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Addition of Milk Does Not Alter the Antioxidant Activity of Black Tea

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Abstract

Tea is a polyphenol-rich beverage like wine and catechins are its chief polyphenols. Catechins have cardio-protective effects as they can scavenge free radicals and inhibit lipid peroxidation. Epidemiological studies indicate an inverse relation between tea consumption and the risk of cardiovascular and other chronic diseases. Addition of milk to black tea has been reported to adversely affect its beneficial effects, but the data are not unequivocal. Therefore, we assessed the effect of the addition of milk to black tea on its ability to modulate oxidative stress and antioxidant status in adult male human volunteers. Although the area under the curve of plasma catechins was lower on the consumption of tea with milk compared to black tea, it did not affect the beneficial effects of black tea on total plasma antioxidant activity, plasma resistance to oxidation induced ex vivo, and decreased plasma and urinary thiobarbituric acid reactive substance levels. The results suggest that addition of milk may not obviate the ability of black tea to modulate the antioxidant status of subjects and that consumption of black tea with/without milk prevents oxidative damage in vivo.

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... Nilgiri, by contrast, is situated in the mountains of the southernmost tea-growing region, Tamil Nadu state in India. The Nilgiri (Blue Hill) mountains feature high altitude ridges that boast lush forests and jungles where tea plants thrive (22)(23)(24)(25)(26)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50). ...
... Harmful effects of tea overconsumption (black or green) are due to three main factors: (1) its caffeine content, (2) the presence of aluminum, and (3) the effects of tea polyphenols on iron bioavailability (13)(14)(15)(16)(17)(18)(19)(20)36). Green tea should not be taken by patients suffering from heart conditions or major cardiovascular problems (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55). Pregnant and breastfeeding women should drink no more than one or two cups per day, because caffeine can cause an increase in heart rhythm (13-20, 26-36, 55). ...
... Pregnant and breastfeeding women should drink no more than one or two cups per day, because caffeine can cause an increase in heart rhythm (13-20, 26-36, 55). It is also important to control the concomitant consumption of green tea and some drugs, due to caffeine's diuretic effects (13)(14)(15)(16)(17)(18)(19)(20)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55). Some studies revealed the capacity of tea plants to accumulate high levels of aluminum (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55). ...
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This review of literature paper highlights about tea (Camellia sinensis) phytochemistry, health benefits and toxicity. Assam state is the largest tea-growing region in India and is home to India's indigenous, wild-growing tea plant variety, Camillia sinensis Assamica. Indian tea is very famous throughout the world and known for famous Assam tea, Darjeeling tea, Niligiri tea, Kodagu or Coorg tea, Chikkamagalore organic tea, Baba Budan hills tea, Kangra tea, Sikkim tea, and Mannar tea. The plant Camellia sinensis variety: Assamica or sinensis is the source of different teas (black, green, white, yellow, and oolong) consumed worldwide, which are classified by the oxidation degree of their bioactive compounds. Thus, teas are classified according to their processing, where the main variation occurs in the degree of oxidation that modifies chemical and sensory characteristics (aroma, color and flavour). Green tea and black tea are processed differently during manufacturing from Camellia sinensis, variety: Assamica or sinensis. Teas became more than simply pleasing and cultural hot drinks. Teas have prevailed for their laxative, hypoglycemic, antioxidant, anti-inflammatory, neuroprotective, anticarcinogenic, anti-obesity, cardiovascular and liver protection properties, especially when consumed through functional foods or food supplements in a limited quantity. However, consumption of large amounts of black or green tea may cause nutritional health problems because of the strong binding activities of tea polyphenols and the caffeine content. However, drinking even a very high dietary amount of black tea or green tea would be unlikely to cause these adverse effects in humans. Addition of milk to tea can decrease or completely inhibit tea antioxidant properties. Epigallo-catechin gallate (EGCG) is an important biochemical marker of Assam state, Northeast Indian tea as it contributes 50% of total catechins. Good quality organic tea rich in melatonin content, if consumed in the right quantity can have major positive effects on the body. This review paper updates about the achievements of Indian tea industry in the international market, and growing demand for organic tea.
... The IC 50 value of 7.5 ± 0.5 μM for MEPCA indicates that it is a potent antioxidant, even at low micromolar concentrations. Blood concentrations of dietary polyphenols are typically between 0.3 and 10 μM (Reddy et al., 2005;Scalbert and Williamson, 2000;Sugisawa and Umegaki, 2002;van het Hof et al., 1998;Yamamoto et al., 2003;Yang et al., 1998), so MEPCA shows significant antioxidant effects at biologically relevant concentrations. Table 1 summarizes the results obtained for each of the polyphenol compounds evaluated using this DNA damage assay (all gel electrophoresis results are provided in Figs. ...
... Since MEPCA was the only polyphenol compound to prevent NP CuOmediated DNA damage at blood polyphenol concentrations (0.3-10 μM (Reddy et al., 2005;Scalbert and Williamson, 2000;Sugisawa and Umegaki, 2002;van het Hof et al., 1998;Yamamoto et al., 2003;Yang et al., 1998); MEPCA IC 50 = 7.5 μM), we tested this polyphenol as well as its gallol analog, MEGA, for their ability to inhibit NP CuO/H 2 O 2 -mediated L929 cell death (Tables S18 and S19 and Figs. S21 and S22 in the Supplementary Material, respectively). ...
... Plasmid DNA damage assays evaluate both antioxidant and prooxidant polyphenol activity, and both behaviors were observed in these studies. The catechol-containing MEPCA is the most effective polyphenol for prevention of NP CuO-mediated DNA damage, with an IC 50 value within the physiological range of blood polyphenol concentrations (0.3-10 μM) (Reddy et al., 2005;Sugisawa and Umegaki, 2002;van het Hof et al., 1998;Yamamoto et al., 2003;Yang et al., 1998). Catecholcontaining polyphenols more effectively prevent DNA damage than their gallol analogs. ...
Article
The ability of ten polyphenolic antioxidants to prevent CuO nanoparticle (NPCuO) and H2O2-mediated DNA damage and cytotoxicity was investigated. Five of the polyphenols (MEPCA, PREGA, MEGA, ECG, and EGCG) prevent NPCuO/H2O2-mediated DNA damage (IC50 values of 7.5–800 μM), three have no effect (PCA, VA, and EC), and two (GA and EGC) result in increased DNA damage. Most polyphenols had similar antioxidant/prooxidant activity in the presence of NPCuO or free copper ions. Electron paramagnetic resonance (EPR) spectroscopy of reactive oxygen species (ROS) generated by NPCuO/H2O2 in the presence of representative polyphenols correlate with results of DNA damage studies: in the presence of NPCuO/H2O2, MEPCA prevents ROS formation, VA has no effect on ROS levels, and EGC increases ROS levels. EPR results with CuO nanoparticles washed to remove dissolved copper in solution (wCuO) in the presence of H2O2/ascorbate suggest that MEPCA prevents ROS formation on the nanoparticle surface in addition to preventing ROS formation from dissolved copper. In mouse fibroblast (L929) cells, combining NPCuO with H2O2 results in significantly greater cytotoxicity than observed for either component alone. After 3 h incubation with MEPCA or MEGA, the viability loss in L929 cells induced by NPCuO/H2O2 challenge was significantly rescued at physiologically relevant polyphenol levels (1 μM). These studies show that polyphenols can protect DNA and inhibit cytotoxicity generated by NPCuO under oxidative stress conditions.
... The reduction of phenolics absorption in the presence of milk is in agreement with Reddy et al. [43] and Serafini et al. [21], who reported that the peak concentrations of plasma flavan-3-ols were significantly lower after consumption of black tea with milk, milk chocolate, and chocolate with milk. However, other studies have failed to show significant differences in plasma concentrations of epicatechin [44], total catechins [45], flavonols [18], and TAC [20,46] after ingestion of chocolate and tea with milk. ...
... In other studies in which chocolate was utilized as the antioxidant source, Schroeter et al. [44] and Serafini et al. [21] reached opposite conclusions, utilizing different proportions of milk lipids: 3% in the former, with no effect of milk, and 30% in the latter, with a clear inhibitory effect [47]. It is a matter of fact that the discrepancy of the results in humans is remarkable, with half the reports suggesting a lack of effect [18,20,[43][44][45][46] and the other half suggesting an inhibitory effect of milk [15,17,19,21]. ...
... Thus, a decreased fat content of milk lowers the amount of fat soluble antioxidants in milk and consequently lowers the total antioxidant property of the milk (Ryan and Petit 2010). Some studies report no negative effect on the plasma antioxidant activity of black tea after adding whole milk (Reddy et al. 2005; Hollman et al. 2001; Leenen et al. 2000), whereas others report a negative effect (Hertog et al. 1997; Tewari et al. 2000; Kartsova and Alekseeva 2008). In comparison, most of the studies on the effect of low-fat milk on tea show a decrease (although to a different extent) in both the antioxidant activity of tea-infused milk and the bioavailability of tea antioxidants in vitro or in vivo (Moser et al. 2014; Egert et al. 2013; Xie et al. 2013; Dubeau et al. 2010; Ryan and Sutherland 2011; Ryan and Petit 2010; Lorenz et al. 2009; Lorenz et al. 2007). ...
... Reports have shown weak to non-existent effects of milk addition to tea (Hollman et al. 2001; Leenen et al. 2000; van het Hof et al. 1998; Kyle et al. 2007; Reddy et al. 2005), but less in number than reports of negative effects. As mentioned before, milk is an inherently good source of antioxidants, thus addition of milk should increase the total antioxidant potential of a tea-milk beverage in the absence of any synergistic of confounding effects. ...
Article
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Tea consumption is practiced as a tradition and has shown potential to improve human health. Maximal uptake of tea antioxidants and milk proteins without a negative impact on tea flavor is highly desired by consumers. There is conflicting evidence for the effect of milk addition to tea on antioxidant activity. Differences in the type of tea, the composition, type and amount of milk, preparation method of tea-milk infusions, the assays used to measure antioxidant activity, and sampling size likely account for the different findings. Interactions between tea polyphenols and milk proteins, especially between catechins and caseins, could account for a decrease in antioxidant activity, although other mechanisms are also possible given the similar effect between soy and bovine milk. The role of milk fat globules and the milk fat globule membrane surface is also important when considering interactions and loss of polyphenolic antioxidant activity, which has not been addressed in the literature.
... However, the ability of tea flavan-3-ols to bind non-specifically with proteins is also well known Kanakis et al., 2011;Soares, Mateus, & Freitas, 2007). Proteinflavan-3-ol interaction has demonstrated the ability to modulate biological activity (He, Lv, & Yao, 2006;Lorenz et al., 2007, Lorenz, Stangl, & Stangl, 2009Tagliazucchi, Verzelloni, & Conte, 2005), bioaccessibility (Green, Murphy, Schulz, Watkins, & Ferruzzi, 2007;Xie, Kosinska, Xu, & Andlauer, in press) and potentially bioavailability of flavan-3-ols (Reddy, Sagar, Sreeramulu, Venu, & Raghunath, 2005;Serafini et al., 2003Serafini et al., , 2009. ...
... Previous studies have shown that the addition of milk to polyphenol-rich foods impacts flavan-3-ol bioaccessibility and bioavailability (Green et al., 2007;Reddy et al., 2005;Serafini et al., 2003Serafini et al., , 2009Xie et al., in press). While this effect is typically attributed to the presence of milk protein, milk minerals may have an impact on both polyphenol and protein structure and stability. ...
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While the impact of interactions between flavan-3-ol and protein on food quality has been reported, the ability of these interactions to modify flavan-3-ol bioavailability remains unclear. The objectives of this study were to characterize the influence of milk proteins and mineral components of the milk matrix on in vitro bioaccessibility of green tea flavan-3-ols and to assess the relative impact of protein digestibility in the GI tract on protein-flavan3-ol binding. Protein solutions containing sodium-caseinate (S-CSN, 35.6 mg/mL), alpha-lactalbumin (alpha-LA, 1 mg/mL), p-lactoglobulin (beta-LG, 3.5 mg/mL), or non-fat dry milk (NFDM) were prepared in Jenness Koops (JK) buffer containing milk salts and formulated at 10-40% (v/v) into green tea beverages containing 0.6 mg/mL total flavan-3-ols. Samples were subjected to a three-stage in vitro digestion to assess flavan-3-ol digestive release and stability (bioaccessibility). Milk protein, most notably S-CSN, significantly decreased (p <0.05) bioaccessibility of flavan-3-ols relative to JK buffer controls (10 relative to 32%). Interestingly, the presence of milk minerals significantly increased (p < 0.05) flavan-3-ol bioaccessibility compared to that of controls (32 relative to 18%). These data combined with SDS-PAGE and fluorometric analyses suggest that both milk proteins and minerals may alter flavan-3-ol bioaccessibility, but normal GI digestion appears to minimize the impact of specific protein interactions. (C) 2014 Published by Elsevier Ltd.
