Vegetables, fruit, and cancer prevention: a review

Soyfoods, isoflavones and risk of colonic cancer: a review of the in vitro and in vivo data

Soy foods and soybean components have received considerable attention of late for their potential role in reducing cancer risk. Although the relationship between soy intake and the risk of breast and prostate cancer has been the focus of most interest, the relationship between soy intake and other cancers, including colorectal cancer, has also been studied. Several anti-carcinogens have been identified in soybeans, but most enthusiasm for the potential anti-cancer effects of soy undoubtedly stems from work involving soybean isoflavones. Isoflavones have a limited distribution in nature, and, for practical purposes, soyfoods are the only nutritionally relevant dietary source of these phytochemicals. Isoflavones are weak oestrogens but possess other potentially important biological attributes independent of their ability to bind to the oestrogen receptor. The isoflavone genistein inhibits the growth of most types of hormone-dependent and hormone-independent cancer cells in vitro, including colonic cancer cells. Several mechanisms for the in vitro anti-cancer effects of genistein have been proposed, including effects on signal transduction. A number of epidemiological studies, primarily of Asian origin, have examined the relationship between soy intake and the risk of colorectal cancer. Although these studies provide little support for a protective effect of soy, concerns have been raised about the completeness of the soy intake data, since soy was not the focus of these studies and most of this research was conducted prior to the recent interest in the anti-cancer effects of soy. The effect of soy/isoflavone intake has also been studied in rodents, but again these data are conflicting and provide only modest support for a protective effect. Although the relationship between soy intake and colonic cancer risk is certainly worthy of further investigation, there is, at the moment, very limited support for soy exerting a protective effect against this type of cancer.

Demographic and psychosocial predictors of fruit and vegetable intakes differ: implications for dietary interventions

OBJECTIVE

The National Cancer Institute (Rockville, Md) has launched a nationwide initiative--5 A Day for Better Health--to encourage consumption of fruits and vegetables. Because the tastes and culinary uses of fruits and vegetables differ, however, it is not known whether a general 5-A-Day message is an effective intervention strategy. This study examined whether there are differences between the demographic and psychosocial correlates of fruit and vegetable intakes.

DESIGN

Data are from the Washington State Cancer Risk Behavior Survey (1995-1996), a cross-sectional, random-digit-dial telephone survey representative of the adult population of Washington State.

SUBJECTS/SETTING

Interviews were completed with 1,450 adults. Data were collected about demographic characteristics, health status, health-related behavior, fruit and vegetable intakes, and the following diet-related psychosocial factors: beliefs, motives, barriers, attitudes, and stages of dietary change.

STATISTICAL ANALYSES

Multivariate linear regression analysis was used to test whether the associations of demographic characteristics and psychosocial factors with fruit intake differed from associations with vegetable intake.

RESULTS

In general, health status, health-related behavior, and psychosocial factors were more strongly associated with fruit intakes than vegetable intakes. For example, regular exercisers consumed 0.44 more daily servings of fruits and 0.36 more servings of vegetables than nonexercisers. Compared with those in the preaction stage of dietary change, adults in the maintenance stage consumed 0.99 more daily servings of fruits and 0.68 more servings of vegetables. Intrinsic motivations for eating a healthful diet (eg, to feel better) were strongly associated with both fruit and vegetable intakes, and these associations were stronger for fruit. Extrinsic motivations were not associated with either fruit or vegetable intakes.

APPLICATIONS

Dietary interventions based on a general 5-A-Day message may be more effective in increasing fruit intakes than vegetable intakes. Targeted interventions that focus specifically on vegetables are probably necessary. Intrinsic motives for eating a healthful diet should be key components of interventions to increase fruit and vegetable intakes.

