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      Green Tea Consumption and Risk of Breast Cancer and Recurrence—A Systematic Review and Meta-Analysis of Observational Studies

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          Abstract

          Breast cancer (BC) is the most common cancer in women and several factors are involved in its onset. Green tea (GT) has been shown to have potential beneficial effects on different types of cancer. The aim of this review was to evaluate the association between GT regular consumption and risk of BC in women. The risk of BC recurrence and risk of BC in relation to menopausal status were also evaluated. A literature search of PubMed, Scopus, and Web of Science was conducted. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to perform the systematic review and meta-analysis. Full texts were downloaded for 40 studies; however, only 13 records were included in the meta-analysis. Eight were cohort studies and five were case-control studies. The pooled sample consisted of 163,810 people. An inverse statistically significant relationship between GT and BC risk, with an Odds Ratio (OR) = 0.85 ((95% CI = 0.80–0.92), p = 0.000)), was found. Egger’s linear regression test did not show a potential publication bias (intercept 0.33, t = 0.40, p = 0.695), which was also confirmed by the symmetry of the funnel plot. Moreover, no high statistical heterogeneity (Chi 2 = 31.55, df = 13, I 2 = 58.79%, p = 0.003) was found. The results of this meta-analysis showed a potential protective effect of GT consumption on BC, especially for BC recurrence.

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          A review of latest research findings on the health promotion properties of tea.

          Important progress has been made in the past five years concerning the effects of green and black tea on health. Experimentation with new accurate tools provide useful information about the metabolism of tea components in the body, their mode of action as antioxidants at the cellular level and their protective role in the development of cancer, cardiovascular disease and other pathologies. The use of tea components as nutraceuticals and functional foods are also discussed.
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            Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis

            Objective To evaluate the association of chocolate consumption with the risk of developing cardiometabolic disorders. Design Systematic review and meta-analysis of randomised controlled trials and observational studies. Data sources Medline, Embase, Cochrane Library, PubMed, CINAHL, IPA, Web of Science, Scopus, Pascal, reference lists of relevant studies to October 2010, and email contact with authors. Study selection Randomised trials and cohort, case-control, and cross sectional studies carried out in human adults, in which the association between chocolate consumption and the risk of outcomes related to cardiometabolic disorders were reported. Data extraction Data were extracted by two independent investigators, and a consensus was reached with the involvement of a third. The primary outcome was cardiometabolic disorders, including cardiovascular disease (coronary heart disease and stroke), diabetes, and metabolic syndrome. A meta-analysis assessed the risk of developing cardiometabolic disorders by comparing the highest and lowest level of chocolate consumption. Results From 4576 references seven studies met the inclusion criteria (including 114 009 participants). None of the studies was a randomised trial, six were cohort studies, and one a cross sectional study. Large variation was observed between these seven studies for measurement of chocolate consumption, methods, and outcomes evaluated. Five of the seven studies reported a beneficial association between higher levels of chocolate consumption and the risk of cardiometabolic disorders. The highest levels of chocolate consumption were associated with a 37% reduction in cardiovascular disease (relative risk 0.63 (95% confidence interval 0.44 to 0.90)) and a 29% reduction in stroke compared with the lowest levels. Conclusions Based on observational evidence, levels of chocolate consumption seem to be associated with a substantial reduction in the risk of cardiometabolic disorders. Further experimental studies are required to confirm a potentially beneficial effect of chocolate consumption.
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              Influence of Drinking Green Tea on Breast Cancer Malignancy among Japanese Patients

              Inhibitory effects of green tea on carcinogenesis have been investigated in numerous laboratory studies using (–)‐epigallocatechin gallate (EGCG) or crude green tea extract, and there is also some epidemiologic evidence. Further, EGCG has been reported to inhibit the growth of cancer cells, lung metastasis in an animal model, and urokinase activity. In this study, we first examined the association between consumption of green tea prior to clinical cancer onset and various clinical parameters assessed at surgery among 472 patients with stage I, II, and III breast cancer. We found that increased consumption of green tea was closely associated with decreased numbers of axillary lymph node metastases among premenopausal patients with stage I and II breast cancer and with increased expression of progesterone receptor (PgR) and estrogen receptor (ER) among postmenopausal ones. Since these are potential prognostic factors, we then investigated the prognosis of breast cancer with special reference to consumption of green tea, in a follow‐up study of these patients. We found that increased consumption of green tea was correlated with decreased recurrence of stage I and II breast cancer (P<0.05 for crude disease‐free survival); the recurrence rate was 16.7 or 24.3% among those consuming ≥5 cups or ≥4 cups per day, respectively, in a seven‐year follow‐up of stage I and II breast cancer, and the relative risk of recurrence was 0.564 (95% confidence interval, 0.350–0.911) after adjustment for other lifestyle factors. However, no improvement in prognosis was observed in stage III breast cancer. Our results indicate that increased consumption of green tea prior to clinical cancer onset is significantly associated with improved prognosis of stage I and II breast cancer, and this association may be related to a modifying effect of green tea on the clinical characteristics of the cancer.
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                Author and article information

                Journal
                Nutrients
                Nutrients
                nutrients
                Nutrients
                MDPI
                2072-6643
                03 December 2018
                December 2018
                : 10
                : 12
                : 1886
                Affiliations
                [1 ]Post-Graduate School of Hygiene and Preventive Medicine, Department of Experimental Medicine, University of Perugia, P.le L. Severi 1, 06132 Perugia, Italy
                [2 ]Digestive Endoscopy Unit, Veneto Institute of Oncology IOV-IRCCS, Via Gattamelata 64, 35128 Padua, Italy; stefano.realdon@ 123456iov.veneto.it
                [3 ]Department of Pharmaceutical Science, University of Perugia, Via del Giochetto 2, 06123 Perugia, Italy; angela.abalsamo@ 123456yahoo.it (A.A); mattia.acito@ 123456studenti.unipg.it (M.A.); milena.villarini@ 123456unipg.it (M.V.); massimo.moretti@ 123456unipg.it (M.M.)
                Author notes
                [* ]Correspondence: vincenza.gianfredi@ 123456studenti.unipg.it (V.G.); daniele.nucci@ 123456iov.veneto.it (D.N.); Tel.: +39-075-585-7488 (V.G.); +39-049-8221-1719 (D.N.); Fax: +39-075-585-7422 (V.G.)
                [†]

                These two authors equally contributed to the manuscript.

                Author information
                https://orcid.org/0000-0003-3848-981X
                https://orcid.org/0000-0003-4546-213X
                https://orcid.org/0000-0003-2885-0894
                https://orcid.org/0000-0003-1808-1999
                https://orcid.org/0000-0002-8769-883X
                https://orcid.org/0000-0002-5038-8619
                https://orcid.org/0000-0001-6843-7637
                Article
                nutrients-10-01886
                10.3390/nu10121886
                6316745
                30513889
                6ddcf97e-477e-4a6e-9c51-a8304fa5381b
                © 2018 by the authors.

                Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 10 November 2018
                : 28 November 2018
                Categories
                Review

                Nutrition & Dietetics
                breast cancer risk,green tea,epigallocatechin,women,cancer recurrence,camellia sinensis,meta-analysis

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