Cruciferous vegetables and cancer risk in a network of case-control studies.

BACKGROUND: Cruciferous vegetables have been suggested to protect against various cancers, though the issue is open to discussion. To further understand their role, we analyzed data from a network of case-control studies conducted in Italy and Switzerland. PATIENTS AND METHODS: The studies included a total of 1468 cancers of the oral cavity/pharynx, 505 of the esophagus, 230 of the stomach, 2390 of the colorectum, 185 of the liver, 326 of the pancreas, 852 of the larynx, 3034 of the breast, 367 of the endometrium, 1031 of the ovary, 1294 of the prostate, 767 of the kidney, and 11,492 controls. All cancers were incident, histologically confirmed; controls were subjects admitted to the same network of hospitals as cases for a wide spectrum of acute nonneoplastic conditions. RESULTS: The multivariate odds ratio (OR) for consumption of cruciferous vegetables at least once a week as compared with no/occasional consumption was significantly reduced for cancer of the oral cavity/pharynx (OR=0.83), esophagus (OR=0.72), colorectum (OR=0.83), breast (OR=0.83), and kidney (OR=0.68). The OR was below unity, but not significant, for stomach (OR=0.90), liver (OR=0.72), pancreatic (OR=0.90), laryngeal (OR=0.84), endometrial (OR=0.93), ovarian (OR=0.91), and prostate (OR=0.87) cancer. CONCLUSION: This large series of studies provides additional evidence of a favorable effect of cruciferous vegetables on several common cancers.

The total antioxidant capacity of the diet is an independent predictor of plasma beta-carotene.

OBJECTIVE: To investigate the contribution of the total antioxidant capacity (TAC) of the diet to plasma concentrations of beta-carotene. DESIGN: Cross-sectional study. SETTING: Department of Public Health and Department of Internal Medicine and Biomedical Sciences, University of Parma. SUBJECTS: A total of 247 apparently healthy adult men (n=140) and women (n=107). METHODS: A medical history, a physical exam including height, weight, waist circumference and blood pressure measurements, a fasting blood draw, an oral glucose tolerance test and a 3-day food record. RESULTS: We observe a negative trend across quartiles of plasma beta-carotene for most biological variables clustering in the insulin resistance syndrome, as well as for traditional and new risk factors for type II diabetes and cardiovascular disease (CVD), including C-reactive protein and gamma-glutamyltranspeptidase (P<0.05). Regarding dietary characteristics, energy-adjusted intake of fat, fiber, fruits, vegetables, beta-carotene, vitamin C, vitamin E and dietary TAC significantly increased with increasing plasma beta-carotene (P<0.05), whereas alcohol intake decreased (P=0.013). Adjusted geometric means (95% confidence interval) of plasma beta-carotene significantly increased across quartiles of dietary TAC, even when single dietary antioxidants were considered in the model (QI=0.087 mg/dl (0.073-0.102); QII=0.087 mg/dl (0.075-0.103); QIII=0.114 mg/dl (0.098-0.132) and QIV=0.110 mg/dl (0.093-0.130); P for linear trend=0.026). When the population was divided on the basis of alcohol consumption, this trend was also observed in subjects drinking <20 g alcohol/day (P=0.034), but not in those with higher alcohol intake (P=0.448). CONCLUSIONS: Dietary TAC is an independent predictor of plasma beta-carotene, especially in moderate alcohol drinkers. This may explain, at least in part, the inverse relationship observed between plasma beta-carotene and risk of chronic diseases associated to high levels of oxidative stress (i.e., diabetes and CVD), as well as the failure of beta-carotene supplements alone in reducing such risk.

Comparison between daidzein and genistein antioxidant activity in primary and cancer lymphocytes.

The main objective of this study was to compare the protective effect of daidzein and genistein against induced oxidative damage in Jurkat T-cell line and in peripheral blood lymphocytes of healthy subjects. After supplementation of cells with isoflavones (from 2.5 to 20micromol/L in Jurkat T-cell and from 0.01 to 2.5micromol/L in primary lymphocytes, 24h), we determined DNA damage induced by hydrogen peroxide using the comet assay and lipid peroxidation evaluating malondialdehyde (MDA) production after ferrous ion treatment. Supplementation of Jurkat cells and primary lymphocytes with both isoflavones significantly increased DNA protection from oxidative damage at concentrations between 0.1 and 5micromol/L (P<0.05), and with just daidzein, at concentrations higher than 2.5micromol/L, there was a decrease in the production of MDA (P<0.05). Our results seem to support that daidzein is just as effective as genistein in protecting cells against oxidative damage especially with respect to DNA. Moreover, since the protective effect was found at concentrations reachable in plasma after soy consumption (less than 2micromol/L), it can be assumed that the antioxidant activity of isoflavones could really contribute to the healthy properties of soy.

Lycopene and vitamin C concentrations increase in plasma and lymphocytes after tomato intake. Effects on cellular antioxidant protection.

OBJECTIVE: This study seeks to verify whether the regular consumption of small amounts of tomato products can protect lymphocyte DNA and lipids from oxidative damage. DESIGN: Standardized dietary intervention. SUBJECTS: Twelve healthy female subjects (mean age 25.2 y). INTERVENTION: Subjects were instructed to follow a standardized diet for 1 week, followed by 3 weeks consumption of the same diet enriched with small amounts of different tomato products providing as a mean 8 mg lycopene, 0.5 mg beta-carotene and 11 mg vitamin C per day. Plasma and lymphocyte concentrations of carotenoids, vitamin C and vitamin E were analysed. Ex vivo protection of lymphocyte DNA from oxidative injury produced by iron ions was evaluated by means of the Comet assay, and lipid peroxidation by HPLC analysis of malondialdehyde (MDA). RESULTS: Dietary intervention with tomato products increased lycopene concentration both in plasma (P < 0.001) and lymphocytes (P < 0.01). Vitamin C concentrations increased by approximately 35% in plasma (P < 0.05) and by approximately 230% in lymphocytes (P < 0.005). Vitamin E decreased significantly in plasma (P < 0.0001) but not in lymphocytes. Finally, there was an improved protection from DNA oxidative damage (P < 0.05) with no significant effect on MDA levels. CONCLUSIONS: Our results suggest that tomato products are not only good sources of lycopene but also sources of bioavailable vitamin C. A Regular intake of small amounts of tomato products can increase cell protection from DNA damage induced by oxidant species. This effect may originate from the synergism of different antioxidants present in tomatoes.

