Oxidative stress is suspected to intervene in certain chronic diseases. Muc
h research has been devoted to the relationship between vitamin E, a major
lipid-soluble antioxidant, and certain widespread diseases. Experimental an
d epidemiological proof supports a protective effect of vitamin E in a numb
er of pathological processes such as coronary heart disease, cancer, catara
ct, diabetes mellitus, and Alzheimer disease. Randomized clinical trials ha
ve not confirmed a beneficial effect of vitamin E supplementation on the pr
ogression of these diseases. Certain methodological biases could however ha
ve affected these studies, explaining conflicting results. These biases inc
lude inaccuracy or vitamin E intake estimates and changes in eating habits
during the course of the survey. An insufficient supplementation period usi
ng an insufficient dose and inclusion of aged and high-risk patients are th
e main limitations of the reported clinical trials.
Large scale randomized clinical trials including healthy and low-risk subje
cts, along with prolonged administration of high-dose natural vitamin E, as
sociated with synergetic compounds, and testing on morphological or biologi
cal features, will allow a better understanding of the relationship between
vitamin E and chronic diseases.