... However, the data are still equivocal. The addition of milk to tea has been reported to inhibit the plasma antioxidant activity in humans [43], whereas other researchers observed that adding milk to tea did not alter the plasma antioxidant activity in humans [44,45]. Reddy et al. [44] found lower levels of plasma catechins (i.e., polyphenol in tea) after participants consumed tea with milk compared to tea only. ...
... The addition of milk to tea has been reported to inhibit the plasma antioxidant activity in humans [43], whereas other researchers observed that adding milk to tea did not alter the plasma antioxidant activity in humans [44,45]. Reddy et al. [44] found lower levels of plasma catechins (i.e., polyphenol in tea) after participants consumed tea with milk compared to tea only. However, van het Hof et al. [46] observed that milk had no effect on plasma levels of catechins, and they concluded that milk does not affect the bioavailability of catechins. ...
Article
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Blueberry consumption has been shown to have various health benefits in humans. However, little is known about the effect of blueberry consumption on blood pressure, endothelial function and insulin sensitivity in humans. The present study investigated the role of blueberry consumption on modifying blood pressure in subjects with metabolic syndrome. In addition, endothelial function and insulin sensitivity (secondary measurements) were also assessed. A double-blind and placebo-controlled study was conducted in 44 adults (blueberry, n = 23; and placebo, n = 21). They were randomized to receive a blueberry or placebo smoothie twice daily for six weeks. Twenty-four-hour ambulatory blood pressure, endothelial function and insulin sensitivity were assessed pre- and post-intervention. The blood pressure and insulin sensitivity did not differ between the blueberry and placebo groups. However, the mean change in resting endothelial function, expressed as reactive hyperemia index (RHI), was improved significantly more in the group consuming the blueberries versus the placebo group (p = 0.024). Even after adjusting for confounding factors, i.e., the percent body fat and gender, the blueberry group still had a greater improvement in endothelial function when compared to their counterpart (RHI; 0.32 ± 0.13 versus -0.33 ± 0.14; p = 0.0023). In conclusion, daily dietary consumption of blueberries did not improve blood pressure, but improved (i.e., increased) endothelial function over six weeks in subjects with metabolic syndrome.
... It decreased plasma and urinary thiobarbituric acid reactive substance levels. The results suggested that the addition of milk may not obviate the ability of black tea to modulate the antioxidant status of subjects and that consumption of black tea with/without milk prevents oxidative damage in vivo (Reddy et al., 2005). In another study, eighteen healthy volunteers consumed two out of four supplements for three days: black tea, black tea with milk, green tea, and water. ...
... 29 The degree and quantity of penetration of a herbal drug, or its active ingredients, is determined by its bioavailability. 30,31 Bioavailability can depend on the chemical complexity of an herb, due to the synergistic and antagonistic actions of its constituents, in promoting absorption. A drug's hydrophobic properties determine its ability to cross the luminal wall, as do the gut microflora, patients' liver function, and the chemical modifications made by the herbal constituents. ...
Article
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Traditional Indian medicine (ayurveda) is becoming increasingly popular, with many chronic conditions responding to it well. Most patients begin to take conventional medications as soon as their diagnoses are made, so ayurvedic treatments are usually undergone alongside and/or after conventional medical approaches. A detailed knowledge of the action of food, spices, and medicinal plants is needed in order to understand their potential influence fully. While societal use of ayurvedic plants and Indian spices is commonplace, without ill effect, the use of more concentrated products made from single plants, often in the form of teas or tablets, is of more concern. The mechanisms by which polyherbal drugs and their extracts act differ in many respects from the actions of single substances or synthetic drugs. Despite the fact that ayurvedic medicines are based on natural herbal materials, their safety depends on their method of administration, taking into account individuals’ needs and their specific disease conditions.
... They came to the conclusion that after 24 h, the amount of chlorogenic acid adsorbed was lower in those who consumed coffee with milk. However, contrary to the mentioned results, Reddy et al. (2005) analysed the effect of the addition of milk on the health-promoting properties of black tea, and as it turned out, the presence of milk proteins, according to these authors, did not cause changes in the antioxidant capacity of phenolic compounds in the blood serum of people involved in the research. Moreover, according to the studies conducted by Roura et al. (2007), interaction with milk proteins does not affect the bioavailability of the phenolic compounds present in cocoa. ...
Article
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Interactions between the different compounds present in foods are common and have influence on the nutritional and functional properties of food products. Among a wide range of these interactions, the formation of complexes between proteins and phenolic compounds seems to be the most important issue. Complexation of the phenolic compounds with proteins can be analysed considering several aspects. These complexes might strongly affect nutritional potential of polyphenols by masking their antioxidant capacity, and on the other hand might have influence on the structure of proteins which may cause their precipitation or decrease susceptibility to digestion. The complexity of protein–phenolic compound interactions is a challenge for food analysts and forced researchers to establish a wide range of analytical methods, allowing determination of complexes formation. The main aim of this review is to give researchers an overview of the currently used methods that can be applied to study the interactions between proteins and phenolic compounds.
... Normal effects of tea in protecting against cardiovascular disease get blocked by the addition of milk because casein from the milk binds to the molecules in the tea that cause the arteries to get relaxed, particularly EGCG (Lorenz et al., 2007). Other studies have found no significant effect of milk on the observed increase in total plasma antioxidant activity (Reddy et al., 2005). Previous studies have observed a beneficial effect of black tea, which was not attributable to the catechin content (Widlansky et al., 2005). ...
... Regarding the food matrix, the smoothies in Stull et al.'s [25,31] study contained milk and yogurt and there is controversy about whether the proteins in milk interact with polyphenols and negate their antioxidant capacity and bioavailability. However, there are still discrepancies between studies [33][34][35][36][37]. It is important to note that the milk contained in the blueberry smoothie did not mask the beneficial effects of the blueberries on improving insulin sensitivity and endothelial function [25,31]. ...
Article
Full-text available
Blueberries are a rich source of polyphenols, which include anthocyanin bioactive compounds. Epidemiological evidence indicates that incorporating blueberries into the diet may lower the risk of developing type 2 diabetes (T2DM). These findings are supported by pre-clinical and clinical studies that have shown improvements in insulin resistance (i.e., increased insulin sensitivity) after obese and insulin-resistant rodents or humans consumed blueberries. Insulin resistance was assessed by homeostatic model assessment-estimated insulin resistance (HOMA-IR), insulin tolerance tests, and hyperinsulinemic-euglycemic clamps. Additionally, the improvements in glucose tolerance after blueberry consumption were assessed by glucose tolerance tests. However, firm conclusions regarding the anti-diabetic effect of blueberries cannot be drawn due to the small number of existing clinical studies. Although the current evidence is promising, more long-term, randomized, and placebo-controlled trials are needed to establish the role of blueberries in preventing or delaying T2DM.
... Alternatively some studies have shown that the addition of milk to tea inhibits its antioxidant activity whereas other workers have reported that the addition of milk does not alter the antioxidant activity of polyphenols in tea, coffee, or cocoa beverages (Richelle, Tavazzi, & Offord, 2001;Serafini, Ghiselli, & Ferro-Luzzi, 1996). Lower levels of plasma catechins have also been reported after drinking tea with milk compared to black tea (Reddy, Vidya Sagar, Sreeramulu, Venu, & Raghunath, 2005). In contrast, other workers have reported that milk had no effect on plasma levels of catechins (Van het Hof, Kivits, Weststrate, & Tijburg, 1998). ...
... This protein binds to the polyphenols present in cocoa, depending on the environment in which it is found. It has been previously shown that adding milk to black tea did not affect the antioxidant capacity (Reddy et al., 2005). Furthermore, Arts et al. (2002) demonstrated through the interaction between flavonoids and proteins with the TEAC test that this relationship between them negatively affects the antioxidant capacity, reducing it both in products and in vivo. ...
Article
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Oxidative stress is associated with the pathogenesis of several chronic diseases. Cocoa is a food rich in polyphenols, with high antioxidant properties, and is an important food in its fight. However, most polyphenols have low solubility, which impairs their biological action. Therefore, encapsulation through the spray drying technique can significantly improve these parameters by generating a protective layer using proteins and polysaccharides. Therefore, the objective of this work was to elaborate a cocoa-based product encapsulated with maltodextrin (CM) or goat milk whey (CW) and to evaluate the total phenolic compounds and their antioxidant capacity, as well as the particle size of the encapsulated product. Cocoa-based products were encapsulated using maltodextrin DE20 or goat whey using a B-290 mini spray dryer (Büchi Labortechnik, Flawil, Switzerland) in a 1:1 weight ratio. Subsequently, the antioxidant capacity was analyzed by the 2,2'-azino-bis (3-ethylbenzoatiazoline-6-sulfonic acid) (ABTS) method and total phenolic compounds using the phenol reagent Folin-Ciocalteu by spectrophotometry, as well as the size of the particle. The CW obtained a higher yield (33.11%) when compared to the CM (24.03%) in the spray dryer. Most of the particles (90%) present in the CM and CS had a size of 21.92 and 21.12 µM, respectively. CW had a higher content of phenolic compounds compared to CM (CM: 536 ± 8.0 vs. CW: 818 ± 77.0 mg GAE/100g dw, p = 0.05). No significant difference was observed in antioxidant capacity between samples (CM: 545 ± 26.0 vs. CW: 478 ± 18.0 µmol TE/100g dw, p = 0.114). The results showed that although CS has a higher content of phenolic compounds, both had the same antioxidant capacity.
... This kind of association may not only decrease the antioxidant properties of catechins, but also affect the nutritional value of dairy products along with possible changes to the physical characteristics and flavour (Han et al. 2011a(Han et al. , 2011bGiroux et al. 2013). However, some scientists have commented that such interactions might not negatively affect the bioavailability of catechins or milk protein in the human body (Hollman et al. 2001;Reddy et al. 2005;Roura et al. 2007), and some even believe that associations between catechins and milk proteins can be considered as a positive effect by which catechins might enhance the functionality or bioavailability of milk proteins (Dubeau et al. 2010;Xie et al. 2013;Haratifar & Corredig 2013). ...
Article
Due to their well-known health benefits, green tea catechins have received recent attention as natural additives in foods such as dairy products. However, they may present some irreversible associations with milk components (e.g. protein and milk fat globules). To investigate the behaviour of two important green tea catechins, (+)-catechin (C) and (-)-epigallocatechin gallate (EGCG), in a standard whole milk system under the conditions of cheesemaking, 250 and 500 ppm of each catechin were added to whole milk (3.3% fat). Although both C and EGCG at either concentration increased both total phenolic content and total antioxidant capacity of the subnatants obtained from the milk system, there was a less linear increase when the concentration of the catechins was doubled, whereas C or EGCG were recovered (measured by HPLC) differently. Overall, these results suggest a degree of associations between green tea catechins with milk proteins and milk fat.
... In one study, the addition of milk to black tea did not appear to have a major impact on various plasma parameters (AUC, Cmax, Tmax, or T1/2), compared with black tea alone, 171 whereas in another study, a 20% reduction in AUC was found. However, plasma concentrations were only monitored for 3 hours, 172 and the milk may have delayed peak absorption to some extent. Mixed effects or only small reductions in bioavailability were also found for coffee polyphenols when consumed with coffee and milk or dairy creamer. ...
Article
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While many epidemiological studies have associated the consumption of polyphenols within fruits and vegetables with a decreased risk of developing several chronic diseases, intervention studies have generally not confirmed these beneficial effects. The reasons for this discrepancy are not fully understood but include potential differences in dosing, interaction with the food matrix, and differences in polyphenol bioavailability. In addition to endogenous factors such as microbiota and digestive enzymes, the food matrix can also considerably affect bioaccessibility, uptake, and further metabolism of polyphenols. While dietary fiber (such as hemicellulose), divalent minerals, and viscous and protein-rich meals are likely to cause detrimental effects on polyphenol bioaccessibility, digestible carbohydrates, dietary lipids (especially for hydrophobic polyphenols, e.g., curcumin), and additional antioxidants may enhance polyphenol availability. Following epithelial uptake, polyphenols such as flavonoids may reduce phase II metabolism and excretion, enhancing polyphenol bioavailability. Furthermore, polyphenols may act synergistically due to their influence on efflux transporters such as p-glycoprotein. In order to understand polyphenol bioactivity, increased knowledge of the factors affecting polyphenol bioavailability, including dietary factors, is paramount.
