Lack of effect of a high-fiber cereal supplement on the recurrence of colorectal adenomas. Phoenix Colon Cancer Prevention Physicians' Network

Diet, Nutrition, and Cancer Prevention: The Postgenomic Era

The genomic era of human nutrition is upon us: the human genome and several plant genomes have been characterized, and genetically modified foods are now abundantly available in the marketplace. The link between diet and cancer is well established, and new genomic technologies have made possible the investigation of nutritional modulation of the carcinogenesis pathway with nutrients, micronutrients, and phytochemicals. Current study of nutrient-modulated carcinogenesis involves exploring the effect of nutrients on DNA damage and repair mechanisms; DNA methylation, which influences gene expression and cellular phenotypes; antioxidant rearranging and oxidative stress; target receptors and signal transduction pathways; cell cycle controls and check points; apoptosis; and antiangiogenic processes. With nutritional genomics, proteomics, and metabolomics, scientists are able to simultaneously elucidate the biological effects of dietary constituents on cell function and global gene expression. This generation of new knowledge on nutrient-gene interactions provides the justification for a research framework for diet and cancer prevention that is focused on identifying and developing new biomarkers as well as a novel and contemporary paradigm for dietary intervention.

Quantity and quality of dietary fat, carbohydrate, and fiber intake in the German EPIC cohorts

AIM

This evaluation aims to describe the quantity and quality of dietary fat, carbohydrate and fiber intake in both German cohorts participating in the European Prospective Investigation into Cancer and Nutrition (EPIC).

METHODS

Estimates are based on standardized computer-guided 24-hour dietary recalls from 1,078 women and 1,013 men in Heidelberg and 898 women and 1,032 men in Potsdam. In a subsample, plasma phospholipid (PL) fatty acids were analyzed as well.

RESULTS

Adjusted mean dietary intake estimates demonstrated that the contribution of fat as well as n-6 and n-3 polyunsaturated fatty acids (PUFA) to the total daily energy intake was higher in both women and men of EPIC-Potsdam compared to EPIC-Heidelberg. Surprisingly, the dietary n-6/n-3 PUFA ratio was lower in the Potsdam cohort. These results were confirmed by means of the PL fatty acid pattern. Besides the higher contribution of polysaccharides to total energy intake in EPIC-Heidelberg, women of the Heidelberg cohort revealed a significantly lower contribution of mono- and disaccharides (sucrose) to total energy intake. Although total fiber intake data were similar in both cohorts, analysis by food groups showed differences in dietary fiber intake originating from the food groups cereals, fruits and potatoes.

CONCLUSION

The results demonstrate distinct differences in the dietary fat, carbohydrate and fiber intake between both German EPIC cohorts, which contribute to the exposure variation in the whole of EPIC.

Position of the American Dietetic Association and Dietitians of Canada: vegetarian diets

It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Approximately 2.5% of adults in the United States and 4% of adults in Canada follow vegetarian diets. A vegetarian diet is defined as one that does not include meat, fish, or fowl. Interest in vegetarianism appears to be increasing, with many restaurants and college foodservices offering vegetarian meals routinely. Substantial growth in sales of foods attractive to vegetarians has occurred and these foods appear in many supermarkets. This position paper reviews the current scientific data related to key nutrients for vegetarians including protein, iron, zinc, calcium, vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and iodine. A vegetarian, including vegan, diet can meet current recommendations for all of these nutrients. In some cases, use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life-cycle including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fibre, magnesium, potassium, folate, antioxidants such as vitamins C and E, and phytochemicals. Vegetarians have been reported to have lower body mass indices than non-vegetarians, as well as lower rates of death from ischemic heart disease, lower blood cholesterol levels, lower blood pressure, and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer. While a number of federally funded and institutional feeding programs can accommodate vegetarians, few have foods suitable for vegans at this time. Because of the variability of dietary practices among vegetarians, individual assessment of dietary intakes of vegetarians is required. Dietetics professionals have a responsibility to support and encourage those who express an interest in consuming a vegetarian diet. They can play key roles in educating vegetarian clients about food sources of specific nutrients, food purchase and preparation, and any dietary modifications that may be necessary to meet individual needs. Menu planning for vegetarians can be simplified by use of a food guide that specifies food groups and serving sizes.

Calcium or resistant starch does not affect colonic epithelial cell proliferation throughout the colon in adenoma patients: a randomized controlled trial

Patients with a history of sporadic adenomas have increased epithelial cell proliferative activity, an intermediate risk marker for colorectal cancer. Reduction of proliferation by dietary intervention may reflect a decreased colorectal cancer risk. To evaluate whether calcium or resistant starch could reduce proliferative activity throughout the colon, we performed a randomized controlled trial in 111 sporadic adenoma patients. Patients received two placebos, 1 g of calcium + placebo, or 30 g of amylomaize (19 g of resistant starch) + placebo. After 2 mo, biopsies were collected from the cecum, transverse and sigmoid colon, and rectum during colonoscopy. Epithelial cell proliferation was determined by dividing the number of 5-bromo-2-deoxyuridine-labeled nuclei by the total number of nuclei x 100 (labeling index, LI). LI of luminal, mid, and basal compartments was determined. Twenty-five patients dropped out. In the remaining 86 patients (28 treated with placebo, 30 with calcium + placebo, and 28 with resistant starch + placebo), no difference was observed in total LI, the LI of the three compartments, or the crypt length in the four areas of the colorectum. Colonic epithelial cell proliferative activity throughout the colon of sporadic adenoma patients is not affected by supplementation with 1 g of calcium or 19 g of resistant starch.

Diet, individual responsiveness and cancer prevention

Dietary recommendations for the prevention of cancer have been based predominantly on large epidemiological studies of diet and lifestyle, conducted 20, and in some cases, almost 30 years ago. Government programs have been successful in educating the public about the benefits of eating fruits and vegetables, yet despite these efforts, Americans have become heavier, diabetes is more prevalent and general health indicators have not greatly improved. Individual response to dietary recommendations may be complicated by a variety of factors. Polymorphisms in genes related to drug activation and detoxification, folate metabolism, DNA repair, vitamin receptors and other cellular receptors could account for a lack of benefit at the level of the individual for consuming cancer preventive foods. Beyond consideration of genetic polymorphisms, the last half century has brought stark changes in lifestyle that depart from normal diurnal cycle and periodic fluctuations in food availability. Thus, modern times may be characterized as being constantly in a "feast" environment. The cellular consequences may be an increase in risk for several diseases including cancer.

