Calcium intake and colorectal cancer risk: Results from the nurses' health study and health professionals follow‐up study

The relationship between calcium intake and colorectal cancer (CRC) risk remains inconclusive. We conducted this study to evaluate whether the association between calcium intake and CRC risk differs by anatomic subsite and determine the dose–response relationship for this association, as well as assess when in carcinogenesis calcium may play a role. We assessed calcium intake every 4 years and followed 88,509 women (1980–2012) in the Nurses' Health Study and 47,740 men (1986–2012) in the Health Professionals Follow‐Up Study. We documented 3,078 incident CRC cases. Total calcium intake (≥1,400 vs. <600 mg/d) was associated with a statistically significant lower risk of colon cancer (multivariable relative risk: 0.78, 95%CI: 0.65–0.95). Similar results were observed by different sources of calcium (from all foods or dairy products only). The inverse association was linear and suggestively stronger for distal colon cancer (0.65, 0.43–0.99) than for proximal colon cancer (0.94, 0.72–1.22, p‐_{common effects} = 0.14). Additionally, when comparing different latencies, the overall pattern suggested that the inverse association appeared to be stronger with increasing latency and was strongest for intakes 12–16 years before diagnosis. Comparing total calcium intakes of ≥1,400 vs. <600 mg/d for intake 12–16 y before diagnosis, the pooled RR (95% CIs) of CRC was 0.76 (0.64–0.91). Higher calcium intake was associated with a lower risk of developing colon cancer, especially for distal colon cancer. Overall inverse association was linear and did not differ by intake source. Additionally, calcium intake approximately 10 years before diagnosis appeared to be associated with a lower risk of CRC.     

Cruciferous vegetable consumption and gastric cancer risk: A meta‐analysis of epidemiological studies

The relationship between consumption of cruciferous vegetables (CV) and risk of gastric cancer has been investigated by many studies, but remains controversial. We carried out a meta‐analysis to summarize available evidence from epidemiological studies on this point. Relevant published reports of CV intake and gastric cancer were identified using MEDLINE (PubMed), EMBASE, and Web of Science databases through to the end of September 2012. We pooled the relative risk from individual studies using a fixed‐ or random‐effects model and carried out heterogeneity and publication bias analyses. Sixteen case–control and six prospective studies were included in our analysis. When all studies were pooled, we yielded a significantly inverse association between CV (relative risk = 0.81; 95% confidence interval, 0.75–0.88) intake and gastric cancer risk, with little heterogeneity (Q = 27.27, P = 0.292, I² = 12.0%). Specific analysis for cabbage intake yielded similar result. When separately analyzed, case–control studies of CV intake yielded significant results and the results of prospective studies showed borderline statistical significance. Moreover, significant results were consistent for high‐quality studies, for North American, European, and Asian studies, for studies on males, and for studies on non‐cardia gastric cancer. Findings from this meta‐analysis provide evidence that high intake of CV was inversely associated with the risk of gastric cancer and non‐cardia gastric cancer in humans. Further studies on other specific CV, food preparation methods, and stratified results by anatomic cancer site and histological type should be extended in the future.     

Meat subtypes and their association with colorectal cancer: Systematic review and meta‐analysis

