Diet and colorectal adenomas: a case-control study in Majorca

Practical Considerations in Diagnosing and Managing Early-Onset GI Cancers

The incidence of early-onset (EO) GI cancers occurring in individuals younger than age 50 years has been rising at an alarming rate over the past two decades. Although this rise in incidence among young patients correlates with increased rates of obesity, changes in diet, and alterations in the environment, the effects of these environmental factors on carcinogenesis, metastasis, and treatment response are unknown. Although several unique clinical trends exist among EO-GI cancers and their average-onset GI cancer counterparts, GI cancers are molecularly indistinct between younger and older patients, and no data support distinct treatment paradigms for patients with EO disease. The majority of EO-GI cancers are not explained by germline changes. There remains a critical need for further research to understand the pathogenesis and optimal management of EO-GI cancers. In addition, current screening strategies are not adequate to identify EO-GI cancers, and early biomarkers are needed. Specialized centers, with a focus on psychosocial aspects of cancer management, can address the unique care needs of patients with EO-GI cancers.

Association between Dietary Fibre Intake and Colorectal Adenoma: A Systematic Review and Meta-Analysis

PubMed/Medline, Excerpta Medica dataBASE (EMBASE) and Scopus were searched in January 2021 in order to retrieve evidence assessing the association between dietary fibre intake and the risk of colorectal adenoma in adults. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for the reporting of results. Only primary observational studies were included. Publication bias was estimated through the Egger's test and the visual inspection of the funnel plot. Heterogeneity between studies was calculated with I2 statistics. The search strategy identified 683 papers, 21 of which were included in our meta-analysis. Having evaluated a total of 157,725 subjects, the results suggest a protective effect of dietary fibre intake against colorectal adenoma. Effect Size (ES) was [0.71 (95% CI = 0.68-0.75), p = 0.000)]. Moderate statistical heterogeneity (Chi2 = 61.68, df = 23, I2 = 62.71%, p = 0.000) was found. Findings show a statistically significant (p = 0.000) and robust association between a higher intake of dietary fibre and a lower risk of colorectal adenoma, considering both the prevalent and incident risk. Moreover, the meta-regression analysis showed a borderline significant negative linear correlation between the amount of dietary fibre intake and colorectal adenoma. Lastly, we performed a subgroup analysis by sex, showing a higher protective effect for men.

Independent associations of dairy and calcium intakes with colorectal cancers in the Adventist Health Study-2 cohort

OBJECTIVE

Results associating dairy and Ca intakes with colorectal cancer (CRC) risk have been mixed. Most previous analyses have suffered from confounding between dairy and Ca intakes. We examined independent associations between these variables, also dairy foods, and CRC incidence in a population with a large range of dairy intakes.

DESIGN

Adventist Health Study-2 is a cohort study where subjects were enrolled 2002-2007. Proportional hazard regression analyses were performed to estimate hazard ratios (HR). Regression calibration was used to correct for dietary measurement error.

SETTING

The population lived in all states of the USA.

SUBJECTS

There were 77712 analytic subjects, all of whom were Seventh-day Adventists. Much of their dietary Ca came from non-dairy sources.

SUBJECTS

During a mean follow-up of 7·8 years, 380 incident colon cancer and 111 incident rectal cancer cases were observed.

RESULTS

Comparing extreme quintiles of intake in measurement error-corrected analyses, dairy intake (HR=0·31; 95 % CI 0·09, 0·88), independent of total Ca, was inversely related with risk of rectal cancer but gave little indication of association with colon cancer. However, total Ca intake (independent of dairy) was associated with risk of colon cancer (HR=0·55; 95 % CI 0·28, 0·98) and there was little indication of association with rectal cancer. Traditional regression analyses and associations with macronutrients from dairy generally supported these results. Milk intake was also negatively associated with CRC (HR=0·63; 95 % CI 0·43, 0·89).

CONCLUSIONS

Dairy intake may decrease the risk of rectal cancer, and Ca may reduce risk of colon cancer and CRC.

Association Between Consumption of Fruits and Vegetables and Risk of Colorectal Adenoma: A PRISMA-Compliant Meta-Analysis of Observational Studies

There have been contradictory results about the association of fruits and vegetables intake with colorectal adenoma (CRA) risk, the precursor lesion of colorectal cancer. Herein, we have conducted a meta-analysis of the published observational studies to have a clear understanding about this association.Eligible studies up to November 30, 2014, were identified and retrieved by searching MEDLINE and EMBASE databases along with the manual review of the reference list of the retrieved studies. The quality of the included studies was evaluated using Newcastle-Ottawa Quality Assessment Scale, and random-effects model was used to calculate summary relative risk (SRR) and corresponding 95% confidence interval (CI).A total of 22 studies involving 11,696 CRA subjects were part of this meta-analysis. The SRR for the highest versus the lowest intake of vegetables alone was 0.91 (95% CI: 0.80-1.02, Pheterogeneity = 0.025), whereas for vegetables and fruits combined, it was 0.82 (95% CI: 0.75-0.91, Pheterogeneity = 0.369), and for fruits alone, it was 0.79 (95% CI: 0.71-0.88, Pheterogeneity = 0.111). In addition, linear dose-response analysis also showed similar results, for example, for per 100 g/d increment of fruits, the SRR was 0.94 (95% CI: 0.92-0.97) and for vegetables it was 0.98 (95% CI: 0.96-1.01). Nonlinear association was only observed for vegetables (Pnonlinearity = 0.024), but not for fruits (Pnonlinearity = 0.583).Thus, this meta-analysis suggested that fruits consumption have a significant protective effect on CRA risk, but not vegetables. Moreover, we recommend additional studies with prospective designs that use validated questionnaires and control for important confounders to further validate the overall results.

Sedentary behavior is associated with colorectal adenoma recurrence in men

PURPOSE

The association between physical activity and colorectal adenoma is equivocal. This study was designed to assess the relationship between physical activity and colorectal adenoma recurrence.

METHODS

Pooled analyses from two randomized, controlled trials included 1,730 participants who completed the Arizona Activity Frequency Questionnaire at baseline, had a colorectal adenoma removed within 6 months of study registration, and had a follow-up colonoscopy during the trial. Logistic regression modeling was employed to estimate the effect of sedentary behavior, light-intensity physical activity, and moderate-vigorous physical activity on colorectal adenoma recurrence.

RESULTS

No statistically significant trends were found for any activity type and odds of colorectal adenoma recurrence in the pooled population. However, males with the highest levels of sedentary time experienced 47% higher odds of adenoma recurrence. Compared to the lowest quartile of sedentary time, the ORs (95% CIs) for the second, third, and fourth quartiles among men were 1.23 (0.88, 1.74), 1.41 (0.99, 2.01), and 1.47 (1.03, 2.11), respectively (p(trend) = 0.03). No similar association was observed for women.

CONCLUSIONS

This study suggests that sedentary behavior is associated with a higher risk of colorectal adenoma recurrence among men, providing evidence of detrimental effects of a sedentary lifestyle early in the carcinogenesis pathway.

Total calcium intake and colorectal adenoma in young women

BACKGROUND

Total calcium intake appears to reduce occurrence of colorectal adenoma; however, the dose necessary for prevention in young women is unclear. We examined fine categories of calcium intake in relation to occurrence of first colorectal adenoma in a cohort of mostly premenopausal (88 %) women aged 26-60 at time of endoscopy.

DESIGN

We conducted an analysis among 41,403 participants in the Nurses' Health Study II and assessed intakes of calcium prior to endoscopy through participants' responses to biannual questionnaires.

