Interaction among heme iron, zinc, and supplemental vitamin C intake on the risk of lung cancer: Iowa Women's Health Study

Dietary iron and the risk of lung cancer

Animal models have suggested the carcinogenic effect of iron due to its oxidative potential. The lung is particularly vulnerable to oxidative stress. However, epidemiological studies investigating the association between dietary iron and the risk of lung cancer have reported inconclusive results. In this systematic review and meta-analysis, we aimed to clarify this association. Methods: We searched PubMed, Web of Science, Scopus and Google scholar for eligible articles published through May 2023 reporting the Relative Risk (RR), Hazard Ratio (HR) or Odds Ratio (OR) with 95% confidence interval (95% CI). Case-control and cohort studies that examined the relationship between dietary iron and lung cancer risk were included and review and meta-analyses articles, experimental studies, abstracts, letters to editor and studies with insufficient data were excluded. Finally, three case-control studies and 6 cohort studies were included. Random effect models were used to calculate the pooled results. Results: Nine studies (cases n=21,943, participants n=1,542,993) were included. There were no significant associations between the highest dietary total iron (heme and non-heme) (RR: 1.09, 95% CI: 0.78 to 1.51) or heme iron (RR: 1.01, 95% CI: 0.73 to 1.38) intake compared to the lowest intake with lung cancer risk. Null-associations were also observed in the subgroup analysis based on smoking status and lung cancer histology. However, in the subgroup of women (cases n=5074), heme iron was associated with a 14% increase in the risk of lung cancer (RR: 1.14, 95% CI: 1.01 to 1.29). Conclusions: The current results demonstrated that there is no significant relationship between dietary iron intake and the risk of lung cancer. However, a positive association was observed between dietary heme iron and the risk of lung cancer in women, which may require further investigation.

Dietary and supplementary vitamin C intake and the risk of lung cancer: A meta‑analysis of cohort studies

Previous cohort studies reported inconsistent findings regarding the association between dietary or supplementary vitamin C intake and lung cancer risk. These associations were investigated by conducting a meta-analysis of cohort studies. The PubMed and EMBASE databases were utilized, using keywords related to the topic from inception to April 15, 2022. Pooled effect sizes, such as relative risk (RR) or hazard ratio (HR) with 95% confidence intervals (CIs), were calculated using a random-effects model. A total of 20 cohort studies from 13 articles were included in the final analysis. In a meta-analysis of all studies, there was no significant association between dietary or supplementary vitamin C intake and lung cancer risk (RR/HR, 0.90; 95% CI, 0.80-1.01; I2=56.4%; n=20). In the subgroup meta-analysis by the source of vitamin C, dietary vitamin C intake decreased the risk of lung cancer (RR/HR, 0.82; 95% CI, 0.73-0.92; I2=42.5%; n=14), whereas there was no association between supplementary vitamin C intake and lung cancer risk (RR/HR, 1.01; 95% CI, 0.84-1.22; n=4). The present meta-analysis of cohort studies found that dietary vitamin C intake is beneficial for preventing lung cancer, whereas its supplementary intake does not have a beneficial effect.

Role of iron biomarkers and iron intakes in lung cancer risk: A systematic review and meta-analysis

BACKGROUND

The role of iron biomarkers and iron intake in the susceptibility to lung cancer is unclear. The purpose of this study was to conduct a systematic review and meta-analysis, to assess the relationship between iron levels in the body or iron intake and the risk of lung cancer.

METHOD

This review is registered with PROSPERO (number CRD 42020199776). PubMed, Web of Science, Scopus, Embase and Cochrane were used to search for studies assessing the relationship between iron and lung cancer, up to July 15, 2021. Qualitative and quantitative analysis was carried out to determine if there was a correlation between iron biomarkers/intakes and the risk of lung cancer.

RESULT

Twenty articles were included. Pooled analyses demonstrated that serum ferritin concentrations and transferrin saturation (TSAT) were significantly higher in patients with lung cancer than in healthy controls (ferritin: standardized mean differences [SMD], 0.235, 95% confidence interval [CI], 0.129, 0.341, I² = 32.1 %; TSAT: SMD, 0.07, 95 % CI, 0.018, 0.121, I² = 0 %). In contrast, serum transferrin concentrations were significantly lower in patients with lung cancer than in healthy controls (SMD, -0.591, 95 % CI, -1.18, -0.003, I² = 87.7 %). No significant effects of serum iron, lung tissue iron, bronchoalveolar lavage fluid (BALF) ferritin, or iron intake (total iron, dietary iron, heme iron, or non-heme iron) were found on lung cancer incidence.

