Dietary energy sources and colon cancer risk

Regulatory T Cells in Bioactive Peptides-Induced Oral Tolerance; a Two-Edged Sword Related to the Risk of Chronic Diseases: A Systematic Review

This systematic review assesses the literature regarding beneficial and potential detrimental effects of bioactive peptides (BPs), focusing on evidence of regulatory T cells (T-regs) mediated oral tolerance (OT), collagen hydrolysate (CH) supplementation in osteoarthritis (OA) and the association of T-regs with chronic disease. The systematic search was done for articles published from inception to April 2019 using the PubMed and Scopus databases. About 3081 papers were identified by three different search strategies and screened against inclusion criteria which resulted in the inclusion of 22 articles. From the included articles, 12 papers were related to treatment of different disease in vivo by oral administration of BPs, six articles evaluated the effects of CH supplementation, as a rich source of BPs, on OA pain-relief and four observational studies assessed the association of circulating T-regs and risk of cancer and cardiovascular disease (CVD). The evidence obtained from first search strategy, indicated that oral administration of BPs improve clinical manifestations of animal models of allergy, arthritis, atherosclerosis, ulcerative colitis and allograft rejection by T-regs expansion; while, observational studies showed that although higher levels of circulating T-regs reduced risk of CVD and allergy, but, increased risk of solid cancers.

Mutation analysis of adenomas and carcinomas of the colon: Early and late drivers

Colorectal cancer (CRC) accounts for about 8% of all new cancer cases diagnosed in the US. We used whole exome sequence data from triplet samples (colon carcinoma, colon adenoma, and normal tissue) from 18 individuals to assess gene mutation rates. Of the 2 204 genes that were mutated, APC, TTN, TP53, KRAS, OBSCN, SOX9, PCDH17, SIGLEC10, MYH6, and BRD9 were consistent with genes being an early driver of carcinogenesis, in that they were mutated in multiple adenomas and multiple carcinomas. Fifty-two genes were mutated in ≥12.5% of microsatellite stable (MSS) carcinomas but not in any of the adenomas, in line with the profile of a late driver event involved in tumor progression. Thirty-eight genes were sequenced in a larger independent set of 148 carcinoma/normal tissue pairs to obtain more precise mutation frequencies. Eight of the genes, APC, TP53, ATM, CSMD3, LRP1B, RYR2, BIRC6, and MUC17, contained mutations in >20% of the carcinomas. Interestingly, mutations in four genes in addition to APC that are associated with dysregulation of Wnt signaling, were all classified as early driver events. Most of the genes that are commonly associated with colon cancer, including APC, TP53, and KRAS, were all classified as being early driver genes being mutated in both adenomas and carcinomas. Classifying genes as potential early and late driver events points to candidate genes that may help dissect pathways involved in both tumor initiation and progression.

The association between dietary protein intake and colorectal cancer risk: a meta-analysis

BACKGROUND

Association between dietary protein intake and colorectal cancer risk has not been fully quantified, while the results were controversial. This study aimed to evaluate the role of protein intake in the development of colorectal cancer.

METHODS

PUBMED and EMBASE were searched up to December 2016. Two independent reviewers independently extracted data from eligible studies. Relative risk (RR) with 95% confidence intervals (CI) was pooled using random-effects model to estimate the result. Besides, publication bias and sensitivity analysis were conducted.

RESULTS

Thirteen articles involving 21 studies comprising 8187 cases were included in this report. The pooled RR of colorectal cancer was 1.006 (95% CI = 0.857-1.179) indicating that there is no significant association between dietary protein intake and colorectal cancer risk. Furthermore, the pooled RRs for colon cancer and rectum cancer were 1.135(95% CI = 0.871-1.480) and 0.773(95% CI = 0.538-1.111), respectively, with the highest category of dietary protein intake. The association was not significant either in subgroup analysis of study design, protein type (animal protein or vegetable protein), sex, and or geographic locations.

CONCLUSIONS

The present study indicated that the highest category compared to the lowest category of protein intake had no significant association on colorectal cancer risk. Dose-response analysis was not conducted due to limited information provided. Therefore, more studies with large cases and participants as well as detailed amounts of dietary protein intake are wanted to confirm this result.

Do alcoholic beverages, obesity and other nutritional factors modify the risk of familial colorectal cancer? A systematic review

PURPOSE

Individuals with family history of colorectal cancer are at higher risk of colorectal cancer than the general population. Until now, guidelines for familial colorectal cancer risk have only pointed at early diagnosis efforts via screening tests and surveillance, and payed scarce or no attention to lowering exposure to modifiable risk factors, notably nutritional factors.

METHODS

We conducted a systematic review of epidemiological studies investigating the associations between nutritional factors, family history of colorectal cancer, and colorectal cancer risk. From the 5312 abstracts identified until December 2016, 184 full text articles were examined for eligibility. Finally, 31 articles (21 from case-control studies, 9 from cohort studies and 1 from an intervention study) met inclusion criteria and were analyzed.

RESULTS

Mainly, the combinations of family history of colorectal cancer and higher consumptions of alcoholic beverages, red or processed meat, or overweight/obesity increase the risk of colorectal cancer. Consistently, a strong increase is observed with the combinations of family history of colorectal cancer and unhealthy dietary patterns/lifestyles. Statistically significant interactions between these nutritional factors, family history of colorectal cancer and colorectal cancer risk are reported. Other data are inconclusive and additional prospective studies are needed.

CONCLUSIONS

For the first time, our findings highlight that addressing high consumption of alcoholic beverages, red or processed meat, and overweight/obesity, and more largely the exposure to multiple unhealthy dietary/nutritional behaviors could offer new perspectives of prevention to individuals with family history of colorectal cancer. A better information of these patients and of health professionals on these nutritional modifiable risk factors is recommended.

A meta-analysis between dietary carbohydrate intake and colorectal cancer risk: evidence from 17 observational studies

The association between dietary carbohydrate intake and colorectal cancer (CRC) risk remains controversial. We therefore conducted this meta-analysis to assess the relationship between them. A literature search from the databases of PubMed, Embase, Web of Science and Medline was performed for available articles published in English (up to September 2016). Pooled relative risk (RR) with 95% confidence interval (CI) was calculated to evaluate the association between dietary carbohydrate intake and CRC risk. The random-effect model (REM) was selected as the pooling method. Publication bias was estimated using Egger’s regression asymmetry test and funnel plot. A total of 17 articles involving 14402 CRC patients and 846004 participants were eligible with the inclusion criteria in this meta-analysis. The pooled RR with 95% CI of dietary carbohydrate intake for CRC, colon cancer and rectum cancer risk were 1.08 (95% CI =0.93–1.23, I² =68.3%, P_{heterogeneity}<0.001), 1.09 (95% CI =0.95–1.25, I² =48.3%) and 1.17 (95% CI =0.98–1.39, I² =17.8%) respectively. When we conducted the subgroup analysis by gender, the significant association was found in men’s populations (summary RR =1.23, 95% CI =1.01–1.57), but not in the women’s populations. In the further subgroup analyses for study design and geographic locations, we did not find any association between dietary carbohydrate intake and CRC risk in the subgroup results respectively. No significant publication bias was found either by the Egger’s regression asymmetry test or by the funnel plot. This meta-analysis suggested that higher dietary carbohydrate intake may be an increased factor for CRC risk in men populations. Further studies are wanted to confirm this relationship.

