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Metabolic syndrome and liver-related events: a systematic review and meta-analysis.
Ren, H, Wang, J, Gao, Y, Yang, F, Huang, W
BMC endocrine disorders. 2019;19(1):40
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Liver cancer is one of the most common cancers worldwide and chronic liver disease a major cause of death in the US. Viral hepatitis and excessive alcohol intake are important risk factors, but do not explain many cases. Non-alcoholic fatty liver disease (NAFLD) is associated with insulin resistance and several metabolic abnormalities, suggesting a link between metabolic factors and cancer of the liver. This review and meta-analysis pooled data from 19 epidemiological studies, involving 1,561,457 participants, to evaluate the risk of metabolic syndrome for liver related events (LREs). 16 of the 19 studies showed an increased risk of LREs for people with metabolic syndrome, whilst 3 found a negative association. The meta-analysis found that people with metabolic syndrome had increased risks of 76% for liver cancer and of 421% for death from liver related causes. The risk of any LRE was increased by 49%. The risks were higher for people with hepatitis B infection and lower for people living in Asia. The authors state that the mechanisms are not fully understood and hypothesise that people with metabolic syndrome likely share risk factors for cancer, such as low physical activity, oxidative stress and dietary factors such as high caloric food, high fat and low fibre intake. The authors conclude that metabolic syndrome is an important risk factor for liver disease.
Abstract
BACKGROUND Previous studies have suggested that metabolic syndrome (MetS) and its component conditions are linked to the development of many benign or malignant diseases. Some studies have described relationships among metabolic syndrome or diabetes and liver cancer, but not many articles described the relationships between MetS and cirrhosis, acute hepatic failure, end-stage liver disease, and even death. However, liver cancers, cirrhosis, acute hepatic failure, end-stage liver disease, and liver-related mortality-collectively described as liver-related events (LREs)-may have different relationships with MetS. We undertook this meta-analysis to examine the association between MetS and LREs, and to determine whether geographic region or hepatitis B virus (HBV) positivity might influence the association. METHODS Relevant studies were identified from PubMed, EMBASE, and the Cochrane database. Two reviewers independently searched records from January 1980 to December 2017. The search terms included 'metabolic syndrome', 'diabetes mellitus', 'insulin resistance syndrome', and 'metabolic abnormalities', combined with 'cirrhosis', 'hepatic fibrosis ', 'hepatocellular carcinoma', 'complication', 'LRE', 'HCC', 'liver-related events', and 'liver cancer'. No language restriction was applied to the search. We chose the studies reporting an association between MetS and LREs. We used Begg's and Egger's tests and visually examined a funnel plot to assess publication bias. All analyses were conducted in Stata 14.0 software. RESULTS There were 19 studies (18 cohort and 1 case-control) included in the analysis, with a total of 1,561,457 participants. The subjects' ages ranged from 18 to 84 years. The combined analysis showed an overall 86% increase risk of LREs in cases with MetS (RR: 1.86,95% CI: 1.56-2.23). The funnel plot was asymmetrical, and the Egger's test p values showed a publication bias in this meta analysis. However, through the trim and fill method, we obtained a new RR value for LREs with MetS of 1.49 (95% CI: 1.40-1.58, p = 0.000). There was no obvious difference with the two answers, so we concluded that the results were robust. For hepatitis B positive patients, the RR for MetS and LREs was 2.15 (95% CI:1.02-4.53, p = 0.038), but for the hepatitis B negative patients, the RR was 1.85 (95% CI:1.53-2.24, p = 0.000). And for non-Asians, the RR for MetS and LREs was 2.21 (95% CI: 1.66-2.69, p = 0.000), while for Asians, the RR was 1.73 (95% CI: 1.35-2.22, p = 0.000). CONCLUSIONS This meta-analysis showed that MetS is associated with a moderately increased risk of LREs prevalence. Patients with MetS together with hepatitis B are more likely to develop hepatic events. For non-Asians, MetS is more likely to increase the incidence of LREs.
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Exposure to glyphosate-based herbicides and risk for non-Hodgkin lymphoma: A meta-analysis and supporting evidence.
