Rapid peroxyl radical scavenging capacity (PSC) assay for assessing both hydrophilic and lipophilic antioxidants

This paper reports a simple, rapid, and sensitive assay for assessing peroxyl radical scavenging capacity (PSC) of both hydrophilic and lipophilic antioxidant compounds and food extracts. The assay is based on the degree of inhibition of dichlorofluorescin oxidation by antioxidants that scavenge peroxyl radicals, generated from thermal degradation of 2,2'-azobis(amidinopropane). For hydrophilic antioxidant activity, the dose required to cause a 50% inhibition of the reaction (EC(50)) ranged from 2.41 +/- 0.02 (EGCG) to 21.26 +/- 0.38 microM (ferulic acid). EC(50) values for the hydrophilic antioxidant activity of food extracts ranged from 309.2 +/- 3.63 (apple) to 3345.1 +/- 151.5 micromol of vitamin C equiv/100 g for wheat bran. The EC(50) values for lipophilic antioxidant activity were 1.58 +/- 0.11 (Trolox), 4.35 +/- 0.43 (alpha-tocopherol), 18.94 +/- 0.38 (BHA), and 182.69 +/- 13.7 microM (BHT). Whole grain lipophilic antioxidant activity ranged from 3.49 +/- 0.57 (wheat) to 8.79 +/- 1.98 micromol of alpha-tocopherol equiv/100 g of rice. Hydrophilic antioxidant activity contributed >98% of the total antioxidant activity (hydrophilic plus lipophilic) of whole grains tested. The PSC assay was accurate (86-108% recovery), precise (0.12-11% CV), and reproducible (12% RSD) and produced results comparable to those of similar published assays. The PSC assay can be routinely used to analyze or screen both hydrophilic and lipophilic antioxidants or food extracts and will be a valuable alternative biomarker for future epidemiological studies of chronic diseases.     

Iron status of adolescent girls from two boarding schools in southern Benin

Iron deficiency (ID) is the most prevalent micronutrient deficiency in the world, particularly in developing countries. Blood samples and a qualitative FFQ on Fe- and vitamin C-rich foods were obtained in 180 adolescent girls aged 12 to 17 years living in two boarding schools from south Benin. ID, defined as serum ferritin either 73 micromol/l or transferrin saturation<20%, was found in 32% of subjects. Anaemia (Hb<120 g/l) was found in 51% of adolescents, while 24% suffered from iron-deficiency anaemia (IDA) (ID and Hb<20 g/l). After adjusting for confounding factors (age, mother's and father's occupation, household size) in a logistic regression equation, subjects having a low meat consumption (beef, mutton, pork) (<4 times/week) were more than twice as likely to suffer from ID (OR=2.43; 95% CI 1.72, 3.35; P=0.04). Adolescents consuming less fruits (<4 times/week) also had a higher likelihood of suffering from ID (OR=1.53; 95% CI 1.31, 2.80; P=0.03). Finally, subjects whose meat consumption was low were twice as likely to suffer from IDA (OR=2.24; 95% CI 1.01, 4.96; P=0.04). The prevalence of ID represents an important health problem in these Beninese adolescent girls. A higher consumption of Fe-rich foods and of promoters of Fe absorption (meat factor and vitamin C) is recommended to prevent ID deficiency in these subjects.     

Glutathione peroxidase activity, TBARS, and alpha-tocopherol in meat from chickens fed different diets.

This study investigated the effect of feeding broilers with diets differing in dietary fat source (lard, sunflower oil, olive oil) and vitamin E (basal vs supplemented with 200 mg of alpha-tocopheryl acetate/kg) on meat lipid oxidative stability. The diets differed by their degree of unsaturation and included the natural antioxidant alpha-tocopherol (vitamin E). Glutathione peroxidase (GSHPx) activity was measured in raw meat and ranged from 3.62 to 8.06 nmol NADPH/min/mg protein. The enzyme activity was influenced by the degree of unsaturation of the diet. Capillary gas chromatography analyses showed that dietary alpha-tocopherol accumulated in the muscle tissue and contributed to a better oxidative stability of the raw and cooked meat. Thigh meat alpha-tocopherol levels ranged from 2.73 to 3.62 microg/g in unsupplemented chickens whereas levels from 8.69 to 13.37 microg/g were observed in the thigh meat from alpha-tocopherol supplemented animals. The inclusion of olive oil and alpha-tocopherol in the animal diet gave lower thiobarbituric acid reactive substance (TBARS) values and lower GSHPx activity. High correlations were found between the parameters studied. The results suggest that the glutathione peroxidase activity could be used as an indicator of the meat oxidative stability. A negative relationship was observed between GSHPx activity and tissue alpha-tocopherol levels, and a positive relationship was evidenced between TBARS and antioxidant enzyme activity.     