Dietary protein and fat intake in relation to risk of colorectal adenoma in Korean

Consumption of red meat and alcohol are known risk factors for colorectal cancer, but associations for dietary fat remain unclear. We investigated the associations of dietary fat, protein, and energy intake with prevalence of colorectal adenoma.We performed a prospective cross-sectional study on asymptomatic persons who underwent a screening colonoscopy at a single center during a routine health check-up from May to December 2011. Dietary data were obtained via a validated Food Frequency Questionnaire (FFQ), assisted by a registered dietician. We also obtained information on alcohol consumption and smoking status, and measured metabolic syndrome markers including abdominal circumference, blood pressure, fasting glucose, serum triglyceride and high-density lipoprotein cholesterol. We calculated odds ratio (OR) and 95% confidence interval (CI) to evaluate the associations using the polytomous logistic regression models. As a secondary analysis, we also conducted a matched analysis, matched by age and sex (557 cases and 557 non-cases).The study sample included 557 cases (406 males and 151 females) with histopathologically confirmed colorectal adenoma, and 1157 controls (650 males and 507 females). The proportion of advanced adenoma was 28.1% of men and 18.5% of female, respectively. Although vegetable protein intake was inversely associated with the prevalence of colorectal adenoma, further adjustment for potential confounding factors attenuated the association, resulting in no significant associations. There were no significant associations between dietary fat intake and colorectal adenoma in energy-adjusted models. For vegetable protein in women, the OR for the comparison of those in the highest tertile with those in the lowest tertile was 0.47 (95% CI 0.25-0.91, P for trend = 0.07) after adjustment for total energy intake. However, after controlling for metabolic syndrome markers, body mass index, smoking status, alcohol consumption, and family history of colorectal adenoma, which were all significantly high in the colorectal adenoma patients group, the association became attenuated (OR 0.54, 95% CI 0.27-1.11, P for trend = 0.13).In conclusion, we did not observe the significant associations for intakes of total energy, total, animal and vegetable fats, and total, animal and vegetable proteins in relation to colorectal adenoma prevalence.

Reducing mortality from colorectal cancer: screening versus primary prevention

SUMMARY 

Screening reduces mortality from colorectal cancer but, like breast and prostate cancer screening, does not significantly prolong life expectancy. It is cost effective though, as polyp removal prevents cancer development and its associated cost and morbidity. Given the lack of impact of screening on overall life expectancy, prevention of colorectal cancer by lifestyle adjustment, particularly dietary, should still be considered as an alternative strategy. Avoidance of excessive calories and increased fiber intake would probably reduce risk not only for colorectal cancer but also for cardiovascular and cerebrovascular disease and substantially reduce all-cause mortality. We need better knowledge though of how specific dietary components impact on colon cancer risk and for this we probably need better understanding of the role of bacteria.

[Dietary risk factors in relation to colorectal adenoma]

BACKGROUND/AIMS

The role of dietary risk factors in colorectal carcinogenesis remains unclear. We investigated the association between dietary intakes and colorectal adenomas who visited a health promotion center for a routine health check-up colonoscopy.

METHODS

We conducted a retrospective case-control study using data from individuals who had colonoscopy at Seoul National University Hospital Healthcare System Gangnam Center from October 2003 to December 2007. The subjects were 242 patients (162 males and 80 females) with histopathologically confirmed colorectal adenoma, and 464 (272 males and 192 females) controls. Dietary data were obtained via 24 hour dietary recall, assisted by a registered dietitian. The student's t-test and the chi-square test were performed for the statistical comparison of means and proportions among groups. Multivariate analyses using logistic regression were performed to assess the relation between dietary intake and colorectal adenoma.

RESULTS

The total average energy intake of the patients (male: 2,407.5±429.2 kcal, female: 1,901.3±316.9 kcal) was higher than the controls (male: 2,249.6±430.4 kcal, female: 1,752.4±275.0 kcal; p=0.001). High energy intake (male: OR=4.13, 95% CI=1.70-10.05, p=0.002; female: OR=4.00, 95% CI=1.51-10.61, p=0.005) and animal protein intake (male: OR=3.97, 95% CI=1.66-9.49, p=0.002; female: OR=5.76, 95% CI=1.99-16.169, p=0.001) were found to be associated with the risk of colorectal adenoma after adjusting for confounders such as age, BMI, waist circumference, metabolic syndrome and smoking.

CONCLUSIONS

In summary, high energy intake and animal protein were associated with colorectal adenoma.

Colonocyte telomere shortening is greater with dietary red meat than white meat and is attenuated by resistant starch

BACKGROUND & AIMS

Population studies indicate that greater red meat consumption increases colorectal cancer risk while dietary fibre is protective. Previous work in rats showed that diets high in protein, including red meat, increase colonocyte DNA strand breaks and that this effect is attenuated by resistant starches (RS). Telomeres are long hexamer repeats that protect against spontaneous DNA damage which would lead to chromosomal instability. Telomere shortening is associated with greater risk of colorectal cancer. The current study aimed to determine the effects of cooked red and white meat intake on colonocyte telomere length in rats and whether dietary RS modified their effects.

METHODS

After four weeks of feeding cooked beef or chicken at 15, 25 and 35% of diet with or without RS, colonocyte telomere length was measured.

RESULTS

Telomere length decreased in proportion to red meat content of the diet. A similar trend was observed in the white meat group. Colonocyte telomere shortening due to increased dietary meat was attenuated by the inclusion of RS.

CONCLUSION

These data support previous findings of increased colonocyte DNA damage with greater red and white meat intake and also the protective effect of dietary fibre.

Risk factors for colon cancer in Northeastern Thailand: interaction of MTHFR codon 677 and 1298 genotypes with environmental factors

BACKGROUND

Polymorphisms in methylenetetrahydrofolate reductase (MTHFR), such as MTHFR C677T and A1298C, are associated with several cancers. This study aimed to evaluate the effects of MTHFR polymorphisms on colon cancer risk and possible interactions with environmental factors in a population from northeastern Thailand.

METHODS

This hospital-based case-control study was conducted during 2002-2006; 130 colon cancer cases and 130 age- and sex-matched controls were enrolled. Information was collected and blood samples were obtained for assay of MTHFR C677T and A1298C polymorphisms by polymerase chain reaction with restriction fragment length polymorphism techniques. Associations between variables of interest and colon cancer were assessed using conditional logistic regression.

RESULTS

Increased risk of colon cancer was associated with alcohol consumption and bowel habits. Alcohol drinkers who consumed < or = 0.50 or >0.50 units of alcohol per day had elevated risks (OR(adj) = 3.5; 95% CI: 1.19-10.25 and OR(adj) = 1.71; 95% CI: 0.74-3.96, respectively). The risk was also higher in subjects with frequent constipation (11.69; 2.18-62.79) and occasional constipation (3.43; 1.72-6.82). An interaction was observed between the MTHFR C677T polymorphism and freshwater fish consumption on colon cancer risk (P value for interaction = 0.031). Interactions were observed between the MTHFR A1298C polymorphism and bowel habits, family history of cancer, alcohol consumption, and beef consumption on colon cancer risk (P-value for interaction = 0.0005, 0.007, 0.067, 0.003, respectively).