... Evidence on the contrary showed a slightly larger study of 21 healthy volunteers found that addition of milk into tea did not affect its antioxidant properties (Leenen et al., 2000). Other studies (n = 9 and n = 18) also found that addition of milk into tea did not affect its antioxidant power (Hollman et al., 2001;Reddy et al., 2005). Therefore, it can be tentatively concluded that the addition of milk is unlikely to decrease tea antioxidant power. ...
Article
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Tea has been widely consumed around the world for thousands of years and drinking tea is a daily habit for people of all ages. Tea is a major source of flavanoids, which have become well known as antioxidants. Tea also contains caffeine and theanine, which have been found to associate with health benefits. Many animal and epidemiological studies have been conducted to investigate the link between tea consumption and human health. However, common questions that arise about tea consumption include: whether all teas are the same, why drinking tea is linked with health benefits, how do the different ways of tea preparation impact on availability of tea components, how much and how long a person should consume tea to obtain health benefits, and whether there is any negative health effect associated with drinking tea. To answer these questions, this paper outlines the tea components and their link to human health, discusses major factors affecting availability of tea components in a tea cup, and reviews the latest epidemiological evidence linking tea consumption to human health.
... For instance, black tea, which is rich in catechins, is of particular interest, since the addition of milk is common practice. From a health standpoint, there is conflicting evidence concerning whether bioavailability of phenolics is reduced, enhanced, or unaffected by complexation with milk proteins (Reddy et al., 2005, Lorenz et al., 2007. With respect to shelf-life and preventing oxidation in complex food systems, the effect of complexation between food components may be beneficial. ...
... Egert et al. [7] showed negative effects on the bioavailability of gallated catechins for caseinate, milk, and soy proteins, whilst the non-gallated forms were unaffected. Others have described a null-effect of milk on bioavailability for total plasma tea catechins or antioxidant capacity [8,9]. Accordingly, bioavailability of (epi)catechin in a milk chocolate drink was reported not to be substantially affected [10]. ...
Article
Polyphenols, a complex group of secondary plant metabolites, including flavonoids and phenolic acids, have been studied in depth for their health-related benefits. The activity of polyphenols may, however, be hampered when consumed together with protein-rich food products, due to the interaction between polyphenols and proteins. To that end we have tested the bioavailability of representatives of a range of polyphenol classes when consumed for five days in different beverage matrices. In a placebo-controlled, randomized, cross-over study, 35 healthy males received either six placebo gelatine capsules consumed with 200 mL of water, six capsules with 800 mg polyphenols derived from red wine and grape extracts, or the same dose of polyphenols incorporated into 200 mL of either pasteurized dairy drink, soy drink (both containing 3.4% proteins) or fruit-flavoured protein-free drink . At the end of the intervention urine and blood was collected and analysed for a broad range of phenolic compounds using Gas Chromatography–Mass Spectrometry (GC-MS), Liquid Chromatography–Multiple Reaction Monitoring–Mass Spectrometry (LC-MRM-MS), and Nuclear Magnetic Resonance (NMR) spectroscopy techniques. The plasma and urine concentrations of the polyphenols identified increased with all formats, including the protein-rich beverages. Compared to capsule ingestion, consumption of polyphenol-rich beverages containing either dairy, soy or no proteins had minor to no effect on the bioavailability and excretion of phenolic compounds in plasma (118% ± 9%) and urine (98% ± 2%). We conclude that intake of polyphenols incorporated in protein-rich drinks does not have a major impact on the bioavailability of a range of different polyphenols and phenolic metabolites.
... However, the obtained results are contradictory. Some of them have reported an inhibitory effect, while others have shown no significant effect of adding milk [22][23][24] . Milk fat exists in emulsified form coated by thin layer known as a globule membrane 25 , and its effect on antioxidant activity and bioavailability of coffee polyphenols is unclear until now. ...
Article
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Polyphenols have been widely studied and considered as a health promotingand disease preventive agents in humans. Several studies investigated the antioxidantproperties of polyphenols and their abilities to eliminate free radicals. In this study, theantioxidant activity of coffee in the presence of different types of cows’ milk at differentconcentrations, 10% or 20%, was investigated. Our results showed that milk could eitherenhance the scavenging of DPPH or decrease the metal chelating and metal reducingactivity of polyphenol. However, more investigations are required to evaluate themechanisms by which fats in milk can alter the antioxidant activity of coffee.
... In a study by Rashidinejad et al. (2015), the addition of catechin in cheese increased the total phenolic compounds concentration in in vitro digestion during 90 days, also, catechin treatments presented higher antioxidant activity (FRAP, ORAC) through time and this activity increased as the concentration of catechin increased. On the other hand, Reddy et al. (2005) evaluated the in vivo effect (human) of consumption of green tea (catechins) added with milk. The results showed that catechins were present in plasma after the consumption and this reduced the plasma and urinary TBARS values. ...
Chapter
Global food production is affected by microbiological and oxidative factors, resulting in raising food waste. In order to reduce the incidence of these factors, food industry use synthetic additives, but this trend is declining due to their association with different diseases. Thus, the food industry is searching for safe and innovative alternatives for consumers, taking into account the consumer preference toward healthy and natural additives. This issue gives a real prospection for using natural additives in food such as plants additives that contain a variety of bioactive secondary metabolites. Also, their activity of prolonging shelf life of foods has been demonstrated by several authors, which reduces the impact of microbiological and oxidative factors. Likewise, these compounds showed other functional and interesting properties such as nutrient supplement, colorant, flavor, sweeteners, and texturizer.
... Animal studies have concluded that "daily intake of green tea catechins / extract efficiently protects the penumbra from irreversible damage due to cerebral ischemia, reduced the formation of post ischemic brain edema and infarct volume and consequent neurological deficits" (Hong et al. 2000;Lee et al. 2004;Suzuki et al. 2004). The observational epidemiological research in humans is strongly supportive of the hypothesis that tea consumption, at the level of e"3 cups per day, either as green or black tea, reduces the risk of occurrence of stroke, stroke volume, and mortality from stroke (Delavar et al. 2008;Liang et al. 2009;Reddy et al. 2005). ...
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Tea is the most widely consumed human beverage and rich in flavonoids, which causes significant endothelium dependent vasodilatation. Aims are to study the effect of tea drinking in subjects with ischemic stroke and metabolic syndromes. A total of 1100 stroke patients were selected from indoor/ outdoor department of Ramakrishna Mission Seva Pratisthan and other Hospitals of Kolkata from last three years. Individuals between 40 to 80 years of age were recruited. Clinical and biochemical examination were conducted in each case at the onset and every 6 months interval. Individuals stable on existing medications were advised to continue the same unless situation demands dose modification or withdrawal. Methods of tea preparation were detailed to study participants and they were asked to take ≥3 cups (each cup contains 150 ml of tea /day. Out of 1100 participants, 787 were men and 313 were women and the mean age was 61.62±11.02. Tea drinkers constituted 95.09% of total study individuals. At second follow up, 773 subjects were regular in attendance and 9 died. The most preferred type of tea ingested was decoction (53.64%). Significant (p< 0.001) decrements were noticed in systolic blood pressure, Body Mass Index (BMI), fasting blood glucose and Low Density Lipoprotein (LDL) level when compared between base line and consecutive visits. Tea consumption of 450 ml or more (≥3cups)/day was associated with reduction of the incidence of recurrent ischemic stroke, significant decrement of systolic blood pressure, better control of fasting hyperglycemia, and lowering down of the level of total cholesterol and Low Density Lipoprotein level in subjects with hypercholesterolemia. Further investigations are needed to corroborate our observations.
... The three components of milk can be selected as the most practical photochemically important components: (1) the proteins are related to the activated flavor of light-exposed milk; (2) the lipids are related to the other oxidized flavor; and (3) various antioxidants in milk are photoehemically changed, damaging nutritional quality (31). Reddy et al. (32) indicated that the addition of anthocyanin-rich black tea to milk could prevent oxidative damage. Hence, we found that the level of TAC in the light-protected groups was unchanged (P > 0.05; Table 2), suggesting that anthocyanins add antioxidant activity to milk, which could protect milk from light oxidation. ...
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The aim of this study was to observe the effect of purple corn anthocyanin on the light-induced antioxidant activity, free radicals, volatile compounds, color parameters, and sensory properties of milk during storage. There were four groups: (1) negative control, no addition of anthocyanins + exposure to fluorescent light (NC); (2) positive control 1, no addition of anthocyanins + protected from fluorescent light (PC1); (3) positive control 2, the addition of 0.3% (w/v) anthocyanins + exposure to fluorescent light (PC2); and (4) the addition of 0.3% anthocyanins + protected from fluorescent light (AC). The results indicated that the concentration of antioxidant activity parameters in the NC group decreased during the entire storage period, whereas antioxidant activity parameters were unchanged except for the glutathione peroxidase (GSH-Px) in the AC group. Moreover, the NC group showed lower levels of 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity and higher levels of superoxide anion and hydrogen peroxide than the other groups after 1 d of storage period. The extent of malondialdehyde accumulation and lipid peroxidation in the control groups were greater than that of the AC group. Twenty-two volatile compounds were determined in milk, which consisted of eight alcohols, three ketones, five aldehydes, two esters, and four hydrocarbons by headspace gas chromatography mass spectrometer analysis. Specifically, individual aldehydes, esters and hydrocarbons in the AC group remained at relatively stable values during storage relative to the other three groups. Stronger positive correlations were detected between several antioxidant activities (superoxide dismutase, GSH-Px) and DPPH scavenging activity as well as total ketones in milk. Adding of anthocyanin did not impact on the color values of L*, a* and b* in light-protected milk during the entire storage period. Some sensory evaluation parameters (flat, garlic/onion/weedy, oxidized-light, oxidized-metal, rancid) in AC group were significantly higher than that of the control group at the end of the period. In conclusion, the current study revealed that the addition of purple corn anthocyanin pigment to light-protected milk had the potential to prevent lipid oxidation, enhance antioxidant activity, maintain volatile compounds and increase the sensory scores.
... An increased absorption of flavonols (quercetin and kaempferol) was observed in healthy adult males after ingestion of black tea and this increase was not significantly different from that after the ingestion of black tea with milk (31). In another in vivo study it was reported that the area under curve of plasma catechins was lower after black tea consumption (7 g of tea solids) with milk compared to black tea alone (57). However, this did not affect the TAC values in plasma (FRAP assay). ...
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Milk contains a wide array of compounds with established or putative pro— or anti—oxidant function. The functions of these compounds have been intensively studied. This review focusses on some important aspects in this wide field namely the methodology for measurement of the total antioxidant capacity (TAC), the content of TAC and some related compounds in human and animal milks and infant formulas, and the effect of milk intake on antioxidant status in the body and on the activity of dietary flavonoids as studied in vitro and in vivo. Regarding methodology TAC in milk can be measured by spectrophotometric and electrochemical methods and some of their characteristics are reviewed. Milk, whey, high—molecular—weight and low—molecular—weight (LMW) fractions of whey have all been found to have antioxidant capacity using these techniques. The major antioxidant in the LMW fraction has been identified as urate. An extensive literature survey was made regarding data on the antioxidant capacity and related variables of milk obtained from different sources (human milk, infant formulas and animal milk) and subjected to different treatments. Differences in TAC between milks from different sources have been observed but due to the variety of techniques used no clear pattern is evident at present. Another important aspect is the putative effects of the intake of milk products on the antioxidant status of the consumer. A few studies performed in adults and premature infants are reviewed and it is stated that too little information is available to make any firm conclusions in this regard. Finally, a high interest has been devoted to the possible interference of milk with the antioxidant properties of flavonoid—rich food like tea. Most in vitro studies show an inhibition by milk on tea flavonoid activity whereas the results from the corresponding in vivo studies are equivocal. Our general conclusion is that several compounds in various milk fractions contribute to the antioxidant capacity of milk and that much further work is needed to unravel the complex interactions among the pro— and antioxidants, and their putative health effects on the consumer.
