under the curve (AUC) measured 0-360 min after ENZLR intake was ∼2 times higher than after LR intake. A 1-compartment model could describe the postprandial increase in plasma concentration after ENZLR intake, whereas an asymptotic regression model described the plasma concentrations after LR intake. Despite increased available and soluble PLs, ENZLR did not increase plasma enterolignans.Conclusion: The modification of rye bran with cell wall-degrading enzymes resulted in significantly greater plasma concentrations of PLs and the 4-h AUC, particularly syringaresinol, in multicatheterized pigs.

Effect of olive cultivar on bioaccessibility and antioxidant activity of phenolic fraction of virgin olive oil

AIM

This study aims to characterize the phenolic profile and antioxidant capacity of seven monovarietal virgin olive oils (VOOs) and evaluate their in vitro gastrointestinal stability.

METHODS

'Picual', 'Blanqueta', 'Sevillana', 'Habichuelero', and 'Chetoui' olive cultivars were selected for VOO extraction. The oils were subjected to in vitro digestion. The recovery index (RI) of phenolic compounds after each digestion step and the bioaccessibility index (BI) were evaluated. In addition, the antioxidant activity of the bioaccessible fraction (BF) of VOOs was determined by DPPH, ABTS, and ORAC assays, as well as by studying the intracellular reactive oxygen species in Caco-2 cells.

RESULTS

Differences were found in the composition of phenolic compounds in VOOs depending on cultivars. During the digestive process, important losses of phenolic compounds were observed between the buccal and duodenal steps, unlike HTy and Ty, which presented increased recovery due to the hydrolysis of secoiridoid derivatives. Differences in the bioaccessibility of phenolic compounds were found between varieties of VOOs. 'Sevillana' VOO had the highest total bioaccessibility (36%), followed by the 'Picual' (19%), 'Chetoui' (17%), 'Habichuelero' (10%), and 'Blanqueta' (8%) varieties. The BF of all the varieties of VOO showed similar radical ABTS scavenging capacity, 'Chetoui', and 'Blanqueta'-BF having the highest radical DPPH scavenging capacity, and 'Habichuelero' and 'Picual'-BF showing protective effects against the peroxyl radical measured by ORAC_FL assay. All VOO-BFs presented decreases in ROS levels in Caco-2 cells.

CONCLUSIONS

Our results suggest differences in the bioaccessibility of phenolics from diverse VOO varieties, which could lead to different biological properties. Therefore, this study represents a first step toward the development of novel dietary strategies focusing on the phenolic supplementation of different VOOs to preserve human health.

Exposure to phytoestrogens in utero and age at menarche in a contemporary British cohort

Phytoestrogens are estrogenic compounds that occur naturally in plants. Phytoestrogens can cross the placenta, and animal studies have found associations between in utero exposure to phytoestrogens and markers of early puberty. We investigated the association between in utero exposure to phytoestrogens and early menarche (defined as <11.5 years of age at onset) using data from a nested case-control study within the Avon Longitudinal Study of Parents and Children, a longitudinal study involving families living in the South West of England. Concentrations of six phytoestrogens were measured in maternal urine samples collected during pregnancy. Logistic regression was used to explore associations between tertiles of phytoestrogen concentrations and menarche status, with adjustment for maternal age at menarche, maternal education, pre-pregnancy body mass index (BMI), child birth order, duration of breastfeeding, and gestational age at sample collection. Among 367 mother-daughter dyads, maternal median (interquartile range) creatinine-corrected concentrations (in µg/g creatinine) were: genistein 62.1 (27.1-160.9), daidzein 184.8 (88.8-383.7), equol 4.3 (2.8-9.0), O-desmethylangolensin (O-DMA) 13.0 (4.4-34.5), enterodiol 76.1 (39.1-135.8), and enterolactone 911.7 (448.1-1558.0). In analyses comparing those in the highest tertile relative to those in the lowest tertile of in utero phytoestrogen exposure, higher enterodiol levels were inversely associated with early menarche (odds ratio (OR)=0.47; 95% confidence interval (CI): 0.26-0.83), while higher O-DMA levels were associated with early menarche (OR=1.89; 95% CI: 1.04-3.42). These findings suggest that in utero exposure to phytoestrogens may be associated with earlier age at menarche, though the direction of association differs across phytoestrogens.