Increased expression of thioredoxin-1 in human colorectal cancer is associated with decreased patient survival

Thioredoxin-1 is a redox protein that, when overexpressed, causes increased cancer-cell growth and inhibited apoptosis. Thioredoxin-1 expression has been reported to be increased in several human primary tumors, but its relationship to tumor progression and patient survival has not been established. We studied the expression of thioredoxin-1 as measured with immunohistochemical staining in paraffin-embedded human normal colonic mucosa, adenomatous polyps, and primary and metastatic colorectal cancer. Thioredoxin-1 expression was not increased in 12 colorectal adenomatous polyps, compared with 8 samples of normal colonic mucosa, but was significantly increased in 12 primary colorectal cancers (P <.01). Thioredoxin-1 expression was not significantly different in primary lymph-node metastases and the primary colorectal cancer. Using colorectal cancer samples from 37 subjects for whom survival data was available, we found that thioredoxin-1 expression increased with Dukes stage, although the association was not statistically significant (P =.077). We noted a significant association between thioredoxin-1 expression and patient survival (P =.004); higher score was associated with decreased survival. When adjusted for Dukes stage, thioredoxin-1 expression showed a statistically significant association with survival (P =.012). The work shows that increased thioredoxin-1 expression is a relatively late event in colorectal carcinogenesis and provides evidence in a small group of subjects with colorectal cancer of Dukes stages A through D that thioredoxin-1 expression may be an independent marker of patient prognosis.

Preventing cancer: dietary lifestyle or clinical intervention?

In Australia, colorectal, prostate and breast cancers are the most frequently occurring cancers in our society, a pattern that is quite different from that of underdeveloped countries. While diet is largely responsible for these differences, technological advances mean that the solutions can be viewed as systematic, financial, lifestyle or technological. They range from those that require self-discipline and care for personal well-being through to those that are seemingly a quick technological fix that will work in spite of an unhealthy lifestyle. There are three main approaches available for prevention of these cancers: dietary lifestyle, chemoprevention and screening. It has been estimated that the potential for prevention by a healthy dietary lifestyle is excellent and might reduce the burden of breast, prostate and colorectal cancer by 33-55%, 10-20% and 66-75%, respectively. This should be safe and inexpensive and have collateral benefit such as reduced cardiovascular disease and osteoporosis. But, population compliance with more plant-based, less calorie dense foods is uncertain, the most healthy are likely to be the most compliant and evidence for effectiveness when interventional programs are undertaken is disappointing. It is not clear how dependable the dietary approach would be where inherited genetic factors determine risk for one of these cancers. Chemoprevention, the administration of natural or synthetic agents that delay, slow down or inhibit the process of tumorigenesis, are still under development and study. Hormone receptor modulators for breast and derivatives of non-steroidal anti-inflammatory drugs for colorectal cancers seem to have most promise and may reduce tumour incidence or death by as much as 50%. These agents are simpler to comply with than changing dietary lifestyle and they are more potent, hence they may be of particular value in high-risk settings. But they are likely to be more costly and run the risk of adverse effects with few collateral benefits. Screening, or the testing of an individual for a disease when that individual does not have any symptoms or signs suggesting that the disease is present, aims to prevent or delay the development of the cancer. Screening impacts on mortality more so than on incidence, reducing colorectal cancer mortality in the range 15-60% and breast cancer mortality by 23-37%. Screening has the advantage of being effective in high-risk as well as average-risk groups and is an 'easy' solution for the person who elects not to follow a healthy dietary lifestyle. Nonetheless, it is expensive, demanding on resources, provides no collateral benefits and does not have the same potential to reduce incidence of disease as does the dietary approach. With these Western cancers, we are fortunate that there are options for prevention. At least choices are available and some will suite certain circumstances and personalities more than others.

Pronounced reduction in adenoma recurrence associated with aspirin use and a polymorphism in the ornithine decarboxylase gene

Most sporadic colon adenomas acquire mutations in the adenomatous polyposis coli gene (APC) and show defects in APC-dependent signaling. APC influences the expression of several genes, including the c-myc oncogene and its antagonist Mad1. Ornithine decarboxylase (ODC), the first enzyme in polyamine synthesis, is a transcriptional target of c-myc and a modifier of APC-dependent tumorigenesis. A single-nucleotide polymorphism exists in intron 1 of the human ODC gene, which lies between two myc-binding domains. This region is known to affect ODC transcription, but no data exist on the relationship of this polymorphism to risk of colorectal neoplasia in humans. We show that individuals homozygous for the minor ODC A-allele who reported using aspirin are approximately 0.10 times as likely to have an adenoma recurrence as non-aspirin users homozygous for the major G-allele. Mad1 selectively suppressed the activity of the ODC promoter containing the A-allele, but not the G-allele, in a human colon cancer-derived cell line (HT29). Aspirin (>or=10 microM) did not affect ODC allele-specific promoter activity but did activate polyamine catabolism and lower polyamine content in HT29 cells. We propose that the ODC polymorphism and aspirin act independently to reduce the risk of adenoma recurrence by suppressing synthesis and activating catabolism, respectively, of colonic mucosal polyamines. These findings confirm the hypothesis that the ODC polymorphism is a genetic marker for colon cancer risk, and support the use of ODC inhibitors and aspirin, or other nonsteroidal antiinflammatory drugs (NSAIDs), in combination as a strategy for colon cancer prevention.

Surveillance after positive and negative colonoscopy examinations: issues, yields, and use

As colorectal cancer screening gains acceptance by the public, the use of colonoscopy will increase. The frequency of surveillance examinations after detection of an adenoma is one of the largest contributors to the cost of colorectal cancer screening. Ten years after the publication of the landmark National Polyp Study, the issue of when to perform surveillance examinations and how often to expect advanced findings remains acute. Current guidelines for surveillance vary across specialty organizations. Individuals with advanced adenomas are at increased risk for recurrent advanced adenomas. The impact of multiple nonadvanced adenomas or a single nonadvanced adenoma on subsequent risk of an advanced adenoma or cancer is less clear. Still less is known about findings on repeat examinations after an initial negative examination, whether after colonoscopy or sigmoidoscopy. The yield after a negative examination is an important consideration in determining the recommended interval for screening colonoscopy. For example, the data supporting a 10-yr interval for screening colonoscopy is only indirect. What little we do know about the yield after negative examinations comes from selected, nonrepresentative populations. Of concern, evidence from several polyp prevention trials demonstrates higher yields for subsequent cancer than would be expected, despite a relatively high use of surveillance procedures in follow-up. Further population-based research on the frequency of use and yield of surveillance examinations is needed. Studies that examine the need and the needed timing of subsequent surveillance are essential to containing costs for screening as well as to informing the public better about what endoscopic screening can and cannot accomplish.

