NEW YORK (Reuters Health) – A comparison of the effects of various forms of dietary vitamin E on lung cancer risk shows a strong independent relationship only for alpha-tocopherol, researchers report.
The investigators, headed by Dr. Somdat Mahabir at The University of Texas M.D. Anderson Cancer Center in Houston, analyzed the associations between four dietary tocopherols (alpha, beta, gamma, and delta) and lung cancer risk, in a study of 1,088 patients with lung cancer and 1,414 healthy control subjects.
In the September issue of the International Journal of Cancer, the authors explain that dietary data were collected using a modified version of a 135-item questionnaire developed by the National Cancer Institute and administered by trained interviewers. The authors note that only individuals with “reasonable” daily caloric intakes were included.
The researchers constructed two different models for analyzing risk. In the first model, “When dietary intakes of alpha-, beta-, gamma-, and delta-tocopherol were analyzed separately, increasing intakes of alpha-, beta-, and gamma-tocopherol but not delta-tocopherol, were associated with a lower risk of lung cancer,” the authors report.
Specifically, with increasing quartiles of intake, the odds ratios for lung cancer were 0.63, 0.58, and 0.39 with alpha-tocopherol; 0.79, 0.59, and 0.56 with beta-tocopherol; and 0.84, 0.76, and 0.56 with gamma-tocopherol.
“In model 2, for which the association of a specific tocopherol was adjusted for all the other tocopherols, only the alpha-tocopherol association remained significant,” the investigators write. The odds ratios with increasing quartiles of intake were 0.66, 0.64, and 0.47.
They add that in model 1, the protective effect of alpha-tocopherol did not depend on subjects’ smoking status. In model 2, however, the inverse relationship remained significant only among current or former smokers, with “a more pronounced risk reduction seen in current smokers.”
“To the best of our knowledge, this is the first study to compare dietary intakes of the different forms of tocopherols and lung cancer risk,” the researchers write.
They acknowledge that estimates of dietary tocopherol intake are very difficult to assess and that their case-control study had multiple limitations. Still, they conclude, “Our data should be useful in stimulating additional epidemiologic and basic science research in the relationship of different forms of vitamin E and cancer.”
Int J Cancer 2008;123:1173-1180.