Calcium supplements for the prevention of colorectal adenomas. Calcium Polyp Prevention Study Group

Calcium and colorectal cancer: some questions remain

There is convincing laboratory evidence that calcium reduces the risk of colorectal cancer, but previous epidemiologic studies have reported somewhat inconsistent results. A recent large prospective study confirms that higher calcium intake is associated with a modestly reduced risk of distal colorectal cancer. There was little additional risk reduction associated with consumers of more than 700 mg calcium/day. This study also suggests that certain subgroups, such as males, smokers, and people who consume low levels of vitamin D, may be at differential risk. Because colon cancer is a common disease, even a modest decrease in risk has the potential for preventing a substantial number of cases.

Cyclooxygenase-2 and Gastrointestinal Cancer

The cyclooxygenase (COX) enzymes (COX-1 and COX-2) are key enzymes of prostaglandin (PG) biosynthesis. Nonselective non-steroidal anti-inflammatory drugs (NSAIDs) inhibit the enzymatic activity of both COX-1 and COX-2. Selective COX-2 inhibitors have been developed that appear to have 50% less gastrointestinal toxicity than traditional nonselective NSAIDs. Experimental evidence suggests that the COX pathway is involved in tumor promotion. Evidence to support this comes from both clinical and laboratory findings suggesting that chronic NSAID use reduces the relative risk for developing colorectal cancer (CRC). Although the precise mechanism or mechanisms by which these drugs affect tumor progression is not completely understood, it is likely that part of their anti-tumor effect is due to inhibition of the COX- 2 enzyme. COX-2 levels are increased in CRC as well as in several other solid malignancies. COX-2-derived bioactive lipid products promote tumor-associated n eovascularization, inhibit cell death, and stimulate cell proliferation and motility. Additionally, treatment with COX-2-selective inhibitors reduces polyp burden in animal models of intestinal neoplasia and in humans with familial adenomatous polyposis (FAP). Ongoing human clinical trails are under way to test the efficacy of COX-2-selective inhibitors in a number of human cancers.

Cancer in the elderly: is it preventable?

It is the goal of the American Cancer Society to decrease the mortality from cancer by 50% and the incidence of cancer by 25% by the year 2015 in the United States. Achieving this goal requires intervention at the primary (incidence) and secondary (mortality) prevention stages, and will involve a concerted effort of the individual practitioner, governmental agencies, local, state, and national interest groups, and the population at large. Primary care practitioners must increase their level of enthusiasm for cancer prevention, and actively counsel patients about cancer risks and preventive measures. Practitioners should encourage inclined patients by providing support and specialty resources, such as dieticians, exercise therapists, and smoking and alcohol cessation programs. The greatest effort lies in the general population, who must adopt a healthier lifestyle, including appropriate diet, smoking cessation, control of obesity, and daily exercise. None of these lifestyle changes are easy to embrace, but once educated about lifestyle and risk of cancer, people have a powerful incentive to change. Continued public awareness campaigns and encouragement from health care providers are essential for the success of such programs. The success in smoking cessation shows that achieving societal lifestyle changes on a large scale is possible. The elderly are especially prone to benefit from primary and secondary prevention techniques, and it must not be assumed that only the young will realize the benefits of prevention and screening. The association of age and cancer risk will always be present, but need not be as consequential as it is now. Although cancer prevention may have a limited role in antiaging per se, the feasibility of cancer risk reduction has a definite role in aging successfully.

Colorectal cancer chemoprevention--an overview of the science

The development and dissemination of sophisticated detection technologies have recently exposed the high prevalence of preinvasive colorectal neoplasia in the adult U.S. population. Although cancer screening and surveillance provide opportunities for risk stratification, they achieve risk reduction only when coupled with effective interventions. This review surveys the lead compounds for colorectal cancer prevention and the measures by which they may be prioritized for clinical testing. Clinical trials remain the rate-limiting step in agent development, and novel trial designs are needed to hasten agent identification and testing for cancer prevention. Innovative research models include the nesting of prevention end points within cancer treatment trials and within trials testing promising preventive compounds intended for nononcologic indications.

