Cocoa Polyphenols Research Articles

Cocoa and Dark Chocolate Polyphenols: From Biology to Clinical Applications.

It is well known that cocoa and dark chocolate possess polyphenols as major constituents whose dietary consumption has been associated to beneficial effects. In fact, cocoa and dark chocolate polyphenols exert antioxidant and anti-inflammatory activities switching on some important signaling pathways such as toll-like receptor 4/nuclear factor κB/signal transducer and activator of transcription. In particular, cocoa polyphenols induce release of nitric oxide (NO) through activation of endothelial NO synthase which, in turn, accounts for vasodilation and cardioprotective effects. In the light of the above described properties, a number of clinical trials based on the consumption of cocoa and dark chocolate have been conducted in healthy subjects as well as in different categories of patients, such as those affected by cardiovascular, neurological, intestinal, and metabolic pathologies. Even if data are not always concordant, modifications of biomarkers of disease are frequently associated to improvement of clinical manifestations. Quite interestingly, following cocoa and dark chocolate ingestion, cocoa polyphenols also modulate intestinal microbiota, thus leading to the growth of bacteria that trigger a tolerogenic anti-inflammatory pathway in the host. Finally, many evidences encourage the consumption of cocoa and dark chocolate by aged people for the recovery of the neurovascular unit.

Effect of Dark Chocolate Extracts on Phorbol 12-Myristate 13-Acetate-Induced Oxidative Burst in Leukocytes Isolated by Normo-Weight and Overweight/Obese Subjects.

Oxidative and inflammatory stress represents a major risk factor for cardiovascular disease (CVD) in overweight and obese subjects. Between the different plant foods, chocolate has been shown to decrease CVD risk due to its antioxidant and anti-inflammatory properties. However, as we recently showed in epidemiological studies, meta-analyses, and human trials, dietary antioxidants resulted more effective in subjects characterized by an ongoing oxidative stress, than in healthy people. Aim of this work was to investigate the effect of different concentrations of chocolate phenolic extract (CPE) on in vitro free radical production, stimulated by phorbol 12-myristate 13-acetate (PMA), in leukocytes extracted from blood of normo-weight and overweight/obese subjects. Neutrophils from overweight/obese group had a significantly higher free radical production compared to the normo-weight group. In neutrophils, the lowest CPE concentration significantly reduced free radical production in overweight/obese group only, and higher CPE concentrations were effective in both groups. In monocytes, the CPE concentration that was significantly effective in reducing free radical production was lower in overweight/obese subjects than in normo-weight subjects. Chocolate polyphenol extracts inhibit oxidative burst in human neutrophils and monocytes with a higher efficiency in subjects characterized by an unphysiological oxidative/inflammatory stress, such as overweight and obese. Results of this study provide further evidence about a differential role of dietary antioxidant strictly related to the “stress” condition of the subjects.

Origin-based polyphenolic fingerprinting of Theobroma cacao in unfermented and fermented beans

A comprehensive analysis of cocoa polyphenols from unfermented and fermented cocoa beans from a wide range of geographic origins was carried out to catalogue systematic differences based on their origin as well as fermentation status. This study identifies previously unknown compounds with the goal to ascertain, which of these are responsible for the largest differences between bean types. UHPLC coupled with ultra-high resolution time-of-flight mass spectrometry was employed to identify and relatively quantify various oligomeric proanthocyanidins and their glycosides amongst several other unreported compounds. A series of biomarkers allowing a clear distinction between unfermented and fermented cocoa beans and for beans of different origins were identified. The large sample set employed allowed comparison of statistically significant variations of key cocoa constituents.

Anxiety levels moderate the protective effect of dark chocolate polyphenol intake against metabolic syndrome: The ATTICA study

Anxiety levels moderate the protective effect of dark chocolate polyphenol intake against metabolic syndrome: The ATTICA study

Dark chocolate polyphenol intake is an efficient predictor of metabolic syndrome: The ATTICA study

Dark chocolate polyphenol intake is an efficient predictor of metabolic syndrome: The ATTICA study

