Monday, February 2, 2009

Higher vitamin E levels in smokers linked with reduced pancreatic cancer risk

The February, 2009 issue of the American Journal of Clinical Nutrition reported the finding of researchers at the National Cancer Institute, the University of Michigan, and the National Public Health Institute in Helsinki, Finland, of an association between higher concentrations of alpha-tocopherol (the most biologically active and plentiful form of vitamin E in most human tissues) and a lower risk of pancreatic cancer in smokers. Smoking, diabetes and obesity are among the known risk factors for this deadly form of cancer.

Rachel Z. Stolzenberg-Solomon and colleagues evaluated data from 29,092 men who participated in the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study, a double-blind placebo-controlled trial which sought to determine the effect of alpha-tocopherol and beta-carotene supplementation on the prevention of cancers in smokers between 1985 and 1988. Over up to 19.4 years of follow-up, 318 cases of pancreatic cancer were diagnosed.

For participants whose serum alpha-tocopherol levels at the beginning of the study were among the top 20 percent of participants, the risk of developing pancreatic cancer was 48 percent lower than those whose levels were in the lowest fifth. Among the 27,111 subjects for whom dietary questionnaire responses were available, for those who had the highest polyunsaturated fat intake at over 9.9 grams per day there was an even greater reduction in pancreatic cancer risk observed in participants with the highest vitamin E levels, a finding that could be explained by vitamin E’s ability to counteract polyunsaturated fats’ pro-oxidant effect.

While no protective association was observed between dietary intake of vitamin E and pancreatic cancer risk in this study, the authors note that dietary intake as estimated by questionnaire responses is not precise, and that serum vitamin concentrates may be more biologically meaningful due to their reflection of the combined effects of intake, absorption and utilization as well as depletion caused by oxidative stress. “Our results support the hypothesis that higher concentrations of serum alpha-tocopherol may protect against pancreatic carcinogenesis in smokers,” they conclude. “Further research is needed to evaluate our findings in other populations, particularly relative to exposure factors that influence endogenous oxidative stress.”

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