A multicenter case-control study of diet and lung cancer among non-smokers

Epidemiology of lung cancer: ACCP evidence-based clinical practice guidelines (2nd edition)

BACKGROUND

The objective of this study was to summarize the published literature concerning the epidemiology of lung cancer.

METHODS

A narrative review of published evidence was conducted, identifying and summarizing key reports that describe the occurrence of lung cancer in populations and factors that affect lung cancer risk.

RESULTS

In the United States, lung cancer remains the leading cause of cancer death in both men and women, even though an extensive list of modifiable risk factors has long been identified. The predominant cause of lung cancer is exposure to tobacco smoke, with active smoking causing most cases but passive smoking also contributing to the lung cancer burden.

CONCLUSIONS

The reductions in smoking prevalence in men that occurred in the late 1960s through the 1980s will continue to drive lung cancer mortality rates downward in men during the first portion of this century, but rates in women have not yet begun to decrease. Fortunately, exposures to major occupational respiratory carcinogens have largely been controlled, but the population is still exposed to environmental causes of lung cancer, including radon, the second leading cause of lung cancer death.

The U.S. Food and Drug Administration's evidence-based review for qualified health claims: tomatoes, lycopene, and cancer

Several studies have reported an inverse association between tomato and/or lycopene intake and the risk of some types of cancer. In 2004, the U.S. Food and Drug Administration (FDA) received two petitions for qualified health claims regarding tomatoes, lycopene, and the risk reduction for some forms of cancer. Health claims that characterize the relationship between a food or food component and a disease or health-related condition require premarket approval by FDA to be included on the labels of conventional foods and dietary supplements. Here we describe FDA's review of the scientific data for tomato and/or lycopene intake with respect to risk reduction for certain forms of cancer. The FDA found no credible evidence to support an association between lycopene intake and a reduced risk of prostate, lung, colorectal, gastric, breast, ovarian, endometrial, or pancreatic cancer. The FDA also found no credible evidence for an association between tomato consumption and a reduced risk of lung, colorectal, breast, cervical, or endometrial cancer. The FDA found very limited evidence to support an association between tomato consumption and reduced risks of prostate, ovarian, gastric, and pancreatic cancers.

Meat and fish consumption and risk of lung cancer: A case-control study in Galicia, Spain

Diet is one of the elements that may influence the development of lung cancer. To ascertain the relationship between meat and fish consumption and the appearance of this disease, a case-control study was conducted on a population in Galicia (NW Spain), with a sample of 295 cases and 322 controls. All cases had histologic confirmation, and controls were individuals who were attending the hospital to undergo trivial surgery. All subjects were over 35, and sampling was based on sex frequency. Frequent consumption of meat seemed to have a protective effect, with an OR of 0.24 (95% CI 0.11-0.50), an effect that was maintained for pork consumption (OR 0.35; 95% CI 0.18-0.67). In contrast, consumption of fish showed an association with lung cancer, with an OR of 1.67 (95% CI 0.99-2.81), an association that extended to both white (OR 1.61 95% CI 0.93-2.79) and blue fish (OR 2.03 95% CI 1.23-3.34). Consumption of meat seems to reduce the risk of lung cancer, whereas consumption of fish could exert an influence by increasing the risk of this disease.

Fruit and vegetable consumption and lung cancer risk: Updated information from the European Prospective Investigation into Cancer and Nutrition (EPIC)

The association of fruit and vegetable consumption and lung cancer incidence was evaluated using the most recent data from the European Prospective Investigation into Cancer and Nutrition (EPIC), applying a refined statistical approach (calibration) to account for measurement error potentially introduced by using food frequency questionnaire data. Between 1992 and 2000, detailed information on diet and life-style of 478,590 individuals participating in EPIC was collected. During a median follow-up of 6.4 years, 1,126 lung cancer cases were observed. Multivariate Cox proportional hazard models were applied for statistical evaluation. In the whole study population, fruit consumption was significantly inversely associated with lung cancer risk while no association was found for vegetable consumption. In current smokers, however, lung cancer risk significantly decreased with higher vegetable consumption; this association became more pronounced after calibration, the hazard ratio (HR) being 0.78 (95% CI 0.62-0.98) per 100 g increase in daily vegetable consumption. In comparison, the HR per 100 g fruit was 0.92 (0.85-0.99) in the entire cohort and 0.90 (0.81-0.99) in smokers. Exclusion of cases diagnosed during the first 2 years of follow-up strengthened these associations, the HR being 0.71 (0.55-0.94) for vegetables (smokers) and 0.86 (0.78-0.95) for fruit (entire cohort). Cancer incidence decreased with higher consumption of apples and pears (entire cohort) as well as root vegetables (smokers). In addition to an overall inverse association with fruit intake, the results of this evaluation add evidence for a significant inverse association of vegetable consumption and lung cancer incidence in smokers.

