Derivation and Validation of a Total Fruit and Vegetable Intake Prediction Model to Identify Targets for Biomarker Discovery Using the UK National Diet and Nutrition Survey.

BACKGROUND: Dietary assessments in research and clinical settings are largely reliant on self-reported questionnaires. It is acknowledged that these are subject to measurement error and biases and that objective approaches would be beneficial. Dietary biomarkers have been purported as a complementary approach to improve the accuracy of dietary assessments. Tentative biomarkers have been identified for many individual fruits and vegetables (FVs), but an objective total FV intake assessment tool has not been established. OBJECTIVES: To derive and validate a prediction model of total FV intake (TFVpred) to inform future biomarker studies. METHODS: Data from the National Diet and Nutrition Survey (NDNS) were used for this analysis. A modeling group (MG) consisting of participants aged >11 years from the NDNS years 5-6 was created (n = 1746). Intake data for 96 FVs were analyzed by stepwise regression to derive a model that satisfied 3 selection criteria: SEE ≤80, R2 >0.7, and ≤10 predictors. The TFVpred model was validated using comparative data from a validation group (VG) created from the NDNS years 7-8 (n = 1865). Pearson's correlation coefficients were assessed between observed and predicted values in the MG and VG. Bland-Altman plots were used to assess agreement between TFVpred estimates and total FV intake. RESULTS: A TFVpred model, comprised of tomatoes, apples, carrots, bananas, pears, strawberries, and onions, satisfied the selection criteria (R2 = 0.761; SEE = 78.81). Observed and predicted total FV intake values were positively correlated in the MG (r = 0.872; P < 0.001; R2 = 0.761) and the VG (r = 0.838; P < 0.001; R2 = 0.702). In the MG and VG, 95.0% and 94.9%, respectively, of TFVpred model residuals were within the limits of agreement. CONCLUSIONS: Intakes of a concise FV list can be used to predict total FV intakes in a UK population. The individual FVs included in the TFVpred model present targets for biomarker discovery aimed at objectively assessing total FV intake.

Differential effects of resveratrol on the dilator responses of femoral arteries, ex vivo.

Resveratrol is a plant-derived phytoalexin with antioxidant, anti-inflammatory and cardio-protective properties and may be a promising therapeutic intervention strategy in cardiovascular disease. Here, we investigated the acute direct effects of trans-resveratrol (RV), on acetylcholine (ACh)-induced and flow-mediated dilation (FMD) of isolated pressurized femoral arteries of young (4-month-old) and old (26-month-old) mice. Vessel exposure to RV enhanced ACh (0.01-1.0 mM)-induced dilation (p < 0.05), but not FMD (@ 5-10 µL⋅min-1) (p < 0.05) in both young and old mice. After RV incubation, acute nitric oxide (NO) production by cultured endothelial cells was increased in response to 0.01 mM ACh, but reduced by flow (5-10 µL⋅min-1; p < 0.05). In isolated femoral arteries from endothelial nitric oxide synthase knockout (eNOS-/-) mice, RV had no overall effect on FMD, but potentiated ACh induced dilation, that was completely abolished by potassium channel blockers, Apamin and Tram 34 (p < 0.01). We demonstrate that the non-metabolised form of RV stimulates ACh-induced dilation via the NO and EDHF pathways, but not FMD by interaction with the cyclo-oxygenase pathway. Our findings have important implications in the use of RV (for both young and aged) under 'normal' non-diseased physiological states.

The effects of chronic trans-resveratrol supplementation on aspects of cognitive function, mood, sleep, health and cerebral blood flow in healthy, young humans.