Uterus Weight of Ovariectomized Rats Given Cocoa Powder and Extract

Estrogen is a hormone that influences the growth of uterus. Ovariectomized rats lose their ovaries as the main source of estrogen so their uterus tends to shrink. The objective of thise study was to evaluate the potency of cocoa as an estrogen substitute, which was done through an experiment that tested the influence of cocoa products on the uterus weight of ovariectomized rats. There were five treatments and in each of the treatments, six wistar rats were given the substance for three days. Four groups of treatment consisted of ovariectomized rats given cocoa extract (875.2 ppm of polyphenols, 1 g/kg of body weight, BW), cocoa powder (369.8 ppm of polyphenols, 1 g/kg BW), olive oil (10 mL/kg BW), or estradiol valerate (1 mg/kg BW). The fifth group consisted of intact (non-ovariectomized) rats given 10 mL/kg BW of water. The finding showed that the ovariectomized rats given olive oil had lower uterus weight than that of intact rats, while the ovariectomized rats given estradiol valerate had higher uterus weight compared to the intact and olive oil groups. The ovariectomized rats given cocoa powder and extract had higher uterus weight compared to those given only olive oil; although they were not significantly different. Correlation between the body weight and uterus weight varied across treatment groups. The rats given olive oil showed significant, positive correlation, while the intact rats showed moderate, positive correlation. The rats given estradiol valerate and cocoa powder showed non-significant correlation. Since the polyphenol content in cocoa powder was at lower concentration than that in the cocoa extract, it was predicted that cocoa polyphenols are more potential in the lower concentration. This study concludes that even though consumption of cocoa powder and extract did not significantly induced uterus growth, cocoa is still considered having estrogenic activity by lowering the correlation between the body weight and uterus weight in ovariectomized rats.

Green and Efficient Extraction Method to Determine Polyphenols in Cocoa and Cocoa Products

Cocoa and cocoa products have broad and well-proven health benefits, most of which are associated with the high antioxidant capacity of cocoa flavonoids. Most extraction methods for flavonoids in cocoa products use several steps including a defatting step and large amount of organic solvents. Moreover, they are labor-intensive and time-consuming. In this work, a pressurized hot water extraction (PHWE) method has been compared to conventional sonication extraction (CSE) method. The contribution of individual compounds to the total antioxidant capacity of the extracts was evaluated by developing an analytical technique consisting of high-performance liquid chromatography (HPLC) with photodiode array coupled to electrochemical and to charged aerosol detectors and HPLC-mass spectrometry for the confirmation of the identity of compounds present. Additionally, procyanidins were analyzed by fluorescence detection. PHWE turned out to be more efficient in extracting phenolics and methylxanthines, as compared to the conventional method, in addition to being more “green” in terms of using less organic solvents.

Dietary and nutrition interventions for the therapeutic treatment of chronic fatigue syndrome/myalgic encephalomyelitis: a systematic review.

BackgroundChronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is characterised by unexplained fatigue for at least 6 months accompanied by a diverse but consistent set of symptoms. Diet modification and nutritional supplements could be used to improve patient outcomes, such fatigue and quality of life. We reviewed and discussed the evidence for nutritional interventions that may assist in alleviating symptoms of CFS/ME.MethodsMedline, Cinahl and Scopus were systematically searched from 1994 to May 2016. All studies on nutrition intervention were included where CFS/ME patients modified their diet or supplemented their habitual diet on patient‐centred outcomes (fatigue, quality of life, physical activity and/or psychological wellbeing).ResultsSeventeen studies were included that meet the inclusion criteria. Of these, 14 different interventions were investigated on study outcomes. Many studies did not show therapeutic benefit on CFS/ME. Improvements in fatigue were observed for nicotinamide adenine dinucleotide hydride (NADH), probiotics, high cocoa polyphenol rich chocolate, and a combination of NADH and coenzyme Q10.ConclusionsThis review identified insufficient evidence for the use of nutritional supplements and elimination or modified diets to relieve CFS/ME symptoms. Studies were limited by the number of studies investigating the interventions, small sample sizes, study duration, variety of instruments used, and studies not reporting dietary intake method. Further research is warranted in homogeneous CFS/ME populations.

Effect of Cocoa Polyphenolic Extract on Macrophage Polarization from Proinflammatory M1 to Anti-Inflammatory M2 State.