Position of the American Dietetic Association and Dietitians of Canada: Vegetarian diets

It is the position of the American Dietetic Association and Dietitians of Canada that appropriately planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. Approximately 2.5% of adults in the United States and 4% of adults in Canada follow vegetarian diets. A vegetarian diet is defined as one that does not include meat, fish, or fowl. Interest in vegetarianism appears to be increasing, with many restaurants and college foodservices offering vegetarian meals routinely. Substantial growth in sales of foods attractive to vegetarians has occurred, and these foods appear in many supermarkets. This position paper reviews the current scientific data related to key nutrients for vegetarians, including protein, iron, zinc, calcium, vitamin D, riboflavin, vitamin B-12, vitamin A, n-3 fatty acids, and iodine. A vegetarian, including vegan, diet can meet current recommendations for all of these nutrients. In some cases, use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Well-planned vegan and other types of vegetarian diets are appropriate for all stages of the life cycle, including during pregnancy, lactation, infancy, childhood, and adolescence. Vegetarian diets offer a number of nutritional benefits, including lower levels of saturated fat, cholesterol, and animal protein as well as higher levels of carbohydrates, fiber, magnesium, potassium, folate, and antioxidants such as vitamins C and E and phytochemicals. Vegetarians have been reported to have lower body mass indices than nonvegetarians, as well as lower rates of death from ischemic heart disease; vegetarians also show lower blood cholesterol levels; lower blood pressure; and lower rates of hypertension, type 2 diabetes, and prostate and colon cancer. Although a number of federally funded and institutional feeding programs can accommodate vegetarians, few have foods suitable for vegans at this time. Because of the variability of dietary practices among vegetarians, individual assessment of dietary intakes of vegetarians is required. Dietetics professionals have a responsibility to support and encourage those who express an interest in consuming a vegetarian diet. They can play key roles in educating vegetarian clients about food sources of specific nutrients, food purchase and preparation, and any dietary modifications that may be necessary to meet individual needs. Menu planning for vegetarians can be simplified by use of a food guide that specifies food groups and serving sizes.

Dietary fibre in food and protection against colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC): an observational study

BACKGROUND

Dietary fibre is thought to protect against colorectal cancer but this view has been challenged by recent prospective and intervention studies that showed no protective effect.

METHODS

We prospectively examined the association between dietary fibre intake and incidence of colorectal cancer in 519978 individuals aged 25-70 years taking part in the EPIC study, recruited from ten European countries. Participants completed a dietary questionnaire in 1992-98 and were followed up for cancer incidence. Relative risk estimates were obtained from fibre intake, categorised by sex-specific, cohort-wide quintiles, and from linear models relating the hazard ratio to fibre intake expressed as a continuous variable.

FINDINGS

Follow-up consisted of 1939011 person-years, and data for 1065 reported cases of colorectal cancer were included in the analysis. Dietary fibre in foods was inversely related to incidence of large bowel cancer (adjusted relative risk 0.75 [95% CI 0.59-0.95] for the highest versus lowest quintile of intake), the protective effect being greatest for the left side of the colon, and least for the rectum. After calibration with more detailed dietary data, the adjusted relative risk for the highest versus lowest quintile of fibre from food intake was 0.58 (0.41-0.85). No food source of fibre was significantly more protective than others, and non-food supplement sources of fibre were not investigated.

INTERPRETATION

In populations with low average intake of dietary fibre, an approximate doubling of total fibre intake from foods could reduce the risk of colorectal cancer by 40%.

Dietary fibre and colorectal adenoma in a colorectal cancer early detection programme

BACKGROUND

Although dietary fibre has been reported to have no association with colorectal adenoma and cancer, in some studies this topic remains controversial.

METHODS

We used a 137-item food frequency questionnaire to assess the relation of fibre intake and frequency of colorectal adenoma. The study was done within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a randomised controlled trial designed to investigate methods for early detection of cancer. In our analysis, we compared fibre intake of 33971 participants who were sigmoidoscopy-negative for polyps, with 3591 cases with at least one histologically verified adenoma in the distal large bowel (ie, descending colon, sigmoid colon, or rectum). Odds ratios were estimated by logistic regression analysis.

FINDINGS

High intakes of dietary fibre were associated with a lower risk of colorectal adenoma, after adjustment for potential dietary and non-dietary risk factors. Participants in the highest quintile of dietary fibre intake had a 27% (95% CI 14-38, p(trend)=0.002) lower risk of adenoma than those in the lowest quintile. The inverse association was strongest for fibre from grains and cereals and from fruits. Risks were similar for advanced and non-advanced adenoma. Risk of rectal adenoma was not significantly associated with fibre intake.

INTERPRETATION

Dietary fibre, particularly from grains, cereals, and fruits, was associated with decreased risk of distal colon adenoma.

Nutrition and diet in the development of gastrointestinal cancer

Diet plays a role in the prevention and development of gastrointestinal cancers. The majority of available research consists of case-control studies, but the number of clinical trials is growing. The dietary recommendations to reduce gastrointestinal cancer risk include lowering total energy, fat, and saturated fat intake; avoidance of grilled and smoked foods; avoidance of alcohol; and increasing intake of fruits, vegetables, and fiber. Studies of esophageal cancer support these dietary approaches, with the exception of dietary fat reduction and increased green tea intake. For gastric cancer, consuming additional fruits and vegetables, including those high in ascorbic acid, may reduce risk, and the capacity for diet to alter Helicobacter pylori infection should be explored. Recent interventional trials do not support a role for high-fiber or low-fat diets in reducing development of colon adenomas, although the evidence does not rule out efficacy at earlier stages of disease. Finally, the evidence for a relationship between pancreatic cancer and diet remains sparse and warrants additional investigation.

Dietary fibre and risk of colorectal cancer in the Breast Cancer Detection Demonstration Project (BCDDP) follow-up cohort

BACKGROUND

The hypothesis that increased intake of dietary fibre lowers the risk of colorectal cancer (CRC) has recently been weakened by results from cohort and intervention studies that did not detect such an association. We investigated the association between dietary fibre intake and risk of CRC in a cohort of women that prospectively answered a food frequency questionnaire (FFQ).