Associations between specific red meat subtypes and risk of colorectal cancer (CRC) have been investigated in a number of epidemiological studies. However, no publication to date has summarised the overall epidemiological evidence. We conducted a systematic review and meta‐analysis of prospective studies (cohort, nested case‐control or case‐cohort studies), which reported relative risk (RR) estimates and 95% confidence intervals (CI) for the association between intake of meat subtypes with colorectal, colon or rectal cancer or colorectal adenoma risk. PubMed and ISI Web of Science were searched up until August 1, 2014. Nineteen studies examined meat subtypes (5 beef, 5 pork, 2 lamb, 1 veal and 19 poultry) and associations with colorectal, colon or rectal cancer risk and 4 studies examined associations with adenoma risk (1 beef and 4 poultry). Comparing highest versus lowest intake, beef consumption was associated with an increased risk of CRC (RR = 1.11, 95% CI = 1.01 to 1.22) and colon cancer (RR = 1.24, 95% CI = 1.07 to 1.44), but no association was found with rectal cancer (RR = 0.95, 95% CI = 0.78 to 1.16). Higher consumption of lamb was also associated with increased risk of CRC (RR = 1.24, 95% CI = 1.08 to 1.44). No association was observed for pork (RR = 1.07, 95% CI = 0.90 to 1.27), but some between study heterogeneity was observed. No association was observed for poultry consumption and risk of colorectal adenomas or cancer. This meta‐analysis suggests that red meat subtypes differ in their association with CRC and its sub sites. Further analysis of data from prospective cohort studies is warranted, especially regarding the role of pork.     

Intakes of vitamins A, C, and E and use of multiple vitamin supplements and risk of colon cancer: a pooled analysis of prospective cohort studies

Objective

To evaluate the associations between intakes of vitamins A, C, and E and risk of colon cancer.

Methods

Using the primary data from 13 cohort studies, we estimated study- and sex-specific relative risks (RR) with Cox proportional hazards models and subsequently pooled RRs using a random effects model.

Results

Among 676,141 men and women, 5,454 colon cancer cases were identified (7–20 years of follow-up across studies). Vitamin A, C, and E intakes from food only were not associated with colon cancer risk. For intakes from food and supplements (total), the pooled multivariate RRs (95% CI) were 0.88 (0.76–1.02, >4,000 vs. ≤1,000 μg/day) for vitamin A, 0.81 (0.71–0.92, >600 vs. ≤100 mg/day) for vitamin C, and 0.78 (0.66–0.92, >200 vs. ≤6 mg/day) for vitamin E. Adjustment for total folate intake attenuated these associations, but the inverse associations with vitamins C and E remained significant. Multivitamin use was significantly inversely associated with colon cancer risk (RR = 0.88, 95% CI: 0.81–0.96).

Conclusions

Modest inverse associations with vitamin C and E intakes may be due to high correlations with folate intake, which had a similar inverse association with colon cancer. An inverse association with multivitamin use, a major source of folate and other vitamins, deserves further study.     

Coffee consumption and the risk of colorectal cancer by anatomical subsite in Japan: Results from the HERPACC studies

Consumption of coffee, a popular beverage worldwide, has been associated with lower colorectal cancer (CRC) risk. Although CRC exhibits different biological characteristics by anatomical subsite, the possibly heterogeneous impact of coffee on CRC by anatomical subsite has remained unclear. Here, we conducted two case‐control studies to examine the association between coffee consumption and CRC risk as well as risk by anatomic subsite among Japanese using data from the Hospital‐based Epidemiological Research Program at Aichi Cancer Center I and II (HERPACC‐I and II). Subjects were enrolled in HERPACC‐I between 1988 and 2000 and in HERPACC‐II between 2001 and 2005. Coffee consumption was measured with a self‐administered questionnaire. A conditional logistic regression model was used to calculate odds ratios (ORs) of CRC with coffee consumption, adjusted for potential confounders of age, smoking, alcohol drinking, red meat intake, BMI, exercise, family history of CRC, and diabetes mellitus history. We estimated summary ORs by pooling study‐specific ORs with a fixed effects model. In total, 2,696 CRC cases and 13,480 non‐cancer outpatients as controls were included. Overall, compared to non‐drinkers, ORs of less than 1 cup/day, 1–2 cups/day and 3 or more cups/day for CRC were 0.88 (95% CI: 0.77–1.00), 0.90 (95% CI: 0.80–1.01) and 0.78 (95% CI: 0.65–0.92), respectively (trend‐p = 0.009). Subsite‐specific analysis revealed a significant inverse linear trend between coffee consumption and distal colon cancer (p‐trend = 0.048), and a tendency toward a lower risk of rectal cancer (p‐trend = 0.068). These findings suggest that coffee consumption might impact the prevention of CRC, especially distal colon cancer.     

