Vitamin A and lung cancer

Biochemical Evaluation of Some Fruit Characteristics of Blueberry Progenies Obtained from 'Simultan × Duke'

The popularity of Vaccinium corymbosum blueberry cv. has increased over time because its fruits are highly valued for their taste, aroma, and multiple ways of use. A field trial with two genotypes and their hybrids was organized during 2021-2022 at the Research Institute for Fruit Growing Pitesti-Maracineni, Romania. This paper proposes a comparative analysis of the quality of berries in 17 hybrids of the 'Simultan' and 'Duke' cultivars, selected by the size and the soluble solid content, in agreement with the objectives of the blueberry breeding program. The genotype influence on berry weight, total soluble solids, pH, vitamin C, total polyphenols, total flavonoids, total anthocyanins, lycopene, β-carotene, and antioxidant activity was determined considering the climatic factors. The results showed that fruit weight varied between 1.22 and 2.47 g, total soluble solids reached a maximum of 19.22 °Brix, and the pH oscillated between 3.14 and 3.89. Vitamin C content varied from 9.52 to 18.69 mg in 100 g fresh weight, with an average of 14.35 mg/100 g. Total polyphenol, flavonoid, and anthocyanin contents averaged 709.92 mg gallic acid equivalent in 100 g fresh weight, 165.48 mg catechin equivalent in 100 g fresh weight, and 81.88 mg cyanidin-3-O-glucoside equivalent in 100 g fresh weight, respectively. Results show that the strategy of growers to produce blueberries with a large diameter, visually attractive for traders and consumers, is not sufficient for repeat sales. Our study proves that large fruits do not have the highest content of bioactive compounds. Smaller berries had higher polyphenol, lycopene, and β-carotene contents. It is recommended that the selection of the hybrid in the breeding program also takes into account the content of bioactive compounds.

Consequences of Vitamin A Deficiency: Immunoglobulin Dysregulation, Squamous Cell Metaplasia, Infectious Disease, and Death

Vitamin A is an important regulator of immune protection, but it is often overlooked in studies of infectious disease. Vitamin A binds an array of nuclear receptors (e.g., retinoic acid receptor, peroxisome proliferator-activated receptor, retinoid X receptor) and influences the barrier and immune cells responsible for pathogen control. Children and adults in developed and developing countries are often vitamin A-deficient or insufficient, characteristics associated with poor health outcomes. To gain a better understanding of the protective mechanisms influenced by vitamin A, we examined immune factors and epithelial barriers in vitamin A deficient (VAD) mice, vitamin D deficient (VDD) mice, double deficient (VAD+VDD) mice, and mice on a vitamin-replete diet (controls). Some mice received insults, including intraperitoneal injections with complete and incomplete Freund’s adjuvant (emulsified with PBS alone or with DNA + Fus-1 peptide) or intranasal inoculations with Sendai virus (SeV). Both before and after insults, the VAD and VAD+VDD mice exhibited abnormal serum immunoglobulin isotypes (e.g., elevated IgG2b levels, particularly in males) and cytokine/chemokine patterns (e.g., elevated eotaxin). Even without insult, when the VAD and VAD+VDD mice reached 3–6 months of age, they frequently exhibited opportunistic ascending bacterial urinary tract infections. There were high frequencies of nephropathy (squamous cell hyperplasia of the renal urothelium, renal scarring, and ascending pyelonephritis) and death in the VAD and VAD+VDD mice. When younger VAD mice were infected with SeV, the predominant lesion was squamous cell metaplasia of respiratory epithelium in lungs and bronchioles. Results highlight a critical role for vitamin A in the maintenance of healthy immune responses, epithelial cell integrity, and pathogen control.

The Effects of a Multimedia System in Supermarkets To Alter Shoppers' Food Purchases

A randomized-control test of a multimedia nutrition intervention—the Nutrition for a Lifetime System (NLS©)— utilized supermarket receipts to examine effects of NLS treatment on the daily per person nutritional content of participants' supermarket purchases. In regression analyses controlling for background variables, baseline purchases and trends toward increased purchasing, NLS treatment contributed to lower levels of total fat and to higher levels of total fiber and servings of fruits and vegetables at post-test. Redemption of NLS coupons contributed to greater decreases in fat and increases in servings of fruits and vegetables in users' purchases. Implications for future interventions promoting healthier food choices include tailoring program content and addressing broader lifestyle issues such as caloric intake and expenditure.

Targeting cancer stem-like cells using dietary-derived agents - Where are we now?

Diet has been linked to an overwhelming proportion of cancers. Current chemotherapy and targeted therapies are limited by toxicity and the development of resistance against these treatments results in cancer recurrence or progression. In vitro evidence indicates that a number of dietary-derived agents have activity against a highly tumorigenic, chemoradiotherapy resistant population of cells within a tumour. This population is associated with cancer recurrence and is therefore clinically significant. Targeting this subpopulation, termed cancer stem-like cells with dietary-derived agents provides a potentially low toxicity strategy to enhance current treatment regimens. In addition, dietary-derived compounds also provide a novel approach to cancer prevention strategies. This review focusses on selected diet-derived agents that have been shown to specifically target cancer stem-like cells using in vivo models, or in clinical trials. Furthermore, the potential limitations of these studies are discussed, and areas of research that need to be addressed to allow successful translation of dietary-derived agents to the clinical arena are highlighted.