Calcium intake trends and health consequences from childhood through adulthood

Issues involving low calcium intake and dairy product consumption are currently the focus of much debate and discussion at both the scientific and lay community levels. In this review, we examine the following major areas of interest: (1). the role of calcium intake and dairy product consumption in chronic diseases, (2). nutritional qualities of milk and other dairy products, (3). trends in calcium intake and dairy product consumption, (4). current status of calcium intakes and dairy product consumption in children, (5). tracking of calcium intake and diary product consumption, (6). the impact of school meal participation on calcium intake and dairy product consumption, (7). concerns related to calcium-fortified foods and beverages and (8). factors influencing children's milk consumption. To date, the findings indicate that calcium intake and dairy product consumption have beneficial roles in a variety of chronic diseases; dairy products provide an abundant source of vitamins and minerals; calcium intakes of children have increased over time, yet intakes are not meeting the current adequate intake (AI) calcium recommendations; dairy consumption has decreased, and soft drink consumption and, possibly, consumption of calcium-fortified products have increased; consumption of dairy products have a positive nutritional impact on diets of children, particularly from school meals, and there are many factors which influence children's milk consumption, all of which need to be considered in our efforts to promote adequate calcium intakes by children. Based on this review, areas that need immediate attention and future research imperatives are summarized in an effort to further our understanding on what we already know and what we need to know to promote healthier eating habits early in life.

Circulating Vitamin D Metabolites, Polymorphism in Vitamin D Receptor, and Colorectal Adenoma Risk

Objective: Vitamin D is a potential agent for the prevention of colorectal cancer possibly through mechanisms mediated by the vitamin D receptor (VDR). We investigated the association of circulating vitamin D metabolites and a genetic variant of the VDR gene with advanced colorectal adenoma, a precursor lesion of colorectal cancer. Methods: Cases with advanced adenoma of the distal large bowel and gender- and ethnicity-matched controls with a negative sigmoidoscopy were randomly selected from participants in the Prostate, Lung, Colorectal and Ovarian Cancer Screening trial. Genotype analysis of the VDR TaqI polymorphism was completed on 763 cases and 774 controls. Serum levels of 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] were measured in a subset of 394 cases and 397 controls. Results: Serum levels of 25(OH)D were inversely associated with advanced adenoma risk in women but not in men. Comparing those in the highest quintile with those in the lowest quintile, the risk for advanced adenoma decreased by 73% in women [odds ratio (OR) = 0.27, 95% confidence interval (95% CI) = 0.11–0.69; P for trend = 0.0002], while the risk did not decrease in men (OR = 1.10, 95% CI = 0.60–2.05; P for trend = 0.85). In women, 25(OH)D levels were significantly higher in current users of hormone replacement therapy (HRT) than in former or never HRT users. Neither serum 1,25(OH)2D nor VDR TaqI genotype was associated with advanced adenoma risk. Conclusion: Higher serum 25(OH)D levels were associated with decreased adenoma risk. Serum 1,25(OH)2D and VDR TaqI genotype were not associated with adenoma risk.

Short-term impact of cancer prevention and screening activities on quality of life

PURPOSE

There are few data on the short-term effects of participating in cancer prevention activities, undergoing genetic risk assessment, or having routine screening. The objective of this article is to systematically review existing research on short-term effects of prevention, genetic counseling and testing, and screening activities on quality of life.

METHODS

We conducted a MEDLINE search for original research studies that were published between January 1, 1985, and December 31, 2002, and conducted in North America or Western Europe. Data were abstracted and summarized using a standardized format.

RESULTS

We reviewed 210 publications. Most studies focused on psychological states (anxiety, depression), symptoms, or general health status. One hundred thirty-one studies used 51 previously validated noncancer instruments. Many researchers (12.6%) also added cancer-specific measures, such as perceived cancer risk or symptom indices. Only one study measured satisfaction or quality of provider-client communication. While one report examined lost workdays, no other economic consequences of short-term outcomes were evaluated. Among seven studies that assessed short-term outcomes preferences, only four specifically used time trade-off or linear rating scale methods. No study used standard gamble or willingness-to-pay methods. The overwhelming majority of research indicated that short-term effects were transient. Only two studies linked short-term effects to long-term cancer-related health behaviors such as repeat screening.