RESULTS

Between 1991 and 2007, we documented 2,273 colorectal adenoma cases. There was a significant trend across categories of calcium intakes with lowest intakes suggestive of higher occurrence of adenoma (p = 0.03) and those in the distal colon (p = 0.03) and rectum (p = 0.04). Compared with 1,001-1,250 mg/day of calcium intake, ≤ 500 mg/day was suggestive of a modest increase in occurrence of adenoma (multivariable RR = 1.21, 95 % CI 0.90-1.61); there were also suggestions of an increased risk with >500 to ≤ 700 mg/day of calcium. The association between ≤ 500 mg/day of calcium intake and adenoma was stronger for multiple (RR = 2.27, 95 % CI 1.38, 3.72), large (≥ 1 cm) (RR = 2.01, 95 % CI 1.27, 3.21), and high-risk adenoma (≥ 1 cm or mention of villous histology/high-grade dysplasia) (RR = 1.76, 95 % CI 1.13, 2.72). No differences in associations were noted between jointly categorized calcium and phosphorus or magnesium intakes.

CONCLUSIONS

Our findings suggest that low intakes of calcium, <500 and possibly 500-700 mg/day, in younger women are associated with an increased risk of multiple and advanced colorectal adenoma.

Legume consumption and colorectal adenoma risk: a meta-analysis of observational studies

Background

The anticancer effects of legumes have been explored extensively, but evidence from epidemiologic studies on colorectal adenoma is controversial. We performed a meta-analysis to assess these issues.

Methods

A systemic search of several databases was conducted for relevant studies evaluating the relationship between legume intake and adenoma risk, with no language restriction, from January 1, 1966, to April 1, 2013.

Results

Three cohort and eleven case control studies with 8,380 cases and a total of 101,856 participants were included in the analysis; the pooled odds ratio (95% confidence interval) for the highest vs. lowest consumption categories was 0.83 (0.75–0.93), with moderate level of heterogeneity (I² = 25.9% and P = 0.146) based on a random effects model. A decreased risk of adenoma was also observed in most of our subgroup meta-analyses.

Conclusions

Higher intake of legumes significantly reduced the risk of colorectal adenoma in our meta-analysis. Nevertheless, due to possible confounders and bias, further investigations are warranted to confirm this relationship.

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.

Red and processed meat intake and risk of colorectal adenomas: a systematic review and meta-analysis of epidemiological studies

BACKGROUND

Current evidence indicates that red and processed meat intake increases the risk of colorectal cancer; however, the association with colorectal adenomas is unclear.

OBJECTIVE

To conduct a systematic review and meta-analysis of epidemiological studies of red and processed meat intake and risk of colorectal adenomas as part of the Continuous Update Project of the World Cancer Research Fund.

DESIGN

PubMed and several other databases were searched for relevant studies from their inception up to 31 December 2011. Summary relative risks (RRs) were estimated using a random effects model.

RESULTS

Nineteen case-control studies and seven prospective studies were included in the analyses. The summary RR per 100 g/day of red meat was 1.27 (95 % CI 1.16-1.40, I (2) = 5 %, n = 16) for all studies combined, 1.20 (95 % CI 1.06-1.36, I (2) = 0 %, n = 6) for prospective studies, and 1.34 (95 % CI 1.12-1.59, I (2) = 31 %, n = 10) for case-control studies. The summary RR per 50 g/day of processed meat intake was 1.29 (95 % CI 1.10-1.53, I (2) = 27 %, n = 10) for all studies combined, 1.45 (95 % CI 1.10-1.90, I (2) = 0 %, n = 2) for prospective studies, and 1.23 (95 % CI 0.99-1.52, I (2) = 37 %, n = 8) for case-control studies. There was evidence of a nonlinear association between red meat (p nonlinearity < 0.001) and processed meat (p nonlinearity = 0.01) intake and colorectal adenoma risk.

CONCLUSION

These results indicate an elevated risk of colorectal adenomas with intake of red and processed meat, but further prospective studies are warranted.

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.

Foods and food groups associated with the incidence of colorectal polyps: the Adventist Health Study

Colorectal cancer (CRC) is a leading cause of cancer death in the United States. The majority of CRC arise in adenomatous polyps and 25-35% of colon adenoma risk could be avoidable by modifying diet and lifestyle habits. We assessed the association between diet and the risk of self-reported physician-diagnosed colorectal polyps among 2,818 subjects who had undergone colonoscopy. Subjects participated in 2 cohort studies: the AHS-1 in 1976 and the AHS-2 from 2002-2005. Multivariate logistic regression analysis was used to estimate the period risk of incident cases of polyps; 441 cases of colorectal polyps were identified. Multivariate analysis adjusted by age, sex, body mass index, and education showed a protective association with higher frequency of consumption of cooked green vegetables (OR 1 time/d vs. <5/wk = 0.76, 95% CI = 0.59-0.97) and dried fruit (OR 3+ times/wk vs. <1 time/wk = 0.76, 95%CI = 0.58-0.99). Consumption of legumes at least 3 times/wk reduced the risk by 33% after adjusting for meat intake. Consumption of brown rice at least 1 time/wk reduced the risk by 40%. These associations showed a dose-response effect. High frequency of consumption of cooked green vegetables, dried fruit, legumes, and brown rice was associated with a decreased risk of colorectal polyps.

Folate intake and risk of colorectal cancer and adenoma: modification by time

BACKGROUND

Experimental and observational studies have suggested that folate may play dual roles in colorectal cancer risk depending on the timing and dose.

OBJECTIVE

We examined the latency between folate intake and the incidence of colorectal cancer.

DESIGN

We prospectively examined associations between folate intake assessed every 2 to 4 y by using validated food-frequency questionnaires and risk of colorectal cancer and adenoma in the Nurses' Health Study and Health Professionals Follow-Up Study, which included 2299 incident colorectal cancers and 5655 colorectal adenomas from 1980 to 2004.

RESULTS

There was an association between total folate intake 12-16 y before diagnosis and lower risk of colorectal cancer (relative risk: 0.69; 95% CI: 0.51, 0.94; ≥800 compared with <250 μg folate/d), but there was no association between intake in the recent past and colorectal cancer risk. Long- and short-term intakes of total folate were associated with a lower risk of colorectal adenoma, with a strong association with intake 4-8 y before diagnosis (odds ratio: 0.68; 95% CI: 0.60, 0.78; ≥800 compared with <250 μg folate/d). The current use of multivitamins for >15 y, but not a shorter duration of use, was associated with lower risk of colorectal cancer; and a shorter duration of use was related to lower risk of adenoma. We did not observe an adverse effect of total folate or synthetic folic acid on risk of colorectal cancer or adenoma even during the folic acid fortification era.

CONCLUSION

Folate intake is inversely associated with risk of colorectal cancer only during early preadenoma stages.

Primary prevention of colorectal cancer

Colorectal cancer has been strongly associated with a Western lifestyle. In the past several decades, much has been learned about the dietary, lifestyle, and medication risk factors for this malignancy. Although there is controversy about the role of specific nutritional factors, consideration of dietary pattern as a whole appears useful for formulating recommendations. For example, several studies have shown that high intake of red and processed meats, highly refined grains and starches, and sugars is related to increased risk of colorectal cancer. Replacing these factors with poultry, fish, and plant sources as the primary source of protein; unsaturated fats as the primary source of fat; and unrefined grains, legumes and fruits as the primary source of carbohydrates is likely to lower risk of colorectal cancer. Although a role for supplements, including vitamin D, folate, and vitamin B6, remains uncertain, calcium supplementation is likely to be at least modestly beneficial. With respect to lifestyle, compelling evidence indicates that avoidance of smoking and heavy alcohol use, prevention of weight gain, and maintenance of a reasonable level of physical activity are associated with markedly lower risks of colorectal cancer. Medications such as aspirin and nonsteroidal anti-inflammatory drugs and postmenopausal hormones for women are associated with substantial reductions in colorectal cancer risk, though their utility is affected by associated risks. Taken together, modifications in diet and lifestyle should substantially reduce the risk of colorectal cancer and could complement screening in reducing colorectal cancer incidence.