Zhang, L, Rana, I, Shaffer, RM, Taioli, E, Sheppard, L
Mutation research. Reviews in mutation research. 2019;781:186-206
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Glyphosate is a highly effective broad-spectrum herbicide that is typically applied in mixtures known as glyphosate-based herbicides (GBHs). Glyphosate and its metabolites persist in food, water, and dust, potentially indicating that everyone may be exposed ubiquitously. The objective of this study was to focus on an a priori hypothesis - the highest biologically relevant exposure to GBHs, i.e., higher levels, longer durations and/or with sufficient lag and latency, will lead to increased risk of non-Hodgkin lymphoma (NHL) in humans. This study is a meta-analysis of six studies (one cohort and five case-control control studies) with almost 65,000 participants. Results demonstrated a significantly increased NHL risk in highly GBH-exposed individuals. Authors conclude that the overall evidence from human, animal, and mechanistic studies presented in this study, supports a compelling link between exposures to GBHs and increased risk for NHL.
Abstract
Glyphosate is the most widely used broad-spectrum systemic herbicide in the world. Recent evaluations of the carcinogenic potential of glyphosate-based herbicides (GBHs) by various regional, national, and international agencies have engendered controversy. We investigated whether there was an association between high cumulative exposures to GBHs and increased risk of non-Hodgkin lymphoma (NHL) in humans. We conducted a new meta-analysis that includes the most recent update of the Agricultural Health Study (AHS) cohort published in 2018 along with five case-control studies. Using the highest exposure groups when available in each study, we report the overall meta-relative risk (meta-RR) of NHL in GBH-exposed individuals was increased by 41% (meta-RR = 1.41, 95% confidence interval, CI: 1.13-1.75). For comparison, we also performed a secondary meta-analysis using high-exposure groups with the earlier AHS (2005), and we calculated a meta-RR for NHL of 1.45 (95% CI: 1.11-1.91), which was higher than the meta-RRs reported previously. Multiple sensitivity tests conducted to assess the validity of our findings did not reveal meaningful differences from our primary estimated meta-RR. To contextualize our findings of an increased NHL risk in individuals with high GBH exposure, we reviewed publicly available animal and mechanistic studies related to lymphoma. We documented further support from studies of malignant lymphoma incidence in mice treated with pure glyphosate, as well as potential links between glyphosate / GBH exposure and immunosuppression, endocrine disruption, and genetic alterations that are commonly associated with NHL or lymphomagenesis. Overall, in accordance with findings from experimental animal and mechanistic studies, our current meta-analysis of human epidemiological studies suggests a compelling link between exposures to GBHs and increased risk for NHL.
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Glycemic Index, Glycemic Load and Cancer Risk: An Updated Meta-Analysis.
Turati, F, Galeone, C, Augustin, LSA, La Vecchia, C
Nutrients. 2019;11(10)
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This 2019 meta-analysis is an update of an earlier 2015 study on the relationship between high Glycemic Index (GI) and Glycemic load (GL) diets and cancer risk. Twenty new epidemiological reports were added to the original seventy-five studies covering a total of 169,00 cancer cases. The theory is that elevated insulin levels, triggered by a high GI diet, increase bioactive chemicals which promote cancer development by inhibiting cell apoptosis and stimulating cell proliferation. This study collated cancers into 3 subgroups of hormonal cancers (breast, endometrium, ovary and prostate), digestive tract cancers (cancers, stomach, colorectum and pancreas) and other (lung, bladder and kidney). The combined results showed that the risk ratio for hormonal-related cancers and GI/GL were modestly elevated but not significant except for a possible moderate positive association between GL and endometrial cancer (RR1.12). There was a positive significant association between high GI intake and colorectal cancer risk (RR 1.20) but not with the other digestive-tract cancers. A high GI was associated with small increased risks of bladder (RR 1.25) and kidney (RR 1.16) cancers. The researchers conclude that the high number of studies and cancer types included provide high statistical power. Although the results show only moderate association this may be relevant at population level given the high incidence of cancers.