CONCLUSION

There is considerable heterogeneity in short-term outcome measurement. Clinicians need to be aware of potential for short-term, transient adverse effects. The impact of short-term experiences should to be linked to long-term health status and use of services.

Estrogen plus progestin and colorectal cancer in postmenopausal women

BACKGROUND

Although the Women's Health Initiative (WHI) trial of estrogen plus progestin in postmenopausal women identified more overall health risks than benefits among women in the hormone group, the use of estrogen plus progestin was associated with a significant decrease in the risk of colorectal cancer. We analyzed features of the colorectal cancers that developed and their relation to the characteristics of the participants.

METHODS

In the WHI trial, 16,608 postmenopausal women who were 50 to 79 years of age and had an intact uterus were randomly assigned to a combination of conjugated equine estrogens (0.625 mg per day) plus medroxyprogesterone acetate (2.5 mg per day) or placebo. The main outcome measures were the incidence, stages, and types of colorectal cancer, as determined by blinded central adjudication.

RESULTS

There were 43 invasive colorectal cancers in the hormone group and 72 in the placebo group (hazard ratio, 0.56; 95 percent confidence interval, 0.38 to 0.81; P=0.003). The invasive colorectal cancers in the hormone group were similar in histologic features and grade to those in the placebo group but with a greater number of positive lymph nodes (mean +/-SD, 3.2+/-4.1 vs. 0.8+/-1.7; P=0.002) and were more advanced (regional or metastatic disease, 76.2 percent vs. 48.5 percent; P=0.004). In exploratory analyses, women in the hormone group with antecedent vaginal bleeding had colorectal cancers with a greater number of positive nodes than women in the hormone group who did not have vaginal bleeding (3.8+/-4.3 vs. 0.7+/-1.5 nodes, P=0.006).

CONCLUSIONS

Relatively short-term use of estrogen plus progestin was associated with a decreased risk of colorectal cancer. However, colorectal cancers in women who took estrogen plus progestin were diagnosed at a more advanced stage than those in women who took placebo.

Functions and roles of the extracellular Ca2+-sensing receptor in the gastrointestinal tract

The gastrointestinal tract is vital to food digestion and nutrient absorption as well as normal salt and water homeostasis. Studies over the last several years have shown that the Ca2+-sensing receptor is expressed along the entire gastrointestinal tract. The potential roles for the receptor in gastrointestinal biology are now only beginning to be elucidated and much work remains. Well-studied physiological effects include regulation of gastric acid secretion and modulation of fluid transport in the colon. It remains to be determined if the Ca2+-sensing receptor is involved in calcium handling by the gastrointestinal tract. The ability of organic nutrient receptor agonists/allosteric modifiers, such as polyamines and L-amino acids, to activate the Ca2+-sensing receptor suggest potential roles in signalling nutrient availability to gastric and intestinal epithelial cells. In addition, polyamines are crucial for normal cell proliferation and differentiation required to sustain the rapid turnover of gastrointestinal epithelial cells and the Ca2+-sensing receptor may be involved in this function. Activation of the colonic Ca2+-sensing receptor can abrogate cyclic nucleotide-mediated fluid secretion suggesting a role for the receptor in modifying secretory diarrheas like cholera. Finally, the Ca2+-sensing receptor has been suggested to provide a mechanism for the effect of calcium intake in reducing the risk of colon cancer.

Dietary calcium intake and breast cancer risk among Chinese women in Shanghai

Limited epidemiological evidence suggests that calcium intake may be related to breast cancer risk. Data from a large, population-based, case-control study (n = 1,459 cases, 1,556 controls) conducted in Shanghai, China, between 1996 and 1998 were used to investigate the association between calcium intake and risk for breast cancer. Diet was assessed using a quantitative food-frequency questionnaire. The multivariate-adjusted odds ratio (OR) comparing all women combined in the highest to lowest deciles of total calcium intake was 0.74 (95% confidence interval [CI] = 0.46-1.20). Whereas calcium primarily derived from poultry was inversely associated with risk for breast cancer (comparing the highest to lowest quintile OR = 0.71, 95% CI = 0.55-0.93) with a statistically significant test for trend, calcium derived from milk, seafood, fruit, and vegetables was not associated with risk of breast cancer. Given that breast cancer is one of the top contributors to cancer incidence worldwide, even a moderate inverse association between calcium and breast cancer risk, if confirmed, could have important public health implications in breast cancer prevention.

