Insulin and colon cancer

Colorectal cancer screening in North Carolina: associations with diabetes mellitus and demographic and health characteristics

BACKGROUND

Diabetes mellitus (DM) may increase the risk of colorectal cancer, a leading cause of cancer death in the United States. This report examines factors associated with colorectal cancer screening, including DM status.

METHODS

Data from the 1993/1995/1997 North Carolina (NC) Behavioral Risk Factor Surveillance System were analyzed to assess self-reported screening rates within guidelines for sigmoidoscopy/proctoscopy (sig/proct) and fecal occult blood test (FOBT).

RESULTS

Overall, 28.6, 27.2, and 19.7% received a sig/proct, FOBT, or either test within guidelines, respectively. Screening rates varied according to some demographic variables, but not by DM status. However, DM status changed some relationships between screening and some demographic/health characteristics.

CONCLUSIONS

Colorectal cancer screening in NC is similar to national rates, but certain subgroups are less likely to get screened. Persons with DM are as likely to get colorectal cancer screening, but some groups with DM (ethnic minorities, persons of low socioeconomic status) may be at high risk for not getting screened. Educational efforts to increase screening should target these groups.

Dietary glycemic load and colorectal cancer risk

BACKGROUND

Insulin and insulin-like growth factors can stimulate proliferation of colorectal cells. High intake of refined carbohydrates and markers of insulin resistance are associated with colorectal cancer. To test the insulin/colon cancer hypothesis, we determined whether the dietary glycemic index and the glycemic load are associated with colorectal cancer risk.

DESIGN

A case-control study on colorectal cancer conducted in Italy. Cases included 1125 men and 828 women with histologically confirmed incident cancer of the colon or rectum. Controls were 2073 men and 2081 women hospitalized for acute conditions. We calculated average daily dietary glycemic index and glycemic load, and fiber intake from a validated food frequency questionnaire.

RESULTS

Direct associations with colorectal cancer risk emerged for glycemic index (odds ratio (OR) in highest vs. lowest quintile = 1.7; 95% confidence interval (CI): 1.4-2.0) and glycemic load (OR = 1.8; 95% CI: 1.5-2.2), after allowance for sociodemographic factors, physical activity, number of daily meals, and intakes of fiber, alcohol and energy. ORs were more elevated for cancer of the colon than rectum. Overweight and low intake of fiber from vegetables and fruit appeared to amplify the adverse consequences of high glycemic load.

CONCLUSIONS

The positive associations of glycemic index and load with colorectal cancer suggest a detrimental role of refined carbohydrates in the etiology of the disease.

Energy balance and cancer: the role of insulin and insulin-like growth factor-I

Recent theories propose that a Western lifestyle may increase cancer risk through alterations in the metabolism of insulin and insulin-like growth factors (IGF: McKeown-Eyssen, 1994; Giovannucci, 1995; Kaaks, 19%; Werner & LeRoith, 1996). Insulin regulates energy metabolism, and increases the bioactivity of IGF-I, by enhancing its synthesis. and by decreasing several of its binding proteins (IGFBP; IGFBP-1 and -2). Insulin and IGF-I both stimulate anabolic processes as a function of available energy and elementary substrates (e.g. amino acids). The anabolic signals by insulin or IGF-I can promote tumour development by inhibiting apoptosis, and by stimulating cell proliferation. Furthermore, both insulin and IGF-I stimulate the synthesis of sex steroids, and inhibit the synthesis of sex hormone-binding globulin (SFIBG), a binding protein that regulates the bioavailability of circulating sex steroids to tissues. The present paper reviews epidemiological findings relating the risk of cancers of the colo-rectum, pancreas, breast, endometrium and prostate to body size (obesity, height) and physical activity, and discusses the relationships between obesity and physical activity and plasma levels of insulin, IGF-I and IGFBP. Subsequent sections review epidemiological findings relating cancer risk to indices of chronic hyperinsulinaemia, and to plasma levels of IGF-I and IGFBP. Conclusions are that chronic hyperinsulinaemia may be a cause of cancers of the colon, pancreas and endometrium, and also possibly of the breast. On the other hand, elevated plasma IGF-I, as total concentrations or relative to levels of IGFBP-3, appears to be related to an increased risk of prostate cancer, breast cancer in young women, and possibly cob-rectal cancer. For cancers of the endometrium, breast and prostate, these findings are discussed in the context of relationships between insulin and IGF-I and levels of bioavailable sex steroids.

Prospective study of colorectal cancer risk and physical activity, diabetes, blood glucose and BMI: exploring the hyperinsulinaemia hypothesis

A sedentary lifestyle, obesity, and a Westernized diet have been implicated in the aetiology of both colorectal cancer and non-insulin dependent diabetes mellitus, leading to the hypothesis that hyperinsulinaemia may promote colorectal cancer. We prospectively examined the association between colorectal cancer risk and factors related to insulin resistance and hyperinsulinaemia, including BMI, physical activity, diabetes mellitus, and blood glucose, in a cohort of 75 219 Norwegian men and women. Information on incident cases of colorectal cancer was made available from the Norwegian Cancer Registry. Reported P values are two-sided. During 12 years of follow up, 730 cases of colorectal cancer were registered. In men, but not in women, we found a negative association with leisure-time physical activity (P for trend = 0.002), with an age-adjusted RR for the highest versus the lowest category of activity of 0.54 (95% CI = 0.37-0.79). Women, but not men, with a history of diabetes were at increased risk of colorectal cancer (age-adjusted RR = 1.55; 95% CI = 1.04-2.31), as were women with non-fasting blood glucose > or = 8.0 mmol l(-1)(age-adjusted RR = 1.98; 95% CI = 1.31-2.98) compared with glucose <8.0 mmol l(-1). Overall, we found no association between BMI and risk of colorectal cancer. Additional adjustment including each of the main variables, marital status, and educational attainment did not materially change the results. We conclude that the inverse association between leisure-time physical activity and colorectal cancer in men, and the positive association between diabetes, blood glucose, and colorectal cancer in women, at least in part, support the hypothesis that insulin may act as a tumour promoter in colorectal carcinogenesis.

Susceptibility of lean and obese Zucker rats to tumorigenesis induced by N-methyl-N-nitrosourea

To address the possible involvement of hyperinsulinemia in breast cancer development, we have examined the susceptibility of lean and obese Zucker rats to N-methyl-N-nitrosourea (MNU)-induced mammary cancer. Fifty-day-old female lean or obese Zucker rats received intraperitoneal (i.p.) injections of 37.5 or 20 mg/kg MNU, respectively. We showed in separate experiments that these doses produce similar levels of DNA methylation in the mammary epithelial cells of the lean and obese animals. Over the course of 29 weeks following MNU treatment, half of the lean rats developed carcinomas of the mammary gland, demonstrating that they are of intermediate susceptibility to mammary tumorigenesis. During this period, the obese rats developed hyperinsulinemia and insulin resistance as expected. Although palpable tumors developed at a similar rate in the lean and obese rats, only 10% of the obese animals developed mammary carcinomas. The obese rats, however, developed a high incidence (63.3%) of epidermal cysts that occurred mainly in the region of the mammary glands. A 13.3% incidence of colon carcinomas was also found in the obese rats. These results suggest that the development of hyperinsulinemia does not render the obese Zucker rats more susceptible to mammary gland carcinogenesis. Our observation of colon carcinomas in obese, but not lean rats, however, is consistent with evidence that hyperinsulinemia promotes colon cancer in rodents and humans.