Polyphenols-rich cocoa has many beneficial effects on human health, such as anti-inflammatory effects. Macrophages function as control switches of the immune system, maintaining the balance between pro- and anti-inflammatory activities. We investigated the hypothesis that cocoa polyphenol extract may affect macrophage proinflammatory phenotype M1 by favoring an alternative M2 anti-inflammatory state on macrophages deriving from THP-1 cells. Chemical composition, total phenolic content, and antioxidant capacity of cocoa polyphenols extracted from roasted cocoa beans were determined. THP-1 cells were activated with both lipopolysaccharides and interferon-γ for M1 or with IL-4 for M2 switch, and specific cytokines were quantified. Cellular metabolism, through mitochondrial oxygen consumption, and ATP levels were evaluated. Here, we will show that cocoa polyphenolic extract attenuated in vitro inflammation decreasing M1 macrophage response as demonstrated by a significantly lowered secretion of proinflammatory cytokines. Moreover, treatment of M1 macrophages with cocoa polyphenols influences macrophage metabolism by promoting oxidative pathways, thus leading to a significant increase in O2 consumption by mitochondrial complexes as well as a higher production of ATP through oxidative phosphorylation. In conclusion, cocoa polyphenolic extract suppresses inflammation mediated by M1 phenotype and influences macrophage metabolism by promoting oxidative pathways and M2 polarization of active macrophages.

Discrimination of Cocoa Bean Origin by Chocolate Polyphenol Chromatographic Analysis and Chemometrics

Nowadays, the traceability and origin authentification in foodstuff is of great interest for consumers and industries. It is proved that the chemical composition is linked to the geographical and varietal origin of food products. Cocoa, the main ingredient in chocolate, provides a lot of polyphenol compounds still present in the chocolate bars. By analyzing these chemical species, we aim to investigate the information about the country of origin of chocolate. Our method is based on an acetone/water liquid/liquid extraction coupled with a high-performance liquid chromatography–diode array detector–mass spectrometry analysis (HPLC-DAD-MS). Forty-seven chocolate samples of different varieties (Criollo, Trinitario, Nacional, and Forastero) from 12 countries within two continents were analyzed. Polyphenols such as catechin, epicatechin, and several of procyanidins’ polymers were identified. Principal component analysis (PCA) was performed on 21 variables: 20 polyphenols and the polyphenol total content. The results highlight that the polyphenolic profile allows to classify the chocolate samples according to geographical origins (Madagascar, Caribbean, different countries from South America and Africa) as well as their variety.

The Cardiovascular Effects of Cocoa Polyphenols-An Overview.

Cocoa is a rich source of high-quality antioxidant polyphenols. They comprise mainly catechins (29%–38% of total polyphenols), anthocyanins (4% of total polyphenols) and proanthocyanidins (58%–65% of total polyphenols). A growing body of experimental and epidemiological evidence highlights that the intake of cocoa polyphenols may reduce the risk of cardiovascular events. Beyond antioxidant properties, cocoa polyphenols exert blood pressure lowering activity, antiplatelet, anti-inflammatory, metabolic and anti-atherosclerotic effects, and also improve endothelial function. This paper reviews the role of cocoa polyphenols in cardiovascular protection, with a special focus on mechanisms of action, clinical relevance and correlation between antioxidant activity and cardiovascular health.

Heterosis and heritability estimates of purine alkaloids and polyphenols in cocoa

Cocoa (Theobroma cacao L.) is an important allogamous tropical tree crop, whose centre of diversity is considered to be in Central America. Dry cocoa beans from five cocoa clones, and their intercrossed hybrids were analysed based on the variation of alkaloids and polyphenolic compounds contents, in order to gain insights on the heterosis and broad-sense heritability. Polyphenols and alkaloids were analysed at 280 nm by HPLC, using a Photodiode Array Detector (PDA); while anthocyanins were separated with the SEP-PAK Vac 6cc 1000 mg (waters) column and measured at 520 nm with a PDA. Dry cocoa beans displayed high content of purine alkaloids (2.1 and 8.8 mg g-1 for caffein and theobromine, respectively), and polyphenols (25 and 2978 μg g-1 for catechin and epicatechin, respectively). Among the five cocoa clones, SNK16 was the highest in purine alkaloid (caffein and theobromin) and flavanol (catechin and epicatechin); while T79/467 possessed the greatest quantity of cyanidin-3-galactoside and cyanidin-3-arabinoside. From all the parameters studied, anthocyanins (Cyanidin- 3-galactoside and cyanidin-3-arabinoside) exhibited the highest level of heterosis. Parental genotypes SNK16 and T79/467 showed good aptitudes for the combination of characters because their reciprocal hybrids F5 and F9, distinguished themselves by better levels of mid-parent heterosis values. Besides, the heritability value in strict sense of this Cyanidin-3-galactoside was very high. Absence of significant difference between genotypes, coming from reciprocal crossbreeding for Cyanidin-3-galactoside, suggests that this character in cocoa would be nuclear contrary to purine alkaloids and flavan-3-ols, where their transmission to offsprings can be stated as cytoplasmic.Key Words: Caffein, catechin, Theobroma cacao