Adenoma recurrences after resection of colorectal carcinoma: results from the Southwest Oncology Group 9041 calcium chemoprevention pilot study

BACKGROUND

Colorectal adenomas are the usual precursors to carcinoma in sporadic and hereditary colorectal cancers (CRC).

METHODS

A total of 220 CRC patients (stages 0, I, and II) were randomized prospectively in a double-blind pilot study of calcium chemoprevention by using recurrent colorectal adenomas as a surrogate end point. This trial is still in progress, and we report the preliminary findings on adenoma recurrence rates.

RESULTS

Synchronous adenomas were present in 60% of patients, and cancer confined in a polyp was present in 23% of patients. The overall cumulative adenoma recurrence rate was 31% (19% in the first year, 29% for 2 years, and 35% for 3 years). The recurrence rates were greater for patients with synchronous adenomas: 38% at 3 years (P =.01). Lower stage was associated with higher adenoma recurrence rates (P =.04). Factors including age, sex, site of primary cancer, and whether the cancer was confined to a polyp were not significantly associated with differences in adenoma recurrence rates.

CONCLUSIONS

The substantial adenoma recurrence rate in patients resected of CRC justifies colonoscopic surveillance on a periodic basis. Patients with higher rates of adenoma recurrences, such as CRC with synchronous adenomas, are ideal subjects for chemoprevention trials.

Dietary pectin and calcium inhibit colonic proliferation in vivo by differing mechanisms

Diet plays an important role in promoting and/or preventing colon cancer; however, the effects of specific nutrients remain uncertain because of the difficulties in correlating epidemiological and basic observations. Transmissible murine colonic hyperplasia (TMCH) induced by Citrobacter rodentium, causes significant hyperproliferation and hyperplasia in the mouse distal colon and increases the risk of subsequent neoplasia. We have recently shown that TMCH is associated with an increased abundance of cellular beta-catenin and its nuclear translocation coupled with up-regulation of its downstream targets, c-myc and cyclin D1. In this study, we examined the effects of two putatively protective nutrients, calcium and soluble fibre pectin, on molecular events linked to proliferation in the colonic epithelium during TMCH. Dietary intervention incorporating changes in calcium [high (1.0%) and low (0.1%)] and alterations in fibre content (6% pectin and fibre-free) were compared with the standard AIN-93 diet (0.5% calcium, 5% cellulose), followed by histomorphometry and immunochemical assessment of potential oncogenes. Dietary interventions did not alter the time course of Citrobacter infection. Both 1.0% calcium and 6% pectin diet inhibited increases in proliferation and crypt length typically seen in TMCH. Neither the low calcium nor fibre-free diets had significant effect. Pectin diet blocked increases in cellular beta-catenin, cyclin D1 and c-myc levels associated with TMCH by 70%, whereas neither high nor low calcium diet had significant effect on these molecules. Diets supplemented with either calcium or pectin therefore, exert anti-proliferative effects in mouse distal colon involving different molecular pathways. TMCH is thus a diet-sensitive model for examining the effect of specific nutrients on molecular characteristics of the pre-neoplastic colonic epithelium.

Effects of Calcium Supplementation on Circulating Lipids

For about a century there has been recognition that calcium and lipids bind to one another in the gut, each interfering with the other's absorption. Calcium also causes malabsorption of bile acids, which is likely to contribute further to malabsorption of fat. High dietary calcium intakes may also have stimulatory effects on lipolysis. These mechanisms provide a basis for hypothesising that calcium supplementation may impact on circulating lipid concentrations, and there is now a significant amount of observational and trial data indicating that this is the case. The largest randomised controlled trial of calcium effects on lipids was carried out in 223 healthy postmenopausal women, and found that low density lipoprotein-cholesterol (LDL-C) decreased 6.3% and high density lipoprotein-cholesterol (HDL-C) increased by 7.3% at 1-year. The resultant 16.4% increase in HDL-C/LDL-C ratio would be predicted to reduce cardiovascular event rates by 20-30%, which is consistent with the available observational data. There are no trial data addressing this question and it is possible that other lipid-lowering agents, such as hydroxymethylglutaryl coenzyme A reductase inhibitors, might impact on cardiac event rates by mechanisms other than by lowering cholesterol levels. Therefore, caution is appropriate in incorporating these findings into clinical practice, but the balance of evidence suggests that calcium is a cost-effective adjunct to the dietary management of hyperlipidaemia.