Dietary zinc, copper and selenium, and risk of lung cancer

Zinc, copper and selenium are important cofactors for several enzymes that play a role in maintaining DNA integrity. However, limited epidemiologic research on these dietary trace metals and lung cancer risk is available. In an ongoing study of 1,676 incident lung cancer cases and 1,676 matched healthy controls, we studied the associations between dietary zinc, copper and selenium and lung cancer risk. Using multiple logistic regression analysis, the odds ratios (OR) and 95% confidence intervals (CI) of lung cancer for all subjects by increasing quartiles of dietary zinc intake were 1.0, 0.80 (0.65-0.99), 0.64 (0.51-0.81), 0.57 (0.42-0.75), respectively (p trend = 0.0004); similar results were found for men. For dietary copper, the ORs and 95% CI for all subjects were 1.0, 0.59 (0.49-0.73), 0.51 (0.41-0.64), 0.34 (0.26-0.45), respectively (p trend < 0.0001); similar reductions in risk and trend were observed by gender. Dietary selenium intake was not associated with risk, except for a significant inverse trend (p = 0.04) in men. Protective trends (p < 0.05) against lung cancer with increased dietary zinc intake were also found for all ages, BMI > 25, current smokers, pack-years < or =30, light drinkers and participants without emphysema. Increased dietary copper intake was associated with protective trends (p < 0.05) across all ages, BMI, smoking and vitamin/mineral supplement categories, pack-years < or =30 and 30.1-51.75 and participants without emphysema. Our results suggest that dietary zinc and copper intakes are associated with reduced risk of lung cancer. Given the known limitations of case-control studies, these findings must be interpreted with caution and warrant further investigation.

Fruit and vegetables in cancer prevention

Our aim was to review the epidemiological literature on possible cancer-preventive effects of the consumption of fruits and vegetables in humans, to quantify the effect of high versus low consumption of fruits and vegetables, and to give an overall assessment of the existing evidence. We based our work on an expert meeting conducted by the International Agency for Research on Cancer in 2003. A qualitative reading and evaluation of relevant articles on the cancer-preventive effect of the consumption of fruits and vegetables was made followed by the calculation of the mean relative risk and range for cohort and case-control studies separately. The possible population-preventable fraction for modifying diet in relation to fruit and vegetable consumption was calculated as well as an overall statement about the degree of evidence for the cancer-preventive effect of fruit and vegetable consumption for each cancer site. There is limited evidence for a cancer-preventive effect of the consumption of fruits and vegetables for cancer of the mouth and pharynx, esophagus, stomach, colon-rectum, larynx, lung, ovary (vegetables only), bladder (fruit only), and kidney. There is inadequate evidence for a cancer-preventive effect of the consumption of fruits and vegetables for all other sites. Applying this range of risk difference to the range of prevalence of low intake, the preventable fraction for low fruit and vegetable intake would fall into the range of 5-12%. It is important to recognize that this is only a crude range of estimates and that the proportion of cancers that might be preventable by increasing fruit and vegetable intake may vary beyond this range for specific cancer sites and across different regions of the world.

Polymorphisms of methionine synthase and methionine synthase reductase and risk of lung cancer: a case-control analysis

Although tobacco is the major lung cancer risk factor, folate deficiency has also been implicated as a risk. Methionine synthase (MS; gene symbol, MTR) and methionine synthase reductase (MSR; gene symbol, MTRR) play important roles in the folate metabolism pathway. It was hypothesized that polymorphisms of MTR and MTRR are associated with lung cancer risk and interact with dietary intake of folate-related nutrients in lung cancer etiology. In a hospital-based, case-control study of 1,035 lung cancer cases and 1,148 controls of non-Hispanic whites, frequency matched by age, sex, ethnicity and smoking status, the MTR 2756A>G and MTRR 66A>G polymorphisms were genotyped. It was found that the MTRRG allele was associated with a significantly increased lung cancer risk [adjusted odd ratio (OR)=1.34, 95% confidence interval (CI)=1.06-1.70 for the AG genotype and OR=1.39, 95% CI=1.08-1.78 for the GG genotype compared to the AA genotype]. Further analysis suggested some evidence of gene-diet interactions between the MTRR 66A>G polymorphism and dietary intake of total folate and vitamin B12. When the two polymorphisms were evaluated together by the number of the variant alleles (i.e. the MTR2756G and MTRR66A), lung cancer risk was significantly increased in a dose-dependent manner (Ptrend=0.045). The risk of lung cancer was 1.29 (0.98-1.69) for one variant allele, and 1.36 (1.04-1.77) for two or more variant alleles compared to the wild-type (0 variant allele) genotype. In conclusion, our data provide evidence supporting the association between the MTR 2756A>G and MTRR 66A>G polymorphisms and lung cancer risk, which may be modulated by dietary nutrient intake.

