Doris S. M. Chan

Dietary fibre, whole grains, and risk of colorectal cancer: systematic review and dose-response meta-analysis of prospective studies

Objective To investigate the association between intake of dietary fibre and whole grains and risk of colorectal cancer. Design Systematic review and meta-analysis of prospective observational studies. Data sources PubMed and several other databases up to December 2010 and the reference lists of studies included in the analysis as well as those listed in published meta-analyses. Study selection Prospective cohort and nested case-control studies of dietary fibre or whole grain intake and incidence of colorectal cancer. Results 25 prospective studies were included in the analysis. The summary relative risk of developing colorectal cancer for 10 g daily of total dietary fibre (16 studies) was 0.90 (95% confidence interval 0.86 to 0.94, I2=0%), for fruit fibre (n=9) was 0.93 (0.82 to 1.05, I2=23%), for vegetable fibre (n=9) was 0.98 (0.91 to 1.06, I2=0%), for legume fibre (n=4) was 0.62 (0.27 to 1.42, I2=58%), and for cereal fibre (n=8) was 0.90 (0.83 to 0.97, I2=0%). The summary relative risk for an increment of three servings daily of whole grains (n=6) was 0.83 (0.78 to 0.89, I2=18%). Conclusion A high intake of dietary fibre, in particular cereal fibre and whole grains, was associated with a reduced risk of colorectal cancer. Further studies should report more detailed results, including those for subtypes of fibre and be stratified by other risk factors to rule out residual confounding. Further assessment of the impact of measurement errors on the risk estimates is also warranted.

Red and Processed Meat and Colorectal Cancer Incidence: Meta-Analysis of Prospective Studies

Background The evidence that red and processed meat influences colorectal carcinogenesis was judged convincing in the 2007 World Cancer Research Fund/American Institute of Cancer Research report. Since then, ten prospective studies have published new results. Here we update the evidence from prospective studies and explore whether there is a non-linear association of red and processed meats with colorectal cancer risk. Methods and Findings Relevant prospective studies were identified in PubMed until March 2011. For each study, relative risks and 95% confidence intervals (CI) were extracted and pooled with a random-effects model, weighting for the inverse of the variance, in highest versus lowest intake comparison, and dose-response meta-analyses. Red and processed meats intake was associated with increased colorectal cancer risk. The summary relative risk (RR) of colorectal cancer for the highest versus the lowest intake was 1.22 (95% CI  = 1.11−1.34) and the RR for every 100 g/day increase was 1.14 (95% CI  = 1.04−1.24). Non-linear dose-response meta-analyses revealed that colorectal cancer risk increases approximately linearly with increasing intake of red and processed meats up to approximately 140 g/day, where the curve approaches its plateau. The associations were similar for colon and rectal cancer risk. When analyzed separately, colorectal cancer risk was related to intake of fresh red meat (RR for 100 g/day increase  = 1.17, 95% CI  = 1.05−1.31) and processed meat (RR for 50 g/day increase  = 1.18, 95% CI  = 1.10−1.28). Similar results were observed for colon cancer, but for rectal cancer, no significant associations were observed. Conclusions High intake of red and processed meat is associated with significant increased risk of colorectal, colon and rectal cancers. The overall evidence of prospective studies supports limiting red and processed meat consumption as one of the dietary recommendations for the prevention of colorectal cancer.

Is concordance with World Cancer Research Fund/American Institute for Cancer Research guidelines for cancer prevention related to subsequent risk of cancer? Results from the EPIC study

BACKGROUND In 2007 the World Cancer Research Fund (WCRF) and the American Institute of Cancer Research (AICR) issued 8 recommendations (plus 2 special recommendations) on diet, physical activity, and weight management for cancer prevention on the basis of the most comprehensive collection of available evidence. OBJECTIVE We aimed to investigate whether concordance with the WCRF/AICR recommendations was related to cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. DESIGN The present study included 386,355 EPIC participants from 9 European countries. At recruitment, dietary, anthropometric, and lifestyle information was collected. A score was constructed based on the WCRF/AICR recommendations on weight management, physical activity, foods and drinks that promote weight gain, plant foods, animal foods, alcoholic drinks, and breastfeeding for women; the score range was 0-6 for men and 0-7 for women. Higher scores indicated greater concordance with WCRF/AICR recommendations. The association between the score and cancer risk was estimated by using multivariable Cox regression models. RESULTS Concordance with the score was significantly associated with decreased risk of cancer. A 1-point increment in the score was associated with a risk reduction of 5% (95% CI: 3%, 7%) for total cancer, 12% (95% CI: 9%, 16%) for colorectal cancer, and 16% (95% CI: 9%, 22%) for stomach cancer. Significant associations were also observed for cancers of the breast, endometrium, lung, kidney, upper aerodigestive tract, liver, and esophagus but not for prostate, ovarian, pancreatic, and bladder cancers. CONCLUSION Adherence to the WCRF/AICR recommendations for cancer prevention may lower the risk of developing most types of cancer.