Single doses of resveratrol have previously been shown to increase cerebral blood flow (CBF) with no clear effect on cognitive function or mood in healthy adults. Chronic resveratrol consumption may increase the poor bioavailability of resveratrol or otherwise potentiate its psychological effects. In this randomised, double-blind, placebo-controlled, parallel-groups study, a total of sixty adults aged between 18 and 30 years received either placebo or resveratrol for 28 d. On the 1st and 28th day of treatment, the performance of cognitively demanding tasks (serial subtractions, rapid visual information processing and 3-Back) (n 41 complete data sets) was assessed, alongside blood pressure (n 26) and acute (near-IR spectroscopy (NIRS)) and chronic (transcranial Doppler) measures of CBF (n 46). Subjective mood, sleep quality and health questionnaires were completed at weekly intervals (n 53/54). The results showed that the cognitive effects of resveratrol on day 1 were restricted to more accurate but slower serial subtraction task performance. The only cognitive finding on day 28 was a beneficial effect of resveratrol on the accuracy of the 3-Back task before treatment consumption. Subjective ratings of 'fatigue' were significantly lower across the entire 28 d in the resveratrol condition. Resveratrol also resulted in modulation of CBF parameters on day 1, as assessed by NIRS, and significantly increased diastolic blood pressure on day 28. Levels of resveratrol metabolites were significantly higher both before and after the day's treatment on day 28, in comparison with day 1. These results confirm the acute CBF effects of resveratrol and the lack of interpretable cognitive effects.

Effects of resveratrol alone or in combination with piperine on cerebral blood flow parameters and cognitive performance in human subjects: a randomised, double-blind, placebo-controlled, cross-over investigation.

Previous research has shown that resveratrol can increase cerebral blood flow (CBF) in the absence of improved cognitive performance in healthy, young human subjects during the performance of cognitively demanding tasks. This lack of cognitive effects may be due to low bioavailability and, in turn, reduced bioefficacy of resveratrol in vivo. Piperine can alter polyphenol pharmacokinetics, but previous studies have not investigated whether this affects the efficacy of the target compound. Therefore, the objective of the present study was to ascertain whether co-supplementation of piperine with resveratrol affects the bioavailability and efficacy of resveratrol with regard to cognition and CBF. The present study utilised a randomised, double-blind, placebo-controlled, within-subjects design, where twenty-three adults were given placebo, trans-resveratrol (250 mg) and trans-resveratrol with 20 mg piperine on separate days at least a week apart. After a 40 min rest/absorption period, the participants performed a selection of cognitive tasks and CBF was assessed throughout the period, in the frontal cortex, using near-IR spectroscopy. The presence of resveratrol and its conjugates in the plasma was confirmed by liquid chromatography-MS analysis carried out following the administration of the same doses in a separate cohort (n 6). The results indicated that when co-supplemented, piperine and resveratrol significantly augmented CBF during task performance in comparison with placebo and resveratrol alone. Cognitive function, mood and blood pressure were not affected. The plasma concentrations of resveratrol and its metabolites were not significantly different between the treatments, which indicates that co-supplementation of piperine with resveratrol enhances the bioefficacy of resveratrol with regard to CBF effects, but not cognitive performance, and does this without altering bioavailability.

Oral green tea catechin metabolites are incorporated into human skin and protect against UV radiation-induced cutaneous inflammation in association with reduced production of pro-inflammatory eicosanoid 12-hydroxyeicosatetraenoic acid.

Green tea catechins (GTC) reduce UV radiation (UVR)-induced inflammation in experimental models, but human studies are scarce and their cutaneous bioavailability and mechanism of photoprotection are unknown. We aimed to examine oral GTC cutaneous uptake, ability to protect human skin against erythema induced by a UVR dose range and impact on potent cyclo-oxygenase- and lipoxygenase-produced mediators of UVR inflammation, PGE2 and 12-hydroxyeicosatetraenoic acid (12-HETE), respectively. In an open oral intervention study, sixteen healthy human subjects (phototype I/II) were given low-dose GTC (540 mg) with vitamin C (50 mg) daily for 12 weeks. Pre- and post-supplementation, the buttock skin was exposed to UVR and the resultant erythema quantified. Skin blister fluid and biopsies were taken from the unexposed and the UVR-exposed skin 24 h after a pro-inflammatory UVR challenge (three minimal erythema doses). Urine, skin tissue and fluid were analysed for catechin content and skin fluid for PGE2 and 12-HETE by liquid chromatography coupled to tandem MS. A total of fourteen completing subjects were supplement compliant (twelve female, median 42.5 years, range 29-59 years). Benzoic acid levels were increased in skin fluid post-supplementation (P= 0.03), and methylated gallic acid and several intact catechins and hydroxyphenyl-valerolactones were detected in the skin tissue and fluid. AUC analysis for UVR erythema revealed reduced response post-GTC (P= 0.037). Pre-supplementation, PGE2 and 12-HETE were UVR induced (P= 0.003, 0.0001). After GTC, UVR-induced 12-HETE reduced from mean 64 (sd 42) to 41 (sd 32) pg/µl (P= 0.01), while PGE2 was unaltered. Thus, GTC intake results in the incorporation of catechin metabolites into human skin associated with abrogated UVR-induced 12-HETE; this may contribute to protection against sunburn inflammation and potentially longer-term UVR-mediated damage.