Never smokers and lung cancer risk: a case-control study of epidemiological factors

We performed an analysis of potential epidemiological risk factors for lung cancer using data from 280 cases and 242 hospital-based controls, all lifetime never smokers (those who had smoked <100 cigarettes in their lifetimes) and frequency matched on age, gender and ethnicity. The data on demographic characteristics, medical history of respiratory diseases (asthma, emphysema, pneumonia and hay fever), weight and height, family history, female characteristics and environmental tobacco smoke (ETS) and dust exposure were derived from personal interviews. We performed a logistic regression analysis of these variables adjusting for age, gender, ethnicity, income and years of education. Exposure to ETS (OR = 2.08, 95% CI [1.25-3.43]) and dusts (OR = 2.43, 95% CI [1.53-3.88]) were associated with significantly increased risk. In the analysis for joint effects, exposure to both ETS and dusts conferred a higher risk (OR = 3.25, 95% CI [1.58-6.70]) than exposure to either alone. Family history of any cancer with onset before age 50 in at least 1 first degree relative was a significant risk predictor (OR = 1.70, 95% CI [1.10-2.64]). Individuals with a self-reported physician-diagnosed history of hay fever, but not asthma, had a decreased lung cancer risk (OR = 0.57, 95% CI [0.35-0.92]). In the multivariate analysis, exposure to ETS and dusts, and family history of cancer with onset before age 50 were significant risk factors, while a history of hay fever (occurring without asthma) was significantly protective.

Lung cancer risks in relation to vegetable and fruit consumption and smoking

In a case-control study on lung cancer, risk was analysed in relation to smoking habits and frequency of vegetable and fruit consumption. Lung cancer cases in West Sweden and population controls were interviewed using a questionnaire where the frequency of consumption of dietary items and smoking habits were assessed. The material presented comprises 177 female and 359 male confirmed cases of lung cancer and 916 population controls. There was a dose-response relationship in regard to the number of cigarettes smoked and the number of years smoked, the latter factor being more important. After adjustment for number of cigarettes smoked/day and number of years smoked, the risk for those who seldom consumed vegetables was about twice of that among those who consumed vegetables frequently, both among nonsmokers, smokers and former smokers. This risk increase in relation to vegetable consumption also was present for different smoking categories. A similar tendency, although less pronounced, was found for fruit consumption. The results demonstrate that dietary factors are related to the risk for lung cancer, although smoking is the dominant risk factor.

Sex differences in risk of lung cancer associated with methylene-tetrahydrofolate reductase polymorphisms

Methylenetetrahydrofolate reductase (MTHFR) catalyzes the metabolism of folate and nucleotides needed for DNA synthesis and repair. Variations in MTHFR functions likely play roles in the etiology of lung cancer. The MTHFR gene has three nonsynonymous single nucleotide polymorphisms (i.e., C677T, A1298C, and G1793A) that have a minor allele frequency of >5%. We investigated the associations between the frequencies of MTHFR variant genotypes and risk of lung cancer in a hospital-based case-control study of 1,051 lung cancer patients and 1,141 cancer-free controls in a non-Hispanic White population. We found that compared with the MTHFR 1298AA genotype, the 1298CC genotype was associated with a significantly increased risk of lung cancer in women [(odds ratio (OR), 2.09; 95% confidence interval (95% CI), 1.32-3.29)] but not in men (OR, 0.95; 95% CI, 0.62-1.45). The MTHFR 677TT genotype was associated with a significantly decreased risk of lung cancer in women (OR, 0.60; 95% CI, 0.40-0.92) but not in men. No association was found between the MTHFR G1793A polymorphism and risk of lung cancer. Further analysis suggested evidence of gene-dietary interactions between the MTHFR C677T polymorphism and dietary intake of vitamin B6, vitamin B12, and methionine in women and evidence of gene-environment interactions between the MTHFR C677T and A1298C polymorphisms and tobacco smoking in men. In conclusion, the polymorphisms of MTHFR may contribute to the risk of lung cancer in non-Hispanic Whites and modify the risk associated with the dietary and environmental exposure in a sex-specific manner.