CONCLUSIONS

In a Thai population, colon cancer risk was associated with alcohol and beef consumption, bowel habits, and family history of cancer. Interactions between MTHFR polymorphisms and environmental factors were also observed.

Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps

BACKGROUND

Several dietary factors have been considered to be involved in the increasing incidence of colorectal cancer in industrialised countries. Experimental and epidemiological evidence has been suggestive but not conclusive for a protective role for high dietary calcium intake. Intervention studies with colorectal cancer as an endpoint are difficult to perform owing to the large number of patients and the long follow-up required; studies using the appearance of colorectal adenomatous polyps as a surrogate endpoint are therefore considered in reviewing the existing evidence.

OBJECTIVES

This systematic review aims to assess the effect of supplementary dietary calcium on the incidence of colorectal cancer and the incidence or recurrence of adenomatous polyps.

SEARCH STRATEGY

We searched the Cochrane Controlled Trials Register, the Cochrane Colorectal Cancer Group specialised register, MEDLINE, Cancerlit , and Embase, to July 2007. The reference lists of identified studies were inspected for further studies, and the review literature was scrutinized.

SELECTION CRITERIA

Randomised controlled trials of the effects of dietary calcium on the development of colonic cancer and adenomatous polyps in humans are reviewed. Studies of healthy adults and studies of adults at higher risk of colon cancer due to family history, previous adenomatous polyps, or inflammatory bowel disease were considered; data from subjects with familial polyposis coli are excluded. The primary outcomes were the occurrence of colon cancer, and occurrence or recurrence of any new adenomas of the colon. Secondary outcomes were any adverse event that required discontinuation of calcium supplementation, and drop-outs before the end of the study.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data, assessed trial quality and resolved discrepancies by consensus. The outcomes were reported as odds ratios (OR) with 95% confidence intervals (CI). The data were combined with the fixed effects model.

MAIN RESULTS

Two studies with 1346 subjects met the inclusion criteria. Both trials were well designed, double - blind, placebo controlled trials, included participants with previous adenomas. The doses of supplementary elemental calcium used were 1200 mg daily for a mean duration of 4 years, and 2000 mg/day for three years. The rates of loss to follow -up were 14 % and 11%. For the development of recurrent colorectal adenoma, a reduction was found (OR 0.74, CI 0.58,0.95) when the results from both trials were combined.

AUTHORS' CONCLUSIONS

Although the evidence from two RCTs suggests that calcium supplementation might contribute to a moderate degree to the prevention of colorectal adenomatous polyps, this does not constitute sufficient evidence to recommend the general use of calcium supplements to prevent colorectal cancer.

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.

Carbohydrate Digestibility Predicts Colon Carcinogenesis in Azoxymethane-Treated Rats

The purpose of this study was to compare the effect of carbohydrate structure and digestibility on azoxymethane (AOM)-induced colon carcinogenesis. Five groups of male Fischer 344 rats each comprising 30 animals were injected with AOM and fed a high-fat diet with 15% of various carbohydrates. The carbohydrate sources used were sucrose, cornstarch (a linear starch, reference group), potato starch (a branched starch), a short-chained oligofructose (Raftilose), and a long-chained inulin-type fructan (Raftiline). An interim sacrifice was performed after 9 wk to investigate markers of carbohydrate digestibility, including caecal fermentation (caecum weight and pH) and glucose and lipid metabolism [glucose, fructoseamine, HbA1c, triglycerides, and insulin-like growth factor (IGF) 1]. In addition potential early predictors of carcinogenicity [cell proliferation and aberrant crypt foci (ACF)] at 9 wk and their correlation to colon cancer risk after 32 wk were investigated. Tumor incidence was significantly reduced in animals fed oligofructose, and the number of tumors per animal was significantly reduced in animals fed inulin and oligofructose at 32 wk after AOM induction compared to the reference group fed sucrose. Increased caecum weight and decreased caecal pH were seen in groups fed oligofructose, inulin, and potato starch. Plasma triglyceride was decreased in rats fed oligofructose and inulin. Cell proliferation was increased in the proximal colon of rats fed sucrose, oligofructose, and inulin, and the number of cells per crypt decreased in rats fed oligofructose and inulin. The total number of ACF's was unaffected by treatment, and the size and multiplicity of ACF was unrelated to tumor development. It was concluded that less digestible carbohydrates with an early effect on caecum fermentation and plasma triglyceride decreased subsequent tumor incidence and multiplicity. This was unrelated to ACF, cell proliferation, and other markers of glucose and lipid metabolism.

Major Scientific Advances with Dairy Foods in Nutrition and Health

A large body of scientific evidence collected in recent decades demonstrates that an adequate intake of calcium and other nutrients from dairy foods reduces the risk of osteoporosis by increasing bone acquisition during growth, slowing age-related bone loss, and reducing osteoporotic fractures. These results have culminated in the new (2005) Dietary Guidelines for Americans that now recommend 3 servings of milk products per day to reduce the risk of low bone mass and contribute important amounts of many nutrients that may have additional health attributes beyond bone health. A number of animal, observational, and clinical studies have shown that dairy food consumption can help reduce the risk of hypertension. Clinical trials indicate that the consumption of recommended levels of dairy products, as part of a healthy diet, can contribute to lower blood pressure in individuals with normal and elevated blood pressure. Emerging data also indicate that specific peptides associated with casein and whey proteins can significantly lower blood pressure. In addition, a growing body of evidence has provided support for a beneficial effect of dairy foods on body weight and fat loss. Clinical studies have demonstrated that during caloric restriction, body weight and body fat loss occurs when adequate calcium is provided by supplements and that this effect is further augmented by an equivalent amount of calcium supplied from dairy foods. Several studies support a role for calcium, vitamin D, and dairy foods against colon cancer. Additionally, conjugated linoleic acid, a fatty acid found naturally in dairy fat, confers a wide range of anticarcinogenic benefits in experimental animal models and is especially consistent for protection against breast cancer.

Obesity and colorectal cancer: epidemiology, mechanisms and candidate genes

There is increasing evidence that dysregulation of energy homeostasis is associated with colorectal carcinogenesis. Epidemiological data have consistently demonstrated a positive relation between increased body size and colorectal malignancy, whereas mechanistic studies have sought to uncover obesity-related carcinogenic pathways. The phenomenon of "insulin resistance" or the impaired ability to normalize plasma glucose levels has formed the core of these pathways, but other mechanisms have also been advanced. Obesity-induced insulin resistance leads to elevated levels of plasma insulin, glucose and fatty acids. Exposure of the colonocyte to heightened concentrations of insulin may induce a mitogenic effect within these cells, whereas exposure to glucose and fatty acids may induce metabolic perturbations, alterations in cell signaling pathways and oxidative stress. The importance of chronic inflammation in the pathogenesis of obesity has recently been highlighted and may represent an additional mechanism linking increased adiposity to colorectal carcinogenesis. This review provides an overview of the epidemiology of body size and colorectal neoplasia and outlines current knowledge of putative mechanisms advanced to explain this relation. Family based studies have shown that the propensity to become obese is heritable, but this is only manifest in conditions of excess energy intake over expenditure. Inheritance of a genetic profile that predisposes to increased body size may also be predictive of colorectal cancer. Genomewide scans, linkage studies and candidate gene investigations have highlighted more than 400 chromosomal regions that may harbor variants that predispose to increased body size. The genetics underlying the pathogenesis of obesity are likely to be complex, but variants in a range of different genes have already been associated with increased body size and insulin resistance. These include genes encoding elements of insulin signaling, adipocyte metabolism and differentiation, and regulation of energy expenditure. A number of investigators have begun to study genetic variants within these pathways in relation to colorectal neoplasia, but at present data remain limited to a handful of studies. These pathways will be discussed with particular reference to genetic polymorphisms that have been associated with obesity and insulin resistance.