Approaches for the identification of genetic modifiers of nutrient dependent phenotypes: examples from folate

By combining the sciences of nutrition, bioinformatics, genomics, population genetics, and epidemiology, nutrigenomics is improving our understanding of how diet and nutrient intake can interact with or modify gene expression and disease risk. In this review, we explore various approaches to examine gene–nutrient interactions and the modifying role of nutrient consumption, as they relate to nutrient status and disease risk in human populations. Two common approaches include the use of SNPs in candidate genes to identify their association with nutritional status or disease outcomes, or genome-wide association studies to identify genetic polymorphisms associated with a given phenotype. Here, we examine the results of various gene–nutrient interaction studies, the association of genetic polymorphisms with disease expression, and the identification of nutritional factors that modify gene-dependent disease phenotypes. We have focused on specific examples from investigations of the interactions of folate, B-vitamin consumption, and polymorphisms in the genes of B-vitamin dependent enzymes and their association with disease risk, followed by an examination of the strengths and limitations of the methods employed. We also present suggestions for future studies, including an approach from an on-going large scale study, to examine the interaction of nutrient intake and genotypic variation and their impact on nutritional status.

Mendelian randomisation: a tool for assessing causality in observational epidemiology

Detection and assessment of the effect of a modifiable risk factor on a disease with view to informing public health intervention policies are of fundamental concern in aetiological epidemiology. In order to have solid evidence that such a public health intervention has the desired effect, it is necessary to ascertain that an observed association or correlation between a risk factor and a disease means that the risk factor is causal for the disease. Inferring causality from observational data is difficult, typically due to confounding by social, behavioural, or physiological factors which are difficult to control for and particularly difficult to measure accurately. A possible approach to inferring causality when confounding is believed to be present but unobservable, as it may not even be fully understood, is based on the method of instrumental variables and is known under the name of Mendelian randomisation if the instrument is a genetic variant. While testing for the presence of a causal effect using this method is generally straightforward, point estimates of such an effect are only obtainable under additional parametric assumptions. This chapter introduces the concept and illustrates the method and its assumptions with simple real-life examples. It concludes with a brief discussion on pitfalls and limitations.

Monitoring micronutrients in cigarette smokers

Smoking is associated with oxidative stress and increased risks of many chronic diseases that both shorten life and impair its quality. Low concentrations of several micronutrients, especially the antioxidants vitamin C and beta-carotene, are also associated with smoking, and there has been much interest in determining whether deficiencies in micronutrients are involved etiologically in smoking-related diseases. The objective of this review was to bring together reports on dietary intakes, biochemical indicators of micronutrient status, and results of some intervention studies on micronutrients where authors had compared outcomes in smokers and non-smokers. The micronutrients discussed are vitamins A, E, and C; the carotenoids; some of the B-vitamin group; and the minerals selenium, zinc, copper, and iron. The data were then examined to determine whether effects on the biochemical markers of micronutrient status were due to differences in dietary intakes between smokers and non-smokers or to the consequences of inflammatory changes caused by the oxidative stress of smoking. It was concluded that although smoking is associated with reduced dietary intake of vitamin C and carotenoid-containing foods, inflammatory changes increase turnover of these micronutrients so that blood concentrations are still lower in smokers than non-smokers even when there is control for dietary differences. In the case of vitamin E, there is some evidence for increased turnover of this nutrient in smokers, but this has little to no influence on blood concentrations, and there are no differences in dietary intake of vitamin E between smokers and non-smokers. Serum concentrations of vitamin A, folate, and vitamin B12 and B6 markers do not appear to be influenced by smoking, although there is some influence of dietary intake on concentrations of these nutrients in the body. In the case of the minerals examined, the main effects on biochemical markers of mineral status were attributed to inflammation and were therefore greater in heavy or long-term smokers. Serum concentrations of selenium and erythrocyte GPx activity were lower in smokers. Erythrocyte CuZn-SOD activity and serum ceruloplasmin concentrations were elevated, while serum zinc concentrations were depressed only in heavy smokers. Lastly, smoking appears to affect iron homeostasis mainly by changing hemoglobin concentrations, which were in general increased. Serum iron, TfR, and ferritin were mostly unaffected by smoking, except in pregnancy where there is evidence of increased erythropoiesis causing lower saturation of plasma transferrin and some evidence of lowering of iron stores.

Genetic epidemiology and public health: hope, hype, and future prospects

Genetic epidemiology is a rapidly expanding research field, but the implications of findings from such studies for individual or population health are unclear. The use of molecular genetic screening currently has some legitimacy in certain monogenic conditions, but no established value with respect to common complex diseases. Personalised medical care based on molecular genetic testing is also as yet undeveloped for common diseases. Genetic epidemiology can contribute to establishing the causal nature of environmentally modifiable risk factors, through the application of mendelian randomisation approaches and thus contribute to appropriate preventive strategies. Technological and other advances will allow the potential of genetic epidemiology to be revealed over the next few years, and the establishment of large population-based resources for such studies (biobanks) should contribute to this endeavour.

Proposed criteria for assessing the efficacy of cancer reduction by plant foods enriched in carotenoids, glucosinolates, polyphenols and selenocompounds

BACKGROUND AND AIMS

The cancer-protective properties of vegetable consumption are most likely mediated through 'bioactive compounds' that induce a variety of physiologic functions including acting as direct or indirect antioxidants, regulating enzymes and controlling apoptosis and the cell cycle. The 'functional food' industry has produced and marketed foods enriched with bioactive compounds, but there are no universally accepted criteria for judging efficacy of the compounds or enriched foods.

