RESUMO
BACKGROUND: Some epidemiological studies have suggested that vitamin E intake reduces the risk of pancreatic cancer; however, this conclusion has not been supported by all the published studies. We conducted a meta-analysis to assess the relationship between vitamin E intake and the risk of pancreatic cancer by combining the results from published articles. MATERIAL/METHODS: We searched the published studies that reported the relationship between vitamin E intake and pancreatic cancer risk using the PubMed, Web of Science, and Embase databases through December 31st, 2014. Based on a fixed-effects or random-effects model, the RR and 95% CI were used to assess the combined risk. RESULTS: In total, 10 observational studies (6 case-control studies and 4 cohort studies) were included. The overall RR (95% CI) of pancreatic cancer for the highest vs. the lowest level of vitamin E intake was 0.81 (0.73, 0.89). We found little evidence of heterogeneity (I2=19.8%, P=0.255). In the subgroup analyses, we found an inverse association between vitamin E intake and pancreatic cancer risk both in the case-control and cohort studies. Additionally, this inverse association was not modified by different populations. CONCLUSIONS: In our meta-analysis, there was an inverse association between vitamin E intake and the risk of pancreatic cancer. A high level of vitamin E might be a protective factor for populations at risk for pancreatic cancer.
Assuntos
Anticarcinógenos , Antioxidantes/fisiologia , Estudos Observacionais como Assunto/estatística & dados numéricos , Neoplasias Pancreáticas/epidemiologia , Vitamina E/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticarcinógenos/administração & dosagem , Antioxidantes/administração & dosagem , Ásia/epidemiologia , Estudos de Casos e Controles , Estudos de Coortes , Suplementos Nutricionais , Europa (Continente)/epidemiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Neoplasias Pancreáticas/prevenção & controle , Projetos de Pesquisa , Risco , Fatores de Risco , Tamanho da Amostra , Estados Unidos/epidemiologia , Vitamina E/administração & dosagem , Adulto JovemRESUMO
We demonstrate the importance of London dispersion forces in defining the adsorption capacity within expanded graphite, a simple model of the more complex experimental geometries of activated carbon, using a combination of the non-local correlation functional of Dion et al paired with a recent exchange functional of Cooper (vdW-DF(C09x)) and a classical continuum model. Our results indicate that longer ranged interactions due to dispersion forces increase the volume over which molecules interact with a porous medium. This significantly enhances the adsorption density within a material, and explains recent experimental work showing that the densification of H(2) in carbon nanopores is sensitive to the pore size. Remarkably, our slit pore geometries give adsorption densities of up to 3 wt% at 298 K and 20 MPa which correlates well with experimental values for 9 Å pores-a value that could not be predicted using local density approximation (LDA) calculations. In its entirety, this work presents a powerful approach for assessing molecular uptake in porous media and may have serious impacts on efforts to optimize the properties of these materials.