... The researchers concluded that there were some possible interactions between coffee phenolics and milk proteins, but these had no significant effect on the bioavailability of CGA in the rats (Duarte and Farah 2011). Besides coffee, some other studies also revealed an insignificant change in the antioxidant capacity of tea (Kyle et al. 2007;Leenen et al. 2000;Reddy et al. 2005) and blackberry juice (Hassimotto et al. 2008), when treated with milk addition. It should also be noted that all these changes are dose-dependent, meaning that based on the concentration of the phenolics and/or proteins in a coffeemilk beverage system, the results obtained may change from a negative effect to a neutral (insignificant change) or even positive effect. ...
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To date, there exists a debate on the effect of milk added to coffee infusions/beverages concerning the nutritional quality of coffee and the functional properties of its phenolic compounds. Yet, the full nutritional quality and functional properties of a coffee beverage without a significant negative impact on its sensorial profile are highly desired by the consumers. Negative/masking, positive, and neutral effects of milk on the antioxidant activity and bioavailability of coffee phenolics (particularly, chlorogenic acids) have been reported. Some potential factors including the type and amount of milk added, type of coffee beverage, the composition of both milk (protein and fat) and coffee (phenolic compounds), preparation method, assays used to measure antioxidant properties, and sampling size may account for the various reported findings. Interactions between phenolic compounds in coffee and milk proteins could account as the main responsible aspect for the reported masking/negative impact of milk on the antioxidant activity and bioaccessibility/bioavailability of coffee bioactives. However, considering the interactions between milk components and coffee phenolics, which result in the loss of their functionality, the role of milk fat globules and the milk fat globule membrane can also be crucial, but this has not been addressed in the literature so far. • Highlights • In most cases, milk is added to the coffee beverages in several various ways. • Effect of milk on the nutritional/functional properties of coffee is controversial. • Enough evidence suggests negative effects of milk addition on properties of coffee. • Interactions of coffee phenolics and milk proteins could account as the main aspect. • The role of milk fat globules and milk fat globule membrane may also be crucial.
... Normal effects of tea in protecting against cardiovascular disease get blocked by the addition of milk because casein from the milk binds to the molecules in the tea that cause the arteries to get relaxed, particularly EGCG (Lorenz et al., 2007). Other studies have found no significant effect of milk on the observed increase in total plasma antioxidant activity (Reddy et al., 2005). Previous studies have observed a beneficial effect of black tea, which was not attributable to the catechin content (Widlansky et al., 2005). ...
Article
Tea is the second most frequently consumed cheapest non-alcoholic beverage worldwide, black tea is the most produced type, followed by green and Oolong tea. The venture of this paper is to focus on the latest research efforts regarding the health effects related to consumption of black tea and derive some future research directions towards its therapeutic potentialities. With a view of the above, comprehensive information on the fermentation process, composition, and quality of black tea has been provided. Several major beneficial roles of black tea are antioxidant activity, antiulcer effect, anti-inflammatory effect, antimicrobial properties, anticancer properties, antimutagenic activity along with the attenuating or reducing effects on blood pressure, CHD and cardiovascular disease, atherosclerosis, oxidative damage are important. Moreover, black tea has proven to enhance insulin activity, helps in treating asthma, retard cataract, maintains fluid balance, bone health and dental health, improves mean body mass index and body weight, prevents cellular DNA damage, inhibits HIV, lowers stress hormone levels, etc. The potential effect on human biosynthetic pathways related to oxidative processes as well as that on cognitive performance has also been discussed with citation from various research findings.
... However, generally, the addition of milk to tea or cocoa has had either no effect or modest effects on absorption or excretion of avan-3-ols. [84][85][86][87][88] However, avan-3-ol mediated vasodilation was impaired in milk-tea beverages relative to tea alone suggesting that milk protein interactions may serve to limit the cardioprotective benets of tea. 78 The extent to which this outcome is due to protein interactions such as those observed by Egert et al. (2013) or may be related to instability of avan-3-ols at elevated pH (>6) of milk based systems is not known. ...
Article
Many of the potential health benefits of flavonoids have been associated with their specific chemical and biological properties including their ability to interact and bind non-covalently to macronutrients in foods. While flavonoid-protein interactions and binding have been the subject of intensive study, significantly less is understood about non-covalent interactions with carbohydrates and lipids. These interactions with macronutrients are likely to impact both the flavonoid properties in foods, such as their radical scavenging activity, and the food or beverage matrix itself, including their taste, texture and other sensorial properties. Overall, non-covalent binding of flavonoids with macronutrients is primarily driven by van der Waals interactions. From the flavonoid perspective, these interactions are modulated by characteristics such as degree of polymerization, molecular flexibility, number of external hydroxyl groups, or number of terminal galloyl groups. From the macronutrient standpoint, electrostatic and ionic interactions are generally predominant with carbohydrates, while hydrophobic interactions are generally predominant with lipids and mainly limited to interactions with flavonols. All of these interactions are involved in flavonoid-protein interactions. While primarily associated with undesirable characteristics in foods and beverages, such as astringency, negative impact on macronutrient digestibility and hazing, more recent efforts have attempted to leverage these interactions to develop controlled delivery systems or strategies to enhance flavonoids bioavailability. This paper aims at reviewing the fundamental bases for non-covalent interactions, their occurrence in food and beverage systems and their impact on the physico-chemical, organoleptic and some nutritional properties of food.
... These studies implied that the influence of proteins on the antioxidant profiles of phenolics critically depends on the types of both molecules involved and the determination systems adopted. In human and animal trials, milk addition to black tea reduced the area under the curve of plasma catechins but did not obviate their ability to modulate oxidative stress and antioxidant status in healthy male adults (Reddy et al. 2005). Similarly, the ingestion of milk and blueberries did not induce differences in plasma markers of lipid oxidation in healthy volunteers (Serafini et al. 2009). ...
Article
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Dietary proteins and phenolic compounds are commonly co-existing components that readily interact with each other to yield complexes in a wide range of food systems. The formed complexes play a critical role in the physiochemical characteristics of both reacting molecules, thereby impacting nutritional and quality profiles of related products. In this review, we provided the most updated knowledge on dietary protein-phenolic interactions related with food science and human nutrition, including their mechanisms of complexation, analytical technologies, and alterations in the functionality and nutraceutical properties of both reacting partners. Their potential applications in the industries regarding stability during food processing and storage, impacts on product quality, and fabrication of novel delivery systems for liable bioactives were also discussed. The interactions between dietary proteins and phenolics, either via non-covalent or covalent processes, are ubiquitous in food systems and are closely associated with chemical structures of both compounds and the surrounding conditions, mainly temperature, pH, and the presence of phenolic oxidases. Albeit in different ways, such intermolecular associations induced changes in protein conformational structures, which subsequently impacted their techno-functional properties, digestibility, and allergenic potentials; in turn, the bioaccessibility/bioavailability and health-protecting features of interacted phenolics were modified to various extents, as noticed by in vitro and in vivo evidence. Largely depending on the interaction molecules and preparation steps, those influences can be either favorable or unfavorable in different systems and therefore can be tailored to develop food products and nutraceuticals with maximized functionality and quality attributes.
... 7 The individual and joint advantages of milk and tea have been documented. [8][9][10][11][12] Despite the antioxidant benefits on skin and oral cancer risk, the disadvantages of vascular protective effects reduction of tea, 13 increased obesity risk, and high caries tendency outweighs them. 14 The beneficial effect of drinking tea also requires a person to drink it every two hours. ...
Article
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Objectives: Public health dentists in the Philippines are being made to treat more patients and do other tasks despite being underpaid. Despite this, there is a dearth of information on burnout and its association with Filipino public-school dentists. Thus, this study aimed to assess the burnout levels and their association with the amount of work and sleep quality. Methods: There were 10 out of 14 dentists from the Caraga Region who responded and answered a self-directed and self-reported online questionnaire composed of 52 questions that gauged sociodemographic data, sources of burnout, level of burnout, lower back pain, and sleep quality. Results: Based on the results of the study, dentists with more than 40, 000 patients (rs=0.81, p=0.005), in charge of more than one municipality (rs=0.67, p=0.035) and more than one school (rs=0.67, p=0.035), and with poor sleep (rs=1, p=0.005) experience more burnout. Conclusion: The level of burnout is high in Filipino public-school dentists. In this study, burnout was associated with dentists who have poor sleep, having to serve more than 40, 000 patients, more than one municipality, and more than one school. The legal bases for oral health and other pertinent memorandum orders from concerned government organizations should be revisited.
... 7 The individual and joint advantages of milk and tea have been documented. [8][9][10][11][12] Despite the antioxidant benefits on skin and oral cancer risk, the disadvantages of vascular protective effects reduction of tea, 13 increased obesity risk, and high caries tendency outweighs them. 14 The beneficial effect of drinking tea also requires a person to drink it every two hours. ...
Article
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Background: Since 1987, data regarding dental caries prevalence in the Philippines has been shown to be over 90%. Objective: This study compared the trends of Filipino web searches regarding toothache and milk tea from 2017 to 2019 through spatio-temporal analyses. Methods: Google Trends searches for the years 2017, 2018, and 2019 were done using three separate search queries using the parameters “toothache” (TA) and “milk tea” (MT) as search terms, Philippines as location, Health as category, and Web Search as database. Results: The outcome showed a decreasing trend in searches for toothache and an increasing interest for milk tea web searches from 2017 to 2019. A multiple comparison test showed that searches for MT were significantly more than TA in 2017 (p<0.001), 2018 (p<0.001), and 2019 (p<0.001). Searches for TA during the 2nd, 3rd, and 4th quarter compared to the 1st quarter of the year, in Caraga, Eastern Visayas, Western Visayas and Zamboanga Peninsula compared to Manila, were found to be significantly high. Conclusion: Filipinos’ health-seeking behavior show decreasing interest towards TA and increasing for MT.
... It was observed that, based on previous work, variations among individuals, tea type, milk type and assessment methods should be considered when evaluating the impact on health of milk addition to tea. Some studies found there was no negative effect on the plasma antioxidant activity of tea with addition of whole milk (Leenen et al. 2000;Hollman et al. 2001;Reddy et al. 2005), whereas others showed a negative effect (Sharma et al. 2008;Ryan and Petit 2010;Ryan and Sutherland 2011). Some studies highlighted the ability of milk proteins to facilitate intestinal transport of some polyphenols in green tea by increasing their absorption (Xie et al. 2013). ...
... The addition of bovine, soy or rice milk to tea samples increased the in vitro recovery of total tea catechins, whilst no significant difference was detected in in vivo (in humans) catechin bioavailability of tea samples with or without milk (Green et al., 2007). Similarly, no significant effects of milk proteins on in vivo bioavailability of tea and coffee phenolics were reported (Hollman et al., 2001;Leenen et al., 2000;Reddy et al., 2005;Renouf et al., 2010). In terms of blueberry polyphenols, their interactions with milk proteins led to a lower in vivo antioxidant potential and decreased caffeic acid absorption (Serafini et al., 2009). ...
... 11 Additionally, peak concentrations of plasma flavan-3-ols were significantly lower after healthy male subjects consumed tea with milk than those after consuming black tea alone. 33 The inhibitory effects of milk may be due to interactions among nutrients, and in the present study, the interaction of anthocyanins and milk proteins. Polyphenols can bind to proteins via hydrogen bonding involving polar groups and hydrophobic interactions involving non-polar aro- 43 indicated that hydrophobic interactions accounted for the binding of pelargonidin to β-lactoglobulin. ...
Article
Strawberries are a dietary source of anthocyanins, particularly pelargonidin glycosides. Dietary anthocyanins have received increasing attention among researchers and consumers due to their health benefits. The oral bioavailability of anthocyanins is reported to be low and various dietary factors may influence their oral bioavailability further. Milk is suggested to reduce (poly)phenols’ oral bioavailability. However, the effect of milk on anthocyanin oral bioavailability remains uncertain. Likewise, mixed nutrient meals may influence the oral bioavailability of anthocyanins. Therefore, the purpose of this study was to assess the effect of milk on the oral bioavailability and other pharmacokinetic (PK) variables of strawberry anthocyanins consumed with and without a meal. Nine healthy participants consumed a strawberry beverage prepared in milk or water with a standard meal on two occasions. On two additional occasions, the beverages were given to a subset (n = 4) of participants to determine the impact of the meal on anthocyanin PK variables, including oral bioavailability. Independent of the meal, beverages prepared in milk significantly reduced the peak plasma concentrations (Cmax) of pelargonidin-3-O-glucoside (P-3-G), pelargonidin-glucuronide (PG) and pelargonidin-3-O-rutinoside (P-3-R), as well as the PG and P-3-R area under the curve (AUC) (p < 0.05) compared to beverages prepared in water. Milk did not influence the oral relative bioavailability of pelargonidin anthocyanins under meal conditions; however, the oral relative bioavailability of pelargonidin anthocyanins was reduced by ∼50% by milk under without meal conditions (p < 0.05). Consuming strawberry beverages made with milk and consuming those made with water with and without a meal influenced different aspects of strawberry anthocyanin PKs. The significance of this effect on clinical efficacy requires additional research.
