The goal of the present study was to investigate whether subchronic treatment with grape juice concentrate is able to protect liver and peripheral blood cells against cholesterol-induced injury in rats. The effects of the grape juice concentrate treatment on histopathological changes, immunohistochemistry for cyclo-oxygenase-2 (COX-2), and basal and oxidative DNA damage induced by H2O2 using a single-cell gel (comet) assay were evaluated. Male Wistar rats (n 18) were divided into three groups: group 1 – negative control; group 2 – cholesterol at 1 % (w/w) in their diet, treated for 5 weeks; group 3 – cholesterol at 1 % in their chow, treated for 5 weeks, and grape juice concentrate at 222 mg/d in their drinking-water in the final week only. The results indicated that the treatment with grape juice concentrate did not show remarkable differences regarding liver tissue in group 3 compared with group 2. However, grape juice concentrate was able to decrease oxidative DNA damage induced by H2O2 in peripheral blood cells, as depicted by the tail moment results. COX-2 expression in the liver did not show statistically significant differences (P>0·05) between groups. Taken together, the present results suggest that the administration of subchronic grape juice concentrate prevents oxidative DNA damage in peripheral blood cells.

Antioxidant requirements have neither been defined for endurance nor been defined for ultra-endurance athletes. To verify whether an acute bout of ultra-endurance exercise modifies the need for nutritive antioxidants, we aimed (1) to investigate the changes of endogenous and exogenous antioxidants in response to an Ironman triathlon; (2) to particularise the relevance of antioxidant responses to the indices of oxidatively damaged blood lipids, blood cell compounds and lymphocyte DNA and (3) to examine whether potential time-points of increased susceptibility to oxidative damage are associated with alterations in the antioxidant status. Blood that was collected from forty-two well-trained male athletes 2 d pre-race, immediately post-race, and 1, 5 and 19 d later was sampled. The key findings of the present study are as follows: (1) Immediately post-race, vitamin C, α-tocopherol, and levels of the Trolox equivalent antioxidant capacity, the ferric reducing ability of plasma and the oxygen radical absorbance capacity (ORAC) assays increased significantly. Exercise-induced changes in the plasma antioxidant capacity were associated with changes in uric acid, bilirubin and vitamin C. (2) Significant inverse correlations between ORAC levels and indices of oxidatively damaged DNA immediately and 1 d post-race suggest a protective role of the acute antioxidant responses in DNA stability. (3) Significant decreases in carotenoids and γ-tocopherol 1 d post-race indicate that the antioxidant intake during the first 24 h of recovery following an acute ultra-endurance exercise requires specific attention. Furthermore, the present study illustrates the importance of a diversified and well-balanced diet to maintain a physiological antioxidant status in ultra-endurance athletes in reference to recommendations.

Extra-virgin olive oils (EVOO), high in phenolic compounds with antioxidant properties, could be partly responsible for the lower mortality and incidence of cancer and CVD in the Mediterranean region. The present study aims to measure oxidative DNA damage in healthy human subjects consuming olive oils with different concentrations of natural phenols. A randomised cross-over trial of high-phenol EVOO (high-EVOO; 592mg total phenols/kg) V low-phenol EVOO (low-EVOO; 147mg/kg) was conducted in ten postmenopausal women in Florence. Subjects were asked to substitute all types of fat and oils habitually consumed with the study oil (50g/d) for 8 weeks in each period. Oxidative DNA damage was measured by the comet assay in peripheral blood lymphocytes, collected at each visit during the study period. Urine samples over 24h were collected to measure the excretion of the olive oil phenols. The average of the four measurements of oxidative DNA damage during treatment with high-EVOO was 30% lower than the average during the low-EVOO treatment (p=0·02). Urinary excretion of hydroxytyrosol and its metabolite homovanillyl alcohol were significantly increased in subjects consuming high-EVOO. Despite the small sample size, the present study showed a reduction of DNA damage by consumption of an EVOO rich in phenols, particularly hydroxytyrosol.

