However Professor Jarmo Virtamo, the principal investigator of the Alpha-Tocopherol, Beta-Carotene Cancer Prevention (ATBC) trial, warned that further research is needed to clarify whether taking supplements can offer the same level of protection.
Original findings from the ATBC study, which included nearly 30,000 Finnish men, showed that daily supplements of alpha-tocopherol (50mg) reduced the risk of prostate cancer by 32 per cent.
In a new analysis, Professor Virtamo, based at the National Public Health Institute in Helsinki, Finland, and colleagues from the National Cancer Institute in Bethesda, Maryland and the Fred Hutchinson Cancer Research Center looked at the impact of circulating vitamin E levels on 100 individuals with prostate cancer and 200 cancer-free controls participating in the trial.
Men with the highest levels of alpha-tocopherol in their blood at baseline were 51 per cent less likely to develop prostate cancer than those with the lowest levels, they reported in yesteday's issue of the Journal of the National Cancer Institute (vol 97, no 5, pp396-399).
Similarly, men with the highest levels of gamma-tocopherol were 43 per cent less likely to develop the disease compared with men with the lowest levels.
"Further analyses indicated that the association of high serum tocopherols with low prostate cancer risk was stronger in the alpha-tocopherol-supplemented group than in those not receiving alpha-tocopherol," note the authors.
Vitamin E is thought to fight cancer through its antioxidant activity, which combats the oxidative stress involved in cancer development. It also has other non-antioxidant properties, such as enhancement of the immune response, which may also play a role in the benefits seen.
Professor Virtamo said that the new findings were not surprising based on the earlier results but that they offered support for the original findings.
"There are actually very few studies looking at the association of vitamins with prostate cancer. More often they have focused on lung cancer," he told NutraIngredients.com.
But he added: "Unfortunately this study only shows an association between reduced cancer but it doesn't show that if you start giving people supplements this will protect them against prostate cancer."
In addition, the levels of vitamin E levels seen among the participants could be considered low and did not necessarily demonstrate support for gamma-tocopherol.
Gamma-tocopherol, found naturally in walnuts, sesame seeds and corn, was found to hold back the proliferation of lab-cultured human prostate and lung cancer cells in research at Purdue University published in December.
Previous research by the same team found that gamma-tocopherol inhibits inflammation, which had already been implicated in cancer development.
But Professor Virtamo cautioned: "Since trials have shown no benefit with alpha-tocopherol, the research world has started to look at new nutrients, such as gamma-tocopherol. But you have to remember that the intake of gamma-tocopherol in Finland is very low."
The highest tertile of alpha-tocopherol levels in the study were 15.78mg and the highest tertile of gamma-tocopherol was 1.08mg.
"The benefit seen here probably reflects that those with higher gamma-tocopherol levels also have a more healthy lifestyle in general," he said.
"Also the difference in tertiles is very small. We need other studies comparing levels with bigger differences."
"It is always possible that a different form of vitamin E has different effects or that they have different effects on different organs. But we need more data," concluded Professor Virtamo.
Vitamin E researchers are eagerly awaiting results form the Select trial, looking at whether high dose (400mg) alpha-tocopherol supplements can protect against prostate cancer. If these results fail to confirm the ATBC findings, new research will have to look at the role of dosages on cancer protection.