Does insufficient adjustment for smoking explain the preventive effects of fruit and vegetables on lung cancer?

Recent reports have raised the question, whether the previously observed protective effects of high intake of fruit and vegetables on the risk of lung cancer were due to insufficient adjustment for smoking leading to residual confounding. Association of intake of fruit and vegetables on lung cancer risk was examined, using the Danish prospective cohort study, "Diet, Cancer and Health". Participants completed a food-frequency and lifestyle questionnaire, and age-standardized incidence rates and rate ratios were estimated for quartiles of dietary exposure. In 1993-2001, 247 out of the 54158 participants were diagnosed with lung cancer. The incidence rate of lung cancer was highest in the lowest quartile of intake of plant food (fruit, vegetables, legumes and potatoes) and the age-standardized rate ratio of lung cancer decreased significantly with increasing intake of plant food to 0.35 (95% CI, 0.27-0.45) but after control for smoking it was attenuated to 0.65 (95% CI, 0.45-0.93). The incidence rate differences of current smokers with high (> or = 400 g per day) and low (< 400 g per day) daily intake of plant food were independent of smoking intensity; assuming a true biological protective effect, 80-90 lung cancer cases per 100000 current smokers could be prevented in our cohort if all smokers had a high intake of plant food. The observed inverse association between high intakes of plant food seems chiefly to be a real protective effect, and not solely due to residual confounding.

Dietary carotenoids and risk of lung cancer in a pooled analysis of seven cohort studies

Intervention trials with supplemental beta-carotene have observed either no effect or a harmful effect on lung cancer risk. Because food composition databases for specific carotenoids have only become available recently, epidemiological evidence relating usual dietary levels of these carotenoids with lung cancer risk is limited. We analyzed the association between lung cancer risk and intakes of specific carotenoids using the primary data from seven cohort studies in North America and Europe. Carotenoid intakes were estimated from dietary questionnaires administered at baseline in each study. We calculated study-specific multivariate relative risks (RRs) and combined these using a random-effects model. The multivariate models included smoking history and other potential risk factors. During follow-up of up to 7-16 years across studies, 3,155 incident lung cancer cases were diagnosed among 399,765 participants. beta-Carotene intake was not associated with lung cancer risk (pooled multivariate RR = 0.98; 95% confidence interval, 0.87-1.11; highest versus lowest quintile). The RRs for alpha-carotene, lutein/zeaxanthin, and lycopene were also close to unity. beta-Cryptoxanthin intake was inversely associated with lung cancer risk (RR = 0.76; 95% confidence interval, 0.67-0.86; highest versus lowest quintile). These results did not change after adjustment for intakes of vitamin C (with or without supplements), folate (with or without supplements), and other carotenoids and multivitamin use. The associations generally were similar among never, past, or current smokers and by histological type. Although smoking is the strongest risk factor for lung cancer, greater intake of foods high in beta-cryptoxanthin, such as citrus fruit, may modestly lower the risk.

Fruits, vegetables and lung cancer: a pooled analysis of cohort studies

Inverse associations between fruit and vegetable consumption and lung cancer risk have been consistently reported. However, identifying the specific fruits and vegetables associated with lung cancer is difficult because the food groups and foods evaluated have varied across studies. We analyzed fruit and vegetable groups using standardized exposure and covariate definitions in 8 prospective studies. We combined study-specific relative risks (RRs) using a random effects model. In the pooled database, 3,206 incident lung cancer cases occurred among 430,281 women and men followed for up to 6-16 years across studies. Controlling for smoking habits and other lung cancer risk factors, a 16-23% reduction in lung cancer risk was observed for quintiles 2 through 5 vs. the lowest quintile of consumption for total fruits (RR = 0.77; 95% CI = 0.67-0.87 for quintile 5; p-value, test for trend < 0.001) and for total fruits and vegetables (RR = 0.79; 95% CI = 0.69-0.90; p-value, test for trend = 0.001). For the same comparison, the association was weaker for total vegetable consumption (RR = 0.88; 95% CI = 0.78-1.00; p-value, test for trend = 0.12). Associations were similar between never, past, and current smokers. These results suggest that elevated fruit and vegetable consumption is associated with a modest reduction in lung cancer risk, which is mostly attributable to fruit, not vegetable, intake. However, we cannot rule out the possibility that our results are due to residual confounding by smoking. The primary focus for reducing lung cancer incidence should continue to be smoking prevention and cessation.

