Case-control study on colorectal cancer and diet in Marseilles

Dietary risk factors in gastrointestinal cancers: A case-control study in North India

Background

One-third of all cancer deaths are preventable by alterations in diet.

Methods

A case control study was conducted in a Regional Cancer Center in North India to evaluate the relationship of diet with selected gastrointestinal cancers. A total of 171 cases, 151 hospital controls, and 167 healthy controls were interviewed using food frequency questionnaire. Data was analyzed using odds ratio with 95% confidence interval and Chi-square test.

Results

Two to three times increased risk of GI cancers was observed with hot and salted tea. Alcohol [OR 2.30 (1.32-4)] and smoking [OR (2.77 (1.77-4.33)] emerged as risk factors in healthy controls among whom freshly prepared food had significant protective effect [OR 0.57 (0.37-0.88)]. Sweet tea showed protective effect in hospital and healthy controls (OR 0.33 and 0.26, respectively). NSAIDS was associated with significantly higher risk of GI cancers. Consumption of dietary fibers decreased risk, which was significant for wheat and pulses but insignificant for rice. Vegetables and fruits showed significant protective effect ranging from 20 to 80% while intake of non-vegetarian foods showed significantly higher odds among controls (OR 2.37-13.4). Odds of GI cancer cases having consumed chutneys and pickles were significantly higher in comparison to healthy controls while consumption of dairy products showed protection. Low and medium intake of mixed spices inclusive of curcumin showed protection (OR 0.13 and 0.39, respectively) while intake of red chillies was associated with 2-30 times significantly higher odds.

Conclusions

We have been able to generate baseline evidence of association between diet and selected GI cancers to encourage prevention and further research.

Comparison of Fatty Acid Contents and MMP-1 Inhibitory Effects of the Two Antarctic Fish, Notothenia rossii and Champsocephalus gunnari

Total fatty-acid (FA) contents of different organs (stomach, liver, brain, and skin) of two Antarctic fish, marbled rockcod (Notothenia rossii) and mackerel icefish (Champsocephalus gunnari), were examined using gas chromatography–mass spectrometry (GC–MS). N. rossii possessed higher contents of total omega-3, where eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), the most represented omega-3 FAs, were distributed throughout all parts of the fish. The highest level of EPA was observed in the skin and that of DHA was observed in the brain of N. rossii. C. gunnari showed organ peculiarity in that most of the omega-3 FAs were found in stomach and skin. Specifically, the highest levels of EPA and DHA were both observed in the stomach. Although N. rossii and C. gunnari both inhabit the Antarctic Southern Oceans, their characteristics in terms of the composition of fatty acids were shown to vary. The extracts were also evaluated for matrix metalloproteinase-1 (MMP-1)-inhibitory activities in UVB-induced human dermal fibroblasts, where extracts of the skin and liver of N. rossii showed the most significant inhibition upon MMP-1 production. These findings provide experimental evidence that the extracts of the Antarctic fish could be utilized as bioactive nutrients, particularly in the enhancement of skin health.

The role of calcium and vitamin D dietary intake on risk of colorectal cancer: systematic review and meta-analysis of case-control studies

PURPOSE

The aim of this study is to analyze the current evidence about the relationships between calcium/vitamin D and CRC based on case-control studies according to sex, tumor location and continental region to complement the information obtained in meta-analyses of other designs.

METHODS

The articles were located in three databases (PUBMED, EMBASE and SCOPUS), they should be written in English language, with a case and control design and published between 1 January 1970 and 31 October 2019.

RESULTS

There were 37 selected studies, 32 for intake of calcium, that involved 24,353 CRC cases and 30,650 controls, and 23 for that of VIT D, with a total of 19,076 cases and 36.746 controls included. For dietary calcium intake, the overall OR was 0.94 (95% CI 0.92-0.97), suggesting a reducing effect with a 6% decrease in CRC risk for every 300 mg of calcium ingested daily. Regarding vitamin D intake a global OR of 0.96 (95% CI 0.93-0.98) was observed, what means a 4% decrease in the risk of CRC per 100 IU/day of vitamin D.

CONCLUSION

Higher dietary intakes of calcium and vitamin D are associated to a decreased risk of CRC.

Potato Consumption and Risk of Site-Specific Cancers in Adults: A Systematic Review and Dose-Response Meta-Analysis of Observational Studies

The etiology of cancer type may vary significantly due to anatomy, embryology, and physiology of the cancer site. Although the association between potato consumption and colorectal cancer (CRC) was summarized in a 2018 meta-analysis of 5 cohort studies, to the best of our knowledge, no meta-analysis has evaluated potato consumption in relation to multiple cancer sites in adults. Medline/PubMed, ISI Web of Knowledge, Scopus, and the Cochrane Database of Systematic Reviews were searched for relevant publications through August 2020. We selected cohort or case-control studies conducted in adults that reported risk estimates (relative risk [RRs], HRs, and ORs) of potato intake for any cancer type. Random effects meta-analyses compared high and low intake categories. Twenty prospective cohort studies (total n = 785,348) including 19,882 incident cases, and 36 case-control studies (21,822 cases; 66,502 controls) were included. Among cohort studies, we did not find an association between high versus low intake of total potato (white and yellow) consumption and overall cancers: 1.04 (95% CI: 0.96, 1.11; tau2 = 0.005, n = 18). We found no relation between total potato consumption (high compared with low intake) and risk of CRC, pancreatic cancer, colon, gastric, breast, prostate, kidney, lung, or bladder cancer in cohort or case-control studies. We did not find an association between high versus low consumption of potato preparations (boiled/fried/mashed/roasted/baked) and risk of gastrointestinal-, sex-hormone-, or urinary-related cancers in cohort or case-control studies. Certainty of the evidence was low for total cancer, CRC, colon, rectal, renal, pancreatic, breast, prostate, and lung cancer and very low for gastric and bladder cancer. In conclusion, potato intake or potato preparations were not associated with multiple cancer sites when comparing high and low intake categories. This finding was consistent with the findings from the 2018 meta-analysis regarding potato intake and risk of CRC.

A Review of the In Vivo Evidence Investigating the Role of Nitrite Exposure from Processed Meat Consumption in the Development of Colorectal Cancer

The World Cancer Research Fund (WCRF) 2007 stated that the consumption of processed meat is a convincing cause of colorectal cancer (CRC), and therefore, the public should avoid it entirely. Sodium nitrite has emerged as a putative candidate responsible for the CRC-inducing effects of processed meats. Sodium nitrite is purported to prevent the growth of Clostridium botulinum and other food-spoiling bacteria, but recent, contradictory peer-reviewed evidence has emerged, leading to media reports questioning the necessity of nitrite addition. To date, eleven preclinical studies have investigated the effect of consuming nitrite/nitrite-containing meat on the development of CRC, but the results do not provide an overall consensus. A sizable number of human clinical studies have investigated the relationship between processed meat consumption and CRC risk with widely varying results. The unique approach of the present literature review was to include analysis that limited the human studies to those involving only nitrite-containing meat. The majority of these studies reported that nitrite-containing processed meat was associated with increased CRC risk. Nitrite consumption can lead to the formation of N-nitroso compounds (NOC), some of which are carcinogenic. Therefore, this focused perspective based on the current body of evidence links the consumption of meat containing nitrites and CRC risk.