CONCLUSION

Among the different iron biomarkers analyzed, a trend in association was only detected with serum ferritin, TSAT and transferrin concentration and no associations were found between iron intakes and the risk of lung cancer. However, more prospective studies are needed to strengthen the current evidence.

Mendelian randomization study indicates lack of causal associations between iron status and lung cancer

Observational studies provided conflicting results on the association between iron status and the risk of lung cancer. The aim of our study was to investigate the effect of genetically determined iron status on lung cancer risk using a mendelian randomization (MR) approach. Single-nucleotide polymorphisms for iron status were selected from a genome-wide meta-analysis of 48,972 subjects. Genetic association estimates for risk of lung cancer were derived from a Genome-Wide Association Study (GWAS) summary performed by the International Lung Cancer Consortium. The inverse-variance weighted method was used for the main analyses and sensitivity analyses. MR analysis demonstrated that increased genetically-predicted iron status did not causally increase risk of lung cancer. The odds ratios were 1.11 (95% CI, 0.92, 1.34; P = .26), 0.76 (95% CI, 0.52, 1.12; P = .17), 1.09 (95% CI, 0.86, 1.38; P = .47), and 0.91 (95% CI, 0.81, 1.02; P = .11) per 1 standard deviation increment of serum iron, ferritin, transferrin saturation, and transferrin levels, respectively. No observed indication of heterogeneity (P for Q > 0.05) or pleiotropy (P for intercept > 0.05) were found from the sensitivity analysis. The MR study indicated that genetic iron status was not causally associated with the risk of lung cancer, the causal relationship between iron status and lung cancer needs to be further elucidated by additional studies that strictly control for confounding factors.

Association between aspirin use and lung cancer incidence depends on high-frequency use, bodyweight, and age in U.S. adults

Background

Chemoprevention of cancer with aspirin is controversial as a primary prevention strategy. We sought to investigate the association between aspirin frequency and risk of lung cancer in The Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial.

Methods

Using data from 101,722 participants in PLCO, we used a Cox regression model coupling with propensity score to detect the association between aspirin frequency and lung cancer risk.

Results

High-frequency aspirin use significantly increased risk of lung cancer by 28% compared to no use (HR =1.28; 95% CI, 1.14–1.45; P=3.37×10⁻⁵), especially for current smoker (HR =1.30; 95% CI, 1.07–1.57; P=6.82×10⁻³). However, the increased lung cancer risk due to high-frequency aspirin use significantly decreased with increasing bodyweight (HR_interaction =0.96; 95% CI, 0.94–0.99; P=1.26×10⁻²). Further, for participants with bodyweight <80 kg, high-frequency aspirin use showed an elevated risk at <76 years of age (HR_age<76 =1.47; 95% CI, 1.25–1.73; P=3.81×10⁻⁶). Our study used propensity score under various confounding and stratification analyses by cardio-cerebrovascular status, which all presented similar evidences.

Conclusions

High-frequency aspirin use is associated with the increased risk of lung cancer. Current smoker or people with age <76 years and bodyweight <80 kg should be more cautious to high-frequency aspirin use for lung cancer chemoprevention. This study provides a new insight for lung cancer chemoprevention.

Statistical Assessment of Toxic and Essential Metals in the Serum of Female Patients with Lung Carcinoma from Pakistan

Lung cancer (LC) is the number one cancer killer of women both in the USA and around the world. Besides cigarette smoking, an important feature in the etiology of LC is its strong association with exposure of toxic metals. The primary objective of the present investigation was to assess the concentrations of toxic/essential elements (Ni, Ca, Se, Zn, Co, K, Cr, As, Cu, Na, Fe, Hg, Cd, Mg, Mn, and Pb) in the serum samples of LC female patients with female controls by atomic absorption spectrometry after wet-acid digestion procedure. Carcinoembryonic antigen (CEA) was also measured in the serum of the patients using immunoradiometric method. Comparative appraisal of the data revealed that concentrations of Cr, Mg, Cd, Pb, Hg, As, and Ni were noted to be high significantly in serum of LC female patients, while the average Fe, Co, Mn, Na, K, Zn, Ca, and Se were observed at higher levels in female controls (p < 0.05). The correlation study revealed significantly different mutual associations among the elements in the both donor groups. Markedly, variations in the elemental levels were also noted for different types (non-small cell lung cancer and small cell lung cancer) and stages (I, II, III, & IV) of LC patients. Multivariate analyses showed substantially diverse apportionment of the metals in the female patients and female controls. Hence, present findings suggest that the toxic and essential metals accumulated in the body may pose a high risk for LC progression in Pakistani females.