Dairy products and colorectal cancer risk: a systematic review and meta-analysis of cohort studies

BackgroundPrevious studies of the association between intake of dairy products and colorectal cancer risk have indicated an inverse association with milk, however, the evidence for cheese or other dairy products is inconsistent.MethodsWe conducted a systematic review and meta-analysis to clarify the shape of the dose–response relationship between dairy products and colorectal cancer risk. We searched the PubMed database for prospective studies published up to May 2010. Summary relative risks (RRs) were estimated using a random effects model.ResultsNineteen cohort studies were included. The summary RR was 0.83 (95% CI [confidence interval]: 0.78–0.88, I² = 25%) per 400 g/day of total dairy products, 0.91 (95% CI: 0.85–0.94, I² = 0%) per 200 g/day of milk intake and 0.96 (95% CI: 0.83–1.12, I² = 28%) per 50 g/day of cheese. Inverse associations were observed in both men and women but were restricted to colon cancer. There was evidence of a nonlinear association between milk and total dairy products and colorectal cancer risk, P < 0.001, and the inverse associations appeared to be the strongest at the higher range of intake.ConclusionsThis meta-analysis shows that milk and total dairy products, but not cheese or other dairy products, are associated with a reduction in colorectal cancer risk.     

Consumption of meat,traditional and modern processed meat and colorectal cancer risk among the Moroccan population: A large-scale case–control study

The current study aimed to investigate the relationship between red and white meat subtypes, processed meat (divided into traditional “Khlii, Kaddid” and industrially processed meat) and colorectal cancer (CRC) risk, considering CRC subsites, in Moroccan adults. A case–control study was conducted including 2,906 matched case–control pairs recruited from the five largest university hospitals in Morocco. Dietary data were collected through a validated Food Frequency Questionnaire (FFQ). Multivariable odds ratios (OR) and 95% confidence intervals (CI), for the association of CRC risk with meat consumption (high vs. low intake), were estimated using conditional logistic regression models, adjusted for relevant confounding variables. Overall, consumption of red meat was positively associated with colon cancer and CRC risk (OR = 1.23, 95% CI = 1.05–1.44; OR = 1.14, 95% CI = 1.02–1.27), respectively. In contrast, no significant association was observed between the consumption of red meat and rectal cancer risk (OR = 1.05, 95% = 0.90–1.23). Interestingly, while processed meat from industrial processes was positively associated with colon cancer, rectal cancer and CRC (OR = 1.61, 95% CI = 1.27–2.04; OR = 1.73, 95% CI = 1.34–2.23; OR = 1.67, 95% CI = 1.41–1.98), processed meat prepared using traditional methods was inversely associated with colon cancer and CRC risk (OR = 0.74, 95% CI = 0.57–0.98; OR = 0.77, 95% CI = 0.64–0.93), respectively. Furthermore, positive associations were observed between poultry intake and colon cancer risk among men (OR = 1.27, 95% CI = 1.01–1.59). Our study showed similar associations between the consumption of red meat and CRC risk in Morocco as in developed countries, while inverse associations were found for traditionally processed meat products. This is the first study to investigate the differential effects of traditional vs. westernized processed meat products in a developing country. Other studies are needed to confirm these findings and to understand the physiological pathways underlying these associations.     

Intakes of heme iron and zinc and colorectal cancer incidence: a meta-analysis of prospective studies

Background

Epidemiologic findings concerning the associations between intakes of heme iron and zinc and colorectal cancer (CRC) incidence yielded conflicting results. We aimed to investigate the associations by performing a meta-analysis of prospective studies.

Methods

We conducted a literature search on PubMed and EMBASE databases up to December 2012 to identify the prospective studies that investigated the relationships between heme iron or zinc intake and risk of CRC. We also reviewed the bibliographies of the retrieved articles to identify additional studies. We used a random-effects model to calculate the summary relative risks (RRs) with 95 % confidence intervals (CIs).