Predicting phenolic acid absorption in Caco-2 cells: a theoretical permeability model and mechanistic study.

There is a considerable need to rationalize the membrane permeability and mechanism of transport for potential nutraceuticals. The aim of this investigation was to develop a theoretical permeability equation, based on a reported descriptive absorption model, enabling calculation of the transcellular component of absorption across Caco-2 monolayers. Published data for Caco-2 permeability of 30 drugs transported by the transcellular route were correlated with the descriptors 1-octanol/water distribution coefficient (log D, pH 7.4) and size, based on molecular mass. Nonlinear regression analysis was used to derive a set of model parameters a', ß', and b' with an integrated molecular mass function. The new theoretical transcellular permeability (TTP) model obtained a good fit of the published data (R² = 0.93) and predicted reasonably well (R² = 0.86) the experimental apparent permeability coefficient (P(app)) for nine non-training set compounds reportedly transported by the transcellular route. For the first time, the TTP model was used to predict the absorption characteristics of six phenolic acids, and this original investigation was supported by in vitro Caco-2 cell mechanistic studies, which suggested that deviation of the P(app) value from the predicted transcellular permeability (P(app)(trans)) may be attributed to involvement of active uptake, efflux transporters, or paracellular flux.

Absorption and metabolism of chlorogenic acids in cultured gastric epithelial monolayers.

Gastric absorption of feruloylquinic acid and di-O-caffeoylquinic acid analogs has never been investigated despite their potential contribution to the proposed beneficial health effects leading to reduced risk of type 2 diabetes. Using a cultured gastric epithelial model, with an acidic apical pH, the relative permeability coefficients (P(app)) and metabolic fate of a series of chlorogenic acids (CGAs) were investigated. Mechanistic studies were performed in the apical to basal direction and demonstrated differential rates of absorption for different CGA subgroups. For the first time, we show intact absorption of feruloylquinic acids and caffeoylquinic acid lactones across the gastric epithelium (P(app) ∼ 0.2 cm/s). Transport seemed to be mainly by passive diffusion, because good linearity was observed over the incubation period and test concentrations, and we speculate that a potential carrier-mediated component may be involved in uptake of certain 4-acyl CGA isomers. In contrast, absorption of intact di-O-caffeoylquinic acids was rapid (P(app) ∼ 2-10 cm/s) but nonlinear with respect to time and concentration dependence, which was potentially limited by interaction with an efflux transporter and/or pH gradient dependence. For the first time, methylation is shown in gastric mucosa. Furthermore, isoferulic acid, dimethoxycinnamic acid, and ferulic acid were identified as novel gastric metabolites of CGA biotransformation. We propose that the stomach is the first location for the release of hydroxycinnamic acids, which could explain their early detection after coffee consumption.

Coordination between microbiota and root endodermis supports plant mineral nutrient homeostasis.