Association of various dietary habits and risk of lung cancer: an updated comprehensive literature review

Lung cancer remains the leading cause of cancer death in both men and women worldwide. Tobacco smoking remains the single most important factor. Recent research has focused on the role of nutrition and dietary habits on lung tumorigenesis. With many individual reports on separate dietary aspects, no single review is available in the literature that summarizes the updated studies. To our knowledge, this is the first review that comprehensively reviews the updated literature on the effect of dietary habits on lung cancer. This review was concluded in February 2019 and included all meta-analyses, systematic reviews, and literature reviews. Thirty studies were retrieved in total. Items in the diet that offer a protective effect on lung parenchyma are fruits, vegetables, fish, nuts, soy, B vitamins, vitamin D, vitamin E, vitamin C, and zinc. Changing dietary habits to decrease the risk of lung cancer can be performed in parallel with smoking cessation programs. There is a need for future studies with large sample sizes to accurately evaluate some aspects of nutrition and their effect on lung cancer risk. Physicians are encouraged to provide nutritional advice to their patients.

Haem iron intake and risk of lung cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort

BACKGROUND

Epidemiological studies suggest that haem iron, which is found predominantly in red meat and increases endogenous formation of carcinogenic N-nitroso compounds, may be positively associated with lung cancer. The objective was to examine the relationship between haem iron intake and lung cancer risk using detailed smoking history data and serum cotinine to control for potential confounding.

METHODS

In the European Prospective Investigation into Cancer and Nutrition (EPIC), 416,746 individuals from 10 countries completed demographic and dietary questionnaires at recruitment. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for incident lung cancer (n = 3731) risk relative to haem iron, non-haem iron, and total dietary iron intake. A corresponding analysis was conducted among a nested subset of 800 lung cancer cases and 1489 matched controls for whom serum cotinine was available.

RESULTS

Haem iron was associated with lung cancer risk, including after adjustment for details of smoking history (time since quitting, number of cigarettes per day): as a continuous variable (HR per 0.3 mg/1000 kcal 1.03, 95% CI 1.00-1.07), and in the highest versus lowest quintile (HR 1.16, 95% CI 1.02-1.32; trend across quintiles: P = 0.035). In contrast, non-haem iron intake was related inversely with lung cancer risk; however, this association attenuated after adjustment for smoking history. Additional adjustment for serum cotinine did not considerably alter the associations detected in the nested case-control subset.

CONCLUSIONS

Greater haem iron intake may be modestly associated with lung cancer risk.

Magnesium intake and lung cancer risk: A systematic review and meta-analysis

Magnesium may reduce the risk of lung cancer by affecting cell proliferation, inflammation and by preserving lung function; however, the results of epidemiological studies on the potential benefits of magnesium in lung pathology are inconclusive. We conducted this meta-analysis to investigate the association between magnesium intake and the risk of lung cancer. A total of 5 studies were extracted from PubMed, SCOPUS, and the Cochrane Review (to May 2018). These studies involved 58,5821 participants with 8,977 lung cancer cases. The pooled relative risk (RR) indicated a significant association between lung cancer incidence and magnesium intake (RR = 0.88, 95% CI = 0.79 to 0.98; p = 0.018). To investigate the cause of heterogeneity of these studies (I² = 75.8%, p < 0.001), we performed a subgroup analysis which was affected by the mean dose of magnesium intake, where doses of magnesium intake lower than 300 mg/d significantly decreased lung cancer risk (RR = 0.83, 95% CI = 0.70 to 0.99; p = 0.034). Increasing magnesium intake doses to over 300 mg/d did not reduce the incidence of lung cancer (RR = 0.89, 95% CI = 0.78 to 1.01; p = 0.076). Our meta-analysis suggests that magnesium intake of less than 300 mg/d may have protective effects in lung cancer.