The relation of type 2 diabetes and cancer

Increasing evidence indicates that individuals with type 2 diabetes (diabetes) are at elevated risk for several common human malignancies, including cancers of the colon, breast, endometrium, pancreas, and liver. In particular, the consistent positive results reported by prospective investigations make it unlikely that methodologic issues, occult tumors, or chance results could explain the findings. Since diabetes and impaired fasting glucose together affect >25% of Americans above age 50, even a moderate etiologic association (e.g., relative risk = 1.5) would explain >10% of involved malignancies. Laboratory studies have suggested biologically plausible mechanisms. Insulin, for example, is typically at high levels during the development and early stages of diabetes. Activation of the insulin receptor by its ligand, or cross-activation of the insulin-like growth factor-I receptor, has been shown to be mitogenic and promote tumorigenesis in various model systems. A "unifying concept," in fact, holds that hyperinsulinemia may underlie the cancer associations of several additional risk factors, including high waist circumference, visceral fat, waist-to-hip ratio, body mass index, sedentary lifestyle, and energy intake. In this review, we assess current evidence regarding the relation of type 2 diabetes with cancer, and evaluate the findings in terms of well-accepted criteria for establishing causality.

A prospective study of insulin-like growth factor-I, IGF-binding proteins-1, -2 and -3 and lung cancer risk in women

Insulin-like growth factor-I (IGF-I) has mitogenic and anti-apoptotic properties and has been implicated in the development of breast, colorectum, prostate and lung cancer. IGF binding proteins (IGFBPs) are not only carrier proteins for IGFs but also hold a central position in IGF ligand-receptor interactions through influences on the bioavailability and distribution of IGFs in the extracellular environment. A case-control study nested within the New York University Women's Health Study Cohort included 93 women diagnosed with lung cancer at least 6 months after recruitment into the study. Two controls (n = 186) were matched to each case on age, date of blood sampling, menopausal status, day of menstrual cycle and questionnaire data of smoking status at the time of blood donation. Serum IGF-I, IGFBP-1, -2 and -3, insulin and cotinine were measured. Mean serum levels of IGF-I, IGFBP-1, -2 and -3 were not significantly different between the case and control groups. Univariate logistic regression analyses showed no association of lung cancer risk with serum levels of IGF-I or any of the IGFBPs. These results remained virtually the same in multivariate analyses, including adjustment for cotinine, time since last meal, BMI, IGF-I or IGFBP-3, respectively. Exclusion of cases diagnosed within 3 years of recruitment in the cohort, or restriction of the analyses to adenocarcinomas only, did not alter these results. Our study does not offer evidence in support of an association between prediagnostic serum levels of IGF-I or IGFBP-1, -2 and -3 and lung cancer risk in women.

A reduction in blood insulin levels as a host endocrine response during tumor development

It has been previously reported that endogenous insulin levels decrease during tumor growth. We have now studied whether this host endocrine response is independent of the way in which the tumor is induced. For this purpose, animals transplanted with tumor cells induced by 3-methylcholanthrene (MCA) or 7,12-dimethylbenz(a) anthracene (DMBA), or with EL-4 lymphoma cells, and animals that develop autochthonous tumors induced by MCA or the murine mammary tumor virus (MMTV) were used. These procedures result in the induction of tumors of different histologic types: fibrosarcoma, mammary adenocarcinoma and lymphoma. The results obtained showed that a reduction in insulin levels preceded the overt appearance of tumors in all models of syngeneic or autochthonous tumors studied but not when DMBA-induced tumor cells were administered into allogeneic recipients. Reduced levels of insulin before tumor detection appeared to affect the onset of MCA-induced tumors. Indeed, those mice with a late tumor onset were those that had a more pronounced decrease in insulin blood levels during the induction phase of autochthonous MCA-induced tumors. Soluble factors associated with tumor growth seem to mediate the reduction in insulin blood levels in mice transplanted with EL-4 tumor cells. The results obtained indicate that the reduction in insulin levels detected is a consequence of the recognition of tumor cells by the host, and seems to be independent of the histologic type of the neoplastic cells that develop. Pharmacological interventions at the levels of mechanisms that control insulin output should clarify the relevance of decreased levels of this hormone for tumor development.

Induction of hepatic insulin-like growth factor binding protein-1 (IGFBP-1) in rats by dietary n-6 polyunsaturated fatty acids

The insulin-like growth factors (IGFs) are mitogenic polypeptides that have been linked to a variety of normal physiological processes as well as neoplasia. Overexpression of several components of the IGF system is associated with hepatocarcinogenesis in humans and rodents. In rat liver, diets rich in n-6 polyunsaturated fatty acid (PUFA) enhance the development of preneoplastic lesions and tumors. Therefore, the objective of this study was to determine the effect of these dietary fatty acids on the hepatic expression of the various components of the IGF system. The mRNA levels of IGF-1 and the type 1 receptor were not different in livers of rats fed a diet containing 20% corn oil (CO) compared with those fed 5% CO. Analysis of the IGF binding proteins revealed that insulin-like growth factor binding protein-1 (IGFBP-1) levels were altered by the amount and type of dietary fat. A 2.5-fold induction of IGFBP-1 mRNA occurred within 1 week after the animals were fed the 20% corn oil diet compared with those fed 5% CO and was further enhanced to over 6-fold after 1 month. Furthermore, IGFBP-1 protein was only detectable in the livers of animals fed the 20% CO diet. Induction of IGFBP-1 mRNA (4.5-fold) also occurred in rats fed a high-fat diet containing safflower (rich in n-6 PUFAs) compared with those fed a high-fat diet containing menhaden oil (rich in n-3 PUFAs). The induction of IGFBP-1 mRNA was independent of serum insulin levels and the development of insulin resistance. Since IGFBP-1 mRNA is upregulated in regenerating liver, we reasoned that the induction of IGFBP-1 mRNA may be associated with an increase in cell proliferation; however, no difference was observed in the hepatic labeling index of rats fed the 20% CO compared with the 5% CO diet. In summary, these studies show a striking induction by dietary n-6 PUFAs of hepatic IGFBP-1, a protein that has been implicated in liver cancer development.

