Diet and cancer. Any progress in the interim?

Diet and nutrient factors in colorectal cancer risk

Diet and nutrition are estimated to explain as much as 30%-50% of the worldwide incidence of colorectal cancer. In 2007, the World Cancer Research Fund (WCRF), in conjunction with the American Institute for Cancer Research (AICR), released the second expert report that summarizes the current scientific evidence linking diet to the prevention of cancer. This text provides an expert summary and level of evidence of the research relating diet/nutrients to factors that influence cancers of multiple organs, including colon and rectum, with an important emphasis on global patterns. Specific examples include dietary fat, red and processed meat, and dairy, as well effects of nutrients such as calcium, folate, and vitamin D. Evidence is obtained from ongoing systematic literature reviews conducted by experts in both the United States and Europe. The expert panel applies standard practices to evaluate the strength and quality of individual studies to draw summary conclusions. In 2011, the report was updated to include findings from a series of meta-analyses published in 2010. To complement the WCRF/AICR report, the authors review the evidence favoring the role for diet and nutrition in the etiology of colorectal cancer. Specifically, they have integrated information gained from more recent meta-analyses and high-quality, prospective study findings, some of which have been included in the 2011 updated WCRF/AICR summary.

Correlates between vegetable consumption and gallbladder cancer

The results of several studies indicate that a diet rich in fresh vegetables protects against several common epithelial neoplasms. This probable effect has been related to specific micronutrients contained in vegetables. In the present case-control study a systematic assessment of the relationship between vegetable intake and the risk of gallbladder cancer has been undertaken. The study is of particular interest in order to better understand the quantifying effect of vegetable consumption with regard to gallbladder cancer. One hundred and fifty-three patients with gallbladder cancer and 153 controls with gallstone disease were included. Each patient's consumption of vegetables was assessed by using a food frequency questionnaire. The frequency of vegetable consumption was divided into three levels: > or =3 days/week, 1-2 days/week and no or rare consumption. Participants were divided into three groups according to the level of vegetable intake. Odds ratios and 95% confidence intervals were computed for subsequent levels of vegetable consumption compared with the high level of consumption. A low consumption of vegetables showed an increase in odds ratio for gallbladder cancer for almost all the vegetables studied. A significant inverse trend was observed for green leafy vegetables and gallbladder cancer. An inverse association was observed for amaranth with an OR of 3.45 for the low vs. high level of consumption. Corresponding values were 2.14 for spinach, 1.86 for bathua, 1.02 for bengalgram leaves, 2.26 for cabbage, 3.06 for fenugreek leaves, 1.95 for mustard leaves and 1.44 for radish leaves. An inverse relationship between the risk of gallbladder cancer and the level of vegetable consumption was observed.

Health perceptions and risk behaviors of lung cancer survivors

BACKGROUND

Lung cancer survivors are at an increased risk for recurrence and the development of secondary tumors and other comorbid conditions. However, little is known about lung cancer survivors' risk behaviors and the effect of these behaviors on overall health perceptions.

OBJECTIVE

The purpose of this study was to describe the prevalence of health risk behaviors among non-small cell lung cancer survivors and their relationship perception to overall health.

METHODS

One hundred forty-two survivors of non-small cell lung cancer with a minimum of 5 years disease free completed a battery of questionnaires to assess perception of health status and self-reported risk behaviors (smoking, exposure to secondhand smoke, alcohol use) and weight before and after diagnosis. Urinary cotinine level was used to verify smoking status, and actual height and weight were obtained to determine overweight status (body mass index, >/=25). Descriptive statistics and logistic regression were used to analyze the data.

RESULTS

Seventy percent of participants reported their health as good to excellent. Although 81% quit smoking after diagnosis, 13.4% continued to smoke and 28% reported exposure to secondhand smoke. Approximately half the sample (58%) drank alcohol (16.3% quit after diagnosis) and was overweight (51%). A strong agreement between current smoking and exposure to secondhand smoke was observed. In a multivariate analysis, smoking (odds ratio [OR], 7.02; CI, 2.45 to 20.13), exposure to secondhand smoke (OR, 5.37; CI, 2.42 to 11.95), alcohol use (OR, 9.04; CI, 3.28 to 24.92), and overweight (OR, 8.51; CI, 3.44 to 21.10) were independent predictors of perceived poor health status.

CONCLUSION

Although most lung cancer survivors have made healthy lifestyle changes, a substantial proportion has not. Our findings suggest the need for multiple risk factor interventions to decrease risk behaviors and improve overall health after a cancer diagnosis.

Dietary factors in oral leukoplakia and submucous fibrosis in a population-based case control study in Gujarat, India

OBJECTIVES

To investigate the relationship of specific nutrients and food items with oral precancerous lesions among tobacco users.