SCOPE

Carotenoids, glucosinolates, polyphenols and selenocompounds are families of bioactive compounds common to vegetables. Although numerous studies have investigated the agricultural and human health implications of enriching foods with one or more of these compounds, inadequate chemical identification of compounds, lack of relevant endpoints and inconsistencies in mechanistic hypotheses and experimental methodologies leave many critical gaps in our understanding of the benefits of such compounds. This review proposes a decision-making process for determining whether there is reasonable evidence of efficacy for the both the compound and the enriched food. These criteria have been used to judge the evidence of efficacy for cancer prevention by carotenoids, polyphenols, glucosinolates and selenocompounds.

CONCLUSIONS

The evidence of efficacy is weak for carotenoids and polyphenols; the evidence is stronger for glucosinolates and lycopene, but production of enriched foods still is premature. Additionally there is unacceptable variability in the amount and chemical form of these compounds in plants. The evidence of efficacy for selenocompounds is strong, but the clinical study that is potentially the most convincing is still in progress; also the variability in amount and chemical form of Se in plants is a problem. These gaps in understanding bioactive compounds and their health benefits should not serve to reduce research interest but should, instead, encourage plant and nutritional scientists to work together to develop strategies for improvement of health through food.

'Mendelian randomization': can genetic epidemiology contribute to understanding environmental determinants of disease?

Associations between modifiable exposures and disease seen in observational epidemiology are sometimes confounded and thus misleading, despite our best efforts to improve the design and analysis of studies. Mendelian randomization-the random assortment of genes from parents to offspring that occurs during gamete formation and conception-provides one method for assessing the causal nature of some environmental exposures. The association between a disease and a polymorphism that mimics the biological link between a proposed exposure and disease is not generally susceptible to the reverse causation or confounding that may distort interpretations of conventional observational studies. Several examples where the phenotypic effects of polymorphisms are well documented provide encouraging evidence of the explanatory power of Mendelian randomization and are described. The limitations of the approach include confounding by polymorphisms in linkage disequilibrium with the polymorphism under study, that polymorphisms may have several phenotypic effects associated with disease, the lack of suitable polymorphisms for studying modifiable exposures of interest, and canalization-the buffering of the effects of genetic variation during development. Nevertheless, Mendelian randomization provides new opportunities to test causality and demonstrates how investment in the human genome project may contribute to understanding and preventing the adverse effects on human health of modifiable exposures.

Does chronic periodontitis cause coronary heart disease? A review of the literature

BACKGROUND

Chronic periodontitis, or CP, has been associated with coronary heart disease, or CHD. This article reviews the available prospective CP-CHD evidence.

LITERATURE REVIEWED

In nine cohort studies, CP was associated with a 15 percent greater risk of developing CHD. Conclusions from individual studies depended on study characteristics. Summary risk estimates for studies controlling for smoking intensity (five of nine studies) or health awareness (two of nine studies) or studies with more than 600 CHD events (three of nine studies) suggest that CP is either not at all or weakly associated with CHD. Summary risk estimates for the studies that did not control for these factors or that examined an insufficient number of CHD events reported a weak increase in CHD risk associated with CP (20 percent greater). These data suggest that the CP-CHD associations observed in smaller studies are due to insufficient control for lifestyle differences. In addition, one cohort study reported that edentulous people had a CHD risk similar to that of people with CP. Therefore, the plausibility of dental infection elimination affecting CHD risk appears limited.

SUMMARY

Current evidence supporting a causal CP-CHD link is weak. Rigorous methodological and analytical control of lifestyle factors such as smoking will be required to elucidate whether the CP-CHD disease association is either small or nonexistent.

CLINICAL IMPLICATIONS

Cigarette smoking destroys both oral and systemic health. Because of this strong common causal factor, oral and systemic health are linked. Dentistry should continue to play an important role in implementing smoking prevention and cessation programs.

Diet and lung cancer: a new approach

Lung cancer is one of major public health problems facing the world today, owing to the high incidence of the disease and its poor prognosis. Although the principal cause of lung cancer is tobacco use, smokers find it extremely difficult to quit the habit. Hence, there is a need to take action targeted at other risk factors for this disease. One such factor is diet, which is known to be able to raise or lower the risk of lung cancer. This paper seeks to complement other reviews in the field and to shed more light both on the influence that dietary factors may have upon the occurrence of this neoplasm and on the causes of this possible effect.

The effect of the Maryland WIC 5-A-Day promotion program on participants' stages of change for fruit and vegetable consumption

The Maryland Women, Infants and Children (WIC) 5-A-Day Promotion Program examined the effect of a multifaceted nutrition intervention on changing the fruit and vegetable consumption of low-income women in the WIC program in Maryland. The sample consisted of 3,122 participants (1,443 intervention and 1,679 control) with a mean age of 27.2. Fifty-six percent were Black/African American. This article focuses on the effect of the intervention on the stages of change of the participants. Intervention participants showed significantly greater positive movement through the stages than control participants. Stages of change were measured for two specific target behaviors: eating five servings of fruits and vegetables a day and eating more servings of fruit and vegetables a day. Results demonstrated significant differences in the stage status of intervention and control women and in movement through the stages. The effectiveness of the intervention across groups depended on which staging measure was used.