Fecal Fatty Acid Profiling as a Potential New Screening Biomarker in Patients with Colorectal Cancer

BACKGROUND

The fatty acid profile of the fecal metabolome and its association with colorectal cancer (CRC) has not been fully evaluated.

AIMS

We aimed to compare the fecal fatty acid profiles of CRC patients and healthy controls.

METHODS

We enrolled 26 newly diagnosed CRC patients and 28 healthy individuals between July 2014 and August 2014 from our institute. Long- and short-chain fatty acids were extracted from fecal samples and analyzed using gas chromatography-mass spectrometry.

RESULTS

Regarding fecal long-chain fatty acids, the levels of total ω-6 polyunsaturated fatty acids and, particularly, of linoleic acid (C18:2ω-6) were significantly higher in male CRC patients than in healthy men (2.750 ± 2.583 vs. 1.254 ± 0.966 µg/mg feces, P = 0.040; 2.670 ± 2.507 vs. 1.226 ± 0.940 µg/mg feces, P = 0.034, respectively). In addition, the levels of total monounsaturated fatty acid and, particularly, of oleic acid (C18:1ω-9) were significantly higher in male CRC patients than in healthy men (1.802 ± 1.331 vs. 0.977 ± 0.625 µg/mg feces, P = 0.027; 1.749 ± 1.320 vs. 0.932 ± 0.626 µg/mg feces, P = 0.011, respectively). However, those differences were not shown in female gender. The level of fecal short-chain fatty acids was not different between CRC patients and healthy controls.

CONCLUSIONS

There were changes in the profiles of fecal fatty acid metabolomes in CRC patients compared to healthy controls, implying that fecal fatty acids could be used as a novel screening tool for CRC.

Dietary Habits in Spain: An Approximation

The dietary pattern of a population sample of males selected as a control group for a case-control study on bladder cancer carried out in four different regions of Spain is presented. Out of 807 population controls initially selected, 530 were interviewed, 465 males and 65 females. The method of selection of the study subjects and the diet assessment method are described. Our results confirm the Mediterranean pattern of the Spanish diet, with an important consumption of fresh fish, fruits and vegetables, and the use of vegetable oils, specially olive oil, for cooking and seasoning, accompanied with a high polyunsaturated/saturated ratio (0.7). The consumption of butter, cheese and other dairy products, on the other hand, is very low. Estimated total caloric intake is relatively low if compared with international figures, although questionnaire base assessment may seriously underestimate caloric intake, as it is the absolute amount of intake of lipids and carbohydrates. In relative terms, however, lipids provide the highest percentage of calories.

Cigarette smoke extracts induced the colon cancer migration via regulating epithelial mesenchymal transition and metastatic genes in human colon cancer cells

There was considerable evidence that exposure to cigarette smoke is associated with an increased risk for colon cancer. Nevertheless, the mechanism underlying the relationship between cigarette smoking and colon cancer remains unclear. Moreover, there were only a few studies on effects of complexing substance contained in cigarette smoke on colon cancer. Thus, we further investigated whether cigarette smoke extract (CSE) affects the cell cycle, apoptosis and migration of human metastatic colon cancer cells, SW-620. MTT assay revealed that SW-620 cell proliferation was significantly inhibited following treatments with all CSEs, 3R4F, and two-domestic cigarettes, for 9 days in a concentration-dependent manner. Moreover, CSE treatments decreased cyclin D1 and E1, and increased p21 and p27 proteins by Western blot analysis in SW-620 cells. Additionally, the treatment of the cells with CSE contributed to these effects expressing by apoptosis-related proteins. An increased migration or invasion ability of SW-620 cells following CSE treatment was also confirmed by a scratch or fibronectin invasion assay in vitro. In addition, the protein levels of E-cadherin as an epithelial maker were down-regulated, while the mesenchymal markers, N-cadherin, snail, and slug, were up-regulated in a time-dependent manner. A metastatic marker, cathepsin D, was also down-regulated by CSE treatment. Taken together, these results indicate that CSE exposure in colon cancer cells may deregulate the cell growth by altering the expression of cell cycle-related proteins and pro-apoptotic protein, and stimulate cell metastatic ability by altering epithelial-mesenchymal transition (EMT) markers and cathepsin D expression. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 690-704, 2017.

Pharmacological Intervention through Dietary Nutraceuticals in Gastrointestinal Neoplasia

Neoplastic conditions associated with gastrointestinal (GI) tract are common worldwide with colorectal cancer alone accounting for the third leading rate of cancer incidence. Other GI malignancies such as esophageal carcinoma have shown an increasing trend in the last few years. The poor survival statistics of these fatal cancer diseases highlight the need for multiple alternative treatment options along with effective prophylactic strategies. Worldwide geographical variation in cancer incidence indicates a correlation between dietary habits and cancer risk. Epidemiological studies have suggested that populations with high intake of certain dietary agents in their regular meals have lower cancer rates. Thus, an impressive embodiment of evidence supports the concept that dietary factors are key modulators of cancer including those of GI origin. Preclinical studies on animal models of carcinogenesis have reflected the pharmacological significance of certain dietary agents called as nutraceuticals in the chemoprevention of GI neoplasia. These include stilbenes (from red grapes and red wine), isoflavones (from soy), carotenoids (from tomatoes), curcuminoids (from spice turmeric), catechins (from green tea), and various other small plant metabolites (from fruits, vegetables, and cereals). Pleiotropic action mechanisms have been reported for these diet-derived chemopreventive agents to retard, block, or reverse carcinogenesis. This review presents a prophylactic approach to primary prevention of GI cancers by highlighting the translational potential of plant-derived nutraceuticals from epidemiological, laboratory, and clinical studies, for the better management of these cancers through consumption of nutraceutical rich diets and their intervention in cancer therapeutics.

Nonlinear association between magnesium intake and the risk of colorectal cancer

OBJECTIVES

The association between dietary magnesium intake and the risk of colorectal cancer has been examined by many prospective studies, but remains controversial because of inconsistent results. We aimed to carry out a meta-analysis to investigate this.

MATERIALS AND METHODS

We assessed this association with categorical and dose-response meta-analysis of data from prospective cohort studies. Relevant studies were identified by searching MEDLINE, EMBASE, and OVID for studies published before 9 June 2012, with no restrictions. Relative risks (RRs) and 95% confidence intervals (CIs) for the highest versus lowest and dose-response association were estimated using random-effects models. Heterogeneity and publication bias was investigated, and subgroup, sensitivity, and meta-regression analyses were carried out.