METHODS

We studied 45 491 women in the Breast Cancer Detection Demonstration Project (BCDDP) follow-up cohort. A 62-item FFQ was administered from 1987 and 1989 to assess dietary intake. Participants received follow-up questionnaires (in 1992-1995 and 1995-1998) on which they reported incident cancers. Cases were also identified through searches of the National Death Index and state cancer registries. Cox proportional hazard regression was used to generate risk ratios and 95% CI for quintiles of total fibre intake and fibre subtypes.

RESULTS

During a mean follow-up time of 8.5 years we identified 487 colorectal cancer cases. The 10th and 90th percentiles of dietary fibre intake were 5.4 g and 18.2 g respectively. For total fibre we observed no association with colorectal cancer (fifth versus first quintile, RR = 0.94, 95% CI: 0.71-1.23). Analyses by subgroup of fibre and by anatomical subsite did not reveal any stronger inverse associations.

CONCLUSIONS

Within a cohort of older women characterized by a relatively low fibre intake, there was little evidence that dietary fibre intake lowers the risk of colorectal cancer.

Vegetables and fruit intake and cancer mortality in the Hiroshima/Nagasaki Life Span Study

The association between green-yellow vegetables and fruit consumption and risk of cancer death was investigated in a prospective study of 38 540 men and women who were atomic-bomb survivors in Hiroshima and Nagasaki, Japan. Study participants completed a dietary questionnaire in 1980-1981 and were followed-up for cancer deaths until March 1998, during which time 3136 cancer deaths were identified. Daily or almost daily fruit consumption was associated with a significant 12% reduction in total cancer mortality (RR=0.88; 95% CI, 0.80-0.96 for daily intake compared with intake once per week or less). Daily or almost daily green-yellow vegetables consumption was associated with a marginally significant 8% reduction in total cancer mortality (0.92; 0.94-1.01). Green-yellow vegetables consumption was associated with a significant reduction in liver cancer mortality (0.75; 0.60-0.95). Fruit consumption was associated with a significantly reduced risk of stomach cancer and lung cancer mortality (0.80; 0.65-0.98). Green-yellow vegetables and fruit consumption was associated with a reduction in oesophageal cancer, but these associations were not statistically significant. Neither green-yellow vegetables nor fruit consumption was associated with colorectal cancer or breast cancer mortality. These results support the evidence that daily consumption of fruit and vegetables reduces the risk of total cancer, and specifically cancers of the stomach, liver, and lung.

A randomized trial of aspirin to prevent colorectal adenomas in patients with previous colorectal cancer

BACKGROUND

Experimental studies in animals and observational studies in humans suggest that regular aspirin use may decrease the risk of colorectal adenomas, the precursors to most colorectal cancers.

METHODS

We conducted a randomized, double-blind trial to determine the effect of aspirin on the incidence of colorectal adenomas. We randomly assigned 635 patients with previous colorectal cancer to receive either 325 mg of aspirin per day or placebo. We determined the proportion of patients with adenomas, the number of recurrent adenomas, and the time to the development of adenoma between randomization and subsequent colonoscopic examinations. Relative risks were adjusted for age, sex, cancer stage, the number of colonoscopic examinations, and the time to a first colonoscopy. The study was terminated early by an independent data and safety monitoring board when statistically significant results were reported during a planned interim analysis.

RESULTS

A total of 517 randomized patients had at least one colonoscopic examination a median of 12.8 months after randomization. One or more adenomas were found in 17 percent of patients in the aspirin group and 27 percent of patients in the placebo group (P=0.004). The mean (+/-SD) number of adenomas was lower in the aspirin group than the placebo group (0.30+/-0.87 vs. 0.49+/-0.99, P=0.003 by the Wilcoxon test). The adjusted relative risk of any recurrent adenoma in the aspirin group, as compared with the placebo group, was 0.65 (95 percent confidence interval, 0.46 to 0.91). The time to the detection of a first adenoma was longer in the aspirin group than in the placebo group (hazard ratio for the detection of a new polyp, 0.64; 95 percent confidence interval, 0.43 to 0.94; P=0.022).

CONCLUSIONS

Daily use of aspirin is associated with a significant reduction in the incidence of colorectal adenomas in patients with previous colorectal cancer.

Primary and secondary prevention of colorectal cancer

Colorectal cancer is the third leading cause of cancer deaths in the United States. Because of the nature and the progression of the disease, it is highly preventable and suitable for screening. Yet the American Cancer Society estimates included over 100,000 cases of new occurrence of colorectal cancer and over 50,000 deaths in the year 2002. The continued high colorectal cancer mortality rate is due to the under utilization of screening tests. This review will explore the barriers to low screening test use. Implications for healthcare professionals on how to increase the general populations' awareness of colorectal cancer and ways to increase adherence to screening by integrating theories of the Health Belief Model will be discussed. The current research and literature about primary prevention focused on modifiable risk factors and chemoprevention will be examined. Secondary prevention, however, will be the key to help reduce the mortality and morbidity of colorectal cancer. The current screening guidelines will be reviewed as well. It is possible to increase screening rate by modifying and influencing patients' perceived cancer risk, and by educating and training healthcare providers.

Nondigestible carbohydrates in the diets of infants and young children: a commentary by the ESPGHAN Committee on Nutrition

The consumption of nondigestible carbohydrates is perceived as beneficial by health professionals and the general public, but the translation of this information into dietary practice, public health recommendations, and regulatory policy has proved difficult. Nondigestible carbohydrates are a heterogeneous entity, and their definition is problematic. Without a means to characterize the dietary components associated with particular health benefits, specific attributions of these cannot be made. Food labeling for "fiber" constituents can be given only in a general context, and the development of health policy, dietary advice, and education, and informed public understanding of nondigestible carbohydrates are limited. There have, however, been several important developments in our thinking about nondigestible carbohydrates during the past few years. The concept of fiber has expanded to include a range of nondigestible carbohydrates. Their fermentation, fate, and effects in the colon have become a defining characteristic; human milk, hitherto regarded as devoid of nondigestible carbohydrates, is now recognized as a source for infants, and the inclusion of nondigestible carbohydrates in the diet has been promoted for their "prebiotic" effects. Therefore, a review of the importance of nondigestible carbohydrates in the diets of infants and young children is timely. The aims of this commentary are to clarify the current definitions of nondigestible carbohydrates, to review published evidence for their biochemical, physiologic, nutritional, and clinical effects, and to discuss issues involved in defining dietary guidelines for infants and young children.