Beta-carotene and lung cancer: a case study

The conflicting evidence of the relation between beta-carotene and lung cancer in humans serves as a poignant case study with respect to what types of evidence are sufficient to support or change a nutrition recommendation. This article is a review of the available evidence of the relation between beta-carotene and lung cancer, including data regarding beta-carotene intake (from diet and supplements), beta-carotene biochemical status, and vegetable and fruit consumption, and a discussion of the role of this evidence in making nutrition recommendations. More than 30 case-control and cohort studies were conducted over many years in various populations and indicated that people who eat more vegetables and fruit, foods rich in carotenoids, and carotenoids (beta-carotene in particular), as well as those with higher blood beta-carotene concentrations, have a lower risk of lung cancer than those who eat fewer such foods or have lower beta-carotene concentrations. In contrast, the intervention results from large, controlled trials of beta-carotene supplementation do not support the observed beneficial associations or a role for supplemental beta-carotene in lung cancer prevention; instead, they provide striking evidence for adverse effects (ie, excess lung cancer incidence and overall mortality) in smokers. The findings require that caution be exercised in recommending supplemental beta-carotene, particularly for smokers, and argue against changing the vegetable-fruit recommendations in the direction of greater nutrient specificity. This case study of beta-carotene and lung cancer stresses the importance of having results from at least one, and preferably more, large, randomized intervention trial before public health recommendations concerning micronutrient supplementation are considered.

Knowledge, attitudes, and practices related to fruit and vegetable consumption of high school students

PURPOSE

To assess the level of nutrition knowledge, attitudes and practices related to fruit and vegetable consumption of high school students attending participating parochial schools in the New Orleans area.

METHODS

The baseline data reported in this study, "Gimme 5: A Fresh Nutrition Concept for Students," represents one of the nine National Cancer Institute-funded projects from the national "5-A-Day for Better Health Program" initiated in 1991. A survey containing 22 nutrition-related items about fruit and vegetables was used to assess knowledge in 2213 students.

RESULTS

On average, adolescents reported 39% correct knowledge scores. A significant ethnic effect (p < .001) was noted, with White adolescents scoring higher than African American adolescents. Significant ethnic differences in the frequency of fruit and vegetable consumption were also observed, with African-American adolescents reporting a lower mean consumption (2.17 servings) than white adolescents (2.69 servings). Consumption by Hispanic youth (2.48 servings) was similar to those in the "other" ethnic category (2.55 servings). Girls reported being more confident in their ability to eat five servings of fruits and vegetables per day than did boys (p < .05).

CONCLUSIONS

Although the knowledge and consumption levels of adolescents with regard to fruits and vegetables were low, their attitudes toward learning about healthier eating practices were favorable.

Increasing fruit and vegetable consumption through worksites and families in the treatwell 5-a-day study

OBJECTIVES

We report on the results of the Treatwell 5-a-Day study, a worksite intervention aimed at increasing consumption of fruits and vegetables.

METHODS

Twenty-two worksites were randomly assigned to 3 groups: (1) a minimal intervention control group, (2) a worksite intervention, and (3) a worksite-plus-family intervention. The interventions used community-organizing strategies and were structured to target multiple levels of influence, following a socioecological model. Data were collected by self-administered employee surveys before and after the intervention; the response rate was 87% (n = 1359) at baseline and 76% (n = 1306) at follow-up. A process tracking system was used to document intervention delivery.

RESULTS

After control for worksite, gender, education, occupation, race/ethnicity, and living situation, total fruit and vegetable intake increased by 19% in the worksite-plus-family group, 7% in the worksite intervention group and 0% in the control group (P = .05). These changes reflect a one half serving increase among workers in the worksite-plus-family group compared with the control group (P = .018).

CONCLUSIONS

The worksite-plus-family intervention was more successful in increasing fruit and vegetable consumption than was the worksite intervention. Worksite interventions involving family members appear to be a promising strategy for influencing workers' dietary habits.

The effects of a health promotion-health protection intervention on behavior change: the WellWorks Study

OBJECTIVES

This study assessed the effects of a 2-year integrated health promotion-health protection work-site intervention on changes in dietary habits and cigarette smoking.

METHODS

A randomized, controlled intervention study used the work site as the unit of intervention and analysis; it included 24 predominantly manufacturing work sites in Massachusetts (250-2500 workers per site). Behaviors were assessed in self-administered surveys (n = 2386; completion rates = 61% at baseline, 62% at final). Three key intervention elements targeted health behavior change: (1) joint worker-management participation in program planning and implementation, (2) consultation with management on work-site environmental changes, and (3) health education programs.

RESULTS

Significant differences between intervention and control work sites included reductions in the percentage of calories consumed as fat (2.3% vs 1.5% kcal) and increases in servings of fruit and vegetables (10% vs 4% increase). The intervention had a significant effect on fiber consumption among skilled and unskilled laborers. No significant effects were observed for smoking cessation.

CONCLUSIONS

Although the size of the effects of this intervention are modest, on a populationwide basis effects of this size could have a large impact on cancer-related and coronary heart disease end points.

Social support and readiness to make dietary changes

This article examines the relationship between reported social support and readiness to increase fruit and vegetable consumption, based on the Transtheoretical Stage of Change Model. Data were collected as part of the baseline assessments for a work site intervention study promoting increased consumption of fruits and vegetables. Among workers who did not live alone, household support was significantly higher for those of Hispanic and African American heritage than other groups, and was also higher among men, nonsmokers, and those living with adults compared to those living only with children. In multivariate analyses, coworker support was significantly associated with being in preparation compared to precontemplation/contemplation. Household support was not significantly related to readiness to change in multivariate analyses. The effectiveness of work site nutrition education interventions is likely to be enhanced by teaching participants to provide social support to coworkers and family members.