Results

Eight studies on heme iron intake and six studies on zinc intake met the inclusion criteria. The summary RR of CRC for the highest versus the lowest intake was 1.14 (95 % CI = 1.04–1.24) for heme iron and 0.83 (95 % CI = 0.72–0.94) for zinc, respectively. The observed associations were not significantly modified by subsites within the colorectum, sex, geographic area, study duration, the number of cases, or the range of intakes. In the dose–response analyses, the summary RR of CRC was 1.11 (95 % CI = 1.03–1.18) for heme iron intake of 1 mg/day, and 0.86 (95 % CI = 0.78–0.96) for zinc intake of 5 mg/day, respectively. There was little evidence of publication bias.

Conclusion

This meta-analysis suggests a significant positive dose–response association of heme iron intake and a significant inverse dose–response association of zinc intake with risk of CRC.     

Age at menarche and risk of ovarian cancer: A meta‐analysis of epidemiological studies

Epidemiological studies have reported inconsistent associations between menarcheal age and ovarian cancer risk. To our knowledge, a meta‐analysis for the association between menarcheal age and ovarian cancer has not been reported. Relevant published studies of menarcheal age and ovarian cancer were identified using MEDLINE, EMBASE and Web of Science through the end of April 2012. Two authors (T‐T.G. and Q‐J.W.) independently assessed eligibility and extracted data. We pooled the relative risks (RRs) from individual studies using a random‐effects model and performed heterogeneity and publication bias analyses. A total of 27 observational studies consisting of 22 case–control and five cohort studies were included in our analysis. In a pooled analysis of all studies, a statistically significant inverse association was observed between menarcheal age (for the oldest compared to the youngest category) and ovarian cancer risk (RR = 0.85; 95% confidence interval [CI] = 0.75–0.97). The pooled RRs of ovarian cancer for the oldest versus the youngest categories of menarcheal age in prospective and case–control studies were 0.89 (95% CI = 0.76–1.03) and 0.84 (95% CI = 0.70–0.99), respectively. Inverse associations between menarcheal age and ovarian cancer risk were observed in most subgroups; however, the significant association was restricted to invasive and borderline serous ovarian cancer. In conclusion, findings from this meta‐analysis support that menarcheal age was inversely associated with the risk of ovarian cancer. More large studies are warranted to stratify these results by different cancer grading and histotype of ovarian cancer.     

Coffee consumption and risk of colorectal cancer: A systematic review and meta‐analysis of prospective cohort studies

An inverse association between coffee consumption and the risk of colorectal cancer has been found in several case‐control studies, but such an association was not consistent in prospective cohort studies. We conducted a systematic meta‐analysis of prospective cohort studies on coffee consumption and colorectal cancer published up to June 2008. We combined relative risks (RR) for colorectal cancer comparing high vs. low categories of coffee consumption using random‐effects models. We identified 12 eligible cohort studies, which included 646,848 participants and 5,403 cases for colorectal cancer. The summarized result of the meta‐analysis comparing high‐ vs. low‐consumption categories showed no significant effect of coffee consumption on colorectal cancer risk (RR = 0.91; 95% confidence intervals [CI]: 0.81–1.02). The RR was 0.93 (95% CI: 0.71–1.22) when considering 4 studies conducted in the United States of America, 0.91 (95% CI: 0.76–1.10) for 5 studies from Europe, and 0.83 (95% CI: 0.62–1.10) for 3 Japanese studies. No significant differences by sex and cancer‐site were found, but there was a slight suggestion of an inverse association between coffee consumption and colon cancer in women (RR = 0.79; 95% CI: 0.60–1.04), especially Japanese women (RR = 0.62; 95% CI: 0.37–1.05). The suggestive inverse associations were slightly stronger in studies that controlled for smoking and alcohol, and in studies with shorter follow‐up times. Information on coffee type, its serving size, or brewing method may provide a better understanding of this reassuring result and the real role of coffee on colorectal cancer risk. © 2008 Wiley‐Liss, Inc.     