RESULTS

The analysis included 333 510 participants with 7435 colorectal cancers from seven prospective cohort studies. The summary RR for the highest versus the lowest intake of dietary magnesium was 0.81 (95% CI: 0.70-0.92) for colorectal cancer, 0.76 (95% CI: 0.64-0.88) for colon cancer, and 0.82 (95% CI: 0.58-1.06) for rectal cancer. For men and women, the pooled RR was 0.76 (95% CI: 0.51-1.01) and 0.81 (95% CI: 0.68-0.94), respectively. Significant inverse associations of colorectal cancer and dietary magnesium emerged in nonlinear models (p nonlinearity=0.03). The greatest risk reduction was observed when dietary magnesium intake increased from very low levels.

CONCLUSION

Dietary magnesium intake has a statistically significant nonlinear inverse association with the risk of colorectal cancer. The greatest reduction for magnesium intake is 200-270 mg/day. Whether the association is causal or because of confounding warrants further investigation.

Lifestyle and colorectal cancer: A case-control study

A case-control study has been conducted to investigate the relationship between lifestyle and risk of colorectal cancer. Cases are one hundred patients diagnosed with colon and rectal cancer in Tokai University Hospital between 1986 and 1994. Three controls per case were individually matched by age, sex, local areas and date of health checkups at the Automated Multi-phasic Health Testing and Services (AMHTS ) Center of the hospital. The results were analyzed by multi-factorial logistic regression models. Positive history of maternal cancer, large consumption of alcohol, frequent consumption of potato products and white-collar job were predominant risk factors while frequent intake of seaweed was a protective factor. Frequent intakes of dairy foods and lack of exercise showed no significant tendency to increase risk of colorectal cancer. Smoking habits, intakes of meat and egg were shown not to be related to this disease. These findings suggest that family history of cancer and dietary factors play a key role in causation and prevention of colorectal cancer.

Magnesium intake and colorectal tumor risk: a case-control study and meta-analysis

BACKGROUND

Dietary magnesium might be related to colorectal tumor risk through the pivotal roles of magnesium in cellular metabolism, insulin resistance, and systemic inflammation.

OBJECTIVE

We evaluated the hypothesis of whether higher dietary magnesium intake is associated with reduced colorectal tumor risk.

DESIGN

A case-control study on colorectal adenomas (768 cases; 709 polyp-free control subjects) and a meta-analysis of colorectal adenomas (3 case-control studies) and carcinomas (6 prospective cohort studies) were conducted. Dietary magnesium was estimated from food-frequency questionnaires in the case-control study and most studies in the meta-analyses. Data analysis comprised multiple logistic regression analysis (case-control study) and fixed- and random-effects meta-analyses.

RESULTS

The case-control study showed a nonsignificant inverse association between dietary magnesium intake and risk of colorectal adenomas (OR for every 100-mg/d increase: 0.81; 95% CI: 0.62, 1.06). However, inverse associations were observed only in subjects with BMI (in kg/m²) ≥25, in subjects aged ≥55 y, and for advanced adenomas. Associations did not vary by the calcium-to-magnesium intake ratio. In the meta-analysis, every 100-mg/d increase in magnesium intake was associated with 13% lower risk of colorectal adenomas (OR: 0.87; 95% CI: 0.75, 1.00) and 12% lower risk of colorectal cancer (RR: 0.88; 95% CI: 0.81, 0.97).

CONCLUSIONS

Our findings support the hypothesis that higher intakes of dietary magnesium are associated with lower risk of colorectal tumors. The consumption of magnesium-rich foods may be a new avenue to explore further in the search for cancer-prevention strategies.

Coffee consumption and risk of colorectal cancer: a meta-analysis of observational studies

Objective

Separate meta-analyses based on case–control and cohort studies have reported different results on the relationship between coffee consumption and colorectal cancer risk. To clarify the effect of coffee intake on colorectal cancer risk, we performed a meta-analysis based on both case–control and cohort studies.

Design

Review study.

Setting

We identified case–control and cohort studies related to coffee consumption and colorectal cancer risk listed on MEDLINE, the Cochrane Controlled Trials Register, EMBASE, Science Citation Index and PubMed (until May 2011).

Subjects

Research literature on the relationship between coffee consumption and colorectal cancer risk.

Results

Twenty-five case–control (15 522 cases) and sixteen cohort studies (10 443 cases) were included in the meta-analysis. Comparing the highest v. the lowest/non category of coffee consumption, the combined results from case–control studies showed a significant relationship with colorectal cancer (OR = 0·85, 95 % CI 0·75, 0·97) and colon cancer (OR = 0·79, 95 % CI 0·67, 0·95), but not rectal cancer (OR = 0·95, 95 % CI 0·79, 1·15). For cohort studies, there was a slight suggestion of an inverse association with colorectal cancer (relative ratio = 0·94; 95 % CI 0·88, 1·01) and colon cancer (OR = 0·93, 95 % CI 0·86, 1·01), rather than rectal cancer (OR = 0·98, 95 % CI 0·88, 1·09). In subgroup analyses using case–control studies, significant inverse associations were found in females for colorectal cancer and in Europe for colorectal and colon cancer, while the subgroup analyses of cohort studies found that coffee drinks substantially decreased risk of colon cancer only in Asian women.

Conclusions

Results from case–control studies suggest coffee consumption can significantly decrease the risks of colorectal cancer and colon cancer, especially in Europe and for females.

Coffee consumption and risk of colorectal cancer: a meta-analysis of case-control studies

A meta-analysis of case-control studies on coffee consumption and colorectal cancer risk was conducted. Twenty-four eligible studies published before May 2010 were identified, including a total of 14,846 cases of colorectal, colon or rectal cancer. Compared to non/occasional drinkers, the odds ratios (OR) for drinkers were 0.83 (95% CI 0.73-0.95) for colorectal, 0.93 (95% CI 0.81-1.07) for colon and 0.98 (95% CI 0.85-1.13) for rectal cancer, with significant heterogeneity among studies; the corresponding ORs for the increment of 1 cup/day were 0.94 (95% CI 0.91-0.98), 0.95 (95% CI 0.92-0.98), and 0.97 (95% CI 0.95-0.99). For the highest coffee drinkers, the ORs were 0.70 (95% CI 0.60-0.81) for colorectal cancer, 0.75 (95% CI 0.64-0.88) for colon cancer and 0.87 (95% CI 0.75-1.00) for rectal cancer, when compared to non/low drinkers. The results of this meta-analysis of case-control studies suggest a moderate favorable effect of coffee consumption on colorectal cancer risk. The reduced risk was consistent across study design (hospital vs. population based), geographic area, and various confounding factors considered. It may reflect a real protection but also partly or largely be due to reverse causation, i.e. decreased coffee consumption among cases following the onset of bowel symptoms.

Meta-analysis of animal fat or animal protein intake and colorectal cancer

BACKGROUND

In the recent World Cancer Research Fund/American Institute for Cancer Research report of diet and cancer, it was concluded that there is limited but suggestive evidence that animal fat intake increases the risk of colorectal cancer.