Serum antioxidant capacity is increased by consumption of strawberries, spinach, red wine or vitamin C in elderly women

It is often assumed that antioxidant nutrients contribute to the protection afforded by fruits, vegetables, and red wine against diseases of aging. However, the effect of fruit, vegetable and red wine consumption on the overall antioxidant status in human is unclear. In this study we investigated the responses in serum total antioxidant capacity following comsumption of strawberries (240 g), spinach (294 g), red wine (300 ml) or vitamin C (1250 mg) in eight elderly women. Total antioxidant capacity was determined using different methods: oxygen radical absorbance capacity (ORAC) assay, Trolox equivalent antioxidant capacity (TEAC) assay and ferric reducing ability (FRAP) assay. The results showed that the total antioxidant capacity of serum determined as ORAC, TEAC and FRAP, using the area under the curve, increased significantly by 7-25% during the 4-h period following consumption of red wine, strawberries, vitamin C or spinach. The total antioxidant capacity of urine determined as ORAC increased (P < 0.05) by 9.6, 27.5, and 44.9% for strawberries, spinach, and vitamin C, respectively, during the 24-h period following these treatments. The plasma vitamin C level after the strawberry drink, and the serum urate level after the strawberry and spinach treatments, also increased significantly. However, the increased vitamin C and urate levels could not fully account for the increased total antioxidant capacity in serum following the consumption of strawberries, spinach or red wine. We conclude that the consumption of strawberries, spinach or red wine, which are rich in antioxidant phenolic compounds, can increase the serum antioxidant capacity in humans. J. Nutr. 2383-2390, 1998

Postprandial plasma carotenoid responses following consumption of strawberries, red wine, vitamin C or spinach by elderly women

This study investigated the postprandial plasma responses of carotenoids for 24 h after feeding five specific breakfast beverages; four of which had low or no carotenoid content. In seven fasting healthy elderly female subjects a blood sample (baseline) was obtained, after which they were given a breakfast beverage, containing one of the following: 1) strawberries (240 g); 2) ascorbic acid (1250 mg); 3) spinach (294 g); 4) red wine (300 mL); and 5) control (breakfast beverage only). Blood samples were collected at 0.5, 1, 4, 7, 11, 15 and 24 h. Plasma carotenoids were measured using HPLC. No significant differences were found in the levels of the plasma carotenoids measured among the various treatments at baseline. In the spinach treatment, plasma lutein, zeaxanthin and beta-carotene levels at 7, 11, 15 and 24 h were significantly higher than those at baseline, as expected. All of the carotenoids measured in the control and vitamin C treatments, at subsequent sampling times were not significantly different from those at baseline. However, for most carotenoids, strawberry and red wine feeding resulted in significantly lower carotenoids values from baseline at 11 and 15 h. Subjects who received a diet with low levels of carotenoids, but whose postprandial plasma levels of carotenoids remain steady, might be explained by a mechanism that promotes secretion of carotenoids into the circulation. Assuming that plasma carotenoids are being used over time, we hypothesize that strawberries and red wine contain some substances that interfere with the secretion of carotenoids into the circulation.

Effects of vegetables-fruit extracts and indole-3-carbinol on stearic acid-modulated intercellular communication and cytochrome P450-IA activity

Modulatory effects were investigated of extracts of a vegetables-fruit mixture and indole-3-carbinol (I3C) on stearic acid-modulated gap junctional intercellular communication (GJIC) and cytochrome P450-IA activity (EROD). In V79 cells, pure water and hexane extracts of a vegetables-fruit mixture and 25 μg/ml I3C significantly protected against decreased GJIC caused by 10 μM stearic acid. Furthermore, pure, 10× and 100× diluted vegetables-fruit extracts significantly maintained their capacity to induce EROD activity in Caco-2 cells, but only when these extracts were added to the cells in media already containing 500 μM stearic acid for 48 h. Stearic acid itself did not induce EROD activity. I3C (10, 25, and 50 μg/ml) clearly induced EROD activity in Caco-2 cells, irrespective of the order at which I3C and stearic acid were added to the cells. In conclusion, the present in vitro study showed that vegetables-fruit extracts and I3C modulate effects of stearic acid on intercellular communication and cytochrome P450-IA activity.

Nutritional factors in cancer prevention

Current epidemiologic and laboratory evidence suggests that nutritional factors may play an important role in chemoprevention, although the relative importance of that role for the various micronutrients and dietary constituents is still unclear. The complexity of this area of investigation and practice clearly requires knowledge of the relevant measurement tools, chemistry, biology, and food science, and also the limitations that must be considered in the interpretation of nutritional data. Despite the challenges encountered in translation to clinical research and practice, nutrition remains a promising area of chemoprevention, likely to yield important information and strategies with a large public health impact.