Exposure to acrylamide and human cancer—a review and meta-analysis of epidemiologic studies

BackgroundAcrylamide has been associated to cancer risk in rodents, but data on humans are inconclusive. We thus carried out a critical review and meta-analysis of studies of exposure to acrylamide and cancer.MethodsWe identified 586 publications, 25 presented relevant results. We conducted meta-analyses of studies of dietary intake based on random-effects models by calculating pooled relative risks (RR) and the corresponding 95% confidence intervals (CI). We combined results of occupational studies according to a fixed-effect model.ResultsThe summary RRs for an increase of 10 μg/day of acrylamide intake were close to unity for all the cancers considered, ranging from 0.98 for esophageal cancer to 1.01 for colon, endometrial, ovarian and kidney cancer. None of the estimates was significant. Exclusion of one case–control study from Sweden resulted in a summary RR of kidney cancer of 1.04 (95% CI 1.00–1.08). The combined standardized mortality ratios for high occupational exposure were 1.67 (95% CI 0.83–2.99) for pancreatic cancer and 2.22 (95% CI 0.81–4.84) for kidney cancer.ConclusionsAvailable studies consistently suggest a lack of an increased risk of most types of cancer from exposure to acrylamide. The main association that requires further monitoring involves kidney cancer.     

Diabetes mellitus and subsite-specific colorectal cancer risks in the Iowa Women's Health Study.

OBJECTIVE: Controversy remains regarding the association between type 2 diabetes mellitus (DM) and colorectal cancer (CRC) risk. To clarify and extend the existing data, we prospectively evaluated the association between self-reported type 2 DM (onset at >30 years of age) and incident CRC, overall and by anatomic subsite, among postmenopausal women in the Iowa Women's Health Study (n = 35,230).METHODS: After 14 years of follow-up, a total of 870 incident CRC cases were identified through annual linkage to the Iowa Cancer Registry. DM was analyzed as reported at baseline and as a time-dependent variable using information obtained during follow-up. CRC risks were estimated using Cox proportional hazards regression models.RESULTS: After adjusting for age, body mass index and other potential confounding variables, the relative risk (RR) for women with DM versus women without DM was modestly increased at 1.4 [95% confidence interval (95% CI), 1.1-1.8]. By anatomic subsite, the RR for proximal colon cancer was statistically significantly increased (RR, 1.9; 95% CI, 1.3-2.6), whereas the RRs for distal colon (RR, 1.1; 95% CI, 0.6-1.8) and rectal cancer (RR, 0.8; 95% CI, 0.4-1.6) were not statistically different from unity. Analyses that included DM ascertained at baseline and follow-up yielded similar results.CONCLUSION: In this large, prospective study of postmenopausal women, the association between DM and incident CRC was found to be subsite specific. If confirmed by others, this finding implies that CRC prevention strategies among type 2 DM patients should include examination of the proximal colon.     

Dietary fiber and breast cancer risk: a systematic review and meta-analysis of prospective studies

BackgroundEvidence from case–control studies suggest that dietary fiber may be inversely related to breast cancer risk, but it is unclear if this is supported by prospective data. We conducted a systematic review and meta-analysis of the evidence from prospective studies.MethodsPubMed was searched for prospective studies of fiber intake and breast cancer risk until 31st August 2011. Random effects models were used to estimate summary relative risks (RRs).ResultsSixteen prospective studies were included. The summary RR for the highest versus the lowest intake was 0.93 [95% confidence interval (CI) 0.89–0.98, I² = 0%] for dietary fiber, 0.95 (95% CI 0.86–1.06, I² = 4%) for fruit fiber, 0.99 (95% CI 0.92–1.07, I² = 1%) for vegetable fiber, 0.96 (95% CI 0.90–1.02, I² = 5%) for cereal fiber, 0.91 (95% CI 0.84–0.99, I² = 7%) for soluble fiber and 0.95 (95% CI 0.89–1.02, I² = 0%) for insoluble fiber. The summary RR per 10 g/day of dietary fiber was 0.95 (95% CI 0.91–0.98, I² = 0%, P_{heterogeneity} = 0.82). In stratified analyses, the inverse association was only observed among studies with a large range (≥13 g/day) or high level of intake (≥25 g/day).ConclusionIn this meta-analysis of prospective studies, there was an inverse association between dietary fiber intake and breast cancer risk.     

