Diet and cancer prevention

Diet and oral, pharyngeal, and esophageal cancer

Cancers of the upper digestive tract, including those arising in the oral cavity, pharynx, and esophagus, present a significant public health problem worldwide. These cancers are associated with high morbidity and mortality, and identification of protective factors is very important. A number of epidemiological studies have examined the association between vegetables, fruits, carotene, vitamin A, vitamin C, and vitamin E and oral, pharyngeal, and esophageal cancers. The results of 35 epidemiological studies, including one prospective cohort study, one nested case-control study, two randomized controlled trials, nine population-based case-control studies, and 22 hospital-based case-control studies, in addition to in vitro and animal studies, were examined to determine whether the criteria for causal assumption were satisfied for a protective role of these dietary components against development of oral, pharyngeal, and esophageal cancers. There is enough evidence to point to a preventive role of vegetable intake, including green vegetables, cruciferous vegetables, and yellow vegetables, total fruit intake, and citrus fruit intake. Yellow fruits are likely to be protective. Carotene, vitamin C, and vitamin E are protective, most likely in combination with each other and other micronutrients. The role of vitamin A is not clear because of conflicting findings in the studies reviewed.

Diet, Nutrition, and Cancer Prevention: The Postgenomic Era

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

Characterization of nonstarch polysaccharides content from different edible organs of some vegetables, determined by GC and HPLC: comparative study

Content and composition of dietary fiber as nonstarch polysaccharides (NSP) was determined in vegetables belonging to different types of edible organs, using GC and HPLC. Samples analyzed were subterranean organs (radish and leek), leaves (celery, swiss chard, and lettuce), stalks (celery, swiss chard, and asparagus), inflorescence (broccoli), and fruits (tomato, green pepper, and marrow). The results indicate that though the monomeric profile is similar in all these samples quantitative differences were found for neutral sugars and uronic acids among samples of the same type of vegetal organ. The NSP values determined using CG method were in good agreement with HPLC method (R(2) = 0.9005). However, arabinose, mannose, and galactose plus rhamnose are more influenced by the analytical method used than the rest of the monomers in nearly all the samples analyzed. Final values of NSP depend on the method used in celery stalks, broccoli, and green pepper.

Ethnic differences in the nutrient intake adequacy of premenopausal US women: results from the Third National Health Examination Survey

OBJECTIVE

To examine the adequacy of dietary intake of calcium; folate; and vitamins C, D, E, B-6, and B-12 in premenopausal US women of differing ethnicity.

DESIGN

Analyses of single and duplicate 24-hour recalls were conducted to determine dietary intake during the Third National Health and Nutrition Examination Survey.

SUBJECTS

Three thousand five hundred eighty-five randomly selected women aged 20 to 50 years from across the United States who were not pregnant or lactating were examined between 1988 and 1994.

STATISTICAL ANALYSES

Usual nutrient intake distributions were estimated using the Iowa State University method for adjustment of the distribution. The Estimated Average Requirement cut-point method was used to determine the proportion of women with inadequate intake for each nutrient in each ethnic group.

RESULTS

More than 75% of women irrespective of ethnic group had usual intakes of calcium lower than the new Adequate Intake. More than 90% of the women had inadequate intakes of folate and vitamin E from food sources alone. More than half of smokers had inadequate intakes of vitamin C. Intakes of vitamins B-6 and B-12 were low in less than 10% of these women.

APPLICATIONS/CONCLUSIONS

This article provides evidence that a high proportion of premenopausal US women are underconsuming a variety of nutrients. Dietary intakes alone are not currently adequate to meet the new recommended intakes. Nutritional supplement use is widespread and effective, but does not eliminate the concerns for at-risk populations. Awareness of the general inadequacies in intakes of vitamin E and folic acid at large, and in many women vitamin C as well, can help direct individual dietary recommendations and place the emphasis in group counseling on nutrients that are of widespread concern. In addition, foods rich in vitamins B-6 and of general nutritional benefit should be emphasized among African American women in the United States as a substantial proportion of this group is still showing inadequate intakes from foods.