Plant roots and animal guts have evolved specialized cell layers to control mineral nutrient homeostasis. These layers must tolerate the resident microbiota while keeping homeostatic integrity. Whether and how the root diffusion barriers in the endodermis, which are critical for the mineral nutrient balance of plants, coordinate with the microbiota is unknown. We demonstrate that genes controlling endodermal function in the model plant Arabidopsis thaliana contribute to the plant microbiome assembly. We characterized a regulatory mechanism of endodermal differentiation driven by the microbiota with profound effects on nutrient homeostasis. Furthermore, we demonstrate that this mechanism is linked to the microbiota's capacity to repress responses to the phytohormone abscisic acid in the root. Our findings establish the endodermis as a regulatory hub coordinating microbiota assembly and homeostatic mechanisms.

Green tea catechins and their metabolites in human skin before and after exposure to ultraviolet radiation.

Dietary flavonoids may protect against sunburn inflammation in skin. Preliminary reports using less complete analysis suggest that certain catechins and their metabolites are found in skin biopsies and blister fluid after consumption of green tea; however, it is not known if they are affected by solar-simulated ultraviolet radiation (UVR) or whether conjugated forms, with consequently altered bioactivity, are present. The present study tested the hypothesis that UVR affects the catechin levels in the skin of healthy volunteers after consumption of green tea and how catechins in the plasma are related to their presence in skin tissue samples. In an open oral intervention study, 11 subjects consumed green tea and vitamin C supplements daily for 3months. Presupplementation and postsupplementation plasma samples, suction blister fluid and skin biopsies were collected; the latter two samples were collected both before and after UVR. A sensitive high-performance liquid chromatography/mass spectrometric assay was used to measure the intact catechin metabolites, conjugates and free forms. Seven green tea catechins and their corresponding metabolites were identified postsupplementation in skin biopsies, 20 in blister fluid and 26 in plasma, with 15 green tea catechin metabolites present in both blister fluid and plasma. The valerolactone, O-methyl-M4-O-sulfate, a gut microbiota metabolite of catechins, was significantly increased 1.6-fold by UVR in blister fluid samples. In conclusion, there were some common catechin metabolites in the plasma and blister fluid, and the concentration was always higher in plasma. The results suggest that green tea catechins and metabolites are bioavailable in skin and provide a novel link between catechin metabolites derived from the skin and gut microbiota.

Xanthine oxidase activity in vitro: effects of food extracts and components.

There is significant interest in the direct antioxidant activities of dietary polyphenols, due to associations between consumption of polyphenol-rich foods, such as fruits and vegetables, and decreased incidence of oxidative-stress related disease. However, indirect antioxidant action, such as the inhibition of ROS-producing enzymes, may be equally relevant to health benefits through a general reduction in oxidative stress in vivo. To this end, the effects of food extracts and individual compounds on the in vitro activity of xanthine oxidase (XO) were assessed, many for the first time. Several compounds were shown to be potent inhibitors in vitro, including hesperetin and theaflavin-3,3'-digallate with IC50 values of 39 and 49 microM, respectively. Of the extracts, cranberry juice, purple grape juice, and black tea were the most potent, with IC50 values of 2.4, 3.5, and 5.8% of extracts, respectively. Some samples were shown to promote XO activity over the concentration ranges tested, including orange juice and pink grapefruit juice. Certain "inhibitors", such as purple grape juice and black tea, promoted XO activity at low concentration. The possible role of dietary inhibitors of XO in reducing oxidative stress in vivo is discussed.

A randomized controlled trial of green tea catechins in protection against ultraviolet radiation-induced cutaneous inflammation.