Rye polyphenols and the metabolism of n-3 fatty acids in rats: a dose dependent fatty fish-like effect

As long-chain fatty acids (LCFA) of the n-3 series are critically important for human health, fish consumption has considerably increased in recent decades, resulting in overfishing to respond to the worldwide demand, to an extent that is not sustainable for consumers’ health, fisheries economy, and marine ecology. In a recent study, it has been shown that whole rye (WR) consumption improves blood and liver n-3 LCFA levels and gut microbiota composition in rats compared to refined rye. The present work demonstrates that specific colonic polyphenol metabolites may dose dependently stimulate the synthesis of n-3 LCFA, possibly through their microbial and hepatic metabolites in rats. The intake of plant n-3 alpha-linolenic acid and WR results in a sort of fatty fish-like effect, demonstrating that the n-3 LCFA levels in blood and tissues could be increased without eating marine foods, and therefore without promoting unsustainable overfishing, and without damaging marine ecology.

Absorption of plant lignans from cereals in an experimental pig model

Plant lignans are diphenolic compounds ingested with whole grains and seeds and converted to enterolignans by the colonic microbiota. In the present study, we investigated absorption and metabolism of plant lignans and enterolignans in vivo after consumption of cereal-based diets. Six pigs fitted with catheters in the mesenteric artery and portal vein and with a flow probe attached to the portal vein along with twenty pigs for quantitative collection of urine were used for this study. The animals were fed bread based on wheat flour low in plant lignans and three lignan-rich breads based on whole-wheat grain, wheat aleurone flour or rye aleurone flour. Plant lignans and enterolignans in plasma were monitored daily at fast after 0-3 d of lignan-rich intake, and on the 4th day of lignan-rich intake a 10-h profile was completed. Urine samples were collected after 11 d of lignan-rich diet consumption. The concentrations of plant lignans were low at fast, and was 1·2-2·6 nmol/l after switching from the low-lignan diet to the lignan-rich diets. However, on the profile day, the concentration and quantitative absorption of plant lignans increased significantly from 33 nmol/h at fast to 310 nmol/h 0-2·5 h after ingestion with a gradual increase in the following periods. Quantitatively, the absorption of plant lignans across diets amounted to 7 % of ingested plant lignans, whereas the urinary excretion of plant lignans was 3 % across diets. In conclusion, there is a substantial postprandial uptake of plant lignans from cereals, suggesting that plant lignans are absorbed from the small intestine.

Whole Rye Consumption Improves Blood and Liver n-3 Fatty Acid Profile and Gut Microbiota Composition in Rats

Background

Whole rye (WR) consumption seems to be associated with beneficial health effects. Although rye fiber and polyphenols are thought to be bioactive, the mechanisms behind the health effects of WR have yet to be fully identified. This study in rats was designed to investigate whether WR can influence the metabolism of n-3 and n-6 long-chain fatty acids (LCFA) and gut microbiota composition.

Methods

For 12 weeks, rats were fed a diet containing either 50% WR or 50% refined rye (RR). The WR diet provided more fiber (+21%) and polyphenols (+29%) than the RR diet. Fat intake was the same in both diets and particularly involved similar amounts of essential (18-carbon) n-3 and n-6 LCFAs.

Results

The WR diet significantly increased the 24-hour urinary excretion of polyphenol metabolites–including enterolactone–compared with the RR diet. The WR rats had significantly more n-3 LCFA–in particular, eicosapentanoic (EPA) and docosahexanoic (DHA) acids–in their plasma and liver. Compared with the RR diet, the WR diet brought significant changes in gut microbiota composition, with increased diversity in the feces (Shannon and Simpson indices), decreased Firmicutes/Bacteroidetes ratio and decreased proportions of uncultured Clostridiales cluster IA and Clostridium cluster IV in the feces. In contrast, no difference was found between groups with regards to cecum microbiota. The WR rats had lower concentrations of total short-chain fatty acids (SCFA) in cecum and feces (p<0.05). Finally, acetate was lower (p<0.001) in the cecum of WR rats while butyrate was lower (p<0.05) in the feces of WR rats.

Interpretation

This study shows for the first time that WR consumption results in major biological modifications–increased plasma and liver n-3 EPA and DHA levels and improved gut microbiota profile, notably with increased diversity–known to provide health benefits. Unexpectedly, WR decreased SCFA levels in both cecum and feces. More studies are needed to understand the interactions between whole rye (fiber and polyphenols) and gut microbiota and also the mechanisms of action responsible for stimulating n-3 fatty acid metabolism.

