Higher dietary vitamin E intake can reduce lung cancer risk: Chinese meta-analysis

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”​.

Diet differences

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​

https://doi.org/10.6133/apjcn.032016.04​

“Association of dietary vitamin E intake with risk of lung cancer: a dose-response meta-analysis”​

Authors: Yong-Jian Zhu, et al.​

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