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

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

Fecal levels of short-chain fatty acids and bile acids as determinants of colonic mucosal cell proliferation in humans

We studied the correlation between fecal levels of short-chain fatty acids (SCFA), bile acids (BA), and colonic mucosal proliferation in humans on a free diet. Subjects [n = 43: 27 men and 16 women; 61 +/- 7 and 59 +/- 6 (SE) yr old, respectively] were outpatients who previously underwent resection of at least two sporadic colon polyps. Mucosal proliferation was determined by [3H]thymidine incorporation in vitro in three colorectal biopsies obtained without cathartics and was expressed as labeling index (LI). BA were analyzed in feces by mass spectrometry and SCFA by gas chromatography. We found that increasing levels of BA in feces did not correlate with higher LI. On the contrary, higher levels of SCFA were significantly associated with lower LI in the colonic mucosa (P for trend = 0.02). In conclusion, in humans on a free diet, intestinal proliferation seems to be regulated by the levels of SCFA in feces and not by BA. Because a lower intestinal proliferation is associated with a decreased colon cancer risk, treatments or diets that increase colonic levels of SCFA might be beneficial for colonic mucosa.

Diet and cancer: where are we and where are we going?

Many studies have shown that overall dietary patterns, dietary components consumed, or mode of food preparation are all possibly relevant in either reducing or increasing the risk of cancer in animals or man. Yet, dietary intervention studies, stemming from laboratory and epidemiological observational studies have often failed to demonstrate the anticipated protection against cancer. One possible explanation for the discrepancy between the results of various observational and experimental chemo-prevention studies is the lack of control for biological diversity of the participants of these studies. It is suggested that future epidemiological studies provide evidence stratified by status of major metabolic polymorphisms pertinent to the study subject, and that future intervention studies take these differences into account in the design and analysis phases.

Nutrient intakes and adenocarcinoma of the esophagus and distal stomach

We studied the relationship between nutrient intakes and adenocarcinoma of the esophagus and distal stomach among 124 esophageal adenocarcinoma cases, 124 distal stomach cancer cases, and 449 controls in a population-based case-control study in eastern Nebraska. The residual method was used to adjust nutrient intake quartiles or tertiles for energy intake. We observed significant inverse associations with risk of esophageal adenocarcinoma for dietary intakes of total vitamin A [highest vs. lowest quartile, multivariate odds ratio (OR) = 0.5, P for trend = 0.05], beta-cryptoxanthin (OR = 0.5, P = 0.05), riboflavin (OR = 0.5, P = 0.01), folate (OR = 0.5, P = 0.03), zinc (OR = 0.5, P = 0.05), dietary fiber (OR = 0.5, P = 0.05), protein (OR = 0.5, P = 0.02), and carbohydrate (OR = 0.4, P = 0.02). For distal stomach cancer, only vitamin C (OR = 0.6, P = 0.04), dietary fiber (OR = 0.4, P = 0.007), and carbohydrate (OR = 0.4, P = 0.004) were inversely associated with risk. Our analyses showed significant interaction between dietary fat intake, but not intakes of other nutrients, and respondent type for both cancer sites. Subgroup analyses among self-respondents revealed positive associations between saturated fat intake and risk of esophageal adenocarcinoma (OR = 1.0, 4.1, and 4.6 for intake tertiles, P for trend = 0.02) and risk of distal stomach cancer (OR = 1.0, 1.2, and 3.6, P = 0.03). However, no such associations were found among proxy respondents. Our data suggest that greater intake of dietary fiber, certain carotenoids, and vitamins may decrease the risk of esophageal adenocarcinoma, whereas greater intake of saturated fat may increase the risk of esophageal adenocarcinoma and distal stomach cancer.

Screening intervals for colonic neoplasia

Surveillance examinations after detection of an adenoma are one of the largest contributors to the cost of colorectal cancer screening. Screening colonoscopy, beginning at the age of 50 years, is increasing in frequency and becoming part of the zeitgeist. Given the high rate of adenomatous polyp detection on colonoscopy, the amount of time spent and costs consumed by surveillance are likely to grow to significant levels in the coming years. Guidelines for surveillance examinations vary across specialty organizations. Individuals with advanced adenomas are at increased risk for recurrent advanced adenomas. The impact of multiple nonadvanced adenomas or a single nonadvanced adenoma on subsequent risk of an advanced adenoma or cancer is less clear. Recommended surveillance after colorectal cancer has greater consensus, but concerns remain. Studies that predict the need and the needed timing of surveillance remain an important research priority.

Modifiable risk factors for colon cancer

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

Diet quality and major chronic disease risk in men and women: moving toward improved dietary guidance

BACKGROUND

Adherence to the Dietary Guidelines for Americans, measured with the US Department of Agriculture Healthy Eating Index (HEI), was associated with only a small reduction in major chronic disease risk. Research suggests that greater reductions in risk are possible with more specific guidance.

OBJECTIVE

We evaluated whether 2 alternate measures of diet quality, the Alternate Healthy Eating Index (AHEI) and the Recommended Food Score (RFS), would predict chronic disease risk reduction more effectively than did the HEI.

DESIGN

A total of 38 615 men from the Health Professional's Follow-up Study and 67 271 women from the Nurses' Health Study completed dietary questionnaires. Major chronic disease was defined as the initial occurrence of cardiovascular disease (CVD), cancer, or nontraumatic death during 8-12 y of follow-up.

RESULTS

High AHEI scores were associated with significant reductions in risk of major chronic disease in men [multivariate relative risk (RR): 0.80; 95% CI: 0.71, 0.91] and in women (RR: 0.89; 95% CI: 0.82, 0.96) when comparing the highest and lowest quintiles. Reductions in risk were particularly strong for CVD in men (RR: 0.61; 95% CI: 0.49, 0.75) and in women (RR: 0.72; 95% CI: 0.60, 0.86). In men but not in women, the RFS predicted risk of major chronic disease (RR: 0.93; 95% CI: 0.83, 1.04) and CVD (RR: 0.77; 95% CI: 0.64, 0.93).

