PLASMA TOCOPHEROL AND PREVALENCE OF COLORECTAL ADENOMAS IN A MULTIETHNIC POPULATION

Although vitamin E can block mutagenesis and cell transformation in vi tro and can reduce the number of chemically induced colonic adenomas i n mice, previous clinical trials have found no protective effect of vi tamin E supplements against colorectal adenomas, and epidemiological s tudies have found only weak protective effects of dietary or plasma al pha-tocopherol against colorectal cancer, We previously examined first diagnosis of colorectal adenomas in a sigmoidoscopy screening populat ion and failed to find a protective effect of dietary vitamin E. Becau se measurements of dietary intake may not be a good proxy of vitamin E status, we assayed plasma alpha- and gamma-tocopherol concentration f or 332 subjects with colorectal adenomas and 363 control subjects from this previous sigmoidoscopy-based study, Increasing alpha-tocopherol and decreasing gamma-tocopherol levels were associated with decreased occurence of large (greater than or equal to 1 cm) but not of small (< 1 cm) adenomas; however, after adjustment for potential confounding va riables, these trends were not statistically significant, A strong tre nd (P = 0.02) was observed by using the alpha-tocopherol:gamma-tocophe rol ratio, which may be a more sensitive indicator of alpha-tocopherol intake, Subjects in the highest versus lowest quintile of alpha-tocop herol:gamma-tocopherol ratio had an odds ratio of 0.36 (95% confidence interval, 0.14-0.95) for large adenomas, The finding that a high alph a-tocopherol:gamma-tocopherol ratio is associated with decreased occur rence of large, but not of small, colorectal adenomas is consistent wi th previous findings that alpha-tocopherol may be protective against c olon cancer, A high plasma alpha-toeopherol:gamma-tocopherol ratio may be a better predictor of decreased cancer risk than high plasma alpha -tocopherol alone.