DESIGN

A population-based case-control study.

SETTING

Villages in Palitana taluk of Bhavnagar district, Gujarat, India.

SUBJECTS AND METHODS

An interviewer-administered food frequency questionnaire, developed and validated for this population, was used to estimate nutrient intake in blinded, house-to-house interviews. Among 5018 male tobacco users, 318 were diagnosed as cases. An equal number of controls matched on age (+/- 5 years), sex, village, and use of tobacco were selected.

MAIN OUTCOME MEASURES

Odds ratios (OR) from multiple logistic regression analysis controlling for relevant variables (type of tobacco use and economic status).

RESULTS

A protective effect of fibre was observed for both oral submucous fibrosis (OSF) and leukoplakia, with 10% reduction in risk per g day-1 (P < 0.05). Ascorbic acid appeared to be protective against leukoplakia with the halving of risk in the two highest quartiles of intake (versus the lowest quartile: OR = 0.46 and 0.44, respectively; P < 0.10). A protective effect of tomato consumption was observed in leukoplakia and a suggestion of a protective effect of wheat in OSF.

CONCLUSION

In addition to tobacco use, intake of specific nutrients may have a role in the development of oral precancerous lesions.

Dietary correlates of fat intake

Dietary fat intake has been associated with the development of chronic diseases, including heart disease and cancer, in human populations; however, associations demonstrated between disease and fat intake may be confounded by related dietary factors. Therefore, description of the correlates of fat intake in free-living adults may help identify important confounders independent of disease status. In a population of 863 women and 538 men between the ages of 50 and 85 randomly selected from two counties in western New York, we found that most nutrients were correlated with grams of total fat intake including protein, carbohydrates, cholesterol, dietary fiber, retinol, iron, and calcium. Carbohydrates and dietary fiber were not related to the concentration of fat in the diet (% of energy from fat). Alcohol intake was negatively associated with fat concentration for men but not for women. Particularly important for the study of cancers, the antioxidants carotene and ascorbic acid were negatively associated with fat concentration in the diet.

Nutritional risk factors for breast cancer

The observation of large differences in breast cancer rates between countries has led to the hypothesis that excessive intake of dietary fat is an important risk factor for breast cancer in women. Case-control and prospective studies, however, generally have failed to show associations between dietary fat and breast cancer risk. There therefore is only weak evidence that modest reductions in fat intake (for instance to levels of 30% of caloric intake from fat) will reduce breast cancer risk. The possible benefits of lowering fat intake to levels substantially below 30% of calories will need to be tested in a randomized trial. In the meantime, the possible roles of micronutrient imbalances and childhood nutritional factors need to be studied better. Obesity is related to breast cancer in a complex way that suggests that a hormonal correlate of excessive body weight might affect breast cancer growth and metastasis. The potential benefit of intentional weight loss as an adjunct breast cancer treatment deserves further study. Many studies have suggested that drinking alcohol, even at modest levels, might increase breast cancer risk. Because the potential benefits of modest levels of alcohol for cardiovascular disease may outweigh the risk for breast cancer, recommendations for total alcohol abstinence may be premature for women with an average breast cancer risk. Women at unusually high risk for breast cancer who have a lower-than-average risk for cardiovascular disease, however, might make an informed decision to abstain from alcohol intake. Following current dietary advice to increase the amount of fruits, vegetables, and whole grains in the diet while reducing fats is certainly prudent for women to reduce their risk of several chronic disease, but current data points to the somber conclusion that such changes probably will have little effect on breast cancer risk.

5-A-DAY: dietary behavior and the fruit and vegetable intake of Latino children

OBJECTIVES

The purpose of the study was to examine children's intake of fruits and vegetables in relation to the recent national "5-A-DAY" campaign.

METHODS

Four 24-hour dietary recalls per child collected from 205 mothers of 4- to 5-year-old urban Latino children were used to analyze average 5-A-DAY fruit and vegetable consumption and examine associations between 5-A-DAY consumption, nutrient intakes, and eating patterns.

RESULTS

The reported mean servings per day of fruits and vegetables, as defined by 5-A-DAY criteria, were 1.8 and 1.0, respectively, with only 6.8% (n = 14) of the children averaging five or more servings per day. Fruit juice accounted for 36% of 5-A-DAY servings. There were significant linear trends in intake of vitamins A and C, potassium, iron, cholesterol, protein, and fiber across quintiles of 5-A-DAY intake. There were no differences among quintiles in intake of saturated or total fat or in servings from most non-5-A-DAY food groups.

CONCLUSIONS

Latino children's intake of fruits and vegetables falls far short of current recommendations. Fruit juice accounted for a disproportionate amount of 5-A-DAY intake in this population. Sensible 5-A-DAY interventions should take into consideration the existing eating patterns of the target population.