CONCLUSIONS

The AHEI predicted chronic disease risk better than did the RFS (or the HEI, in our previous research) primarily because of a strong inverse association with CVD. Dietary guidelines can be improved by providing more specific and comprehensive advice.

Research strategies and the use of nutrient biomarkers in studies of diet and chronic disease

OBJECTIVE

To provide an account of the state of diet and chronic disease research designs and methods; to discuss the role and potential of aggregate and analytical observational studies and randomised controlled intervention trials; and to propose strategies for strengthening each type of study, with particular emphasis on the use of nutrient biomarkers in cohort study settings.

DESIGN

Observations from diet and disease studies conducted over the past 25 years are used to identify the strengths and weaknesses of various study designs that have been used to associate nutrient consumption with chronic disease risk. It is argued that a varied research programme, employing multiple study designs, is needed in response to the widely different biases and constraints that attend aggregate and analytical epidemiological studies and controlled intervention trials. Study design modifications are considered that may be able to enhance the reliability of aggregate and analytical nutritional epidemiological studies. Specifically, the potential of nutrient biomarker measurements that provide an objective assessment of nutrient consumption to enhance analytical study reliability is emphasised. A statistical model for combining nutrient biomarker data with self-report nutrient consumption estimates is described, and related ongoing work on odds ratio parameter estimation is outlined briefly. Finally, a recently completed nutritional biomarker study among 102 postmenopausal women in Seattle is mentioned. The statistical model will be applied to biomarker data on energy expenditure, urinary nitrogen, selected blood fatty acid measurements and various blood micronutrient concentrations, and food frequency self-report data, to identify study subject characteristics, such as body mass, age or socio-economic status, that may be associated with the measurement properties of food frequency nutrient consumption estimates. This information will be crucial for the design of a potential larger nutrient biomarker study within the cohort study component of the Women's Health Initiative.

SETTING AND SUBJECTS

The methodology under study is expected to be pertinent to a wide variety of diet and chronic disease association studies in the general population. Ongoing work focuses on statistical methods developed using computer simulations motivated by studies of dietary fat in relation to breast and colon cancer among post-menopausal women, and ongoing pilot studies to be described in detail elsewhere, involving post-menopausal women living in the Seattle area.

RESULTS AND CONCLUSION

A varied research programme appears to be needed to make progress in the challenging diet and chronic disease research area. Such progress may include aggregate studies of diet and chronic disease that include sample surveys in diverse population groups world-wide, analytical epidemiological studies that use nutrient biomarker data to calibrate self-report nutrient consumption estimates, and randomised controlled intervention trials that arise from an enhanced infrastructure for intervention development. New innovative designs, models and methodologies are needed for each such research setting.

Chemoprevention of colorectal cancer: problems, progress, and prospects

Chemoprevention holds great promise as a complement to traditional CRC screening and treatment. Effective chemopreventive agents might improve patient outcomes by reducing the number of missed lesions, the morbidity associated with their identification and treatment, and their malignant potential. In addition, chemoprevention may reduce neoplastic potential simultaneously in several organs and improve clinical outcomes for persons at risk for cancers at multiple sites (e.g., colorectal and extracolonic cancers in HNPCC cohorts). Complex molecular circuits underlie the disease mosaic that is associated with aging. Several of these diseases share common mechanisms against which preventive interventions appear to be effective, such as NSAIDs for colorectal neoplasia and neurodegenerative disease, and statins for cardiovascular disease and colorectal neoplasia. Understanding these mechanisms and effects could raise prevention science to an entirely new level. The number of trials that are investigating chemopreventives against CR neoplasia is relatively small; if these agents live up to a fraction of their promise, the public health impact may be great (see Table 6).

Epidemiology and prevention of colorectal cancer

CRC, the second-leading cause of cancer death in the United States, is a highly preventable disease. Ironically, available and effective screening technologies are not consistently applied, even as new ones are developed. This discordance between preventive opportunity and practice conveys a sobering message regarding nontechnologic issues that must be addressed if the promise of CRC prevention is to be realized. Our response to this message will determine the public health impact of cancer prevention. In the 1980s, cancer chemoprevention was regarded as scientific speculation. Within the last decade, however, cancer has been recognized as a late, nonobligate stage of carcinogenesis, a chronic process that provides time and targets for preventive intervention. Further advances are emerging out of rigorous clinical testing, which remains the limiting factor in transforming ingenious concepts into useful tools for the prevention of CRC. The challenges and rewards of participation in chemoprevention research--both as patients and health care providers-have never been greater.

Colorectal polyps in the elderly: what should be done?

Colorectal cancer is an important cause of morbidity and mortality among Western nations, and is more common in the elderly than in younger individuals. With the general acceptance of the adenoma-carcinoma sequence, the current consideration is that colorectal cancer is preventable if all adenomas are removed before they have the chance to progress to cancer. To that end, physicians should now advocate screening for colorectal cancer and through this effort a large number of patients with adenomatous polyps will be discovered. It is important to understand the strategy in dealing with this growing population of patients with adenomas. After an initial polypectomy, patients with adenomas should be entered into a surveillance program to detect and remove recurrent adenomas. Recommended surveillance intervals are shorter for patients with a family history of colorectal cancer, those with multiple adenomas (>2), large adenomas (> or = 1cm), or those whose adenomas have high-grade dysplasia, villous architecture, or that are cancerous. Effective chemoprevention would be a potential method of lengthening colonoscopic surveillance intervals. Unfortunately, no treatment has been found to be effective enough to alter our current surveillance practice. The only recommendation that can be made at this time for those patients with a history of colonic adenomas is to add 3 g/day of calcium carbonate to their diet, though its effect on adenoma recurrence is modest.

The effect of diet on risk of cancer

Diet-related factors are thought to account for about 30% of cancers in developed countries. Obesity increases the risk of cancers in the oesophagus, colorectum, breast, endometrium, and kidney. Alcohol causes cancers of the oral cavity, pharynx, larynx, oesophagus, and liver, and causes a small increase in the risk of breast cancer. Adequate intakes of fruit and vegetables probably lower the risk for several types of cancer, especially cancers of the gastrointestinal tract. The importance of other factors, including meat, fibre, and vitamins, is not yet clear. Prudent advice is to eat a varied diet including plenty of fruit, vegetables, and cereals to maintain a healthy bodyweight with the help of regular physical activity and to restrict consumption of alcohol.

Fibres and colorectal cancer: should we change our dietary advice on prevention?

