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The association between green tea consumption and breast cancer risk: A systematic review and meta-analysis.
Najaf Najafi, M, Salehi, M, Ghazanfarpour, M, Hoseini, ZS, Khadem-Rezaiyan, M
Phytotherapy research : PTR. 2018;(10):1855-1864
Abstract
This systematic review and meta-analysis aimed to critically evaluate the relation between green tea (GT) consumption and the risk of breast cancer. Popular electronic databases were systematically searched for papers in English language. All case-control and cohort studies in addition to randomized clinical trials were included if they assessed the chemopreventive effects of GT on breast cancer. The quality of included studies was assessed using the Newcastle-Ottawa and Jadad scale. This systematic review comprised 14 studies: 9 case-control studies, 4 cohort studies, and 1 clinical trial. Odds ratio (OR) in case-control studies suggested that women in the group receiving the highest level of GT had 19% reduction in breast cancer risk compared with those who received the lowest level of GT (summary OR = 0.81, p = .031; 95% CI [0.66, 0.981]; heterogeneity, I2 = 71.53, p < .001, random effect model; 9 studies). OR in cohort studies also showed no significant difference (OR = 0.99, p = .94; 95% CI [0.81, 1.138]; heterogeneity, I2 = 19.06, p = .29; fixed-effect model; 4 studies). According to the only clinical trial, treatment with GT could not alter the mammographic density compared with placebo (26% vs. 25%). It cannot be concluded that GT consumption may decrease the risk of breast cancer. Due to high heterogeneity, a pooled analysis of case-control and cohort studies was not performed.
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[Efficacy of lycopene intake in primary prevention of prostate cancer: a systematic review of the literature and meta-analysis.].
Cataño, JG, Trujillo, CG, Caicedo, JI, Bravo-Balado, A, Robledo, D, Mariño-Alvarez, AM, Pedraza, A, Arcila, MJ, Plata, M
Archivos espanoles de urologia. 2018;(2):187-197
Abstract
OBJECTIVE To evaluate the efficacy of lycopene intake in primary prevention of prostate cancer (PCa). METHODS A systematic search of the literature was conducted in March 2015 and the articles published between the years 1990-2015 were reviewed. The following search terms were used: prostate cancer, prostatic neoplasm, lycopene, prevention, effectiveness and efficacy (MeSH). Publications including research in humans, written in English and whose texts were accessible were reviewed. The types of studies included were: clinical trials, cohort and case-control studies. We found 343 articles; of these, 27 were included in the systematic review. After the latter were rigorously analyzed, 23 were included in the meta-analysis using the pooled odds ratios (OR) and risk ratios (RR) of case-control and cohort studies, respectively, and their confidence intervals (95% CI), using random-effects models with Review Manager 5.2. RESULTS Out of the 27 articles included in the systematic review, 22 were case-control and 5 were cohort studies. For the case-control studies, the total number of patients with PCa was 13,999 and the total number of controls 22,028. Cohort studies included 187,417 patients and PCa was diagnosed in 8,619 of these. The metaanalysis determined an OR = 0.94 (IC 95% 0.89-1.00) and RR = 0.9 (IC 95% 0.85-0.95) of PCa related with lycopene and/or raw or cooked tomatoes intake. CONCLUSIONS Although our study found that there is a statistically significant inverse association between lycopene intake and PCa, the magnitude of this association is weak and comes solely from observational studies, which do not allow recommending its use as a standard of practice. High-quality randomized clinical trials are required to clarify current evidence.
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Soy Consumption and the Risk of Prostate Cancer: An Updated Systematic Review and Meta-Analysis.
Applegate, CC, Rowles, JL, Ranard, KM, Jeon, S, Erdman, JW
Nutrients. 2018;(1)
Abstract
Prostate cancer (PCa) is the second most commonly diagnosed cancer in men, accounting for 15% of all cancers in men worldwide. Asian populations consume soy foods as part of a regular diet, which may contribute to the lower PCa incidence observed in these countries. This meta-analysis provides a comprehensive updated analysis that builds on previously published meta-analyses, demonstrating that soy foods and their isoflavones (genistein and daidzein) are associated with a lower risk of prostate carcinogenesis. Thirty articles were included for analysis of the potential impacts of soy food intake, isoflavone intake, and circulating isoflavone levels, on both primary and advanced PCa. Total soy food (p < 0.001), genistein (p = 0.008), daidzein (p = 0.018), and unfermented soy food (p < 0.001) intakes were significantly associated with a reduced risk of PCa. Fermented soy food intake, total isoflavone intake, and circulating isoflavones were not associated with PCa risk. Neither soy food intake nor circulating isoflavones were associated with advanced PCa risk, although very few studies currently exist to examine potential associations. Combined, this evidence from observational studies shows a statistically significant association between soy consumption and decreased PCa risk. Further studies are required to support soy consumption as a prophylactic dietary approach to reduce PCa carcinogenesis.