Abstract
Diets high in glycemic index (GI) and glycemic load (GL) have been related to an increased risk of selected cancers, but additional quantification is required. We updated a systematic review and meta-analysis published in 2015 to May 2019 to provide quantitative information on GI/GL and cancer risk. Relative risks (RR) and the corresponding 95 % confidence intervals (CI) for the highest versus the lowest categories of GI and GL were extracted from selected studies and pooled using random-effects models. Twenty reports (>22,000 cancer cases) have become available after January 2015, and 15 were added to the meta-analyses by cancer sites, which considered a total of 88 investigations. The five additional reports were reviewed, but not included in the meta-analyses, since data were inadequate to be pooled. For hormone-related cancers, summary RRs for the highest versus lowest GI and GL intakes were moderately increased. They ranged from 1.04 (breast) to 1.12 (endometrium) for GI and from 1.03 (prostate) to 1.22 (ovary) for GL, of borderline significance. High GI was associated with small increased risks of colorectal (summary RR for GI: 1.20, 95% CI, 1.07-1.34-GL: 1.09, 95% CI, 0.97-1.22, 19 studies), bladder (GI: 1.25, 95% CI, 1.11-1.41-GL: 1.10, 95% CI, 0.85-1.42, four studies) and kidney cancers (GI: 1.16, 95% CI, 1.02-1.32-GL: 1.14, 95% CI, 0.81-1.60, five studies). GL was not significantly related to those cancer sites. Stomach, prostate and lung cancers were not associated with GI and GL. The present analysis, based on an updated comprehensive evaluation of the epidemiological literature, indicates moderate unfavorable effects of high versus low GI on colorectal, and possibly bladder and kidney cancers, and a possible moderate positive association between GL and endometrial cancer.
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Association between intake of non-sugar sweeteners and health outcomes: systematic review and meta-analyses of randomised and non-randomised controlled trials and observational studies.
Toews, I, Lohner, S, Küllenberg de Gaudry, D, Sommer, H, Meerpohl, JJ
BMJ (Clinical research ed.). 2019;364:k4718
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Consumption of non-sugar sweeteners (NSS) has recently increased due to an emphasis on a low sugar diet. However, the exact health effects of this switch are uncertain. The aim of this systematic review and meta-analysis of 56 randomised and non-randomised trials aimed to determine the health effects of NSS’s in adults and children. The results showed that amongst adults body weight, blood sugar, daily energy intake, and blood pressure were all lower when exposed to NSS’s. Other health measures such as cancer and neurological disorders remained unaffected. Amongst children blood sugar was significantly higher and a small increase in body mass index was also observed when exposed to NSS’s. It was concluded that most health outcomes were unaffected by NSS’s, and there appears to be no health benefits on a broad range of outcomes when switching from sugar. Potential harm from regular NSS consumption could not be ruled out from this study. Healthcare professionals could use this study to understand that recommending diets which switch from sugar to NSS’s may have limited health benefits.
Abstract
OBJECTIVE To assess the association between intake of non-sugar sweeteners (NSS) and important health outcomes in generally healthy or overweight/obese adults and children. DESIGN Systematic review following standard Cochrane review methodology. DATA SOURCES Medline (Ovid), Embase, Cochrane CENTRAL, WHO International Clinical Trials Registry Platform, Clinicaltrials.gov, and reference lists of relevant publications. ELIGIBILITY CRITERIA FOR SELECTING STUDIES Studies including generally healthy adults or children with or without overweight or obesity were eligible. Included study designs allowed for a direct comparison of no intake or lower intake of NSS with higher NSS intake. NSSs had to be clearly named, the dose had to be within the acceptable daily intake, and the intervention duration had to be at least seven days. MAIN OUTCOME MEASURES Body weight or body mass index, glycaemic control, oral health, eating behaviour, preference for sweet taste, cancer, cardiovascular disease, kidney disease, mood, behaviour, neurocognition, and adverse effects. RESULTS The search resulted in 13 941 unique records. Of 56 individual studies that provided data for this review, 35 were observational studies. In adults, evidence of very low and low certainty from a limited number of small studies indicated a small beneficial effect of NSSs on body mass index (mean difference -0.6, 95% confidence interval -1.19 to -0.01; two studies, n=174) and fasting blood glucose (-0.16 mmol/L, -0.26 to -0.06; two, n=52). Lower doses of NSSs were associated with lower weight gain (-0.09 kg, -0.13 to -0.05; one, n=17 934) compared with higher doses of NSSs (very low certainty of evidence). For all other outcomes, no differences were detected between the use and non-use of NSSs, or between different doses of NSSs. No evidence of any effect of NSSs was seen on overweight or obese adults or children actively trying to lose weight (very low to moderate certainty). In children, a smaller increase in body mass index z score was observed with NSS intake compared with sugar intake (-0.15, -0.17 to -0.12; two, n=528, moderate certainty of evidence), but no significant differences were observed in body weight (-0.60 kg, -1.33 to 0.14; two, n=467, low certainty of evidence), or between different doses of NSSs (very low to moderate certainty). CONCLUSIONS Most health outcomes did not seem to have differences between the NSS exposed and unexposed groups. Of the few studies identified for each outcome, most had few participants, were of short duration, and their methodological and reporting quality was limited; therefore, confidence in the reported results is limited. Future studies should assess the effects of NSSs with an appropriate intervention duration. Detailed descriptions of interventions, comparators, and outcomes should be included in all reports. SYSTEMATIC REVIEW REGISTRATION Prospero CRD42017047668.
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Coffee Consumption and Risk of Colorectal Cancer: A Systematic Review and Meta-Analysis of Prospective Studies.
Sartini, M, Bragazzi, NL, Spagnolo, AM, Schinca, E, Ottria, G, Dupont, C, Cristina, ML
Nutrients. 2019;11(3)
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Coffee is the second most widely consumed drink worldwide, after water. It contains many active compounds that affect the health and functioning of the digestive tract. Previous population studies on the relationship between coffee consumption and cancer prevention have had mixed results. The aim of this systematic review and meta-analysis was to provide an up to date summary of the relationship between coffee consumption and the risk of colorectal cancer. The authors looked at 26 prospective studies. When results from the 26 studies were pooled, no significant relationship between coffee consumption and colorectal cancer was found. The researchers then looked at the results by ethnicity and found a protective effect for coffee on colorectal cancer in people from the US. For colon cancer, coffee was protective in men and women combined and in men alone, regardless of ethnicity. When the results were separated according to ethnicity, a significant protective effect was noted in European men and in Asian women. There was no association between coffee consumption and rectal cancer. Decaffeinated coffee demonstrated a protective effect against colorectal cancer in both men and women. The authors concluded that ethnicity could explain the mixed results of previous studies. Further research is needed into the relationship between a person’s genetic make-up and the risk of colorectal cancer associated with coffee.
Abstract
Coffee is a blend of compounds related to gastrointestinal physiology. Given its popularity and the epidemiology of colorectal cancer, the impact of this beverage on public health could be considerable. Our aim was to provide an updated synthesis of the relationship between coffee consumption and the risk of colorectal cancer. We conducted a systematic review and meta-analysis of 26 prospective studies. Regarding colorectal cancer, no significant relationship was detected. Stratifying for ethnicity, a protective effect emerged in US subjects. Concerning colon cancer, coffee proved to exert a protective effect in men and women combined and in men alone. Stratifying for ethnicity, a significant protective effect was noted in European men only and in Asian women only. Concerning rectal cancer, no association was found. Decaffeinated coffee exhibited a protective effect against colorectal cancer in men and women combined. Studies were appraised for their quality by means of the Newcastle-Ottawa Quality Assessment Scale for Cohort studies. Only one study proved to be of low quality. Ethnicity could explain the heterogeneity of the studies. However, little is known about the relationship between the genetic make-up and the risk of colorectal cancer associated with coffee. Further research is warranted.
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Effect of ω-3 polyunsaturated fatty acid-supplemented parenteral nutrition on inflammatory and immune function in postoperative patients with gastrointestinal malignancy: A meta-analysis of randomized control trials in China.