Aspirin and cancer risk: a quantitative review to 2011

BackgroundAspirin has been associated to a reduced risk of colorectal and possibly of a few other common cancers.MethodsTo provide an up-to-date quantification of this association, we conducted a meta-analysis of all observational studies on aspirin and 12 selected cancer sites published up to September 2011.ResultsRegular aspirin is associated with a statistically significant reduced risk of colorectal cancer [summary relative risk (RR) from random effects models = 0.73, 95% confidence interval (CI) 0.67–0.79], and of other digestive tract cancers (RR = 0.61, 95% CI = 0.50–0.76, for squamous cell esophageal cancer; RR = 0.64, 95% CI = 0.52–0.78, for esophageal and gastric cardia adenocarcinoma; and RR = 0.67, 95% CI = 0.54–0.83, for gastric cancer), with somewhat stronger reductions in risk in case–control than in cohort studies. Modest inverse associations were also observed for breast (RR = 0.90, 95% CI = 0.85–0.95) and prostate cancer (RR = 0.90, 95% CI = 0.85–0.96), while lung cancer was significantly reduced in case–control studies (0.73, 95% CI = 0.55–0.98) but not in cohort ones (RR = 0.98, 95% CI = 0.92–1.05). No meaningful overall associations were observed for cancers of the pancreas, endometrium, ovary, bladder, and kidney.ConclusionsObservational studies indicate a beneficial role of aspirin on colorectal and other digestive tract cancers; modest risk reductions were also observed for breast and prostate cancer. Results are, however, heterogeneous across studies and dose–risk and duration–risk relationships are still unclear.     

Meat subtypes and colorectal cancer risk: A pooled analysis of 6 cohort studies in Japan

Red meat and processed meat have been suggested to increase risk of colorectal cancer (CRC), especially colon cancer. However, it remains unclear whether these associations differ according to meat subtypes or colon subsites. The present study addressed this issue by undertaking a pooled analysis of large population‐based cohort studies in Japan: 5 studies comprising 232 403 participants (5694 CRC cases) for analysis based on frequency of meat intake, and 2 studies comprising 123 635 participants (3550 CRC cases) for analysis based on intake quantity. Study‐specific hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using the Cox proportional hazards model and then pooled using the random effect model. Comparing the highest vs lowest quartile, beef intake was associated with an increased risk of colon cancer in women (pooled HR 1.20; 95% CI, 1.01‐1.44) and distal colon cancer (DCC) risk in men (pooled HR 1.30; 95% CI, 1.05‐1.61). Frequent intake of pork was associated with an increased risk of distal colon cancer in women (pooled HR 1.44; 95% CI, 1.10‐1.87) for “3 times/wk or more” vs “less than 1 time/wk”. Frequent intake of processed red meat was associated with an increased risk of colon cancer in women (pooled HR 1.39; 95% CI, 0.97‐2.00; P trend = .04) for “almost every day” vs “less than 1 time/wk”. No association was observed for chicken consumption. The present findings support that intake of beef, pork (women only), and processed red meat (women only) might be associated with a higher risk of colon (distal colon) cancer in Japanese.     