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Non-herbal tea consumption and ovarian cancer risk: a systematic review and meta-analysis of observational epidemiologic studies with indirect comparison and dose-response analysis.
Zhang, D, Kaushiva, A, Xi, Y, Wang, T, Li, N
Carcinogenesis. 2018;(6):808-818
Abstract
Ovarian cancer (OC) accounts for 4% of female malignancies worldwide, and its prognosis is unfavorable. Currently available epidemiologic data suggest that non-herbal tea consumption may reduce OC risk, but these evidences are inconsistent. A comprehensive literature search for observational epidemiologic studies reporting associations between non-herbal tea consumption and OC risk was conducted in electronic databases. A random-effects model was used to synthesize effect measures in binary meta-analysis, and adjusted indirect comparison was used to compare whether there was a difference in effects between green tea (GT) and black tea (BT). Both linear and non-linear models were used to explore the dose-response relationship. Fourteen studies were included, and we obtained an inverse and significant pooled estimate in binary meta-analysis [risk ratio (RR)pool = 0.76, 95% confidence interval (CI) 0.61-0.95, PCochran < 0.001, I2 = 81.5%]. No publication bias was identified in binary meta-analysis. In binary meta-analysis stratified by tea types, we observed a significant association for GT (RRpool = 0.64, 95% CI 0.45-0.90, PCochran = 0.071, I2 = 53.6%), but not BT (RRpool = 0.85, 95% CI 0.65-1.12, PCochran = 0.007, I2 = 65.9%). Indirect comparison, which treated BT as the reference, showed an inverse but non-significant association (RRGT versus BT = 0.74, 95% CI 0.48-1.15). Both linear and non-linear models found that OC risk decreased as the consumption levels of total non-herbal tea increased. However, the dose-response relationship was stronger for GT when compared with BT. Our results suggest that non-herbal tea, especially GT, is associated with a reduced risk of OC. Future studies should explore biochemical evidence regarding the variation in chemopreventive effects between different types of non-herbal tea.
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Calcium as a chemopreventive agent against colorectal neoplasm: does obesity play a role?
Keum, N, Kim, H, Giovannucci, EL
Cancer causes & control : CCC. 2017;(8):853-856
Abstract
BACKGROUND Concerning the chemopreventive potential of calcium against colorectal neoplasms, strong evidence from initial randomized controlled trials (RCTs) of colorectal adenoma has not been confirmed from the most recent large RCT. To explain the conflicting results, a new hypothesis was proposed that the benefit of calcium may be confined to lean individuals. METHODS To test this hypothesis, we examined heterogeneity of the associations of calcium intake with adenoma and CRC, using data from the most recent meta-analyses of observational studies and conducting subgroup analysis by average body mass index (BMI) of study population. RESULTS An inverse association of calcium intake with adenoma and CRC did not vary by population average BMI. By anatomical subsites of CRC, while there was no significant evidence of heterogeneity by population average BMI (P heterogeneity > 0.05), the benefit of calcium was confined to studies with population average BMI of ≥25 kg/m2 for both colon cancer and rectal cancer, contradicting the hypothesis. CONCLUSIONS In our study-level meta-analysis, we found no evidence to support that the chemopreventive potential of calcium, if real, may be stronger in leaner individuals.
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Lycopene Consumption and Risk of Colorectal Cancer: A Meta-Analysis of Observational Studies.