Early life events and later risk of colorectal cancer: age-period-cohort modelling in the Nordic countries and Estonia

BACKGROUND

A lowering of colorectal cancer risk for the birth cohorts born around World War II (WWII) has previously been observed in Norway, a country which suffered some 20% caloric restriction during the war. The purpose of the study was to conduct a similar kind of analysis in the other Nordic countries and Estonia, which were also subjected to various degrees of energy restriction during WWII.

METHODS

All new cases of colorectal cancer in the Nordic countries and Estonia diagnosed between 40 and 84 years of age and born between 1874 and 1953, were collected from the national cancer registries. The incidence data were fitted to an age-period-cohort model.

RESULTS

A transient drop in the estimated colorectal cancer incidence rate was observed for the birth cohorts born around WWII in Estonia, together with a tendency of decreased risk in Sweden and Denmark.

CONCLUSION

The previously observed lowering of colorectal cancer risk for persons born during WWII in Norway also prevails in Estonia. Energy restriction is a possible explanation for these findings, since the countries suffered from varying nutritional conditions during the war. Exogenous factors acting during periods early in life may have an impact on later colorectal cancer risk.

Dietary calcium supplementation for preventing colorectal cancer and adenomatous polyps

BACKGROUND

Several dietary factors have been considered to be involved in the increasing incidence of colorectal cancer in industrialised countries. Experimental and epidemiological evidence has been suggestive but not conclusive for a protective role for high dietary calcium intake. Intervention studies with colorectal cancer as an endpoint are difficult to perform owing to the large number of patients and the long follow-up required; studies using the appearance of colorectal adenomatous polyps as a surrogate endpoint are therefore considered in reviewing the existing evidence.

OBJECTIVES

This systematic review aims to assess the effect of supplementary dietary calcium on the incidence of colorectal cancer and the incidence or recurrence of adenomatous polyps.

SEARCH STRATEGY

We searched the Cochrane Controlled Trials Register, the Cochrane Colorectal Cancer Group specialised register, MEDLINE, Cancerlit, and Embase, to April 2002. The reference lists of identified studies were inspected for further studies, and the review literature was scrutinized.

SELECTION CRITERIA

Randomised controlled trials of the effects of dietary calcium on the development of colonic cancer and adenomatous polyps in humans are reviewed. Studies of healthy adults and studies of adults at higher risk of colon cancer due to family history, previous adenomatous polyps, or inflammatory bowel disease were considered; data from subjects with familial polyposis coli are excluded. The primary outcomes were the occurrence of colon cancer, and occurrence or recurrence of any new adenomas of the colon. Secondary outcomes were any adverse event that required discontinuation of calcium supplementation, and drop-outs before the end of the study.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data, assessed trial quality and resolved discrepancies by consensus. The outcomes were reported as odds ratios (OR) with 95% confidence intervals (CI). The data were combined with the fixed effects model.

MAIN RESULTS

Two studies with 1346 subjects met the inclusion criteria. Both trials were well designed, double - blind, placebo controlled trials, included participants with previous adenomas. The doses of supplementary elemental calcium used were 1200 mg daily for a mean duration of 4 years, and 2000 mg/day for three years. The rates of loss to follow -up were 14 % and 11%. For the development of recurrent colorectal adenoma, a reduction was found (OR 0.74, CI 0.58,0.95) when the results from both trials were combined.

AUTHORS' CONCLUSIONS

Although the evidence from two RCTs suggests that calcium supplementation might contribute to a moderate degree to the prevention of colorectal adenomatous polyps, this does not constitute sufficient evidence to recommend the general use of calcium supplements to prevent colorectal cancer.

Diet and colorectal cancer: implications for the obese and devotees of the Atkins diet

Colorectal cancer (CRC) is the second most common cause of cancer-related death in the Western world and its prevalence is increasing. Potential causes of this increase are changes in diet and the increases in obesity seen. This paper looks at the literature surrounding diet and obesity and the links to this increase in CRC. Heralded as a weight loss miracle we investigate whether the literature suggests the Atkins diet may actually do more harm than good by acting to increase an individual's risk of CRC. Obesity has been demonstrated to be a major factor in the increase in CRC although links to changes in diet are more tenuous. Published studies on diet suggest the Atkins diet may help reduce rather than increase the risk of CRC.

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.

Energy balance, insulin-related genes and risk of colon and rectal cancer

Energy balance, or the ability to maintain body weight by balancing energy intake with energy expenditure, appears to be important in the etiology of colon cancer. One possible mechanism whereby energy balance may be associated with colorectal cancer is through its association with insulin. In our study, we evaluate the interaction between polymorphisms in 4 genes thought to be involved in insulin-related functions and components of energy balance with risk of colorectal cancer. Data from 2 population-based case-control studies of colon and rectal cancer conducted in Utah and Northern California were used to evaluate associations between body mass index (BMI), physical activity, energy intake and sucrose-to-fiber ratio and a CA repeat polymorphism of the IGF1 gene, the A/C polymorphism at nucleotide -202 of the IGFBP3, the G972R polymorphism of the IRS1 gene and the G1057D polymorphism of the IRS2 gene. A total of 1,346 incident colon cancer cases and 1,544 population-based controls and 952 incident rectal cancer cases and 1,205 controls were available for analysis. Inconsistent associations were identified between BMI, physical activity, energy intake and insulin-related genes. The 192/192 IGF1 genotype was associated with significant reduction in colon cancer risk among those with high physical activity (odds ratio [OR] 0.57; 95% confidence interval [CI] 0.39-0.83; p interaction 0.01). Although there was no significant pattern of interaction between either BMI or energy intake and polymorphisms assessed, specific sources of energy did appear to be more related to colon cancer risk in the presence of specific IRS2 and IGF1 genotypes. A high sucrose-to-fiber ratio increased risk of colon cancer in men who had the IRS2 DD genotype and among men who did not have the 192/192 IGF1 genotype. In summary, these data support the importance of components of energy balance in risk of colorectal cancer. Obesity, physical activity and energy intake appear to alter risk of colorectal cancer; however, the risk appears to be minimally influenced by genetic variants evaluated.

Associations between BMI, energy intake, energy expenditure, VDR genotype and colon and rectal cancers (United States)

Components of energy balance are important elements associated with colorectal cancer risk. In this study we examine the association between VDR genotypes, BMI, physical activity, and energy intake and risk of colorectal cancer. Data from a population-based case-control study of colon (1174 cases and 1174 controls) and rectal (785 cases and 1000 controls) cancer was used to evaluate the associations. The Bsm1, polyA, and Fok1 VDR polymorphisms were evaluated. For colon cancer, those who are obese were at greater risk of colon cancer if they had the SS or BB (OR = 3.50; 95% CI = 1.75-7.03; p interaction 0.03) or ff (OR = 2.62; 95% CI = 1.15-5.99; p interaction 0.12/) VDR genotypes. On the other hand, those who were least physically active were at greater risk of colon cancer if they had the ff VDR genotype (OR = 3.46; 95% CI = 1.58-7.58; p interaction 0.05). The association between energy intake and colon cancer appears to be driven more by energy intake than Bsm1 or polyA VDR genotypes, although there was a significant interaction between the Fok1 VDR polymorphism and energy intake and risk of both colon and rectal cancer (p interaction 0.01 for colon and 0.04 for rectal). These data suggest a relationship between VDR genotype and factors related to energy balance in modifying colorectal cancer risk.