Vitamins E plus C and interacting conutrients required for optimal health. A critical and constructive review of epidemiology and supplementation data regarding cardiovascular disease and cancer

Antioxidants are crucial components of fruit/vegetable rich diets preventing cardiovascular disease (CVD) and cancer: plasma vitamins C, E, carotenoids from diet correlate prevalence of CVD and cancer inversely, low levels predict an increased risk of individuals which is potentiated by combined inadequacy (e.g., vitamins C + E, C + carotene, A + carotene); self-prescribed rectification of vitamins C and E at adequacy of other micronutrients reduce forthcoming CVD, of vitamins A, C, E, carotene and conutrients also cancer; randomized exclusive supplementation of beta-carotene +/- vitamin A or E lack benefits except prostate cancer reduction by vitamin E, and overall cancer reduction by selenium; randomized intervention with synchronous rectification of vitamins A + C + E + B + minerals reduces CVD and counteracts precancerous lesions; high vitamin E supplements reveal potentials in secondary CVD prevention. Plasma values desirable for primary prevention: > or = 30 mumol/l lipid-standardized vitamin E (alpha-tocopherol/cholesterol > or = 5.0 mumol/mmol); > or = 50 mumol/l vitamin C aiming at vitamin C/vitamin E ratio > 1.3-1.5; > or = 0.4 mumol/l beta- (> or = 0.5 mumol/l alpha+ beta-) carotene.

CONCLUSIONS

In CVD vitamin E acts as first risk discriminator, vitamin C as second one; optimal health requires synchronously optimized vitamins C + E, A, carotenoids and vegetable conutrients.

Development of a school-based nutrition intervention for high school students: Gimme 5

PURPOSE

To describe a 4-year intervention targeting fruit/vegetable consumption by high school students.

DESIGN

This is a cohort study involving six pairs of schools (n = 12) matched on gender, race, enrollment, and location with schools randomly assigned within pairs to intervention or control conditions.

SETTING

Twelve Archdiocese of New Orleans high schools.

SUBJECTS

Cohort was defined as students (n = 2339) who were ninth-graders in the 1993-94 school year who provided baseline data.

INTERVENTION

Four components of the intervention are: (1) school-wide media-marketing campaign, (2) school-wide meal and snack modification, (3) classroom workshops and supplementary subject matter activities, and (4) parental involvement.

MEASURES

Focus groups were conducted for target population input and program development. Process evaluation included student feedback on media-marketing intervention materials and activities reported here. Process measures also included school meal participation, student characteristics, and verification of intervention activities.

RESULTS

Focus groups identified barriers to increased consumption of fruit and vegetables as lack of availability, variety, and inconsistency in taste. Student attitudes were favorable regarding a school program to improve diet and parental involvement. Low consumption of fruits/vegetables was reported. After a 2-month school-wide program introduction utilizing various media-marketing materials and activities, 93% of students were aware of the program and 96% could identify the healthy eating message.

CONCLUSIONS

Program development can be guided and enriched by student input via focus groups. Media-marketing activities effectively delivered health messages and attracted students' attention. Materials and activities used were acceptable channels for increasing awareness, positive attitudes, and knowledge about fruits/vegetables.

Epidemiology of lung cancer: a worldwide epidemic

OBJECTIVES

To examine patterns and trends in lung cancer and the risk factors associated with development of this disease.

DATA SOURCES

Epidemiologic studies, research studies, review articles, and government reports pertaining to epidemiology of lung cancer.

CONCLUSION

Epidemiological evidence documents that most lung cancer cases could be prevented. With 3 million persons worldwide dying annually from lung cancer attributable to smoking, cigarette smoking remains the number one target for public health action to reduce cancer risk in the general population.

IMPLICATIONS FOR NURSING PRACTICE

A useful resource for nurses is the descriptive epidemiology of lung cancer, a knowledge base that identifies who is at risk. Linking this risk information with knowledge of strategies for reducing these risks provides a basis for planning and implementing interventions to prevent lung cancer.

Nutrition and lung cancer

Epidemiologic evidence on the relationship between nutrition and lung cancer is reviewed. Observational studies of diet and lung cancer, both prospective and retrospective, continue to suggest strongly that increased vegetable and fruit intake is associated with reduced risk in men and women; in various countries; in smokers, ex-smokers, and never-smokers; and for all histologic types of lung cancer. Prospective studies of blood beta-carotene levels, arguably the best available biomarker of vegetable and fruit intake, indicate that low levels are predictive of increased lung cancer incidence. However, in a randomized, placebo-controlled clinical trial in male smokers, lung cancer incidence and total mortality were increased significantly among the men receiving beta-carotene supplements. If beta-carotene can prevent lung carcinogenesis, which the trial cannot rule out, then the dosage, duration of use, method of administration, and/or subpopulation are critical. Ongoing clinical trials, some of which include women, will provide much-needed information. Other carotenoids, other phytochemicals, and associated dietary patterns may explain the beneficial effects of vegetables and fruits and have not been explored adequately in epidemiologic work. Several observational epidemiologic studies, both prospective and retrospective, have indicated that diets high in fat, saturated fat, and cholesterol may increase the risk of lung cancer and that the effect is not mediated through vegetable and fruit intake. The relationship, although not yet established, merits further investigation. Since beta-carotene can function as an antioxidant, other micronutrients with this potential, specifically vitamins E and C and selenium, also have been proposed to reduce lung cancer risk. However, the totality of the epidemiologic evidence is not, at present, persuasive for any one of these micronutrients.

