Lower serum vitamin E tied to higher colorectal cancer risk
Lower serum vitamin E concentrations are associated with elevated risks of colorectal cancer (CRC), according to a new meta-analysis.
Pooled data from 11 studies over 10 publications (n=6,431; 520 cases; 5,981 controls) showed that mean serum vitamin E concentrations was significantly lower in CRC patients than in controls with a weighted mean difference (WMD) of -2.994 µmol/L (95 percent CI, -4.395 to -1.591 µmol/L; p<0.001).
Significant heterogeneity was detected in the results (p<0.001); subgroup analyses were performed to identify the source.
Subgroup analysis by ethnicity showed that lower serum vitamin E levels were associated with higher CRC risks (WMD, -1.82; -3.00 to -0.65 µmol/L; p=0.002). This trend was not significant in Asians (WMD, 11.01; -22.09 to 0.09 µmol/L; p=0.052).
Moreover, the association between vitamin E levels and CRC risk was significant only when cases were compared with hospital-based controls (WMD, -3.43; -6.27 to -0.59 µmol/L; p=0.018) but not with population-based controls.
The meta-analysis included case-control studies that assessed the relationship between CRC risk and levels of serum vitamin E. The databases of PubMed, Embase and China National Knowledge Infrastructure were accessed.
Among the information retrieved were cohort characteristics, vitamin E levels and disease incidence. The Newcastle-Ottawa scale (NOS) was used to assess methodological quality of the selected studies.
Of the 10 eligible publications, and out of a maximum of nine points in the NOS, three studies scored eight, six scored seven and two scored six.
Further prospective cohort studies are required to more accurately determine the effects of low vitamin E levels on CRC risk, according to researchers.