Dietary fatty acids and recurrence of colorectal adenomas in a European intervention trial

Epidemiological studies have provided inconsistent data about the role of dietary fatty acids in colorectal cancer, and few studies have addressed their role in colorectal adenoma. The aim of the study was to assess the risk of overall adenoma recurrence associated with dietary consumption of total fat, subtypes of fat, and specific fatty acids (oleic acid, linoleic acid, alpha-linolenic acid). The study sample was composed of 523 patients with confirmed adenomas at the index colonoscopy, 35 to 75 yr old, who completed the European fiber-calcium intervention trial and had an initial dietary assessment using a qualitative and quantitative food questionnaire. The overall 3-yr recurrence rate was 22.6% (118 out of 523 patients). There were no significant associations between overall adenoma recurrence and either total fat, subtypes of fat, or specific fatty acids. However, polyunsaturated fatty acids and linoleic acid were both moderately but significantly associated with distal and multiple recurrence. No significant associations were observed with recurrence of proximal or advanced adenomas. Our findings do not support the hypothesis of strong associations between dietary fatty acids and recurrence of colorectal adenomas. The hypothesis of a differential role of specific fatty acids according to colorectal subsites deserves further investigation.

Fruit and vegetable intakes are associated with lower risk of colorectal adenomas

Many phytochemicals in fruits and vegetables have been shown to have cancer-inhibitory effects in animal studies. These effects on cancer, however, have not been clearly demonstrated in human studies. This study investigated the association between fruit and vegetable intakes and the risk of adenomatous polyps. Participants were part of the Tennessee Colorectal Polyp Study. Eligible participants aged 40-75 y were recruited from patients undergoing colonoscopy at 2 medical centers in Nashville, Tennessee from 2003 to 2005. Cases had at least one adenoma and controls were polyp free. Dietary intake was assessed using a self-administered FFQ. Associations between dietary intakes and adenoma risk were evaluated using unconditional logistic regression with restricted cubic function spline. In multivariate analyses of 764 cases and 1517 controls, increased intakes of total fruits, berries, fruit juice, and green leafy vegetables were associated with reduced adenoma risk. The odds ratio for upper tertile intake compared with lower was 0.66 (95% CI = 0.51-0.86) for total fruits, 0.64 (95% CI = 0.47-0.87) for berries, 0.72 (95% CI = 0.56-0.92) for fruit juice, and 0.74 (95% CI = 0.58-0.96) for green vegetables. This study provides additional evidence that high total fruit intake and certain fruit and vegetable intakes may be associated with a reduced risk of colorectal adenomas.

Vitamins B2, B6, and B12 and risk of new colorectal adenomas in a randomized trial of aspirin use and folic acid supplementation

BACKGROUND

Folate, other vitamin B cofactors, and genes involved in folate-mediated one-carbon metabolism all may play important roles in colorectal neoplasia. In this study, we examined the associations between dietary and circulating plasma levels of vitamins B(2), B(6), and B(12) and risk colorectal adenomas.

METHODS

The Aspirin/Folate Polyp Prevention Study is a randomized clinical trial of folic acid supplementation and incidence of new colorectal adenomas in individuals with a history of adenomas (n = 1,084). Diet and supplement use were ascertained through a food frequency questionnaire administered at baseline. Blood collected at baseline was used to determine plasma B-vitamin levels. We used generalized linear regression to estimate risk ratios (RR) and 95% confidence intervals (95% CI) as measures of association.

RESULTS

We found a borderline significant inverse association with plasma B(6) [pyridoxal 5'-phosphate (PLP)] and adenoma risk (adjusted RR Q4 versus Q1, 0.78; 95% CI, 0.61-1.00; P(trend) = 0.08). This association was not modified by folic acid supplementation or plasma folate. However, the protective association of PLP with adenoma risk was observed only among subjects who did not drink alcohol (P(interaction) = 0.03). Plasma B(2) (riboflavin) was inversely associated with risk of advanced lesions (adjusted RR Q4 versus Q1, 0.51; 95% CI, 0.26-0.99; P(trend) = 0.12). No significant associations were observed between adenoma risk and plasma vitamin B(12) or dietary intake of vitamin B(2) and B(6). When we examined specific gene-B-vitamin interactions, we observed a possible interaction between methylenetetrahydrofolate reductase -C677T and plasma B(2) on risk of all adenomas.

CONCLUSION

Our results suggest that high levels of PLP and B(2) may protect against colorectal adenomas.

Physical activity before and after diagnosis of colorectal cancer: disease risk, clinical outcomes, response pathways and biomarkers

Physical inactivity may be responsible for 13-14% of colon cancer, an attributable risk greater than family history. Epidemiological evidence shows an association between occupational and recreational physical activity and colon cancer, but has not established whether physical activity is protective against low-risk or more advanced adenomas. The evidence is inconclusive as to whether physical activity protects against rectal cancer and is conflicting with respect to whether physical activity has equal effects on male and female risk of colorectal cancer. The effect of exercise 'interventions' on the risk of colorectal cancer is currently not known. Also, although inferences can be made from epidemiological studies, no optimal exercise regimen can be confidently prescribed for protection against colorectal cancer. There is little available evidence for the benefits of physical activity before diagnosis of colorectal cancer for disease-specific survival and prognosis, and the clinical effects of an exercise intervention after diagnosis have not been investigated. There is some evidence that improvements in cardiorespiratory fitness reduce adverse effects from cancer treatment when physical activity is undertaken following diagnosis of colorectal cancer. Markers/mechanisms by which physical activity may protect against colorectal cancer and/or improve disease prognosis include gastrointestinal transit-time, chronic inflammation, immune function, insulin levels, insulin-like growth factors, genetics and obesity. Research evidence is, however, limited as to whether these markers are beneficially affected by physical activity, either before or after diagnosis of colorectal cancer.

Fruit and vegetable intake and prevalence of colorectal adenoma in a cancer screening trial

BACKGROUND

Research on the association between fruit and vegetable intake and risk of colorectal adenoma is inconclusive.

OBJECTIVE

We studied whether intake of fruit, vegetables, or their subgroups is associated with a lower risk of prevalent colorectal adenoma.

DESIGN

In men and women (aged 55-74 y) who were screened for colorectal cancer in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO) (1993-2001), we compared 3,057 cases with at least one prevalent histologically verified adenoma of the distal large bowel with 29,413 control subjects. Using a food-frequency questionnaire, we quantified intake of fruit and vegetables in the 12 mo before screening as energy-adjusted pyramid servings/d (ps/d). Adjusted odds ratios (ORs) and 95% CIs were estimated by logistic regression.

RESULTS

Risk of distal adenoma was significantly lower among subjects in high (approximately 5.7 ps/d) versus low (approximately 1.2 ps/d) quintiles of total fruit intake (OR: 0.75; 95% CI: 0.66, 0.86, P for trend <0.001), which was not completely explained by dietary folate or fiber intake. Inverse associations between adenoma and total fruit intake were observed regardless of adenoma histopathology and multiplicity. However, the protective effect was seen only for colon and not rectal adenoma. Total vegetable intake was not significantly associated with reduced risk of adenoma. ORs for colorectal adenoma among persons with high versus low intakes of deep-yellow vegetables, dark-green vegetables, and onions and garlic were significantly related to lower risk of adenoma, although the P for trend for dark-green vegetables was not significant.

CONCLUSION

Diets rich in fruit and deep-yellow vegetables, dark-green vegetables, and onions and garlic are modestly associated with reduced risk of colorectal adenoma, a precursor of colorectal cancer.

Calcium, dietary, and lifestyle factors in the prevention of colorectal adenomas

BACKGROUND

Many studies have suggested a role for calcium in reducing the risk of colorectal adenomas and cancer but its effectiveness may be dependent on interactions with other dietary and/or lifestyle factors. We examined the association between calcium and prevalence of adenomas and assessed whether the association was stronger in biologically plausible subgroups.