Excess mortality among cigarette smokers: changes in a 20-year interval

OBJECTIVES

This study was undertaken to examine changes in smoking-specific death rates from the 1960s to the 1980s.

METHODS

In two prospective studies, one from 1959 to 1965 and the other from 1982 to 1988, death rates from lung cancer, coronary heart disease, and other major smoking-related diseases were measured among more than 200,000 current smokers and 480,000 lifelong non-smokers in each study.

RESULTS

From the first to the second study, lung cancer death rates (per 100,000) among current cigarette smokers increased from 26 to 155 in women and from 187 to 341 in men; the increase persisted after current daily cigarette consumption and years of smoking were controlled for. Rates among nonsmokers were stable. In contrast, coronary heart disease and stroke death rates decreased by more than 50% in both smokers and nonsmokers. The all-cause rate difference between smokers and nonsmokers doubled for women but was stable for men.

CONCLUSIONS

Premature mortality (the difference in all-cause death rates between smokers and nonsmokers) doubled in women and continued unabated in men from the 1960s to the 1980s. Lung cancer surpassed coronary heart disease as the largest single contributor to smoking-attributable death among White middle-class smokers.

Critical assessment of the epidemiological data concerning the impact of antioxidant nutrients on cancer and cardiovascular disease

Epidemiological studies strongly suggest that high intakes of foods rich in beta carotene, as well as those rich in vitamin E or vitamin C, reduce the risk of some but not all cancers and cardiovascular disease. It is difficult to determine whether these antioxidant nutrients per se are the sole protective agents or whether other factors associated with foods containing them contribute to the foods' protective effects. With respect to vitamin E, a number of studies where dietary and supplementary vitamin E were clearly differentiated, a reduced risk of certain cancers or cardiovascular disease from supplemental vitamin E but not from dietary vitamin E was demonstrated. This provides strong presumptive evidence that high intakes of vitamin E per se provide a health benefit. Only a few intervention studies with specific nutrients are available and results are inconsistent.

Psychosocial factors influencing low fruit and vegetable consumption

A major national health campaign has recently been initiated to promote consumption of 5 or more servings of fruits and vegetables each day. This paper investigates psychosocial factors related to fruit and vegetable consumption to understand better who might be receptive and who might resist the national 5-A-Day campaign. We studied 405 adult respondents to a random-digit dial telephone survey. Applying the Transtheoretical Model, respondents were classified by stage of readiness to adopt the practice of eating 5 or more fruits and vegetables each day. Logistic regression models were developed for persons consuming 2 or fewer servings daily and for persons in the Precontemplation stage. Education was directly related to fruit and vegetable intake and indirectly related to being in the Precontemplation stage. Males were twice as likely as females to be in the Precontemplation stage and eat fewer than 2 servings a day. Of special interest, respondents with children at home were at greater risk of eating 2 or fewer servings a day than those without children at home (OR = 1.63; 95% CI, 1.06-2.52). These results imply that stage of readiness to change should be considered as well as other factors in planning interventions for increasing fruit and vegetable consumption.

Vitamin A and cancers of the breast, large bowel, and prostate: epidemiologic evidence

In this review we have examined epidemiological data from a variety of sources to assess the relation between vitamin A intake and cancer risk. The potential for recall bias in case-control studies makes their interpretation difficult, particularly if we are searching for modest associations. Prospective data are preferable, but sparse. Studies of blood levels of carotenoids may be informative if the blood is stored at ultra-low temperatures; however, studies of blood retinol levels are largely uninformative as an index of dietary intake because blood retinol is not well correlated with intake except in vitamin A-deficient populations. We have also reviewed the evidence for an influence of vitamin A intake on the incidence of cancer at the three major cancer sites accounting for a substantial portion of cancers in developed countries. The available data are compatible with a modest inverse association between intake of vitamin A and breast cancer, although it is not clear whether this effect may be due to preformed vitamin A, carotenoids, or both. The evidence that vitamin A protects against colon cancer is unconvincing. In the case of prostate cancer, early suggestions that vitamin A may increase incidence have not been confirmed by subsequent studies. Fortunately, prospective data from a number of large ongoing cohort studies in the United States and Europe should be available within the next 5 years or so. These data will permit further assessment of potential correlations between vitamin A and cancer at various sites by analysis of much larger numbers of cases than are presently available.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers and molecular epidemiology of occupationally related cancer

Effective prevention of cancer requires sensitive early warning systems to identify groups, and ultimately individuals, who are at high risk of developing cancer and to accurately estimate the magnitude of their risk. Incorporated with molecular epidemiologic studies, biologic markers have the potential to provide quantitative human data on the biologically effective dose of carcinogens, resultant molecular effects, and genetic/acquired factors that modulate these effects. Clearly, this information is directly relevant to risk identification and to risk quantification.