Evidence from epidemiological studies overwhelmingly indicates that fruit, vegetables and cereals prevent cancer at a wide range of sites in the body, not just the large bowel. However, recent important papers have shown that an intervention diet rich in fruit, vegetables and fibre failed to decrease the risk of new colorectal adenoma formation. The adenoma-cancer sequence and the role of diet are discussed in the light of these new findings.

The role of nutrition and nutrients in the prevention of chronic diseases

The nutritional factors that increase risk of heart disease, many cancers, and diabetes are identical. Controlling body weight, being physically active, limiting intake of saturated fats, and eating ample amount of fruits and vegetables can all reduce the risk for many different chronic diseases. Physicians have many opportunities to assist their patients in reducing their nutritional risk of chronic diseases.

A critical review of the toxicological effects of carrageenan and processed eucheuma seaweed on the gastrointestinal tract

Carrageenan is a high-molecular-weight, strongly anionic polymer derived from several species of red seaweed that is used for the textural stabilization of foods. Processed Eucheuma Seaweed (PES) is a form of carrageenan with a higher cellulose content. Food-grade carrageenan has a weight average molecular weight greater than 100,000 Da, with a low percentage of smaller fragments. Carrageenan is not degraded to any extent in the gastrointestinal tract and is not absorbed from it in species examined, such as rodents, dogs, and non-human primates. Systemically administered carrageenan has been reported to have a variety of effects, particularly on the immune system, but these are not pertinent to orally administered carrageenan. The substance poligeenan (formerly referred to as degraded carrageenan) is not a food additive. It exhibits toxicological properties at high doses that do not occur with the food additive carrageenan. In-long term bioassays, carrageenan has not been found to be carcinogenic, and there is no credible evidence supporting a carcinogenic effect or a tumor-promoting effect on the colon in rodents. Also, like many dietary fibers, there is significant cecal enlargement in rodents when it is administered at high doses, but this does not appear to be associated with any toxicological consequences to the rodent. Many toxicological studies on carrageenan have involved administration at doses in excess of today's standards for dietary feeding levels in bioassays, and they are orders of magnitude in excess of those to which humans are exposed. Previous reviews of carrageenan and PES by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives (JECFA) have recommended a group allowable daily intake (ADI) of "not specified". The lack of carcinogenic, genotoxic, or tumor-promoting activity with carrageenan strongly supports continuing such an ADI, and JECFA, during its most recent review in 2001, continued this recommendation. The various toxicological studies related to orally administered food-grade carrageenan are summarized along with a brief discussion of critical factors in intestinal carcinogenesis.

Primary prevention: phytoprevention and chemoprevention of colorectal cancer

Considering the various stages of carcinogenesis and the numerous tumor types and available chemoprevention agents, knowledge of the etiology and the type of cancer to be treated, or possibly prevented, and understanding of the mechanisms by which agents exert their chemoprevention benefits may provide for improved strategy in designing therapeutic regimens. Because cancer usually develops over a 10- to 20-year period, it may be necessary for some agents to be provided before or early in the initiation steps of carcinogenesis to have beneficial effects. On the other hand, some agents may be more suitable for CRC prevention if provided at a later stage of carcinogenesis. Gene array, genomics, and proteomics are useful tools in advancing our understanding of the molecular events involved in carcinogenesis and in identifying markers of risk and surrogate end-points for colorectal cancer progression. These techniques may also serve for screening, identifying, and providing treatment targets for high-risk patients populations. Treatment could be developed depending on a patient's individual needs and genomic tumor profile. Clinical markers and surrogate end-points should be considered, together with molecular measurements, to more accurately assess risk. NSAIDs and COXIBs are clinically recognized as chemoprevention agents, and clinical trials evaluating their efficacy are ongoing. Treatment protocols, including dose and timing, remain to be determined, however. DFMO may best be used in combination with other chemoprevention agents. Dietary fiber and calcium supplements, as part of an overall low-fat diet, may decrease CRC risk. Long-term compliance with this regimen may be necessary to effect a beneficial outcome. Folate holds promise but needs further investigation, especially because its beneficial effects may depend on cancer type. Phytochemicals have been identified as strong candidates for use as agents to prevent colorectal cancer in cell culture and in rodent models of carcinogenesis. Their potential as chemoprevention agents must be demonstrated in clinical trials. In vitro and animal studies indicated that combination therapy may be a promising strategy over the monotherapy approach; clinical trials addressing the safety and efficacy of some combinations (DFMO/sulindac, fiber/calcium) are underway. The gastrointestinal tract and other organs are constantly exposed to a mixture of potentially toxic compounds and molecules considered favorable to health. Homeostasis between stress-mediated by toxic compounds and defensive mechanisms, is key for the maintenance of health and the prevention of disease. Whereas aggressive pharmacologic treatment may be necessary for patients at high risk for cancer, dietary supplements may be useful for populations at normal risk. The message for cancer prevention in the general population may well remain: keep a balanced healthy diet, eating a variety from all food groups, as part of a healthy lifestyle that includes moderate exercise.

A diet containing alpha-cellulose and fish oil reduces aberrant crypt foci formation and modulates other possible markers for colon cancer risk in azoxymethane-treated rats

There is a need for better understanding of the roles of dietary fats and fibers in colon cancer risk. We examined the effect of different dietary fiber and fat sources on an azoxymethane (AOM)-induced colon cancer in rats. In a 2 x 3 factorial design, rats were fed a semipurified diet containing soy-derived fiber (Fibrim), alpha-cellulose (Solkafloc) or resistant starch (RS; Hi-maize) at 10 g dietary fiber/100 g diet, combined with fish oil (FO) or sunflower seed oil (SSO) at 10 g/100 g diet, and lard added to all diets at 10 g/100 g, to provide a total of 20 g mixed fat/100 g diet. Sprague-Dawley rats (28 d of age) consumed diets for 4 wk and then two doses of AOM (15 mg/kg body) were administered 1 wk apart by subcutaneous injection. Rats were killed after 13 wk of consuming experimental diets. Colons were fixed in formalin and aberrant crypt foci (ACF) were quantified after staining. ACF counts were higher (+66%, P < 0.01) in rats fed SSO and RS, than in those fed alpha-cellulose and FO. Rats fed FO had 19% fewer ACF than those fed SSO (P < 0.05). alpha-Cellulose was associated with the highest cecal butyrate concentration (P < 0.001), the highest beta-glucuronidase specific activity (P < 0.001) and the lowest cecal water cytotoxicity (P < 0.001) relative to soy fiber- and RS-fed rats. There were inverse correlations between the number of ACF and cecal butyrate concentration (r = -0.33, P < 0.05) and between cecal water cytotoxicity and beta-glucuronidase activity (r = -0.70, P < 0.001). The greatest protection was associated with alpha-cellulose as the fiber source and FO as the fat source as measured by colon ACF numbers in rats.