Physical activity and colorectal cancer

Physical activity has been shown to reduce risk of colon cancer. Some studies have shown site-specific associations while others have not. The inverse association between physical activity and colon cancer is consistent although only 7 of 13 studies that have collected both colon and rectal cancer data in the same manner report reduced risk for rectal cancer; four of these studies detected statistically significant inverse associations. The frequency, duration and intensity of activity are important components of a public health message to reduce risk of colon cancer through performance of physical activity. However, difficulties in estimating the exact amount of activity needed and frequency and intensity of activity result in only crude estimates of dose needed for a protective effect. Much of the literature suggest that more intense activity is needed to reduce colon cancer risk and that somewhere between 3.5 and 4 hours of vigorous activity per week may be needed to optimise protection. Several biological mechanisms have been proposed to explain the association between physical activity and colon cancer; many of these mechanisms also support the observation that intense activities are most protective. Biological mechanisms include: physical activity increasing gut motility; enhancing the immune system; decreasing insulin and insulin-like growth factor levels; decreasing obesity; enhancing free radical scavenger systems; and influencing prostaglandin levels. The evidence taken together provides strong support for lack of physical activity being causally related to colon cancer. It has been estimated that 12-14% of colon cancer could be attributed to lack of frequent involvement in vigorous physical activity.

Postsurgical disparity in survival between African Americans and Caucasians with colonic adenocarcinoma

BACKGROUND

Studies of colorectal adenocarcinoma (CRC) indicate a higher mortality rate for African Americans compared with Caucasians in the United States. In the current study, the authors evaluated the racial differences in survival based on tumor location and pathologic stage between African-American patients and Caucasian patients who underwent surgery alone for CRC.

METHODS

All 199 African American patients and 292 randomly selected, non-Hispanic Caucasian patients who underwent surgery between 1981 and 1993 for first primary sporadic CRC at the University of Alabama-Birmingham (Birmingham, AL) or an affiliated Veterans Affairs hospital were assessed for differences in survival. None of these patients received preoperative or postoperative neoadjuvant or adjuvant therapy. Survival curves were generated using the Kaplan-Meier method, and hazard ratios with 95% confidence intervals (95% CI) were estimated from Cox proportional hazards models, adjusting for demographic and tumor characteristics.

RESULTS

African Americans were 1.67 (95% CI, 1.21-2.33) and 1.52 (95% CI, 1.12-2.07) times more likely to die of colonic adenocarcinoma (CAC) within 5 years and 10 years of surgery, respectively, compared with Caucasians. Racial differences in survival were observed among patients with Stage II, III, and IV CAC; however, the strongest and statistically significant association was observed among patients with Stage II CAC. There were no significant racial differences in survival in patients with rectal adenocarcinomas.

CONCLUSIONS

The current findings suggest that the decreased overall survival at 5 years and 10 years postsurgery observed in African-American patients with CAC may not be attributable to tumor stage at diagnosis or treatment but may be due to differences in other biologic or genetic characteristics between African-American patients and Caucasian patients.

Energy balance and rectal cancer: an evaluation of energy intake, energy expenditure, and body mass index

Lack of energy balance, or greater energy intake than expenditure as indicated by a large body mass index (BMI), has been associated with colon cancer, although less is known about its association with rectal cancer. In this study, we examined the association between BMI, energy intake, and energy expenditure and their combined effect on rectal cancer risk. A population-based case-control study was conducted in Utah and Northern California. Incident cases (n = 952) of rectal cancer and population-based controls (n = 1205) were interviewed between 1997 and 2002 to obtain detailed information on body size, dietary intake, and physical activity patterns. BMI (kg/m(2)) was not associated with rectal cancer in either men or women. Participation in vigorous leisure-time physical activity over the past 20 yr was associated with a significant 40% reduction in rectal cancer risk. Energy intake was associated significantly with increased risk of rectal cancer, especially among people whose diagnosis was prior to age 60 yr (odds ratio [OR] = 3.9; 95% confidence interval [CI] = 1.7-9.1 for men; OR = 2.8; 95% CI = 1.1-7.2 for women). There was a significant interaction between energy intake and energy expenditure, although not between BMI and either energy intake or energy expenditure. These data suggest that large BMI, an indicator of lack of energy balance, is not an important component of the etiology of rectal cancer. However, both physical activity and energy intake were significantly associated with rectal cancer risk. These data suggest that energy expenditure and energy intake alter rectal cancer risk through mechanisms other than energy balance.

Rat strain specific attenuation of estrogen action in the anterior pituitary gland by dietary energy restriction

The purpose of this study was to compare the effects of a 40% restriction of dietary energy consumption, relative to that consumed by rats allowed to feed ad libitum, on the ability of 17beta-estradiol (E2) to induce pituitary tumorigenesis in two inbred rat strains, ACI and Copenhagen (COP), which are very closely related genetically. Ovary-intact ACI and COP rats were fed either a control or an energy-restricted diet beginning at 8 wk of age. Continuous treatment with E2, released from subcutaneous Silastic tubing implants, was initiated at 9 wk of age and the animals were killed 12 wk later. Estrogen-induced pituitary tumorigenesis is associated with rapid induction of lactotroph hyperplasia, increased pituitary mass, and hyperprolactinemia. E2 significantly increased pituitary mass and circulating prolactin (PRL) in both ACI and COP rats, and this response was significantly greater in ACI rats relative to COP. Dietary energy restriction did not inhibit E2-induced pituitary growth in the ACI rat. By contrast, E2-induced pituitary growth in COP rats was attenuated by dietary energy restriction, as evidenced by quantification of pituitary mass, pituitary weight to body weight ratio, circulating PRL, and pituitary cell proliferation. This study indicates that sensitivity to the inhibitory actions of dietary energy restriction on E2-induced pituitary tumorigenesis is genetically determined.

Energy restriction early in life and colon carcinoma risk: results of The Netherlands Cohort Study after 7.3 years of follow-up

BACKGROUND

This study evaluated the effects of severe undernutrition during adolescence and subsequent colon carcinoma risk.

METHODS

The authors evaluated The Netherlands Cohort Study on Diet and Cancer (NLCS) among 62,573 women and 58,279 men aged 55-69 years at baseline. Information on diet and risk factors was collected by questionnaire in 1986. Additional information was collected concerning residence during the hunger winter (1944-1945), the World War II years (1940-1944), and father's employment status during the economic depression of 1932-1940, which were used as indicators of exposure. After 7.3 years of follow-up, 807 colon carcinoma cases (388 females and 419 males) were available for analysis.