Wang, X, Yang, HH, Liu, Y, Zhou, Q, Chen, ZH
Nutrition and cancer. 2016;(7):1083-96
Abstract
A number of epidemiological studies have explored the association between lycopene or lycopene-rich food intake and the risk of colorectal cancer, but the results of these studies have not been consistent. We conducted a systematic review and meta-analysis of studies published in the PubMed and EMBASE databases to quantitatively assess the association between lycopene consumption and the risk of colorectal cancer. A total of 15 studies were included in the meta-analysis, and the summary relative risk (RR) for highest versus lowest category indicated no significant association between lycopene consumption and the risk of colorectal cancer [RR = 0.94, 95% confidence interval (CI): 0.80-1.10]. However, a significant inverse association was observed between lycopene consumption and the site of cancer in the colon (RR = 0.88, 95% CI: 0.81-0.96). We also found that the incidence of colon cancer and lycopene intake did not exhibit dose-response relationships. The Grades of Recommendations Assessment, Development and Evaluation (GRADE) quality in our study was very low. In conclusion, this meta-analysis indicates that lycopene consumption is not associated with the risk of colorectal cancer. Further research will be needed in this area to provide conclusive evidence.
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Calcium supplementation for the prevention of colorectal adenomas: A systematic review and meta-analysis of randomized controlled trials.
Bonovas, S, Fiorino, G, Lytras, T, Malesci, A, Danese, S
World journal of gastroenterology. 2016;(18):4594-603
Abstract
AIM: To determine the efficacy of calcium supplementation in reducing the recurrence of colorectal adenomas. METHODS We conducted a systematic review and meta-analysis of published studies. We searched PubMed, Scopus, the Cochrane Library, the WHO International Clinical Trials Registry Platform, and the ClinicalTrials.gov website, through December 2015. Randomized, placebo-controlled trials assessing supplemental calcium intake for the prevention of recurrence of adenomas were eligible for inclusion. Two reviewers independently selected studies based on predefined criteria, extracted data and outcomes (recurrence of colorectal adenomas, and advanced or "high-risk" adenomas), and rated each trial's risk-of-bias. Between-study heterogeneity was assessed, and pooled risk ratio (RR) estimates with their 95% confidence intervals (95%CI) were calculated using fixed- and random-effects models. To express the treatment effect in clinical terms, we calculated the number needed to treat (NNT) to prevent one adenoma recurrence. We also assessed the quality of evidence using GRADE. RESULTS Four randomized, placebo-controlled trials met the eligibility criteria and were included. Daily doses of elemental calcium ranged from 1200 to 2000 mg, while the duration of treatment and follow-up of participants ranged from 36 to 60 mo. Synthesis of intention-to-treat data, for participants who had undergone follow-up colonoscopies, indicated a modest protective effect of calcium in prevention of adenomas (fixed-effects, RR = 0.89, 95%CI: 0.82-0.96; random-effects, RR = 0.87, 95%CI: 0.77-0.98; high quality of evidence). The NNT was 20 (95%CI: 12-61) to prevent one colorectal adenoma recurrence within a period of 3 to 5 years. On the other hand, the association between calcium treatment and advanced adenomas did not reach statistical significance (fixed-effects, RR = 0.92, 95%CI: 0.75-1.13; random-effects, RR = 0.92, 95%CI: 0.71-1.18; moderate quality of evidence). CONCLUSION Our results suggest a modest chemopreventive effect of calcium supplements against recurrent colorectal adenomas over a period of 36 to 60 mo. Further research is warranted.
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Folate intake and the risk of oral cavity and pharyngeal cancer: a pooled analysis within the International Head and Neck Cancer Epidemiology Consortium.
Galeone, C, Edefonti, V, Parpinel, M, Leoncini, E, Matsuo, K, Talamini, R, Olshan, AF, Zevallos, JP, Winn, DM, Jayaprakash, V, et al
International journal of cancer. 2015;(4):904-14
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Abstract
There are suggestions of an inverse association between folate intake and serum folate levels and the risk of oral cavity and pharyngeal cancers (OPCs), but most studies are limited in sample size, with only few reporting information on the source of dietary folate. Our study aims to investigate the association between folate intake and the risk of OPC within the International Head and Neck Cancer Epidemiology (INHANCE) Consortium. We analyzed pooled individual-level data from ten case-control studies participating in the INHANCE consortium, including 5,127 cases and 13,249 controls. Odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were estimated for the associations between total folate intake (natural, fortification and supplementation) and natural folate only, and OPC risk. We found an inverse association between total folate intake and overall OPC risk (the adjusted OR for the highest vs. the lowest quintile was 0.65, 95% CI: 0.43-0.99), with a stronger association for oral cavity (OR = 0.57, 95% CI: 0.43-0.75). A similar inverse association, though somewhat weaker, was observed for folate intake from natural sources only in oral cavity cancer (OR = 0.64, 95% CI: 0.45-0.91). The highest OPC risk was observed in heavy alcohol drinkers with low folate intake as compared to never/light drinkers with high folate (OR = 4.05, 95% CI: 3.43-4.79); the attributable proportion (AP) owing to interaction was 11.1% (95% CI: 1.4-20.8%). Lastly, we reported an OR of 2.73 (95% CI:2.34-3.19) for those ever tobacco users with low folate intake, compared with nevere tobacco users and high folate intake (AP of interaction =10.6%, 95% CI: 0.41-20.8%). Our project of a large pool of case-control studies supports a protective effect of total folate intake on OPC risk.