Black tea extract supplementation decreases oxidative damage in Jurkat T cells.

The purpose of this study was to investigate the protective effect of black tea (BT) extract against induced oxidative damage in Jurkat T-cell line. Cells supplemented with 10 or 25 mg/L BT were subjected to oxidation with ferrous ions. Malondialdehyde (MDA) production as marker of lipid peroxidation, DNA single strand breaks as marker of DNA damage, and modification of the antioxidant enzyme activity, glutathione peroxidase (GPX) were measured. Results show the efficacy of BT polyphenols to decrease DNA oxidative damage and to affect GPX activity (P<0.05), while no effect was shown on MDA production. The succeeding investigation of the activity of caffeine and epigallocatechin gallate demonstrated their antioxidant potential with respect to the cellular markers evaluated. In conclusion, this study supports the protective effect of BT against ferrous ions induced oxidative damage to DNA and the ability of BT to affect the enzyme antioxidant system of Jurkat cells.

Tomato consumption does not affect the total antioxidant capacity of plasma.

This study was performed to evaluate the effect of tomato intake on total antioxidant activity of plasma measured by the radical trapping antioxidant parameter assay in 11 healthy female subjects. After 7 d of a diet low in carotenoids and free from lycopene, subjects ate 25 g tomato puree daily (containing 7.0 mg lycopene and 0.25 mg beta-carotene) for 14 consecutive days. At the beginning and end of tomato supplementation, the carotenoid plasma concentration and the total antioxidant activity of plasma were assessed. Before tomato puree consumption, mean +/- SE total lycopene and beta-carotene plasma concentrations were 0.13 +/- 0.02 micromol/L and 0.24 +/- 0.04 micromol/L, respectively. After tomato puree supplementation, both concentrations increased significantly (0.57 +/- 0.06 micromol/L, P < 0.0001 for total lycopene, and 0.31 +/- 0. 04 micromol/L, P = 0.0036 for beta-carotene); however, total plasma antioxidant capacity values did not change significantly. From our results, intake of a food rich in carotenoids does not seem to modify the antioxidant capacity of plasma as evaluated by the radical trapping antioxidant parameter assay.

Lymphocyte lycopene concentration and DNA protection from oxidative damage is increased in women after a short period of tomato consumption.

Several epidemiologic studies have suggested a role of tomato products in protecting against cancer and chronic diseases. In nine adult women, we evaluated whether the consumption of 25 g tomato puree (containing 7 mg lycopene and 0.3 mg beta-carotene) for 14 consecutive days increased plasma and lymphocyte carotenoid concentration and whether this was related to an improvement in lymphocyte resistance to an oxidative stress (500 micromol/L hydrogen peroxide for 5 min). Before and after the period of tomato intake, carotenoid concentrations were analyzed by HPLC and lymphocyte resistance to oxidative stress by the Comet assay, which detects DNA strand breaks. Intake of tomato puree increased plasma (P <0.001) and lymphocyte (P<0.005) lycopene concentration and reduced lymphocyte DNA damage by approximately 50% (P<0.0001). Beta-carotene concentration increased in plasma (P<0.05) but not in lymphocytes after tomato puree consumption. An inverse relationship was found between plasma lycopene concentration (r = -0.82, P<0.0001) and lymphocyte lycopene concentration (r = -0.62, P<0.01) and the oxidative DNA damage. In conclusion, small amounts of tomato puree added to the diet over a short period can increase carotenoid concentrations and the resistance of lymphocytes to oxidative stress.

Supplementation of Jurkat T cells with green tea extract decreases oxidative damage due to iron treatment.

Regular tea consumption has been associated with a reduced risk of cancer. As demonstrated in vitro, green tea contains catechins with antioxidant properties. We evaluated the effect of the supplementation of the Jurkat T-cell line with green tea extract on oxidative damage. Cells grown in medium with or without green tea extract (10 mg/L) were treated with Fe(2+) (100 micromol/L) as an oxidative stimulus for 2 h. Cell membrane lipid peroxidation was evaluated by fatty acids pattern analysis and malondialdehyde production in alpha-linolenic acid-loaded cells. Furthermore, oxidative DNA damage (single strand breaks) was detected in cells by the Comet assay and quantified as relative tail moment (RTM). Supplementation with green tea extract significantly decreased malondialdehyde production (1.6 +/- 0.3 vs. 0.6 +/- 0.1 nmol/mg protein, P < 0.05) and DNA damage (0.32 +/- 0.07 vs. 0.12 +/- 0.04 RTM, P < 0.05) after Fe(2+) oxidative treatment. In control cells, there was no effect on membrane distribution of (n-3) fatty acids due to Fe(2+) treatment. Cell enrichment with alpha-linolenic acid increased total membrane (n-3) fatty acids. However, the oxidative treatment did not modify the distribution of polyunsaturated fatty acids. It is likely that the observed protective effects can be attributed to epigallocatechin gallate, which is present mainly (670 g/kg) in green tea extract; however, we cannot exclude contributions by other catechins. These data support a protective effect of green tea against oxidative damage.