METHODS

Cross-sectional data from 222 cases and 479 adenoma-free controls who underwent colonoscopies and completed food frequency and lifestyle questionnaires were used in the analyses. Multivariable logistic regression was used to estimate the association between calcium and prevalence of adenomas. Stratified analyses and the likelihood ratio test were used to examine effect modification by various demographic, lifestyle, and behavioral factors.

RESULTS

Overall, little association was observed comparing total calcium intake of > or = 900 mg/day to < 500 mg/day (adjusted odds ratio [OR] = 0.85, 95% confidence interval [CI]: 0.53-1.37). However, stronger associations were observed in patients with lower fat intake and in those who regularly (> or = 15 times/month) took nonsteroidal antiinflammatory drugs (NSAIDs). Specifically, total calcium intake of > or = 900 mg/day was associated with a lower prevalence of adenomas among patients with lower fat intake (OR = 0.47, 95% CI: 0.25-0.91) but not among those with higher fat intake (OR = 1.20, 95% CI: 0.61-2.35; P-value for interaction = .01). For NSAIDs, the associations were OR = 0.37 (95% CI: 0.16-0.86) for regular NSAID users and OR = 1.27 (95% CI: 0.73-2.22) with infrequent or nonuse of NSAIDs, respectively (P = .06).

CONCLUSIONS

The data suggest that a lower-fat diet and regular NSAID use may enhance calcium's effectiveness as a colorectal cancer preventive agent.

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.

High dry bean intake and reduced risk of advanced colorectal adenoma recurrence among participants in the polyp prevention trial

Adequate fruit and vegetable intake was suggested to protect against colorectal cancer and colorectal adenomas; however, several recent prospective studies reported no association. We examined the association between fruits and vegetables and adenomatous polyp recurrence in the Polyp Prevention Trial (PPT). The PPT was a low-fat, high-fiber, high-fruit, and vegetable dietary intervention trial of adenoma recurrence, in which there were no differences in the rate of adenoma recurrence in participants in the intervention and control arms of the trial. In this analysis of the entire PPT trial-based cohort, multiple logistic regression analysis was used to estimate the odds ratio (OR) of advanced and nonadvanced adenoma recurrence within quartiles of baseline and change (baseline minus the mean over 3 y) in fruit and vegetable intake, after adjustment for age, total energyy intake, use of nonsteroidal anti-inflammatory drugs, BMI, and gender. There were no significant associations between nonadvanced adenoma recurrence and overall change in fruit and vegetable consumption; however, those in the highest quartile of change in dry bean intake (greatest increase) compared with those in the lowest had a significantly reduced OR for advanced adenoma recurrence (OR = 0.35; 95% CI, 0.18-0.69; P for trend = 0.001). The median in the highest quartile of change in dry bean intake was 370% higher than the baseline intake. The PPT trial-based cohort provides evidence that dry beans may be inversely associated with advanced adenoma recurrence.

Fruit and vegetable consumption and colorectal adenomas in the Nurses' Health Study

Consumption of fruits and vegetables may confer protection from colorectal adenomas, but the limited observational and interventional evidence is inconclusive. We examined the association between fruit and vegetable consumption and the prevalence and incidence of adenomas of the distal colon and rectum in the Nurses' Health Study (NHS). We used data from 34,467 women in the NHS who had undergone colonoscopy or sigmoidoscopy during follow-up between 1980 and 1998. Consumption of fruits and vegetables was assessed in 1980, 1984, 1986, 1990, and 1994 using a semiquantitative food frequency questionnaire; 1,720 prevalent cases of adenoma of the distal colon and rectum were diagnosed between 1980 and 1998. Frequent consumption of fruit was inversely related to the risk of being diagnosed with polyps, whereas little association was found for vegetable consumption. Women who reported consuming five or more servings of fruit a day had an odds ratio (OR) of 0.60 [95% confidence interval (95% CI), 0.44-0.81] for developing colorectal adenomas compared with women who consumed only one or fewer servings of fruit per day, after adjustment for relevant covariates (P(trend) = 0.001). The respective OR for vegetable consumption was 0.82 (95% CI, 0.65-1.05; P(trend) = 0.1). Women who consumed four or more servings of legumes per week had a lower incidence of colorectal adenomas than women who reported consuming one serving per week or less (OR, 0.67; 95% CI, 0.51-0.90; P(trend) = 0.005). Frequent consumption of fruit may reduce the risk of colorectal adenomas.

The association of physical activity and body mass index with the risk of large bowel polyps

PURPOSE AND METHOD

Several studies have suggested that physical inactivity and obesity increase the risk for colorectal neoplasia. In this study, we investigated the association of physical activity and body mass index (BMI) with the risk of different types of large bowel polyps. We did an observational analysis nested within a randomized double-blind placebo-controlled chemoprevention trial among patients with one or more recently resected histologically confirmed colorectal adenoma. Nine hundred thirty patients were randomized to calcium (1,200 mg/d, as carbonate) or placebo. Follow-up colonoscopies were conducted approximately 1 and 4 years after the qualifying examination. At study entry, we obtained each subject's current body weight and height, which we used to calculate BMI. After the second study colonoscopy, we asked subjects questions about their leisure time physical activity. Seven hundred eighty-seven subjects completed at least part of the physical activity questionnaire.

RESULTS

We found no association between measures of physical activity or BMI and tubular adenomas or hyperplastic polyps. However, among men, there were strong inverse associations observed between physical activity and advanced neoplastic polyps. Compared with men whose total daily energy expenditure was in the lowest tertile, those in the highest tertile had a risk ratio of 0.35 (95% confidence interval, 17-0.72); there was no similar reduction observed among women (risk ratio, 1.21; 95% confidence interval, 0.36-4.03; P for interaction = 0.04).

DATA INTERPRETATIONS

We found a significant inverse relationship between several measures of physical activity and risk of advanced colorectal neoplasms, particularly among men. No associations were found between BMI and hyperplastic polyps, tubular adenomas, or advanced neoplastic polyps.

Iron status and risk of cancers in the SU.VI.MAX cohort

The aim of the present study was to evaluate the relation between iron status and cancer in a population of middle-aged adults living in France where iron supplementation and iron-fortified foods are rarely used. The SU.VI.MAX study is a randomized, double-blind, placebo-controlled primary prevention trial evaluating the effect of antioxidant supplementation on chronic diseases in women aged 35-60 and men aged 45-60 y. At baseline, concentrations of hemoglobin, serum transferrin and serum ferritin were measured in 10,197 subjects. Data on dietary intake were estimated from six 24-h dietary records completed during the first 2 study years and available for 5287 subjects. All cancer cases that occurred during the 7.5-y follow-up were validated. In men, baseline serum transferrin and serum ferritin concentrations did not differ between subjects with cancers (n = 467) and those without. In women, serum ferritin was higher (P < 0.0001) and serum transferrin tended to be lower (P < 0.08) in cancer cases. Iron status was not related to cancer risk in men, but women with serum ferritin concentrations > 160 microg/L had an increased risk of cancer (odds ratio = 1.88, 95% CI: 1.05,3.35). No relation was found between dietary iron intake and risk of all cancer sites combined for either men or women. Our results suggest that iron status is not a predictor of cancer risk in men, whereas a serum ferritin concentration > 160 microg/L may be associated with an increase in cancer risk in women.