RESULTS

Multivariate analysis showed that both men and women who had lived in a western city in 1944-1945 had a decreased colon carcinoma risk (men: relative risk [RR] = 0.85, 95% confidence interval [CI] = 0.62-1.16; women: RR = 0.80, 95% CI = 0.59-1.09). No association between colon carcinoma risk and urban versus rural residence was found during the war years (1940-1944). Having an unemployed father during the economic depression (1932-1940) was also associated with a small decrease in colon carcinoma risk for men (RR = 0.90, 95% CI =0.62-1.31) and women (RR = 0.75, 95% CI 0.49-1.14). In subgroup analyses, a decreased colon carcinoma risk for men and women who were in their adolescent growth spurt and living in a western city during the hunger winter of 1944-1945 was noted (men: RR = 0.72, 95% CI = 0.31-1.65; women: RR = 0.88, 95% CI = 0.40-1.96). No associations were statistically significant because of the limited study size.

CONCLUSIONS

In the current study, a weak inverse relation was found between energy restriction early in life and subsequent colon carcinoma risk for men and women. However, these findings need replication in a larger study.

Energy intake, body mass index, physical activity, and the colorectal adenoma-carcinoma sequence

Little is known about the precise relationship between energy intake, overweight, sedentary lifestyle, and steps in the colorectal adenoma-carcinoma pathway. We studied these parameters within a case-control study. Patients with adenomas < 10 mm (n = 154) or > 10 mm (n = 208) were compared with polyp-free controls (n = 426) for determining factors associated with adenoma formation, i.e., observed for small and large adenomas, or with adenoma growth only. Colorectal cancer cases (n = 171) were compared with population controls (n = 309) to determine factors specific to the final stage, cancer. Exercise reduced the risk of cancer [odds ratio (OR) = 0.3, 95% confidence interval (CI) = 0.2-0.5 for high vs. low physical activity] but had little influence on adenomas. High energy intake increased the risk of cancer [OR for 5th vs. 1st quintile (OR5) = 1.6, 95% CI = 0.9-2.9, p = 0.02], but not of adenomas. High body mass index (BMI) significantly increased the risk of large adenomas (OR5 = 2.1, 95% CI = 1.2-3.5, p = 0.02 and OR5 = 1.7, 95% CI = 1.0-3.1, p = 0.25) for large and small adenomas vs. polyp-free controls. Neither height nor weight nor BMI influenced the risk of cancer. Results were unmodified when controlling for dietary risk factors and family history. Energy intake, a sedentary lifestyle, and high BMI were independently associated with a high risk of cancer itself or large adenomas, which indicates an effect on promotion of colorectal tumors. These findings suggest that preventive advice regarding these factors should be provided, even late in life, to decrease the risk of colorectal cancer.

Food restriction inhibits the growth of intestinal polyps in multiple intestinal neoplasia mouse

The effect of food restriction (FR) on spontaneous intestinal carcinogenesis in multiple intestinal neoplasia (Min) mice was examined. Thirty male Min mice were allotted to ad libitum feeding control and 20% FR groups from six weeks of age until the end of the 13-week experimental period. Although the total number of visible intestinal polyps in the FR group was not significantly different from the control group value, a significant decrease in large-sized polyps (>2 mm) and an increase in small-sized polyps (< or =2 mm) were observed in the distal small intestine. In this segment, the percentage of apoptotic cells counted in intestinal polyps in the FR group was significantly higher than in the control group, the percentage of proliferating cell nuclear antigen (PCNA)-positive cells not being significantly different. These results indicate that the FR may inhibit the growth of intestinal polyps in the Min mouse, and that apoptosis contributed in part to the inhibitory effect.

Dietary fat, cholesterol and colorectal cancer in a prospective study

The relationships between consumption of total fat, major dietary fatty acids, cholesterol, consumption of meat and eggs, and the incidence of colorectal cancers were studied in a cohort based on the Finnish Mobile Clinic Health Examination Survey. Baseline (1967-1972) information on habitual food consumption over the preceding year was collected from 9959 men and women free of diagnosed cancer. A total of 109 new colorectal cancer cases were ascertained late 1999. High cholesterol intake was associated with increased risk for colorectal cancers. The relative risk between the highest and lowest quartiles of dietary cholesterol was 3.26 (95% confidence interval 1.54-6.88) after adjusting for age, sex, body mass index, occupation, smoking, geographic region, energy intake and consumption of vegetables, fruits and cereals. Consumption of total fat and intake of saturated, monounsaturated, or polyunsaturated fatty acids were not significantly associated with colorectal cancer risk. Nonsignificant associations were found between consumption of meat and eggs and colorectal cancer risk. The results of the present study indicate that high cholesterol intake may increase colorectal cancer risk, but do not suggest the presence of significant effects of dietary fat intake on colorectal cancer incidence.

Changes in diet following the formation of a colostomy

The main aim of this small study was to discover if the formation of a colostomy could adversely affect the long-term dietary intake of patients. While it would seem that there were few adverse effects on nutrient intake after surgery, it became apparent that patients had a need for clear dietary advice. It seemed that this area of their care was lacking. Because of the small number of patients recruited for the study statistical validation was not possible. Therefore, this study is only able to point the way forward for further research into the dietary needs of colostomy patients and the health professional role in this area of care.

A case-control study of diet and testicular carcinoma

No risk factor other than cryptorchidism has been consistently associated with testicular cancer, and the influence of diet on testicular cancer risk has not been extensively explored. A few studies have found increased testicular cancer risk in men whose diets are high in fat, red meats, and milk or low in fruits and vegetables. We evaluated the relationship of dietary factors and risk of testicular cancer and also examined whether this risk varied by type of testicular cancer. We conducted a hospital-based case-control study at The University of Texas M. D. Anderson Cancer Center (Houston, TX) of 160 testicular cancer cases diagnosed between 1990 and 1996 and 136 friend-matched controls. The results of multivariable logistic regression analysis showed that after adjustment for age, education, income, ethnicity, cryptorchidism, and total daily calories, increasing total fat, saturated fat, and cholesterol consumption were associated with increasing risk of nonseminoma testicular cancer, with odds ratios (ORs) for the highest vs. the lowest quartiles of 6.3, 5.3, and 4.6, respectively. The risk for seminoma testicular cancer marginally increased with increasing intake of total fat and saturated fat, with ORs for the highest vs. lowest quartiles of 1.9 and 2.1, respectively. Higher total fat consumption was nearly significantly related to increased mixed germ cell tumor risk, with an OR for highest vs. lowest quartile of 4.2. This study supports the hypothesis that diet (particularly high fat consumption) increases testicular cancer risk in young men. However, the small sample size and the possibility that these observations may be due to bias indicate that the relationship of diet and testicular cancer risk needs to be further examined within a prospective or incident case-control study.