Antioxidant activity of selected Spanish wines in corn oil emulsions

Wines contain phenolic compounds that may be useful for preventing lipid oxidation as dietary antioxidants. This study was aimed at evaluating the antioxidant activity in corn oil emulsions of seventeen selected Spanish wines and two California wines. The inhibition of hydroperoxide formation at 10 microM gallic acid equivalents (GAE) varied from 8.4% to 40.2% with the red wines, from 20.9% to 45.8% with the rosé wines, and from 6.5% to 47.0% with the white wines. The inhibition of hydroperoxide formation at 20 microM GAE varied from 11.9% to 34.1% with the red wines, from 0.1% to 34. 5% with the rosé wines, and from 3.3% to 37.2% with the white wines. The inhibition of hexanal formation at 10 microM GAE varied from 23. 6% to 64.4% with the red wines, from 42.7% to 68.5% with the rosé wines, and from 28.4% to 68.8% with the white wines. The inhibition of hexanal formation at 20 microM GAE varied from 33.0% to 46.3% with the red wines, from 11.3% to 66.5% with the rosé wines, and from -16.7% to +21.0% with the white wines. The antioxidant effect decreased with increasing concentration. This antioxidant activity was related to the five main groups of phenolic compounds identified in wines by HPLC. The relative antioxidant activity correlated positively with the total phenol content of wines (by the Folin-Ciocalteu method and by HPLC), benzoic acids, anthocyanins, flavan-3-ols, and flavonols, for the inhibition of hydroperoxides and hexanal at 10 and 20 microM GAE.     

Lipophilic and hydrophilic antioxidant capacities of common foods in the United States

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORAC(FL)) assay with fluorescein as the fluorescent probe and 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin-Ciocalteu reagent. Hydrophilic ORAC(FL) values (H-ORAC(FL)) ranged from 0.87 to 2641 micromol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORAC(FL) values (L-ORAC(FL)) ranged from 0.07 to 1611 micromol of TE/g. Generally, L-ORAC(FL) values were <10% of the H-ORAC(FL) values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORAC(FL) and H-ORAC(FL). Differences of ORAC(FL) values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORAC(FL). The data demonstrated that processing can have significant effects on ORAC(FL). Considering all of the foods analyzed, the relationship between TP and H-ORAC(FL) showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 micromol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994-1996).     

Seasonal variations in the level of plant constituents in greenhouse production of cherry tomatoes

The content of selected plant constituents was measured in cherry tomatoes (Lycopersicon esculentumMill. cv. Jennita) during conventional Norwegian tomato production in a greenhouse from May until October 2004. Samples were collected according to standard production procedure with orange-yellow colored fruits at weight in the range of 12.4-19.3 g and size in the range of 28.9-33.0 mm (diameter). The content of selected compounds based on 100 g FW were found to vary in the following range during the season: 7.38-28.38 mg of chalconaringenin, 0.32-0.92 mg of rutin, 0.24-1.06 mg of chlorogenic acid, 5.60-20.02 mg of ascorbic acid, 1.60-5.54 mg of lycopene, and 0.37-0.55 mg beta-carotene. Only minute amounts of naringenin together with kaempferol 3-rutinoside and caffeic acid, which previously have been reported from tomatoes, were detected. The content of chalconaringenin to rutin and that of lycopene to beta-carotene showed a strong correlation during the season (p < 0.001). The content of total phenolics and methanol-soluble antioxidants also showed a correlation (p < 0.001), and were found in the range 14.6-32.6 mg of gallic acid equivalents (GAE)/100 g fresh weight (FW) and 445-737 micromol of Fe(II)/100 g FW, respectively. Seasonal variation in the level of plant constituents is shown to be related to photon flux density and fertilization level.     