Fruits and vegetables and lung cancer: Findings from the European Prospective Investigation into Cancer and Nutrition

Intake of fruits and vegetables is thought to protect against the development of lung cancer. However, some recent cohort and case-control studies have shown no protective effect. We have assessed the relation between fruit and vegetable intake and lung cancer incidence in the large prospective investigation on diet and cancer, the European Prospective Investigation Into Cancer and Nutrition (EPIC). We studied data from 478,021 individuals that took part in the EPIC study, who were recruited from 10 European countries and who completed a dietary questionnaire during 1992-1998. Follow-up was to December 1998 or 1999, but for some centres with active follow-up to June 2002. During follow-up, 1,074 participants were reported to have developed lung cancer, of whom 860 were eligible for our analysis. We used the Cox proportional hazard model to determine the effect of fruit and vegetable intake on the incidence of lung cancer. We paid particular attention to adjustment for smoking. Relative risk estimates were obtained using fruit and vegetable intake categorised by sex-specific, cohort-wide quintiles. After adjustment for age, smoking, height, weight and gender, there was a significant inverse association between fruit consumption and lung cancer risk: the hazard ratio for the highest quintile of consumption relative to the lowest being 0.60 (95% Confidence Interval 0.46-0.78), p for trend 0.0099. The association was strongest in the Northern Europe centres, and among current smokers at baseline, and was strengthened when the 293 lung cancers diagnosed in the first 2 years of follow-up were excluded from the analysis. There was no association between vegetable consumption or vegetable subtypes and lung cancer risk. The findings from this analysis can be regarded as re-enforcing recommendations with regard to enhanced fruit consumption for populations. However, the effect is likely to be small compared to smoking cessation.

Diet as risk for lung cancer: a Swedish case-control study

A case-control study was undertaken to study lung cancer in relation to dietary habits, occupational exposure, and living in urban or country areas. Suspect lung cancer cases in West Sweden and population controls were interviewed using a food frequency questionnaire. The study comprised 177 female and 359 male cases and 916 controls. The cases mainly comprised former and current smokers (82% female, 95% male). For the analysis, cases were divided into the histological diagnoses adenocarcinoma and squamous cell, small cell, and adenosquamous cell carcinomas, as well as into smoking categories. A high frequency of consumption of vegetables was significantly related to a lower risk for adenocarcinoma and squamous cell and adenosquamous cell carcinoma among men and adenocarcinoma among women. A low odds ratio in the highest quartile of vegetable consumption in men was seen in all smoking categories. There were no significant protective effects from fruit in the different lung cancer subgroups, although a significant trend was found for heavy-smoking females. A high consumption of milk was related to an increased risk for lung cancer, especially adenosquamous cell carcinoma. The results suggest that the protective effect or risk due to dietary factors may affect different forms of lung cancer. The results from this as well as previous studies suggest a complex interaction between diet and lung cancer risk, involving the types of lung cancer as well as consumption patterns in the population.

A population-based case-control study on fruit and vegetable intake and lung cancer: a paradox effect?

A population-based case-control study was carried out in Northwest Spain to analyze the effect of fruit and vegetable intake on the appearance of lung cancer. A non-significant protective association was found for overall consumption of leafy green and other vegetables, with consumption once a day or more vs. less than once a week yielding odds ratios of 0.63 [95% confidence interval (CI) = 0.24-1.63] for leafy green vegetables and 0.64 (95% CI = 0.30-1.36) for other vegetables. A significant protective association was found for potato consumption. No protective associations were recorded for fruit, whether overall or singly; instead, fruit consumption once a day or more vs. less than once a week registered a risk of 2.16 (95% CI = 1.02-4.58). Although the possibility that this effect may be due to a phenomenon of reverse causation cannot be ruled out, these results could support other reports and hypotheses which indicate that the protective effect of fruit might not be as pronounced as generally thought.

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.

Epidemiology of lung cancer

In the United States, lung cancer remains the leading cause of cancer death in both men and women even though an extensive list of risk factors has been well-characterized. Far and away the most important cause of lung cancer is exposure to tobacco smoke through active or passive smoking. The reductions in smoking prevalence in men that occurred in the late 1960s through the 1980s will continue to drive the lung cancer mortality rates downward in men during the first portion of this century. This favorable trend will not persist unless further reductions in smoking prevalence are achieved.

