Using literature in 11 relevant studies — two from Asia, five from Europe and four from the US — published between 1955 and April 2015, the authors discovered an inversely proportional relationship between vitamin E intake and the risk of developing lung cancer.
The analysis stated: “Vitamin E is a powerful liquid-soluble antioxidant and might be effective in reducing the risk of lung cancer by reducing oxidative stress”, adding that apart from lung cancer, the risk of developing bladder, gastric and prostate cancer can also be reduced by increased vitamin E intake.
The “linear relationship between dietary vitamin E intake and the risk of lung cancer” is characterised by a 5% risk decrease for every 2 mg/d increase in dietary vitamin E consumption.
This inverse relationship was attributed to a number of reasons, such as vitamin E’s “anti-inflammatory properties that protect cells and DNA from reactive radicals”, its ability to “reduce nitrite and inhibit the production of carcinogenic nitrosoamides and nitrosoamines”, and its potential to “prevent carcinogenesis by down-regulating the nuclear factor (NF)-κB signalling pathway to inhibit cell proliferation and angiogenesis, including apoptosis”.
However, subgroup analysis based on geographic location showed that while “dietary vitamin E intake was inversely associated with the risk of lung cancer for the American and European populations”, it was only “marginally significantly associated with the risk of lung cancer for the Asian population”.
While insufficient sample size was a possible reason for this observation (only two of the 11 studies were from Asia), the discrepancy could also be due to varying dietary sources of vitamin E among different ethnic groups and cultures.
For the Western population, the “major dietary sources of vitamin E are soybeans and soybean oil”, which are high in γ-tocopherol. The Asian population, on the other hand, gets most of its vitamin E from leafy greens and eggs, which contain “high quantities of α-tocopherol”.
The former might possess “unique mechanistic characteristics” when compared with the latter, such as anti-inflammatory properties that facilitate the “inhibition of cy-clooxygenase activity, which might make an important contribution to the effect of vitamin E on reduced lung cancer risk," noted the researchers.
Besides this observation, however, the analysis maintained that dietary vitamin E intake is “significantly associated with a reduced risk of lung cancer”, and concluded that the “findings need to be confirmed further by larger prospective studies”.
Source: Asia Pacific Journal of Clinical Nutrition
“Association of dietary vitamin E intake with risk of lung cancer: a dose-response meta-analysis”
Authors: Yong-Jian Zhu, et al.