Does timing of phytonutrient intake influence the suppression of postprandial oxidative stress? A systematic literature review

BACKGROUND: Postprandial oxidative stress markers in blood are generated transiently from various tissues and cells following high-fat and/or high-carbohydrate (HFHC) meals, and may be suppressed by certain phytonutrients, such as polyphenols and carotenoids. However, the transient presence of phytonutrients in circulation suggests that timing of consumption, relative to the meal, could be important. This systematic review investigates the effect of timing of phytonutrient intake on blood markers of postprandial oxidative processes. METHOD: EMBASE, Medline, Scopus and Web of Science were searched up to December 2020. Eligible studies met the criteria: 1) healthy human adults; 2) phytonutrient(s) consumed in solid form within 24 h of a HFHC meal; 3) postprandial measurements of oxidative stress or antioxidants in blood; and 4) controlled study design. Cohen's d effect sizes were calculated to compare studies. RESULTS: Nine studies, involving 256 participants, were included. Phytonutrients were consumed either at the same time, 1 h before, or the day (>12 h) before a HFHC meal. Significant decreases in blood markers - plasma lipid hydroperoxides, plasma malondialdehyde, serum sNox2-dp, serum 8-iso-PGF2α, platelet p47(phox) phosphorylation, and Keap-1 and p47(phox) protein levels in mononuclear cells (MNCs) - were observed where the phytonutrient was consumed together with the challenge meal (n = 4). Lack of any effect on oxidative stress markers was observed where phytonutrients were consumed with (n = 1), 1 h before (n = 1), and the day before (n = 2) the HFHC meal. CONCLUSION: Phytonutrients consumed with a HFHC meal significantly suppressed some markers of oxidative stress in blood. Although there were only a limited number of studies, it appears that suppression appeared effective at the time of peak phytonutrient concentration in plasma. However, further studies are required to confirm the observations and systematically optimise the effect of timing

Transport rates of dietary phytochemicals in cell monolayers is inversely correlated with absorption kinetics in humans

Dietary phytochemicals promote health and reduce the risk of chronic disease. The Phytochemical Absorption Prediction Model (PCAP) predicts the time required for phytochemicals to reach maximal plasma concentrations (Tmax) in humans based on their lipophilicity and molecular mass. Cell-based transport models have been used to quantify transport rate and efficiency of pharmaceuticals and phytochemicals, however these parameters have not previously been related to the human absorption Tmax. Caco-2/HT29-MTX-E12 monolayers were used to characterise transport of phytochemical standards and extracts and to establish a relationship between the in vitro permeability (Papp) of standards and their in vivo Tmax predicted from the PCAP model. Lipophilic compounds transported through the cell monolayer at relatively faster rates (higher Papp) than hydrophilic compounds, whilst having slower predicted in vivo absorption rates (longer Tmax). The results infer differences between in vitro (cell monolayer) and in vivo (human gastrointestinal tract) absorption kinetics of phytochemicals

Statistical modelling coupled with LC-MS analysis to predict human upper intestinal absorption of phytochemical mixtures

A diet rich in phytochemicals confers benefits for health by reducing the risk of chronic diseases via regulation of oxidative stress and inflammation (OSI). For optimal protective bio-efficacy, the time required for phytochemicals and their metabolites to reach maximal plasma concentrations (Tmax) should be synchronised with the time of increased OSI. A statistical model has been reported to predict Tmax of individual phytochemicals based on molecular mass and lipophilicity. We report the application of the model for predicting the absorption profile of an uncharacterised phytochemical mixture, herein referred to as the ‘functional fingerprint’. First, chemical profiles of phytochemical extracts were acquired using liquid chromatography mass spectrometry (LC-MS), then the molecular features for respective components were used to predict their plasma absorption maximum, based on molecular mass and lipophilicity. This method of ‘functional fingerprinting’ of plant extracts represents a novel tool for understanding and optimising the health efficacy of plant extracts

Regulation of milk protein solubility by a whey-derived proline-rich peptide product

The effects of a bovine whey peptide product enriched in proline (wPRP) on the solubility of milk proteins were tested under ambient conditions or following heat treatment at 75 and 100Â °C, for 1 and 15Â min, followed by post-incubation storage at either ambient temperature or 4Â °C for up to 7Â d. wPRP promoted solubilisation of milk proteins in a concentration-dependent manner without heat treatment and also after heat treatment at 75 and 100Â °C, and the effect was enhanced after storage under either ambient or refrigerated storage conditions. Interactions of wPRP and milk proteins were monitored by particle size analysis and tryptic digestion and specifically linked with solubilisation of αS1 casein (αS1-Cn), which supported observed changes in milk protein solubility. The results suggested that wPRP preferably prevented or reversed physical versus covalent protein aggregation, with the relaxation of hydrophobic interactions at 4Â °C providing an additive effect. This application of wPRP represents a novel approach to stabilisation of dairy proteins following thermal processing with industrial usefulness yet to be explored. Copyright © Proprietors of Journal of Dairy Research 2013Â

Dietary Phytochemicals Promote Health by Enhancing Antioxidant Defence in a Pig Model

Phytochemical-rich diets are protective against chronic diseases and mediate their protective effect by regulation of oxidative stress (OS). However, it is proposed that under some circumstances, phytochemicals can promote production of reactive oxygen species (ROS) in vitro, which might drive OS-mediated signalling. Here, we investigated the effects of administering single doses of extracts of red cabbage and grape skin to pigs. Blood samples taken at baseline and 30 min intervals for 4 hours following intake were analyzed by measures of antioxidant status in plasma, including Trolox equivalent antioxidant capacity (TEAC) and glutathione peroxidase (GPx) activity. In addition, dose-dependent production of hydrogen peroxide (H2O2) by the same extracts was measured in untreated commercial pig plasma in vitro. Plasma from treated pigs showed extract dose-dependent increases in non-enzymatic (plasma TEAC) and enzymatic (GPx) antioxidant capacities. Similarly, extract dose-dependent increases in H2O2 were observed in commercial pig plasma in vitro. The antioxidant responses to extracts by treated pigs were highly correlated with their respective yields of H2O2 production in vitro. These results support that dietary phytochemicals regulate OS via direct and indirect antioxidant mechanisms. The latter may be attributed to the ability to produce H2O2 and to thereby stimulate cellular antioxidant defence systems