Review article: chemoprevention of colorectal cancer

Colorectal cancer is a disease with a high mortality at present, due to the late stage at which many cases present. Attention is therefore focusing on preventative strategies for colorectal cancer given that polyps appear to be identifiable and treatable precursor lesions of this disease. Endoscopic polypectomy has been shown to reduce the incidence of colorectal cancer and there is a good case for endoscopic screening of the general population. However, this will require a large amount of manpower and resources and its success will also depend on the overall compliance of the population. Epidemiological studies have shown that individuals reporting a regular intake of aspirin and other non-steroidal anti-inflammatory drugs have a reduced risk of developing colorectal polyps and cancer. Similarly, a number of natural substances, such as calcium and folate, when supplemented regularly in the diet, have also been linked to a possible decreased incidence of colorectal cancer. This has led to the concept of using such agents to reduce the number of cases of colorectal cancer. In this article, we review the current evidence for the use of these and other agents for the chemoprevention of colorectal cancer, together with theories as to their possible mechanisms of action.

Interventions for patients, providers, and health care organizations

Clinicians and the organizations within which they practice play a major role in enabling patient participation in cancer screening and ensuring quality services. Guided by an ecologic framework, the authors summarize previous literature reviews and exemplary studies of breast, cervical, and colorectal cancer screening intervention studies conducted in health care settings. Lessons learned regarding interventions to maximize the potential of cancer screening are distilled. Four broad lessons learned emphasize that multiple levels of factors-public policy, organizational systems and practice settings, clinicians, and patients-influence cancer screening; that a diverse set of intervention strategies targeted at each of these levels can improve cancer screening rates; that the synergistic effects of multiple strategies often are most effective; and that targeting all components of the screening continuum is important. Recommendations are made for future research and practice, including priorities for intervention research specific to health care settings, the need to take research phases into consideration, the need for studies of health services delivery trends, and methods and measurement issues.

Chronic disease prevention: public health potential and research needs

This paper, arising out of an event to honour the statistical and scientific contributions of Professor Peter Armitage, is concerned with research strategies and needs for chronic disease prevention. A few highlights from recent intervention trials for the prevention of cancer, cardiovascular disease, fractures and diabetes is provided, along with a discussion of some settings where intervention trial results seem discrepant with a body of preceding observational data. This background is used to identify research strategies and infrastructure needs for moving this vitally important research area forward, for both chemoprevention and lifestyle modification interventions.

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

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

Preclinical models for chemoprevention of colon cancer

Colon cancer is the second leading cause of cancer incidence and death in the USA in 2002. Specific genetic defects have been identified which cause hereditary colon cancers in humans. In addition, a number of intestinal luminal risk factors for colon cancer have been described. This information has been exploited to develop experimental cell and rodent models which recapitulate features of human colon cancer. In this chapter, we will discuss the strengths and limitations of these models to further our understanding of basic mechanisms of colon carcinogenesis and to develop strategies for colon cancer chemoprevention.

Meat and cancer: haemoglobin and haemin in a low-calcium diet promote colorectal carcinogenesis at the aberrant crypt stage in rats