Risk factors for lung cancer among Canadian women who have never smoked

Risk factors for lung cancer among women who had never smoked were assessed in a case-control study of 161 newly diagnosed histologically confirmed cases and 483 population controls between 1994 and 1997 in eight Canadian provinces. Measurement included socio-economic status, smoking habits, alcohol use, diet, residential and occupational histories and exposure to environmental tobacco smoke (ETS). Dose-response associations were observed for consumption of tea, adjusted odds ratios (ORs) 0.6 (95% confidence interval (CI) = 0.3-0.9) for 1-7 cups per week and 0.4 (95% CI = 0.2-0.7) for > or = 8 cups per week (P = 0.0008), and smoked meat, adjusted ORs 1.3 (95% CI = 0.8-2.3) for 0.5 slice per week and 2.1 (95% CI = 1.1-4.0) for >0.5 slice per week (P = 0.02). Regular use of shortening in cooking was also related to lung cancer. Increased ORs with borderline significance were found for total consumption of meat, eggs or French fries and fried potatoes. Passive exposure to ETS at home (or at work) may be associated with lung cancer risk among never-smoker women; the adjusted ORs were 0.7 (95% CI = 0.2-2.3), 1.2 (95% CI = 0.4-3.2), 1.5 (95% CI = 0.5-4.0) for 1-16, 17-30, and 31 or more years of combined residential and/or occupational ETS exposure, respectively, with a similar pattern for smoker-years of ETS exposure.

Carotenoids: separation methods applicable to biological samples

Epidemiologic and clinical studies have shown that a high intake of vegetables and fruit, with consequently high intakes and circulating concentrations of carotenoids, is associated with reduced risk of cardiovascular and other chronic diseases. The antioxidant properties of carotenoids are thought to contribute to these effects. The analysis of carotenoids in plasma, foods and tissues has thus become of interest in studies examining the role of diet in chronic disease prevention and management. High-performance liquid chromatography with ultra-violet or photodiode array detection is most often employed in routine use. We review these and other current methods for carotenoid analysis and information on sample stability relevant to epidemiological studies. The carotenoids remain an important and intriguing subject of study, with relevance to prevention of several important "lifestyle-related" diseases. Research into their physiological functions and their use as dietary markers requires sensitive, accurate and precise measurement. Further advances in these methodological areas will contribute to basic, clinical and public health research into the significance of carotenoid compounds in disease prevention.

Lycopene and the lung

The human lung, due to the oxidative and ozone stress to which it is exposed, is particularly vulnerable to oxidative damage. Concentrations of dietary antioxidants in the lung epithelial lining and lining fluids may provide protection against oxidative damage. A randomized clinical trial was conducted to study the effects of supplemental, carotenoid-rich vegetable juice (V-8) on lung function macrophage levels of carotenoids and in moderating ozone-induced lung damage. Healthy young adults (n = 23) were exposed to 0.4 ppm ozone in a chamber for 2 hr after either 2 weeks of antioxidant supplementation (including one can of V-8 juice daily) or placebo. Mean lung concentrations of lycopene increased by 12%, and lung epithelial cell DNA damage as measured by the Comet Assay decreased 20% in supplemented subjects. No change in peripheral blood lymphocyte DNA damage was observed as evidenced by no change in mean comet area or length in supplemented or placebo subjects. We were not able to separate the effects of lycopene from other carotenoids or antioxidants administered in this study; however, lycopene is the predominant carotenoid in V-8 (it represents 88% of total carotenoids). A review of the epidemiologic literature providing evidence for the effect of lycopene (diet or serum) or tomatoes on the risk of lung cancer reveals 27 observational epidemiologic studies (18 case-control and nine cohort studies) reporting relative risk (RR) estimates. RR estimates for cohort studies ranged from 0.63 to 1.24 (mean RR = 0.93, SD = 0.16). Odds ratios (OR) for case-control studies ranged from 0.27 to 0.93 (mean OR = 0.61, SD = 0.16). Both plasma levels (RR = 1.01, OR = 0.37) and estimated intakes of lycopene from dietary sources (mean RR = 0.93, RR range = 0.80-1.05; mean OR = 0.67, OR range = 0.27-0.93) were examined. Seventeen studies, three of which were cohorts, reported their results at the level of tomato consumption rather than, or in addition to, lycopene consumption (mean RR = 0.89, RR range = 0.63-1.24; mean OR = 0.61, OR range = 0.37-0.80). The published epidemiologic literature shows an interaction between study design and the relationship between lycopene and/ or tomatoes and risk of lung cancer. Overall, cohort studies did not show an association, whereas case-control studies showed a decreased risk with greater consumption of lycopene and tomatoes. Although lycopene can be found in the human lung, and there is evidence, albeit weak, for a protective association with lung cancer, its biologic role remains to be elucidated.

