Previous epidemiological studies suggested that vitamin E could aid in lowering the risk of cervical cancer, but the data presented by different reports was considered ‘controversial’.
As such, researchers from Wenzhou Medical University in China conducted a meta-analysis to explore the association between vitamin E and cervical neoplasia, which included both cervical cancer and premalignant growths.
They assessed 15 observational studies involving a total of 10,069 subjects (3,741 cases and 6,328 controls).
Higher intake, lower risk
The researchers observed that a “higher category of vitamin E could reduce the cervical neoplasia risk”, while in their sub-group analysis, both vitamin E intake and levels of vitamin E in the blood were inversely associated with the risk of cervical neoplasm.
The same relationship was observed among different populations and types of cervical neoplasia, and the meta-analysis added that “meta-regression showed that none of the including covariates were significantly related to the outcomes”.
A different association
However, despite lower serum levels of vitamin E having been associated with increased cancer risk, several studies had different results.
One of the studies observed that the plasma concentrations of α-tocopherol between healthy controls and patients with cervical intraepithelial neoplasia were similar.
The analysis attributed this to the fact that the “mechanisms of vitamin E on cancer risk were still not well understood”.
It stated that vitamin E’s main mechanism could possibly be anti-carcinogenic and anti-oxidative, or could improve immunity, and prohibit cancer cell growth by restricting the phosphoinositide 3-kinase pathway.
Limited by bias and heterogeneity
The researchers also acknowledged the limitations of the analysis.
The vitamin E dosage and formulations varied across the different studies, which were almost exclusively case-control studies and as such, could have resulted in selection bias.
Additionally, “misclassification and imprecise measurement of vitamin E intake should be of concern in observational researches”, and there was also significant heterogeneity in the studies included.
This might have been due to the differing study variables, such as different ethnicities, regions, testing methods and time periods.
The meta-analysis concluded that while “sufficient supplementation of vitamin E might reduce the risk of cervical neoplasia…more randomised controlled trials and cohort studies with high quality were required to further validate this inverse relationship”.
Source: PLOS One
“Effect of vitamin E supplementation on uterine cervical neoplasm: A meta-analysis of case-control studies”
Authors: Xiaoli Hu, et al.