Elucidation of arctigenin pharmacokinetics after intravenous and oral administrations in rats: integration of in vitro and in vivo findings via semi-mechanistic pharmacokinetic modeling

Although arctigenin (AR) has attracted substantial research interests due to its promising and diverse therapeutic effects, studies regarding its biotransformation were limited. The current study aims to provide information regarding the pharmacokinetic properties of AR via various in vitro and in vivo experiments as well as semi-mechanistic pharmacokinetic modeling. Our in vitro rat microsome incubation studies revealed that glucuronidation was the main intestinal and liver metabolic pathway of AR, which occurred with V max, K m, and Clint of 47.5 ± 3.4 nmol/min/mg, 204 ± 22 μM, and 233 ± 9 μl/min/mg with intestinal microsomes and 2.92 ± 0.07 nmol/min/mg, 22.7 ± 1.2 μM, and 129 ± 4 μl/min/mg with liver microsomes, respectively. In addition, demethylation and hydrolysis of AR occurred with liver microsomes but not with intestinal microsomes. In vitro incubation of AR and its metabolites in intestinal content demonstrated that glucuronides of AR excreted in bile could be further hydrolyzed back to the parent compound, suggesting its potential enterohepatic circulation. Furthermore, rapid formation followed by fast elimination of arctigenic acid (AA) and arctigenin-4'-O-glucuronide (AG) was observed after both intravenous (IV) and oral administrations of AR in rats. Linear pharmacokinetics was observed at three different doses for AR, AA, and AG after IV administration of AR (0.48-2.4 mg/kg, r (2) > 0.99). Finally, an integrated semi-mechanistic pharmacokinetic model using in vitro enzyme kinetic and in vivo pharmacokinetic parameters was successfully developed to describe plasma concentrations of AR, AA, and AG after both IV and oral administration of AR at all tested doses.

Extra virgin olive oil phenolics: absorption, metabolism, and biological activities in the GI tract

Olive oil, a typical ingredient of the Mediterranean diet, possesses many beneficial health effects. The biological activities ascribed to olive oil consumption are associated in part to its phenolics constituents, and mainly linked to the direct or indirect antioxidant activity of olive oil phenolics and their metabolites, which are exerted more efficiently in the gastrointestinal (GI) tract, where dietary phenolics are more concentrated when compared to other organs. In this regard, we present a brief overview of the metabolism, biological activities, and anticancer properties of olive oil phenolics in the GI tract.

Quantitative aspects of the metabolism of lignans in pigs fed fibre-enriched rye and wheat bread

A diet rich in lignans has been suggested to be protective against a range of chronic diseases. The distribution and metabolic fate of lignans is, however, very poorly understood. We fed high-fibre wheat breads low in lignans (n 8) or high-fibre rye breads (n 9) rich in plant lignans to pigs for 58-67 d, and analysed the content of plant lignans and their metabolites in the diet, blood, bile, faeces, urine and selected tissues. Apparent faecal digestibility of dietary precursors was higher than of total (plant- and entero-) lignans due to conversion to enterolactone and enterodiol. The digestibility of lariciresinol and matairesinol was lower than that of the sum of plant lignans. This suggests that interconversion of plant lignans during digestion and enterohepatic circulation occur without complete conversion to enterolignans. The majority of lignans present in plasma and urine was in the form of enterolignans, but up to 23 % in the plasma, and 11 % in the urine of the rye-fed pigs were in the form of plant lignans. There was a very high concentration of lignans in bile from the rye-fed pigs with as much as 77 % in the form of plant lignans. Lignans were detected in the tissue of colon, liver, breast and brain at a much higher level with rye than with wheat, but only in the form of enterolactone. The importance and implications of systemic exposure to plant lignans remain to be elucidated.