Nonlinear Reduction in Risk for Colorectal Cancer by Fruit and Vegetable Intake Based on Meta-analysis of Prospective Studies

BACKGROUND & AIMS The association between fruit and vegetable intake and colorectal cancer risk has been investigated by many studies but is controversial because of inconsistent results and weak observed associations. We summarized the evidence from cohort studies in categorical, linear, and nonlinear, dose-response meta-analyses. METHODS We searched PubMed for studies of fruit and vegetable intake and colorectal cancer risk that were published until the end of May 2010. We included 19 prospective studies that reported relative risk estimates and 95% confidence intervals (CIs) of colorectal cancer-associated with fruit and vegetable intake. Random effects models were used to estimate summary relative risks. RESULTS The summary relative risk for the highest vs the lowest intake was 0.92 (95% CI: 0.86-0.99) for fruit and vegetables combined, 0.90 (95% CI: 0.83-0.98) for fruit, and 0.91 (95% CI: 0.86-0.96) for vegetables (P for heterogeneity=.24, .05, and .54, respectively). The inverse associations appeared to be restricted to colon cancer. In linear dose-response analysis, only intake of vegetables was significantly associated with colorectal cancer risk (summary relative risk=0.98; 95% CI: 0.97-0.99), per 100 g/d. However, significant inverse associations emerged in nonlinear models for fruits (Pnonlinearity<.001) and vegetables (Pnonlinearity=.001). The greatest risk reduction was observed when intake increased from very low levels of intake. There was generally little evidence of heterogeneity in the analyses and there was no evidence of small-study bias. CONCLUSIONS Based on meta-analysis of prospective studies, there is a weak but statistically significant nonlinear inverse association between fruit and vegetable intake and colorectal cancer risk.

Adherence to the World Cancer Research Fund/American Institute for Cancer Research guidelines and risk of death in Europe: results from the European Prospective Investigation into Nutrition and Cancer cohort study

BACKGROUND In 2007, the World Cancer Research Fund (WCRF) and the American Institute for Cancer Research (AICR) issued recommendations on diet, physical activity, and weight management for cancer prevention on the basis of the most comprehensive collection of available evidence. OBJECTIVE We investigated whether concordance with WCRF/AICR recommendations is related to risk of death. DESIGN The current study included 378,864 participants from 9 European countries enrolled in the European Prospective Investigation into Cancer and Nutrition study. At recruitment (1992-1998), dietary, anthropometric, and lifestyle information was collected. A WCRF/AICR score, which incorporated 6 of the WCRF/AICR recommendations for men [regarding body fatness, physical activity, foods and drinks that promote weight gain, plant foods, animal foods, and alcoholic drinks (score range: 0-6)] and 7 WCRF/AICR recommendations for women [plus breastfeeding (score range: 0-7)], was constructed. Higher scores indicated greater concordance with WCRF/AICR recommendations. Associations between the WCRF/AICR score and risks of total and cause-specific death were estimated by using Cox regression analysis. RESULTS After a median follow-up time of 12.8 y, 23,828 deaths were identified. Participants within the highest category of the WCRF/AICR score (5-6 points in men; 6-7 points in women) had a 34% lower hazard of death (95% CI: 0.59, 0.75) compared with participants within the lowest category of the WCRF/AICR score (0-2 points in men; 0-3 points in women). Significant inverse associations were observed in all countries. The WCRF/AICR score was also significantly associated with a lower hazard of dying from cancer, circulatory disease, and respiratory disease. CONCLUSION Results of this study suggest that following WCRF/AICR recommendations could significantly increase longevity.