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.

Characterization of beta-carotene 15,15'-dioxygenase activity in TC7 clone of human intestinal cell line Caco-2

The purpose of this study was to identify mammalian cell line(s) which possess intrinsic enzymatic activity of beta-carotene 15, 15'-dioxygenase. This enzyme (EC1.13.11.21) converts beta-carotene to retinal (precursor of retinol and retinoic acid). To assess activity, cellular enzyme preparations were incubated with beta-carotene for 60 min; retinal formed was quantified by HPLC. Activity was not detected in IPEC-1, HepG2, HL60, Wurzburg, or parent Caco-2 cell lines. However, two subclones of Caco-2, PF11 and TC7, possessed activity (2.5 and 14.7 pmol/h.mg, respectively). Using the enzyme preparation of TC7 cells, retinal formation was linear with incubation time and protein concentration; Km and Vm values were 1.6 microM and 23.8 pmol/h.mg, respectively. In addition, when TC7 cells were maintained in serum-free medium, activity was increased 8.2-fold after 19 days of postconfluency. Finally, 48 h incubation with beta-carotene (delivered to TC7 cells in Tween 40) resulted in a 1.7-fold increase of dioxygenase activity and the appearance of vitamin A (9.3 pmol/mg protein). However, retinoic acid was not detected under our experimental conditions. In sum, the TC7 subclone of the Caco-2 cell line possesses beta-carotene 15, 15'-dioxygenase activity and thus can be useful in future investigations of human carotenoid metabolism.

Procyanidins extracted from pine bark protect alpha-tocopherol in ECV 304 endothelial cells challenged by activated RAW 264.7 macrophages: role of nitric oxide and peroxynitrite

A co-culture system was used to study the effect of reactive nitrogen species (RNS) generated by RAW 264.7 macrophages grown on filters and activated by lipopolysaccharide and interferon-gamma, on the alpha-tocopherol levels in ECV 302 endothelial cells. The results indicate that: RNS generated by activated macrophages or by direct administration of peroxynitrite lead to a significant loss of alpha-tocopherol in endothelial cells; pre-incubation with procyanidin extracted from pine bark (Pycnogenol) protects alpha-tocopherol of endothelial cells and enhances by about 15% basal endogenous levels of alpha-tocopherol. These results demonstrate flavonoids participate in the cellular antioxidant network and suggest that Pycnogenol may play an important role in the protection of endothelium from oxidative stress induced by reactive nitrogen species.

Spousal similarities in fruit and vegetable consumption

PURPOSE

To explore similar patterns of fruit and vegetable consumption between health center employees and their spouses.

DESIGN

Cross-sectional mailed survey assessing frequency of fruit and vegetable consumption, as well as demographics and knowledge, attitudes, access, and social support related to fruit and vegetable consumption.

SETTING

Six Massachusetts health centers.

SUBJECTS

Two hundred eleven health center employee/spouse pairs (422 individuals).

MEASURES

The kappa statistic measured agreement in fruit and vegetable consumption between employees and spouses. The Spearman rho coefficient measured correlations for individual responses. Multiple Linear Regression Models examined variables that explained fruit and vegetable consumption level differences.

RESULTS

Response rate was 59%. Mean fruit and vegetable daily intake was 4.68 and 4.30 servings for employees and spouses, respectively. Over 75% of employee and spouse estimates measuring fruit and vegetable consumption-related information, on average, were within one survey response category of each other. Knowledge, attitudes, and access indices were significantly correlated with fruit and vegetable consumption for both employees and spouses. The social support index was significantly correlated with fruit and vegetable consumption only for the spouses. Differences in knowledge, attitudes, and access indices between employees and spouses helped to explain different fruit and vegetable consumption levels. Nonresponse, selection, recall, and seasonal reporting biases may limit the findings' generalizability.

CONCLUSIONS

The effectiveness of worksite nutrition interventions may be improved by involving family/household members.