Position of the American Dietetic Association: health implications of dietary fiber

Dietary fiber consists of the structural and storage polysaccharides and lignin in plants that are not digested in the human stomach and small intestine. A wealth of information supports the American Dietetic Association position that the public should consume adequate amounts of dietary fiber from a variety of plant foods. Recommended intakes, 20-35 g/day for healthy adults and age plus 5 g/day for children, are not being met, because intakes of good sources of dietary fiber, fruits, vegetables, whole and high-fiber grain products, and legumes are low. Consumption of dietary fibers that are viscous lowers blood cholesterol levels and helps to normalize blood glucose and insulin levels, making these kinds of fibers part of the dietary plans to treat cardiovascular disease and type 2 diabetes. Fibers that are incompletely or slowly fermented by microflora in the large intestine promote normal laxation and are integral components of diet plans to treat constipation and prevent the development of diverticulosis and diverticulitis. A diet adequate in fiber-containing foods is also usually rich in micronutrients and nonnutritive ingredients that have additional health benefits. It is unclear why several recently published clinical trials with dietary fiber intervention failed to show a reduction in colon polyps. Nonetheless, a fiber-rich diet is associated with a lower risk of colon cancer. A fiber-rich meal is processed more slowly, which promotes earlier satiety, and is frequently less calorically dense and lower in fat and added sugars. All of these characteristics are features of a dietary pattern to treat and prevent obesity. Appropriate kinds and amounts of dietary fiber for the critically ill and the very old have not been clearly delineated; both may need nonfood sources of fiber. Many factors confound observations of gastrointestinal function in the critically ill, and the kinds of fiber that would promote normal small and large intestinal function are usually not in a form suitable for the critically ill. Maintenance of body weight in the inactive older adult is accomplished in part by decreasing food intake. Even with a fiber-rich diet, a supplement may be needed to bring fiber intakes into a range adequate to prevent constipation. By increasing variety in the daily food pattern, the dietetics professional can help most healthy children and adults achieve adequate dietary fiber intakes.

Diet and colorectal cancer: an investigation of the lectin/galactose hypothesis

BACKGROUND & AIMS

Mucosal expression of terminal unsubstituted galactose is increased in colon cancer and precancer and allows interaction with mitogenic galactose-binding lectins of dietary or microbial origin. This study tests the hypothesis that galactose, which is variably plentiful in fruit and vegetable but not cereal fibers, might prevent cancer by binding and inhibiting such lectins.

METHODS

Colorectal cancer cases (512) and controls (512) were matched for age, sex, primary care practitioner, and postal code. A 160-item food-frequency questionnaire was used to estimate their usual pre-illness (6 months previous) diet, aspirin intake, and exercise.

RESULTS

Neither cereal fiber nor fruit and vegetable fiber were protective when assessed by univariate analysis, whereas dietary fiber galactose content showed a dose-related protective effect (odds ratio [OR] highest quartile/lowest quartile, 0.67; confidence interval [CI], 0.47-0.95) that remained protective when adjusted for energy, red meat, alcohol, calcium, protein and fat intake, regular aspirin usage, and exercise. Intake of nonlegume green vegetables, assessed because of the high lectin content of legumes, was also protective (OR, 0.54; CI, 0.35-0.81), but this was not independent of galactose. Protective effects of exercise and regular daily aspirin consumption and harmful effects of high energy consumption and high red meat intake were confirmed.

CONCLUSIONS

The protective effect of fruit and vegetable fibers may be related to their galactose content. This provides further evidence that the association between diet and colon cancer is mediated via specific food components and may explain the discrepant results of studies addressing the protective effects of fiber.

The long-term effect of dietary advice in men with coronary disease: follow-up of the Diet and Reinfarction trial (DART)

OBJECTIVE

To assess the long-term effect of dietary advice on diet and mortality after a randomised trial of men with a recent history of myocardial infarction.

DESIGN

Questionnaire survey and mortality follow-up after a trial of dietary advice.

SETTING

Twenty-one hospitals in south Wales and south-west England.

SUBJECTS

Former participants in the Diet and Reinfarction Trial.

MAIN OUTCOME MEASURES

Current fish intake and cereal fibre intake. All-cause mortality, stroke mortality and coronary mortality.

RESULTS

By February 2000, after 21147 person years of follow-up, 1083 (53%) of the men had died. Completed questionnaires were obtained from 879 (85%) of the 1030 men alive at the beginning of 1999. Relative increases in fish and fibre intake were still present at 10 y but were much smaller. The early reduction in all-cause mortality observed in those given fish advice (unadjusted hazard 0.70 (95% CI 0.54, 0.92)) was followed by an increased risk over the next 3 y (unadjusted hazard 1.31 (95% CI 1.01, 1.70). Fat and fibre advice had no clear effect on coronary or all-cause mortality. The risk of stroke death was increased in the fat advice group-the overall unadjusted hazard was 2.03 (95% CI 1.14, 3.63).

CONCLUSIONS

In this follow-up of a trial of intensive dietary advice following myocardial infarction we did not observe any substantial long-term survival benefit. Further trials of fish and fibre advice are feasible and necessary to clarify the role of these foods in coronary disease.

Colon cancer: detection and prevention

Recent data have advanced our ability to detect, survey, and manage patients with colonic neoplasia. Current studies and consensus statements increasingly support the role of colonoscopic screening over less invasive testing such as FOBT or FS for appropriately selected individuals. There are many issues, however, that remain unresolved. What is the appropriate surveillance of an individual with a single family member who had colon cancer at an early age? How should family members of suspected HNPCC kindreds be managed? There has yet to be a prospective cohort validation of the Bethesda criteria in directing clinical practice, with the endpoint of mortality reduction. Questions regarding prophylaxis with dietary supplements and medications are exciting areas that are currently under study. As newer technologies become clinically available for molecular diagnostics and screening, and virtual colonoscopy with computed tomography and magnetic resonance disseminates, there will undoubtedly be new questions to be answered regarding their ability to aid in the detection and management of colon cancer.