OBJECTIVE

To clarify this potential relation, we conducted meta-analyses across a variety of subgroups, incorporating data from additional studies.

DESIGN

Analyses of high compared with low animal fat intakes and categorical dose-response evaluations were conducted. Subgroup analyses, consisting of evaluations by study design, sex, and tumor site were also performed.

RESULTS

Six prospective cohort studies with comprehensive dietary assessments, contributing 1070 cases of colorectal cancer and approximately 1.5 million person-years of follow-up, were identified. The summary relative risk estimate (SRRE) for these studies was 1.04 (95% CI: 0.83, 1.31; P for heterogeneity = 0.221) on the basis of high compared with low intakes. When data from case-control studies were combined with the cohort data, the resulting SRRE was 1.15 (95% CI: 0.93, 1.42) with increased variability (P for heterogeneity = 0.015). In our dose-response analysis of the cohort studies, no association between a 20-g/d increment in animal fat intake and colorectal cancer was observed (SRRE: 1.02; 95% CI: 0.95, 1.09). In a separate analysis of 3 prospective cohort studies that reported data for animal protein or meat protein, no significant association with colorectal cancer was observed (SRRE: 0.90; 95% CI: 0.70, 1.15).

CONCLUSION

On the basis of the results of this quantitative assessment, the available epidemiologic evidence does not appear to support an independent association between animal fat intake or animal protein intake and colorectal cancer.

Dietary vitamin B6 intake and the risk of colorectal cancer

Vitamin B6, a coenzyme in the folate metabolism pathway, may have anticarcinogenic effects. Laboratory and epidemiologic studies support the hypothesis of its protective effect against colorectal cancer (CRC). The aim of this large Scottish case-control study, including 2,028 hospital-based cases and 2,722 population-based controls, was to investigate the associations between dietary and supplementary intake of vitamin B6 and CRC. Three logistic regression models adjusted for several confounding factors, including energy, folate, and fiber intake, were applied in the whole sample and after age, sex, cancer site, folate, MTHFR C677T (rs1801133), MTHFR A1298C (rs1801131), MTR A2756G (rs1805087), and MTRR A66G (rs1801394) stratification (analysis on genotypes on 1,001 cases and 1,010 controls < or =55 years old). Moderately strong inverse and dose-dependent associations in the whole sample were found between CRC risk and the intake of dietary and total vitamin B6 in all three models [model III: odds ratio (OR), 0.77; 95% confidence interval (95% CI), 0.61-0.98; P for trend = 0.03; OR, 0.86; 95% CI, 0.69-1.07; P for trend = 0.12]. In addition, meta-analyses of published studies showed inverse associations between vitamin B6 and CRC (combined relative risk, 0.81; 95% CI, 0.68-0.96; test for overall effect P = 0.01; combined odds ratio, 0.67; 95% CI, 0.60-0.75; test for overall effect P < 0.00001). Analysis within the stratified subgroups showed similar associations apart from a stronger effect among < or =55-year-old individuals. Evidence from larger cohort and experimental studies is now required to confirm and define the anticarcinogenic actions of vitamin B6 and to explore the mechanisms by which this effect is mediated.

Diet, gender, and colorectal neoplasia

The association between diet and colorectal cancer has been studied in depth for many decades, with equivocal results. It has been hypothesized that cancers arising in the distal and proximal colon have different pathologies, and therefore different risk factors. As such, it is possible that diet-related factors might influence colorectal neoplasia differently depending on the subsite. Recent evidence indicates that women may be more likely to develop proximal cancers than men. Additionally, the link between certain dietary factors and colorectal neoplasia in women seems to vary by menopausal status. Given these observations, women may be affected differently than men by diet-related factors. The objective of this article was therefore to review the data for diet and colorectal adenomas and cancer, and then attempt to address the potential differences in the association of diet-related factors and colorectal neoplasia in men and women. For total energy intake, selenium, and fiber, it seems that there may be slightly stronger effects in men as compared with women, whereas calcium and folate seem to affect both sexes similarly. With regard to vitamin D and colorectal cancer, women may exhibit stronger associations than men. Perhaps the most evidence for a sex-specific effect is observed for obesity, where more substantial direct relationships between body size and colorectal neoplasia have been reported for men than for women. However, this observation may be influenced by the differential effects in women by menopausal status. Further research on sex-specific dietary effects is warranted.

The effect of lactose maldigestion on the relationship between dairy food intake and colorectal cancer: a systematic review

Dairy food consumption has been inconsistently shown to protect against colorectal cancer (CRC) in case-based studies, and no clear benefits against recurrent colonic polyps (CRP) have been reported. Based on population-based studies we have hypothesized that dairy food intake may have anti-CRC effects at both low intake lactase non-persistent (LNP) populations and at high intake lactase persistent (LP) subjects. We separately analyse existing case-based studies and divide origins into high LNP (>or= 80% LNP prevalence), low LNP (prevalence <or= 20%) and mid LNP countries (21-79% prevalence), which coincide with low, high, and mid quantity dairy food intake regions, respectively. Odds ratios and relative risks (RR) of highest versus lowest dairy intake within each group are analyzed together for assessment of protection against CRC and CRP. Eighty studies met stipulated criteria. Thirteen analyzed the effect on recurrent polyps. Forest plots from 2 regions, high LNP (low dairy food intake) RR = 0.84 [95% confidence interval (CI) = 0.73-0.97) and low LNP (high dairy food intake) RR = 0.80 (95% CI = 0.73-0.88) demonstrated significant protection against CRC. In mixed LNP/LP populations (mid dairy food intake) nonsignificant protection was found RR = 0.92 (95% CI = 0.79-1.06). Similar regional analysis for CRP failed to show significant protective effect in any region. This meta-analysis supports that the highest level of dairy food consumption protects subjects in both high and low LNP regions but not in areas with significant mixed LNP/LP populations. In both groups, dairy foods had no effect on polyp formation, suggesting it may only protect against CRC at late stages of promotion. These results raise the possibility that LNP/LP status may be partly responsible for the discrepant results with respect to the relationship between dairy food consumption and CRC.

Fruit and vegetable consumption and risk of colorectal cancer in Japan: The Miyagi Cohort Study

Objective

Adequate fruit and vegetable intake has been suggested to protect against colorectal cancer. However, several recent prospective studies have reported no association. We therefore examined the association between fruit and vegetable intakes and the risk of colorectal cancer in a prospective cohort study in Japan.

Design

Between June and August 1990, 47 605 Japanese men and women completed a self-administered questionnaire, including a food-frequency questionnaire. We divided the subjects into quartiles based on their self-reported fruit and vegetable consumption. There were 165 colon cancer and 110 rectal cancer incidences identified during 7 years of follow-up, to the end of December 1997. We used Cox proportional hazards models to estimate the relative risk (RR) of developing colorectal cancer according to the level of fruit and vegetable consumption, applying adjustments for potential confounders.