Kinetics of hot air roasting of cocoa nibs and product quality

AbstractCocoa beans are widely used in the manufacturing of various food and beverage products such as chocolates, powdered drink, cookies, confectioneries, and others. Processing plays a vital role in governing the final flavor profile of cocoa beans especially during roasting. The current studies aimed to determine the transport properties of cocoa nibs during roasting and also to investigate the quality of roasted cocoa nibs. Cocoa nibs were roasted at temperatures of 120, 130, and 140 °C inside a hot air convective oven. Kinetics analyses showed that overall rates of sensible heating (from T = 27 to 100 °C) were in the range of 5.1–9.5 °C/min as compared to overall rates of effective roasting (from T = 100 °C onwards) in the range of 0.9–1.4 °C/min. The observed moisture content profiles followed the typical exponential decay as commonly explained by the Fick's second law of diffusion. The dependency of thermal and moisture diffusivities with temperatures could be described using quadratic and Arrhenius models, respectively. It was determined that the average order of magnitude for moisture diffusivity was 10−10 m2/s as compared to 10−9 m2/s for thermal diffusivity. High roasting temperature had a negative impact on cocoa polyphenols where greater degradation was observed. Sensory evaluation showed that cocoa liquor produced from the higher temperature treatment (T = 140 °C) had the highest cocoa flavor.Practical applicationsInformation on the roasting kinetics and moisture/thermal diffusivities are important design parameters for cocoa roaster. Changes in flavor quality during roasting are important in governing the development of flavor in the finished chocolate products. Therefore, the current studies contribute knowledge to the cocoa industry for both equipment and chocolate manufacturers.

Effects of dark chocolate on NOX-2-generated oxidative stress in patients with non-alcoholic steatohepatitis.

Activation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is considered a pathogenetic mechanism determining fibrosis and disease progression in non-alcoholic steatohepatitis (NASH). Polyphenols exert antioxidant action and inhibit NADPH oxidase in humans. To analyse the effect of cocoa polyphenols on NADPH oxidase isoform 2 (NOX2) activation, oxidative stress and hepatocyte apoptosis in a population affected by NASH. In a cross-sectional study comparing 19 NASH and 19 controls, oxidative stress, as assessed by serum NOX2 activity and F2-isoprostanes, and hepatocyte apoptosis, as assessed by serum cytokeratin-18 (CK-18) levels, were measured. Furthermore, the 19 NASH patients were randomly allocated in a crossover design to 40 g/day of dark chocolate (>85% cocoa) or 40 g/day of milk chocolate (<35% cocoa), for 2 weeks. sNOX2-dp, serum isoprostanes and CK-18 were assessed at baseline and after 2 weeks of chocolate intake. Compared to controls, NASH patients had higher sNOX2-dp, serum isoprostanes and CK-18 levels. A significant difference for treatments was found in subjects with respect to sNOX2-dp, serum isoprostanes and serum CK-18. The pairwise comparisons showed that, compared to baseline, after 14 days of dark chocolate intake, a significant reduction in sNOX2-dp serum isoprostanes and CK-18 M30 was found. No change was observed after milk chocolate ingestion. A simple linear regression analysis showed that ∆ of sNOX2-dp was associated with ∆ of serum isoprostanes. Cocoa polyphenols exert an antioxidant activity via NOX2 down-regulation in NASH patients.