Diet, individual responsiveness and cancer prevention

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

Effect of caloric restriction on Hprt lymphocyte mutation in aging rats

Caloric restriction (CR) reduces tumor incidence and retards aging in laboratory animals, including non-human primates. Because of the relationships among mutation, disease susceptibility, and aging, we investigated whether or not CR affects the accumulation of somatic cell mutations in aging animals. Starting at approximately 2 months of age, male CD rats (Harlan Sprague-Dawley-derived) were placed on different levels of dietary intake: ad libitum (AL) feeding, and 90% (10% CR), 75% (25% CR) and 60% (40% CR) of the total calories consumed by AL animals. At 3, 6, 12, and 24 months after the beginning of CR, Hprt mutant frequencies (MFs) were determined. The MFs measured in spleen lymphocytes from AL and CR rats sacrificed at 3 months of dietary restriction were similar for all dietary groups. However, the MFs at 6, 12, and 24 months of CR were significantly higher in AL-fed rats compared with animals on 40% CR: (4.5+/-0.4)x10(-6) versus (3.3+/-0.3)x10(-6) (P=0.032) in 6 months CR rats; (10.3+/-2.3)x10(-6) versus (7.3+/-1.2)x10(-6) in 12 months CR rats (P=0.04), and (18.3+/-3.2)x10(-6) versus (7.8+/-1.0)x10(-6) (P=0.001) in 24 months CR rats. In addition, rats receiving 25% CR for 24 months had a MF, (10.7+/-2.0)x10(-6), between the 40% CR and AL rats. Multiplex PCR of the Hprt gene in mutant clones from 12 and 24 months 40% CR rats and the corresponding AL rats detected deletions in 42% of CR mutants and 19% of AL mutants. Because of the difference in Hprt MF in the two groups, the estimated MF associated with deletions in CR rats was similar to the deletion MF in AL rats. This observation implies that the lower MF in CR rats is due to a reduction in smaller Hprt mutations (i.e. base substitutions and frameshifts). The pattern of smaller Hprt mutations from AL rats suggests that many were produced by reactive oxygen species (ROS). The results indicate that CR reduces the accumulation of spontaneous somatic cell mutation in aging rats, especially those caused by base substitutions and frameshifts.

Antimutagenicity of supercritical CO2 extracts of Terminalia catappa leaves and cytotoxicity of the extracts to human hepatoma cells

Natural antimutagens may prevent cancer and are therefore of great interest to oncologists and the public at large. Phytochemicals are potent antimutagen candidates. When the Ames test was applied to examine the antimutagenic potency of supercritical carbon dioxide (SC-CO(2)) extracts of Terminalia catappa leaves at a dose of 0.5 mg/plate, toxicity and mutagenicity were not detected. The antimutagenic activity of SC-CO(2) extracts increased with decreases of temperature (60, 50, and 40 degrees C) and pressure (4000, 3000, and 2000 psi) used for extraction. The most potent antimutagenicity was observed in extracts obtained at 40 degrees C and 2000 psi. At a dose of 0.5 mg of extract/plate, approximately 80% of the mutagenicity of benzo[a]pyrene (B[a]P, with S-9) and 46% of the mutagenicity of N-methyl-N '-nitroguanidine (MNNG, without S-9) were inhibited. Media supplemented with SC-CO(2) extracts at a range of 0-500 microg/mL were used to cultivate human hepatoma (Huh 7) and normal liver (Chang liver) cells. The viability of the cells was assayed by measuring cellular acid phosphatase activity. A dose-dependent growth inhibition of both types of cells was observed. The SC-CO(2) extracts were more cytotoxic to Huh 7 cells than to Chang liver cells. The observation that SC-CO(2) extracts of T. catappa leaves did not induce mutagenicity at the doses tested while exhibiting potent antimutagenicity and were more cytotoxic to human hepatoma cells than to normal liver cells is of merit and warrants further investigation.

Diet quality and cancer incidence in Nova Scotia, Canada

Cancer rates in the province of Nova Scotia, Canada, are among the highest in the country and coincide with elevated rates of risk factors such as smoking, poor diet, and obesity. To investigate the importance of diet on cancer, using data from the 1990 Nova Scotia Nutrition Survey, we developed a diet quality score reflecting compliance with 17 nutrient recommendations. The survey data were subsequently linked with the provincial cancer registry, and the relationship between diet quality and cancer was quantified using logistic regression. Our results support an inverse relationship between diet quality and cancer, although limited statistical power resulting from our small study sample did not reveal any statistically significant relationships. We estimated that cancer incidence could potentially be reduced by approximately 35% through improved diet quality. On the basis of poor diet, nutrition-related factors (high body mass index), our estimates of the preventable fraction of cancer, and the high provincial cancer rates, we recommend health promotion strategies aimed at improving diet quality in Nova Scotia.