Results

No statistically significant association was observed between fruit and vegetable consumption and the risk of colorectal cancer. The multivariate RR of colon cancer in the highest quartile of fruit and vegetable intake compared with the lowest was 1.13 (95% confidence interval (CI) 0.73–1.75), the RR for vegetables alone was 1.24 (95% CI 0.79–1.95) and that for fruit alone was 1.45 (95% CI 0.85–2.47). The corresponding multivariate RRs for rectal cancer were 1.12 (95% CI 0.67–1.89), 1.14 (95% CI 0.67–1.93) and 1.41 (95% CI 0.73–2.73).

Conclusions

We found no association between the consumption of fruit and vegetables and the risk of colorectal cancer among the Japanese population.

Coffee consumption and risk of colorectal cancer in a population-based prospective cohort of Japanese men and women

We prospectively examined the association between coffee consumption and the risk of developing colorectal cancer in a large population-based cohort study (the JPHC Study) of Japanese men and women. Data were analyzed from a population-based cohort of 96,162 subjects (46,023 men and 50,139 women). A total of 1,163 incident colorectal cancers were identified during the follow-up period, including 763 cases of colon cancer and 400 of rectal cancer. We observed a significant inverse association between coffee consumption and the risk of developing invasive colon cancer among women. Compared with those who almost never consumed coffee, women who regularly consumed 3 or more cups of coffee per day had a RR of 0.44 (95% CI = 0.19-1.04; p for trend = 0.04) after adjustment for potential confounding factors. However, no significant association was found for rectal cancer in women. In men, no significant decrease was observed in any colorectal cancer site. Further, additional analyses on the association of green tea consumption with colorectal cancer risk found no significant association in men or women. These findings suggest that coffee consumption may lower the risk of colon cancer among Japanese women.

Folate, vitamin B6, multivitamin supplements, and colorectal cancer risk in women

The authors evaluated associations between intakes of folate and vitamin B(6) and colorectal cancer risk among women enrolled in a randomized trial on aspirin and vitamin E in disease prevention. At baseline (1992-1995), 37,916 US women aged >or=45 years who were free of cancer and cardiovascular disease provided dietary information. During an average of 10.1 years of follow-up (through February 20, 2004), 220 colorectal adenocarcinoma cases were documented. Total folate and vitamin B(6) intakes were not significantly associated with the risk of colorectal cancer. However, dietary intakes of folate and vitamin B(6) were significantly inversely associated with colorectal cancer risk among women who were not taking supplements containing folate and vitamin B(6). Multivariable relative risks among women in the highest quintiles of intake versus the lowest were 1.16 (95% confidence interval (CI): 0.76, 1.79) for total folate, 1.14 (95% CI: 0.77, 1.69) for total vitamin B(6), 0.46 (95% CI: 0.26, 0.81) for dietary folate, and 0.69 (95% CI: 0.41, 1.15) for dietary vitamin B(6). The use of multivitamin supplements was not related to colorectal cancer risk. These findings suggest that higher dietary intakes of folate and vitamin B(6) may reduce the risk of colorectal cancer in women. An alternative explanation is that other factors related to dietary intakes of folate and vitamin B(6) account for the inverse associations.

Searching one or two databases was insufficient for meta-analysis of observational studies

OBJECTIVE

To address methodologic issues in searching for observational studies by presenting database search methods and results.

STUDY DESIGN AND SETTING

Results of two literature searches for publications reporting on observational studies of alcohol consumption and the risk of breast cancer and large bowel cancer were compared, to evaluate the sensitivity of various bibliographic databases and search strategies, including hand-searching reviews and meta-analyses.

RESULTS

The target sensitivity of 90% of publications in the breast cancer search was achieved by starting with Medline, then adding Biosis, Embase, and SCI EXPANDED-SSCI, which provided a total of 72 (91%) of the 79 relevant publications. To reach a similar 89% sensitivity for large bowel cancer, at least Biosis, Dissertation Abstracts Online, Embase, ETOH, and Medline had to be searched, with the addition of hand search of reviews and meta-analyses.

CONCLUSION

Limiting a search to one or two databases when conducting meta-analyses of observational studies will not provide a thorough summary of the existing literature. The findings support recommendations to implement a comprehensive search of electronic databases and the reference lists of recent review articles and meta-analyses.

Plasma vitamin B6 and the risk of colorectal cancer and adenoma in women

BACKGROUND

Vitamin B6, whose main circulating form is pyridoxal 5'-phosphate (PLP), is important in one-carbon metabolism, which is critical for DNA synthesis and DNA methylation, both of which are potentially involved in colorectal carcinogenesis. However, no previous epidemiologic studies have directly evaluated the association of plasma PLP with risk for colorectal neoplasia.

METHODS

We conducted a prospective nested case-control study of 32,826 female participants of the Nurses' Health Study who provided blood specimens in 1989-1990. From 1989-1990 to 2000 (1998 for adenoma), a total of 194 incident colorectal cancer cases and 410 incident colorectal adenoma cases were identified from medical records. Multivariable-adjusted relative risks (RRs) and 95% confidence intervals (CIs) were calculated using logistic regression. All statistical tests were two-sided.

RESULTS

A suggestive inverse association was observed between plasma PLP concentration and risk for colorectal cancer when comparing the highest quartile versus the lowest (RR = 0.56, 95% CI = 0.31 to 1.01; P(trend) = .07); the association of PLP concentration with colon cancer was statistically significant (RR = 0.42, 95% CI = 0.21 to 0.85; P(trend) = .02). Both associations were statistically significant and stronger after controlling for intakes of folate, of multivitamins, and of methionine (for colorectal cancer, RR = 0.48, 95% CI = 0.25 to 0.92; P(trend) = .03; for colon cancer, RR = 0.38, 95% CI = 0.18 to 0.80; P(trend) = .01). Total vitamin B(6) intake was also statistically significantly inversely associated with colon cancer risk (RR = 0.51, 95% CI = 0.27 to 0.97; P(trend) = .007). There was a suggestive inverse association between plasma PLP concentration and advanced distal colorectal adenoma (RR = 0.65, 95% CI = 0.37 to 1.11; P(trend) = .08), but the association with early-stage adenoma was weaker (RR = 0.85, 95% CI = 0.52 to 1.38; P(trend) = .52).

CONCLUSIONS

Our results suggest that vitamin B6 may be inversely associated with risk of colorectal neoplasia.

