Vitamin E Intake and Risk of Prostate Cancer: A Meta-Analysis

Abstract

Vitamin E is a group of antioxidative tocopherols and tocotrienols that play a potential role in chemoprevention. Studies investigating the association between vitamin E and prostate cancer risk have been conflicting. We identified observational and interventional studies examining the association between vitamin E intake and prostate cancer risk from PubMed, EMBASE and the Cochrane Library. A random-effects model was used to perform a meta-analysis and estimate relative risks (RRs) and the corresponding 95% confidence intervals (CIs) of prostate cancer risk according to vitamin E intake. Subgroup analyses were conducted by study design, sample size, study population characteristics, geographical region, and dose of vitamin E intake. The association between dietary (RR = 0.97; 95% CI = 0.92–1.02) and supplemental (RR = 0.99; 95% CI = 0.94–1.04) vitamin E intake on prostate cancer risk was non-significant. In subgroup analyses, supplemental vitamin E was significantly associated with reduced prostate cancer risk in studies in Europe (RR = 0.81, 95% CI = 0.69–0.97). Overall, this meta-analysis demonstrates little evidence for a beneficial effect of vitamin E intake on prostate cancer risk but suggests that there may be some conditions in which supplements could confer a protective effect on prostate cancer risk.

Pathophysiological-Based Nutritional Interventions in Cirrhotic Patients with Sarcopenic Obesity: A State-of-the-Art Narrative Review

“…As cirrhotic subjects were excluded from this study, causing a lack further evidence in this specific subset of patients, current guidelines do not recommend vitamin E supplementation to cirrhotic patients with obesity, even when dysmetabolic liver disease is present [177]. This caution is justified by the fact that vitamin E toxicity can cause major bleeding events, whereas the possible association between vitamin E supplementation and an increased risk of prostate cancer has not been confirmed by a recent metanalysis [227]. Few data are available to evaluate the effects of antioxidant supplementation in sarcopenia, with overall inconsistent evidence [228].…”

Antioxidant and Anti-Tumor Effects of Dietary Vitamins A, C, and E

“…Studies investigating the application of vitamin E as a cancer-fighting supplement in vivo have prioritized utilizing the δ- and γ-tocopherol forms—likely due to recent findings suggesting that α-tocopherol is not as effective as these other tocopherols as a preventative agent and antioxidant [ 127 , 128 , 129 , 130 , 131 , 132 ]. One such experiment investigated the ability of a γ-tocopherol-rich mixture of tocopherols (γ-TmT; 57% γ-tocopherol, 24% δ-tocopherol, 13% α-tocopherol and 1.5% β-tocopherol) to block tumorigenesis in mice directly exposed to the carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) with or without the carcinogen benzo[ a ]pyrene (B[ a ]P).…”

“…Researchers in this study found no influence of γ-tocopherol in preventing prostate tumor growth when compared to the control population [ 137 ]. This apparent inability for vitamin E to impact tumorigenesis of prostate cancer in rats may be related to recent findings that suggest vitamin E supplementation does not improve the risk of developing prostate cancer and may in fact actually increase the risk of prostate cancer in humans via the aforementioned increase in cytochrome family activity [ 126 , 129 , 130 , 138 , 139 ].…”

“…As with the pre-clinical studies, clinical data regarding the role of vitamin E in cancer prevention has shown mixed results ( Figure 5 ) [ 128 , 129 , 130 , 131 , 138 , 139 , 140 ]. One meta-analysis that primarily reviewed case-control and cohort studies regarding the usage of tocopherols as preventative agents against colorectal, lung, prostate, and breast cancer from 1986 to 2009 highlights many of the desired outcomes of vitamin E supplementation despite an equivalent presence of null findings [ 128 ].…”

“…Another meta-analysis investigated the associations between dietary and supplemental vitamin E intake and prostate cancer risk. From the 19 studies compiled, the estimated relative risk (RR) of developing prostate cancer from dietary levels of vitamin E intake was 0.97 (95% CI: 0.92–1.02); while, the estimated RR of developing prostate cancer from supplementary levels of vitamin E intake was 0.99 (95% CI: 0.94–1.04) [ 130 ]. Additionally, the estimated RR of developing prostate cancer from dietary and supplementary levels of vitamin E intake combined was 0.97 (95% CI: 0.85–1.08), supporting the conclusion that there was not an association between the cumulative intake of vitamin E and a change in prostate cancer risk [ 130 ].…”