Abstract
BackgroundStudies 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.Methodology and Principal FindingsIn 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.Conclusion/SignificanceOur 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.
Highlights
Lung cancer is the leading cause of cancer-related deaths worldwide for both men and women, and approximately 1.5 million new cases are diagnosed each year [1,2]
For the past few decades, studies have shown that fruits and vegetables are associated with a lower incidence of lung cancer [3]; supplemental vitamins are widely used for chemoprevention of lung cancer because dietary habits are difficult to change [4]
Any prospective study that examined the relationship between folate intake and incidence of lung cancer was eligible for inclusion in our study, and no restrictions were placed on language or publication status
Summary
Lung cancer is the leading cause of cancer-related deaths worldwide for both men and women, and approximately 1.5 million new cases are diagnosed each year [1,2]. For the past few decades, studies have shown that fruits and vegetables are associated with a lower incidence of lung cancer [3]; supplemental vitamins are widely used for chemoprevention of lung cancer because dietary habits are difficult to change [4]. Dietary intake of fruits and vegetables has been closely related to the risk of lung cancer. Among the supplemental vitamin subtypes, folate shows promise for inhibiting carcinogenesis and reducing the risk of lung cancer at a certain dose. Data on the effect of folate intake on the subsequent incidence of lung cancer are limited and inconclusive. 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
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