Metabolism of the lignan macromolecule into enterolignans in the gastrointestinal lumen as determined in the simulator of the human intestinal microbial ecosystem

Estrogenic plant compounds from the human diet such as the lignan secoisolariciresinol diglucoside (SDG, 1) can exert biological activity in the human body upon ingestion and bioactivation to enterodiol (END, 5) and enterolactone (ENL, 6). Bioavailability of lignans is influenced by the food matrix and gut microbial action, of which the latter is subject to a large interindividual variation. In this study, the fate of the lignan precursor SDG, present in the lignan macromolecule of flax seed ( Linum usitatissimum), was determined during an artificial stomach and small intestinal digestion and during metabolism by two different enterolignan phenotypes in a TWINSHIME environment (TWIN Simulator of the Human Intestinal Microbial Ecosystem). The lignan macromolecule acted as a delivery system of SDG in the large intestine. SDG was only hydrolyzed into secoisolariciresinol (SECO, 2) through microbial action in the ascending colon, after which it was bioactivated into enterolignans from the transverse colon onward. Single demethylation was a first step in the bioactivation, followed by dehydroxylation. Enterolignan phenotypes remained stable throughout the experimental period. The establishment of END and ENL production equilibria reflected the subdominance of ENL-producing bacteria in the gastrointestinal tract.

Lignans and human health

This review focuses on the possible role in human health of the consumption of lignan-rich foods. Most of the plant lignans in human foods are converted by the intestinal microflora in the upper part of the large bowel to enterolactone and enterodiol, called mammalian or enterolignans. The protective role of these compounds, particularly in chronic Western diseases, is discussed. Evidence suggests that fiber- and lignan-rich whole-grain cereals, beans, berries, nuts, and various seeds are the main protective foods. Many factors, in addition to diet, such as intestinal microflora, smoking, antibiotics, and obesity affect circulating lignan levels in the body. Lignan-rich diets may be beneficial, particularly if consumed for life. Experimental evidence in animals has shown clear anticarcinogenic effects of flaxseed or pure lignans in many types of cancer. Many epidemiological results are controversial, partly because the determinants of plasma enterolactone are very different in different countries. The source of the lignans seems to play a role because other factors in the food obviously participate in the protective effects. The results are promising, but much work is still needed in this area of medicine.

Whole grain food intake elevates serum enterolactone

Both intake of whole grain and higher levels of serum enterolactone have been related to reduced risk for CHD and some cancers. Because lignans are prevalent in the outer layers of grains, these findings may be related. We carried out a crossover feeding study in which overweight, hyperinsulinaemic, non-diabetic men (n5) and women (n6) ate, in random order, wholegrain foods or refined-grain foods in a diet with 30% energy from fat. The dominant whole grain was wheat, followed by oats and rice. All food was supplied by the investigators and each diet lasted for 6 weeks, with an intervening washout period of 6–9 weeks. Serum enterolactone concentrations were higher when eating the wholegrain than the refined-grain diet by 6·2 (within person SE 1·7) nmol/l (P=0·0008). Most of the increase in serum enterolactone when eating the wholegrain diet occurred within 2 weeks, though the serum enterolactone difference between wholegrain and refined-grain diets continued to increase through 6 weeks. Serum enterolactone concentrations can be raised by eating a diet rich in whole grains.

A newly constructed and validated isoflavone database for the assessment of total genistein and daidzein intake

The principal phyto-oestrogens (PO) in food are isoflavones, lignans, coumestans and prenylated flavonoids, with isoflavones and lignans being the most commonly found in UK diets. Until recently obtaining accurate data on the PO content of foods was hampered by lack of suitable analytical methods and validation techniques. Furthermore, although PO data exist for some foods, these foods may not be available in the UK. The aim of the present study was to construct a new, comprehensive isoflavone (total genistein + daidzein) database. Using data, mainly from recent GC–MS analysis, for approximately 300 foods available in the UK, and extensive recipe calculations, a new database was constructed containing approximately 6000 foods allocated an isoflavone value. By analysing 7d weighed food diaries, the database was subsequently used to estimate isoflavone intake in two groups of healthy volunteers, omnivores (n9) and vegetarians (n10). Mean isoflavone intake in the vegetarian and omnivorous group was 7·4 (sem 3·05) and 1·2 (sem 0·43) mg/d, respectively. Mean intake for the total group was 4·5 (sem 1·89) mg/d. Main food sources of isoflavones for the vegetarian group were soya milk (plain), meat-substitute foods containing textured vegetable protein and soya protein isolate, soya mince, wholemeal bread and rolls, white bread and rolls, croissants and pitta breads, beans, raisins and soya sauce. Main food sources of isoflavones for the omnivorous group were soya yogurts, wholemeal bread and rolls, white bread and rolls, garlic bread, nan bread and brown bread, sultanas and scones.