Risk factors for lung cancer among nonsmoking women

To evaluate risk factors for lung cancer in nonsmoking women, we used data of a case-control study conducted between 1991 and 1996 in Germany. A total of 234 female histologically confirmed lung cancer patients and 535 population controls who had never smoked more than 400 cigarettes in their lifetime were personally interviewed with respect to occupation, exposure to environmental tobacco smoke (ETS), family history of cancer, prior physician-diagnosed lung diseases or cancer and diet. One-year radon measurements in the last dwelling were performed. Odds ratios (OR) adjusted for age and region and 95% confidence intervals (CI) were calculated via logistic regression. When cumulative duration of exposure to ETS in hours was considered, the OR for high compared to not or low ETS exposed women was 2.62 (CI:1.35-5.06) for occupational exposure and OR=1.67 (CI:0.86-3.25) for spousal exposure, exhibiting a significant trend for ETS at work. Working more than 10 years in jobs or industries with known or suspected lung carcinogens was associated with OR=2.0 (CI:0.99-4.0). An elevated risk due to prior lung diseases was present for pneumonia (OR=1.6; CI:1.07-2.40) and tuberculosis (OR=1.6; CI:0.77-3.37). No significant increase in risk with increasing residential radon levels or with the presence of a family history of lung cancer was apparent. Protective effects were observed for high vs. low consumption of fresh vegetables (OR=0.5; CI:0.25-0.82) and cheese (OR=0.3, CI:0.21-0.55). ETS at work, occupational hazards and previous pneumonia may be risk factors for lung cancer in nonsmoking women, while a diet rich in fresh vegetables and cheese seems to be protective.

Lung cancer risk among Czech women: a case-control study

BACKGROUND

Few data are available to explain the ongoing increase in lung cancer mortality among Czech women. The study is aimed at examining the role of smoking and known or suspected cofactors.

METHODS

Data collected by in-person interviews from 269 female lung cancer cases and 1079 controls were analyzed using unconditional logistic regression and other methods.

RESULTS

Cigarette smoking was the most important factor associated with excess risk of lung cancer among women. Risk was increased both among current smokers (OR = 10.30), long-term ex-smokers (> or =10 years ago; OR = 3.79), and short-term ex-smokers (<10 years ago; OR = 14.63), all compared against never-smokers. In addition, significant associations with risk were found for chronic cough, chronic phlegm of less than 2-year duration, and shortness of breath. Inverse associations emerged for physical exercise and body mass index. Excess risk associated with consumption of red meat and poultry, and protective effects associated with intake of vegetables were restricted to squamous-, small-, and large-cell cancers combined, but were not apparent for adenocarcinoma.

CONCLUSIONS

While smoking has been verified to be the main determinant of lung cancer risk among Czech women, cofactors such as diet, history of lung disease, and lifestyle factors may have a contributory role.

Dietary habits and risk of lung cancer death in a large-scale cohort study (JACC Study) in Japan by sex and smoking habit

Lung cancer has increased and is the leading cause of cancer death among Japanese males. The associations of dietary habits with the risk of lung cancer death were evaluated by sex and smoking habits in this study. In the Japan Collaborative Cohort (JACC) Study, a cohort established in 1988 - 90 and consisting of 42 940 males and 55 308 females was observed for lung cancer deaths up to the end of 1997. During the observation period, 446 males and 126 females died of lung cancer. A self-administered food frequency questionnaire was used as the baseline survey. Hazard ratios for dietary factors were calculated by Cox's proportional hazards model. Among males, a high intake of ham and sausages, cheese, green-leafy vegetables, oranges, and other fruits significantly and dose-dependently decreased the risk of lung cancer death. Among females, a high intake of miso-soup, ham and sausages, and liver significantly and almost dose-dependently increased the risk. Vegetables and fruits rich in antioxidative and carcinogenic agents reduced the risk of lung cancer deaths among male smokers more than among female nonsmokers. The results among female nonsmokers were partially consistent with the hypothesis that high fat consumption increases the risk of lung cancer, especially that of adenocarcinoma.

Carotenoids are degraded by free radicals but do not affect lipid peroxidation in unilamellar liposomes under different oxygen tensions

It has been questioned whether carotenoids can act as antioxidants in biological membranes. Biological membranes can be modeled for studies of lipid peroxidation using unilamellar liposomes. Both carotenoid depletion and lipid peroxidation were increased with increasing oxygen tension in unilamellar liposomes. Carotenoids in such liposomes were found to be very sensitive to degradation by free radicals generated from iron and 2,2'-azobis(2-amidinopropane) dihydrochloride, but they were not protective against lipid peroxidation. Lycopene and beta-carotene were more sensitive to free radical attack than lutein, zeaxanthin, and beta-cryptoxanthin.