Carotenoids and cancer: an update with emphasis on human intervention studies

This article gives an overview of the current state of knowledge on the cancer preventive potential of carotenoids. Numerous retrospective and prospective epidemiological studies have shown that a high intake of carotenoid-rich fruits and vegetables is associated with a decreased risk of cancer at a number of common sites. For several other cancer sites, however, the epidemiological evidence is not very consistent. A number of mechanisms for the cancer preventive properties of carotenoids have been proposed. Conversion to retinol, possibly in posthepatic tissues, would allow an effect on cellular differentiation and proliferation, and on cell-to-cell communication. Antioxidant functions could prevent free radical-induced damage to cellular DNA and other macromolecules. Immunomodulatory effects could enhance immune surveillance in tumorigenesis. In addition, non-retinol-mediated effects of carotenoids on metabolism of carcinogens and cell-to-cell communication have been shown. Observational epidemiology cannot resolve whether associations are due to a specific carotenoid, or to an associated factor in fruits and vegetables, whereas interpretation of animal studies is hampered by uncertainties in extrapolation between species, more so because the metabolism of carotenoids in most animals differs notably from that in humans. Human intervention studies on biomarkers related to cancer risk and on cancer incidence are, therefore, necessary. Human intervention studies performed so far suggest that beta-carotene can affect carcinogenesis, though not at all stages and not at all cancer sites. Implications for future human intervention research are discussed.

Environmental tobacco smoke and the risk of cancer in adults

The apparent effect of environmental tobacco smoke (ETS) exposure on cancer risk has become an important social and political issue. The risk of cancer in non-smokers is often the main reason for prohibiting or restricting smoking in public places. A number of epidemiological studies have shown an association between ETS exposure and lung cancer. However, the strength of this association has still to be estimated. Only a few studies have reported on ETS and cancer from sites other than the lung in adults. No definite conclusions can be drawn at present from a critical review of the epidemiological evidence, but the suggestion of an association is present for sinonasal cancer, while bladder cancer does not seem to be associated to ETS exposure. Positive studies are available for cancers from other sites, including the breast, the uterine cervix and the brain, but these are difficult to interpret.

Molecular epidemiology of lung cancer and the modulation of markers of chronic carcinogen exposure by chemopreventive agents

Chronic inhalation exposure to environmental carcinogens such as polycyclic aromatic hydrocarbons (PAHs), cigarette smoke, 4-aminobiphenyl (4-ABP), ethylene oxide, and styrene is associated with elevations in biomarkers such as DNA adducts, protein adducts, sister chromatid exchanges (SCEs), chromosomal aberrations, gene mutation, and/or oncogene activation. These biomarkers indicate an increased cancer risk for the exposed population, although quantitative estimates cannot be made with certainty. There is convincing epidemiological evidence that the antioxidant and free radical-scavenging vitamins C and E and beta-carotene (beta-C) protect against cancer of the lung and other epithelial tissues, with somewhat weaker evidence for retinol. Experimental studies demonstrate that these micronutrients are capable of blocking or reducing tumor formation caused by diverse carcinogens. A variety of mechanisms appear to be involved, including suppression of carcinogen activation, enhancement of carcinogen detoxification, induction of cellular differentiation, inhibition of mutagenesis, enhancement of immunologic function, and/or reduction of the formation of carcinogen-DNA adducts, SCEs, micronuclei, and other markers of genotoxic damage. Therefore, we have recently investigated the possible modifying effect of serum vitamins C and E, beta-C, and retinol on a number of such biomarkers in a case-control study of lung cancer, and in a cross-sectional study of heavy smokers. Preliminary results indicate an inhibitory effect of certain vitamins on DNA adduct formation. A significant number of human intervention trials are ongoing involving these vitamins. It appears that biomarkers can provide useful intermediate endpoints for assessment of both the mechanisms and the efficacy of chemopreventive agents.

Intake of vegetables, fruits, beta-carotene, vitamin C and vitamin supplements and cancer incidence among the elderly: a prospective study

A cohort of 11,580 residents of a retirement community initially free from cancer were followed from 1981 to 1989. A total of 1,335 incident cancer cases were diagnosed during the period. Relative risks of cancer were calculated for baseline consumption of vegetables, fruits, beta-carotene, dietary vitamin C, and vitamin supplements. After adjustment for age and smoking, no evidence of a protective effect was found for any of the dietary variables in men. However, an inverse association was observed between vitamin C supplement use and bladder cancer risk. In women, reduced cancer risks of all sites combined and of the colon were noted for combined intake of all vegetables and fruits, fruit intake alone, and dietary vitamin C. Supplemental use of vitamins A and C showed a protective effect on colon cancer risk in women. There was some suggestion that beta-carotene intake and supplemental use of vitamin A, C, and E were associated with reduced risk of lung cancer in women, but none of these results were statistically significant. These inverse associations observed in women seem to warrant further investigation, although there was inconsistency in results between the sexes.

Retinoids--"differentiation agents" for cancer treatment and prevention

The ability of vitamin A and its derivatives to induce differentiation in certain target tissues has been appreciated for nearly a century. Recently, oral all-trans retinoic acid (ATRA), a vitamin A metabolite, has been shown to induce terminal differentiation of leukemic cells in patients with acute promyelocytic leukemia (APL). Complete remissions are obtained and normal hematopoiesis is established in an outpatient setting with minimal side effects in the majority of cases. Although remissions are not durable, disseminated intravascular coagulation, a frequent complication of remission induction in APL, is avoided by oral ATRA prior to definitive chemotherapy. The molecular basis for the efficacy of ATRA in APL appears to be the involvement of the retinoic acid receptor alpha locus in the t(15;17) translocation breakpoint characteristic of APL.