Dietary intake of folate and riboflavin, MTHFR C677T genotype, and colorectal adenoma risk: a Dutch case-control study

We investigated the associations between dietary intake of folate and vitamin B2, MTHFR C677T genotype, and colorectal adenomas in a Dutch case-control study. Data of cases with at least one histologically confirmed colorectal adenoma (n = 768) and controls with no history of any type of colorectal polyp (n = 709) were included. Dietary intake was assessed using a food-frequency questionnaire. Multivariable models included age and, if appropriate, dietary folate and calcium intake. The adjusted odds ratio (OR) and 95% confidence interval (CI) for the highest compared with the lowest sex-specific tertile of intake were 1.32 (95% CI, 1.01-1.73) for folate and 0.51 (95% CI, 0.36-0.73) for vitamin B2. Folate seemed to be a risk factor, especially when vitamin B2 intake was low; vitamin B2 was inversely associated with adenomas, especially with relatively high folate intake. No association was observed between MTHFR C677T genotype and colorectal adenomas. The inverse association between vitamin B2 intake and colorectal adenoma risk seemed to be more pronounced among those with the MTHFR TT genotype. We conclude that this study does not provide evidence for a decreased colorectal adenoma risk for subjects with high dietary intake of folate. It suggests, however, an inverse association between vitamin B2 and colorectal adenomas, which may be more relevant for those with the MTHFR TT genotype.

Folate and its preventive potential in colorectal carcinogenesis

Based on a 15-year old hypothesis, it is believed that an adequate ingestion of folate vitamins decreases, whereas a nutritional depletion of folate increases the risk of colorectal cancer. The present article reviews the efforts to provide biochemical and epidemiological evidence for folate as a chemopreventive agent against colorectal carcinogenesis. BIOLOGICAL EVIDENCE: Tetrahydrofolates govern the intracellular one-carbon metabolism and account for proper DNA biosynthesis and macromolecular modification. Numerous experimental studies traced different molecular pathways and tried to link folate depletion with DNA instability and/or mutagenesis. However, none of the proposed underlying molecular mechanisms appear clearly defined. EPIDEMIOLOGICAL EVIDENCE: Numerous case-control and prospective studies have been conducted on folate and colorectal cancer, which all together miss a clinical bottom line. The recommendation of folate intake to prevent colorectal cancer is therefore not evidence-based.

Hemochromatosis Gene Mutations, Body Iron Stores, Dietary Iron, and Risk of Colorectal Adenoma in Women

BACKGROUND

Some experimental evidence suggests that iron may play a role in colorectal carcinogenesis, but human data for this role have been conflicting, possibly because of problems related to study design or measurement of iron exposure. We assessed dietary iron intake and genetic and biochemical markers of iron status in a prospective, nested case-control study of women enrolled in the Nurses' Health Study.

METHODS

Among 32 826 women who provided a blood specimen, we identified 527 women with colorectal adenoma and 527 matched control subjects who underwent endoscopy but were not diagnosed with adenoma after blood collection. We assessed iron intake, mutations in the HFE gene that are associated with hereditary hemochromatosis (i.e., H63D and C282Y), and plasma biochemical measures of total body iron, including transferrin saturation and the ratio of the concentrations of transferrin receptors to ferritin. Logistic regression models were used to estimate relative risks (RR) and 95% confidence intervals (CI). All statistical tests were two-sided.

RESULTS

Women with any HFE gene mutation had higher total body iron stores, as reflected by higher transferrin saturations (P < .001) and lower levels of the ratio of transferrin receptors to ferritin (P = .02), than women with no HFE gene mutation. However, HFE gene mutations were not associated with risk of adenoma (multivariable RR = 1.08, 95% CI = 0.83 to 1.39; P = .58). Moreover, comparison of extreme categories showed no associations between adenoma and the extent of transferrin saturation (multivariable RR = 0.96, 95% CI = 0.63 to 1.47; Ptrend = .66), the ratio of transferrin receptors to ferritin (multivariable RR = 0.98, 95% CI, 0.60 to 1.60; Ptrend = .99), or dietary iron intake (multivariable RR = 1.04, 95% CI = 0.68 to 1.57; Ptrend = .94).

CONCLUSIONS

Although our study used several distinct measures of iron status (i.e., genetic mutations, biochemical markers, and dietary intake) and a nested case-control design, we did not observe a role for iron in the pathogenesis of colorectal neoplasia in women.

Vitamin B6 intake, alcohol consumption, and colorectal cancer: a longitudinal population-based cohort of women

BACKGROUND & AIMS

Vitamin B6 has a crucial role in 1-carbon metabolism, which involves DNA synthesis and DNA methylation. Aberrations in these processes have been implicated in colorectal carcinogenesis. We examined the association between long-term dietary vitamin B6 intake and risk of colorectal cancer and whether this association is modified by consumption of alcohol, which may disrupt 1-carbon metabolism.

METHODS

Our study population comprised 61,433 women in the population-based Swedish Mammography Cohort. The women were aged 40 to 76 years, had no history of cancer, and completed a food-frequency questionnaire at baseline in 1987-1990. Dietary information was updated in 1997. During a mean follow-up of 14.8 years, 805 incident colorectal cancer cases were diagnosed.

RESULTS

After controlling for age and other potential confounders, long-term intake of dietary vitamin B6 was significantly inversely associated with risk of colorectal cancer (P value for trend = .002). Compared with women in the lowest quintile of vitamin B6 intake, those in the highest quintile had a 34% lower risk (multivariate rate ratio, 0.66; 95% confidence interval, 0.50-0.86). The association was most pronounced among women with moderate to high alcohol consumption. The multivariate rate ratio of colorectal cancer comparing extreme quintiles of vitamin B6 intake was 0.28 (95% confidence interval, 0.13-0.59) among women who consumed > or = 30 g/wk of alcohol (approximately equivalent to 2 drinks per week).

CONCLUSIONS

Findings of this study suggest that vitamin B6 may play a role in the prevention of colorectal cancer, particularly among women who drink alcohol.

Influence of folate status on genomic DNA methylation in colonic mucosa of subjects without colorectal adenoma or cancer

DNA hypomethylation may increase the risk of colorectal cancer. The main aim of this study was to assess the influence of folate status (serum and erythrocyte folate and plasma homocysteine concentrations) on DNA methylation. Methylenetetrahydrofolate reductase (MTHFR 677C --> T and 1298A --> C), methionine synthase (MS 2756A --> G) and cystathionine synthase (CBS 844ins68) polymorphisms were measured to account for potential confounding effects on folate status and DNA methylation. A total of 68 subjects (33 men and 35 women, 36-78 years) free from colorectal polyps or cancer were recruited in a cross-sectional study. Tissue biopsies were obtained at colonoscopy for the determination of DNA methylation in colonic mucosa using an in vitro radiolabelled methyl acceptance assay. Serum and erythrocyte folate were inversely correlated with plasma homocysteine (r=-0.573, P<0.001 and r=-0.307, P=0.01 respectively) and DNA hypomethylation in colonic mucosa (r=-0.311, P=0.01 and r=-0.356, P=0.03). After adjusting for gender, age, body mass index, smoking and genotype, there were weak negative associations between serum and erythrocyte folate and colonic DNA hypomethylation (P=0.07 and P=0.08, respectively).

Colorectal cancer and the relationship between genes and the environment

Colorectal cancer (CRC) is a significant cause of morbidity and mortality in developed countries, with both genetic and environmental factors contributing to the etiology and progression of the disease. Several risk factors have been identified, including positive family history, red meat intake, smoking, and alcohol intake. Protective factors include vegetables, calcium, hormone replacement therapy, folate, nonsteroidal anti-inflammatory drugs, and physical activity. The interaction between these environmental factors, in particular diet and genes, is an area of growing interest. Currently, oncogenes, tumor suppressor genes, and mismatch repair genes are believed to play an essential role in colorectal carcinogenesis. When considering the genetics of CRC, only 10% of cases are inherited and only 2-6% can be ascribed to the highly penetrant genes, such as APC, hMLH and hMSH2. Lower penetrance genes combined with a Western-style diet contribute to the majority of sporadic CRCs. The purpose of this article is to give a brief overview of the epidemiologic studies that have been conducted and present the major findings. Here, we examine the molecular events in CRC, with particular focus on the interaction between genes and environment, and review the most current research in this area.

