Intake of Vitamins A, C, and E and Postmenopausal Breast Cancer: The Iowa Women's Health Study

Abstract

The association between dietary antioxidant vitamin intake and the risk of breast cancer was examined in a prospective study of 34,387 postmenopausal women in Iowa. Intakes of vitamins A, C, and E and of retinol and carotenoids were assessed in 1986 by mailed semiquantitative food frequency questionnaire. Through December 31, 1992, 879 incident breast cancer cases occurred in this cohort. There was little suggestion that breast cancer risk was associated with differences in intake of these vitamins. For example, from the lowest to highest total vitamin A intake categorized by quintiles, the age-adjusted relative risks of breast cancer were 1.0, 0.95, 1.17, 1.20, and 0.90 (p trend = 0.92). Similarly unremarkable relative risk patterns were seen for the intakes of vitamins C and E and of retinol and carotenoids. These findings were not altered after adjustment for breast cancer risk factors or in analyses confined to women who reported no supplemental vitamin intake. Exclusion of cases that occurred in the first 2 years of follow-up, under the assumption that women may have increased intake of these vitamins in response to preclinical symptoms of breast cancer, did not suggest an inverse association of these vitamins with the risk of breast cancer. Women who reported consuming at least 500 mg/day of supplemental vitamin C had a relative risk of breast cancer of 0.79 compared with women who did not take supplemental vitamin C, and women who reported consuming more than 10,000 IU/day of vitamin A had a corresponding relative risk of 0.73. However, these relative risks were not statistically significant. These results provide little evidence that intake of these vitamins is associated with breast cancer risk.

Vitamins A, C and E and the risk of breast cancer: results from a case-control study in Greece

“…Of ten case-control studies, seven (Graham et al, 1991;Lee et al, 1991;London et al, 1992;Holmberg et al, 1994;Yuan et al, 1995;Freudenheim et al, 1996;Negri et al, 1996) suggest an inverse association with vitamin E intake and three (Toniolo et al, 1989;Gerber et al, 1990;Richardson et al, 1991) report null or positive associations; the results are statistically significant in four (Graham et al, 1991;London et al, 1992;Freudenheim et al, 1996;Negri et al, 1996) of the studies reporting inverse associations. The results from cohort studies are decidedly weaker: of five studies (Graham et al, 1992;Hunter et al, 1993;Rohan et al, 1993;Kushi et al, 1996;Verhoeven et al, 1997), only one (Graham et al, 1992) reports a relative risk of less than 0.90, and this was not statistically significant.…”

“…A combined analysis of the data from eight case-control studies reported an odds ratio of 0.85 (P = 0.007) for the highest versus the lowest quintile of carotenoid intake (Howe et al, 1990). The results from six prospective studies are weaker; four (Paganini-Hill et al, 1987;Graham et al, 1992;Hunter et al, 1993;Rohan et al, 1993) observed inverse but non-significant associations, and two (Kushi et al, 1996;Verhoeven et al, 1997) found no evidence of an inverse association. Although the majority of the case-control and cohort studies did not evaluate specific carotenoids other than β-carotene, one recent case-control study presented results for several carotenoids.…”

“…Howe et al (1990), in a combined analysis of the data from nine case-control studies, reported an odds ratio of 0.69 (P<0.0001) for the highest quintile of vitamin C intake. Three prospective studies (Graham et al, 1992;Rohan et al, 1993;Verhoeven et al, 1997) observed relative risks of less than 0.90, although another two (Hunter et al, 1993;Kushi et al, 1996) did not. None of the results from prospective studies were statistically significant.…”

“…In a combined analysis of seven case-control studies, Howe et al (1990) report an odds ratio of 1.04 for the highest quintile of retinol intake. Of five prospective studies, two (Hunter et al, 1993;Rohan et al, 1993) report inverse associations with retinol intake, and three (Graham et al, 1992;Kushi et al, 1996;Verhoeven et al, 1997) report null or positive associations. The only statistically significant finding from a prospective study is reported by Hunter et al (1993), in which the relative risk for the highest quintile of intake is 0.80 (95% CI 0.68-0.95).…”

Micronutrient Vitamin Deficiencies and Cardiovascular Disease Risk: Advancing Current Understanding

“…Vitamin E supplementation provided a better reduction (40%) than the dietary vitamin E. The Health Professional Follow-Up Study of 40,000 US male professionals aged 40-75 years provided similar results [110]. Likewise, the Iowa Women's Health Study [149] found an inverse association between vitamin E and CVD. However, in the latter, the association was strongest in the group taking supplements than the diet group.…”