Brassica vegetable consumption shifts estrogen metabolism in healthy postmenopausal women

Previous studies suggest that the estrogen metabolite 16 alpha-hydroxyestro ne acts as a breast tumor promoter. The alternative product of estrogen met abolism, 2-hydroxyestrone, does not exhibit estrogenic properties in breast tissue, and lower values of the ratio 2-hydroxyestrone:16 alpha-hydroxyest rone (2:16) in urine may be an endocrine biomarker for greater breast cance r risk. Vegetables of the Brassica genus, such as broccoli, contain a phyto chemical, which may shift estrogen metabolism and increase the 2:16 ratio. Adding 500 g/day of broccoli to a standard diet shifts 2:16 values upward i n humans; however, it is unknown as to whether healthy women are able to co nsume a sufficient quantity of Brassica to affect breast cancer risk throug h this mechanism. In this study, 34 healthy postmenopausal women participat ed in an intensive intervention designed to facilitate the addition of Bras sica to the daily diet. The diet was measured by repeated 24-h recall, and estrogen metabolites were measured by enzyme immunoassay in 24-h urine samp les. In a crude analysis, there was a nonsignificant increase in the urinar y 2:16 ratio associated with greater Brassica consumption. With adjustment for other dietary parameters, Brassica vegetable consumption was associated with a statistically significant increase in 2:16 values, such that for ea ch 10g/day increase in Brassica consumption, there was an increase in the 2 :16 ratio of 0.08 (95% confidence interval, 0.02-0.15), To the extent that the 2:16 ratio, as measured in urine, is associated with breast cancer risk , future research should consider Brassica vegetable consumption as a poten tially effective and acceptable dietary strategy to prevent breast cancer.