Primary prevention of colorectal cancer: lifestyle, nutrition, exercise

The past two decades have provided a vast amount of literature related to the primary prevention of colorectal cancer. Large international variation in colorectal cancer incidence and mortality rates and the prominent increases in the incidence of colorectal cancer in groups that migrated from low- to high-incidence areas provided important evidence that lifestyle factors influence the development of this malignancy. Moreover, there is convincing evidence from epidemiological and experimental studies that dietary intake is an important etiological factor in colorectal neoplasia. Although the precise mechanisms have not been clarified, several lifestyle factors are likely to have a major impact on colorectal cancer development. Physical inactivity and to a lesser extent, excess body weight, are consistent risk factors for colon cancer. Exposure to tobacco products early in life is associated with a higher risk of developing colorectal neoplasia. Diet and nutritional factors are also clearly important. Diets high in red and processed meat increase risk. Excess alcohol consumption, probably in combination with a diet low in some micronutrients such as folate and methionine, appear to increase risk. There is also recent evidence supporting a protective effect of calcium and vitamin D in the etiology of colorectal neoplasia. The relationship between intake of dietary fiber and risk of colon cancer has been studied for three decades but the results are still inconclusive. However, some micronutrients or phytochemicals in fiber-rich foods may be important; folic acid is one such micronutrient that has been shown to protect against the development of colorectal neoplasia and is currently being studied in intervention trials of adenoma recurrence. The overwhelming evidence indicates that primary prevention of colon cancer is feasible. Continued focus on primary prevention of colorectal cancer, in combination with efforts aimed at screening and surveillance, will be vital in attaining the greatest possible progress against this complex, yet highly preventable disease.

Dietary Glycemic Load, Carbohydrate, Sugar, and Colorectal Cancer Risk in Men and Women

Hyperinsulinemia may explain excess colorectal cancer among individuals who are overweight or inactive. Recent studies have observed elevated colorectal cancer risk among individuals with elevated insulin levels 2 hours after oral glucose challenge or with elevated plasma C-peptide levels. The effect of consuming a high glycemic diet on colorectal risk, however, remains uncertain. Two prospective cohort studies, the Nurses' Health Study and the Health Professionals Follow-up Study, contributed up to 20 years of follow-up. After exclusions, 1,809 incident colorectal cancers were available for analyses. Dietary glycemic load (GL) was calculated as a function of glycemic index (postprandial blood glucose response as compared with a reference food), carbohydrate content, and frequency of intake of individual foods reported on food frequency questionnaires. Multivariable Cox proportional hazards models were used to adjust for potential confounders. Intakes of dietary carbohydrate, GL, overall glycemic index, sucrose, and fructose were not associated with colorectal cancer risk in women. A small increase in risk was observed in men with high dietary GL (multivariate relative risk, 1.32; 95% confidence interval, 0.98-1.79; highest versus lowest quintile), sucrose or fructose (multivariate relative risk, 1.37; 95% confidence interval, 1.05-1.78; highest versus lowest quintile of fructose, P = 0.008). Associations were slightly stronger among men with elevated body mass index (≥25 kg/m2). Results among women were similar after stratifying by body mass index or physical activity. High intakes of GL, fructose, and sucrose were related to an elevated colorectal cancer risk among men. For women, however, these factors did not seem to increase the risk of colorectal cancer.

Effect of diet, life style, and other environmental/chemopreventive factors on colorectal cancer development, and assessment of the risks

This review presents a comprehensive, evenhanded evaluation of the evidence from experimental, in vitro and human studies associating environmental and therapeutic factors with risk of colorectal cancer. Life styles correlated with the greatest increase in colorectal cancer risk are the ones that typify a diet rich in fat and calories, alcohol drinking and tobacco smoking, and low intake of vegetable, fruits and fibers, referred to as a "western diet," as well as sedentary style (i.e., no- or low-exercise). This kind of life style has also been associated with other chronic diseases (other cancers, obesity, dyslipedemia, diabetes, hypertension cardiovascular, and hypertension). The evidence does not implicated red meat as a risk factor, and fiber has been shown to protect against colorectal adenomas and carcinomas. Calcium, vitamin D, folate, and some antioxidant vitamins and minerals (gamma-tocopherol and selenium) have protective effects, and daily exercise for > or =30 min results in a significant decrease in risk. Estrogen use (hormone replacement therapy) substantially reduces colorectal cancer risk in postmenopausal women. Nonsteroidal anti-inflammatory drugs (e.g., aspirin) in excessive doses is protective, especially in high risk populations, but the side effects of its use and cost incurred due to its continued intake over long periods must be carefully scrutinized before any recommendations are made for the general public.

Epidemiologic evidence of the protective effect of fruit and vegetables on cancer risk

BACKGROUND

Diets rich in fruit and vegetables have been recommended for preventing cancer. The evidence supporting this recommendation is based on observational studies, although results of several prospective studies have cast some doubts on whether fruit and vegetables are associated with cancer risk reduction.

OBJECTIVE

We sought to summarize evidence from case-control and prospective studies on fruit and vegetable intake and cancer risk with a meta-analytic approach.

DESIGN

Published case-control and cohort studies that reported on total vegetable and fruit intake and risk of cancer of several sites were included. Relative risks were estimated by using linear logistic regression models.

RESULTS

Case-control studies overall support a significant reduction in the risks of cancers of the esophagus, lung, stomach, and colorectum associated with both fruit and vegetables; breast cancer is associated with vegetables but not with fruit; and bladder cancer is associated with fruit but not with vegetables. The overall relative risk estimates from cohort studies suggest a protective effect of both fruit and vegetables for most cancer sites considered, but the risk reduction is significant only for cancers of the lung and bladder and only for fruit.

CONCLUSIONS

Prospective studies provide weaker evidence than do case-control studies of the association of fruit and vegetable consumption with reduced cancer risk. The discrepancies may be related to recall and selection biases in case-control studies. In contrast, the association may have been underestimated in prospective studies because of the combined effects of imprecise dietary measurements and limited variability of dietary intakes within each cohort.

Fish consumption and colorectal cancer: a case-reference study in Japan

Several clinical studies have suggested that supplementation with fish oils can suppress the proliferation of colorectal mucosa and therefore inhibit the development of colorectal cancer. However, epidemiological evidence concerning fish consumption and risk is inconsistent and limited. To clarify the association between intake of fish and the likelihood of developing colorectal cancer, we conducted a large sample size case-reference study with 928 cases of colon cancer, 622 of rectal cancer and 46886 cancer-free outpatient references aged 40-79 years. The data showed frequent raw/cooked fish intake to be associated with decreased odds ratio (OR) 0.68 with 95% confidence interval (CI) 0.47-0.99 for male colon cancer, especially for males aged over 60 years, smokers and frequent meat eaters. A marginal decrease in the OR (OR 0.58, 95% CI 0.31-1.07) was also detected for female rectal cancer, especially in the regular physical exercise subgroup. However, frequent dried/salted fish intake was found to be associated with increased OR in females younger than 60 years old and alcohol drinkers. Although there is some possible bias in epidemiological studies, the results suggest that frequent raw/cooked fish intake may decrease the risk while dried/salted fish, in contrast, may exert a detrimental effect.