BACKGROUND: Safe systemic protection from the health hazards of ultraviolet radiation (UVR) in sunlight is desirable. Green tea is consumed globally and is reported to have anti-inflammatory properties, which may be mediated through the impact on cyclooxygenase and lipoxygenase pathways. Recent data suggest that green tea catechins (GTCs) reduce acute UVR effects, but human trials examining their photoprotective potential are scarce. OBJECTIVE: We performed a double-blind, randomized, placebo-controlled trial to examine whether GTCs protect against clinical, histologic, and biochemical indicators of UVR-induced inflammation. DESIGN: Healthy adults (aged 18-65 y, phototypes I-II) were randomly allocated to 1350 mg encapsulated green tea extract (540 mg GTC) with 50 mg vitamin C or placebo twice daily for 3 mo. Impact on skin erythema, dermal leukocytic infiltration, and concentrations of proinflammatory eicosanoids was assessed after solar-simulated UVR challenge, and subject compliance was determined through assay of urinary GTC metabolite epigallocatechin glucuronide. RESULTS: Volunteers were assigned to the active (n = 25) or the placebo (n = 25) group. After supplementation, median (IQR) sunburn threshold (minimal erythema dose) was 28 (20-28) and 20 (20-28) mJ/cm(2) in the active and placebo groups, respectively (nonsignificant), with no difference in AUC analysis for measured erythema index after a geometric series of 10 UVR doses. Skin immunohistochemistry showed increased neutrophil and CD3(+) T-lymphocyte numbers post-UVR in both groups (P < 0.01) with no statistically significant differences between groups after supplementation. Cyclooxygenase and lipoxygenase metabolites prostaglandin E2 (vasodilator) and 12-hydroxyeicosatetraenoicacid (chemoattractant), respectively, increased after UVR (P < 0.05), with no differences between supplementation groups. CONCLUSION: Oral GTC (1080 mg/d) with vitamin C over 3 mo did not significantly reduce skin erythema, leukocyte infiltration, or eicosanoid response to UVR inflammatory challenge. This trial was registered at clinicaltrials.gov as NCT01032031.

Gastrointestinal absorption and metabolism of hesperetin-7-O-rutinoside and hesperetin-7-O-glucoside in healthy humans.

SCOPE: Hesperetin-7-O-rutinoside (hesperidin) reduces blood pressure in healthy volunteers but its intestinal absorption and metabolism are not fully understood. Therefore, we aimed to determine sites of absorption and metabolism of dietary flavanone glycosides in humans. METHODS AND RESULTS: Using a single-blind, randomized crossover design, we perfused equimolar amounts of hesperetin-7-O-rutinoside and hesperetin-7-O-glucoside directly into the proximal jejunum of healthy volunteers. We assessed the appearance of metabolites in the perfusate, blood and urine, to determine the sites of metabolism and excretion, and compared this to oral administration. The glucoside was rapidly hydrolyzed by brush border enzymes without any contribution from pancreatic, stomach, or other secreted enzymes, or from bacterial enzymes. Only ∼3% of the dose was recovered intact in the perfusate, indicating high absorption. A proportion was effluxed directly back into the perfused segment mainly in the form of hesperetin-3'-O-sulfate. In contrast, very little hydrolysis or absorption of hesperetin-7-O-rutinoside was observed with ∼80% recovered in the perfusate, no hesperetin metabolites were detected in blood and only traces were excreted in urine. CONCLUSION: The data elucidate the pathways of metabolism of dietary hesperidin in vivo and will facilitate better design of mechanistic studies both in vivo and in vitro.

Urinary excretion of ginkgolide terpene lactones following acute consumption of Ginkgo biloba extract.

Urinary biomarkers of plant food supplement (PFS) exposure/intake represent an accurate, objective tool for determining PFS consumption in humans with applications ranging from epidemiology to subject compliance in clinical trials. Ginkgo biloba remains one of the worlds most popular PFS, yet few studies have investigated the uptake and metabolism of its primary unique bioactives: the terpene lactones. To this end, we conducted a dual-dose, acute crossover intervention using G. biloba supplements in healthy participants (n = 12). Pooled 24-H urine samples were analyzed by triple quadrupole LC-MS-MS. We observed that bilobalide and ginkgolides A and B were passed into urine intact and in a dose-dependent manner. Low levels of intact ginkgolides C and J were also excreted. To our knowledge, this is the first study to report intact ginkgolide J in urine following oral consumption of ginkgo supplements and is also the first to account for excreted terpene lactones as a proportion of dose.

High performance liquid chromatography tandem mass spectrometry dual extraction method for identification of green tea catechin metabolites excreted in human urine.