Diet and adenomatous polyp risk

Studies of risk factors for colonic adenomatous polyps have been reported in greater numbers in 1993 than in all previous years combined. This explosion in interest in polyps has not arisen because polyps themselves cause serious illness. They are in the vast majority of cases asymptomatic. However, adenomas have become the surrogate for colon cancer in a number of phase III dietary intervention trials. These trials were undertaken at a time when very little was known of adenoma risk factors. Data accumulated in the past 18 months in general demonstrate a similarity in risk factors for cancer and polyp. Since it has also been recently established that polypectomy diminishes colon cancer risk, the adenomatous polyp has been established as an ethical and convenient surrogate for cancer of the colon. Prevention of colorectal cancer is the goal of all the above studies, and it is hoped that the dietary intervention trials currently under way will generate the data that will make prevention possible.

Assessment of the reliability of a diet history questionnaire

The purpose of this study was to estimate the reliability of a self-administered food frequency questionnaire developed at the National Cancer Institute (NCI) (Bethesda, MD). Food intake information was collected from 48 women with breast cancer and 50 women who had a familial breast cancer risk. These women were participants in a long-term investigation of diet and breast cancer at the Ohio State University (Columbus, OH). Pearson correlation coefficients were obtained for 29 nutrients. The effect of time between questionnaires, age, weight, and caloric intake was also examined. The results showed moderate reliability coefficients for most of the nutrients (r = 0.5-0.8). For the majority of nutrients, the women with breast cancer had higher coefficients than did the high-risk women. High-risk women with shorter elapsed time periods between the first and second questionnaire had higher reliability coefficients as did women who consumed fewer calories. Age and weight (standardized by height) showed no effect on reliability. Recommendations for improving the NCI questionnaire in addition to using it as a standard method of measuring food intake are discussed.

Dietary glutathione intake in humans and the relationship between intake and plasma total glutathione level

Glutathione may function as an anticarcinogen by acting as an antioxidant or by binding with cellular mutagens. Orally administered glutathione increases plasma glutathione levels, and plasma glutathione is also synthesized in the liver. To investigate the associations between glutathione intake and plasma glutathione level, we compared dietary intake estimates from food frequency questionnaire data and measured concentrations of plasma total glutathione and other serum antioxidants in 69 white men and women. Daily glutathione intake ranged from 13.0 to 109.9 mg (mean 34.8 mg). Fruits and vegetables were found to contribute over 50% of usual dietary glutathione intake, whereas meats contributed less than 25%. Small negative correlations were observed between dietary and plasma glutathione and, although they were usually not statistically significant, they were generally consistent by different time periods of dietary intake assessment. Adjustment for sex, age, caloric intake, and dietary intake of the sulfur-containing amino acids methionine and cystine did not alter the observed associations. The correlations appeared to be modified, however, by serum vitamin C concentration, with little or no association between dietary and plasma glutathione among those with lower levels of serum vitamin C and stronger negative correlations among those with higher serum vitamin C levels. These findings indicate that factors regulating plasma glutathione concentration are complex and not simply related to dietary glutathione intake or supply of precursor amino acids.

Trends in cancer mortality in young adults in Europe, 1955-1989

Trends in mortality in the age group 20-44 years for the 16 most common cancers or groups of cancer in young adults are presented for 24 European countries (i.e. those with > or = 1,000,000 inhabitants). The largest (up to 9-fold) and most frequent increases were recorded for cancer of the mouth and pharynx (> or = 2-fold increase from 1955-1959 to 1985-1989 in 10 countries), and oesophagus (in eight countries) in males, and for cancer of the skin, chiefly of melanomatous type, in males and females (in nine and eight countries, respectively). Consistent declines were observed for cancer of the stomach and uterus (chiefly, cervix), and for Hodgkin's disease, most notably in northern European countries. Little change emerged in the last 30 years or so in young adult mortality rates for cancer of the colon-rectum, pancreas, non-Hodgkin's lymphoma, leukaemias and cancers of the breast and ovaries in women. More than 2-fold elevations in lung cancer mortality rates in men aged 20-44 years were found only in a few previously non-market economy countries, and in Spain and Portugal. In some northern European countries, favourable downward trends in young males were accompanied by more than 2-fold increases in lung cancer mortality rates in young women. Overall, total cancer mortality rates in women at aged 20-44 years have declined over the last 35 years by more than 20% in 12 countries, and have not increased anywhere. Total cancer mortality rates in young males showed similar decreases in nine northern European countries, but increases of the same magnitude were also observed in most formerly non-market economy countries, and in Spain and Portugal.