Diabetes mellitus and cancer

Although an association between diabetes and cancer was found over 100 years ago, the issue underwent different interpretations over the subsequent decades, and only modern, prospective, epidemiological cohort and case-control studies conducted in several countries have provided reliable evidence of an increased cancer risk in diabetic patients, mainly in those with type 2 diabetes. This risk varies according to the tumor site: it is the greatest for primary liver cancer, moderately elevated for pancreatic cancer, and relatively low for colorectal, endometrial, breast, and renal cancers. The cause of the association is not clear and remains the subject of different hypotheses. The most frequently cited reason is the potential effect of insulin. Found in high concentrations, due to insulin resistance in most patients with type 2 diabetes, this hormone is believed to express a mitogenic effect. This hypothesis needs to be confirmed in appropriately programmed prospective studies, but it may already be helpful in choosing an adequate treatment for type 2 diabetes to achieve optimal metabolic control with a simultaneous reduction in hyperinsulinemia, such as diet, physical exercise, metformin, and acarbose.

Mechanisms for the impact of whole grain foods on cancer risk

Dietary guidance recommends consumption of whole grains for the prevention of cancer. Epidemiologic studies find that whole grains are protective against cancer, especially gastrointestinal cancers such as gastric and colonic, and hormonally-dependent cancers including breast and prostate. Four potential mechanisms for the protectiveness of whole grains against cancer are described. First, whole grains are concentrated sources of dietary fiber, resistant starch, and oligosaccharides, fermentable carbohydrates thought to protect against cancer. Fermentation of carbohydrates in the colon results in production of short chain fatty acids that lower colonic pH and serve as an energy source for the colonocytes. Secondly, whole grains are rich in antioxidants, including trace minerals and phenolic compounds, and antioxidants have been proposed to be important in cancer prevention. Thirdly, whole grains are significant sources of phytoestrogens that have hormonal effects related to cancer protection. Phytoestrogens are thought to be particularly important in the prevention of hormonally-dependent cancers such as breast and prostate. Finally, whole grains mediate glucose response, which has been proposed to protect against colon and breast cancer.

Endocrine host responses during early and late phases of tumor development

It is well established that hormones affect tumor growth. Conversely, inoculation of cells obtained from tumors that had been transplanted for many generations causes changes in the concentration of different hormones before and after tumor detection. We aimed at answering the question of whether hormonal alterations also occur during the development of primary tumors and following transplantation of tumors from early generations. Primary tumors were induced in mice by either the carcinogenic agent 3-methylcholanthrene, which produces fibrosarcomas, or the milk-transmitted mammary tumor virus, which induces adenocarcinomas. The results showed that (i) in both models, an early reduction in plasma insulin and prolactin levels occurred, and in the case of insulin, this reduction was sustained for a prolong period prior to tumor detection, indicating that recognition by the host of emergent tumor cells triggers an endocrine response; (ii) in contrast with multiply transplanted tumors, cells from early transplant generations produced no significant endocrine changes during latency; (iii) irrespective of whether they were primary or transplanted, large tumor burdens caused similar hormonal alterations, consisting of increased corticosterone and growth hormone and decreased insulin, thyroxin, prolactin and sex steroid levels in blood. Our comprehensive longitudinal study demonstrates host endocrine responses during different stages of neoplastic development.

Nutritional factors in human cancers

A variety of external factors interacting with genetic susceptibility influence the carcinogenesis process. External factors including oxidative compounds, electrophilic agents, and chronic infections may enhance genetic damage. In addition, various hormonal factors which influence growth and differentiation are critically important in the carcinogenic process. Diet and nutrition can influence these processes directly in the gastrointestinal tract by providing bioactive compounds to specific tissues via the circulatory system, or by modulating hormone levels. Differences in certain dietary patterns among populations explain a substantial proportion of cancers of the colon, prostate and breast. These malignancies are largely influenced by a combination of factors related to diet and nutrition. Their causes are multifactorial and complex, but a major influence is the widespread availability of energy-dense, highly processed and refined foods that are also deplete in fiber. These dietary patterns in combination with physical inactivity contribute to obesity and metabolic consequences such as increased levels of IGF-1, insulin, estrogen, and possibly testosterone. These hormones tend to promote cellular growth. For prostate cancer, epidemiologic studies consistently show a positive association with high consumption of milk, dairy products, and meats. These dietary factors tend to decrease 1.25(OH)2 vitamin D, a cell differentiator, and low levels of this hormone may enhance prostate carcinogenesis. While the nutritional modulation of growth-enhancing and differentiating hormones is likely to contribute to the high prevalence of breast, colorectal, prostate, and several other cancers in the Western world, these cancers are relatively rare in less economically developed countries, where malignancies of the upper gastrointestinal tract are quite common. The major causes of upper gastrointestinal tract cancers are likely related to various food practices or preservation methods other than refrigeration, which increase mucosal exposure to irritants or carcinogens.

Energy sources and risk of cancer of the breast and colon-rectum in Italy

Dietary habits are thought to be involved as determinant of breast and colorectal cancer. Nevertheless results of epidemiological studies on diet show several inconsistencies. This is true for the findings related to energy and its sources. Between 1991 and 1996, 2569 women with incident breast cancer (median age: 55 years) and 2588 controls (median age: 56 years), and 1953 subjects with cancer of the colon-rectum (median age: 62 years) and 4154 controls (median age: 58 years) were interviewed in the hospitals of six Italian areas. The validated food frequency questionnaire included questions on 78 foods and recipes and specific questions on individual fat intake pattern. Significant risks for breast and colorectal cancer emerged with increasing intake of energy (odds ratios in highest vs. lowest quintile were 1.32 and 1.49 respectively). Due to the high interrelations existing among the various sources of energy, the separated analysis of each macronutrient didn't achieve the independent estimates of the effects. In order to overcome this situation, we used a completely partitioned model in which all the main sources of energy were entered simultaneously as continuous variables in the regression. High intake of starch led to an increase of cancer risk (odds ratios for an addition of 100 kcal/day were 1.08 and 1.10 for breast and colorectal cancer respectively). A positive association was also found for saturated fat (odds ratios 1.16 for breast and 1.12 for colorectal cancer). High intakes of polyunsaturated fatty acids (chiefly derived from olive and seed oils) were protective more markedly for breast cancer. A possible interpretation of the risk for starch, implies the glycemic overload and hyperinsulinemia due to the high grade of refinement of cereals (the main source of starch) eaten in Italy.