Iron levels, genes involved in iron metabolism and antioxidative processes and lung cancer incidence

Background

Lung cancer is the most common adult malignancy accounting for the largest proportion of cancer related deaths. Iron (Fe) is an essential trace element and is a component of several major metabolic pathways playing an important role in many physiological processes. In this study we evaluated the association between Fe concentration in serum, iron metabolism parameters and genetic variaton in 7 genes involved in iron metabolism and anti-oxidative processes with the incidence of lung cancer in Poland.

Materials and methods

The study included 200 lung cancer patients and 200 matched healthy control subjects. We analyzed serum iron concentration and iron metabolism parameters (TIBC, UIBC, serum ferritin and transferrin saturation), and genotyped seven variants in seven genes: HFE, TFR1, HAMP, TF, SOD2, CAT and GPX1.

Results

Lung cancer patients compared to their matched controls had significantly higher mean serum iron level (p = 0.01), ferritin level (p = 0.007) and TIBC (p = 0.006). Analysis revealed that higher concentration of iron and ferritin (IVth quartile) compared to the lower concentration (Ist quartile) was associated with over 2-fold increased lung cancer incidence. We also found that higher transferrin saturation (p = 0.01) and lower TIBC (p<0.01) are associated with better survival of lung cancer patients. The analysis of polymorphisms in iron related genes did not reveal a significant difference between lung cancer patients and controls. However, rs10421768 in HAMP showed a borderline statistically significant correlation with lung cancer risk (OR = 2.83, p = 0.05).

Conclusions

The results of this case control study indicate that higher body iron represented by higher Fe and ferritin levels may be associated with lung cancer incidence. Rs10421768 in HAMP may be associated with about 3-times higher lung cancer risk. Higher Fe body content may be associated with better survival of lung cancer patients.

Zinc transporters are differentially expressed in human non-small cell lung cancer

Lung cancer is one of the most common human malignancies worldwide, but its oncogenesis process remains unclear. Recent studies demonstrated that zinc (Zn) and Zn transporters were associated with the development and progression of human cancers. The role of Zn transporters including ZIPs and ZnTs in lung cancer, however, has never been evaluated. Thus, we aimed to investigate the expression levels of all human Zn transporters, including 14 ZIPs and 10 ZnTs, in eight different lung cancer cell lines and paired human tumor tissues. We observed great variations in ZIPs and ZnTs mRNA levels across cell lines and human lung cancer specimens. ZIPs showed a tendency to be upregulated, while ZnTs exhibited a downward expression trend. ZIP4 was overexpressed in six lung cancer cell lines and 59% (26/44) of tumor tissues, which was consistent with results from lung cancer datasets including TCGA database. Our results indicated that the dysregulation of Zn transporters may contribute to lung tumorigenesis.

Dietary mineral intake and lung cancer risk: the Rotterdam Study

Objective

Limited data are available on the role of mineral intake in the development of lung cancer (LC). We investigated whether dietary calcium, copper, iron, magnesium, selenium and zinc intake were associated with LC risk.

Methods

We analyzed data from 5435 participants of the Rotterdam Study, a prospective population-based cohort study among subjects aged 55 years and older. At baseline (1990–1993), diet was measured by a validated food frequency questionnaire. LC events were diagnosed on the basis of pathology data and medical records. Hazard ratios (HRs) on LC for energy-adjusted mineral intake were calculated using Cox regression models while adjusting for potential confounders.

Results

During a follow-up period of 22 years, we identified 211 incident cases of LC. A higher zinc intake was associated with 42 % reduction in risk of LC (top tertile vs. first tertile: HR 0.58, 95 % CI 0.35; 0.94, P-for trend = 0.039). Similarly, high intake of iron was associated with reduced risk of LC (top tertile vs. first tertile: HR 0.58, 95 % CI 0.37; 0.92, P-for trend = 0.021). There was no association between dietary intake of calcium, copper, magnesium and selenium and LC risk.

Conclusions

Our results suggest that dietary zinc and iron intake are associated with reduced risk of LC. No evidence was found for an association between calcium, copper, magnesium and selenium intake and LC risk.

Electronic supplementary material

The online version of this article (doi:10.1007/s00394-016-1210-4) contains supplementary material, which is available to authorized users.

Health effects of different dietary iron intakes: a systematic literature review for the 5th Nordic Nutrition Recommendations

BACKGROUND

The present literature review is part of the NNR5 project with the aim of reviewing and updating the scientific basis of the 4th edition of the Nordic Nutrition Recommendations (NNR) issued in 2004.