... Similarly, chocolate polyphenols have been reported to pose a higher total antioxidant capacity in vivo compared to milk chocolate or dark chocolate ingested with milk. [121] On the contrary, some researchers claimed that the addition of milk to green tea [122] or black tea [122,123] did not lead any differences in plasma antioxidant activity. ...
Article
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The biological activity and techno-functional properties of phenolic compounds has gained great importance due to the epidemiologically-proved health benefits. Use of polyphenols as fortification agents for functional food production and nanotechnological approaches using natural vehicles for polyphenol delivery have been recently discussed. In this respect, milk proteins and dairy products represent unique characteristics for polyphenol studies. The conflicting results on the functionality of polyphenols interacting with milk proteins either in model systems or in complex dairy matrices reveal the need of future studies.
Article
Flavonoids are polyphenolic compounds produced by plants and delivered to the human body through food. Although the epidemiological analyses of large human populations did not reveal a simple correlation between flavonoid consumption and health, laboratory investigations and clinical trials clearly demonstrate the effectiveness of flavonoids in the prevention of cardiovascular, carcinogenic, neurodegenerative and immune diseases, as well as other diseases. At present, the abilities of flavonoids in the regulation of cell metabolism, gene expression, and protection against oxidative stress are well-known, although certain biophysical aspects of their functioning are not yet clear. Most flavonoids are poorly soluble in water and, similar to lipophilic compounds, have a tendency to accumulate in biological membranes, particularly in lipid rafts, where they can interact with different receptors and signal transducers and influence their functioning through modulation of the lipid-phase behavior. In this study, we discuss the enhancement in the lipophilicity and antioxidative activity of flavonoids after their complexation with transient metal cations. We hypothesize that flavonoid-metal complexes are involved in the formation of molecular assemblies due to the facilitation of membrane adhesion and fusion, protein-protein and protein-membrane binding, and other processes responsible for the regulation of cell metabolism and protection against environmental hazards.
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Antioxidant consumption can increase through strategic food choices. Acorns could contribute to those strategic choices. We surveyed antioxidant content in a variety of acorns from the southeastern United States. The phenolic content of Quercus velutina prior to leaching was 39.4±3.6 mg GAE/g and of Quercus alba was 27.4±.3 mg GAE/g. After 5 leaching stages, the phenolic content of Q. velutina was 12.3±.8 mg GAE/g and of Q. alba was 10.8±.7 mg GAE/g. After milling, the phenolic value for Q. velutina was 39.9±4.5 mg GAE/g and for Q. alba was 6.6±.1 mg GAE/g. A spice cookie made with all-purpose wheat flour contained 2.7±.1 mg GAE/g. When red oak acorn meal was substituted, the cookie contained 9.6±3.3 mg GAE/g, and when substituted with white oak acorn meal contained 4.2±.4 mg GAE/g. Ingredient interactions influenced the phenolic content. Acorns and acorn products can be a strategic method of increasing polyphenolic intake.
Article
The behaviour of low-fat cheese fortified with catechin in an in vitro gastrointestinal digestive system to investigate the effect of (+)-catechin on total phenolic content (TPC), antioxidant activity (AA), and catechin recovery was studied. Three different concentrations of catechin (125, 250, and 500 ppm) were added to pasteurized skim milk (0.1% fat) and a hard low fat cheese was made. The cheese was cold stored over a 90-day ripening period at 8ºC and the samples were taken on days 0, 30, and 90. For extracting phenolic compounds for chemical analysis, a simulated digestion model contains both gastric and intestinal digestion was employed for digesting the cheese samples for 6 hours. The Folin-Ciocalteu assay was carried out for measuring TPC whereas AA was measured via two different methods including ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC). Catechin addition enhanced TPC besides AA in cheese samples during 90-day ripening period significantly (p<0.01). Both FRAP and ORAC showed a high degree of correlation with TPC where the correlation between ORAC and TPC was higher than the correlation between FRAP and TPC. Therefore, ORAC could be the most suitable technique for estimating AA in cheese samples and dairy products. The in vitro recovery of catechin after 90-day storage was 60.7, 62.8, and 75.2 % for 125, 250, and 500 ppm catechin-treated cheeses, respectively.
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The aim of our study was to determine whether milk diminished the staining effects of Turkish and imported black tea with or without chlorhexidine. Human incisor teeth (n = 36) were incubated with 18 different preparations of steeped or infused black tea plus saliva with or without milk and/or chlorhexidine. Enamel staining was measured using a colorimeter before and after exposure. Independent of the type of tea, the inclusion of milk changed the tooth color toward blue on the yellow–blue spectrum (p < 0.001) and toward black on the black–white spectrum (p < 0.001). The inclusion of chlorhexidine changed the tooth color toward white on the black–white spectrum (p < 0.01) and toward yellow on the yellow–blue spectrum (p < 0.001). The inclusion of both milk and chlorhexidine caused a yellow color difference (Δb*= 0.244); this change was reduced with the addition of chlorhexidine only (Δb* = 0.8224). Tea plus chlorhexidine exerted a substantial color change. Milk reduces the staining caused by tea, and the color change induced by the addition of milk can be interpreted as optical white. Milk also neutralizes some of the yellow staining caused by chlorhexidine.
Article
Published data of the last decade on the chemical analysis and related problems of investigation of phenolic antioxidants as components of complex biomedical and food objects are generalized. The physicochemical properties of these compounds are presented in accordance with the up-to-date classification of their structures. Particular attention is paid to the development of new and advancement of traditional methods for determination of natural phenolic antioxidants in relation to public health protection problems. The interdisciplinary character of the considered problems is emphasized and the ways for problem solution are outlined.
Chapter
This chapter presents the important tea-growing areas, the manufacture of different types of tea (green, white, oolong, and black), and the chemical constituents of tea. Flavonoids and other polyphenols are the most important constituents of tea, the foremost being catechins (flavanols), which are the most abundant flavanoids in fresh tea leaves. The conversion of catechins to theaflavins and thearubigins during the manufacture of oolong and black teas, and the chemistry of other flavonoids, such as flavonol and flavone glycosides, proanthocyanidins, and bisflavanols, are presented. Data on the content of these compounds are given and concepts for the differentiation of different types of tea (e.g., green and black tea) and the detection of geographic origin are discussed. The chemistry of non-flavonoids in tea, such as alkaloids, carotenoids, minerals, amino acids (especially l-theanine), carbohydrates, lipids, and volatiles/aroma compounds, is discussed. The brewing of tea and tea products (decaffeinated and instant teas, tea-based ready-to-drink beverages) is explained. The potential health benefits (e.g., anticancer effects, protection against cardiovascular heart disease) of tea and its constituents, foremost tea flavonoids, are described. This chapter includes a section on the bioavailability and metabolism of tea constituents. State-of-the-art analytical methods for the determination of selected tea constituents are listed.
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Green tea polyphenols (GTP) have been widely tested for their effects on several metabolic syndromes and degenerative diseases such as cancer, cardiovascular diseases, and diabetes. The present study was formulated to assess the physiological efficacy of green tea polyphenol infused with milk (GTPM) on skin integrity in correlation with antioxidative status in healthy adults. Forty-four healthy voluntary subjects were recruited and assigned to two groups, who drank 240 ml of mineral water mixed with either an experimental (GTPM) or placebo package (2 packs per day) for the following 6 months. The experimental group then switched to the placebo package, and vice versa, for a further 6 months, with one month of washout period in between. During the initial, 3(rd), 6(th), 10(th), and 13(th) month anthropometric measurements were performed and fasting blood samples were withdrawn for various biochemical assays. Skin examination was performed at the initial, 6(th) and 13(th) month. No significant alterations were observed in any of the anthropometric measurements. Administration of GTPM significantly increased (p < 0.05) the antioxidant index and antioxidant enzyme activities when compared with the placebo group, whereas a concomitant decrease in the levels of lipid peroxidation were noted. Moreover, GTPM intake notably improved skin integrity and texture by markedly lowering (p < 0.05) skin wrinkles and roughness in elderly subjects. GTPM proved to be an effective antioxidant by lowering oxidative stress and thereby ameliorating skin texture and integrity.
Chapter
Cacao products such as chocolate and cocoa are major food sources of polyphenolic compounds in the form of monomeric catechins and oligomeric procyanidins. These compounds display a myriad of health-related properties that are only realized after they have transited through the digestive tract, interacted with the intestinal microflora, undergone presystemic biotransformations, and become absorbed from the intestinal milieu.
Chapter
In vitro digestion models permit the characterization of cocoa procyanidins during digestion under physiological conditions, caused by alimentary enzymes. Cultured cell models facilitate studies of small intestinal absorption and metabolism, as an important step towards elucidating the potential impact of these cocoa procyanidins on human health. Characterization of the digestive species of cocoa procyanidins forming as consequence of colonic fermentation provides useful information for future studies in vivo. The in vitro digestion models could act as a first directional influence on the reformulation of new cocoa products in order to achieve the required “nutrient profiles.”
Chapter
Although there are many studies reporting the potential health benefits of the diverse bioactive compounds present in our diet, many aspects related to their bioavailability and bioaccessibility, and particularly their metabolism, have been poorly investigated. In order to exert an effect in the body, a compound should be able to reach the target site of action at concentrations that will trigger the expected response. When considering the potential beneficial effects of bioactive food compounds, it is important to take into account the many factors that can have a significant effect on their bioavailability, and consequently can alter the amount of these compounds that will be absorbed and that will ultimately reach the site of action. This chapter focuses on the several means of improving bioavailability that are described in the literature, including bioaccessibility, food matrix, biological transporters, metabolizing enzymes, and molecular interactions.
Chapter
The gut microbiome is defined as the complex ecosystem of microorganisms that live in the gastrointestinal tract of humans and animals; it is composed of bacteria, viruses, fungi, and even archaea, though it primarily consists of bacteria. It plays a vital role in host physiology and metabolism, from immune function to organ development. The gut microbiome has been implicated as a factor in many diseases and has a hand in brain function, behavior, and mental health. Several factors contribute to the composition of the gut microbiome, including host genetics, diet, and environment, with early-life diet seeming to have a more permanent impact than diet later in life. Not only can diet alter an individual’s health through its influence on the gut microbiome, but also it can even impact future generations. This chapter will outline the ways in which specific foods, food groups, and diets impact the human gut microbiome and their subsequent effects on human health.
Chapter
Milk and milk-based foods are nutrient-rich products consumed worldwide. Recently, the incorporation of the encapsulated bioactive food ingredients into milk and dairy foods, as a convenient way of delivery for such ingredients, has received considerable research attention, due to their potential contributions to human nutrition and health. This chapter reviews the opportunities and challenges of incorporation of encapsulated bioactive food ingredients into milk and dairy products. The evidence from the supplementation of these products with encapsulated bioactive compounds and protected bioactive live organisms has been discussed. Although a large body of evidence was found that indicates the possibility of using milk and dairy products as potential carriers for the delivery of bioactive ingredients, it appears that only a few studies have investigated such possibility in reasonable depth. Therefore, future research is required to answer the remaining questions including feasibility, safety, efficacy, and in-vivo bioavailability of the incorporated bioactive ingredients into dairy products.
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Blueberries belong to the genus Vaccinium of the family Ericaceae. A series of epidemiological studies have demonstrated that blueberry polyphenols, particularly blueberry anthocyanins provide significant beneficial effects for humans. However, the findings of clinical studies have been equivocal. Therefore, we sought to assess the potential anti-hypertensive effects of blueberry supplementation through a meta-analysis of available randomized controlled trials (RCTs). A comprehensive literature search of PubMed, The Cochrane Library, AMED (Allied and Complementary Medicine Database), Embase, Web of Science, Wanfang Database, and China National Knowledge Infrastructure were performed to identify potential studies published before June 2015. The standardized mean difference and 95% confidence interval (CI) were used as summary statistics. Net changes in systolic blood pressure (SBP) and diastolic blood pressure (DBP) between the blueberry and placebo groups were calculated by subtracting the values at the end of follow-up from those at baseline. Meta-regression was used to identify potential moderators of effect size. Six RCT studies with 204 participants were included in our meta-analysis. There was no significant effect of blueberry supplementation on changes in blood pressure (BP) relative to baseline, and there was a mean difference of -0.28 (95% CI: -1.11 to 0.56, I(2)=87%) and -0.5 (95% CI: -1.24 to 0.24, I(2)=84%) mmHg for SBP and DBP, respectively. In summary, the results from this meta-analysis do not favor any clinical efficacy of blueberry supplementation in improving BP. Further well-designed larger RCTs are required to verify the association between blueberry supplementation and BP.Journal of Human Hypertension advance online publication, 22 September 2016; doi:10.1038/jhh.2016.70.