Inhibition of malonaldehyde formation in oxidized calf thymus DNA with synthetic and natural antioxidants

Calf thymus DNA was oxidized by Fenton's reagent with or without synthetic antioxidants (Trolox and DMPO) and natural antioxidants-quercetin, apigenin, 2'-O-glycosylisovitexin (2'-O-GIV), (+)-catechin, cyanidin, pelargonidin, keracyanin, and callistephin. Malonaldehyde (MA) formed in oxidized DNA was analyzed using gas chromatography. MA formed from oxidized DNA without antioxidants was 4.0 +/- 0.53 nmol/mg of DNA in buffer solution, 3.7 +/- 0.34 nmol/mg of DNA in NaOH solution, and 4.6 +/- 0.19 nmol/mg of DNA in HCl solution. MA formed from DNA with antioxidants (at the level of 0.1 micromol/mL) ranged from 1.90 +/- 0.18 (catechin) to 4.10 +/- 0.18 nmol/mg of DNA (cyanidin). Trolox and DMPO inhibited MA formation from DNA by 41.2% and 18.6%, respectively, at the level of 0.1 micromol/mL. Trolox (water-soluble vitamin E) exhibited dose-dependent inhibition. The decreasing order of inhibitory effect by flavonoids at the level of 0.1 micromol/mL was catechin (48.5%) > quercetin (47.1%) > 2'-O-GIV (40.5%) > apigenin (29.9%) and by the anthocyanins at the level of 0.1 micromol/mL was callistephin (45%) > keracyanin (33.2%) > pelargonidin (25.1%) > cyanidin (10.2%).     

Individual and combined antioxidant effects of seven phenolic agents in human erythrocyte membrane ghosts and phosphatidylcholine liposome systems: importance of the partition coefficient

Antioxidant activities of seven phenolic agents against Fe(2+)-induced lipid oxidation were compared with alpha-tocopherol, beta-carotene, and vitamin C in human erythrocyte membrane ghosts and liposome systems. The antioxidant activity of five test flavonoids followed the order catechin > epicatechin > rutin > quercetin > myricetin in both systems (p < 0.05), which was negatively correlated with their partition coefficients. The antioxidant interaction of these phenolic agents with alpha-tocopherol, beta-carotene, or vitamin C in inhibiting Fe(2+)-induced lipid oxidation was examined. Synergistic effects were present in the combinations of alpha-tocopherol plus caffeic acid, catechin, or epicatechin as well as in all combinations of vitamin C plus phenolic antioxidants. On the basis of the stronger individual and combined effects present in caffeic acid, catechin, and epicatechin, the application of these three phenolic agents with or without alpha-tocopherol, beta-carotene, and vitamin C may provide stronger protective benefits against lipid oxidation, which may be helpful for oxidation-related diseases prevention.     

Effects of oxidized dietary oil and vitamin E supplementation on lipid profile and oxidation of muscle and liver of juvenile atlantic cod (Gadus morhua)