High intake of red meat, but not of white meat, is associated with an increased risk of colon cancer. However, red meat does not promote cancer in rodents. Haemin, added to low-calcium diets, increases colonic proliferation, and haemoglobin, added to high-fat diets, increases the colon tumour incidence in rats, an effect possibly due to peroxyl radicals. We thus speculated that haem might be the promoting agent in meat, and that prevention strategies could use calcium and antioxidants. These hypotheses were tested in rats at the aberrant crypt foci (ACF) stage at 100 days. F344 rats (n = 124) were given an injection of azoxymethane and were then randomized to 11 groups fed with low-calcium (20 micro mol/g) AIN76-based diets, containing 5% safflower oil. Haemin (0.25, 0.5 and 1.5 micro mol/g) or haemoglobin (1.5 and 3 micro mol haem/g) was added to five experimental diets, compared with a control diet without haem. Three other high-haemin diets (1.5 micro mol/g) were supplemented with calcium (250 micro mol/g), antioxidant butylated hydroxyanisole and rutin (0.05% each), and olive oil, which replaced safflower oil. Faecal water was assayed for lipid peroxidation by thiobarbituric acid reactive substances (TBARs) test, and for cytolytic activity. Haemin strikingly increased the ACF size, dose-dependently, from 2.6 to 11.4 crypts/ACF (all P < 0.001). The high-haemin diet also increased the number of ACF per colon (P < 0.001). Promotion was associated with increased faecal water TBARs and cytotoxicity. Calcium, olive oil and antioxidants each inhibited the haemin-induced ACF promotion, and normalized the faecal TBARs and cytotoxicity. The haemoglobin diets increased the number of ACF and faecal TBARs, but not the ACF size or the faecal cytotoxicity. In conclusion, dietary haemin is the most potent known ACF promoter. Haemoglobin is also a potent promoter of colorectal carcinogenesis. The results suggest that myoglobin in red meat could promote colon cancer. Diets high in calcium, or in oxidation-resistant fats, may prevent the possible cancer-promoting effect of red meat.

The potential benefits of dietary and/or supplemental calcium and vitamin D

Osteoporosis is a significant problem in women and men. In addition, as osteoporosis has garnered more attention there should be more attention than ever placed on the potential benefits of calcium and vitamin D. Clinicians need to inform patients that there are numerous healthy dietary sources of calcium and vitamin D. Calcium and vitamin D supplements seem to act synergistically to reduce fracture risk in men and women; therefore, they need to be taken together to impact fracture risk. In addition, almost every randomized trial of an effective osteoporosis drug therapy has utilized calcium and vitamin D to enhance the efficacy of the drug itself. Several forms of calcium supplements are commercially available today and clinicians need to understand the similarities and differences between them. Calcium and vitamin D in moderation also have a good safety profile and may actually have benefits far beyond osteoporosis therapy. For example, calcium may increase high-density lipoprotein (HDL), prevent colon polyps, reduce blood pressure, reduce kidney stone recurrence, and may promote weight loss. Vitamin D may reduce the risk of some cancers, provide an enhanced response to some chemotherapeutic agents, prevent type I diabetes, and may reduce tooth loss along with calcium. Clinicians need to encourage individuals to receive the recommended daily allowance of these two agents because they seem to have an impact on numerous health conditions besides osteoporosis.

Chemoprevention of colorectal cancer in ulcerative colitis

BACKGROUND

Patients with ulcerative colitis (UC) are at greater risk of developing colorectal cancer (CRC) than the general population. Both duration and extent of UC are important risk factors for CRC, as is the presence of primary sclerosing cholangitis, family history of CRC, and (in some studies) early age at diagnosis of UC. Efforts to reduce this risk have focused on colonoscopic surveillance as the best alternative to the more definitive, but less appealing, approach of prophylactic colectomy. However, spurred on by findings in the sporadic CRC literature, there has been a growing interest in a possible role for chemoprevention of CRC in patients with UC.

EMPIRICAL STUDIES

Published evidence to date indicates that 5-aminosalicylic acid agents are protective against the development of dysplasia and CRC. Oral, but not topical, steroids also appear to be chemoprotective, but their chronic use cannot be recommended for this indication. Ursodeoxycholic acid has been shown to reduce the risk of neoplasia in UC patients with primary sclerosing cholangitis. Evidence suggests, but does not prove, that folic acid is chemopreventive in patients with UC. Further studies are needed to fully define the chemoprotective role of these and other agents.