No influence of beta-carotene on smoking-induced DNA damage as reflected by sister chromatid exchanges

The putative cancer-preventive potential of beta-carotene may be explained by its anti-oxidant capacity to prevent free-radical-induced DNA damage. To evaluate this hypothesis, we studied the effect of 14 weeks of beta-carotene supplementation on the frequency of sister chromatid exchanges (SCE) in lymphocytes in 143 heavy smokers in a randomized, double-blind, placebo-controlled intervention trial. Age, smoking habits and pretreatment blood levels of cotinine, beta-carotene, retinol and vitamins C and E were similar in the placebo group (n = 73) and the treatment group (n = 70). Plasma beta-carotene levels increased 13-fold in the treatment group during intervention, whereas the other parameters remained stable in both groups. Initial SCE levels were similar in the treatment and placebo groups (5.10 +/- 0.98 vs. 5.00 +/- 0.99 SCE/lymphocyte). During the intervention, both groups showed an almost identical decrease, and at the end of the intervention period there was no difference in SCE levels between the treatment and the placebo groups (4.37 +/- 0.38 vs. 4.24 +/- 0.37 SCE/lymphocyte). This study shows no protective effect of beta-carotene on DNA damage as reflected by sister chromatid exchanges in lymphocytes. Our results thus do not yield support for a cancer-preventive mechanism of beta-carotene involving this form of DNA damage. It cannot be excluded, however, that beta-carotene prevents other forms of smoking-induced DNA damage, affects other tissues, or is preventive in later stages of carcinogenesis.

Dietary beta-carotene, cigarette smoking, and lung cancer in men

A cohort of 5,080 men living in a retirement community in California (United States) and initially free from lung cancer were followed from June 1981 to December 1989. At recruitment, each study participant completed a mailed questionnaire which requested information on the subject's medical history, use of cigarettes, and usual consumption frequencies during the preceding 12 months of 44 vegetable and fruit items. Men who had never smoked had the highest mean daily intake of beta-carotene (8,505 micrograms), followed by past smokers (7,761 micrograms) and then by current smokers (6,178 micrograms). beta-Carotene intake of the subject's wife was correlated significantly with that of the husband in the 4,018 spouse pairs (r = 0.46; P = 0.0001). Among men with similar smoking habits, dietary beta-carotene intake significantly decreased with the spouse's smoking habit: never, past, and current smokers (P = 0.004; test for linear trend). During 31,477 person-years of follow-up, 125 incident cases of lung cancer were observed among the cohort of 5,080 men. Age-adjusted relative risks for lung cancer were below unity (i.e., demonstrating a reduced risk) for higher relative to lower consumption of beta-carotene, of all vegetables and fruits, and of yellow vegetables alone. However, these relative risks approached or crossed the null value when adjusted for personal smoking.

Environmental tobacco smoke. Medical and legal issues

Adequate information is available linking ETS to several medical problems, including respiratory illnesses in children and lung cancer in adults; nonetheless, continuing investigation is necessary to clarify several issues. Reliable information needs to be gathered on the quantity and fate of ETS chemicals in ordinary indoor environments; improved surveys quantifying passive smoke exposure should be tested along with the use of biologic markers to quantify exposure-dose relationships in nonsmokers. To date, legislation and private initiatives have been the most promising of the various measures to protect nonsmokers from ETS. While nonsmokers' judicial action has had variable success, it places the burden of challenging smoking on the nonsmoker, and it entails piecemeal, case-by-case resolution. On the other hand, legislation and private policies relieve the nonsmokers' burden to initiate the challenge, and they protect greater numbers of nonsmokers. Furthermore, legislation and policies may have a great number of direct and indirect effects. In the short term, legislation and policies that are adequately implemented and enforced alter the behavior of smokers in areas where smoking is prohibited and should result in a reduced concentration of tobacco smoke in those areas. In the long term, policies and legislation that restrict smoking in public places and the workplace help to reinforce nonsmoking as the normative behavior in society. Smoking restrictions increase public awareness and acceptance of health risks of tobacco smoke. The combination of altered social norms and reduced opportunities to smoke may encourage smokers to quit and nonsmokers, especially adolescents, not to start.

Vegetables, fruit, and cancer. II. Mechanisms

The epidemiologic literature on the relationship between vegetable and fruit consumption and human cancer at a variety of sites was reviewed systematically in Part I. It was concluded that consumption of higher levels of vegetables and fruit is associated consistently, although not universally, with a reduced risk of cancer at most sites, and particularly with epithelial cancers of the alimentary and respiratory tracts. Possible mechanisms by which vegetable and fruit intake might alter risk of cancer are addressed here. A large number of potentially anticarcinogenic agents are found in these food sources, including carotenoids, vitamins C and E, selenium, dietary fiber, dithiolthiones, glucosinolates and indoles, isothiocyanates, flavonoids, phenols, protease inhibitors, plant sterols, allium compounds, and limonene. These agents have both complementary and overlapping mechanisms of action, including the induction of detoxification enzymes, inhibition of nitrosamine formation, provision of substrate for formation of antineoplastic agents, dilution and binding of carcinogens in the digestive tract, alteration of hormone metabolism, antioxidant effects, and others. It appears extremely unlikely that any one substance is responsible for all the associations seen. Possible adverse effects of vegetable and fruit consumption are also examined. One way to consider the relationships reviewed here is to hypothesize that humans are adapted to a high intake of plant foods that supply substances crucial to the maintenance of the organism, but only some of which are currently called 'essential nutrients.' Cancer may be the result of reducing the level of intake of foods that are metabolically necessary--it may be a disease of maladaptation.