Source-specific effects of micronutrients in lung cancer prevention.
ABSTRACT The role of micronutrients in lung cancer prevention is controversial, as observational and experimental studies have generated contradicting results. These discrepancies between studies may be due to different effects of micronutrients depending on source (diet or supplements). The objective of this study was to evaluate the association between vitamin C, E, folate and beta-carotene and lung cancer risk while focusing on source-specific effects of dietary and supplemental intake. The association was evaluated in a cohort of 55,557 Danes who completed a food frequency questionnaire including information on consumption of vitamin C, E, folate and beta-carotene from diet and supplements. Incidence rate ratios of lung cancer were calculated using Cox proportional hazards models. During a median follow-up of 10.6 years, 721 incident lung cancer cases were diagnosed. We found a significant protective effect of dietary vitamin E intake and a significantly higher lung cancer risk with supplemental beta-carotene and dietary folate intake. All three micronutrients exhibited significant source-specific effects. The harmful effect of dietary folate is, however, most likely to be due to uncontrolled confounding. Our results indicate source-specific effects of vitamin E and beta-carotene in lung cancer prevention with a preventive effect of dietary vitamin E and a harmful effect of supplemental beta-carotene. Future studies on micronutrients and lung cancer should take source into account.
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ABSTRACT: Studies have reported inconsistent results regarding the existence of an association between folate intake and the risk of lung cancer. The purpose of this study was to summarize the evidence from prospective cohort studies regarding this relationship by using a dose-response meta-analytic approach. In September 2013, we performed electronic searches in PubMed, Embase, and the Cochrane Library to identify studies examining the effect of folate intake on the incidence of lung cancer. Only prospective cohort studies that reported the effect estimates about the incidence of lung cancer with 95% confidence intervals (CIs) for more than 2 categories of folate intake were included. Overall, we examined 9 cohort studies reporting the data of 566,921 individuals. High folate intake had little effect on the risk of lung cancer (risk ratio [RR], 0.92; 95% CI, 0.84-1.01; P = 0.076). Dose-response meta-analysis also suggested that a 100 µg/day increase in folate intake had no significant effect on the risk of lung cancer (RR, 0.99; 95% CI, 0.97-1.01; P = 0.318). Subgroup analysis suggested that the potential protective effect of low folate intake (100-299 µg/day) was more evident in women than men, while the opposite was true of high folate intake (>400 µg/day). Finally, subgroup analyses of a 100 µg/day increment in folate intake indicated that its potential protective effect was more evident in men than in women. Our study revealed that folate intake had little or no effect on the risk of lung cancer. Subgroup analyses indicated that an increased folate intake was associated with a reduced risk of lung cancer in men. Furthermore, low folate intake may be a protective factor for women, and high folate intake for men.PLoS ONE 01/2014; 9(4):e93465. · 3.53 Impact Factor
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ABSTRACT: PURPOSE: B vitamins and methionine have been postulated to have potential effects on carcinogenesis; however, findings from previous epidemiologic studies on B vitamins, methionine, and lung cancer risk are inconsistent. We investigated associations of dietary intakes of B vitamins (i.e., riboflavin, niacin, vitamin B6, folate, and vitamin B12) and methionine with lung cancer risk among female never smokers. METHODS: The Shanghai Women's Health Study, a population-based, prospective cohort study, included 74,941 women. During a median follow-up of 11.2 years, 428 incident lung cancer cases accrued among 71,267 women with no history of smoking or cancer at baseline. Baseline dietary intakes were derived from a validated, interviewer-administered food frequency questionnaire. Cancer incidence and vital status were ascertained through annual linkage to the Shanghai Cancer Registry and Shanghai Vital Statistics Registry databases and through biennial in-person follow-ups with participants. Adjusted hazard ratios (HR) and 95 % confidence intervals (CI) were calculated using Cox regression. RESULTS: Dietary riboflavin intake was inversely associated with lung cancer risk (HR = 0.62; 95 % CI = 0.43-0.89; p trend = 0.03 for the highest quartile compared with the lowest). A higher than median intake of methionine was associated with lower risk of lung cancer (HR = 0.78; 95 % CI = 0.60-0.99); however, there was no dose-response relation. Intakes of other B vitamins were not associated with lung cancer risk. CONCLUSIONS: Our study suggests that dietary riboflavin intake may be inversely associated with lung cancer risk among female never smokers, which warrants further investigation.Cancer Causes and Control 10/2012; · 3.20 Impact Factor
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ABSTRACT: Most epidemiological studies evaluating the association of fruit and vegetable intakes on lung cancer risk were conducted in North American and European countries. We investigated the association of intakes of fruits, vegetables, dietary vitamins A and C, and folate with lung cancer risk among 61,491 adult Chinese men who were recruited into the Shanghai Men's Health Study, a population-based, prospective cohort study. Baseline dietary intake was assessed through a validated food frequency questionnaire during in-home visits. Multivariate Cox regression was used to estimate hazard ratios (HR) and 95% confidence intervals (CI) of lung cancer risk associated with dietary intakes. During a median follow-up of 5.5 yr, 359 incident lung cancer cases accrued after the first year of follow-up and 68.8% of them were current smokers. Intakes of green leafy vegetables, β-carotene-rich vegetables, watermelon, vitamin A, and carotenoids were inversely associated with lung cancer risk; the corresponding HR (95% CI) comparing the highest with the lowest quartiles were 0.72 (0.53-0.98), 0.69 (0.51-0.94), 0.65 (0.47-0.90), 0.63 (0.44-0.88), and 0.64 (0.46-0.88). Intake of all fruits and vegetables combined was marginally associated with lower risk. Our study suggests that the consumption of carotenoid-rich vegetables is inversely associated with lung cancer risk.Nutrition and Cancer 01/2013; 65(1):51-61. · 2.70 Impact Factor