Maternal Alcohol Consumption during Pregnancy and Risk of Childhood Leukemia: Systematic Review and Meta-analysis

Background: Leukemia is the most frequently occurring cancer in children. Although its etiology is largely unknown, leukemia is believed to result from an interaction between genetic and environmental factors. Among different potential risk factors, the possible role of maternal alcohol consumption during pregnancy has been questioned. Methods: To assess the association between maternal alcohol consumption during pregnancy and childhood leukemia, a systematic review and meta-analysis of published studies was done. Results: Twenty-one case-control studies were included in categorical and dose-response meta-analyses. No cohort study was identified. Analyses were conducted by type of leukemia, childrens age at diagnosis, and type of alcoholic beverage and trimester of pregnancy at alcohol use. Alcohol intake during pregnancy (yes versus no) was statistically significantly associated with childhood acute myeloid leukemia (AML) [odds ratio (OR), 1.56; 95% confidence interval (CI), 1.13-2.15] but not with acute lymphoblastic leukemia (OR, 1.10; 95% CI, 0.93-1.29). Heterogeneity between studies was observed. The OR of AML for an increase of a drink per week was 1.24 (95% CI, 0.94-1.64). The association of alcohol intake during pregnancy with AML was observed for cancers diagnosed at age 0 to 4 years (OR, 2.68; 95% CI, 1.85-3.89) in five studies without heterogeneity (I2 ≤ 0.1%). Conclusions: The results of case-control studies indicate that maternal alcohol consumption during pregnancy is associated with a significantly increased risk of AML in young children. Impact: Avoidance of maternal alcohol drinking during pregnancy might contribute to a decrease in the risk of childhood AML. Cancer Epidemiol Biomarkers Prev; 19(5); 1238–60. ©2010 AACR.

Dietary supplement use and colorectal cancer risk: a systematic review and meta-analyses of prospective cohort studies.

Use of dietary supplements is rising in countries where colorectal cancer is prevalent. We conducted a systematic literature review and meta‐analyses of prospective cohort studies on dietary supplement use and colorectal cancer risk. We identified relevant studies in Medline, Embase and Cochrane up to January 2013. Original and peer‐reviewed papers on dietary supplement use and colorectal cancer, colon cancer, or rectal cancer incidence were included. “Use‐no use”(U‐NU), “highest‐lowest”(H‐L) and “dose‐response”(DR) meta‐analyses were performed. Random‐effects models were used to estimate summary estimates. In total, 24 papers were included in the meta‐analyses. We observed inverse associations for colorectal cancer risk and multivitamin (U‐NU: RR = 0.92; 95% CI: 0.87,0.97) and calcium supplements (U‐NU: RR = 0.86; 95% CI: 0.79,0.95; H‐L: RR = 0.80; 95% CI: 0.70,0.92; DR: for an increase of 100 mg/day, RR = 0.96; 95% CI: 0.94,0.99). Inconsistent associations were found for colon cancer risk and supplemental vitamin A and vitamin C, and for colorectal cancer risk and supplemental vitamin D, vitamin E, garlic and folic acid. Meta‐analyses of observational studies suggest a beneficial role for multivitamins and calcium supplements on colorectal cancer risk, while the association with other supplements and colorectal cancer risk is inconsistent. Residual confounding of lifestyle factors might be present. Before recommendations can be made, an extensive assessment of dietary supplement use and a better understanding of underlying mechanisms is needed.

Foods and beverages and colorectal cancer risk: a systematic review and meta-analysis of cohort studies, an update of the evidence of the WCRF-AICR Continuous Update Project

Objective As part of the World Cancer Research Fund International Continuous Update Project, we updated the systematic review and meta-analysis of prospective studies to quantify the dose-response between foods and beverages intake and colorectal cancer risk. Data sources PubMed and several databases up to 31 May 2015. Study selection Prospective studies reporting adjusted relative risk estimates for the association of specific food groups and beverages and risk of colorectal, colon and rectal cancer. Data synthesis Dose-response meta-analyses using random effect models to estimate summary relative risks (RRs). Results About 400 individual study estimates from 111 unique cohort studies were included. Overall, the risk increase of colorectal cancer is 12% for each 100 g/day increase of red and processed meat intake (95% CI = 4-21%, I2=70%, pheterogeneity (ph)<0.01) and 7% for 10 g/day increase of ethanol intake in alcoholic drinks (95% CI = 5-9%, I2=25%, ph = 0.21). Colorectal cancer risk decrease in 17% for each 90g/day increase of whole grains (95% CI = 11-21%, I2 = 0%, ph = 0.30, 6 studies) and 13% for each 400 g/day increase of dairy products intake (95% CI = 10-17%, I2 = 18%, ph = 0.27, 10 studies). Inverse associations were also observed for vegetables intake (RR per 100 g/day =0.98 (95% CI = 0.96-0.99, I2=0%, ph = 0.48, 11 studies) and for fish intake (RR for 100 g/day = 0.89 (95% CI = 0.80-0.99, I2=0%, ph = 0.52, 11 studies), that were weak for vegetables and driven by one study for fish. Intakes of fruits, coffee, tea, cheese, poultry and legumes were not associated with colorectal cancer risk. Conclusions Our results reinforce the evidence that high intake of red and processed meat and alcohol increase the risk of colorectal cancer. Milk and whole grains may have a protective role against colorectal cancer. The evidence for vegetables and fish was less convincing.