Diet and cancer prevention

Research from several sources provides strong evidence that vegetables, fruits, and whole grains, dietary fibre, certain micronutrients, some fatty acids and physical activity protect against some cancers. In contrast, other factors, such as obesity, alcohol, some fatty acids and food preparation methods may increase risks. Unravelling the multitude of plausible mechanisms for the effects of dietary factors on cancer risk will likely necessitate that nutrition research moves beyond traditional epidemiological and metabolic studies. Nutritional sciences must build on recent advances in molecular biology and genetics to move the discipline from being largely 'observational' to focusing on 'cause and effect'. Such basic research is fundamental to cancer prevention strategies that incorporate effective dietary interventions for target populations.

Diet, smoking and lung cancer: a case-control study of 1000 cases and 1500 controls in South-West England

We have examined the relationship between diet and lung cancer in a case-control study of 982 cases of lung cancer and 1486 population controls in south-west England in which subjects were interviewed personally about their smoking habits and their consumption of foods and supplements rich in retinol or carotene. Analyses were performed for 15 dietary variables, including intake of pre-formed retinol and carotene. There were significant associations (P< 0.01) with lung cancer risk for 13 of the variables, eight of which remained after adjustment for smoking. When the 15 variables were considered simultaneously, independent significant associations remained for 5: pre-formed retinol (increased risk), and fish liver oil, vitamin pills, carrots and tomato sauce (decreased risk). It is unlikely that all five associations represent biological effects, or that they can all be explained by residual confounding by smoking, or by biases. We conclude that there is at least one as yet unidentified factor that is causally related to lung cancer risk and of considerable importance in terms of attributable risk in this population.

Lung cancer in a nonsmoking underground uranium miner

Working in mines is associated with acute and chronic occupational disorders. Most of the uranium mining in the United States took place in the Four Corners region of the Southwest (Arizona, Colorado, New Mexico, and Utah) and on Native American lands. Although the uranium industry collapsed in the late 1980s, the industry employed several thousand individuals who continue to be at increased risk for developing lung cancers. We present the case of a 72-year-old Navajo male who worked for 17 years as an underground uranium miner and who developed lung cancer 22 years after leaving the industry. His total occupational exposure to radon progeny was estimated at 506 working level months. The miner was a life-long nonsmoker and had no other significant occupational or environmental exposures. On the chest X-ray taken at admission into the hospital, a right lower lung zone infiltrate was detected. The patient was treated for community-acquired pneumonia and developed respiratory failure requiring mechanical ventilation. Respiratory failure worsened and the patient died 19 days after presenting. On autopsy, a 2.5 cm squamous cell carcinoma of the right lung arising from the lower lobe bronchus, a right broncho-esophageal fistula, and a right lower lung abscess were found. Malignant respiratory disease in uranium miners may be from several occupational exposures; for example, radon decay products, silica, and possibly diesel exhaust are respiratory carcinogens that were commonly encountered. In response to a growing number of affected uranium miners, the Radiation Exposure Compensation Act (RECA) was passed by the U.S. Congress in 1990 to make partial restitution to individuals harmed by radiation exposure resulting from underground uranium mining and above-ground nuclear tests in Nevada.

Lung cancer in lifetime nonsmoking men - results of a case-control study in Germany

Epidemiological studies of lung cancer among nonsmoking men are few. This case-control study was conducted among lifetime nonsmoking men between 1990 and 1996 in Germany to examine lung cancer risk in relation to occupation, environmental tobacco smoke, residential radon, family history of cancer and previous lung disease. A total of 58 male cases with confirmed primary lung cancer and 803 male population controls who had never smoked more than 400 cigarettes in their lifetime were personally interviewed by a standardized questionnaire. In addition, 1-year radon measurements in the living and bedroom of the subjects' last dwelling were carried out. Unconditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (CI). Having ever worked in a job with known lung carcinogens was associated with a two-fold significantly increased lung cancer risk (OR = 2.2; CI = 1.0-5.0), adjusted for age and region. The linear trend test for lung-cancer risk associated with radon exposure was close to statistical significance, demonstrating an excess relative risk for an increase in exposure of 100 Bq m(-3)of 0.43 (P = 0.052). Nonsignificantly elevated effects of exposure to environmental tobacco smoke in public transportation and in social settings were observed. No associations with a family history of cancer or previous lung diseases were found. Our results indicate that occupational carcinogens and indoor radon may play a role in some lung cancers in nonsmoking men.