Dietary minerals and modification of cardiovascular risk factors

High serum cholesterol, hypertension and obesity are major risk factors for cardiovascular diseases, and together with insulin resistance form a deadly disorder referred to as the metabolic syndrome. All the aspects of this syndrome are strongly related to dietary and lifestyle factors; therefore, it would be reasonable to look for dietary approaches to their modification. Mineral nutrients, such as calcium, potassium and magnesium, lower blood pressure, and especially calcium has beneficial effects also on serum lipids. Recent evidence suggests that increased intake of calcium may help in weight control as well. This review summarizes previous literature on the effects and use of dietary minerals on serum lipids, blood pressure and obesity, with specific focus on the effects of calcium. Calcium and magnesium as divalent cations can form insoluble soaps with fatty acids in the intestine and thus prevent the absorption of part of the dietary fat. Decreased absorption of saturated fat leads to reduction in serum cholesterol level via decreased production of VLDL and increased intake of LDL in the liver. Dietary calcium may also bind bile acids, which increases the conversion of cholesterol to bile acids in the liver. Furthermore, calcium appears to enhance the cholesterol-lowering effect of plant sterols. Thus, dietary combination of the mineral nutrients and plant sterols provides a promising novel approach to the modification of cardiovascular risk factors.

Daily soluble aspirin and prevention of colorectal adenoma recurrence: one-year results of the APACC trial

BACKGROUND & AIMS

Epidemiologic and experimental studies have suggested that aspirin intake reduces the risk for colorectal carcinogenesis. However, the available data are not sufficient to serve as the basis for firm recommendations.

METHODS

We randomly assigned 272 patients with a history of colorectal adenomas (at least one more than 5 mm in diameter, or more than 3) to daily lysine acetylsalicylate (160 or 300 mg/day) or placebo for 4 years. The primary end points were adenoma recurrence after 1 and 4 years. These results are those of the year 1 colonoscopy.

RESULTS

Among the 238 patients who completed the year 1 colonoscopy, at least one adenoma was observed in 38 patients of the 126 (30%) in the aspirin group and in 46 of the 112 (41%) in the placebo group; relative risk was 0.73 (95% confidence interval [CI]: 0.52-1.04; P = 0.08). At least one adenoma of more than 5 mm diameter was observed in 13 patients (10%) in the aspirin group and 26 (23%) in the placebo group (P = 0.01). The corresponding numbers for adenomas more than 10 mm in diameter were one (1%) and 7 (6%) (P = 0.05). Stepwise regression showed that independent factors associated with lower adenoma recurrence are aspirin treatment (adenoma >5 mm, P = 0.01), absence of personal history of adenoma before the entry colonoscopy (P = 0.01), and initial adenomatous polyp burden less than 10 mm (P = 0.001).

CONCLUSIONS

Daily soluble aspirin is associated with a reduction in the risk for recurrent adenomas found at colonoscopy 1 year after starting treatment.

Dietary calcium and vitamin D intake and risk of colorectal cancer: a prospective cohort study in women

Although laboratory data and a few adenoma prevention trials suggest that calcium supplementation may reduce the risk of colorectal neoplasia, the results of observational studies of calcium intake and colorectal cancer risk are contradictory. However, few studies have examined the association among women or effects in specific colon subsites. Women with colorectal cancer diagnosed through 31 December 2000 were identified by linkage to regional cancer registries. During an average 11.3 yr of follow-up of 61,463 women, we observed 572 incident cases of colorectal cancer. Using data obtained from a 67-item food frequency questionnaire and Cox proportional hazards models to estimate rate ratios and 95% confidence intervals, we found an inverse association between dietary calcium intake and colorectal cancer risk. Women with the highest calcium intake (median 914 mg/day) had a reduced risk of colorectal cancer (rate ratio = 0.72, 95% confidence interval = 0.056-0.93, P for trend = 0.02) compared with women with the lowest intake (median 486 mg/day). Furthermore, our results suggest that the inverse association may be strongest in relation to distal cancers and among older women. The association with dairy products was less clear, suggesting that calcium intake per se is more important than specific calcium sources. Vitamin D intake was not clearly associated with risk. In sum, our data suggest that high calcium intake may lower colorectal cancer risk.

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.

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.