Diet, body weight, and colorectal cancer: a summary of the epidemiologic evidence

Colorectal cancer is the second leading cause of cancer death in the United States, and the number of new cases annually is approximately equal for men and women. Several nutritional factors are likely to have a major influence on risk of this cancer. Physical inactivity and excessive adiposity, especially if centrally distributed, clearly increase the risk of colon cancer. Hyperinsulinemia may be an important underlying risk factor. In conjunction with obesity and physical inactivity, which induce a state of insulin resistance, certain dietary patterns that stimulate insulin secretion, including high intakes of red and processed meats, saturated and trans-fats, and highly processed carbohydrates and sugars, may increase the risk of colon cancer. There is evidence suggesting that some component of red meat may independently increase the risk of colorectal cancer, and some micronutrients may be important as protective agents. Currently, the evidence is strongest for folate and calcium. Folate may be especially important in alcohol drinkers because alcohol appears to increase the risk, particularly when folate intake is low. This interaction may be related to the antifolate properties of alcohol. In contrast to earlier studies, more recent epidemiologic studies have generally not supported a strong influence of dietary fiber or fruits and vegetables, although these have other health benefits, and their consumption should be encouraged. The majority of colon cancers, as well as many other conditions, may be prevented by lifestyle alterations in the intake of these nutritional factors, in addition to other factors, such as smoking.

Dairy products and colorectal cancer. A review of possible mechanisms and epidemiological evidence

OBJECTIVES

This review provides an overview of the principal hypotheses and epidemiological evidence of the possible links between colorectal cancer and intake of milk and/or dairy products.

METHODS

The first section outlines the main hypotheses about the possible effect of calcium, vitamin D, fats and other milk components. The possible role of acid lactic bacteria in fermented products is also discussed. The second section is a summary of the published epidemiological evidence. The results on milk, cheese and yoghurt are summarized using a meta-analytical approach. The results of studies on calcium and vitamin D are briefly described.

RESULTS

Case-control studies are heterogeneous and, on average, do not provide evidence of association between total intake of total dairy products, milk, cheese or yoghurt and colorectal cancer risk. The average result from cohort studies support the hypothesis of a protective effect of total dairy products (odds ratio (OR): 0.62; 95% confidence interval (CI): 0.52-0.74; P heterogeneity test: 0.93) and for milk (OR: 0.80; 95% CI: 0.68-0.95; P heterogeneity: 0.77). No association was found between cheese (OR: 1.10; 95% CI: 0.88-1.36; P heterogeneity: 0.55) or yoghurt (OR: 1.03; 95% CI: 0.83-1.28; P heterogeneity: 0.69) in cohort studies.

CONCLUSIONS

Cohort studies consistently found a protective effect of total dairy products and milk intake, but the evidence is not supported by case-control studies. No relationship was found with cheese or yoghurt intake. As the number of cohort studies is still limited, their results need to be confirmed by other prospective studies.

Modifiable risk factors for colon cancer

Although many mechanisms remain unclear, a large body of evidence indicates that several dietary and lifestyle factors are likely to have a major influence on the risk of colon cancer. Physical inactivity, excess body weight, and a central deposition of adiposity are consistent risk factors. Overconsumption of energy is likely to be one of the major contributors to the high rates of colon cancer in Western countries. Beyond their influence on energy balance, the independent role of specific macronutrients remain controversial. Red meat, processed meats, and perhaps refined carbohydrates contribute to risk. Recent evidence indicate that chronic hyperinsulinemia may increase risk of colon cancer. As insulin resistance and subsequent hyperinsulinemia is induced by excess energy intake and some aspects of the Western diet (e.g., saturated fats and refined carbohydrates), insulin may be a focus of factors influencing colon cancer risk. Recent evidence also points to a role of IGF-1, but our understanding of modifiable factors that influence levels of these is poor at present. Of note is that hyperinsulinemia increases free IGF-1 exposure [25]. High alcohol consumption, probably in combination with a diet low in some micronutrients such as folate and methionine, and smoking early in life are likely to increase risk of colon cancer. Recent epidemiologic studies have tended not to support a strong influence of fiber; instead, some micronutrients or phytochemicals in fiber-rich foods may be important. Folate is one such nutrient that has received attention lately and is being studied in randomized intervention trials. Agents with chemopreventive properties, such as aspirin and postmenopausal estrogens, have potential adverse effects so a careful consideration of the risk-benefit ratio is required before general recommendations can be made. Other NSAIDs with a potential for reduced toxicity, such as celecoxib, are currently being evaluated for efficacy and toxicity. The overwhelming evidence indicates that primary prevention of colon cancer is feasible. At least 70% of colon cancers may be preventable by moderate changes in diet and lifestyle [197]. Secondary prevention, through screening by sigmoidoscopy and colonoscopy, is also critically important to prevent mortality from colon cancer; however, many of the diet and lifestyle risk factors for colon cancers are the same for cardiovascular disease and for some other cancers, so focusing on the modifiable risk factors for colon cancer is likely to have many additional benefits beyond this cancer.

Effect of age, period of diagnosis and birth cohort on large bowel cancer incidence in a well-defined French population, 1976-1995

The objective of this study was to present trends in colorectal cancer incidence by sex and subsite in a well-defined French population. All of the 4486 large bowel cancer cases registered between 1976 and 1995 in the Burgundy registry of digestive tract cancers was included in this study. Time trends in colorectal cancer incidence were analysed over the 1976-95 period. The effects of age, period and cohort were evaluated using a log-linear Poisson model. The incidence rates for right colon cancer increased over time: + 21.6% (95% CI: + 13.5; + 29.7) per 5-year period in males and +10.4% (95% CI: + 3.4; + 17.3) in females. Left colon cancer rates increased in males (+ 10.6% 95% CI: + 4.6; + 16.6). Left colon cancer in females and rectal cancer incidence rates did not significantly change. Between the 1901 cohort to the 1941 cohort, estimated cumulative risks for right colon cancer increased sharply. The increase was less marked for left colon and the cumulative risk for rectal cancer remained almost stable. Temporal trends were different by subsites and sexes. In conclusion, our results confirm the existence of different trends in colorectal cancer incidence between subsites and sexes. These differences probably reflect aetiological distinctions.

Dietary interventions to prevent disease

Changing dietary behaviors to prevent chronic disease has been an important research focus for the last 25 years. Here we present a review of published articles on the results of research to identify methods to change key dietary habits: fat intake, fiber intake, and consumption of fruits and vegetables. We divided the research reviewed into sections, based on the channel through which the intervention activities were delivered. We conclude that the field is making progress in identifying successful dietary change strategies, but that more can be learned. Particularly, we need to transfer some of the knowledge from the individual-based trials to community-level interventions. Also, more research with rigorous methodology must be done to test current and future intervention options.

Flavonoids and steroid hormone-dependent cancers

Steroid-hormone dependent cancers, including those of the breast, prostate and colon, are leading causes of morbidity and mortality in western countries. In rural Asian areas, these diseases are relatively uncommon. Dietary factors, including low consumption of fruit, vegetables and soy in the west have been shown in various epidemiologic studies as reasons for these differences. This review discusses flavonoids, one component of these plant foods that is being investigated for their role in chemoprevention. Epidemiological, in vitro, animal and human studies shall be explored to look at mechanisms involved, including steroid hormone activity, effects on cell growth, antioxidant activities, inhibition of chemical carcinogenesis and influences on modulators of cancer risk. Although the in vitro and animal models point to several pathways by which flavonoids may reduce incidence of these cancers, the clinical data are still relatively lacking. More research is needed to determine how best to use foods containing these compounds to reduce steroid hormone-dependent cancer risk.

