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Observational epidemiological surveys (WG 3) page 37
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1-2-6 Vitamin E (Tables 22-25)
Comments on tables 22-25
For stomach cancer the results are inconsistent, with the Chinese case-control study based on
dietary intake showing a strong reduction in risk and the European prospective study based on
plasma levels (but only 28 cases) showing a non-significant increase in risk. This result raise
the attention on the different behaviours in food intake among countries and on the difficult
interpretation of studies with different designs. The recent studies tend to support a possible
role of vitamin E in risk reduction of lung cancer, only in association with vitamin C and/or
carotenoids (Berry et al., 1999). For colon cancer, the case-control studies showed a tendency
towards a reduction of risk, which was non significant in the prospective study. In the
Canadian study the intake appeared more protective than the supplements. For breast cancer,
there was a non significant increase of risk in prospective studies conducted in Northern
countries but a tendency to a risk reduction in the case-control studies from the Mediterranean
countries and Uruguay. This effect decreased or became NS with mutual adjustment for other
antioxidants. A decreased risk was also found in the Italian study for high levels of seed oil
intake, which is the main source of vitamin E. Therefore, it is difficult to attribute a specific
effect to one of these nutrients. Thus, the results from Mediteranean studies were intriguing
but underlined the difficulty of inferring the effect of a nutrient from food intake, and even
from food habits as a whole. Two case-control studys of the 3 recently reported on dietary
vitamin E intake and the prospective studies in Switzerland (Eicholzer et al., 1996) and USA
(the Physicians Health Study, Gann et al., 1999) based on plasma concentration indicated an
effect on prostate cancer incidence, to be mentioned in spite of the small number of cases and
the wide CI, in Switzerland and the borderline significant results in the USA and in the
Uruguayan case-control study, because of the results of ATBC study (See below).