Insight into Potential Impact of Serum Levels of β-Carotenoid on Lung and Colorectal Cancer Mortality: An 18-Year Retrospective National Cohort Study

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Beta-carotenoids, precursors of vitamin A, are important antioxidants within the physiological system in humans and animals. Lung cancer is the leading cause of cancer-related deaths in the US, followed by colorectal cancer. Sufficient evidence linking influence of β-carotene on lung and colorectal cancer mortality are lacking; thus, our objective was to examine the influence of serum β-carotene levels on lung and colorectal cancer mortality in an 18-yr follow-up study. A retrospective cohort study was conducted with 14,358 adults who participated in phase II of the National Health and Nutrition Examination Survey III (1991-1994) (NHANES III). This served as baseline and was correlated with the National Death Index database for an 18-yr (1988-2006) follow up study. Cox Proportional Hazards Regression Model was used to estimate Hazard Ratios (HRs) for lung and colorectal cancer mortality among individuals with high, medium or low levels of β-carotenoids. Unadjusted HR for lung cancer HRL and colorectal cancer HRC deaths associated with low serum levels of beta carotenoids were 2.21 (95% CI=1.56-3.13) and 1.60 (95% CI=0.78-3.28), respectively, and 1.00 (ref). Upon adjustment for multiple risk factors (e.g., age, sex and cigarette smoking), HRL and HRC were 1.58 (95% CI=1.10-2.28) and 1.53 (95% CI=0.73-3.19), respectively and 1.00 (ref). HR for lung cancer deaths linked to serum levels of β-carotenoid, using 3-level categorization and controlling for fruits and vegetables, were 1.90 (95% CI=1.26-2.86) and 1.02 (95% CI=0.74-1.41) for low and medium vs. high levels, respectively. Findings also showed 2.11 (95% CI=0.93-4.78) and 1.83 (95%CI=1.07-3.16), respectively, for colorectal cancer mortality using a similar comparison. Results indicate that there were significant association between serum levels of beta carotenoids and lung/colorectal cancer mortality. The mechanism by which this phenomenon occurs is a subject for further studies.


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