Pharmacokinetics of enterolignans in healthy men and women consuming a single dose of secoisolariciresinol diglucoside

High concentrations of enterolignans in plasma are associated with a lower risk of acute coronary events. However, little is known about the absorption and excretion of enterolignans. The pharmacokinetic parameters and urinary excretion of enterodiol and enterolactone were evaluated after consumption of their purified plant precursor, secoisolariciresinol diglucoside (SDG). Twelve healthy volunteers ingested a single dose of purified SDG (1.31 micromol/kg body wt). Enterolignans appeared in plasma 8-10 h after ingestion of the purified SDG. Enterodiol reached its maximum plasma concentration 14.8 +/- 5.1 h (mean +/- SD) after ingestion of SDG, whereas enterolactone reached its maximum 19.7 +/- 6.2 h after ingestion. The mean elimination half-life of enterodiol (4.4 +/- 1.3 h) was shorter than that of enterolactone (12.6 +/- 5.6 h). The mean area under the curve of enterolactone (1762 +/- 1117 nmol/L . h) was twice as large as that of enterodiol (966 +/- 639 nmol/L . h). The mean residence time for enterodiol was 20.6 +/- 5.9 h and that for enterolactone was 35.8 +/- 10.6 h. Within 3 d, up to 40% of the ingested SDG was excreted as enterolignans via urine, with the majority (58%) as enterolactone. In conclusion, a substantial part of enterolignans becomes available in the blood circulation and is subsequently excreted. The measured mean residence times and elimination half-lives indicate that enterolignans accumulate in plasma when consumed 2-3 times a day and reach steady state. Therefore, plasma enterolignan concentrations are expected to be good biomarkers of dietary lignan exposure and can be used to evaluate the effects of lignans.

Whole-grain rye bread consumption by women correlates with plasma alkylresorcinols and increases their concentration compared with low-fiber wheat bread

Whole-grain rye and wheat products are rich in lignans, the precursors of enterolactone (ENL) and alkylresorcinols (ARs), which are phenolic lipids. In this crossover trial, we examined the effect of whole-grain rye bread compared with low-fiber wheat bread on plasma AR levels. Women (n = 39) aged 59 +/- 0.94 y (mean +/- SEM) were advised to consume rye (214 +/- 7.1 g/d) or wheat (178 +/- 6.5 g/d) bread (20% of total daily energy intake) in random order for 8 wk. The test periods were separated by an 8-wk washout period. ARs with different homologues and ENL were measured in plasma collected at the beginning (habitual diet) and end of the test bread periods. AR concentrations were higher (P < 0.001) after the rye bread (352 +/- 24.7 nmol/L) and habitual diet (97.7 +/- 12.1 and 88.3 +/- 8.7 nmol/L) periods than after the wheat bread period (36.6 +/- 4.2 nmol/L). Plasma AR concentrations were correlated with intake of rye bread (r = 0.34, P = 0.037), and with insoluble fiber from the whole diet during the rye (r = 0.39, P = 0.013) and wheat (r = 0.32, P = 0.047) bread periods. The plasma AR 17:0/21:0 ratio differed after the rye (0.84 +/- 0.04) and wheat (0.53 +/- 0.08) bread diet periods (P < 0.001). These data strongly suggest that plasma ARs could be used as specific biomarkers for whole-grain rye intake, and their homologue pattern could be used as an indicator of the bread type consumed.

Rye bread in the diet of pigs enhances the formation of enterolactone and increases its levels in plasma, urine and feces

To obtain new insight into the quantitative and qualitative metabolism of rye and wheat lignans, we performed three series of experiments with catheterized pigs. Two diets with similar levels of dietary fiber and macronutrients but with contrasting levels of plant lignans (isolariciresinol, lariciresinol, matairesinol, pinoresinol, secoisolariciresinol and syringaresinol) were prepared from rye (high in lignans) and wheat (low in lignans) soft and crisp breads. In two series of experiments we quantified the uptake from the gut of enterolactone in four pigs fitted with catheters in the portal vein and mesenteric artery and with an ultrasonic flow probe attached to the portal vein to monitor the blood flow. In a third study with six pigs, we quantified the bioavailability of the plant lignans that can be converted to enterolactone (lariciresinol, matairesinol, pinoresinol, secoisolariciresinol and syringaresinol) and the concentration in the peripheral blood. Plant and mammalian lignans in diets and stool were analyzed by isotope dilution gas chromatography-mass spectrometry and enterolactone in plasma and urine determined by time-resolved fluoroimmunoassay. There was a significantly higher formation of enterolactone in pigs fed the rye diet, and higher fecal and urinary excretion and circulating levels of mammalian lignans than in pigs fed the wheat diet. The conversion of mammalian lignan precursors to enterolactone was 48% with the wheat diet and 60% with the rye diet. Mammalian lignans are absorbed by passive diffusion from the large intestine and a substantial fraction of the absorbed mammalian lignans undergoes enterohepatic circulation, resulting in low diurnal variation in plasma levels of enterolactone.