A cross-national investigation of diet and bladder cancer

The existence of a large unexplained portion of attributable risk, and the marked variation in bladder cancer rates globally, have stimulated an interest in the role of nutrition in cancer of the urinary bladder. For this cross-national comparison study, we had complete data available for 50 countries. Using stepwise regression followed by general linear modelling, age-truncated (45-74 years), world-standardised, sex-specific bladder cancer mortality rates were regressed on an array of nutritional and socioeconomic independent variables in an effort to identify important predictors of bladder cancer mortality. Separate principal components analyses were used to summarise the nutritional and the socioeconomic (SES) variables. In the stepwise analyses, using food scores expressed in kcal/day per capita (as opposed to the nutritional components), total fat consistently entered the model first, and explained the greatest share of variability (R2) for both males and females. General linear models were fitted that included total fat, tobacco, alcohol, the three SES components (comprising seven socioeconomic predictors) and two food categories found significant in stepwise modelling, roots/tubers and vegetable oil. The R2 values were 0.84 for male rates and 0.77 for female rates, meaning that these study factors account for 84% of bladder cancer mortality in men and 77% in women. Substitution of the nutritional components for the foods resulted in general linear models with slightly higher R2 values (0.85 for males, 0.77 for females), but with attenuated fat effects. Results are discussed in light of biological plausibility.

A work-site nutrition intervention: its effects on the consumption of cancer-related nutrients

OBJECTIVES

In a work-site nutrition intervention targeting fat and fiber, we examined the intervention's effect on specific nutrients implicated in carcinogenesis, including trace metals, vitamins, and categories of fatty acids. The rationale was based on the association observed in a variety of epidemiologic studies between these nutrients and epithelial cancers.

METHODS

Data were taken from eight control companies and five intervention companies that fully implemented the Treatwell intervention. Analyses of variance were used preserving the study's nested design.

RESULTS

Significant intervention-related associations were observed for increased total vitamin A and carotene. Marginal intervention effects were observed for relative decreases in the percentage of calories from both saturated and monounsaturated fatty acids, a relatively smaller increase in the percentage of calories from polyunsaturated fatty acids, and an increase in the consumption of vitamin B6.

CONCLUSIONS

Results indicate a broader effect of the intervention than on fat and fiber only. Increased intake of carotene, the single most important of these other nutrients, is plausibly related to a variety of epithelial cancers.

Dietary factors related to colorectal neoplasms

Although the etiology of colorectal cancer is multifactorial, experimental evidence suggests a role for dietary factors in the promotion of this disease. The complex interrelations governing energy balance and the consumption of fat, fiber, and micronutrients make it difficult to define the precise role of specific dietary factors in the etiology of colorectal neoplasms. Epidemiologic studies have demonstrated a correlation between the prevalence of colorectal cancer and per capita consumption of meat and fat. Case-control studies investigating the relation between colorectal cancer and dietary fat consumption have yielded inconsistent results. Prospective studies have failed to demonstrate a relation between fat consumption and subsequent risk for colorectal cancer. There is an inverse correlation between fiber intake and the prevalence of colorectal carcinoma. A more detailed analysis of the influence of various types of dietary fiber on the subsequent risk for colorectal cancer will provide a better understanding of this relation. Fiber derived from fruits and vegetables may provide more effective protection than cereal fibers. Correlational studies have established an association between total caloric intake and the prevalence of colorectal carcinoma. The design of future studies investigating the influence of individual dietary constituents on the risk for colorectal cancer must control for variations in energy balance as a confounding variable. Recent evidence suggests that a variety of micronutrients, including calcium, vitamin D, selenium, and vitamins A, C, and E, exert an anticarcinogenic effect. Studies designed to evaluate the influence of alcohol consumption on colorectal carcinogenesis have yielded inconclusive results. The potential influence of food preparation methods on colorectal carcinogenesis requires further evaluation. There is no conclusive evidence to support any of the hypotheses proposed to explain the role of dietary factors in colorectal carcinogenesis. Intervention trials designed to monitor intermediate markers for colorectal cancer such as increased epithelial-cell proliferation rates and the development of aberrant crypt architecture provide the opportunity for testing these hypotheses in relatively short-term studies. The results from such studies can be utilized in the design of large-scale, long-term prospective studies to evaluate the influence of dietary factors on the development of colorectal neoplasms. These trials should generate the information required to develop strategies for diet modification to reduce the incidence of colorectal carcinoma.

Education and cancer risk

BACKGROUND

Socioeconomic factors have been associated, to a variable degree, with the risk of serious cancers.