Measuring stage of change for fruit and vegetable consumption in 9- to 12-year-old girls

This paper presents results of the pilot-testing of a stage of change measure for eating fruit and vegetables (F & V) in 9- to 12-year-old girls. During troop meetings, 259 girls from 22 troops completed a 1-day food recognition form, a brief stage of change algorithm for fruit and for vegetables, and a questionnaire measuring psychosocial variables associated with F & V consumption. Stages for F & V consumption were different and MANOVAs revealed overall significant differences across stages for each variable. F & V intake increased with higher stages, as did preferences, self-efficacy for selecting, preparing, and eating F & V, subjective norms, and F & V preparation skills; reported barriers decreased. Stepwise discriminant analyses between Precontemplation and Contemplation stages identified fruit preferences and barriers differentiating the two stages for fruit consumption and subjective norms and self-efficacy differentiating the two stages for vegetable consumption. Barriers and F & V preparation responsibilities/skills were significant between the Contemplation and the Action stages for both fruit and vegetable consumption, with the additional variable of subjective norms for fruit stage and vegetable preferences for vegetable stage. Findings support the use of this measure to identify stage for children's adoption of F & V consumption behavior and as a guide for intervention development.

The prevention of cancer

1. The major causes of cancer are as follows: (a) Smoking: about a third of U.S. cancer (90% of lung cancer). (b) Dietary imbalances, e.g., lack of dietary fruits and vegetables: The quarter of the population eating the least fruits and vegetables has double the cancer rate for most types of cancer compared to the quarter eating the most; micronutrients may account for much of the protective effect of fruits and vegetables. Excess calories may also contribute to cancer. (c) Chronic infections: mostly in developing countries. (d) Hormonal factors influenced by life-style. 2. There is no epidemic of cancer, except for lung cancer due to smoking. Cancer mortality rates have declined 16% since 1950 (excluding lung cancer and adjusted for the increased life span of the population). 3. Regulatory policy that is focused on traces of synthetic chemicals is based on misconceptions about animal cancer tests. Recent research contradicts these ideas: (a) Rodent carcinogens are not rare. Half of all chemicals tested in standard high-dose animal cancer tests, whether occurring naturally or produced synthetically, are "carcinogens." (b) There are high-dose effects in these rodent cancer tests that are not relevant to low-dose human exposures and which can explain the high proportion of carcinogens. (c) Though 99.9% of the chemicals humans ingest are natural, the focus of regulatory policy is on synthetic chemicals. Over 1000 chemicals have been described in coffee: 27 have been tested and 19 are rodent carcinogens. Plants that we eat contain thousands of natural pesticides which protect plants from insects and other predators: 64 have been tested and 35 are rodent carcinogens. 4. There is no convincing evidence that synthetic chemical pollutants are important for human cancer. Regulations that try to eliminate minuscule levels of synthetic chemicals are enormously expensive: EPA estimates that total expenditures on environmental regulations cost $140 billion/year. It has been estimated by others that the United States spends 100 times more to prevent one hypothetical, highly uncertain death from a synthetic chemical than it spends to save a life by medical intervention. Attempting to reduce tiny hypothetical risks also has costs; for example, if reducing synthetic pesticides makes fruits and vegetables more expensive, thereby decreasing consumption, then cancer will be increased. 5. Improved health will come from knowledge due to biomedical research and from life-style changes by individuals. Little money is spent on biomedical research or on educating the public about lifestyle hazards, compared to the cost of regulations.

Dietary fat consumption and health

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

Procyanidins extracted from Pinus maritima (Pycnogenol): scavengers of free radical species and modulators of nitrogen monoxide metabolism in activated murine RAW 264.7 macrophages

Nitrogen monoxide (NO) has diverse physiological roles and also contributes to the immune defense against viruses, bacteria, and other parasites. However, excess production of NO is associated with various diseases such arthritis, diabetes, stroke, septic shock, autoimmune, chronic inflammatory diseases, and atheriosclerosis. Cells respond to activating or depressing stimuli by enhancing or inhibiting the expression of the enzymatic machinery that produce NO. Thus, maintenance of a tight regulation of NO production is important for human health. Phytochemicals have been traditionally utilized in ways to treat a family of pathologies that have in common the disregulation of NO production. Here we report the scavenging activity of Pycnogenol (the polyphenols containing extract of the bark from Pinus maritima) against reactive oxygen and nitrogen species, and its effects on NO metabolism in the murine macrophages cell line RAW 264.7. Macrophages were activated by the bacterial wall components lipopolysaccharide (LPS) and interferon (IFN-gamma), which induces the expression of large amounts of the enzyme nitric oxide synthase (iNOS). Preincubation of cells with physiological concentrations of Pycnogenol significantly decreased NO generation. It was found that this effect was due to the combination of several different biological activities, i.e., its ROS and NO scavenging activity, inhibition of iNOS activity, and inhibition of iNOS-mRNA expression. These data begin to provide the basis for the conceptual understanding of the biological activity of Pycnogenol and possibly other polyphenolic compounds as therapeutic agents in various human disorders.