Whole-grain rye and wheat foods and markers of bowel health in overweight middle-aged men

BACKGROUND

Whole-grain cereal foods including rye have been identified as providing significant health benefits that do not occur when refined-cereal foods are ingested.

OBJECTIVES

Foods (90 g) containing whole-grain rye flour and whole-grain wheat flour were compared with low-fiber refined-cereal foods for their effects on markers of bowel health and the metabolic markers insulin and glucose.

DESIGN

Three 4-wk interventions were undertaken in a randomized crossover design with 28 overweight men aged 40-65 y who had no history of bowel disease. Against a background intake of 14 g dietary fiber (DF), the men were fed low-fiber cereal grain foods providing 5 g DF for a total of 19 g DF/d. High-fiber wheat foods provided 18 g DF, and high-fiber rye foods provided 18 g DF, both giving a total of 32 g DF/d. Fecal samples (48-h) and fasting and postprandial blood samples were collected at the end of each period and assayed.

RESULTS

Both high-fiber rye and wheat foods increased fecal output by 33-36% (P = 0.004) and reduced fecal beta-glucuronidase activity by 29% (P = 0.027). Postprandial plasma insulin was decreased by 46-49% (P = 0.0001) and postprandial plasma glucose by 16-19% (P = 0.0005). Rye foods were associated with significantly (P = 0.0001) increased plasma enterolactone (47% and 71%) and fecal butyrate (26% and 36%), relative to wheat and low-fiber options, respectively.

CONCLUSIONS

High-fiber rye and wheat food consumption improved several markers of bowel and metabolic health relative to that of low-fiber food. Fiber from rye appears more effective than that from wheat in overall improvement of biomarkers of bowel health.

Mammalian phytoestrogens: enterodiol and enterolactone

The mammalian phytoestrogens enterodiol (END) and enterolactone (ENL) are produced in the colon by the action of bacteria on the plant precursors matairesinol (MAT), secoisolariciresinol (SECO), their glycosides, and other precursors in the diet. Both END and ENL have been shown to possess weakly estrogenic and antiestrogenic activities, and it has been suggested that the high production of these antiestrogenic mammalian lignans in the gut may serve to protect against breast cancer in women and prostate cancer in men. Various in vitro experiments suggested END and ENL significantly inhibited the growth of human colon tumor cells, and the E2-induced proliferation of MCF-7 breast cancer cells was inhibited by ENL. The protective effects of mammalian lignans may be due to their ability to compete with E2 for the type II estrogen receptor, to induce sex hormone binding globulin (SHBG), to inhibit placental aromatase, and to act as antioxidants. This review mainly deals with the chemistry, quantitative analysis, biological properties and health effects of END and ENL.

Enterolignans

A review with 114 references about mammalian lignans (enterolignans). Several aspects have been reviewed: the precursors of mammalian lignans and their biosynthesis, biological activities and health effects, metabolism (in vivo and in vitro) in human and animals, some synthetic strategies to obtain enterolignan skeleton types, including the synthesis of haptens and deuterated lignans, and finally an overview of the analytical methods to detect and quantify lignans in biological matrices and foods.

Phyto-oestrogens and cancer

Phyto-oestrogens have been suggested to have a preventive effect against various cancers. This review includes a discussion of the consumption of phyto-oestrogen-rich foods such as soy, a source of isoflavones, and whole grain products, which contain lignans, and their role in the prevention of breast, prostate, and colon cancer. In women, a soy-containing diet is only slightly protective against breast cancer, if at all, but is more likely to be beneficial if initiated before puberty or during adolescence. These findings are supported by conclusions of studies of immigrants and other epidemiological studies. However, in one case-control study and one prospective study, a low-lignan diet increased the risk of breast cancer. Experimental evidence also exists for an inhibitory effect of soy and rye bran on prostate-cancer growth and for rye bran or isolated lignans on colon cancer. Whether these observed protective effects are caused by the presence of dietary phyto-oestrogens, or whether they are merely indicators of a healthy diet in general, has not been established.