The effects of oxidized dietary lipid and the role of vitamin E on lipid profile, retained tocopherol levels, and lipid oxidation of juvenile Atlantic cod (Gadus morhua) were evaluated following a 9-week feeding trial. Four isonitrogenous experimental diets containing fresh or oxidized (peroxide value of 94 mequiv/kg) fish oil with or without added vitamin E (alpha-tocopherol or mixed tocopherols) were fed to juvenile cod in duplicate tanks. There was no significant (P > 0.05) influence on major lipid classes of cod liver and muscle by diet with the exception of sterols. Sterols content was increased in liver but decreased in muscle by oxidized dietary oil in the absence of vitamin E. Dietary vitamin E supplementation decreased the sterols level in cod liver but with no significant (P > 0.05) effect on their level in the muscle. Fatty acid composition varied between lipid fractions in muscle tissue and was affected by the diet. Oxidized oil significantly (P < 0.05) decreased the deposition of alpha-tocopherol in liver but not in muscle. gamma- and delta-Tocopherols from dietary tocopherol mixtures were retained at very low levels in liver, but higher retention was observed in muscle tissue. The oxidative state of both liver and muscle, as measured by the 2-thiobarbituric acid reactive substances (TBARS) and headspace propanal, negatively correlated with tissue vitamin E levels. It is suggested that oxidized oil affected juvenile Atlantic cod by causing vitamin E deficiency in certain tissues and that these effects could be alleviated by supplementation of a sufficient amount of dietary vitamin E. The results also indicate that mixed tocopherols were good antioxidants for Atlantic cod, although less effective than alpha-tocopherol alone in many tissues with the exception of muscle, where gamma- and delta-tocopherols were deposited at relatively high levels.     

Effects of vitamin E supplementation on lipid peroxidation and color retention of salted calf muscle from a diet rich in polyunsaturated fatty acids.

The color of fresh meat is one of the most important quality criteria of raw muscle foods. This red color is principally due to the presence of oxymyoglobin. The present study was undertaken to examine the effect of a diet rich in polyunsaturated fatty acids (PUFA), the addition of NaCl, and the influence of dietary supplementation with vitamin E on calf muscle oxymyoglobin oxidation (color) and lipid peroxidation. Vitamin E was added to the feed at a concentration of 4000 mg/day for 90 days before slaughter. This diet increased the alpha-tocopherol concentration in muscle membrane from 2.6-2.8 to 6.5-7.0 microg/g of fresh weight. It was found that the diet rich in PUFA and, especially, the addition of NaCl increased muscle lipid peroxidation and oxymyoglobin oxidation as indicated by the contents of thiobarbituric acid-reactive substances and substances that impaired color value readings during storage at 4 degrees C. Both undesirable reactions during storage were controlled very efficiently by the presence of a critically high concentration of alpha-tocopherol in the muscle tissues. The findings concerning the antioxidant activity of alpha-tocopherol in this study form additional evidence of its efficient protection against oxidative reactions during storage of muscle tissues and its potential to maintain a high nutritional value in them.     

Phenolic composition and antioxidant activity of aqueous infusions from Capparis spinosa L. and Crithmum maritimum L. before and after submission to a two-step in vitro digestion model

This study investigated the phenolic composition and antioxidant activities of aqueous infusions from wild-grown caper (Capparis spinosa L.) and sea fennel (Crithmum maritimum L.) from the Dalmatia region (Croatia) before and after their submission to an in vitro digestion process. HPLC/UV-vis-DAD/ESI-MS analysis of the caper infusion identified rutin, kaempferol 3-O-rutinoside, and isorhamnetin 3-O-rutinoside as dominant flavonoids in the matrix together with a series of cinnamoylquinic acid derivatives, whereas in the sea fennel aqueous infusion chlorogenic acid (5-caffeoylquinic acid), its isomers, and higher derivatives were identified as almost the sole class of phenolics. Both infusions exhibited good and dose-dependent antioxidant activity before in vitro digestion by the DPPH method, the β-carotene bleaching method, and copper-induced oxidation of human LDL. The amount of total phenolics (Folin-Ciocalteu assay) strongly decreased in digested samples (from 3.0 and 2.2% in caper and sea fennel infusions, respectively, to <1.0%), as did their antioxidant activity as measured by the three aforesaid methods. The results showed that the majority of phenolic compounds detected in both infusions are not stable under applied simulated gastrointestinal conditions and that the stability of these secondary metabolites strongly depends on the nature of the corresponding matrix.     