Cigarette smoking and colorectal cancer incidence and mortality: Systematic review and meta‐analysis

The association between cigarette smoking and colorectal cancer (CRC) has been controversial. To synthesize the available data, we conducted a comprehensive meta‐analysis of all prospective studies. A total of 36 studies were included in our meta‐analysis. We examined the association between smoking and CRC, colon cancer and rectal cancer in terms of incidence and mortality. Separate analyses were conducted for smoking status, daily cigarette consumption, duration, pack‐years and age of initiation. Relative to nonsmokers, current and former smokers had a significantly increased risk of CRC incidence and mortality, respectively. When CRC data were combined with colon/rectal cancer data, current smokers had a significantly increased risk of CRC incidence. All 4 dose–response variables examined—daily cigarette consumption (RR = 1.38 for an increase of 40 cigarettes/day), duration (RR = 1.20 for an increase of 40 years of duration), pack‐years (RR = 1.51 for an increase of 60 pack‐years) and age of initiation (RR = 0.96 for a delay of 10 years in smoking initiation)—were significantly associated with CRC incidence (all p‐values < 0.0001). The relationship between duration of smoking and rectal cancer incidence was also significant. Among the subset of studies that distinguished cancer by site, a higher risk was seen for rectal cancer than for colon cancer for all analyses. Among prospective studies, a consistent association exists between smoking and CRC. The association is stronger for rectal cancer than for colon cancer in the subset of studies that differentiated cancer by site. © 2008 Wiley‐Liss, Inc.     

An update of the WCRF/AICR systematic literature review on esophageal and gastric cancers and citrus fruits intake

Purpose

The 2007 World Cancer Research Fund/American Institute for Cancer Research expert report concluded that foods containing vitamin C probably protect against esophageal cancer and fruits probably protect against gastric cancer. Most of the previous evidence was from case–control studies, which may be affected by recall and selection biases. More recently, several cohort studies have examined these associations. We conducted a systematic literature review of prospective studies on citrus fruits intake and risk of esophageal and gastric cancers.

Methods

PubMed was searched for studies published until 1 March 2016. We calculated summary relative risks and 95 % confidence intervals (95 % CI) using random-effects models.

Results

With each 100 g/day increase of citrus fruits intake, a marginally significant decreased risk of esophageal cancer was observed (summary RR 0.86, 95 % CI 0.74–1.00, 1,057 cases, six studies). The associations were similar for squamous cell carcinoma (RR 0.87, 95 % CI 0.69–1.08, three studies) and esophageal adenocarcinoma (RR 0.93, 95 % CI 0.78–1.11, three studies). For gastric cancer, the nonsignificant inverse association was observed for gastric cardia cancer (RR 0.75, 95 % CI 0.55–1.01, three studies), but not for gastric non-cardia cancer (RR 1.02, 95 % CI 0.90–1.16, four studies). Consistent summary inverse associations were observed when comparing the highest with lowest intake, with statistically significant associations for esophageal (RR 0.77, 95 % CI 0.64–0.91, seven studies) and gastric cardia cancers (RR 0.62, 95 % CI 0.39–0.99, three studies).

Conclusions

Citrus fruits may decrease the risk of esophageal and gastric cardia cancers, but further studies are needed.

     

Circulating leptin levels and risk of colorectal cancer and adenoma: a case–control study and meta-analysis

Purpose

Equivocal results regarding the role of leptin in colorectal cancer (CRC) and adenoma (CRA) have been reported. A case–control study investigating the association of leptin with CRC risk and clinicopathological characteristics along with meta-analysis of published data on both CRC and CRA were conducted.

Methods

Pubmed and Embase were searched for the meta-analysis, comprising 28 case–control studies amounting 3,614 CRC and 1,215 CRA cases, along with 5,220 controls. Meticulous contact with the authors of individual studies was undertaken for the provision of additional data. Pooling of standardized mean differences (SMD), relative risks (RR) and 95 % CI (random effects models), subgroup, sensitivity, and meta-regression analyses were conducted.