OBJECTIVE

The objective of this systematic literature review was to assess the health effects of different intakes of iron, at different life stages (infants, children, adolescents, adults, elderly, and during pregnancy and lactation), in order to estimate the requirement for adequate growth, development, and maintenance of health.

METHODS

The initial literature search resulted in 1,076 abstracts. Out of those, 276 papers were identified as potentially relevant. Of those, 49 were considered relevant and were quality assessed (A, B, or C). An additional search on iron and diabetes yielded six articles that were quality assessed. Thus, a total of 55 articles were evaluated. The grade of evidence was classified as convincing (grade 1), probable (grade 2), suggestive (grade 3), and inconclusive (grade 4).

RESULTS

There is suggestive evidence that prevention or treatment of iron deficiency (ID) and iron deficiency anemia (IDA) improves cognitive, motoric, and behavioral development in young children, and that treatment of IDA improves attention and concentration in school children and adult women. There is insufficient evidence to show negative health effects of iron intakes in doses suggested by the NNR 4. There is insufficient evidence to suggest that normal birth weight, healthy, exclusively breast-fed infants need additional dietary iron before 6 months of life in the Nordic countries. An iron concentration of 4-8 mg/L in infant formulas seems to be safe and effective for normal birth weight infants. There is probable evidence that iron supplements (1-2 mg/kg/day) given up to 6 months of age to infants with low birth weight (<2,500 g) prevents IDA and possibly reduce the risk of behavioral problems later on. There is probable evidence that ID and IDA in pregnant women can be effectively prevented by iron supplementation at a dose of 40 mg/day from week 18-20 of gestation. There is probable evidence that a high intake of heme iron, but not total dietary, non-heme or supplemental iron, is associated with increased risk of type 2 diabetes (T2D) and gestational diabetes.

CONCLUSIONS

Overall, the evidence does not support a change of the iron intakes recommended in the NNR 4. However, one could consider adding recommendations for infants below 6 months of age, low birth weight infants and pregnant women.

Developing a heme iron database for meats according to meat type, cooking method and doneness level

BACKGROUND

Animal studies have demonstrated that iron may be related to carcinogenesis, and human studies found that heme iron can increase the formation of N-nitroso compounds, which are known carcinogens.

OBJECTIVES

One of the postulated mechanisms linking red meat intake to cancer risk involves iron. Epidemiologic studies attempt to investigate the association between heme iron intake and cancer by applying a standard factor to total iron from meat. However, laboratory studies suggest that heme iron levels in meat vary according to cooking method and doneness level. We measured heme iron in meats cooked by different cooking methods to a range of doneness levels to use in conjunction with a food frequency questionnaire to estimate heme iron intake.

METHODS

Composite meat samples were made to represent each meat type, cooking method and doneness level. Heme iron was measured using atomic absorption spectrometry and inductively coupled plasma-atomic emission spectrometry.

RESULTS

Steak and hamburgers contained the highest levels of heme iron, pork and chicken thigh meat had slightly lower levels, and chicken breast meat had the lowest.

CONCLUSIONS

Although heme iron levels varied, there was no clear effect of cooking method or doneness level. We outline the methods used to create a heme iron database to be used in conjunction with food frequency questionnaires to estimate heme iron intake in relation to disease outcome.

Humic acid enhances cigarette smoke-induced lung emphysema in mice and IL-8 release of human monocytes

Tobacco smoke is the main factor in the etiology of lung emphysema. Generally prolonged, substantial exposure is required to develop the disease. Humic acid is a major component of cigarette smoke that accumulates in smokers' lungs over time and induces tissue damage.

OBJECTIVES

To investigate whether humic acid pre-loading potentiates the development of cigarette smoke-induced lung emphysema in mice and increases IL-8 release by human monocytes.

METHODS

C57BL/6J mice received humic acid or aqueous vehicle by tracheal installation on day 0 and day 7. From day 21 to day 84, the mice were exposed to cigarette smoke or clean air for 5 days/week. Twenty-four hours after the last exposure we determined leukocytes in lung lavage, heart hypertrophy and alveolar wall destruction. Human monocytes were incubated with cigarette smoke extract (CSE), humic acid or the combination overnight.