The simultaneous analysis of free-form and conjugated flavonoids in the same sample is difficult but necessary to properly estimate their bioavailability. A method was developed to optimise the extraction of both free and conjugated forms of catechins and metabolites in a biological sample following the consumption of green tea. A double-blind randomised controlled trial was performed in which 26 volunteers consumed daily green tea and vitamin C supplements and 24 consumed a placebo for 3 months. Urine was collected for 24h at 4 separate time points (pre- and post-consumption) to confirm compliance to the supplementation and to distinguish between placebo and supplementation consumption. The urine was assessed for both free and conjugated metabolites of green tea using LC-MS(2) analysis, after a combination extraction method, which involved an ethyl acetate extraction followed by an acetonitrile protein precipitation. The combination method resulted in a good recovery of EC-O-sulphate (91±7%), EGC-O-glucuronide (94±6%), EC (95±6%), EGC (111±5%) and ethyl gallate (74±3%). A potential total of 55 catechin metabolites were investigated, and of these, 26 conjugated (with methyl, glucuronide or sulphate groups) and 3 free-form (unconjugated) compounds were identified in urine following green tea consumption. The majority of EC and EGC conjugates significantly increased post-consumption of green tea in comparison to baseline (pre-supplementation) samples. The conjugated metabolites associated with the highest peak areas were O-methyl-EC-O-sulphate and the valerolactones M6/M6'-O-sulphate. In line with previous studies, EC and EGC were only identified as conjugated derivatives, and EGCG and ECG were not found as mono-conjugated or free-forms. In summary, the method reported here provides a good recovery of catechin compounds and is appropriate for use in the assessment of flavonoid bioavailability, particularly for biological tissues that may contain endogenous deconjugating enzymes.

Urinary metabolite profiling identifies novel colonic metabolites and conjugates of phenolics in healthy volunteers.

SCOPE: The colonic metabolism of dietary flavonoids, phenolic acids and their phenolic metabolites is complex and many metabolites and conjugates have not yet been unambiguously identified in humans. METHODS AND RESULTS: Urine samples from nine healthy human volunteers obtained after the ingestion of a puree of five (poly)phenol-rich berry fruits were analysed using LC-Orbitrap MS to provide a preliminary indication of possible metabolites based on exact mass. In most cases, the identity of compounds was confirmed using standards produced either chemically or enzymically followed by analysis using LC-triple quadrupole MS. Sulphated, glucuronidated and methylated forms of catechol, pyrogallol and protocatechuic acid mostly appeared in urine after 8 h, suggesting colonic metabolism. Gallic acid and (-)-epicatechin conjugates appeared mainly before 4 h, indicative of absorption from the small intestine. Conjugates of ferulic, caffeic, and vanillic acid appeared at intermediate times. CONCLUSION: We have positively identified metabolites and conjugates, some novel, in the urine of healthy volunteers after intake of multiple phenolics from a mixed puree from berry fruits, with each being excreted at specific and signature times. Some of these compounds could potentially be used as biomarkers of fruit intake. The possible biological activities of these colonic metabolites require further assessment.

Controlled flax interventions for the improvement of menopausal symptoms and postmenopausal bone health: a systematic review.

Concerns regarding hormone therapy safety have led to interest in the use of phytoestrogens for a variety of menopause-related health complaints. Recent meta-analyses concerning soy and postmenopausal bone mineral density, flax and serum cholesterol indicate that significant benefits may be achieved in postmenopausal women. This study aimed to systematically review controlled flax interventions that had reported on menopausal symptoms and bone health in perimenopausal/postmenopausal women. A general search strategy was used to interrogate the Cochrane Library, Embase, MEDLINE, and SciFinder databases. Of 64 initial articles retrieved, we included 11 distinct interventions using flax without cotreatment. Interventions considering hot flush frequency/severity (five studies) and menopausal index scores (five studies) reported improvements from baseline with both flax and control treatments, with no significant difference between groups. There was little evidence to suggest that flax consumption alters circulating sex hormones, but flaxseed intervention increased the urinary 2α-hydroxyestrone/16α-hydroxyestrone ratio, which has been associated with a lower risk of breast cancer. Few studies considered bone mineral density (two studies) or markers of bone turnover (three studies). Flaxseed is currently not indicated for the alleviation of vasomotor symptoms in postmenopausal women. A paucity of appropriate randomized controlled trials means that the effects of flax intervention on postmenopausal bone mineral density are inconclusive.