Drug interactions with grapefruit juice. Extent, probable mechanism and clinical relevance

Concomitant intake with grapefruit juice increases the concentrations of many drugs in humans. The effect seems to be mediated mainly by suppression of the cytochrome P450 enzyme CYP3A4 in the small intestine wall. This results in a diminished first pass metabolism with higher bioavailability and increased maximal plasma concentrations of substrates of this enzyme. The effect was most pronounced in drugs with a high first pass degradation and in many cases has the clear potential to reach clinical relevance, as shown by an occasional change in drug effects or tolerability. For felodipine, nitrendipine, nisoldipine and saquinavir, the interaction was most marked with median increases of area under the curve (AUC) and/or the maximum (peak) plasma drug concentration after single-dose administration (Cmax) values exceeding 70% of respective control periods. Less pronounced, but possibly relevant, concentration increases were found for nifedipine, nimodipine, verapamil, cyclosporin, midazolam, triazolam and terfenadine. This list is not complete because many drugs have not been studied yet. The components of grapefruit juice which are the most probable causes of the interactions are psoralen derivatives, but the flavonoid naringenin may also contribute. Concomitant grapefruit juice intake does not generally decrease the variability of drug pharmacokinetic parameters. Therefore, it is recommended that patients refrain from drinking grapefruit juice when they are taking a drug that is extensively metabolised, unless a lack of interaction has already been demonstrated for the drug. It is also recommended that drugs possibly interacting with grapefruit juice should be appropriately labelled. A place for grapefruit juice as a drug-sparing agent in treatment involving expensive medicine cannot be derived from the information currently available on grapefruit juice interactions.

Broccoli sprouts in cancer prevention

Recent research has aimed to identify specific phytochemicals in Brassica vegetables, such as sulforaphane in broccoli, that may confer protection against cancer. Clinical, dietary, and policy implications are discussed.

Changing fruit and vegetable consumption among children: the 5-a-Day Power Plus program in St. Paul, Minnesota

OBJECTIVES

A randomized school based trial sought to increase fruit and vegetable consumption among children using a multicomponent approach.

METHODS

The intervention, conducted in 20 elementary schools in St. Paul, targeted a multiethnic group of children who were in the fourth grade in spring 1995 and the fifth grade in fall 1995. The intervention consisted of behavioral curricula in classrooms, parental involvement, school food service changes, and industry support and involvement. Lunchroom observations and 24-hour food recalls measured food consumption. Parent telephone surveys and a health behavior questionnaire measured psychosocial factors.

RESULTS

The intervention increased lunchtime fruit consumption and combined fruit and vegetable consumption, lunchtime vegetable consumption among girls, and daily fruit consumption as well as the proportion of total daily calories attributable to fruits and vegetables.

CONCLUSIONS

Multicomponent school-based programs can increase fruit and vegetable consumption among children. Greater involvement of parents and more attention to increasing vegetable consumption, especially among boys, remain challenges in future intervention research.

Case-control assessment of diet and lung cancer risk in African Americans and Mexican Americans