METHODS

The relationship between education and cancer risk was analyzed using data from a series of case-control studies conducted in northern Italy between 1983 and 1990, including 119 histologically confirmed cancers of the oral cavity and pharynx, 294 of the esophagus, 564 of the stomach, 673 of the colon, 406 of the rectum, 258 of the liver, 41 of the gallbladder, 303 of the pancreas, 149 of the larynx, 2860 of the breast, 692 of the cervix, 567 of the corpus uteri, 742 of the ovary, 107 of the prostate, 365 of the bladder, 147 of the kidney, and 120 of the thyroid, 72 Hodgkin diseases, 173 non-Hodgkin lymphomas, 117 myelomas, and a total of 6147 control subjects admitted to the same network of hospitals for acute, non-neoplastic conditions.

RESULTS

Nine types of cancer were inversely related to education. Those were oral cavity and pharynx, with a relative risk (RR) of 0.3 for the highest versus the lowest level; esophagus, RR = 0.6; stomach, RR = 0.5; liver, RR = 0.7; gallbladder, RR = 0.5; larynx, RR = 0.3; cervix, RR = 0.7; endometrium, RR = 0.5; and non-Hodgkin lymphomas, RR = 0.6. Five cancer sites were directly related to education: colon, RR = 1.3; pancreas, RR = 1.3; breast, RR = 1.5; kidney, RR = 1.3; and thyroid, RR = 1.5. No consistent gradient in risk with education was observed for the six other neoplasms considered, including rectum, prostate, bladder, Hodgkin disease, and multiple myeloma. The patterns of risk for education were consistent in men and women for most cancer sites except colon, for which the direct relationship was stronger in males.

CONCLUSIONS

This study confirms the existence of and quantifies a number of strong socioeconomic correlates of cancer risk and indicates a few points open to additional investigation, such as the different pattern of risk for rectal and colon cancer, the strong negative gradient for endometrial cancer, and the absence of any clear association with education for cancers of the ovary, prostate, urinary tract, lymphomas, and myeloma.

Estimates of costs and effects of screening for colorectal cancer in the United States

BACKGROUND

In many ways, colorectal cancer might be an excellent candidate for mass screening because of the following: (1) it is the second leading cause of cancer mortality in the United States; (2) it develops slowly from a precursor lesion; and (3) methods of early detection are available. Barriers to screening include unproven efficacy of the procedure and high costs.

METHODS

Cost analyses are derived from two mathematic models that estimate screening costs and effects based on expert opinion and data from uncontrolled screening studies.

RESULTS

One screening option that follows the guidelines of the American Cancer Society and the National Cancer Institute (annual testing for occult fecal blood and sigmoidoscopy every 5 years) could result in a 40% decrease in colon cancer mortality for American adults between the ages of 50 and 75 years if they comply with screening. This model, developed by David Eddy, projects an average of 44 days of extra life per person screened, at a net cost of $57 per day of life gained. Using assumptions much less favorable to screening, the Office of Technology Assessment modeled this same screening strategy for those aged 65 years and older. This model predicted a similar benefit of extra life per person at a cost of $118 per day of life gained. This doubling of the predicted cost was caused by the inclusion of subsequent colonoscopic surveillance costs for those found to have polyps. Direct costs of screening annually for fecal occult blood and every 5 years by sigmoidoscopy would cost an average of approximately $48 per person per year for screening and follow-up testing of all positive results. Fecal occult blood testing alone, although less effective, costs only $20 per person per year, including follow-up testing of all positive findings.

CONCLUSIONS

The results from randomized trials of fecal occult blood screening will be known in the next 5 years, but trials of screening with sigmoidoscopy will not be complete for 10-15 years. Because mass screening programs will be difficult to fund without better data on their efficacy, colorectal cancer screening will continue to be a matter of individual decision making in the clinical setting for years to come. Clearer presentations of costs and benefits that can be understood by both patients and physicians are needed.

Family history and the risk of stomach and colorectal cancer

BACKGROUND

The role of a family history of selected neoplasms in first-degree relatives in the risk of gastrointestinal cancers has been investigated, but requires further quantification.

METHODS

A case-control study was conducted in northern Italy on 628 histologically confirmed incident cases of stomach cancer, 766 cases of colon cancer, 456 cases of rectal cancer, and 1766 controls admitted to hospital for acute, nonneoplastic, non-digestive tract disorders.

RESULTS

Significant associations were observed between a family history of gastric cancer and stomach cancer risk (relative risk [RR], 2.6), and between a family history of intestinal cancer and colon (RR, 2.4) and rectal cancer (RR, 1.7). There was a tendency for the risks to be above unity for a family history of stomach cancer and for a number of other cancer sites (including esophagus, intestines, liver, pancreas, gallbladder, and lung), and the RR were of borderline statistical significance for cancer of the liver and intestines. The RR for a family history of lung cancer was 1.5 for stomach, 1.2 for colon, and 1.3 for rectal cancer, with none of the estimates being significant. There was no consistent pattern of risk with reference to the type of first-degree relationship; the RR was similar for stomach cancer with reference to parents and siblings, and for colon and rectal cancer, it was only moderately higher with reference to siblings. Significant trends in risk with the number of first-degree relatives were observed for all three cancer sites investigated.