Lipid hydroperoxide determination in dark chicken meat through a ferrous oxidation-xylenol orange method

A ferrous oxidation-xylenol orange (FOX) method was adapted to measure lipid hydroperoxides (LHP) in raw and cooked dark chicken meat. Its applicability was evaluated using samples with different alpha-tocopherol contents or unsaturation degrees (both modulated by dietary supplementation). The FOX assay can work as an induced method because there is some oxidation of the sample extract during the incubation of the reaction. Consequently, it allows assessment of sample susceptibility to oxidation (response after some hours of incubation) and comparison of samples that are highly oxidized or readily susceptible to oxidation through their absorbance after 30 min of incubation. It is highly specific for LHP and showed a linear relationship between volume of meat extract and absorbance. However, the most suitable volume of extract and incubation time must be studied for each kind of sample. The use of butylated hydroxytoluene during this incubation is strongly discouraged because it attenuated the reaction by radical stabilization, thus diminishing Fe(III) formation and leading to a lower response.     

Lipid-soluble antioxidants status and some of its socio-economic determinants among pregnant Ethiopians at the third trimester

OBJECTIVE: To determine the serum levels of three lipid-soluble antioxidants (retinol, beta-carotene and alpha-tocopherol) in pregnant women attending an antenatal clinic (ANC) in Gondar, Ethiopia. DESIGN: A cross-sectional study involving laboratory determination of serum levels of retinol, alpha-tocopherol and beta-carotene using high-performance liquid chromatography and questionnaire-based assessment of socio-economic status. SETTING: ANC of a university teaching hospital. SUBJECTS: Three hundred and twenty-two healthy pregnant women in their third trimester, who attended the ANC. RESULTS: Mean serum levels of retinol, alpha-tocopherol and beta-carotene were found to be 1.23+/-0.5, 25.5+/-0.9 and 0.21+/-0.09 micromol l(-1), respectively. The prevalence of vitamin A deficiency (<1.05 micromol l(-1)) among pregnant women was 38.5%. Women having low retinol (vitamin A) levels were highly likely to live in earth-floored and mud-walled houses, and less likely to own a house and to have a latrine. CONCLUSION: The study shows that serum levels of lipid-soluble antioxidants were low among ANC attendees in northern Ethiopia. It also indicates that some socio-economic factors (such as poor housing standard) are associated with vitamin A deficiency.     

Effect of heated sunflower oil and dietary supplements on the composition, oxidative stability, and sensory quality of dark chicken meat

A factorial design was used to study the effect of dietary oxidized sunflower oils (fresh, heated at low temperatures, and heated at high temperatures), DL-alpha-tocopheryl acetate (0 or 100 mg/kg), and Zn supplementation (0 or 600 mg/kg) on the composition, oxidative stability, and sensory quality of dark chicken meat with skin from animals fed with a Se supplement (Se-enriched yeast, 0.6 mg of Se/kg). The positional and geometrical isomers of linoleic acid were increased in raw meat from chickens fed oils oxidized at high temperatures. In addition, supplementation with alpha-tocopheryl acetate increased the alpha-tocopherol content, whereas 2-thiobarbituric acid (TBA) values and lipid hydroperoxide content were reduced. Likewise, TBA values, rancid aroma, and rancid flavor also decreased in cooked dark meat. However, none of the dietary factors studied affected consumer acceptability scores of cooked meat. Furthermore, Zn supplementation increased the Se content in raw meat.     

Pre- and post-mortem use of grape seed extract in dark poultry meat to inhibit development of thiobarbituric acid reactive substances

Diets containing grape seed extract (GSE)-control, GSE [low GSE, low GSE + methionine, high GSE, and high GSE + methionine], or alpha-tocopherol-were fed to broiler chicks to estimate the antioxidative activity of GSE in processed meat. GSE was detrimental to the growth of chicks, and methionine did not reverse the detrimental effect. GSE with 85.4 g of gallic acid equiv/100 g (GAE 85.4) was added to ground dark turkey meat to obtain treatments with no GSE, 1.0% GSE, and 2.0% GSE and then processed as unsalted or salted and unheated or heated. Processed treatments were analyzed for thiobarbituric acid reactive substances (TBARS) and percent expressible moisture (%EM). GSE at 1.0 and 2.0% decreased TBARS values nearly 10-fold as compared to the control. GSE (1.0%) had a %EM value significantly greater than that of the control. GAE 85.4 decreased TBARS values more than GAE 88.9.     