RESULTS

Humic acid nor cigarette smoke caused alveolar wall destruction within two months. Interestingly, the combination did induce lung emphysema. Humic acid, cigarette smoke or the combination did not change leukocyte types and numbers in lung lavage fluid, but the combination caused peribronchiolar and perivascular lymphocyte infiltration. Humic acid treatment resulted in a high proportion of alveolar macrophages heavily loaded with intracellular granula. Humic acid also induces the release of IL-8 from human monocytes and enhances the CSE-induced IL-8 release.

CONCLUSIONS

Humic acid deposition in the lungs potentiates the development of cigarette smoke-induced interstitial inflammation and lung emphysema. Moreover, humic acid promotes IL-8 release from human monocytes. Since humic acid accumulates steadily in the lungs of smokers, this may provide an explanation for the natural history on late onset of this disease. The model described here offers a novel way to study emphysema and may direct the search for new therapeutic approaches.

Dietary antioxidant intake is associated with the prevalence but not incidence of age-related hearing loss

OBJECTIVES

Diet is one of the few modifiable risk factors for age-related hearing loss. We aimed to examine the link between dietary and supplement intakes of antioxidants, and both the prevalence and 5-year incidence of measured hearing loss.

DESIGN

Cross-sectional and 5-year longitudinal analyses.

SETTING

Blue Mountains, Sydney, Australia.

PARTICIPANTS

2,956 Blue Mountains Hearing Study participants aged 50+ at baseline, examined during 1997-9 to 2002-4.

MEASUREMENTS

Age-related hearing loss was measured and defined as the pure-tone average of frequencies 0.5, 1.0, 2.0 and 4.0 kHz >25 dB HL. Dietary data were collected in a semi-quantitative food frequency questionnaire, and intakes of α-carotene; β-carotene; β-cryptoxanthin; lutein and zeaxanthin; lycopene; vitamins A, C and E; iron and zinc were calculated.

RESULTS

After adjusting for age, sex, smoking, education, occupational noise exposure, family history of hearing loss, history of diagnosed diabetes and stroke, each standard deviation (SD) increase in dietary vitamin E intake was associated with a 14% reduced likelihood of prevalent hearing loss, odds ratio, OR, 0.86 (95% confidence interval, CI, 0.78-0.98). Those in the highest quintile of dietary vitamin A intake had a 47% reduced risk of having moderate or greater hearing loss (>40 dB HL) compared to those in the lowest quintile of intake, multivariable-adjusted OR 0.53 (CI 0.30-0.92), P for trend = 0.04. However, dietary antioxidant intake was not associated with the 5-year incidence of hearing loss.

CONCLUSIONS

Dietary vitamin A and vitamin E intake were significantly associated with the prevalence of hearing loss. However, dietary antioxidant intake did not increase the risk of incident hearing loss. Further large, prospective studies are warranted to assess these relationships in older adults.

No effect of meat, meat cooking preferences, meat mutagens or heme iron on lung cancer risk in the prostate, lung, colorectal and ovarian cancer screening trial

Recent epidemiological studies have suggested that red and processed meat may increase the risk of lung cancer. Possible underlying mechanisms include mutagens produced during high-temperature cooking or preservation, or formed endogenously from heme iron in meat. We used data from 99,579 participants of both screened and nonscreened arms of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, aged 55-74 years, to investigate whether meat type, cooking method, doneness level, intake of specific meat mutagens 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline] (DiMeIQx), 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and benzo(a)pyrene (B(a)P)] and heme iron are associated with lung cancer. Participants' diet was assessed prospectively using a 124-item food frequency questionnaire and an additional meat-cooking module. Dietary data were used in conjunction with a database to estimate intake of MeIQx, DiMeIQx, PhIP, B(a)P and heme iron. After up to 8 years of follow-up, 782 incident lung cancer cases were ascertained. Lung cancer risk was not associated with the consumption of either red (men: HR(Q₅ vs. Q₁) = 1.11, 95% CI = 0.79-1.56, P(trend) = 0.42; women: HR(Q₅ vs. Q₁) = 1.30, 95% CI = 0.87-1.95, P(trend) = 0.65) or processed meat (men: HR(Q₅ vs. Q₁1) = 1.12, 95% CI = 0.83-1.53, P(trend) = 0.22; women: HR(Q₅ vs. Q₁) = 0.98, 95% CI = 0.68-1.41, P(trend) = 0.32) in multivariable models. High-temperature cooking methods, level of meat doneness, meat mutagens and heme iron had no effect on lung cancer risk. In this population, we found no association between meat type, cooking method, doneness level or intake of specific meat mutagens or heme iron and lung cancer risk.