Population-attributable risk for colon cancer in Italy

Risk factors for colon cancer have essentially been considered in terms of relative risks. From a public health viewpoint, however, their impact depends not only on the strength of the association, but also on the distribution of exposures in the population. Thus we used data from a case-control study conducted in Italy between 1992 and 1996 to estimate the population-attributable risks (PARs) for colon cancer in relation to educational level, physical activity, energy and vegetable intake, eating frequency, and family history of colorectal cancer. Cases were 1,225 incident, histologically confirmed colon cancer patients admitted to the major teaching and general hospitals in six Italian areas; controls were 4,154 subjects with no history of cancer, admitted to hospitals in the same catchment areas for acute, nonneoplastic diseases. By use of the distribution of the risk factors in the cases and the multivariate relative risk estimates, PARs were computed, i.e., the proportion of colon cancer that would have been avoided if all subjects were moved to the lowest exposure level. The PARs were 12% for high education, 14% for low physical activity, 14% for high energy intake, 22% for low vegetable intake, 7% for high eating frequency, and 8% for a family history of colorectal cancer. These factors together accounted for 56% of colon cancer cases. PARs were similar across age strata. Men had higher PARs for education, physical activity, and their combination, but lower PARs for energy, eating frequency, vegetable intake, and their combination than women. The percentage of colon cancers attributable to all factors considered together was 50% in men and 67% in women. Even if the PAR estimates were based on several arbitrary assumptions on the exposure distribution for various risk factors, available knowledge could, in principle, explain > 50% of cases in this Italian population, thus indicating and quantifying the theoretical scope for prevention.

Physical activity, body mass index, and prostaglandin E2 levels in rectal mucosa

BACKGROUND

Evidence suggests a relationship between prostaglandin levels in colonic mucosa and risk of colon cancer. Physical inactivity and a higher body mass index (BMI; weight in kilograms divided by [height in meters]2) have been consistently shown to increase risk of this cancer. We investigated whether higher levels of leisure-time physical activity or a lower BMI was associated with lower concentrations of prostaglandin E2 (PGE2) in rectal mucosa.

METHODS

This study was conducted in 41 men and 22 women, 42-78 years of age, with a history of polyps, who participated in a randomized clinical trial testing the effects of piroxicam on rectal mucosal PGE2 levels. An [125I]PGE2 radioimmunoassay kit was used to determine PGE2 levels in samples of extracted rectal mucosa collected before randomization. Leisure-time physical activity was assessed through a self-administered questionnaire collected at baseline. The reported time spent at each activity per week was multiplied by its typical energy expenditure, expressed in metabolic equivalents (METs), to yield a MET-hours per week score. A repeated measures model was used to assess the effect of BMI and physical activity as predictors of PGE2 concentration. All statistical tests were two-sided.

RESULTS

After adjustment for age, a higher BMI was associated with higher PGE2 levels (P = .001). A higher level of leisure-time physical activity was inversely associated with PGE2 concentration (P<.03). An increase in BMI from 24.2 to 28.8 kg/m2 was associated with a 27% increase in PGE2. An increase in activity level from 5.2 to 27.7 MET-hours per week was associated with a 28% decrease in PGE2.

CONCLUSIONS

Physical activity and obesity may alter the risk of colon cancer through their effects on PGE2 synthesis.

Energy restriction modulates the development of advanced preneoplastic lesions depending on the level of fat in the diet

Our objective was to investigate the ability of preneoplastic colonic lesions at different stages of development to respond to the growth-retarding effects of energy restriction (ER). Male Fischer 344 rats were given three injections of azoxymethane (15 mg/kg s.c.) and fed a high-fat corn oil diet for 16 weeks. This duration allowed aberrant crypt foci (ACF) to develop and acquire different growth states. ACF growth was assessed by enumerating the number of crypts per focus. At Week 16, 10 animals were killed and their colons were enumerated for ACF (baseline). The remaining animals were then allocated to four dietary groups: high-fat (23% wt/wt), low-fat (5% wt/wt), high-fat energy-restricted (HFER), or low-fat energy-restricted (LFER). After the animals were fed the experimental diets for six weeks, ER decreased the total number of ACF regardless of the level of fat. At Week 12, the LFER diet retarded the appearance of advanced ACF, but this was not the case for the HFER diet. Consequently, the level of fat was identified as the significant variable in affecting the number of ACF with different crypt multiplicity. The animals fed the LFER diet had the fewest tumors and microadenomas per rat. The HFER diet was ineffective in modulating tumor outcome. To our knowledge, these findings are the first to suggest that ER modulated the development of advanced ACF and colonic tumors depending on the level of fat in the diet.

A comparison of prospective and retrospective assessments of diet in a study of colorectal cancer

Dietary factors are widely studied as risk factors for colorectal cancer, with much information from case-control studies. We evaluated the validity of dietary data from a retrospective case-control study of diet and colorectal cancer. As part of the alpha-Tocopherol, beta-Carotene Cancer Prevention Study, diet was assessed at baseline and after diagnosis for colorectal cancer cases and at baseline and regularly during the trial for a random control group. The dietary assessment referred to the previous 12 months (in cases before diagnosis). In the two dietary assessments, the cases reported a greater increase in consumption of fruits and dairy products and a decrease in consumption of potatoes. Accordingly, relative risks for colorectal cancer by baseline dietary data differed markedly from odds ratios from case-control data; e.g., relative risk for a 652-mg increase in calcium intake was 0.79 (95% confidence interval = 0.48-1.30) in case-cohort analysis vs. an odds ratio of 1.57 (95% confidence interval = 1.06-2.33) for case-control analysis. The most likely explanation is the influence of current diet on recall of prediagnosis diet and effects of occult cancer on diet in the year before cancer diagnosis, which have implications for interpretation of case-control studies in evaluating associations between diet and colorectal cancer.

Modulation of estrogen action in the rat pituitary and mammary glands by dietary energy consumption

We are investigating the mechanisms through which estrogens induce development of prolactin (PRL)-producing pituitary tumors and mammary carcinomas in rats and how these mechanisms are affected by dietary energy consumption. The hypothesis under examination is that dietary energy restriction inhibits tumorigenesis in estrogen-responsive tissues by altering cellular responsiveness to estrogenic hormones. In the Fischer 344 (F344) rat strain, a 40% restriction of energy consumption virtually abolishes development of estrogen-induced pituitary tumors. Inhibition of pituitary tumorigenesis in the F344 strain by energy restriction results from modulation of estrogen regulation of cell survival, not cell proliferation. In contrast, energy restriction has no inhibitory effect on estrogen-induced pituitary tumor development in the ACI rat strain. However, energy restriction markedly inhibits induction of mammary carcinomas in female ACI rats treated with 17beta-estradiol. Data presented herein indicate that dietary energy restriction modulates the responsiveness of specific cell populations to estrogenic hormones and thereby inhibits estrogen-induced tumorigenesis in a manner specific to both rat strain and tissue.

Body size and colorectal-cancer risk

Individuals whose energy intake exceeds expenditure are at increased risk of colorectal cancer. To determine whether body-size measurements at different ages were risk factors for cancer of the colon-rectum, we carried out a hospital-based case-control study in 6 Italian areas, 2 of which were in the South. Interviews were conducted with 1,217 subjects of both genders with incident histologically confirmed cancer of the colon, 726 with cancer of the rectum, and 4,136 controls hospitalized for acute, non-neoplastic, non-digestive conditions. The questionnaire included information on sociodemographic factors, and physical activity, a validated dietary history, height, weight at diagnosis and at 12, 30 and 50 years of age and waist-to-hip ratio (WHR). After allowance for education, physical activity, energy intake, family history of colorectal cancer and recent change in weight, the body-mass index (BMI) was significantly associated with colorectal-cancer-risk in men (odds ratio, OR, in highest vs. lowest quintile = 1.7; 95% confidence interval, CI, 1.3-2.3), but not in women (corresponding OR = 0.9; 95% CI, 0.7-1.2). Cases of both gender tended to have higher BMI than controls in adolescence, young adulthood and middle age. Height appeared unrelated to risk. In women, but not in men, WHR was positively associated with risk, independently of BMI (OR for > or = 0.90 vs. < or = 0.81 = 1.6; 95% CI; 1.2-2.1). Thus, excessive weight predicts colorectal-cancer risk in men, whereas abdominal obesity (i.e., a high WHR) represents a more reliable risk indicator in women.