Cocoa polyphenols and fiber modify colonic gene expression in rats

Purpose Cocoa intake has been associated with health benefits, improving cardiovascular function and metabolism, as well as modulating intestinal immune function. The aim of this study was to take an in-depth look into the mechanisms affected by the cocoa intake by evaluating the colonic gene expression after nutritional intervention, and to ascertain the role of the fiber of cocoa in these effects.MethodsTo achieve this, Wistar rats were fed for 3 weeks with either a reference diet, a diet containing 10 % cocoa (C10), a diet based on cocoa fiber (CF) or a diet containing inulin (I). At the end of the study, colon was excised to obtain the RNA to evaluate the differential gene expression by microarray. Results were validated by RT-PCR.ResultsThe C10 group was the group with most changes in colonic gene expression, most of them down-regulated but a few in common with the CF diet. The C10 diet significantly up-regulated the expression of Scgb1a1 and Scnn1 g and down-regulated Tac4, Mcpt2, Fcer1a and Fabp1 by twofold, most of them related to lipid metabolism and immune function. The CF and I diets down-regulated the expression of Serpina10 and Apoa4 by twofold. Similar patterns of expression were found by PCR.ConclusionMost of the effects attributed to cocoa consumption on genes related to the immune system (B cell and mast cell functionality) and lipid metabolism in the colon tissue were due not only to its fiber content, but also to the possible contribution of polyphenols and other compounds.

Model Fermentation of Cocoa (Theobroma cacao) can Produce Similar Microbial and Chemical Quality of Cocoa Compared to Conventional On‐Farm Cocoa Fermentation

Polyphenols in cocoa beans contribute from 12 to 18% dry weight of the whole bean. The major constituent polyphenols in cocoa are catechins (37%), procyanidins (58%) and anthocyanins (4%). Despite the high content of polyphenols in cocoa, cocoa processing including fermentation significantly affects the composition and concentration of polyphenols. Study of cocoa fermentation at the laboratory scale is challenging since industrial cocoa fermentation requires at least 25 kg of fresh wet beans to achieve the proper conditions for fermentation. In this study, dried unfermented cocoa bean and a simulated pulp were used as substrate for laboratory scale fermentation. Microbial and chemical characteristics were monitored over the course of fermentation. Commercially available dried unfermented cocoa bean was first rehydrated with water and then mixed with simulated pulp media developed to ensure the growth of yeast, lactic acid bacteria and acetic acid bacteria, the essential microorganisms for cocoa fermentation. A temperature profile similar to on‐farm cocoa fermentation was acheived using a laboratory incubator. Aeration by shaking the fermentation box at 150 rpm promoted growth of acetic acid bacteria. As a result, internal pH of the cocoa bean decreased from pH 5.73 to pH 4.8 over 7 days of fermentation. By using selective and differential media, yeast growth reached 5.28 × 108 CFU/ml at day 4 and anaerobic bacteria was detected from day 1 and reached the highest concentration of 3.16 × 109 CFU/ml at day 4. Aerobic bacteria was also detected from day 1 and increased gradually to reach a maximum of 2.29 × 109 CFU/ml at day 4. Total concentration of procyanidin (mean ± STDEV) in fermented cocoa bean was analyzed using 4‐Dimethylaminocinnemaldehyde (DMAC) method. Total procyanidin decreased by 64% from day 0 to day 7 (day 0: 0.19 ± 0.01 g procyanidin B2 equivalents/g cocoa extract, day 7: 0.07 ± 0.01 g procyanidin B2 equivalents/g cocoa extract). Folin‐Ciocalteu colorimetric method was performed to determine the total polyphenol content (mean ± STDEV) during fermentation and a 33% decrease was observed from day 0 to day 7 (day 0: 3.63 ± 0.2 g gallic acid equivalents/g cocoa extract, day 7: 2.45 ± 0.2 g gallic acid equivalents/g cocoa extract). The cocoa fermentation model developed in this study will be further employed to evaluate the effect of fermentation conditions on concentration and composition of bioactive compounds and bioactivity thereof in cocoa.Support or Funding InformationVirginia Agricultural Experiment Station salary and startup support for A. Stewart

Carrots, tomatoes and cocoa: Research on dietary antioxidants in Düsseldorf

Dietary antioxidants, their biological effects and underlying mechanisms of action are key topics of research at the Institute of Biochemistry and Molecular Biology I at the Heinrich-Heine University in Düsseldorf where Helmut Sies is active now since more than 35 years. In the present article his research activity on carotenoids is summarized including studies on their bioavailability, antioxidant properties, cellular signaling and dermatological effects. Additionally, comparable studies on cocoa polyphenols are described.