Alcohol Drinking and Second Primary Cancer Risk in Patients with Upper Aerodigestive Tract Cancers: A Systematic Review and Meta-analysis of Observational Studies

Background: We conducted a systematic review and meta-analysis of existing data from observational studies to assess the strength of the association of alcohol drinking with second primary cancer risk in patients with upper aerodigestive tract (UADT; oral cavity, pharynx, larynx, and esophagus) cancer. Methods: PubMed and Embase were searched up to July 2012 and the reference lists of studies included in the analysis were examined. Random-effects models were used to estimate summary relative risks (RR) and 95% confidence interval (CI). Results: Nineteen studies, 8 cohort and 11 case–control studies, were included. In highest versus lowest meta-analyses, alcohol drinking was associated with significantly increased risk of UADT second primary cancers (RR, 2.97; 95% CI, 1.96–4.50). Significantly increased risks were also observed for UADT and lung combined (RR, 1.90; 95% CI, 1.16–3.11) and all sites (RR, 1.60; 95% CI, 1.22–2.10) second primary cancers. For an increase in the alcohol intake of 10 grams per day, dose–response meta-analysis resulted in a significantly increased RR of 1.09 (95% CI, 1.04–1.14) for UADT second primary cancers. Conclusions: Alcohol drinking in patients with UADT cancer is associated with an increased risk of second primary cancers. Studies conducted in alcohol drinking patients with UADT cancer and evaluating the effect of alcohol cessation on second primary cancer and other outcomes are needed. Impact: Our results emphasize the importance of prevention policies aiming to reduce alcohol drinking. Health-care professionals should encourage alcohol drinking patients with UADT cancer to reduce their consumption and reinforce the surveillance of this at-risk subpopulation. Cancer Epidemiol Biomarkers Prev; 23(2); 324–31. ©2013 AACR.

Anthropometric factors and ovarian cancer risk: A systematic review and nonlinear dose-response meta-analysis of prospective studies

In the World Cancer Research Fund/American Institute for Cancer Research report from 2007 the evidence relating body fatness to ovarian cancer risk was considered inconclusive, while the evidence supported a probably causal relationship between adult attained height and increased risk. Several additional cohort studies have since been published, and therefore we conducted an updated meta‐analysis of the evidence as part of the Continuous Update Project. We searched PubMed and several other databases up to 20th of August 2014. Summary relative risks (RRs) were calculated using a random effects model. The summary relative risk for a 5‐U increment in BMI was 1.07 (95% CI: 1.03–1.11, I2 = 54%, n = 28 studies). There was evidence of a nonlinear association, pnonlinearity < 0.0001, with risk increasing significantly from BMI∼28 and above. The summary RR per 5 U increase in BMI in early adulthood was 1.12 (95% CI: 1.05–1.20, I2 = 0%, pheterogeneity= 0.54, n = 6), per 5 kg increase in body weight was 1.03 (95% CI: 1.02–1.05, I2 = 0%, n = 4) and per 10 cm increase in waist circumference was 1.06 (95% CI: 1.00–1.12, I2 = 0%, n = 6). No association was found for weight gain, hip circumference or waist‐to‐hip ratio. The summary RR per 10 cm increase in height was 1.16 (95% CI: 1.11–1.21, I2 = 32%, n = 16). In conclusion, greater body fatness as measured by body mass index and weight are positively associated risk of ovarian cancer, and in addition, greater height is associated with increased risk. Further studies are needed to clarify whether abdominal fatness and weight gain is associated with risk.