Vegan proteins may reduce risk of cancer, obesity, and cardiovascular disease by promoting increased glucagon activity

Amino acids modulate the secretion of both insulin and glucagon; the composition of dietary protein therefore has the potential to influence the balance of glucagon and insulin activity. Soy protein, as well as many other vegan proteins, are higher in non-essential amino acids than most animal-derived food proteins, and as a result should preferentially favor glucagon production. Acting on hepatocytes, glucagon promotes (and insulin inhibits) cAMP-dependent mechanisms that down-regulate lipogenic enzymes and cholesterol synthesis, while up-regulating hepatic LDL receptors and production of the IGF-I antagonist IGFBP-1. The insulin-sensitizing properties of many vegan diets--high in fiber, low in saturated fat--should amplify these effects by down-regulating insulin secretion. Additionally, the relatively low essential amino acid content of some vegan diets may decrease hepatic IGF-I synthesis. Thus, diets featuring vegan proteins can be expected to lower elevated serum lipid levels, promote weight loss, and decrease circulating IGF-I activity. The latter effect should impede cancer induction (as is seen in animal studies with soy protein), lessen neutrophil-mediated inflammatory damage, and slow growth and maturation in children. In fact, vegans tend to have low serum lipids, lean physiques, shorter stature, later puberty, and decreased risk for certain prominent 'Western' cancers; a vegan diet has documented clinical efficacy in rheumatoid arthritis. Low-fat vegan diets may be especially protective in regard to cancers linked to insulin resistance--namely, breast and colon cancer--as well as prostate cancer; conversely, the high IGF-I activity associated with heavy ingestion of animal products may be largely responsible for the epidemic of 'Western' cancers in wealthy societies. Increased phytochemical intake is also likely to contribute to the reduction of cancer risk in vegans. Regression of coronary stenoses has been documented during low-fat vegan diets coupled with exercise training; such regimens also tend to markedly improve diabetic control and lower elevated blood pressure. Risk of many other degenerative disorders may be decreased in vegans, although reduced growth factor activity may be responsible for an increased risk of hemorrhagic stroke. By altering the glucagon/insulin balance, it is conceivable that supplemental intakes of key non-essential amino acids could enable omnivores to enjoy some of the health advantages of a vegan diet. An unnecessarily high intake of essential amino acids--either in the absolute sense or relative to total dietary protein--may prove to be as grave a risk factor for 'Western' degenerative diseases as is excessive fat intake.

Refined-cereal intake and risk of selected cancers in italy

BACKGROUND

Although consumption of whole-grain foods seems to reduce the risk of several types of neoplasms, the potential influence of a diet rich in starches and refined grains is less clear.

OBJECTIVE

We studied the relation between the frequency of consumption of refined cereals (bread, pasta, or rice) and the risk of selected neoplasms.

DESIGN

This was an integrated series of case-control studies conducted in northern Italy between 1983 and 1993. The subjects were patients admitted to the major teaching and general hospitals in Milan and Pordenone with incident, histologically confirmed cancers: 343 with cancer of the oral cavity and pharynx, 94 with cancer of the esophagus, 146 with cancer of the larynx, 745 with cancer of the stomach, 955 with cancer of the colon, 625 with cancer of the rectum, and 428 with cancer of the thyroid. The control subjects were 3526 patients admitted to the same network of hospitals for acute nonneoplastic conditions unrelated to long-term modification of diet. Odds ratios (ORs) for consecutive tertiles of refined-cereal consumption were computed after allowance for sociodemographic variables, education, smoking status, alcohol consumption, body mass index, and consumption of fruit, vegetables, and whole-grain foods.

RESULTS

The ORs for the highest tertile of refined-cereal intake were 1.6 for cancer of the oral cavity, pharynx, esophagus, or larynx; 1.5 for stomach cancer; 1.5 for colon cancer; 1.3 for cancer of the rectum; and 2.0 for thyroid cancer. The trends in risk were significant for all neoplasms considered.

CONCLUSION

Consumption of refined cereals was associated with an increased risk of cancers of the large bowel, the stomach, and other selected digestive and nondigestive sites.

Nutrition in cancer prevention

Although variation in diet may account for approximately one third of the variation in cancer incidence worldwide, epidemiologic studies have proven to be a blunt instrument for identifying causal relationships between intakes of specific food constituents and cancer risk at specific sites. Diets rich in fruits and vegetables seem to be protective, but the adverse effects of beta carotene supplementation trials on lung cancer incidence in smokers caution against the attribution of benefit to single substances. Important diet-gene interactions may exist, as illustrated by differential responses to variation in folate status in those with methylenetetrahydrofolate reductase polymorphisms. Targeting initial intervention studies in those with explicit genetic predisposition to cancer may have both greater cost-effectiveness and fewer ethical difficulties than do similar studies in the general public.

Physical activity, water intake and risk of colorectal cancer in Taiwan: a hospital-based case-control study

The age-adjusted mortality rates of colorectal cancer have been rising in Taiwan over the past 2 decades, and colorectal cancer is now the third leading cause of cancer mortality in the country. We conducted a hospital-based case-control study to clarify the nature of the association between physical activity, water intake and colorectal-cancer risk in Taiwan. A total of 163 subjects (aged 33-80 years) with histologically confirmed primary colorectal cancer and 163 hospital controls were enrolled during 1992. Dietary intake, physical activity and other lifestyle activities were assessed using a comprehensive food-frequency and lifestyle-activity questionnaire. Adjusted odds ratios (OR) and 95% confidence intervals (CI) were estimated using conditional logistic-regression analysis. A strong inverse dose-response relation between increased water intake and rectal cancer was found among men after adjustment for other risk factors (p for trend = 0.0005). The OR for rectal cancer among men in the highest tertile of water intake was 0.08 (95% CI, 0.02-0.35) compared with that among men in the lowest tertile (OR = 1). Similar but not significant trends were seen among women (p = 0.29). The OR for colon cancer among men with active leisure-time physical activity was 0.19 (95% CI, 0.05-0.77) times that among sedentary men (p for trend = 0.03). However, physical activity was not associated with colon-cancer risk among women (p = 0.48). No differences in the amount of water intake were found related to level of physical activity. These findings add to the evidence that leisure-time activity may reduce colon-cancer risk, not only in high-risk but also in low-risk populations, and support the potential beneficial effect of increased water intake in reducing colorectal-cancer risk.

Hypertension and hormone-related neoplasms in women

The relation between hypertension and the risk of selected hormone-related neoplasms in women was investigated in a network of case-control studies conducted in Italy during 1983-1996. Cases were women younger than 75 years with histologically confirmed cancer of the breast (n=3406), endometrium (n=745), ovary (n=970), and thyroid (n=145). Controls were 3054 women admitted in the same geographic area for acute, nonneoplastic, non-hormone-related diseases. Odds ratios (ORs) of treated hypertension were computed after allowance for sociodemographic factors, smoking habits, alcohol consumption, parity, menopausal status, and body mass index (BMI) by means of unconditional logistic regression. The ORs were 1.2 (95% CI, 1.1 to 1.4) for breast cancer and 1.6 (95% CI, 1.3 to 1.9) for endometrial cancer, and the elevated ORs persisted after >/=5 years since diagnosis of hypertension. No significant association was observed for ovarian and thyroid cancer. For breast cancer, the association was apparently stronger at age 55 years or over and consequently after menopause. No appreciable effect modification was evident for endometrial cancer. Allowance for BMI did not explain the association of postmenopausal breast cancer and endometrial cancer with hypertension. The OR of postmenopausal breast cancer was 1.5 (95% CI, 1.1 to 2.0) in hypertensive women with BMI >/=30 kg/m(2) compared with normotensive women with BMI <25 kg/m(2). The corresponding figure for all endometrial cancers was 4.9 (95% CI, 3. 4 to 6.9). Even in the absence of a clear understanding of biological mechanisms, the definition of a role of hypertension on female hormone-related cancers can have relevant implications on individual risk assessment.