Zhao, Y, Wang, C
Medicine. 2018;97(16):e0472
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Omega-3 polyunsaturated fatty acids (PUFAs) can have a beneficial effect on inflammation and immune function. This meta-analysis looked at the effectiveness of omega-3 PUFAs on inflammatory and immune function in patients with stomach or colorectal cancers, following surgery. 16 Chinese randomised controlled trials with over 1000 patients carried out between 2000 and 2017 were included in the analysis. The researchers found that the numbers of immune cells in the omega-3 group were significantly higher than those in the control group. The levels of antibodies in people given omega-3 were significantly higher than those in the control group. Inflammatory markers in the omega-3 group were significantly lower. Those given omega-3 were 64% less likely to experience post-surgical infections. The result of this meta-analysis confirmed that supplementing gastrointestinal cancer patients with omega-3 improves post-surgery indicators of immune function, reduces inflammation, and reduces infections related to surgery. The authors recommend that omega-3 should be added to the nutrition formula given to gastrointestinal cancer patients following surgery.
Abstract
BACKGROUND There are no consensus regarding the efficacy of omega-3polyunsaturated fatty acids (PUFAs) on inflammatory and immune function in postoperative patients with gastrointestinal malignancy. METHODS The literatures published randomized control trials (RCT) were searched in PubMed, Embase, Scopus, Cochrane Library, CNKI, Weipu, and Wanfang Databases. The immune efficacy outcomes of ω-3 polyunsaturated fatty acid-supplemented parenteral nutrition in patients with gastrointestinal malignancy were compared. RESULTS Sixteen RCTs involving 1008 patients (506 in the omega-3 group, 502 in the control group) were enrolled into the analysis. The results of meta-analysis: the cell immunity: The proportions of CD3, CD4, CD4/CD8 in the omega-3 group were significantly higher than those in the control group (CD3: WMD = 4.48; 95% CI, 3.34-5.62; P < .00001; I = 0%; CD4: WMD = 5.55; 95% CI, 4.75-6.34; P < .00001; I = 0%; CD4/CD8: WMD = .28; 95% CI, 0.13-0.44; P = .0004; I = 81%). In the humoral immunity: The levels of IgA, IgM and IgG in the omega-3 group were significantly higher than those in the control group (IgA: WMD = 0.31; 95% CI, 0.25-0.37; P < .00001; I = 0%; IgM: WMD = 0.12; 95% CI, 0.06-1.81; P < .00001; I = 0%; IgG: WMD = 1.19; 95% CI, 0.80-1.58; P < .00001; I = 0%). The count of lymphocyte in the omega-3 group was significantly higher than that in the control group (WMD = 0.22; 95% CI, 0.12-0.33; P < .0001; I = 40%). In the postoperative inflammatory cytokine: The levels of interleukin-6, tumor necrosis factor (TNF)-α and C-reactive protein in the omega-3 group were significantly lower than those in the control group (IL-6: WMD = -3.09; 95% CI, -3.91 to 2.27; P < .00001; I = 45%; TNF-α: WMD = -1.65; 95% CI, -2.05 to 1.25; P < .00001; I = 28%; CRP: WMD = -4.28; 95% CI, -5.26 to 3.30; P < .00001; I = 37%). The rate of postoperative infective complications in the omega-3 group was significantly lower than that in the control group (OR = 0.36; 95% CI, 0.20-0.66; P = .0008; I = 0%). CONCLUSION This meta-kanalysis confirmed that early intervention with Omega -3 fatty acid emulsion in gastrointestinal cancer can not only improve the postoperative indicators of immune function, reduce inflammatory reaction, and improve the postoperative curative effect but also improve the immune suppression induced by conventional PN or tumor. Therefore, postoperative patients with gastrointestinal cancer should add omega-3 unsaturated fatty acids in their PN formula. Further high-quality RCTs are needed to verify its efficacy.
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Consumption of red and processed meat and breast cancer incidence: A systematic review and meta-analysis of prospective studies.