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Vegetables are major dietary sources of fibers and antioxidants such as carotenoids, polyphenols and vitamin C which contribute to explain their protective effects against cardiovascular diseases. We investigated in the rat the effects of a 3-week supplementation of the diet with carrot (15% dry matter) on lipid metabolism and antioxidant status. A significant decrease of cholesterol level in liver (-44%; P= 0.0007) was observed together with a reduction of the level of liver triglycerides (-40%; P= 0.0005). Fecal total steroids excretion increased by 30% upon feeding the carrot diet as compared to the control. The secretion of bile acids was maintained, whereas the cholesterol apparent absorption was reduced in rats fed carrot diet. Carrot consumption also improved the antioxidant status. It significantly decreased the urinary excretion of thiobarbituric acid reactive substances (TBARS), reduced the TBARS levels in heart, increased the vitamin E plasmatic level and tended to increase the ferric reducing ability of plasma (FRAP) as compared to the controls. The carrot diet provided carotenoid antioxidants: 5.1 mg beta-carotene, 1.6 mg alpha-carotene and 0.25mg lutein per 100 g diet. No carotenoids were found in plasma whereas the three carotenoids were detected in the plasma of the rats fed the carrot diet at 125, 41, 43 nmol/L respective concentrations. beta-Carotene was also detected in liver and heart. Carrot consumption modifies cholesterol absorption and bile acids excretion and increases antioxidant status and these effects could be interesting for cardiovascular protection.
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Flavonoids, commonly occurring antioxidants in foods, have been compared in a dose-response manner with vitamins C and E and beta-carotene and found to be powerful antioxidants using an in vitro lipoprotein oxidation model. This model simulates the oxidation of low-density lipoproteins, which results in atherosclerosis. Of the flavonoids and flavonoid-related compounds, flavonols found in tea are the most powerful natural antioxidants. These results provide a mechanism for the beneficial epidemiological effect of dietary flavonoids on heart disease.
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The chemistry of tea as a beverage is reviewed in depth, covering both historical and current chemical perspectives. Special attention is given to the polyphenols in tea, although the general composition and properties are also treated. Current trends in tea science, particularly in the area of polyphenol complexation and antioxidant properties, are also covered. The need for a chemically based understanding, rather than one hypothesized from generalized and indirect observation, is stressed.
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To investigate the in vivo and in vitro effects of black tea on the oxidative modification of low density lipoprotein (LDL). The antioxidant activity of the tea was studied in vitro by measuring the resistance of the LDL to oxidative modification in the presence of copper. The effects of tea consumption in vivo were investigated in two settings. Firstly, to assess the acute effects of tea consumption, five fasting healthy subjects ingested 600 mls (50.7+/-5.4 mg flavonoids) of black tea and peripheral venous blood was collected at 0, 30, 60, 90, 120 and 180 min after consumption. Secondly, to assess the effects of chronic tea consumption, a randomised crossover trial of tea (126.8+/-13.5 mg flavonoids) and coffee consumption was carried out in ten healthy subjects. Black tea extract increased the resistance of LDL in vitro in a concentration dependent manner. There was no significant change in total plasma antioxidant capacity or susceptibility of the LDL to oxidation over the 3 h period after consumption of black tea. The four-week crossover study in which coffee was used as a control against the black tea showed no significant difference in the total plasma antioxidant capacity or susceptibility of LDL to oxidation between the tea and coffee groups. Serum lipids, including total cholesterol, triglycerides, LDL cholesterol and HDL cholesterol did not change significantly throughout the study. The consumption of moderate quantities of black tea acutely or for one week does not increase plasma total antioxidant capacity or alter the susceptibility of LDL to oxidation.
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With increasing evidence that shows the involvement of active oxygen and nitrogen species in a variety of disorders, cancer, and aging, the role of antioxidant against oxidative stress has received renewed attention. In this review article, a rationale for design of lipophilic, radical-scavenging antioxidant is presented and the potency of a novel antioxidant, 2,3-dihydro-5-hydroxy-2,2-dipentyl-4,6-di-tert-butylbenzofuran (BO-653), as an inhibitor of LDL oxidation was evaluated by considering various factors such as reactivity toward radicals, localization, and mobility in the lipoprotein, and fate of its radical. The anti-atherogenic activity of BO-653 was compared with those of α-tocopherol, probucol, and its metabolites. Furthermore, a novel function of phenolic antioxidants such as cell regulation and induction of phase II defense antioxidants are also discussed.
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To investigate the association between consumption of green tea and various serum markers in a Japanese population, with special reference to preventive effects of green tea against cardiovascular disease and disorders of the liver. Cross sectional study. Yoshimi, Japan. 1371 men aged over 40 years resident in Yoshimi and surveyed on their living habits including daily consumption of green tea. Their peripheral blood samples were subjected to several biochemical assays. Increased consumption of green tea was associated with decreased serum concentrations of total cholesterol (P for trend < 0.001) and triglyceride (P for trend = 0.02) and an increased proportion of high density lipoprotein cholesterol together with a decreased proportion of low and very low lipoprotein cholesterols (P for trend = 0.02), which resulted in a decreased atherogenic index (P for trend = 0.02). Moreover, increased consumption of green tea, especially more than 10 cups a day, was related to decreased concentrations of hepatological markers in serum, aspartate aminotransferase (P for trend = 0.06), alanine transferase (P for trend = 0.07), and ferritin (P for trend = 0.02). The inverse association between consumption of green tea and various serum markers shows that green tea may act protectively against cardiovascular disease and disorders of the liver.
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Antioxidant flavonols and their major food source, black tea, have been associated with a lower risk of ischemic heart disease (IHD) and stroke in Dutch men. We investigated whether flavonol intake predicted a lower rate of IHD in 1900 Welsh men aged 45-59 y, who were followed up for 14 y. Flavonol intake, mainly from tea to which milk is customarily added, was not related to IHD incidence [relative risk (RR), highest compared with lowest quartile: 1.0; 95% CI: 0.6, 1.6; P for trend = 0.996; n = 186] but was weakly positively related to IHD mortality (RR: 1.6; 95% CI: 0.9, 2.9; P = 0.119; n = 131) and cancer mortality (RR: 1.3; 95% CI: 0.7, 2.3; P = 0.150; n = 104) and strongly related to total mortality (RR: 1.4; 95% CI: 1.0, 2.0; P = 0.014; n = 334). Men with the highest consumption of tea (> 1.2 L, or > 8 cups/d) had an RR of 2.4 (95% CI: 1.5, 3.9) of dying in the follow-up period compared with men consuming < 300 mL/d (< 2 cups/d). We conclude that intake of antioxidant flavonols is not inversely associated with IHD risk in the United Kingdom. Possibly, flavonols from tea to which milk is added are not absorbed; experimental evidence suggests that adding milk to tea abolishes the plasma antioxidant-raising capacity of tea. The apparent association between tea consumption and increased mortality in this population merits further investigation.
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Dietary flavonoid intake has been reported to be inversely associated with the incidence of coronary artery disease. To clarify the possible role of tea flavonoids in the prevention of atherosclerosis, we investigated the effects of tea flavonoids on the susceptibility of low-density lipoprotein (LDL) to oxidative modification. In an in vitro study, catechins or theaflavins (25-400 mumol/L) were added to plasma and incubated for 3 h at 37 degrees C. Then, the LDL fraction was separated by ultracentrifugation. The oxidizability of LDL was estimated by measuring conjugated diene, thiobarbituric acid-reactive substances (TBARS), and lipid peroxides after cupric sulfate was added. TBARS and lipid peroxides in the supernates were also measured after incubation with macrophages. Catechins significantly (P < 0.01 by ANOVA) and dose-dependently prolonged the lag time before initiation of oxidation. Among the catechins, epigallocatechin gallate exerted the most marked effect, prolonging the oxidation lag time more than vitamin E at the same molar concentration. Theaflavins exerted stronger inhibitory effects than catechins. Macrophage-mediated LDL oxidation was also inhibited by adding these tea flavonoids to the plasma samples. In an in vivo study, 14 healthy volunteers consumed 750 mL black tea/d for 4 wk. After the subjects had consumed tea for 4 wk, the lag time before LDL oxidation was significantly (P < 0.01) prolonged from 54 to 62 min. This minor prolongation occurred despite much lower plasma flavonoids than were used in vitro. No significant change was observed in eight control volunteers. LDL exposed to tea flavonoids in vitro or in vivo reduced oxidizability. We speculate that tea flavonoids may have a role in ameliorating atherosclerosis.
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To assess whether consumption of 100 ml of whisky or red wine by healthy male subjects increased plasma total phenol content and antioxidant capacity. A Latin square arrangement to eliminate ordering effects whereby, after an overnight fast, nine volunteers consumed 100 ml of red wine, malt whisky or unmatured 'new make' spirit. Each volunteer participated on three occasions one week apart, consuming one of the beverages each time. Blood samples were obtained from the anticubital vein at intervals up to 4h after consumption of the beverages when a urine sample was also obtained. Within 30 min of consumption of the wine and whisky, there was a similar and significant increase in plasma total phenol content and antioxidant capacity as determined by the ferric reducing capacity of plasma (FRAP). No changes were observed following consumption of 'new make' spirit. Consumption of phenolic-containing alcoholic beverages transiently raises total phenol concentration and enhances the antioxidant capacity of plasma. This is compatible with suggestions that moderate alcohol usage and increased antioxidant intake decrease the risk of coronary heart disease.
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To investigate the effect of black and green tea consumption, with and without milk, on the plasma antioxidant activity in humans. In a complete cross-over design, 21 healthy volunteers (10 male, 11 female) received a single dose of black tea, green tea (2 g tea solids in 300 ml water) or water with or without milk. Blood samples were obtained at baseline and at several time points up to 2 h post-tea drinking. Plasma was analysed for total catechins and antioxidant activity, using the ferric reducing ability of plasma (FRAP) assay. Consumption of black tea resulted in a significant increase in plasma antioxidant activity reaching maximal levels at about 60 min. A larger increase was observed after consumption of green tea. As anticipated from the higher catechin concentration in green tea, the rise in plasma total catechins was significantly higher after consumption of green tea when compared to black tea. Addition of milk to black or green tea did not affect the observed increases in plasma antioxidant activity. Consumption of a single dose of black or green tea induces a significant rise in plasma antioxidant activity in vivo. Addition of milk to tea does not abolish this increase. Whether the observed increases in plasma antioxidant activity after a single dose of tea prevent in vivo oxidative damage remains to be established. European Journal of Clinical Nutrition (2000) 54, 87-92
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Epidemiologic studies suggest that tea consumption may reduce the risk of cardiovascular diseases, but results are inconsistent. Catechins, which belong to the flavonoid family, are the main components of tea and may be responsible for the alleged protective effect. Taking catechin sources other than tea into account might clarify the reported associations. The objective was to evaluate the association between catechin intake and the incidence of and mortality from ischemic heart disease and stroke. We evaluated the effect of a high catechin intake by using data from the Zutphen Elderly Study, a prospective cohort study of 806 men aged 65-84 y at baseline in 1985. The mean (+/-SD) catechin intake at baseline was 72 +/- 47.8 mg, mainly from black tea, apples, and chocolate. A total of 90 deaths from ischemic heart disease were documented. Catechin intake was inversely associated with ischemic heart disease mortality; the multivariate-adjusted risk ratio in the highest tertile of intake was 0.49 (95% CI: 0.27, 0.88; P for trend: 0.017). After multivariate adjustment, catechin intake was not associated with the incidence of myocardial infarction (risk ratio in the highest tertile of intake: 0.70; 95% CI: 0.39, 1.26; P for trend: 0.232). After adjustment for tea consumption and flavonol intake, a 7.5-mg increase in catechin intake from sources other than tea was associated with a tendency for a 20% reduction in ischemic heart disease mortality risk (P = 0.114). There was no association between catechin intake and stroke incidence or mortality. Catechins, whether from tea or other sources, may reduce the risk of ischemic heart disease mortality but not of stroke.