Obesity, weight gain and risk of colon adenomas in Japanese men

Obesity has been related to increased risk of colon cancer or adenomas, but the epidemiologic findings are not entirely consistent. We examined the relation of not only body mass index (BMI) but also waist-to-hip ratio (WHR) and weight gain to colon adenoma risk in men who received a preretirement health examination at the Japan Self Defense Forces (SDF) Fukuoka and Kumamoto Hospitals during the period from 1995 to 1996. In the series of 803 men at age 47-55 years, 189 cases of colon adenomas and 226 controls with normal total colonoscopy were identified. Weight at 10 years before was ascertained by referring to the recorded data. After allowance for hospital, rank in the SDF, smoking and alcohol use, weight gain over the past 10 years was significantly associated with increased risk of colon adenomas (odds ratio for > or = 6 kg versus < or =-2 kg = 2.2; 95% confidence interval 1.0-4.8). High BMI and high WHR were each associated with increased risk, but only WHR was related to the risk independently of weight gain. In particular, weight gain accompanied with a high WHR was associated with a significant increase in the risk. Men with high physical activity tended to have lower risk. Associations with obesity-related variables and physical activity were not materially differential as regards the location and size of adenoma. The findings indicate that weight gain in middle age leading to abdominal obesity increases the risk of colon adenomas, and consequently of colon cancer.

Risk factors for adenocarcinoma of the small intestine

We have investigated the relation between alcohol, tobacco and dietary habits and risk of adenocarcinoma of the small intestine using data from 2 hospital-based case-control studies on intestinal cancers conducted in 6 Italian centres between 1985 and 1996. Cases were 23 patients below age 75 years with adenocarcinoma of the small intestine. Controls were 230 patients admitted to hospital for a wide spectrum of acute, non-neoplastic, non-digestive tract diseases, matched to cases on sex, age, study and centre. Odds ratios (ORs) were estimated using conditional logistic regression. Alcohol and tobacco consumption did not increase the risk of adenocarcinoma of the small intestine. The risk appeared to be directly related to intake of bread, pasta or rice (OR = 3.8), sugar (OR = 2.9) and red meat (OR = 4.6), and inversely to coffee (OR = 0.4), fish (OR = 0.3), vegetables (OR = 0.3) and fruit (OR = 0.6). Our results suggest that dietary correlates of adenocarcinoma of the small intestine are similar to those of colon cancer and at least of the same magnitude. While the present data are inconsistent with a major effect of tobacco or alcohol, a moderate association between these factors and small bowel cancer may have been obscured by the play of chance.

Increased blood glucose and insulin, body size, and incident colorectal cancer

BACKGROUND

Abdominal obesity--an elevated level of visceral adipose tissue--has been linked to colorectal cancer. Furthermore, elevated levels of visceral adipose tissue have been associated with hyperinsulinemia, and insulin is a growth factor in the colon. We assessed whether waist circumference, a surrogate measure of visceral adipose tissue, and metabolic parameters associated with visceral adipose tissue were related to colorectal cancer.

METHODS

In the Cardiovascular Health Study cohort, we examined the relationship of baseline measurements of body size, glucose, insulin, and lipoproteins to incident colorectal cancer. All P values are two-sided.

RESULTS

Among 5849 participants, 102 incident cases of colorectal cancer were identified. Individuals in the highest quartile of fasting glucose had a nearly twofold increased risk of colorectal cancer (relative risk [RR] = 1.8; 95% confidence interval [CI] = 1.0-3.1), and the linear trend RR (LT RR = 1.2; 95% CI = 1.0-1.5) for fasting glucose level was statistically significant (P =. 02). Glucose and insulin levels 2 hours after oral glucose challenge also exhibited statistically significant associations with colorectal cancer (2-hour glucose levels: RR = 2.4 [95% CI = 1.2-4. 7]/LT RR = 1.3 [95% CI = 1.0-1.6; P =.02]; 2-hour insulin levels: RR = 2.0 [95% CI = 1.0-3.8]/LT RR = 1.2 [95% CI = 1.0-1.5; P =.04]). Analysis of fasting insulin levels suggested a threshold effect, with values above the median associated with colorectal cancer (RR = 1.6; 95% CI = 1.1-2.4; P =.02). Higher levels of waist circumference were also statistically significantly associated with colorectal cancer (RR = 1.9; 95% CI = 1.1-3.3; P =.02).

CONCLUSIONS

These data provide, to our knowledge, the first direct evidence of an association between elevated visceral adipose tissue level, its associated metabolic effects, and colorectal cancer.

Influence of inulin and oligofructose on breast cancer and tumor growth

Because anticarcinogenic and tumor-growth-inhibiting effects of nonsoluble fibers have been described, similar actions of soluble fibers appear to merit investigation. In a preliminary study on methylnitrosourea-induced mammary carcinogenesis in Sprague-Dawley female rats, 15% oligofructose added to the basal diet modulated this carcinogenesis in a negative manner. There was a lower number of tumor-bearing rats and a lower total number of mammary tumors in oligofructose-fed rats than in the group fed the basal diet alone. The effect of dietary nondigestible carbohydrates (15% oligofructose, inulin or pectin incorporated into the basal diet) on the growth of intramuscularly transplanted mouse tumors, belonging to two tumor lines (TLT and EMT6), was also investigated. The results were evaluated by regular tumor measurements with a vernier caliper. The mean tumor surface in the experimental groups was compared with that in animals of the control group fed the basal diet containing starch as the only carbohydrate. The growth of both tumor lines was significantly inhibited by supplementing the diet with nondigestible carbohydrates. Such nontoxic dietary treatment appears to be easy and risk free for patients, applicable as an adjuvant factor in the classical protocols of human cancer therapy.

Population-attributable risk for colon cancer in Italy

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

Colorectal cancer: molecules and populations

The epidemiology and molecular biology of colorectal cancer are reviewed with a view to understanding their interrelationship. Risk factors for colorectal neoplasia include a positive family history, meat consumption, smoking, and alcohol consumption. Important inverse associations exist with vegetables, nonsteroidal anti-inflammatory drugs (NSAIDs), hormone replacement therapy, and physical activity. There are several molecular pathways to colorectal cancer, especially the APC (adenomatous polyposis coli)-beta-catenin-Tcf (T-cell factor; a transcriptional activator) pathway and the pathway involving abnormalities of DNA mismatch repair. These are important, both in inherited syndromes (familial adenomatous polyposis [FAP] and hereditary nonpolyposis colorectal cancer [HNPCC], respectively) and in sporadic cancers. Other less well defined pathways exist. Expression of key genes in any of these pathways may be lost by inherited or acquired mutation or by hypermethylation. The roles of several of the environmental exposures in the molecular pathways either are established (e.g., inhibition of cyclooxygenase-2 by NSAIDs) or are suggested (e.g., meat and tobacco smoke as sources of specific blood-borne carcinogens; vegetables as a source of folate, antioxidants, and inducers of detoxifying enzymes). The roles of other factors (e.g., physical activity) remain obscure even when the epidemiology is quite consistent. There is also evidence that some metabolic pathways, e.g., those involving folate and heterocyclic amines, may be modified by polymorphisms in relevant genes, e.g., MTHFR (methylenetetrahydrofolate reductase) and NAT1 (N-acetyltransferase 1) and NAT2. There is at least some evidence that the general host metabolic state can provide a milieu that enhances or reduces the likelihood of cancer progression. Understanding the roles of environmental exposures and host susceptibilities in molecular pathways has implications for screening, treatment, surveillance, and prevention.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Cross-country comparisons suggest shared risk factors for carcinomas, including male lung adenocarcinoma and colon cancer development