Dietary Marine n-3 Fatty Acids in Relation to Risk of Distal Colorectal Adenoma in Women

Epidemiologic studies of dietary marine n-3 fatty acids and risk of colorectal cancer have been inconsistent, and their relation to risk of colorectal adenoma has not been evaluated in detail. We examined dietary marine n-3 fatty acids and the ratio of marine n-3 to total n-6 fatty acids (n-3/n-6 ratio) in relation to risk of adenoma of the distal colon or rectum among 34,451 U.S. women who were initially free of colorectal cancer or polyps, who completed a semiquantitative food frequency questionnaire in 1980, and who underwent endoscopy from 1980 to 1998. We documented 1,719 distal colorectal adenoma cases (705 large adenomas, 897 small adenomas, 1,280 distal colon adenomas, and 505 rectal adenomas) during 18 years of follow-up. Neither dietary marine n-3 fatty acids nor n-3/n-6 ratio were associated with risk of total distal colorectal adenoma after adjustment for age and established risk factors [multivariable relative risk (RR) for extreme quintiles of dietary marine n-3 fatty acids = 1.04; 95% confidence interval (95% CI), 0.84-1.27, P(trend) = 0.66; RR for extreme quintiles of n-3/n-6 ratio = 1.02; 95% CI, 0.83-1.25; P(trend) = 0.86]. Similarly, no significant associations were observed separately for distal colon or rectal adenoma. However, higher intake of dietary marine n-3 fatty acids was nonsignificantly but suggestively inversely associated with large adenoma (RR, 0.74; 95% CI, 0.54-1.01; P(trend) = 0.16) but directly associated with small adenoma (RR, 1.36; 95% CI, 1.02-1.81; P(trend) = 0.09). Our findings do not support the hypothesis that a higher intake of marine n-3 fatty acids or a higher n-3/n-6 ratio reduces the risk of distal colorectal adenoma but are suggestive that higher intake may reduce the progression of small adenomas to large adenomas.

The association of calcium and vitamin D with risk of colorectal adenomas

The Polyp Prevention Trial (PPT) was a multicenter randomized clinical trial designed to determine the effects of a high-fiber, high-fruit and vegetable, low-fat diet on the recurrence of adenomatous polyps in the large bowel. Detailed dietary intake and supplement use data were collected at baseline and at each of 4 annual study visits. Adenoma recurrence was ascertained by complete colonoscopy at baseline and after 1 and 4 y. Recurrence was found in 754 of the 1905 trial participants. We evaluated the association between calcium and vitamin D intake and adenomatous polyp recurrence after adjusting for intervention group, age, gender, nonsteroidal anti-inflammatory drug use, total energy intake, and the interaction of gender and intervention group. Vitamin D models were also adjusted for the location of the clinic site. Dietary variables were adjusted for total energy intake via the residual method. There were no overall significant associations between adenoma recurrence and dietary calcium intake [odds ratio (OR) for the 5th compared with the lowest quintile = 0.91; 95% CI = 0.67-1.23; P-trend = 0.68], total calcium intake (OR = 0.86; 95% CI = 0.62-1.18; P-trend = 0.20), or dietary vitamin D intake (OR = 0.93; 95% CI = 0.69-1.25; P-trend = 0.43) averaged over follow-up. Total vitamin D intake was weakly inversely associated with adenoma recurrence (OR = 0.84; 95% CI = 0.62-1.13; P-trend = 0.03). Supplemental calcium and vitamin D use during follow-up also were inversely associated with adenoma recurrence (OR for any compared with no use = 0.82; 95% CI = 0.68-0.99; and OR = 0.82; 95% CI = 0.68-0.99; for calcium and vitamin D, respectively). Slightly stronger associations were noted for the prevention of multiple recurrences. Our analyses did not suggest a significant effect modification between total calcium and total vitamin D intake (P = 0.14) on risk for adenoma recurrence. This trial cohort provides some evidence that calcium and vitamin D may be inversely associated with adenoma recurrence.

Hemochromatosis Gene Mutations and Distal Adenomatous Colorectal Polyps

Iron has been suggested to be a risk factor for colorectal neoplasia. Some individuals who are heterozygous for mutations in the hemochromatosis gene (HFE) have higher than average serologic measures of iron. We therefore investigated whether heterozygosity for HFE mutations was related to risk of advanced distal adenoma and whether the relationship was affected by dietary iron intake. In the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, 679 persons with advanced distal adenoma and 697 control persons were genotyped for the two major HFE mutations (C282Y and H63D), one HFE polymorphism (IVS2+4), and one polymorphism (G142S) in the transferrin receptor gene (TFRC). HFE haplotypes were also created to examine the effect of haplotype on risk. Food frequency questionnaire data were used to estimate daily iron intake. There was no relationship between any HFE genotype or haplotype and advanced adenoma. Stratification of HFE genotype by TFRC genotype did not change the results. In addition, there was no relationship between dietary iron intake and risk of adenoma or between HFE genotype and risk of adenoma, stratified by iron intake. These results do not support a relationship between HFE heterozygosity and risk of advanced distal adenoma.

Interactions between folate and aging for carcinogenesis

Inadequate folate intake and aging are each strongly implicated as important risk factors for certain cancers. Since both folate depletion and aging are strongly associated with hyperhomocysteinemia, genomic DNA hypomethylation, and increased uracil misincorporation into DNA, it appears that each of them enhances carcinogenesis by inducing a derangement of one-carbon metabolism that supplies one-carbons to biological methylation reactions and nucleotide synthesis. Recent studies have demonstrated that inadequate dietary folate and aging may interact and synergistically disturb the normal homeostasis of one-carbon metabolism, thereby provoking subsequent biochemical and molecular aberrations, including alterations in critical gene expression related to carcinogenesis. These studies have further indicated that modest folate supplementation may reverse or partially ameliorate those adverse effects induced by folate depletion and aging.

Serum fructosamine and colorectal adenomas

The relationship of glucose in the blood with colorectal adenoma or cancer is not clear. Fructosamine, equivalent to total serum glycated proteins, is a marker of blood glucose levels in the previous 3 weeks. We evaluated in a case-control study the association between fructosamine and colorectal adenoma, a precursor of colorectal cancer. Cases were subjects with the first occurrence of one or more histologically confirmed colorectal adenomatous polyps removed after a complete colonoscopy (153 cases), and controls were subjects with normal colonoscopy performed in the same endoscopy units during the same period (84 controls). Serum fructosamine was measured by a colorimetric method. Unconditional multiple logistic regression was used for statistical analysis. We found that in non-diabetic subjects the risk of colorectal adenoma increased with the level of fructosamine, and the odds ratio of colorectal adenoma in subjects with fructosamine levels higher than the median (270 microg/100 ml), in comparison with subjects with fructosamine lower than the median, was 2.3 (95% CI: 1.1-4.8). The risk of colorectal adenoma increased also with increasing levels of serum triglycerides and cholesterol, and decreased with increasing levels of fasting serum insulin. The results of this study show that the risk of colorectal adenoma increases with the level of fructosamine, an indicator of the level of glucose in the blood more sensitive to foods with a high glycemic index.