The role of carotenoids on the risk of lung cancer

Smoking prevention and cessation remain the primary methods of reducing the incidence of lung cancer. The limited success of efforts towards smoking cessation have led to increasing interest in the role of nutrition in lung cancer prevention. One class of nutrients that has attracted attention as potential chemopreventive agents is the carotenoids, especially beta-carotene, due to their antioxidant properties. In vitro, carotenoids exert antioxidant functions and inhibit carcinogen-induced neoplastic transformation, inhibit plasma membrane lipid oxidation, and cause upregulated expression of connexin 43. These in vitro results suggest that carotenoids have intrinsic cancer chemopreventive action in humans. Many cohort and case-control study data have shown an inverse relationship between fruit and vegetable consumption and lung cancer, although several more recent studies have cast doubt on these findings. Different effects of various dietary nutrients on lung cancer risk have been observed. Several prospective intervention trials were undertaken to examine the effect of supplementation on the risk of lung cancer. Some of these studies demonstrated an increased incidence and mortality from lung cancer in those receiving supplementation. Many hypotheses have emerged as to the reasons for these findings.

Food sources of carbohydrates in a European cohort of adults

OBJECTIVE

To describe the average consumption of carbohydrate-providing food groups among study centres of the European Prospective Investigation into Cancer and Nutrition (EPIC).

METHODS

Of the 27 redefined EPIC study centres, 19 contributed subjects of both genders and eight centres female participants only (men, women, after exclusion of subjects under 35 and over 74 years of age from the original 36 900 total). Dietary data were obtained using the 24-hour recall methodology using the EPIC-SOFT software. The major sources of dietary carbohydrate were identified, and 16 food groups were examined.

RESULTS

The 10 food groups contributing most carbohydrate were bread; fruit; milk and milk products; sweet buns, cakes and pies; potato; sugar and jam; pasta and rice; vegetables and legumes; crispbread; and fruit and vegetable juices. Consumption of fruits as well as vegetables and legumes was higher in southern compared with northern centres, while soft drinks consumption was higher in the north. Italian centres had high pasta and rice consumption, but breakfast cereal, potato, and sweet buns, cakes and pies were higher in northern centres. In Sweden, lower bread consumption was balanced with a higher consumption of crispbread, and with sweet buns, cakes and pies. Overall, men consumed higher amounts of vegetables and legumes, bread, soft drinks, potatoes, pasta and rice, breakfast cereal and sugar and jam than women, but fruit consumption appeared more frequent in women.

CONCLUSION

The study supports the established idea that carbohydrate-rich foods chosen in northern Europe are different from those in the Mediterranean region. When comparing and interpreting diet-disease relationships across populations, researchers need to consider all types of foods.

Consumption of vegetables, fruit and other plant foods in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts from 10 European countries

OBJECTIVE

To describe and compare the consumption of the main groups and sub-groups of vegetables and fruits (V&F) in men and women from the centres participating in the European Prospective Investigation into Cancer and Nutrition (EPIC).

DESIGN

Cross-sectional analysis. Dietary intake was assessed by means of a 24-hour dietary recall using computerised interview software and standardised procedures. Crude and adjusted means were computed for the main groups and sub-groups of V&F by centre, separately for men and women. Adjusted means by season, day of the week and age were estimated using weights and covariance analysis.

SETTING

Twenty-seven centres in 10 European countries participating in the EPIC project.

SUBJECTS

In total, 35 955 subjects (13 031 men and 22 924 women), aged 35-74 years, randomly selected from each EPIC cohort.

RESULTS

The centres from southern countries had the highest consumption of V&F, while the lowest intake was seen in The Netherlands and Scandinavia for both genders. These differences were more evident for fruits, particularly citrus. However, slightly different patterns arose for some sub-groups of vegetables, such as root vegetables and cabbage. Adjustment for body mass index, physical activity, smoking habits and education did not substantially modify the mean intakes of vegetables and fruits.

CONCLUSIONS

Total vegetable and fruit intake follows a south-north gradient in both genders, whereas for several sub-groups of vegetables a different geographic distribution exists. Differences in mean intake of V&F by centre were not explained by lifestyle factors associated with V&F intake.