Smoking is clearly the major risk factor for both squamous cell carcinomas (SCCs) and adenocarcinomas (ACs) of the lung, although less so for the latter, where other influences appear to be important. In order to determine whether cross-country comparisons might provide evidence of shared risk factors with cancers in other organs of males, an examination of IARC/WHO data for cancer incidence was made for countries/registries in Europe, North America, Australia and Asia. Significant simple correlations, which persisted on partial analysis, were observed between lung SCCs and tumors of the larynx (P < 0.001), but not the buccal cavity or oesophagus, along with a link to rectal ACs (P < 0.001). Incidences of lung ACs also correlated with those for colon ACs (P < 0.001) but not lung SCCs. Oesophageal ACs were only related to colon cancers at the simple correlation level, this not persisting on partial analysis or separation into Asian and Western groups. The results suggest that blood borne factors, like hormones, may be important as determinants for the increasingly prevalent lung AC.

Diabetes and endometrial cancer: an Italian case-control study

We considered the association between diabetes and risk of endometrial cancer using data from a large case-control study conducted in Italy. Cases were 752 women with incident, histologically confirmed endometrial cancer < 75 years of age (median age 60 years, range 28-74) admitted to a network of hospitals in Milan. Controls were 2,606 patients (median age 54 years, range 25-74) aged < 75 years, admitted for acute non-neoplastic, non-gynecological, non-hormone-related conditions to the same network of hospitals where cases had been identified. A total of 132 (17.6%) cases and 116 controls (4.5%) reported a history of diabetes. The corresponding multivariate odds ratio (OR) was 2.9 [95% confidence interval (CI) 2.2-3.9]. No association emerged with diabetes diagnosed under age 40 (likely to be insulin-dependent diabetes), whereas the OR of endometrial cancer was 3.1 (95% CI 2.3-4.2) for diabetes diagnosed at age > or = 40 years. The OR of endometrial cancer in women with history of diabetes was 3.0 for women with a body mass index (BMI) (QI) kg/m2 < 25, 3.6 for those with a BMI of 25-29, and 3.3 for those with a BMI > or = 30. No consistent interaction or modifying effect was observed for any other covariate. Our results confirm that non-insulin-dependent diabetes is associated with the risk of endometrial cancer. The association may be mediated through elevated oestrogen levels in diabetic women, hyperinsulinemia or insulin-like growth factor-I (IGF-I).

Prospective study of adult onset diabetes mellitus (type 2) and risk of colorectal cancer in women

BACKGROUND

The remarkable similarity of lifestyle and environmental risk factors for type 2 (non-insulin-dependent) diabetes mellitus and colon cancer has led to the hypothesis that diabetes may increase the risk of this cancer. We prospectively examined the relationship between diabetes and risk of colorectal cancer in a cohort of 118403 women aged 30 through 55 years who were without previously diagnosed cancer at baseline in 1976.

METHODS

The women, who were enrolled in the Nurses' Health Study, were assessed for history of diabetes at baseline and during follow-up by use of biennial questionnaires. Self-reported diabetes was validated by information obtained from a supplemental questionnaire on symptoms and treatment and was confirmed by medical record review in a sample of the participants. Incident cases of colorectal cancer were ascertained through medical record review. All reported P values are two-sided.

RESULTS

During 18 years of follow-up (201061 person-years), we documented 892 new cases of colorectal cancer. After adjustment for age, body mass index (weight in kg/height in m2), physical activity, and other covariates, relative risks (RRs) were 1.43 (95% confidence interval [CI] = 1.10-1.87; P = .009) for colorectal cancer, 1.49 (95% CI = 1.09-2.06; P = .01) for colon cancer, 1.11 (95% CI = 0.56-2.21; P = .76) for rectal cancer, 1.56 (95% CI = 1.07-2.28; P = .02) for advanced colorectal cancer, and 2.39 (95% CI = 1.46-3.92; P = .0005) for fatal colorectal cancer.

CONCLUSION

Our data provide support for the hypothesis that diabetes is associated with an increased risk of colorectal cancer in women.

A dietary trial with a short-term low-sucrose diet in an Italian population: effects on colorectal mucosal proliferation

Colorectal mucosal proliferation is supposed to predict colon cancer risk. We investigated whether a low-sucrose diet might reduce colorectal mucosal proliferation in a group of patients at higher risk of colorectal cancer after at least two colon adenoma resections. In a pilot phase, 14 patients [12 men and 2 women, 60.3 +/- 5 (SD) yr] were instructed to adopt a low-sucrose diet for one month. Colorectal biopsies were taken twice in the same patients, at the start and the end of the intervention period, and mucosal proliferation was measured by [3H]thymidine uptake in vitro and autoradiography. Although compliance of study participants to dietary modification was high, only a few agreed to two consecutive endoscopies; thus we carried out a randomized study, and 107 patients were assigned to a low-sucrose diet (50 treated patients: 31 men and 19 women, 59.7 +/- 7.5 yr) or instructed to continue their usual diet for one month (55 control patients: 32 men and 23 women, 59.6 +/- 7.7 yr). At the end of this period, colorectal biopsies were obtained. The results of the pilot phase and the randomized study showed that a low-sucrose diet for one-month did not affect proliferation or the distribution of proliferation activity along the crypt. The food-frequency questionnaires indicated that treated patients consumed significantly less sucrose (and fewer total calories) during the dietary modification. Urinary fructose, a measure of dietary sucrose intake, was also reduced at the end of the intervention period. In conclusion, we found no evidence that a low-sucrose diet for one month influences colorectal mucosal proliferation.

Marriage of a medium-term liver model to surrogate markers--a practical approach for risk and benefit assessment

The need for a reliable medium-term alternative to traditional long-term rodent test protocols for carcinogen risk assessment is pressing given the immense variety of compounds being developed for introduction into the human environment. The established lack of a complete correlation between mutagenicity and carcinogenicity means that recourse must be made to an in vivo model. Optimally, this model should be able to detect not only complete carcinogenic or promoting potential but also any ability to inhibit neoplasia. In order to be effective, it must take into account the available detailed knowledge on mechanisms of action of carcinogens and modulating agents. The Ito model, for which a uniquely comprehensive set of background data has already been accumulated, has a solid scientific basis; this model utilizes quantitative data for glutathione S transferase-positive foci as the preneoplasia-based surrogate end point (PSE). A very practical candidate for routine application, its predictive power, its flexibility, and its capacity to incorporate a range of mechanism-based surrogate end points (MSEs) provide a powerful tool for attainment of the twin goals of detecting carcinogenic agents and identifying promising chemopreventors.