CONCLUSIONS

In terms of population attributable risk, approximately 8% of stomach cancers and 3% of colorectal cancers would be related to this familial component.

Differences in dietary intake with smoking, alcohol, and education

Differences in the frequency of consumption of 30 selected foods and in the estimated intake of total calories and selected nutrients in relation to alcohol drinking, tobacco smoking, and education were described using information obtained from 1,774 controls of a case-control study of digestive tract cancers conducted in northern Italy. Heavy alcohol consumption, tobacco smoking, and lower level of education were associated with a diet poorer in several aspects, including lower consumption of fresh fruit and green vegetables and higher intake of specific indicator foods, such as sausages and canned meat. For instance, the mean number of portions of fresh fruit per week was 10.5 among male nondrinkers vs. 9.0 among heavy drinkers, 10.4 among male nonsmokers vs. 8.1 among heavy smokers, and 8.8 in less educated individuals vs. 10.7 among those more educated. Consequently, intake of beta-carotene, ascorbic acid, and calcium tended to be inversely related to alcohol and tobacco and directly related to education. Most associations were stronger in males, for whom alcohol consumption was also more common in less educated individuals. Calorie intake was directly related to alcohol consumption, largely reflecting calories provided by alcohol itself. However, alcohol drinking was also directly related to fat consumption. In both sexes, there was a strong positive correlation between cigarette smoking and coffee drinking. These results provide quantitative documentation that alcohol drinking, tobacco smoking, and education, three of the major determinants of cancer risks, were also correlates of dietary patterns and, hence, may exert an important confounding or modifying effect on the diet and cancer relationship.

Diet, smoking, and alcohol in cancer of the larynx: a case-control study

A case-control study among white men in western New York was conducted from 1975 through 1985 to examine diet and other risk factors for laryngeal cancer. Incident pathologically confirmed cases (250) and age- and neighborhood-matched controls (250) were interviewed to determine usual diet and lifetime use of tobacco and alcohol. Cigarettes were strongly associated with risk; pipes and cigars were not. Beer and hard liquor but not wine were associated with increased risk. Dietary fat and carotenoids were related to risk in opposite ways. The upper quartile odds ratio for dietary fat was 2.40 [95% confidence interval 1.26, 4.55], and the upper quartile odds ratio for carotenoids was 0.51 (0.26, 1.01). There was effect modification by smoking. Carotenoids were most negatively associated with risk among the lightest smokers, whereas dietary fat was most positively associated with risk among the heaviest smokers. Total calories, protein, and retinol were associated with increased risk; there was no relationship between laryngeal cancer and vitamin C, vitamin E, carbohydrate, or dietary fiber. This study again demonstrates the strong association between tobacco and alcohol and laryngeal cancer and also suggests that diets low in carotenoids and high in fat may increase risk.

Glutathione in foods listed in the National Cancer Institute's Health Habits and History Food Frequency Questionnaire

Glutathione (GSH) is an antioxidant and anticarcinogen that is present in plant and animal tissues that form the bulk of the human diet. Recent studies show that GSH is absorbed intact in rat small intestine and that oral GSH increases plasma GSH concentration in humans. To provide a database for epidemiological studies of dietary intake of GSH and risk of diseases in humans, we have measured the content of GSH in the foods listed in the National Cancer Institute's Health Habits and History Questionnaire. Foods were purchased in the Atlanta area and prepared as most commonly consumed in the United States. GSH analyses were performed using a high-performance liquid chromatography technique with a method of additions to correct for losses during sample preparation. A separate set of samples was run after treatment with dithiothreitol to measure the total of GSH and its disulfide forms (GSH). The results show that dairy products, cereals, and breads are generally low in GSH; fruits and vegetables have moderate to high amounts of GSH; and freshly prepared meats are relatively high in GSH. Frozen foods generally had GSH contents similar to fresh foods, whereas other forms of processing and preservation generally resulted in extensive loss of GSH. Thus this database will allow researchers to examine the relationship between dietary GSH and risk of cancers and other diseases.