Development and validation of oxygen radical absorbance capacity assay for lipophilic antioxidants using randomly methylated beta-cyclodextrin as the solubility enhancer

We recently reported the improved oxygen radical absorbance capacity (ORAC) assay using fluorescein (FL) as the fluorescent probe. The current ORAC(FL) assay is limited in hydrophilic antioxidant due to the aqueous environment of the assay. Lipophilic antioxidants mainly include the vitamin E family and carotenoids, which play a critical role in biological defense systems. In this paper, we expanded the current ORAC(FL) assay to lipophilic antioxidants. Randomly methylated beta-cyclodextrin (RMCD) was introduced as the water solubility enhancer for lipophilic antioxidants. Seven percent RMCD (w/v) in a 50% acetone-H(2)O mixture was found to sufficiently solubilize vitamin E compounds and other lipophilic phenolic antioxidants in 75 mM phosphate buffer (pH 7.4). This newly developed ORAC assay (abbbreviated ORAC(FL-LIPO)) was validated through linearity, precision, accuracy, and ruggedness. The validation results demonstrate that the ORAC(FL-LIPO) assay is reliable and robust. For the first time, by using 6-hydroxy-2,5,7,8-tetramethyl-2-carboxylic acid as a standard (1.0), the ORAC values of alpha-tocopherol, (+)-gamma-tocopherol, (+)-delta-tocopherol, alpha-tocopherol acetate, tocotrienols, 2,6-di-tert-butyl-4-methylphenol, and gamma-oryzanol were determined to be 0.5 +/- 0.02, 0.74 +/- 0.03, 1.36 +/- 0.14, 0.00, 0.91 +/- 0.04, 0.16 +/- 0.01, and 3.00 +/- 0.26, respectively. The structural information of oxidized alpha-tocopherol obtained by liquid chromatography/mass spectrometry reveals that the mechanism for the reaction between the vitamin E and the peroxyl radical follows the hydrogen atom transfer mechanism, which is in agreement with the notion that vitamin E is the chain-breaking antioxidant.     

Vitamin A status in Cuban children aged 6-11 years

OBJECTIVE AND SETTING: A nationwide study was performed in Cuba to assess vitamin A status and the intake of vitamin-A-providing foods in children aged 6-11 years. DESIGN AND SUBJECTS: The sample comprised 1191 schoolchildren from first to sixth grade, both sexes, from municipalities randomly selected from the five eastern provinces of Cuba in 2002 (first semester) and from the four western and four central provinces in 2003 (first semester). A food-frequency questionnaire was completed by 2038 mother-and-child pairs. RESULTS: Mean (+/-standard deviation) plasma retinol concentrations were 1.77 +/- 0.48 micromol l-1 in the western, 2.01 +/- 0.56 micromol l-1 in the central and 1.40 +/- 0.41 micromol l-1 in the eastern region. No child had plasma retinol concentration below 0.35 micromol l-1, indicative of a high risk of clinical deficiency. Subclinical deficiency, plasma retinol concentration of 0.35-0.7 micromol l-1, was seen in 1.05 micromol l-1) was present in >90% of subjects in all western and central provinces, and in one of the eastern provinces (Holguín), whereas in the four remaining eastern provinces, adequate status was present in >75%. Only nine fruits and vegetables were consumed frequently (>3 times per week) by >50% of children. Thirty-seven per cent regularly consumed a supplement containing vitamin A. CONCLUSIONS: Most Cuban children aged 6-11 years had adequate vitamin A status. Consumption of foods rich in vitamin and provitamin A, especially vegetables, was frequent but limited to a small variety of foods.     