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Calcium intake and colorectal cancer risk: dose-response meta-analysis of prospective observational studies.
Keum, N, Aune, D, Greenwood, DC, Ju, W, Giovannucci, EL
International journal of cancer. 2014;(8):1940-8
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Abstract
Mechanistic and epidemiologic studies provide considerable evidence for a protective association between calcium intake and incident colorectal cancer (CRC). While the relationship has not been substantiated by short-duration randomized controlled trials (RCTs) of CRC, trials do show a benefit on adenomas, a precursor to CRC. To address some of this inconsistency, we conducted dose-response meta-analyses by sources of calcium intake, based on prospective observational studies published up to December 2013 identified from PubMed, Embase, and BIOSIS. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated using a random-effects model. For total calcium intake, each 300 mg/day increase was associated with an approximately 8% reduced risk of CRC (summary RR = 0.92, 95% CI = 0.89-0.95, I(2) = 47%, 15 studies with 12,305 cases, intake = 250-1,900 mg/day, follow-up = 3.3-16 years). While the risk decreased less steeply in higher range of total calcium intake (P(non-linearity) = 0.04), the degree of curvature was mild and statistical significance of non-linearity was sensitive to one study. For supplementary calcium, each 300 mg/day increase was associated with an approximately 9% reduced risk of CRC (summary RR = 0.91, 95% CI = 0.86-0.98, I(2) = 67%, six studies with 8,839 cases, intake = 0-1,150 mg/day, follow-up = 5-10 years). The test for non-linearity was not statistically significant (P(non-linearity) = 0.11). In conclusion, both dietary and supplementary calcium intake may continue to decrease CRC risk beyond 1,000 mg/day. Calcium supplements and non-dairy products fortified with calcium may serve as additional targets in the prevention of CRC. RCTs of calcium supplements with at least 10 years of follow-up are warranted to confirm a benefit of calcium supplements on CRC risk.
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Dietary fiber and the risk of precancerous lesions and cancer of the esophagus: a systematic review and meta-analysis.
Coleman, HG, Murray, LJ, Hicks, B, Bhat, SK, Kubo, A, Corley, DA, Cardwell, CR, Cantwell, MM
Nutrition reviews. 2013;(7):474-82
Abstract
Dietary fiber has several anticarcinogenic effects and is thought to be protective against esophageal cancer. The aim of this systematic review was to quantify the association between dietary fiber and the risk of esophageal cancer by investigating histological subtypes of esophageal cancer and the stage at which fiber may influence the carcinogenic pathway. Systematic search strategies were used to identify relevant studies, and adjusted odds ratios (ORs) were combined using random-effects meta-analyses to assess the risk of cancer when comparing extreme categories of fiber intake. Ten relevant case-control studies were identified within the timeframe searched. Pooled estimates from eight studies of esophageal adenocarcinoma revealed a significant inverse association with the highest fiber intakes (OR 0.66; 95% confidence interval [CI] 0.44-0.98). Two studies also identified protective effects of dietary fiber against Barrett's esophagus. Similar, though nonsignificant, associations were observed when results from five studies of fiber intake and risk of squamous cell carcinoma were combined (OR 0.61; 95%CI 0.31-1.20). Dietary fiber is associated with protective effects against esophageal carcinogenesis, most notably esophageal adenocarcinoma. Potential methods of action include modification of gastroesophageal reflux and/or weight control.