Positive association between resting pulse and cancer incidence in current and former smokers

PURPOSE

To evaluate the association between resting pulse and cancer incidence in older persons.

METHODS

A cohort of 2819 persons, aged 65 to 102 years at baseline, was followed for the development of cancer from 1982 through 1993 by linkage to a statewide cancer registry; 494 incident cases were identified. Resting radial pulse (beats per minute) was measured during an in-person interview at baseline, and sex-specific quintile cutpoints were used in the analysis.

RESULTS

After adjustment for age, body mass, smoking, and physical activity, there was a positive association between pulse and cancer incidence in men: compared to men with a pulse of < 63, men with a pulse of 63-68 (relative risk (RR); 95% confidence interval (CI): RR = 1.68; CI = 1.06-2.66), 69-74 (RR = 1.54; CI = 0.95-2.49), 75-82 (RR = 1.62; CI = 1.03-2.55), and > 82 (RR = 1.63; CI = 1.03-2.65) were at elevated risk for any cancer. This association remained unchanged after further adjustment for cardiovascular comorbidity, diabetes, alcohol use, high level of depressive symptoms, and low self-perceived health status. Exclusion of cases diagnosed in the first two years of follow-up did not alter the association. There was no overall association between pulse and cancer incidence in women. Analyses stratified by smoking status showed that the pulse and cancer association was strongest in ever smokers for both men and women. In subsite analysis for men, pulse was mainly associated with smoking-related tumors as a group and colorectal and prostate cancer.

CONCLUSIONS

These data suggest that resting pulse is associated with cancer incidence, mainly among ever smokers.

Nutrient intake patterns and gastric cancer risk: a case-control study in Belgium

A case-control study on gastric cancer risk in relation to nutrient composition of diet was conducted in the 2 Belgian provinces of Oost-Vlaanderen and Liège as part of a large epidemiological study on cancers of the digestive tract, also including colorectal cancer. The statistical analysis was carried out on a total of 301 men and women aged 35-74 years with histologically confirmed stomach tumors and 2,851 population controls. Dietary intake assessments were obtained by interview, using a dietary history questionnaire. Gastric cancer risk was increased for diets rich in mono- and disaccharides, according to statistical models based on energy-adjusted residuals [odds ratio (OR) = 1.88 for upper vs. lower quartiles of energy-adjusted intakes] or energy decomposition models, but showed no increase for high intake of polysaccharides. Intake of polyunsaturated fats, particularly linoleic acid, was inversely associated with gastric cancer risk. High intake of vitamin C, beta carotene and vitamins B1 (thiamine), B3 (nicotinic acid) or B6 (pyridoxine) was also associated with decreased risk, whereas increased risk was observed for high intake of vitamin A (retinol) or vitamin B2 (riboflavin). Many of these associations between gastric cancer risk and nutrient composition were similar to those found in the analysis of a parallel study on cancers of the colon and rectum.

Obesity as a risk factor for certain types of cancer

In conclusion, obesity has been associated with increased risk for a number of different types of cancer. The evidence has been most consistent for endometrial cancer, breast cancer in postmenopausal women, and renal cell cancer. More variable results have been reported for colorectal, prostate and pancreatic cancer. Possible mechanisms by which obesity may influence cancer risk include alteration in hormonal patterns, including sex hormones and insulin, and factors such as the distribution of body fat and changes in adiposity at different ages. The increasing prevalence of obesity in many parts of the world emphasizes the importance of learning more about the relationship between obesity and cancer and the mechanisms involved in their interaction.

Dietary sugar and lung cancer: a case-control study in Uruguay

To examine whether dietary sugar modifies lung cancer risk, a case-control study involving 463 cases with lung cancer and 465 hospitalized controls was conducted in Uruguay in the period 1993-1996. Dietary patterns were assessed in detail using a 64-item food-frequency questionnaire, which allowed the calculation of total energy intake. After adjustment for potential confounders through a model that included tobacco smoking and total energy, total fat, vitamin C, and alpha-carotene intakes, an increased risk for sugar-rich foods, total sucrose intake, sucrose to dietary fiber ratio, and glycemic index for lung cancer was observed (odds ratio for highest category of total sucrose intake = 1.55, 95% confidence interval = 0.99-2.44). When lung cancer was analyzed separately by cell type, odds ratios for small cell and large cell undifferentiated carcinoma were higher than those observed for squamous cell and adenocarcinoma of the lung. The joint effect of pack-years, total fat intake, and sucrose intake was associated with an increased risk of 28.3 (95% confidence interval = 13.4-59.7) for high values of the three variables. The study suggests that high sucrose intake could be an important risk factor in lung carcinogenesis. Further studies, both epidemiological and experimental, are needed to replicate the present findings and to clarify the mechanism(s) of sucrose intake in lung carcinogenesis.

Comparative effects of secondary bile acids, deoxycholic and lithocholic acids, on aberrant crypt foci growth in the postinitiation phases of colon carcinogenesis

The objective of this study was to investigate the effect of deoxycholic (DCA) and lithocholic (LCA) acids on the postinitiation phases of colon cancer. Male Sprague-Dawley rats (n = 170) were injected with azoxymethane (2 injections at 15 mg/kg body wt sc given 1 wk apart) and fed a control (CON) AIN-93 diet. Two weeks after the second azoxymethane injection, 10 animals were killed and aberrant crypt foci (ACF) were enumerated. The remaining animals were randomly assigned to four diet groups: 1) CON, 2) DCA, 3) LCA, and 4) high fat (HF, a positive control group). Bile acid diets consisted of 0.2% by weight DCA or LCA; HF diets consisted of 20% fat (5% soybean oil + 15% beef tallow by weight). Animals were killed at Weeks 3, 12, and 20 (from 1st carcinogen injection), and number and growth features of ACF and adenomatous lesions were enumerated in the colon. At Week 12, ACF number and small, medium, and large (1-3, 4-6, and > or = 7 crypts/focus, respectively) ACF were higher in the HF group than in the DCA, LCA, and CON groups (p < or = 0.05). By Week 20, ACF number and small, medium, and large ACF were similar in the LCA and HF groups, whereas the response was similar in the DCA and CON groups. Average crypt multiplicity was higher in the HF and LCA groups than in the DCA and CON groups (p < or = 0.05). Microadenoma (MA) incidence was higher in the HF group than in the CON and LCA groups (p < or = 0.05). Regional distribution patterns for ACF number were similar to MA and tumor distribution patterns within the CON, DCA, and HF groups. In the LCA group, ACF number and MA showed a proximal predominance in regional distribution, whereas tumors showed a distal predominance. HF diets provided the most stimulatory environment, immediately enhancing the number and growth of ACF and MA incidence. In conclusion, HF and LCA diets exerted distinct effects on postinitiation phases of colon cancer, whereas the DCA diet did not.