Cocoa polyphenols exhibit antioxidant, anti-inflammatory, anticancerogenic, and anti-necrotic activity in carbon tetrachloride-intoxicated mice

The therapeutic effects of cocoa polyphenols on acute carbon tetrachloride (CCl4)-intoxicated mice were investigated. After determining polyphenols profile in the cocoa extract (CE), CE at a dose of 34.5 mg/kg and epicatechin (EC) at a dose of 2.24 mg/kg were intraperitoneally (i.p.) administered to BALB/cN mice following CCl4 treatment. CE and EC post-treatments suppressed hepatotoxicity and inflammation, ameliorated serum markers of liver injury, returned blood lactate and glucose levels to normal, stimulated synthesis and storage of liver glycogen, and modulated glucose metabolism imbalance induced by CCl4. Cocoa polyphenols also exhibited early stage antifibrotic and anticarcinogenic effects. They affected beneficially the mitochondrial functionality acting on dysfunction in mitochondrial respiration caused by CCl4 and antioxidants regulation at subcellular levels.

A new food frequency questionnaire to assess chocolate and cocoa consumption

ObjectiveCocoa has been highlighted as a food with potential benefits to human health because of its polyphenol content. However, few studies show the contribution of cocoa and chocolate products in polyphenol intake. The aim of this work was to develop a food frequency questionnaire (FFQ) for evaluating the intake of food products containing cocoa (C-FFQ). MethodsA sample of 50 university students was recruited to complete the 90-item questionnaire, a validated questionnaire (called here European Food Safety Authority [EFSA]-Q) as well as a 24-hour dietary recall (24 HDR). Spearman correlation test, Bland-Altman plots, and quintile classification analysis were conducted together with the Wilcoxon test and descriptive statistics. ResultsSignificant correlations between the C-FFQ and the EFSA-Q for the most common cocoa/chocolate products were observed (P < 0.05), as well as between data from the C-FFQ and 24 HDR (P < 0.05). However, a number of cocoa/chocolate products frequently consumed by the participants were detected by the C-FFQ and 24 HDR which were not included in the EFSA-Q. According to the C-FFQ, chocolate bars were the main source of cocoa in university students, but dairy products also provided an important amount of cocoa. ConclusionThe developed C-FFQ questionnaire can be considered as a valid option for assessing the consumption frequency of cocoa/chocolate-derived products, thereby allowing the evaluation of cocoa polyphenol intake in further studies.

Effects of Chocolate Intake on Oxidative Stress/Oxidant-antioxidant Balance in Medical Students: A Controlled Clinical Trial.

Background and Aim:Cocoa polyphenols have been shown to exhibit antioxidant properties in vivo and in vitro. This study aimed to determine whether commercially available chocolate could improve oxidant/antioxidant balance in medical students.Materials and Methods:Sixty students (30 males and 30 females) were given three different types of chocolate. Subjects were divided equally into three groups of 20 students (10 males and 10 females) as follows: (i) Dark chocolate group (DC), (ii) milk chocolate group (MC), and (iii) placebo group (PC). The placebo group was given white chocolate. Blood was drawn at baseline and after consumption of chocolate (40 g/day) for 2 weeks. Serum was analyzed for DNA/RNA oxidative damage, thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), and glutathione peroxidase (GPX) enzymes. Descriptive analyses were conducted to determine the frequency distributions of the study variables. Means were compared across the study groups by one-way Analysis of Variance and within the same group by paired t-test.Results:Mean serum DNA/RNA damage, TBARS, SOD, and GPX enzymes compared between the groups revealed insignificant differences after 2 weeks of chocolate consumption (P = 0.46, 0.19, 0.11, and 0.06). Comparison within the same group also exhibited statistically insignificant differences in DNA/RNA damage in DC and MC groups (0.29 and 0.46, respectively); TBARS in DC and MC groups (0.11 and 0.19, respectively); SOD in DC and MC groups (0.06 and 0.11, respectively); and GPX in DC and MC groups (0.68 and 0.78, respectively).Conclusion:Consumption of 40 g of DC or MC daily for a period of 2 weeks appears to be an ineffective way of improving oxidant/antioxidant balance in medical students.