Nutritional and metabolic aspects of gastrointestinal cancer

It is widely accepted that diet is important in the aetiology of cancer of the human gastrointestinal tract, but the rates of progress in unravelling the associations have varied at the different subsites, and with the different histological types of cancers. We have reached the stage of recognizing the problems, but have only begun to address them. Progress has been most rapid in the large bowel and least rapid in adenocarcinoma of the oesophagus and gastric cardia.

Dietary carbohydrates and the colonic microflora

The world of the colonic microflora has lain dormant in recent years, but is coming alive now with the advent of new chemical and molecular technologies for identifying bacteria, and the emergence of the concepts of biofilms, pro- and prebiotics. That bacteria play an essential role in barrier resistance to infection, ulcerative colitis and colorectal cancer is slowly becoming clear. New potential therapeutic avenues using bacteria should soon start to open up. Scientifically we lack an understanding of the mechanisms at work.

Physical activity and the primary prevention of cancer

Evidence has been accumulating that suggests that physical activity may help reduce the risk of cancer. Physically active people have been shown to have a decreased rate of all-cancer mortality. The incidence of colon, breast, and perhaps prostate cancer are decreased in more active people when compared with their sedentary peers. Chronic physical activity may decrease tumor risk by its effect on natural immunity, antioxidant defenses, improved energy balance, hormonal changes, or by other unknown mechanisms.

Dietary fat consumption and health

Dietary Guidelines have emerged over the past 30 years recommending that Americans limit their consumption of total fat and saturated fat as one way to reduce the risk of a range of chronic diseases. However, a low-fat diet is not a no-fat diet. Dietary fat clearly serves a number of essential functions. For example, maternal energy deficiency, possible exacerbated by very low-fat intakes (< 15% of energy), is one key determinant in the etiology of low birth weight. The debate continues over recommendations for limiting total fat and saturated fatty acid intake in children. Recent evidence indicates that diets with adequate energy providing less than 30% of energy from fat are sufficient to promote normal growth and normal sexual maturation. More attention needs to be devoted to the effect of dietary fat reduction on the nutrient density of children's diets. The association between dietary fat and CHD has been extensively studied. Diets high in saturated fatty acids and trans fatty acids increase LDL cholesterol levels, and in turn, the risk of heart disease. The relationship between high-carbohydrate/low-fat diets and CHD is more ambiguous because high-carbohydrate diets induce dyslipidemia in certain individuals. Obesity among adults and children is now of epidemic proportions in the United States. High-fat diets leading to excessive energy intakes are strongly linked to the increasing obesity in the United States. However, the prevalence of obesity has increased during the same time period that dietary fat intake (both in absolute terms and as a percentage of total dietary energy) has decreased. These trends suggest that a concomitant decrease in total dietary energy and modifications of other lifestyle factors, such as physical activity, also need to be emphasized. Obesity is also an independent risk factor for the development of diabetes. The current availability of fat-modified foods offers the potential for dietary fat reduction and treatment of the comorbidities associated with diabetes. However, to date, few studies have documented the effectiveness of fat-modified foods as part of a weight loss regimen or in reduction in CHD risks among individuals with diabetes mellitus. The association between total dietary fat and cancer is still under debate. While there is some evidence demonstrating associations between dietary fat intake and cancers of the breast, prostate, and colon, there are serious methodologic issues, including the difficulty in differentiating the effects of dietary fat independent of total energy intake. Reported total fat and saturated fatty acid intakes as a percentage of total energy have been declining over the past 30 years in the United States. Despite this encouraging trend, the majority of individuals--regardless of age--do not report consuming a diet that meets the levels of fat and saturated fatty acids recommended by the Dietary Guidelines for Americans. On a relative basis, saturated fat intake has gone down less than has total fat intake. Individuals of all ages who report consuming a diet with < or = 30% of energy from fat consistently have lower energy intakes. Given the increasing rates of obesity in the United States at an earlier and earlier age, dietary fat reduction may be an effective part of an overall strategy to balance energy consumption with energy needs. In each of the age/gender groups reporting consumption of < or = 30% of energy from fat and less than 10% of energy from saturated fatty acids, fat-modified foods play a more important role in their diets than for people who are consuming higher levels of fat and saturated fat. The data are clear than fat-modified foods make a more significant contribution to diets of consumers with low-fat intakes. While one cannot argue cause and effect from the results presented, the patterns of fat-modified foods/low-fat intakes are consistent. The focus on overall diet quality is often lost in the national obsession with lowering fat inta

Within- and between-person variations in portion sizes of foods consumed by the Japanese population

There has been considerable controversy about the utility of asking separate questions on portion sizes in addition to items on consumption frequencies in food frequency questionnaires. One argument against this type of inquiry is that, for most foods, within-person variation of portion size is greater than between-person variation, making it difficult to characterize "usual" or long-term average serving sizes. The authors studied the relative effects of within- and between-person variances in portion sizes of 69 food items using three-day food record data collected from 335 Japanese men and women. Total variance in the portion size for each food was partitioned into within- and between-person components by analysis of variance. Although the ratios of within- to between-person variances in log(e)-transformed portion sizes were > 1.0 for the majority of foods (50 of 69 items, median = 1.7), they were smaller than or close to unity for subgroups of foods that were the major sources of nutrient variables of relevance to diet-cancer associations, such as total energy (rice, calcium (milk), sodium (pickled vegetables), and alcohol (beer, shochu, whiskey). These results indicate that the relative contributions of within- and between-person variations in portion size may vary among foods, and therefore investigators should consider the balance between the advantages and disadvantages of obtaining portion size data separately from intake frequencies when designing food frequency questionnaires.

Dietary fats and colon cancer: assessment of risk associated with specific fatty acids

There are many biological mechanisms whereby dietary fat and specific dietary fatty acids may alter risk of colon cancer in addition to their contribution to total energy intake. To evaluate these potential associations, we used detailed dietary intake data collected in a population-based study of 1,993 incident colon cancer cases and 2,410 controls conducted in 3 areas of the United States. The most commonly consumed fatty acid in the study population was oleic acid. One-third of dietary fats consumed came from additions to other foods at the table or from the preparation of other foods. After adjusting for total energy intake, physical activity and body size, neither total dietary fat nor specific fatty acids was associated with risk of colon cancer. However, among older women, fats from food preparation were associated with increased risk of colon cancer (OR 1.84, 95% CI 1.20-2.80), while fats from foods themselves or from additions to other foods were not. While dietary fats were not associated with colon cancer risk in the total population, subgroups of the population appeared to be at slightly greater risk if they consumed a high-fat diet. Women who consumed a diet high in mono-unsaturated fatty acids (MFAs) and poly-unsaturated fatty acids (PFAs) and who had a family history of colorectal cancer were at greater risk of colon cancer than those with similar intakes but without a family history of colorectal cancer. Similar associations with family history were noted among men diagnosed at younger ages for MFA, linolenic acid and 20-carbon PFA.