Barley lunasin suppresses ras-induced colony formation and inhibits core histone acetylation in mammalian cells

Lunasin is a novel peptide originally identified in soybean that suppresses chemical carcinogen-induced transformation in mammalian cells and skin carcinogenesis in mice. Since the lunasin gene was cloned from soybean and the chemically synthesized form of the lunasin peptide has been used in experiments conducted so far, the isolation of lunasin from other natural sources and testing of its biological properties have not been carried out. We report here the isolation, purification, and biological assay of lunasin from barley, a newly found rich source of the peptide. The identity of lunasin was established by Western blot analysis and mass spectrometric peptide mapping of the in-gel tryptic digest of the putative protein band. Lunasin was partially purified with anion exchange and immunoaffinity chromatography. The crude and partially purified lunasin from barley suppressed colony formation in stably ras-transfected mouse fibroblast cells induced with IPTG. These fractions also inhibited histone acetylation in mouse fibroblast NIH 3T3 and human breast MCF-7 cells in the presence of the histone deacetylase inhibitor sodium butyrate.

Higher radical scavenging activities of polyphenolic antioxidants can be ascribed to chemical reactions following their oxidation

Radical scavenging activities of 34 natural antioxidants were investigated from an electrochemical viewpoint. While the correlation of the oxidation potentials with their DPPH radical scavenging activities (represented by EC(50)) was not high (the correlation coefficient, r=0.73), the number of electrons n required for oxidation of an antioxidant, being obtained by continuous flow-column electrolysis with a slower flow rate (0.05 ml min(-1)), did show a good correlation with EC(50) (1/EC(50)=1.67n+0.50 with r=0.94). The n values of most polyphenols were increased with a decrease in the flow rate, while those of nonpolyphenols were invariant. This suggests that a slower subsequent chemical reaction(s) should be involved in the oxidation of polyphenols, whose higher radical scavenging activities seem to be ascribed to the chemical reactions. In this study, we have proposed a possible mechanism for the oxidation of polyphenols, in which the oxidizable -OH moieties are reproduced through an oxidative dimerization (or more highly polymerization).

Identification of Molecular Targets and Biomarkers for Disease Resistance

Discoveries about molecular targets for nutrients will unquestionably provide important clues into how best to optimize nutrition for an individual. The "Credentialing" of nutrients in terms of their influence on genetic and epigenetic events that bring about a desired phenotypic change is surely within the future of nutrition science.

Calorific restriction: can we extrapolate from animals to humans?

Dietary restriction in animals results in a dramatic reduction of cancer incidence. Several attempts have been made to extrapolate this observation to the human situation. Recent developments in our knowledge of gene-dietary interactions, particularly in relation to vitamins, have been taken into account in a new examination of the likely effects of dietary restriction in humans, but this is a relatively new area of research. Epidemiological studies in relation to diet have also been considered, but probably need to be refined further because of the subtle effects of dietary interactions. Until more detailed information is available the extrapolation can still only be made with the utmost caution.

Diet and environmental carcinogenesis in breast/gynaecological cancers

This paper reports on recent advances on the relation between diet, other environmental factors and breast and gynaecological cancers. Despite considerable research the issue remains still unsettled. The protective effect of a diet rich in vegetables and fruit, and thus selected (antioxidant) micronutrients, is not consistently reported in various studies. The possible relationship between fats and breast and female genital tract neoplasms also remains unconfirmed, while the potential benefits of physical activity remains unquantified. Alcohol appears to be related to the risk of breast cancer and overweight is associated with post-menopausal breast cancer and is strongly related to the risk of endometrial cancer.

From carcinogenesis to clinical interventions for cancer prevention

During the last three decades, the scientific community has made immense progress in acquiring the knowledge needed to prevent cancer. Pioneering research helped to identify potential causes of cancer, particularly environmental factors such as diet, and provided insight regarding their mechanisms-of-action. Concurrently, promising inhibitors of cancer that appeared able to either arrest or reverse cancer development by interfering with one or more steps in the process of carcinogenesis were identified and systematically evaluated for their potential as chemopreventive agents. Numerous agents determined to be safe and effective in preclinical trials have been and continue to be tested in Phase I,II, and III clinical interventions for cancers at various sites, including breast, colon, prostate, esophagus, mouth, lung, cervix, endometrium, ovary, liver, bladder, and skin. The development of valid intermediate biomarkers that can serve as surrogate endpoints for clinical disease is urgently needed to accelerate advances in clinical trials for cancer prevention.