Farvid, MS, Stern, MC, Norat, T, Sasazuki, S, Vineis, P, Weijenberg, MP, Wolk, A, Wu, K, Stewart, BW, Cho, E
International journal of cancer. 2018;143(11):2787-2799
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Red meat and processed meat are hypothesised to be a dietary risk factor for several types of cancer. The aim of this meta-analysis was to summarise the current evidence regarding the association between red meat and processed meat consumption with breast cancer incidence. According to the existing literature, there is evidence that higher consumption of processed meat, but not red meat, is associated with higher risk of breast cancer. Based on these results, the authors conclude further research is required to better understand the effects of dietary risk factors in various molecular subtypes of breast cancer.
Abstract
Prior studies on red and processed meat consumption with breast cancer risk have generated inconsistent results. We performed a systematic review and meta-analysis of prospective studies to summarize the evidence regarding the relation of red meat and processed meat consumption with breast cancer incidence. We searched in MEDLINE and EMBASE databases through January 2018 for prospective studies that reported the association between red meat and processed meat consumption with incident breast cancer. The multivariable-adjusted relative risk (RR) was combined comparing the highest with the lowest category of red meat (unprocessed) and processed meat consumption using a random-effect meta-analysis. We identified 13 cohort, 3 nested case-control and two clinical trial studies. Comparing the highest to the lowest category, red meat (unprocessed) consumption was associated with a 6% higher breast cancer risk (pooled RR,1.06; 95% confidence intervals (95%CI):0.99-1.14; I2 = 56.3%), and processed meat consumption was associated with a 9% higher breast cancer risk (pooled RR, 1.09; 95%CI, 1.03-1.16; I2 = 44.4%). In addition, we identified two nested case-control studies evaluating the association between red meat and breast cancer stratified by N-acetyltransferase 2 acetylator genotype. We did not observe any association among those with either fast (per 25 g/day pooled odds ratio (OR), 1.18; 95%CI, 0.93-1.50) or slow N-acetyltransferase 2 acetylators (per 25 g/day pooled OR, 0.99; 95%CI, 0.91-1.08). In the prospective observational studies, high processed meat consumption was associated with increased breast cancer risk.
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Probiotics for prevention of radiation-induced diarrhea: A meta-analysis of randomized controlled trials.
Liu, MM, Li, ST, Shu, Y, Zhan, HQ
PloS one. 2017;12(6):e0178870
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Acute radiation-induced diarrhoea is a potentially fatal side effect of radiotherapy for abdominal or pelvic cancers. The mechanisms are not yet known, but effects of the radiation on the microbiota may be a factor and probiotic treatment may therefore be beneficial. The authors of this meta-analysis looked at randomised controlled trials of probiotics in the prevention of radiation-induced diarrhoea with probiotics (there were not enough trials to evaluate probiotics for the treatment of radiation-induced diarrhoea). Only six studies qualified for inclusion into this meta-analysis, with a total of 917 patients (490 receiving probiotics, 427 controls). Compared with placebo, patients receiving probiotics had a significantly lower risk of developing diarrhoea, but there was no significant reduction in anti-diarrhoea medication use or Bristol scale stool form. Most studies did not report adverse events from probiotic treatment. The meta-analysis was limited by several factors: variety of bacterial strains, dosages and timings used, differences in cancer treatment (dose of radiotherapy, radiotherapy alone or with chemotherapy), variability of patient populations and diseases, and diagnostic criteria for diarrhoea.
Abstract
BACKGROUND Radiotherapy is commonly used for abdominal or pelvic cancer, and patients receiving radiotherapy have a high risk developing to an acute radiation-induced diarrhea. Several previous studies have discussed the effect of probiotics on prevention of radiation-induced diarrhea, but the results are still inconsistent. OBJECTIVE We performed a meta-analysis of randomized controlled trials (RCTs) to evaluate the efficacy of probiotic supplementation for prevention the radiation-induced diarrhea. METHODS Relevant RCTs studies assessing the effect of probiotic supplementation on clinical outcomes compared with placebo were searched in PubMed, EMBASE, and the Cochrane Library databases (up to March 30 2016). Heterogeneity was assessed with I2 and H2, and publication bias was evaluated using sensitive analysis. RESULTS Six trials, a total of 917 participants (490 participants received prophylactic probiotics and 427 participants received placebo), were included in this meta-analysis. Compared with placebo, probiotics were associated with a lower incidence of radiation-induced diarrhea (RR: 0.55; 95% CI: 0.34-0.88; P = 0.01; I2: 87%; 95% CI: 75%-94%; H2: 2.8; 95% CI: 2.0-4.0). However, there is no significant difference in the anti-diarrheal medication use (RR: 0.68; 95% CI: 0.40-1.14; P = 0.14) or bristol scale on stool form (RR: 0.64; 95% CI: 0.35-1.17; P = 0.14). CONCLUSION Probiotics may be beneficial to prevent radiation-induced diarrhea in patients who suffered from abdominal or pelvic cancers during radiotherapy period.