Intestinal polyp formation in the Apcmin mouse: effects of levels of dietary calcium and altered vitamin D homeostasis

This study evaluated the effects of various levels of dietary calcium on polyp formation, vitamin D homeostasis, and fecal bile acids in the Apcmin mouse. Female Apcmin mice were randomized to three groups and fed a purified diet with either half or double the level of calcium in control AIN-93G. Serum 25-OH-D and fecal bile acids were measured at weeks 0 and 12 of treatment. Mice were killed for polyp scoring by two observers blinded to treatment after 12 weeks. Results show there was no difference in polyp number or tumor load with dietary calcium in any treatment group. Serum 25-OH-D was reduced and total fecal bile acids were increased in animals that received the high calcium diet. We have previously shown that vitamin D supplementation diminishes polyp load; the lack of effect of an altered calcium diet seen here may be due to a disturbance in vitamin D homeostasis.

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.

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.

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.

Screening, prevention and socioeconomic costs associated with the treatment of colorectal cancer

Colorectal cancer (CRC), the third most prevalent cancer worldwide, imposes a significant economic and humanistic burden on patients and society. One study conservatively estimated the annual expenditures for colorectal cancer to be approximately dollars US 5.3 billion in 2000, including both direct and indirect costs. However, other investigators estimated inpatient costs alone incurred in the US in 1994 to be around dollars US 5.14 billion. Therefore, the economic burden of colorectal cancer in the US could be projected to be somewhere in the range of dollars US 5.5-6.5 billion by considering that inpatient costs approximate 80% of total direct costs. No worldwide data have been published, but assuming that the US represents 25-40% of total expenditures in oncology, as seen for breast and lung cancers, a rough estimate for colorectal cancer would be in the range of dollars US 14-22 billion. Screening helps increase patient survival by diagnosing colorectal cancer early. The ideal method among the four tests most used (faecal occult blood test, flexible sigmoidoscopy, colonoscopy and double contrast barium enema) has not been identified. Economic studies of colorectal cancer screening are complex because of the many variables involved, as well as the fact that the outcomes must be followed for many years, and the lack of consensus on screening guidelines. Intuitively, modelling colorectal cancer is one way to overcome these hurdles; published modelling studies predict colorectal cancer screening programs to be within the threshold of dollars US 40000 per life-year saved. The faecal occult blood test appears to be the only clearly effective test, both from a clinical and an economic viewpoint. Important limitations are the invasiveness and inconvenience of the screening procedures, except faecal occult blood test. Patients' comfort and satisfaction are essential in improving compliance with screening recommendations, which appears to be low even in the US (35% of the general population aged over 40 years and 60% of the high-risk population), the country with the highest awareness and compliance in the world. Since colorectal cancer is generally a disease of the elderly, its economic burden is expected to grow in the near future, mainly due to population aging. Potential avenues to pursue in order to contain or reduce the economic burden of colorectal cancer would be the design and implementation of efficient screening programmes, the improvement of patient awareness and compliance with screening guidelines, the development of appropriate prevention programs (i.e. primary and secondary), and earlier diagnosis.

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.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

New avenues for the prevention of colorectal cancer: targeting cyclo-oxygenase-2 activity

Carcinoma of the colon and/or rectum represents the second most common gastrointestinal malignancy worldwide. Despite this prevalence, current therapeutic regimens remain largely ineffectual, particularly when the disease is diagnosed at an advanced stage. Recent work in the field of colorectal cancer has established that a chronic intake of non steroidal anti-inflammatory drugs can reduce the risk of developing colorectal cancer. Although the precise mechanism(s) by which these drugs inhibit tumour growth is not completely understood, it is likely that at least a part of their anti-tumorigenic effects results from an inhibition of the cyclo-oxygenase-2 enzyme. This chapter will focus on this emerging research area and the promise it brings for identifying new strategies for the prevention of colorectal cancer.

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.

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.

Review article: lactose--a potential prebiotic

Lactose maldigestion, which affects a large majority of the world's population, has been mostly linked with uncomfortable symptoms. In addition, dairy consumption is variably blamed or recommended for a number of ill effects. There is, however, emerging evidence that certain lactic acid-producing bacteria, which selectively consume prebiotics, may be beneficial against some lower intestinal diseases. Lactose maldigestion and lactose should perhaps be re-evaluated as a potential provider of such a prebiotic. This historical and observational review discusses lactose and argues the opinion that it has prebiotic potential. Moreover, in maldigesters, natural ingestion or lack thereof may be relevant in the pathogenesis of diseases such as colorectal cancer and inflammatory bowel diseases.