Results

The meta-analysis suggested positive association of serum leptin with CRA (RR, 95 % CI 1.35, 1.03 to +1.76), but not CRC either at the pooled analysis on SMDs or RRs (SMD, 95 % CI 0.18, ?0.04 to +0.40; RR, 95 % CI 1.04, 0.65 to +1.65). Significant heterogeneity between studies on CRC as well as between studies on CRA providing SMD was noted. Subgroup, meta-regression and sensitivity analyses highlighted potential methodology-, design-, size- and quality-related effect modifiers.

Conclusions

Meta-analysis of current evidence suggests positive association of serum leptin with CRA but not with CRC risk. Given the case–control nature of available studies, the limited number of studies on serum leptin and CRA, and the heterogeneity of CRC studies, carefully designed, prospective studies preferably reporting RRs adjusted for a variety of confounders may be warranted.     

Intake of dietary folate vitamers and risk of colorectal carcinoma: results from The Netherlands Cohort Study

BACKGROUND: Several studies have reported inverse associations between folate intake and colorectal carcinoma risk. Few were prospective studies and none evaluated the association between the intake of individual folate vitamers and colorectal carcinoma risk. METHODS: The aim of the current study was to investigate the relationship between dietary folate intake and the risk of colorectal carcinoma in a large prospective cohort study in The Netherlands comprising 120,852 men and women aged 55-69 years. After 7.3 years of follow-up, 760 colon and 411 rectal carcinoma cases were available for analysis. Data processing and analysis used the case-cohort approach. A new Dutch database was used to estimate intakes of total and individual folate vitamers. RESULTS: Analyses adjusted for age, energy intake, family history of colorectal carcinoma, alcohol, vitamin C, iron, and dietary fiber intake yielded an inverse association between colon carcinoma risk and total dietary folate intake (rate ratio [RR]highest vs. lowest quintile, men: 0.73; 95% confidence interval [CI], 0.46-1.17, P trend = 0.03; women: 0.68; 95% CI, 0.39-1.20, P trend = 0.18). An inverse association between rectal carcinoma and total dietary folate intake was found only among men (RR highest vs. lowest quintile, men: 0.66; 95% CI, 0.35-1.21, P trend = 0.03). Analyses showed no clear difference in colorectal carcinoma risk associated with intake of different folate vitamers. CONCLUSIONS: Dietary folate intake was related inversely to colon and male rectal carcinoma risk.     

Dietary intake of fish, ω‐3 and ω‐6 fatty acids and risk of colorectal cancer: A prospective study in U.S. men and women

The association between fish, ω‐3 and ω‐6 polyunsaturated fatty acid (PUFA) intake and risk of colorectal cancer (CRC) remains inconclusive. Recent prospective studies suggest that the relationship may vary by gender, subsite and duration of follow‐up. We followed 123,529 US adults (76,386 women and 47,143 men) without a history of cancer at baseline for 24 to 26 years. Fish and PUFA intake was assessed at baseline and updated every 4 years by using a validated food‐frequency questionnaire. We found no overall association between fish, ω‐3 and ω‐6 PUFA intake and CRC risk with hazard ratio (HR) of 1.03 [95% confidence interval (CI): 0.89–1.20] comparing marine ω‐3 intake of ≥0.30 g/d versus <0.15 g/d among women and 1.05 (95% CI: 0.85–1.30) comparing intake of ≥0.41 g/d versus <0.16 g/d among men. However, fish and marine ω‐3 PUFA intake appeared to be positively associated with risk of distal colon cancer in both men and women and inversely with risk of rectal cancer in men. In an analysis based on a limited number of cases, marine ω‐3 PUFA intake assessed 12–16 years before diagnosis tended to be inversely associated with CRC risk in men (HR: 0.76; 95% CI: 0.52–1.10). In conclusion, although no overall association between fish, ω‐3 or ω‐6 PUFA intake was observed with CRC risk, marine ω‐3 PUFA may be differentially associated with risk of distal colon and rectal cancers and a long latency may be needed for its protection against CRC in men.