Diet and bladder cancer in Spain: a multi-centre case-control study

A multi-centre case-control study on bladder cancer and diet was carried out in 5 regions of Spain. We report results on 432 male cases and 792 matched controls. Usual dietary habits were investigated by means of an interview-based dietary history questionnaire. Bladder-cancer cases were selected from the registers of 12 hospitals located in the study areas. Each case was matched by sex, age and area of residence to 2 controls, one identified in the same hospital and one drawn from population lists. Descriptive analyses indicated that the average dietary pattern was typical of Mediterranean populations: a high P/S ratio, high intake of fish, fruits and vegetables and moderate or low intake of meat and dairy products. Relative risks for specific foods and nutrients were adjusted for tobacco smoking and energy intake. Subjects in the highest quarter of intake of saturated fat had a significantly increased risk of bladder cancer (RR for highest quarter = 2.25; 95% CI = 1.42 to 3.55). Moderate increases in risk for high intake of mono-unsaturated fats and calcium, and a slight decrease for iron were also found, but these disappeared after adjustment for saturated fat. Intake of vitamin E was related to slightly reduced risk (RR for highest quarter = 0.72; 95% CI = 0.48 to 1.09) which was not modified by adjustment for fat. No association was found with intake of retinol or carotene. These results, along with those of previous studies, suggest that saturated fat intake may influence the occurrence of bladder cancer.

Vegetable and fruit consumption and cancer risk

The relationship between cancer risk and frequency of consumption of green vegetables and fruit has been analyzed using data from an integrated series of case-control studies conducted in northern Italy between 1983 and 1990. The overall dataset included the following histologically confirmed cancers: oral cavity and pharynx, 119; oesophagus, 294; stomach, 564; colon, 673; rectum, 406; liver, 258; gall-bladder, 41; pancreas, 303; larynx, 149; breast, 2,860; endometrium, 567; ovary, 742; prostate, 107; bladder, 365; kidney, 147; thyroid, 120; Hodgkin's disease, 72; non-Hodgkin lymphomas, 173; myelomas, 117; and a total of 6,147 controls admitted to hospital for acute non-neoplastic conditions, unrelated to long-term dietary modifications. Multivariate relative risks (RR) for subsequent tertiles of vegetable and fruit consumption were derived after allowance for age, sex, area of residence, education and smoking. For vegetables, there was a consistent pattern of protection for all epithelial cancers, with RRs in the upper tertile ranging from 0.2 for oesophagus, liver and larynx to 0.7 for breast. All the trends in risk were in the same direction and significant for all carcinomas except gall-bladder. In contrast, no protection was afforded by high vegetable consumption against non-epithelial lymphoid neoplasms. With reference to fruit, strong inverse relationships were observed for cancers of the upper digestive and respiratory tract, with RRs in the upper tertile between 0.2 and 0.3 for oral cavity and pharynx, oesophagus and larynx relative to the lowest tertile. The lower the location of the tumour in the digestive tract, the weaker appeared to be the protection afforded. Significant inverse relationships were observed for liver, pancreas, prostate and urinary sites, but not for rectum, breast and female genital cancers or thyroid. No relationship emerged for lymphomas and myelomas. Even in the absence of a clear biological interpretation, the consistency and strength of the patterns observed indicate that, in this population, frequent green vegetable intake is associated with a substantial reduction of risk for several common epithelial cancers, and that fruit intake has a favourable effect, especially on upper digestive cancers and, probably, also on urinary tract neoplasms.

Nutrition and breast cancer

International comparisons have provided striking correlations between fat consumption and risk of breast cancer, but these comparisons do not often consider variations in life style. Case-control studies carried out in several countries showed no real association between fat intake and breast cancer. There is some evidence that vitamin A or carotenoid intake may exert a protective effect. Alcohol intake, on the other hand, seems to be positively associated with breast cancer risk. Elevated body weight, body mass, stature, and frame size have been found to be associated as risk factors for breast cancer in women. Animal studies found that caloric restriction inhibits growth of spontaneous and induced mammary tumors, an observation that held up even when the calorie-restricted animals ingest more fat than the ad-libitum-fed controls. College women who exercise have a lower incidence of breast cancer than their more sedentary classmates. Exercise is another means of reducing caloric availability.

Fiber and cancer

The role of dietary fiber in colon cancer is still not clear. Ecological studies suggested a protective role for high fiber intake, but more recent analysis shows similar intakes of dietary fiber in populations with high or low incidence of colon cancer. Case-control studies generally do not support a protective role for fiber. The data suggest that the effects of fiber must be considered in the context of the total diet and interactions of dietary components. A role for levels of energy intake is not excluded.

Comparison of diet history interview and self completed questionnaire in assessment of diet in an elderly population

STUDY OBJECTIVE

The aim of the study was to determine the reliability of a diet history interview with a short self completed questionnaire of a basic design used in other studies in the United Kingdom.