Carotenoids, vitamin A and risk of adenomatous polyp recurrence in the polyp prevention trial

One trial reported beta-carotene supplementation was protective of adenomatous polyp recurrence in nonsmokers. We now examine the relation of serum and dietary carotenoids and vitamin A to adenomatous polyp recurrence in a subcohort of 834 participants in a low fat, high fiber, high fruit and vegetable dietary intervention, the Polyp Prevention Trial. Multivariate odds ratio (OR) and 95% confidence intervals (CI) of polyp recurrence were obtained using baseline or the average (first 3 years of the trial) carotenoid and vitamin A values after adjustment for covariates. Compared to the lowest quartile of baseline alpha-carotene concentrations, the OR of multiple polyp recurrence for the highest quartile was 0.55 (95% CI = 0.30-0.99) and the OR of right-sided recurrence was 0.60 (95% CI = 0.37-0.95). Baseline dietary intakes of alpha-carotene and vitamin A from food with/without supplements were inversely associated with any recurrence (p for linear trend = 0.03-alpha-carotene; p = 0.004 and p = 0.007 -intakes of vitamin A). Compared to the lowest quartile of averaged beta-carotene concentrations, the OR of multiple adenomas for the highest quartile was 0.40 (95% CI = 0.22-0.75) with an inverse trend (p = 0.02). The risk was inversely related to averaged: alpha-carotene concentrations and right-sided polyps; alpha-carotene intake and recurrence of any, multiple and right-sided polyps; beta-carotene intake and multiple adenoma recurrence; vitamin A from food (with supplements) and each adverse endpoint. Thus, alpha-carotene and vitamin A may protect against recurrence in nonsmokers and nondrinkers or be indicative of compliance or another healthy lifestyle factor that reduces risk.

Alcohol, one-carbon metabolism, and colorectal cancer: recent insights from molecular studies

A growing body of evidence implicates alcohol intake as a risk factor for colorectal cancer. Until recently, most of the data were based on epidemiologic data that examined alcohol intake in relation to risk of colorectal neoplasia, but the evidence has now been broadened by recent molecular studies on mechanisms. In particular, a number of observations strongly support a role for alcohol acting through disruptions in one-carbon metabolism. Excessive alcohol intake is a fairly consistent risk factor for colorectal neoplasia in most studies, and studies show much higher risks of colorectal neoplasia in those with high alcohol and low folate than with high alcohol or low folate individually. Interactions between high alcohol-low folate and the MTHFR677TT genotype with risk of colorectal neoplasia suggest that alcohol is acting through its effects on one-carbon metabolism because the combination of high alcohol-low folate and the MTHFR677TT genotype are related to markedly elevated serum levels of homocysteine and to DNA hypomethylation. In addition, in Japanese studies, consumers of alcohol possessing the ALDH2*2 allele, who have very elevated levels of acetaldehyde, are at high risk for colorectal cancer. The relatively high prevalence of the ALDH2*2 allele may thus account for the stronger association between alcohol and colorectal neoplasia that is frequently observed in studies in Japanese populations. Further research integrating studies with more detailed data on alcohol intake levels and patterns, folate and other related nutrient status, and relevant genotypes may help clarify unresolved questions regarding the health consequences of moderate to high alcohol drinking.

Glycemic Index, Glycemic Load, and Carbohydrate Intake in Relation to Risk of Distal Colorectal Adenoma in Women

Case-control studies and a cohort study have shown inconsistent associations between a high glycemic index or a high glycemic load and risk of colorectal cancer. These dietary variables have not been examined in relation to risk of colorectal adenoma. We thus examined the associations between dietary glycemic index, glycemic load, and carbohydrate intake with risk of adenoma of the distal colon or rectum among 34,428 US women who were initially free of cancer or polyps, who completed a semi-quantitative food-frequency questionnaire in 1980, and who underwent endoscopy from 1980 through 1998. 1,715 adenoma cases (704 large adenomas, 894 small adenomas, 1,277 distal colon adenomas, and 504 rectal adenomas) were documented during 18 years of follow-up. Dietary glycemic index, glycemic load, and carbohydrate intake were not related to risk of total colorectal adenoma after adjustment for age and established risk factors [relative risk (RR) for extreme quintiles of glycemic index = 1.11, 95% confidence interval (CI) 0.94-1.32, P for trend = 0.66; RR for glycemic load = 0.92, 95% CI 0.76-1.11, P for trend = 0.63; RR for carbohydrate intake = 0.90, 95% CI 0.73-1.11, P for trend = 0.64]. In addition, no significant associations were found for large or small adenoma, distal colon or rectal adenoma, or across strata of body mass index. Our findings do not support the hypothesis that a high glycemic index diet, a high glycemic load diet, or high carbohydrate intake overall are associated with risk of colorectal adenoma.

Effect of calcium supplementation on the risk of large bowel polyps

BACKGROUND

Clinical trials have shown that calcium supplementation modestly decreases the risk of colorectal adenomas. However, few studies have examined the effect of calcium on the risk of different types of colorectal lesions or dietary determinants of this effect.

METHODS

Our analysis used patients from the Calcium Polyp Prevention Study, a randomized, double-blind, placebo-controlled chemoprevention trial among patients with a recent colorectal adenoma. Nine hundred thirty patients were randomly assigned to calcium carbonate (1200 mg/day) or placebo. Follow-up colonoscopies were conducted approximately 1 and 4 years after the qualifying examination. We used general estimating equation (GEE) and generalized linear regression analyses to compute risk ratios and 95% confidence intervals (CIs) to assess the effect of calcium treatment versus placebo on the risk of hyperplastic polyps, tubular adenomas, and more advanced lesions. Additionally, we used GEE analyses to compare the calcium treatment effects for various types of polyps with that for tubular adenomas. We also examined the interaction between calcium treatment and baseline intake of dietary calcium, fat, and fiber. All P values were obtained using Wald tests based on the corresponding models. All tests of statistical significance were two-sided.

RESULTS

The calcium risk ratio for hyperplastic polyps was 0.82 (95% CI = 0.67 to 1.00), that for tubular adenomas was 0.89 (95% CI = 0.77 to 1.03), and that for histologically advanced neoplasms was 0.65 (95% CI = 0.46 to 0.93) compared with patients assigned to placebo. There were no statistically significant differences between the risk ratio for tubular adenomas and that for other types of polyps. The effect of calcium supplementation on adenoma risk was most pronounced among individuals with high dietary intakes of calcium and fiber and with low intake of fat, but the interactions were not statistically significant.

CONCLUSION

Our results suggest that calcium supplementation may have a more pronounced antineoplastic effect on advanced colorectal lesions than on other types of polyps.

Exercise and intestinal polyp development in APCMin mice

PURPOSE

Epidemiological evidence suggests that physical activity protects against colon cancer. We previously used a mouse predisposed to intestinal polyps (APCMin) to evaluate this association and found the suggestion of fewer polyps in exercised males but not females. The present study was designed to further explore the potential exercise x sex interaction on polyp development and to begin to look at potential mechanisms.

METHODS

Six-week-old APCMin mice (N = 60 males; 60 females) were randomly assigned to one of two groups by sex: treadmill running at 20 m.min-1, 5% grade, 45 min.d-1, 5 d.wk-1 (EX) or nonrunning controls (CON) (N = 30 per group). EX mice ran in running wheels while in quarantine (weeks 0-3), followed by treadmill running weeks 3-8. Body weights were measured weekly. Urine was collected at 5 wk and fasting blood at 7.5 wk. Body composition was measured, serum was frozen, and polyp number and size were measured at sacrifice.

RESULTS

EX resulted in lower body weights (P < 0.01) and reduced fat mass (P < 0.01). Fasting glucose was lower in EX (P < 0.01), and leptin was lower in EX (P = 0.05) compared with CON. EX did not affect serum insulin-like growth factor-1 or urinary corticosterone. Total polyp number and size were not statistically different between groups; however, there were fewer jejunal polyps in EX (3.6 +/- 0.7, mean +/- SE) versus CON males (5.2 +/- 0.8; P = 0.04) and an even larger difference when only the consistent runners were kept in the analysis (2.7 +/- 0.5 in EX; P = 0.01).

CONCLUSION

Despite favorable changes in body composition, blood glucose, and leptin, 8 wk of running resulted in only minor changes related to polyp development in male but not female APCMin mice.