Impact of disaggregation of composite foods on estimates of intakes of meat and meat products in Irish adults

OBJECTIVE: To evaluate the impact of the disaggregation of composite foods on intake estimates of meat and individual meat categories and on the contribution of meat to nutrient intakes in Irish adults. DESIGN: Data were analysed from the North/South Ireland Food Consumption Survey, which used a 7-day food diary to estimate food intake. Of 742 food codes that contained meat, 320 were codes for meat consumed as an individual portion and 422 were composite foods and were disaggregated to estimate the meat content. SUBJECTS: A nationally representative sample of 475 men and 483 women (not pregnant or lactating) from the Republic of Ireland aged 18-64 years. RESULTS: The mean intake of meat was 134 g day(-1) in consumers (98.5%) and men (168 g day(-1)) consumed significantly more (P<0.001) than women (102 g day(-1)). Mean intakes of meat were higher in subjects with manual skilled occupations (P<0.01) and lower in those with third-level educational qualifications (P<0.05). Without disaggregating meat from composite foods, meat intake was overestimated by 43% (57 g day(-1)) and varied widely by meat category. Meat disaggregated from composite foods contributed 25% of meat intake. The contribution meat made to nutrient intakes ranged from 29% for protein, vitamin B12, zinc and niacin to 20% for vitamin D, 16% for vitamin B6, 15% for thiamine and 14% for iron. CONCLUSIONS: Failure to disaggregate meat from composite foods substantially overestimates meat intake, with a large variation between meat categories. This has important implications for estimates of meat intakes in nutritional epidemiological studies and for food safety purposes.     

Lipid peroxidation and coupled vitamin oxidation in simulated and human gastric fluid inhibited by dietary polyphenols: health implications

The Western diet contains large quantities of oxidized lipids, because a large proportion of the food in the diet is consumed in a fried, heated, processed, or stored form. We investigated the reaction that could occur in the acidic pH of the stomach and accelerate the generation of lipid hydroperoxides and cooxidation of dietary vitamins. To estimate the oxygen content in the stomach after food consumption, oxygen released from masticated bread (20 g) into deoxygenated water (100 mL) was measured. Under these conditions, the oxygen concentration rose by 250 microM and reached a full oxygen saturation. The present study demonstrated that heated red meat homogenized in human gastric fluid, at pH 3.0, generated hydroperoxides and malondialdehyde. The cross-reaction between free radicals produced during this reaction cooxidized vitamin E, beta-carotene, and vitamin C. Both lipid peroxidation and cooxidation of vitamin E and beta-carotene were inhibited at pH 3.0 by red wine polyphenols. Ascorbic acid (44 mg) at a concentration that represented the amount that could be ingested during a meal inhibited lipid peroxidation only slightly. Red wine polyphenols failed to prevent ascorbic acid oxidation significantly but, in conjunction with ascorbic acid, did inhibit lipid peroxidation. In the presence of catechin, a well-known polyphenol found in red wine, ascorbic acid at pH 3.0 works in a synergistic manner preventing lipid peroxidation and beta-carotene cooxidation. The present data may explain the major benefits to our health and the crucial role of consuming food products rich in dietary antioxidants such as fruits, vegetables, red wines, or green tea during the meal.     

Effect of buckwheat extract on the antioxidant activity of lipid in mouse brain and its structural change during in vitro human digestion

This study was conducted to investigate the effects of buckwheat ( Fagopyrum esculentum Moench cv. Yangjul No. 2) extract on the antioxidant activity of lipids in mouse brain and the structural change during in vitro human digestion. Buckwheat was collected from a wild farm and extracted with water. The buckwheat extracts were then passed through an in vitro human digestion model that simulated the composition of the mouth, stomach, and small intestine juice. The results confirmed that the main phenolics of buckwheat extract were rutin, quercitrin, and quercetin. The rutin content increased with digestion of the buckwheat (from 48.82 to 96.34 μg/g) and rutin standard samples (from 92.76 to 556.56 μg/g). Antioxidant activity was more strongly influenced by in vitro human digestion of both buckwheat and rutin standard. After digestion by the small intestine, the antioxidant activity values were dramatically increased (from 5.06 to 87.82%), whereas the antioxidant activity was not influenced by digestion in the stomach for both buckwheat extract and rutin standard. Inhibition of lipid oxidation of buckwheat in mouse brain lipids increased after digestion in the stomach for both buckwheat extract and the rutin standard. The major finding of this study was that in vitro human digestion may be an important modulator of the antioxidant capacity of buckwheat and that this may be because in vitro human digestion increased the antioxidative activity via an increase in antioxidants such as rutin and quercetin.