Joint effects of dietary trace metals and DNA repair capacity in lung cancer risk

In a large case-control study, we previously reported that dietary intakes of zinc (Zn) and copper (Cu), but not selenium (Se), were inversely associated with lung cancer risk. Because Zn, Cu, Se, iron (Fe), and calcium (Ca) are important for maintaining DNA stability, we examined their associations with DNA repair capacity (DRC) measured by the lymphocyte host-cell reactivation assay in 1,139 cases and 1,210 of the controls. Dietary intake was reported in a food frequency questionnaire. In multivariate analyses, compared to those with high dietary Cu + proficient DRC, the odds ratio (95% confidence interval) [OR (95% CI)] for lung cancer for low Cu + suboptimal DRC was 2.54 (1.97-3.27). Similar results were observed for men and women. These effects were more pronounced in older and lean subjects, those with late-stage disease, and those with a family history of cancer in first-degree relatives. Compared to subjects with high Zn + proficient DRC, the OR for lung cancer for low Zn + suboptimal DRC was 1.82 (95% CI, 1.41-2.34), with pronounced effects in men, current smokers, subjects with longer duration of smoking, those with late-stage disease, or those with a family history of cancer. An OR of 1.94 (95% CI, 1.51-2.48) was observed for low Fe + suboptimal DRC compared with high Fe + proficient DRC, and pronounced effects appeared in older, lean subjects, those with longer duration of smoking, are heavier smokers, those with a late-stage disease, and those with a family history of cancer. No significant joint associations were seen for Se or Ca and DRC. Our joint associations between Cu-DRC, Zn-DRC and Fe-DRC and lung cancer risk require confirmation in prospective studies.

Iron intake, oxidative stress-related genes (MnSOD and MPO) and prostate cancer risk in CARET cohort

Iron overload may increase prostate cancer risk through stimulation of oxidative stress, and endogenous pro- and antioxidant capabilities, i.e. manganese superoxide dismutase (MnSOD) and myeloperoxidase (MPO), may modify these associations. We investigated this hypothesis in the Carotene and Retinol Efficacy Trial cohort in a nested case-control study. Although there was no association between iron intake and risk overall, there was a suggestion of increased risk of clinically aggressive prostate cancer with higher iron intake [odds ratio (OR) = 1.4, 95% confidence interval (CI) = 0.9-2.0]. Associations were most notable for men with aggressive prostate cancer who were below the median consumption of total fruits and vegetables (OR = 1.8, 95% CI = 1.1-3.2). Associations between MPO -463 G to A genotype (rs2333227) and prostate cancer risk were only noted among men with aggressive cancer, with more than a 2-fold risk reduction among men with AA genotypes (OR = 0.4, 95% CI = 0.2-1.0); MnSOD was not associated with risk overall, but the MnSOD T to C (Val-9Ala, rs4880) polymorphism modified associations between risk of clinically aggressive prostate cancer and dietary iron intake (P for interaction = 0.02). Among aggressive cancer cases with the TT genotype, higher iron intake level was associated with >2-fold increase in risk (OR = 2.3, 95% CI = 1.0-4.9), whereas there was no association among men with CC genotypes (OR = 0.9, 95% CI = 0.4-2.3). Although interactions were not significant, there were similar patterns for MPO genotype, iron intake and risk. These findings suggest that higher iron intake may be associated with risk of clinically aggressive prostate cancer, and that endogenous antioxidant capabilities may modify these associations.

Dietary Iron and Heme Iron Intake and Risk of Breast Cancer: A Prospective Cohort Study

Recent studies suggest that elevated body iron levels may contribute to breast carcinogenesis; however, epidemiologic evidence is lacking. We used data from a large cohort study of Canadian women to assess breast cancer in association with total iron and heme iron intake. Among 49,654 women ages 40 to 59 followed for an average of 16.4 years, we identified 2,545 incident breast cancer cases. Data from a food frequency questionnaire administered at baseline were used to calculate total dietary iron and heme iron intake. Using Cox proportional hazards models, we found no association of iron or heme iron intake with risk of breast cancer overall, in women consuming 30+ g of alcohol per day, or in women who had ever used hormone replacement therapy. The present study offers no support for an association of iron or heme iron intake with breast cancer risk or for a modification by iron of the effect of alcohol or estrogen. However, further cohort studies with repeated measurement of iron intake are warranted.

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.