Analysis of phenolic compounds in Portuguese wild and commercial berries after multienzyme hydrolysis.

Berry fruits are a good source of phenolic compounds and thus, potentially beneficial to health. Phenolic compounds are mainly present as a variety of conjugated forms, either with sugars via O-glycosidic bonds or with other polyols as esters. This chemodiversity makes characterization and identification highly demanding. Selected varieties of commercial blueberries, raspberries and blackberries and the two wild berries Portuguese crowberry and strawberry tree fruits were characterized for individual phenolic content by liquid chromatography-diode array detection and mass spectrometry (HPLC-DAD-MS) after hydrolysis by a novel combination of the fungal glycosidases hesperidinase and cellulase. This approach is shown to be a simple alternative to other existing methods for analysis of plant phenolic compound aglycones. The hydrolysis of glycosides and organic acid esters is efficient and less aggressive than acid and alkaline hydrolysis. This method is able to disclose new sources of dietary phenolic compounds, and the potential usefulness of Portuguese crowberry and strawberry tree fruit is herein demonstrated.

Epigallocatechin-3-gallate inhibits lactase but is alleviated by salivary proline-rich proteins.

Lactase phlorizin hydrolase is a small intestinal brush border enzyme that catalyzes the hydrolysis of the milk sugar, lactose, and also many flavonoid glucosides. We demonstrate that epigallocatechin-3-gallate (EGCG), the principal flavonoid from green tea, inhibits in vitro hydrolysis of lactose by intestinal lactase. We then tested the hypothesis that salivary proline-rich proteins (PRPs) could modulate this inhibition and stabilize EGCG. Inhibition by EGCG of digestive enzymes (α-amylase>chymotrypsin>trypsin>lactase≫pepsin) was alleviated ∼2-6-fold by PRPs. Furthermore, PRPs appeared stable to proteolysis and also stabilized EGCG under digestive conditions in vitro. This is the first report on EGCG inhibition of lactase, and it quantifies the protective role of PRPs against EGCG inhibition of digestive enzymes.

Review of the efficacy of green tea, isoflavones and aloe vera supplements based on randomised controlled trials.

We assess the evidence for health benefits of three commonly consumed plant food supplements (PFS), green tea, isoflavone and aloe vera, based on published systematic reviews of randomised controlled trials (RCTs). Whilst the potential benefits of green tea have been reported in a wide range of health areas, it is only in the area of the metabolic syndrome that the number of RCTs is approaching sufficient to judge such efficacy. Isoflavone supplements are widely used, and RCTs indicate that they affect bone resorption at lower doses in postmenopausal women undergoing estrogen-related bone loss, but this is only translated to attenuation of bone loss at higher doses of isoflavones. A systematic review on RCTs concluded that the effects of isoflavones on hot flashes in postmenopausal women were highly variable and no conclusions could be drawn. Despite the popularity of aloe vera as a PFS, the evaluation of its efficacy as a coadjuvant therapy for certain metabolic or digestive pathologies remains scarce; it constitutes a typical example of a naturally occurring ingredient whose efficacy in topical applications presupposes its efficacy in systemic applications. Nevertheless, its possible toxic effects on oral consumption call for caution in its utility as a PFS. Since 2007, efficacy evaluation of PFS in Europe has been covered by European Union Nutrition and Health Claims legislation. The European Food Safety Authority has adopted an approach relying on RCTs, while medicinal effects are accepted based on traditional use. In general, there are insufficient RCTs for claims to be made, and conclusive results on PFS should be obtained in the future by conducting studies with more homogeneous populations, by using supplements with optimised and measured bioavailability, and by conducting larger RCTs.