DESIGN

The study used a cohort of elderly people randomly divided into two groups after stratification for sex. Members of one group completed the questionnaire first and were interviewed later; the procedure was reversed for the other group.

SETTING

Participants were drawn from registers of two general practitioners at a Nottingham health centre.

PARTICIPANTS

All non-Asian men aged 65-74 years and women aged 59-65 years registered with the practices were identified (n = 152); 20 could not be traced and two were too ill, leaving 130 possible participants. Of these, 80 took part in the study.

MEASUREMENTS AND RESULTS

Ranking of subjects in terms of estimated fat, fibre, and calcium intakes was compared in the history interview and in the self completed questionnaire. Agreement in tertile ranking was 58% for fibre, 53% for fat, and 49% for calcium. Corresponding correlation coefficients for estimated nutrient intakes were 0.49, 0.45, and 0.41 respectively. The differences in nutrient intakes estimated by the two methods were not affected by age, sex, marital status, or smoking patterns. Subjects in the group asked to complete the questionnaire before being interviewed showed greater percentage concordance for tertile ranking, but this reached significance only for fat intake.

CONCLUSIONS

The two methods provide estimates of intakes similar to those found in other studies in the United Kingdom, and the agreement between them in terms of tertile ranking is also similar to previous studies. The incidence of gross misclassification was low.

Fatty acid composition of phospholipids in erythrocyte membranes and risk of breast cancer

Five fatty acids (FA) 2 saturated, palmitic (C16:0), stearic (C18:0) and 3 unsaturated, oleic (C18:1), linoleic (C18:2), arachidonic (C20:4) acids have been studied in the red cell membranes of breast cancer patients and controls. Statistically significant decrease in the risk of breast cancer has been found to be associated with increase in the levels of linoleic acid in pre-menopausal women and of arachidonic acid in the post-menopausal group.

Environmental diseases of the digestive system

Environmental factors are important mediators of many diseases of the digestive system, defined as the alimentary tract and the accessory organs of digestion, the liver and pancreas. In this review, we principally focus on the action of chemical agents which are classified as (1) naturally occurring compounds, (2) occupational hazards, (3) therapeutic drugs, and (4) constituents of substances of abuse. In addition, the putative role of dietary habits in the pathogenesis of malignant diseases of the digestive system is discussed.

Human carcinogens so far identified

The massive exploitation of natural resources, of which tobacco and asbestos are two conspicuous, though very different examples, and the synthesis of industrial chemicals have generated new hazards and new carcinogens which have been added to older ones. The majority of the over 50 agents that have been firmly identified so far as being human carcinogens belong to the relatively new hazards, that is environmental chemicals or chemical mixtures to which humans have been exposed only during the last century and a half. They are of more importance for cancer occurring in men than in women, and there is no evidence so far that they are related to cancers occurring at some of the most common target sites in either sex. It would be mistaken to believe that complete cancer prevention could be achieved solely by controlling these new, or relatively new, carcinogenic agents, but it would be similarly wrong to deny the importance of trying to control them and of continuing to do so. The experimental approach for the identification of carcinogens has an irreplaceable role to play in preventing the dispersal into our environment of new hazards and in identifying among the chemicals already in use, those that are carcinogenic. That a closer integration between the epidemiological and the experimental approaches may succeed in substantially reducing the size of the unknown region within the spectrum of cancer-causing factors, is today's hope that awaits confirmation. At the same time, advances in the understanding of the mechanisms underlying the different steps of the process leading to the clinical manifestation of cancer may help in the uncovering of agents and risk factors that the approaches used, at least in the way they have been used until now, may not have been apt to identify.

Clinical trials in diet and cancer

Clinical trials in diet and cancer have special problems. We distinguish between a nutritional supplementation and a dietary intervention trial. Since the latter involves a lifestyle modification the intervention requires more careful planning. To illustrate, the method used to reduce the fat intake of subjects in the Women's Health Trial is described. Any clinical trial should satisfy three basic criteria before initiation: plausibility of hypothesis, feasibility, and justifiable cost. In diet and cancer the plausibility of a hypothesis is often controversial. Our conventional reliance on evidence from case-control and cohort studies for judging the plausibility of dietary hypotheses may be misplaced. Errors in the assessment of individuals' diets and the difficulties of separating the effects of highly correlated dietary variables impose severe limitations on the ability of these studies to elucidate the possible effects of diet on cancer incidence. It is therefore unlikely that a consistent pattern of results will be found. Randomized intervention trials, although expensive, have several advantages over analytic epidemiological studies. For example, whereas dietary assessments are required in epidemiological studies to establish a relationship, in intervention trials they are needed only to explain the relationship. We conclude that there is a serious need for reconsidering the relative importance of evidence from various kinds of epidemiological studies relating to diet and cancer.