In this case-control study we determined whether dietary differences underlie some of the ethnic and sex differences in US lung cancer rates. We examined the relationship between diet and lung cancer development in 137 lung cancer cases (93 African Americans and 44 Mexican Americans) and 187 controls (78 African Americans and 109 Mexican Americans). Cases reported a higher daily mean total fat intake (p < 0.001), whereas controls had a higher daily mean intake of dietary fiber (p < 0.001) and fruits (p = 0.02). Ethnic differences in diet were also observed: Mexican Americans consumed less total fat (p < 0.02) and more fiber (p < 0.001) and vegetables (p = 0.08) than African Americans. Additionally, men consumed more total fat (p = 0.08) and less fiber (p = 0.001), fruits (p < 0.001), and vegetables (p = 0.002) than women. Multivariable analysis, after adjustment for the effects of pack-years of smoking, age, total energy intake, sex, and ethnicity, demonstrated a positive association between high total fat consumption and lung cancer risk (p < 0.01) and an inverse association between high fruit consumption and lung cancer risk (p = 0.05). In conclusion, our findings support the hypothesis that diet, particularly high fat consumption and low fruit and vegetable consumption, contributes (independent of cigarette smoking) to the excess lung cancer risk in African-American men, who have the highest lung cancer rates in the United States.

Stages of change and psychosocial correlates of fruit and vegetable consumption among rural African-American church members

PURPOSE

This study examined the relationship between stages of change, other psychosocial factors, and fruit and vegetable (F&V) consumption among rural African-Americans participating in a 5 a Day study.

DESIGN

The cross-sectional design assessed associations between F&V intake, stage of change, self-efficacy, beliefs, barriers, and social support.

SETTING

Participants were surveyed by telephone.

SUBJECTS

Subjects were 3557 adult church members (response rate, 79.1%), aged 18 and over from 10 North Carolina counties.

MEASURES

A seven-item food frequency measured F&V intake. Stage of change was measured using four items; other psychosocial variables were measured using Likert scales. Chi-square tests and analysis of variance were used in statistical analyses.

RESULTS

The majority of participants (65%) were in the preparation stage of change. Individuals in action/maintenance consumed an average of 6.5 daily F&V servings compared to 3.3 to 3.5 servings for those in precontemplation, contemplation, and preparation. Self-efficacy, social support, and belief about how many daily F&V servings are needed, were positively associated with stage. Barriers were most prevalent among precontemplators.

CONCLUSIONS

The findings support the applicability of the stages-of-change model to dietary change among rural African-Americans. The relationship between stage, self-efficacy, social support, and barriers supports using a multicomponent intervention strategy.

Chemoprevention by lycopene of mouse lung neoplasia after combined initiation treatment with DEN, MNU and DMH

An investigation was conducted to assess the chemopreventive potential of lycopene (LP), a naturally occurring hydrocarbon carotenoid found in tomatoes and their products, administered during the post-initiation stage in a multiorgan carcinogenesis model. One hundred eighteen B6C3F1 mice of both sexes were subjected to combined treatment with diethylnitrosamine (DEN), N-methyl-N-nitrosourea (MNU) and 1,2-dimethylhydrazine (DMH) from day 11 after birth to week 9 (DMD treatment) (groups 1 and 2) or their vehicles (group 3). Then group 1 received LP (25 or 50 ppm in drinking water) for 21 weeks from weeks 11 to 32. Group 2 served as a carcinogen alone control and group 3 was given only LP (25 or 50 ppm). All surviving animals were sacrificed at week 32 and the major organs, including the liver, lung, kidney and colon, were histologically examined. The incidences and multiplicities of lung adenomas plus carcinomas combined in male mice in group 1 receiving 50 ppm LP were significantly decreased as compared to the DMD alone or DMD and 25 ppm LP groups (75.0 versus 18.8%, P < 0.02; 0.94 +/- 0.17 versus 0.25 +/- 0.14, P < 0.001). No such effect was observed for females. Although hepatocellular carcinomas were lacking in the DMD and LP groups while two cases were found in the DMD alone group, this difference was not statistically significant. The values for aberrant crypt foci (ACF) and tumors in the colon and kidney did not show any significant variation among the carcinogen-treated subgroups. The results suggest that LP exerts a chemopreventive effect limited to male lung carcinogenesis when given in the post-initiation stage to B6C3F1 mice.