Probiotics reduce the risk of colon cancer by inhibiting carcinogen-induced DNA damage in animals, but there are no analogous data in human subjects. To enhance knowledge of the effects of probiotics in human subjects, we have investigated the genotoxicity of faecal water after dietary intervention with standard yoghurt or with probiotic yoghurt, which included the strains Lactobacillus acidophilus 145 and Bifidobacterium longum 913. Faeces were collected from nine healthy volunteers after intervention with probiotic yoghurt or standard yoghurt. Faecal water was isolated and incubated with human colon tumour cells HT29clone19A. DNA strand breaks, oxidised DNA bases and damage after challenge with H2O2 were determined by micro-gel-electrophoresis. Faecal water was genotoxic in comparison with NaCl, but protected against H2O2-induced DNA strand breaks. The intervention with probiotic yoghurt significantly lowered faecal water genotoxicity compared with standard yoghurt. However, probiotic intervention also increased oxidative damage; this either reflected prooxidative activity or stimulation of endogenous defence systems. Altogether, the balance of effects favoured protection, since faecal water from the probiotic group reduced overall genetic damage. Thus, there was a reduction of strand break-inducing compounds in human faeces after dietary intervention with probiotic bacteria. This protection reflected results from previous studies in carcinogen-exposed animals where probiotics reduced DNA damage in colon cells.

The effect of 4-coumaric and 3,4-dihydroxybenzoic (protocatechuic) acid on the basal oxidative DNA damage of rat colonic mucosa in vivo was studied, relative to vitamin E. F344 rats were treated with 4-coumaric or protocatechuic acid mixed in the diet (25 or 50 mg/kg for 2 weeks). It was observed that 4-coumaric acid (50 mg/kg) significantly decreased the basal level of the oxidative damage assessed as 8-OH-2′-deoxyguanosine levels in DNA and by the comet assay. Moreover, it was found that vitamin E (10 mg/kg) had no effect on colonic mucosa oxidation damage, whereas at a higher dose (55 mg/kg) it actually enhanced oxidative stress. The effect of 4-coumaric acid (50 mg/kg) on the expression of some glutathione-related enzymes (glutathione-S-transferase (GST)-P, GST-M2, GST-M1, γ-glutamylcysteine synthetase, glutathione peroxidase (GSPX)1 and GSPX4) was also investigated at the level of the colonic mucosa. Only the expression of GST-M2 was significantly induced by 4-coumaric acid, while protocatechuic acid was inactive. The data suggest that 4-coumaric acid acts as an antioxidant in the colonic mucosa in vivo.

The effect of dietary intake of flavonols (predominantly quercetin) on oxidative DNA damage was studied in thirty-six healthy human subjects (sixteen men, twenty women). The study was a randomised crossover study, comprising two 14 d treatments of either a low-flavonol (LF) or high-flavonol (HF) diet with a 14 d wash-out period between treatments. Subjects were asked to avoid foods containing flavonols, flavones and flavanols during the LF dietary treatment period and to consume one 150 g onion (Allium cepa) cake (containing 89·7 mg quercetin) and one 300 ml cup of black tea (containing 1·4 mg quercetin) daily during the HF dietary treatment. A 7 d food diary was kept during each dietary period and blood samples were taken after each dietary treatment. Products of oxidative damage to DNA bases were measured in DNA from leucocytes. The study had more than 95 % power to detect a change of 20 % in DNA damage products Plasma vitamin C and plasma quercetin concentrations were also measured. No significant differences in intake of macronutrients or assessed micronutrients, measured DNA base damage products, or plasma vitamin C were found between the HF and LF dietary treatments. The plasma quercetin concentration was significantly higher after the HF dietary treatment period (228·5 (SEM 34·7) nmol/l) than after the LF dietary treatment period (less than the limit of detection, i.e. <66·2 nmol/l). These findings do not support the hypothesis that dietary quercetin intake substantially affects oxidative DNA damage in leucocytes.