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Lycopene and Risk of Prostate Cancer: A Systematic Review and Meta-Analysis.
Chen, P, Zhang, W, Wang, X, Zhao, K, Negi, DS, Zhuo, L, Qi, M, Wang, X, Zhang, X
Medicine. 2015;94(33):e1260
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Lycopene is an antioxidant agent derived from tomatoes, with possible anti-cancer properties including inhibiting growth factors, promoting cell apoptosis, and preventing carcinogenesis. This 2014 meta-analysis reviewed 26 studies and a total of 17,517 prostate patients to see if dose-dependent lycopene supplementation reduced the incidence of prostate cancer compared to 563,299 controls. Prostate cancer (PCa) is the second most common cancer, and a cause of mortality in men. General lycopene intake, via supplementation, showed a slight trend in reducing risk factors for prostate cancer but it was only significant when data from one study was removed to improve the data quality. However, dose-dependent analysis showed that each 5 mg/day increase in lycopene decreased the risk ratio. A higher lycopene consumption of 9 to 21 mg/d was inversely associated with a reduced risk of PCa. High circulating plasma levels of lycopene between 2.17 and 85mg/dL was linearly inversed with PCa risk. Interestingly sub-group analysis of important confounders such as age, family history, energy intake, BMI did not differ considerably between studies. The data was collected from food questionnaires so there may be slight limitations of reporting between the various studies. The study concludes that lycopene may reduce the risk of prostate cancer, but more studies are required to understand the mechanism.
Abstract
Prostate cancer (PCa) is a common illness for aging males. Lycopene has been identified as an antioxidant agent with potential anticancer properties. Studies investigating the relation between lycopene and PCa risk have produced inconsistent results. This study aims to determine dietary lycopene consumption/circulating concentration and any potential dose-response associations with the risk of PCa. Eligible studies published in English up to April 10, 2014, were searched and identified from Pubmed, Sciencedirect Online, Wiley online library databases and hand searching. The STATA (version 12.0) was applied to process the dose-response meta-analysis. Random effects models were used to calculate pooled relative risks (RRs) and 95% confidence intervals (CIs) and to incorporate variation between studies. The linear and nonlinear dose-response relations were evaluated with data from categories of lycopene consumption/circulating concentrations. Twenty-six studies were included with 17,517 cases of PCa reported from 563,299 participants. Although inverse association between lycopene consumption and PCa risk was not found in all studies, there was a trend that with higher lycopene intake, there was reduced incidence of PCa (P = 0.078). Removal of one Chinese study in sensitivity analysis, or recalculation using data from only high-quality studies for subgroup analysis, indicated that higher lycopene consumption significantly lowered PCa risk. Furthermore, our dose-response meta-analysis demonstrated that higher lycopene consumption was linearly associated with a reduced risk of PCa with a threshold between 9 and 21 mg/day. Consistently, higher circulating lycopene levels significantly reduced the risk of PCa. Interestingly, the concentration of circulating lycopene between 2.17 and 85 μg/dL was linearly inversed with PCa risk whereas there was no linear association >85 μg/dL. In addition, greater efficacy for the circulating lycopene concentration on preventing PCa was found for studies with high quality, follow-up >10 years and where results were adjusted by the age or the body mass index. In conclusion, our novel data demonstrates that higher lycopene consumption/circulating concentration is associated with a lower risk of PCa. However, further studies are required to determine the mechanism by which lycopene reduces the risk of PCa and if there are other factors in tomato products that might potentially decrease PCa risk and progression.