Folate and colorectal neoplasia: relation between plasma and dietary markers of folate and adenoma recurrence

BACKGROUND

The results of epidemiologic studies indicate that higher intakes or blood concentrations of folate are associated with a lower risk of colorectal neoplasia; however, only one study assessed the role of homocysteine.

OBJECTIVE

We assessed the relation between biochemical and dietary markers of folate status and colorectal adenoma recurrence.

DESIGN

Analyses were conducted in 1014 men and women aged 40-80 y who had undergone removal of all colorectal polyps. Diet and supplement use were ascertained through a food-frequency questionnaire administered at study entry. Blood collected at baseline was used to measure plasma folate and homocysteine concentrations. Unconditional logistic regression was used to assess the odds of recurrence associated with the intakes of folate, methionine, and vitamins B-6 and B-12 and with plasma folate and homocysteine.

RESULTS

Relative to subjects in the highest quartile of plasma homocysteine, those in the lowest quartile had an odds ratio (OR) of adenoma recurrence of 0.69 (95% CI: 0.47, 1.02; P for trend = 0.02) after adjustment for confounding factors. Lower odds of recurrence were shown for higher plasma folate (OR: 0.66; 95% CI: 0.46, 0.97) and higher total intakes (dietary plus supplemental) of folate (OR: 0.61; 0.42, 0.89) and vitamin B-6 (OR: 0.65; 0.45, 0.94). Slightly weaker and nonsignificant associations were shown for dietary folate, methionine, and total vitamin B-12.

CONCLUSIONS

A lower recurrence of colorectal adenomas was shown in subjects with higher intakes and plasma concentrations of folate. Additional markers involved in folate metabolism, including lower homocysteine and higher vitamin B-6 intake, were also associated with lower odds of recurrence.

Heme iron, zinc, alcohol consumption, and colon cancer: Iowa Women's Health Study

We examined associations among colon cancer incidence and dietary intake of heme iron, a possible prooxidant, zinc, a possible antioxidant, and alcohol, a disruptor of iron homeostasis. During 15 years of follow-up, 34 708 postmenopausal women, aged 55-69 years at baseline who completed a food-frequency questionnaire for the Iowa Women's Health Study, were followed for incident colon cancer. After adjusting for each micronutrient, the relative risks for proximal colon cancer increased more than twofold across categories of heme iron intake (P(trend) =.01) and the corresponding relative risks decreased more than 50% across categories for zinc intake (P(trend) =.01). The positive association with heme iron and the inverse association with zinc intake were stronger among women who consumed alcohol than among those who did not. Zinc intake was also associated with a decreased risk of distal colon cancer (P(trend) =.03), regardless of alcohol or heme iron consumption. Our results suggest that intake of dietary heme iron is associated with an increased risk of proximal colon cancer, especially among women who drink, but that intake of dietary zinc is associated with a decreased risk of both proximal and distal colon 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.

Folate, methyl-related nutrients, alcohol, and the MTHFR 677C-->T polymorphism affect cancer risk: intake recommendations

Colorectal cancer and adenoma risk are inversely associated with higher total folate intake. Significant modifiers of cancer risk also include other methyl-related nutrients and alcohol. Adequate folate intake is particularly important for women at higher risk for breast cancer because of moderate alcohol consumption. The methylenetetrahydrofolate reductase (MTHFR) 677C-->T polymorphism is associated with a reduced risk of some forms of cancer. The protective effect of this folate-related polymorphism is dependent on adequate folate status. Cancer risk may be increased in individuals with the homozygous genotype for the MTHFR 677C-->T polymorphism who have low status of methyl-related nutrients including folate. Intake recommendations to potentially reduce cancer risk include substitution of low folate foods with folate-dense fruits and vegetables and in countries where there is no mandatory folic acid fortification, increased consumption of folic acid from available fortified foods or supplements. Adequate dietary intake of vitamin B-6 and methionine can be achieved by consumption of low fat, concentrated food sources of these nutrients. The recommended intake for vitamin B-12 for individuals >/==" BORDER="0">51 y should be provided predominately in crystalline form (e.g., fortified ready-to-eat cereal, supplements). If alcohol is consumed, consumption should be restricted to <15 g/d or <1 drink/d. The negative effects of low intakes of the methyl-related nutrients with high intakes of alcohol are additive, therefore changes in overall dietary patterns to ensure the consumption of a protective high methyl diet are recommended.

Relationship of folate, vitamin B-6, vitamin B-12, and methionine intake to incidence of colorectal cancers

It is hypothesized that diets deficient in folate, methionine, and vitamins B-6 and B-12 cause DNA hypomethylation and, as a result, increase risk of colorectal cancers. Furthermore, it is proposed that alcohol, a methyl group antagonist, increases risk of colorectal cancers among those with low intake of folate. Data from the Iowa Women's Health Study, a population-based cohort of incident cancer, were used to examine the relationship of folate, methionine, and vitamins B-6 and B-12 to occurrence of cancers of the colon (n = 598) and rectum (n = 123) over 13 yr of follow-up. There were no independent associations of folate, methionine, or vitamins B-6 and B-12 derived from a food frequency questionnaire with incidence of colon cancer. Adjusted relative risks (RRs) of rectal cancer were similar across categories of folate, vitamin B-12, and methionine intake, but RRs increased progressively with increasing intake of vitamin B-6 [P (for trend) = 0.03]. RRs suggested that incidence of cancer of the proximal colon was lower among those with 1) high folate and high vitamin B-12 intake [RR = 0.59, 95% confidence interval (CI) = 0.39-0.89] and 2) high folate and high vitamin B-6 intake (RR = 0.65, 95% CI = 0.50-0.84) than among those with the lowest intake of these nutrients. Incidence of cancer of the proximal colon was also somewhat lower among those with high folate and low alcohol intake (RR = 0.44, 95% CI = 0.22-0.89). Findings provide limited support for an association between dietary factors involved in DNA methylation and risk of cancers of the colon and rectum.

Folate status, genomic DNA hypomethylation, and risk of colorectal adenoma and cancer: a case control study

BACKGROUND & AIMS

Low folate intake may increase risk for colorectal cancer by inducing DNA hypomethylation. This study reports the influence of folate status, DNA methylation, and polymorphisms of methylenetetrahydrofolate reductase (MTHFR 677C-->T and 1298A-->C), methionine synthase (MS 2756A-->G), and cystathionine-beta-synthase (CBS 844ins68) on risk for developing colorectal neoplasia.

METHODS

Thirty-five patients with adenoma, 28 patients with cancer, and 76 controls were recruited for a case control study. Recruitment consent rate was 98%. Blood samples were obtained for determination of blood folates, vitamin B(12), homocysteine, DNA methylation, and genotypes. Tissue biopsy samples were obtained at colonoscopy for determination of DNA methylation in colonic mucosa. Folate status was assessed by constructing a score from estimates of dietary intake and serum and erythrocyte folate.

RESULTS

Cancer patients had 26% lower folate status (95% confidence interval [CI]: 6% to 44%, P = 0.01) and 21% lower serum vitamin B(12) concentration (95% CI: -38% to 1%, P = 0.06) compared with controls. [(3)H] methyl incorporation into colonic DNA was 26% higher in patients with adenoma (95% CI: 8% to 56%, P = 0.009) and 30% higher in patients with cancer (95% CI: -3% to 48%, P = 0.08) compared with controls. High folate status was associated with decreased risk for cancer (P = 0.01 for trend). Colonic and leukocyte DNA hypomethylation were associated with increased risk for adenoma (P = 0.02 and P = 0.01 for trend, respectively) and a nonsignificantly increased risk for cancer (P = 0.09 and P = 0.08 for trend, respectively).

CONCLUSIONS

Low folate status and DNA hypomethylation are associated with colorectal neoplasia.