Body size and colorectal-cancer risk

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

Diet, lifestyle, and colorectal cancer: is hyperinsulinemia the missing link?

Several dietary and other lifestyle factors have been implicated in the development of colorectal cancer. However, the precise nature and actual magnitude of the relationship between individual nutrient intakes and other lifestyle factors and colorectal cancer risk are not clear. A unifying hypothesis has recently been proposed that explains why obesity, physical inactivity, alcohol, and consumption of a typical Western diet increase colorectal cancer risk. This hypothesis suggests that these dietary and other lifestyle factors are associated with insulin resistance and hyperinsulinemia and that hyperinsulinemia, in turn, may stimulate growth of colorectal tumors. Two recently published large prospective epidemiologic studies indicate a significant increase in colorectal cancer risk in subjects with diabetes mellitus, thereby supporting this hypothesis.

Region of birth and black diets: the Harlem Household Survey

OBJECTIVES

This study compared dietary risk factors among Southern-born and other Blacks in Central Harlem.

METHODS

A survey of residents of Central Harlem was used to compute a "healthy diet" score for 621 subjects.

RESULTS

Southern-born respondents had the highest-risk diets. Although their numbers were small, Caribbean-born respondents, particularly those younger than 45 years, had the lowest-risk diets.

CONCLUSIONS

The variation in diets in Central Harlem was considerable, with Southern-born Blacks at highest dietary risk for chronic diseases. These results remain to be tested elsewhere, as does the contribution of other chronic disease risk factors.

Hypertension, antihypertensive drugs, and mortality from cancer among women

OBJECTIVES

To investigate whether hypertension and the use of antihypertensive drugs are associated with mortality from cancer among women.

DESIGN

A prospective study of 11075 women living in Utrecht, the Netherlands, aged 50-65 years at enrolment in a breast cancer screening project (DOM cohort). Women attended screening rounds between 1974 and 1985, during which blood pressure measurements were taken and information on drug use and smoking was ascertained. Since 1974 (median follow-up time 19 years) information on cause of death has been obtained from the patient's general practitioner. Hypertension was defined as a systolic blood pressure > 160 mmHg, a diastolic blood pressure > 95 mmHg, or current use of antihypertensive drugs. Cox regression analysis was used to investigate the association between hypertension (treated and untreated) and total and site-specific mortalities from cancer. The influences of systolic and diastolic blood pressures per 10 mmHg increase for women not using antihypertensive drugs were evaluated. Analyses were adjusted for age, smoking, and body mass index.

RESULTS

In total, 704 women died of cancer and 1633 women left the study area. Hypertensive women had a greater than normal (not statistically significant) total risk of mortality from cancer [hazard ratio (HR) 1.10, 95% confidence interval (CI) 0.93-1.31]. Risks for treated and untreated hypertensive women were similar. Cancer-site-specific analyses revealed a statistically significantly lower mortality from gastrointestinal cancers among untreated hypertensive women (HR 0.64, 95% CI 0.44-0.93), whereas mortality from lung cancer was more prevalent among these women (HR 2.50, 95% CI 1.37-4.59). Mortality from lymphatic and hematopoietic cancers for drug-treated hypertensive women was greater than normal (HR 2.11, 95% CI 1.04-4.28), as was mortality from cancers of the uterus, cervix, and ovary (HR 1.80, 95% CI 1.00-3.26).

CONCLUSION

These results support the hypothesis that, if there is a link between blood pressure and cancer, it is likely to be positive and relatively small (+10%); and applies also to nondrug-treated women. The relation may apply for some types of cancer, but not for others.

Meal frequency and coffee intake in colon cancer

Several studies suggested that frequent eating may increase colon cancer risk. To further clarify this issue, a case-control study was carried out in six areas of Italy on 1,225 incident cases < 75 years of age with histologically confirmed colon cancer and 4,154 control subjects. The controls were hospitalized for acute, nonneoplastic conditions unrelated to long-term dietary modifications. After allowance for education, physical activity, intake of vegetables, and major energy sources, there was a trend of increasing risk with increasing eating frequency (odds ratio for > or = 4 vs. < or = 2 daily meals = 1.24). Coffee intake, which was inversely associated with cancer risk, exerted a modification effect, with an odds ratio of 1.89 for frequent eaters who drank fewer than two cups of coffee per day. Frequent eating increases, whereas high coffee intake decreases, the excretion of bile acids, which are suspected to be carcinogenic to the colon. Thus, it is conceivable that frequent coffee intake may counterbalance the effect of frequent eating.

Diet, nutrients, and gastrointestinal cancer

Tobacco and alcohol use are strong risk factors for cancer of the upper gastrointestinal tract. Saturated fat and red meat intake also appear to increase the risk of colorectal cancer. The strongest and most consistent dietary protective factors for gastrointestinal cancer are vegetables and fruits. Some micronutrients show beneficial effects, but the degree of protection is less than that observed from whole plant foods. Substantial decreases in the morbidity and mortality from gastrointestinal cancer could occur with more widespread adoption of dietary guidelines designed for cancer prevention.

The influence of reproductive and hormonal factors on the risk of colon and rectal cancer in women

A case-control study was conducted between 1992 and 1996 in six Italian areas. It included 537 women with colon cancer, 291 women with rectal cancer and 2081 control women in hospital for acute conditions, unrelated to hormonal or gynaecological diseases. A higher age at menopause was associated with increased colon cancer risk (odds ratio (OR) for > or = 53 years compared with < 50 years = 1.39, 95% confidence interval (CI) 1.04-1.87). Among parous women, a significant trend of decreasing colon cancer risk with increasing number of births was seen for colon (OR for > or = 4 births compared with 1 birth = 0.62, 95% CI 0.42-0.90), but not for rectal cancer. Nulliparous women, however, were at lower risk than women with a single birth, and age at first birth was directly associated with risk. While oral contraceptive use showed no significant influence, ever users of hormone replacement therapy had a reduced risk of rectal cancer (OR = 0.56, 95% CI 0.31-1.01). Thus, the association of colorectal cancer with reproductive and menstrual factors is neither strong nor consistent.

Macronutrient intake and risk of colorectal cancer in Italy

To provide further insight on the relationship between macronutrients and colorectal cancer, overall and by specific subsite(s), we carried out between 1992 and 1996 in 6 Italian areas a case-control study on 1,953 individuals of both sexes with incident colorectal cancer (age range 19-74) and 4,154 controls (age range 19-74) in hospital with acute, non-neoplastic diseases. A validated food-frequency questionnaire was used, including questions on 78 foods or recipes and on individual fat-intake pattern. The risk of cancer of the colon and rectum increased with total energy intake (odds ratio in highest vs. lowest quintile 1.43 and 1.50, respectively). The risk also rose significantly with an increase of starch intake, whereas it moderately decreased with an increase of protein intake. Monounsaturated fat intake appeared uninfluential, while saturated fat intake showed a modest direct association with rectal cancer. Polyunsaturated fat intake was inversely associated with colon cancer risk, particularly with the right colon.