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Prospective studies suggest that tea may protect against cardiovascular disease. A potential mechanism for such an effect involves inhibition of lipid peroxidation by polyphenolic antioxidants derived from tea. Our objective was to determine whether regular ingestion of tea could inhibit in vivo lipid peroxidation. Two controlled intervention studies assessed the effects of regular ingestion of tea on lipid peroxidation determined by measurement of urinary F(2)-isoprostane excretion. Study 1: The effects of 1000 mL/d of green tea and black tea were compared with hot water containing caffeine in 13 subjects with elevated blood pressure using a randomized 3-period (7 d each) crossover design. Study 2: The effects of 1250 mL/d of black tea were compared with hot water in 22 subjects with mildly raised serum total cholesterol concentrations using a randomized 2-period (4 wk each) crossover design. F(2)-isoprostane excretion was not altered after regular ingestion of green tea (273 +/- 48 pmol/mmol creatinine) or black tea (274 +/- 39 pmol/mmol creatinine) in comparison with hot water (263 +/- 47 pmol/mmol creatinine; Study 1), or by regular ingestion of black tea (334 +/- 71 pmol/mmol creatinine) in comparison with hot water (355 +/- 75 pmol/mmol creatinine; Study 2). These results do not support the suggestion that polyphenolic antioxidants derived from tea inhibit in vivo lipid peroxidation.
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The purpose of this study was to investigate the effects of single/double or repeated intake of a normal amount of tea catechin on plasma catechin concentrations and antioxidant activity in young women. First, after an overnight fast, five healthy subjects were given water or single/double dose(s) of tea polyphenol extract (164 mg tea catechins containing 61% epigallocatechin gallate in 190 ml water). Blood samples were taken before and 30, 60 and 180 min after the ingestion. Second, 16 healthy subjects ingested the tea polyphenol extract three times a day at mealtimes for 7 days followed by withdrawal of tea polyphenol extract for 7 days. Blood samples were taken before and after ingestion, and 7 days after the withdrawal of tea catechin. Subjects were prohibited from drinking any beverages containing polyphenols or antioxidant supplements during the study period. Catechin and other antioxidant concentrations in the plasma were measured, and changes in antioxidant activity were evaluated by ferric reducing ability of plasma assay. Single/double ingestion of tea polyphenol extract did not cause an increase in the antioxidant activity. There was no also change in antioxidant activity after the ingestion of tea polyphenol extract for 7 days. Plasma-free epigallocatechin gallate concentration remained at the pre-study level; however, the plasma FRAP value decreased significantly at 7 days after the withdrawal of tea polyphenol extract. Decreases in endogenous antioxidants in the plasma, including vitamin C and bilirubin, were also observed 7 days after withdrawal of tea polyphenol. The results suggest that continuous daily intake of tea catechins affects the concentrations of endogenous antioxidants in the plasma and has the potential to maintain total antioxidant activity.
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Background: Epidemiologic studies suggest that foods rich in flavonoids might reduce the risk of cardiovascular disease. Objective: Our objective was to investigate the effect of intake of flavonoid-containing black currant and apple juice on urinary excretion of quercetin and on markers of oxidative status. Design: This was a crossover study with 3 doses of juice (750, 1000, and 1500 mL) consumed for 1 wk by 4 women and 1 man corresponding to an intake of 4.8, 6.4, and 9.6 mg quercetin/d. Results: Urinary excretion of quercetin increased significantly with dose and with time. The fraction excreted in urine was 0.29–0.47%. Plasma quercetin did not change with juice intervention. Plasma ascorbate increased during intervention because of the ascorbate in the juice. Total plasma malondialdehyde decreased with time during the 1500-mL juice intervention, indicating reduced lipid oxidation in plasma. Plasma 2-amino-adipic semialdehyde residues increased with time and dose, indicating a prooxidant effect of the juice, whereas erythrocyte 2-amino-adipic semialdehyde and γ-glutamyl semialdehyde concentrations, Trolox-equivalent antioxidant capacity, and ferric reducing ability of plasma did not change. Glutathione peroxidase activity increased significantly with juice dose. Conclusions: Urinary excretion of quercetin seemed to be a small but constant function of quercetin intake. Short-term, high intake of black currant and apple juices had a prooxidant effect on plasma proteins and increased glutathione peroxidase activity, whereas lipid oxidation in plasma seemed to decrease. These effects might be related to several components of the juice and cannot be attributed solely to its quercetin content.
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Epidemiologic studies indicated that tea consumption reduces the risk of cardiovascular disease. We assessed the effect of green or black tea consumption on resistance of low-density lipoprotein (LDL) to oxidation ex vivo and on serum lipid concentrations in healthy volunteers. In a 4-wk parallel comparison trial, 45 volunteers consumed 900 mL (6 cups) mineral water, green tea, or black tea/d. Blood samples drawn while subjects were fasting were obtained before and after the study. The effect on resistance of subsequently isolated LDL to oxidation of adding green or black tea extract to plasma was investigated in an in vitro experiment. Consumption of 900 mL (6 cups) green or black tea/d did not affect serum lipid concentrations, resistance of LDL to oxidation, or markers of oxidative damage to lipids in vivo, although consumption of green tea slightly increased total antioxidant activity of plasma. The in vitro experiment showed that resistance of isolated LDL to oxidation increased only after incubation of plasma with very high amounts of green or black tea. These amounts, when converted to tea catechin concentrations, were much higher than those expected in vivo. We conclude that daily consumption of 900 mL (6 cups) green or black tea/d for 4 wk had no effect on serum lipid concentrations or resistance of LDL to oxidation ex vivo. Future research should focus on mechanisms by which tea flavonoids may reduce the risk of cardiovascular disease other than by increasing the intrinsic antioxidant status of LDL.
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Background: Epidemiological studies suggested that consumption of fruit and vegetables may protect against stroke. The hypothesis that dietary antioxidant vitamins and flavonoids account for this observation is investigated in a prospective study. Methods: A cohort of 552 men aged 50 to 69 years was examined in 1970 and followed up for 15 years. Mean nutrient and food intake was calculated from crosscheck dietary histories taken in 1960, 1965, and 1970. The association between antioxidants, selected foods, and stroke incidence was assessed by Cox proportional hazards regression analysis. Adjustment was made for confounding by age, systolic blood pressure, serum cholesterol, cigarette smoking, energy intake, and consumption of fish and alcohol. Results: Forty-two cases of first fatal or nonfatal stroke were documented Dietary flavonoids (mainly quercetin) were inversely associated with stroke incidence after adjustment for potential confounders, including antioxidant vitamins. The relative risk (RR) of the highest vs the lowest quartile of flavonoid intake (greater than or equal to 28.6 mg/d vs <18.3 mg/d) was 0.27 (95% confidence interval [CI], 0.11 to 0.70). A lower stroke risk was also observed for the highest quartile of beta-carotene intake (RR, 0.54; 95% CI, 0.22 to 1.33). The intake of vitamin C and vitamin E was not associated with stroke risk. Black tea contributed about 70% to flavonoid intake. The RR for a daily consumption of 4.7 cups or more of tea vs less than 2.6 cups of tea was 0.31 (95% CI, 0.12 to 0.84). Conclusions: The habitual intake of flavonoids and their major source (tea) may protect against stroke.
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A number of in vitro studies have shown that polyphenols and flavonoids in tea exert significant antioxidant activity. However, epidemiologic and experimental studies have produced conflicting results. The purpose of the present study was to compare the antioxidant activity of black tea in vitro with that ex vivo. Black tea polyphenols (BTP), black tea extract (BTE), or their major polyphenolic antioxidant constituent, epigallocatechin gallate (EGCG), were added to human plasma and lipid peroxidation was induced by the water-soluble radical generator 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH). Following a lag phase, lipid peroxidation was initiated and occurred at a rate that was lowered in a dose-dependent manner by BTP. Similarly, EGCG and BTE added to plasma in vitro strongly inhibited AAPH-induced lipid peroxidation. The lag phase preceding detectable lipid peroxidation was due to the antioxidant activity of endogenous ascorbate, which was more effective at inhibiting lipid peroxidation than the tea polyphenols and was not spared by these compounds. In contrast, when eight healthy volunteers consumed the equivalent of six cups of black tea, the resistance of their plasma to lipid peroxidation ex vivo did not increase over the next 3 h. These data suggest that, despite antioxidant efficacy in vitro, black tea does not protect plasma from lipid peroxidation in vivo. The striking discrepancy between the in vitro and ex vivo data is most likely explained by the insufficient bioavailability of tea polyphenols in humans.
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Epidemiological studies have indicated a protective role of dietary flavonoids in cardiovascular disease, but evidence is still conflicting. Tea is the major dietary source for flavonoids in Western populations. We studied the association of tea intake with aortic atherosclerosis in a general population. The present analysis formed part of the Rotterdam Study, a prospective study of men and women 55 years and older. Dietary intakes were assessed at baseline by a trained dietician who used a semiquantitative food frequency questionnaire. Calcified plaques in the abdominal aorta were radiographically detected after 2 to 3 years of follow-up. Aortic atherosclerosis was classified as "mild," "moderate," or "severe," according to the length of the calcified area (<1 cm, 1-5 cm, and >5 cm, respectively). The association of tea intake with severity of aortic atherosclerosis was studied in 3454 subjects who were free of cardiovascular disease at baseline. Data were analyzed by logistic regression, adjusting for age, sex, body mass index (calculated as weight in kilograms divided by the square of height in meters), smoking, education, and intake of alcohol, coffee, vitamin antioxidants, total fat, and total energy. Multivariable analyses showed a significant, inverse association of tea intake with severe aortic atherosclerosis. Odds ratios decreased from 0.54 (95% confidence interval [CI], 0.32-0.92) for drinking 125 to 250 mL (1-2 cups) of tea to 0.31 (CI, 0.16-0.59) for drinking more than 500 mL/d (4 cups per day). The associations were stronger in women than in men. The association of tea intake with mild and moderate atherosclerosis was not statistically significant. This study indicates a protective effect of tea drinking against ischemic heart disease.
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Spanish strawberries (Fragaria × Ananassa cv. Tudla) with foreseeable high decay were, after harvesting, either left untreated, dipped in water, or dipped in different calcium chloride (CaCl2) solutions at 25 or 45 °C. Subsequently, the fruits were stored at 1°C for 1 day. Their ripening quality parameters were then monitored during a shelf life of 3 days at 18 °C. Dipping the fruits in 1% CaCl2 solution was the most effective treatment for increasing the calcium content of the fruits, for controlling their postharvest decay, and for maintaining their firmness and soluble solids content. The treatments did not affect the sensorial quality of fruits. Keywords: Fragaria × ananassa; ripening; decay; quality
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The relationship between antioxidant activity and antimutagenicity of various tea extracts (green tea, pouchong tea, oolong tea, and black tea) was investigated. All tea extracts exhibited markedly antioxidant activity and reducing power, especially oolong tea, which inhibited 73.6% peroxidation of linoleic acid. Tea extracts exhibited a 65-75% scavenging effect on superoxide at a dose of 1 mg and 30-50% scavenging effect on hydrogen peroxide at a dose of 400 mu g. They scavenged 100% hydroxyl radical at a dosage of 4 mg except the black tea. Tea extracts also showed 50-70% scavenging effect on alpha,alpha-diphenyl-beta-picrylhydrazyl radical. The antioxidant activity and the scavenging effects on active oxygen decreased in the order semifermented tea > nonfermented tea > fermented tea. Tea extracts showed strong antimutagenic action against five indirect mutagens, i.e., AFB(1), Trp-P-1, Glu-P-1, B[a]P, and IQ, especially oolong and pouchong teas. The antioxidant effect of tea extracts was well correlated to their antimutagenicity in some cases but varied with the mutagen and antioxidative properties.