Glycemic index in chronic disease: a review

AIM

The intent of this review is to critically analyze the scientific evidence on the role of the glycemic index in chronic Western disease and to discuss the utility of the glycemic index in the prevention and management of these disease states.

BACKGROUND

The glycemic index ranks foods based on their postprandial blood glucose response. Hyperinsulinemia and insulin resistance, as well as their determinants (eg high energy intake, obesity, lack of physical activity) have been implicated in the etiology of diabetes, coronary heart disease and cancer. Recently, among dietary factors, carbohydrates have attracted much attention as a significant culprit, however, different types of carbohydrate produce varying glycemic and insulinemic responses. Low glycemic index foods, characterized by slowly absorbed carbohydrates, have been shown in some studies to produce beneficial effects on glucose control, hyperinsulinemia, insulin resistance, blood lipids and satiety.

METHOD

Studies on the short and long-term metabolic effects of diets with different glycemic indices will be presented and discussed. The review will focus primarily on clinical and epidemiological data, and will briefly discuss in vitro and animal studies related to possible mechanisms by which the glycemic index may influence chronic disease.

Primary prevention of colorectal cancer: diet and drugs

Primary prevention of colonic adenomas and cancer through dietary interventions or chemoprevention has great appeal. This article discusses primary prevention goals and promising nutritional or chemopreventive strategies. There is substantial observational evidence that diets high in total calories and fat and or low in fruits and vegetables or total fiber as well as low levels of physical activity are related to the risk of colonic neoplasia. Similar observational data indicate that diets high in specific nutrients such as antioxidant vitamins or calcium may be protective. The article describes some of the newer chemopreventive agents and reviews the data linking diet and lifestyle to colorectal cancer risk, focusing on interventions that have also been studied in prospective clinical trials. Finally the evidence supporting the role of non-steroidal anti-inflammatory drugs for the chemoprevention of CRC is reviewed and the status of several other promising newer agents that are entering human trials is summarized.

Meat consumption and colorectal cancer risk: dose-response meta-analysis of epidemiological studies

The hypothesis that consumption of red and processed meat increases colorectal cancer risk is reassessed in a meta-analysis of articles published during 1973-99. The mean relative risk (RR) for the highest quantile of intake vs. the lowest was calculated and the RR per gram of intake was computed through log-linear models. Attributable fractions and preventable fractions for hypothetical reductions in red meat consumption in different geographical areas were derived using the RR log-linear estimates and prevalence of red meat consumption from FAO data and national dietary surveys. High intake of red meat, and particularly of processed meat, was associated with a moderate but significant increase in colorectal cancer risk. Average RRs and 95% confidence intervals (CI) for the highest quantile of consumption of red meat were 1.35 (CI: 1.21-1.51) and of processed meat, 1.31 (CI: 1.13-1.51). The RRs estimated by log-linear dose-response analysis were 1.24 (CI: 1.08-1.41) for an increase of 120 g/day of red meat and 1.36 (CI: 1.15-1.61) for 30 g/day of processed meat. Total meat consumption was not significantly associated with colorectal cancer risk. The risk fraction attributable to current levels of red meat intake was in the range of 10-25% in regions where red meat intake is high. If average red meat intake is reduced to 70 g/week in these regions, colorectal cancer risk would hypothetically decrease by 7-24%.

Selenoprotein levels in patients with colorectal adenomas and cancer

OBJECTIVES

Selenium is a trace mineral that, as a constituent of certain selenoproteins, acts as an antioxidant. Results of studies addressing a cancer protective effect of selenium have been controversial. The present study measured selenoprotein-P, extracellular glutathione peroxidase, and plasma selenium in patients with colon cancer and adenomatous colon polyps to determine whether patients who develop colorectal adenomas or cancer are selenium deficient.

METHODS

Patients who presented to an endoscopy center for colonoscopy or who were referred to our institution with a newly diagnosed colorectal cancer were offered enrollment in the trial. Each patient underwent phlebotomy, usually immediately after colonoscopy. In all, 103 patients were enrolled in the study. Of these, 33 patients were found to have colorectal cancer, 35 adenomatous colon polyps, and 17 normal examinations. A total of 18 patients had other diagnoses and were not included in the study group.

RESULTS

The mean age for the colorectal cancer group was 69 yr, for the adenomatous colon polyp group 62 yr, and for the normal group was 56 yr. The adenomatous colon polyp and normal groups were predominantly female. Based on one way analysis of variance tests, there was no significant difference in selenoprotein-P or plasma selenium levels or extracellular glutathione peroxidase activity among the three groups (p = 0.28, 0.098, and 0.35 respectively).

CONCLUSIONS

The present data suggest that patients with adenomatous colon polyps and those with colorectal cancer are not selenium deficient.

Diet and cancer

The large differences in cancer rates among countries, striking changes in these rates among migrating populations, and rapid changes over time within countries indicate that some aspect of lifestyle or environment is largely responsible for the common cancers in Western countries. Dietary fat has been hypothesized to be the key factor because national consumption is correlated with the international differences. However, detailed analyses in large prospective studies have not supported an important role of dietary fat. Instead, positive energy balance, reflected in early age at menarche and weight gain as an adult, is an important determinant of breast and colon cancers, consistent with numerous studies in animals. As a contributor to positive energy balance, and possibly by other mechanisms, physical inactivity has also been shown to be a risk factor for these diseases and in part accounts for the international differences. Although the percentage of calories from fat in the diet does not appear related to risk of colon cancer, greater risks have been seen with higher consumption of red meat, suggesting that factors other than fat per se are important. In many case-control studies, a high consumption of fruits and vegetables has been associated with reduced risks of numerous cancers, but recent prospective studies suggest these associations may have been overstated. Among the factors in fruits and vegetables that have been examined in relation to cancer risk, present data most strongly support a benefit of higher folic acid consumption in reducing risks of colon and breast cancers. These findings have been bolstered by an association between incidence of colon cancer and a polymorphism in the gene for methylenetetrahydrofolate reductase, an enzyme involved in folic acid metabolism. The benefits of folic acid appear strongest among persons who regularly consume alcohol, which itself is associated with risk of these cancers. Numerous other aspects of diet are hypothesized to influence the risks of cancers in Western countries, but for the moment the evidence is unclear.

Meat consumption and colorectal cancer: a review of epidemiologic evidence

This article reviews the epidemiologic evidence on colorectal cancer risk and meat consumption from 32 case-control and 13 cohort studies published in English from 1970 to 1999 and retrieved from the Medline database. The results support the hypothesis that meat consumption is associated with a modest increase in colorectal cancer risk. This association, however, seems to have been more consistently found for red meat and processed meat. The studies on cooking methods and meat "doneness" are not consistent and the evidence is not conclusive.