Feasibility of a randomized trial of a high-vegetable diet to prevent breast cancer recurrence

Epidemiologic evidence supports the concept that diet influences risk for breast cancer and suggests that prognosis after the diagnosis of breast cancer may also be related to modifiable nutritional factors. The purpose of this study was to investigate the feasibility of a randomized trial of a high-vegetable, reduced-fat, and increased-fiber diet intervention to reduce risk for recurrence among breast cancer survivors. This major change in dietary pattern was promoted through intensive telephone counseling. Participants were 93 women who had been diagnosed with breast cancer (stages I, II, and IIIA) within the previous four years and who had completed their initial treatment. We assessed adherence to the study diet using repeated 24-hour dietary recalls at 6 and 12 months and measurement of circulating carotenoid concentrations. Six months after randomization, the intervention group had significantly increased their mean intake of vegetables (+4.6 servings/day), fruit (+0.7 servings/day), and fiber (+6.4 g/1,000 kcal) and significantly reduced their intake of dietary fat (-9.9% of energy) compared with the control group. Circulating concentrations of carotenoids also increased in the intervention group. These changes persisted at the 12-month visit. Results of this study demonstrate that telephone counseling can be a useful approach in diet intervention and that breast cancer survivors can adopt and maintain a high-vegetable, reduced-fat dietary pattern.

Broccoli sprouts: an exceptionally rich source of inducers of enzymes that protect against chemical carcinogens

Induction of phase 2 detoxication enzymes [e.g., glutathione transferases, epoxide hydrolase, NAD(P)H: quinone reductase, and glucuronosyltransferases] is a powerful strategy for achieving protection against carcinogenesis, mutagenesis, and other forms of toxicity of electrophiles and reactive forms of oxygen. Since consumption of large quantities of fruit and vegetables is associated with a striking reduction in the risk of developing a variety of malignancies, it is of interest that a number of edible plants contain substantial quantities of compounds that regulate mammalian enzymes of xenobiotic metabolism. Thus, edible plants belonging to the family Cruciferae and genus Brassica (e.g., broccoli and cauliflower) contain substantial quantities of isothiocyanates (mostly in the form of their glucosinolate precursors) some of which (e.g., sulforaphane or 4-methylsulfinylbutyl isothiocyanate) are very potent inducers of phase 2 enzymes. Unexpectedly, 3-day-old sprouts of cultivars of certain crucifers including broccoli and cauliflower contain 10-100 times higher levels of glucoraphanin (the glucosinolate of sulforaphane) than do the corresponding mature plants. Glucosinolates and isothiocyanates can be efficiently extracted from plants, without hydrolysis of glucosinolates by myrosinase, by homogenization in a mixture of equal volumes of dimethyl sulfoxide, dimethylformamide, and acetonitrile at -50 degrees C. Extracts of 3-day-old broccoli sprouts (containing either glucoraphanin or sulforaphane as the principal enzyme inducer) were highly effective in reducing the incidence, multiplicity, and rate of development of mammary tumors in dimethylbenz(a)anthracene-treated rats. Notably, sprouts of many broccoli cultivars contain negligible quantities of indole glucosinolates, which predominate in the mature vegetable and may give rise to degradation products (e.g., indole-3-carbinol) that can enhance tumorigenesis. Hence, small quantities of crucifer sprouts may protect against the risk of cancer as effectively as much larger quantities of mature vegetables of the same variety.

Carotenoids and retinoids: a review of research, clinical, and public health applications

Traditionally, the carotenoids and retinoids have been regarded as dietary sources of vitamin A and have been evaluated regarding their respective physiologic roles in vision, growth, immune system integrity, and prevention of vitamin A deficiency. In the 1990s, however, vitamin A deficiency is no longer widespread in Western countries. Therefore, the role of carotenoids and retinoids is evolving to encompass treatment and prevention of conditions such as cancer and cardiovascular disease, which are prevalent in Western societies. This review summarizes current research concerning the therapeutic utility of vitamin A and its analogues and their roles in the prevention of cancer and cardiovascular disease.

Cancer prevention: epidemiology and experiment

Perhaps the most promising lead to the prevention of cancer is derived from the epidemiologic observations that vegetables and fruit are consistently associated with lower risk of cancers of most epithelia. Over 200 studies have been undertaken, and a high proportion of them show lower risk with greater consumption. There are many plausible pathways to explain this risk reduction. The initial human experiments with specific single agents have proved to be disappointing. Single agents are not an advocated approach to chemotherapy, and may be inappropriate for chemoprevention. Foods may provide the optimal mix of phytochemicals and the best polypharmacy against the emergence of malignant clones.