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Electron spin resonance methodology has been used to assess the hydrogen-donating (antioxidant) ability of catechins and extracts of green and black tea to Fremy's radical and galvinoxyl radical in aqueous and organic solutions, respectively. Catechin flavanols accounted for 77–82% of the total antioxidant activity of green tea but only 47–58% of that of black tea. The radical quenching ability of the green tea was 21–24% more effective than that of the black tea in both aqueous and lipophilic systems. Epigallocatechin gallate was the most effective at reducing the two radical species, whereas epigallocatechin was least effective in the galvinoxyl/ethanol system, and catechin least effective in the Fremy's radical/water system. In a model system comprising a mixture of the flavanols in ethanolic or aqueous solution, in the same concentrations as they were present in the tea extracts, the antioxidant potential was a simple summation of the activity of the individual components indicating no synergistic or antagonistic side reactions. Results demonstrate that flavanol components of teas exhibit potent antioxidant activity in both aqueous and organic media. This will be of physiological relevance if such compounds partition into both the aqueous and lipid compartment of cells. © 1998 SCI.
Article
Considerable evidence points to the health benefits of the phytochemical constituents of fruit, vegetables, beverages, and grains in protection against cardiovascular disease and certain cancers. This may be accounted for through contributions from their constituent antioxidants (vitamin E, vitamin C, β-carotene, other carotenoids and the non-nutrient flavonoids, ubiquitous phytochemical components of the diet), as well as through other anticarcinogenic and cardioprotective effects independently of their antioxidant effects. Indeed, the epidemiological evidence for a risk-reducing role of vitamin C for cancer is not as strong as that for fruit and vegetables (1).Dietary components may contribute to antioxidant function in several ways that relate to their structural chemistry (2): i) by directly scavenging free radicals through hydrogen/electron donation, depending on their reducing properties, or reduction potentials; ii) by intercepting the propagatory chain reactions of lipid peroxidation and scavengin...
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The reaction of lipid peroxides in animal tissues with thiobarbituric acid was dependent on pH of the reaction mixture as was the case for linoleic acid hydroperoxide. The optimum pH was found to be 3.5. Taking this fact into consideration, a standard procedure for the assay of lipid peroxide level in animal tissues by their reaction with thiobarbituric acid was developed as follows. Ten percent ( tissue homogenate was mixed with sodium dodecyl sulfate, acetate buffer (pH 3.5), and aqueous solution of thiobarbituric acid. After heating at 95°C for 60 min, the red pigment produced was extracted with n-butanol-pyridine mixture and estimated by the absorbance at 532nm. As an external standard, tetramethoxy-propane was used, and lipid peroxide level was expressed in terms of nmol malondialdehyde. Using this method, the liped peroxide level in the liver of rats suffering from carbon tetrachloride intoxication was investigated. The results were in good agreement with previously reported data obtained by measuring diene content.
Article
Background and methods: The relation of tea to cholesterol, systolic blood pressure, and mortality from coronary heart disease and all causes was studied in 9,856 men and 10,233 women without history of cardiovascular disease or diabetes. All men and women 35-49 years of age from the county of Oppland (Norway) were invited to participate; the attendance rate was 90%. Results: Mean serum cholesterol decreased with increasing tea consumption, the linear trend coefficient corresponded to a difference of 0.24 mmol/liter (9.3 mg/dl) in men and 0.15 mmol/liter (5.8 mg/dl) in women between drinkers of less than one cup and those of five or more cups/day, when other risk factors were taken into account. Systolic blood pressure was inversely related to tea with a difference between the same two tea groups of 2.1 mm in men and 3.5 mm in women. Altogether 396 men and 237 women died from all causes, and of these 141 and 18, respectively, died from coronary heart disease during the 12-year follow-up period. The mortality rate was higher (not statistically significant) among persons drinking no tea or less than one cup compared with persons drinking one or more cups/day. This applies to men and women and to coronary heart disease and all-cause mortality. For men, the relative risk (one or more versus less than one cup) for coronary death from Cox regression was 0.64 (95% CI:0.38, 1.07).
Article
METHODS. The relation between green tea consumption and serum lipid concentrations was examined using cross-sectional data on 1,306 males who received the retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and December 1988. RESULTS. After adjustment for rank, smoking, alcohol use, physical activity, and body mass index, serum total cholesterol levels were found to be inversely related to the consumption of green tea while no association was noted with serum triglycerides and high-density lipoprotein cholesterol. Adjusted mean concentrations of total cholesterol were 8 mg/dl lower in men drinking nine cups or more per day than in those consuming zero to two cups per day. Serum cholesterol levels were inversely associated with traditional Japanese dietary habits (intake of rice and soy bean paste soup) and positively associated with Westernized habits. Additional adjustment for these dietary variables did not alter the inverse relation between green tea and total cholesterol.
Article
Low density lipoproteins (LDL) can be oxidatively modified in vitro by macrophages and certain other cell types so that macrophages will take them up much faster. This process may be important in the formation of cholesterol-laden foam cells derived from macrophages in atherosclerotic lesions. In this study, we have shown that certain flavonoids, plant constituents found in the diet, are potent inhibitors of the modification of 125I-labelled LDL by macrophages, with IC50 values in the micromolar range (e.g. morin and fisetin 1 microM; quercetin and gossypetin 2 microM). The potencies of individual flavonoids in inhibiting LDL modification did not correlate with their previously determined potencies as inhibitors of 5-lipoxygenase and cyclo-oxygenase. The modification of LDL by macrophages exhibits a lag period of about 4-6 hr before enhanced uptake is detected. During this time, there is a rapid depletion in its content of alpha-tocopherol (an endogenous antioxidant found in lipoproteins) followed by a large increase in the level of hydroperoxides. The flavonoids conserved the alpha-tocopherol content of LDL and delayed the onset of detectable lipid peroxidation. Flavonoids also inhibited the cell-free oxidation of LDL mediated by CuSO4. These findings raise the possibility that flavonoids may protect LDL against oxidation in atherosclerotic lesions and may therefore be natural anti-atherosclerotic components of the diet, although this will depend to a large extent on their pharmacokinetics.
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Probucol [bis(3,5-di-tert-butyl-4-hydroxyphenylthio)propane] is a marketed cholesterol-lowering agent that has been shown to be a potent antioxidant. The antioxidant activity of probucol inhibits the formation of oxidatively modified low density lipoproteins (LDL) and reduces atherosclerosis in animals. The uniqueness of probucol is its association with LDL; about 70% of the plasma probucol resides in LDL particles. It has been hypothesized that such association directly protects LDL from oxidation inside the arterial wall. Similar to all chain-breaking antioxidants, probucol is oxidized, consumed, and depleted during oxidation. This chapter describes the in vivo metabolic pathway of probucol as it undergoes oxidation. Three major metabolites, spiroquinone, diphenoquinone, and bisphenol are discussed. Bisphenol is also an antioxidant, being oxidized to diphenoquinone when acting as such. Therefore, the antioxidant activity is continuously regenerated in vivo. The chapter describes the assay for the antioxidant activity of probucol in LDL and whole serum and the analytical procedures for the determination of probucol and probucol metabolites in serum. Determination of these metabolites in serum may provide insight as to the mode of action of probucol in inhibition of atherosclerosis.
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Flavonoids are polyphenolic antioxidants naturally present in vegetables, fruits, and beverages such as tea and wine. In vitro, flavonoids inhibit oxidation of low-density lipoprotein and reduce thrombotic tendency, but their effects on atherosclerotic complications in human beings are unknown. We measured the content in various foods of the flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin. We then assessed the flavonoid intake of 805 men aged 65-84 years in 1985 by a cross-check dietary history; the men were then followed up for 5 years. Mean baseline flavonoid intake was 25.9 mg daily. The major sources of intake were tea (61%), onions (13%), and apples (10%). Between 1985 and 1990, 43 men died of coronary heart disease. Fatal or non-fatal myocardial infarction occurred in 38 of 693 men with no history of myocardial infarction at baseline. Flavonoid intake (analysed in tertiles) was significantly inversely associated with mortality from coronary heart disease (p for trend = 0.015) and showed an inverse relation with incidence of myocardial infarction, which was of borderline significance (p for trend = 0.08). The relative risk of coronary heart disease mortality in the highest versus the lowest tertile of flavonoid intake was 0.42 (95% CI 0.20-0.88). After adjustment for age, body-mass index, smoking, serum total and high-density-lipoprotein cholesterol, blood pressure, physical activity, coffee consumption, and intake of energy, vitamin C, vitamin E, beta-carotene, and dietary fibre, the risk was still significant (0.32 [0.15-0.71]). Intakes of tea, onions, and apples were also inversely related to coronary heart disease mortality, but these associations were weaker. Flavonoids in regularly consumed foods may reduce the risk of death from coronary heart disease in elderly men.
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The cytoprotective effect of three flavonoids, catechin, quercetin and diosmetin, was investigated on iron-loaded hepatocyte cultures, considering two parameters: the prevention of iron-increased lipid peroxidation and the inhibition of intracellular enzyme release. These two criteria of cytoprotection allowed the calculation of mean inhibitory concentrations (IC50) which revealed that the effectiveness of these flavonoids could be classified as follows: catechin > quercetin > diosmetin. These IC50 values have been related to structural characteristics of the flavonoids tested. Moreover, the investigation of the capacity of these flavonoids to remove iron from iron-loaded hepatocytes revealed a good relationship between this iron-chelating ability and the cytoprotective effect. The cytoprotective activity of catechin, quercetin and diosmetin could thus be ascribed to their widely known antiradical property but also to their iron-chelating effectiveness. These findings increase further the prospects for the development and clinical application of these potent antioxidants.
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Evaluation of the vitro antioxidant activity of green and black tea, their in vivo effect on plasma antioxidant potential in man and the effect of milk addition. The antioxidant activity of the tea, with and without milk, was tested in vitro by measuring the length of the peroxyl radical induced lag-phase. The in vivo activity was tested on two groups of five healthy adults. Each group ingested 300 ml of either black or green tea, after overnight fast. The experiment was repeated on a separate day, adding 100 ml whole milk to the tea (ratio 1:4 ). Five subjects acted as controls. The human plasma antioxidant capacity (TRAP) was measured before and 30, 50 and 80 min from the ingestion of tea. Both teas inhibited the in vitro peroxidation in a dose-dependent manner. Green tea was sixfold more potent than black tea. The addition of milk to either tea did not appreciably modify their in vitro antioxidant potential. In vivo, the ingestion of tea produced a significant increase of TRAP (P <0.05), similar in both teas, which peaked at 30-50 min. When tea was consumed with milk, their in vivo activity was totally inhibited. The paper shows that tea possesses a strong antioxidant activity in vitro which is believed to be exerted by its polyphenols moiety. It also provides compelling evidence that tea has also a potent in vivo activity in man. The promptness of the in vivo response suggests that the absorption of the bioactive components of tea takes place in the upper part of the gastrointestinal system. The inhibition of this effect by milk is thought to be due to the complexation of tea polyphenols by milk proteins. These findings might help to clarify the putative role of dietary poly- phenols in modulating oxidative stress in vivo.
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A simple, automated test measuring the ferric reducing ability of plasma, the FRAP assay, is presented as a novel method for assessing "antioxidant power." Ferric to ferrous ion reduction at low pH causes a colored ferrous-tripyridyltriazine complex to form. FRAP values are obtained by comparing the absorbance change at 593 nm in test reaction mixtures with those containing ferrous ions in known concentration. Absorbance changes are linear over a wide concentration range with antioxidant mixtures, including plasma, and with solutions containing one antioxidant in purified form. There is no apparent interaction between antioxidants. Measured stoichiometric factors of Trolox, alpha-tocopherol, ascorbic acid, and uric acid are all 2.0; that of bilirubin is 4.0. Activity of albumin is very low. Within- and between-run CVs are <1.0 and <3.0%, respectively, at 100-1000 micromol/liter. FRAP values of fresh plasma of healthy Chinese adults: 612-1634 micromol/liter (mean, 1017; SD, 206; n = 141). The FRAP assay is inexpensive, reagents are simple to prepare, results are highly reproducible, and the procedure is straightforward and speedy. The FRAP assay offers a putative index of antioxidant, or reducing, potential of biological fluids within the technological reach of every laboratory and researcher interested in oxidative stress and its effects.
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Reactive oxygen species and reactive nitrogen species are formed in the human body. Endogenous antioxidant defences are inadequate to scavenge them completely, so that ongoing oxidative damage to DNA, lipids, proteins and other molecules can be demonstrated and may contribute to the development of cancer, cardiovascular disease and possibly neurodegenerative disease. Hence diet-derived antioxidants may be particularly important in protecting against these diseases. Some antioxidants (e.g. ascorbate, certain flavonoids) can exert pro-oxidant actions in vitro, often by interaction with transition metal ions. The physiological relevance of these effects is uncertain, as is the optimal intake of most diet-derived antioxidants. In principle, these ques