Date of Award

2014

Document Type

Open Access Thesis

Department

Epidemiology and Biostatistics

Sub-Department

Epidemiology

First Advisor

Susan Steck

Abstract

Background: It is well-established that many risk factors for breast cancer are related to estrogen or reproductive factors. Two estrogen metabolites of particular interest are 2-hydroxyestrone (2-OHE) and 16α-hydroxyestrone (16α-OHE) which are often reported together as a ratio of 2:16α-hydroxyestrone (2:16α –OHE). It has been demonstrated in several studies that postmenopausal women who are at a higher risk of breast cancer tend to have increased levels of 16α-OHE or decreased levels of 2-OHE levels in the body. Recent studies have shown that the phytochemical indole-3-carbinol (I3C), found in Brassica vegetables, impacts the conversion of 2-OHE, known as “good estrogen”, by inducing the enzyme CYP1A1; however, research on the effects of Brassica vegetable consumption on the 2:16α-OHE ratio in randomized clinical settings is still sparse. The objective of this study is to examine whether an increase in Brassica vegetable consumption would alter the 2:16α-OHE estrogen metabolite ratio among postmenopausal women, by increasing 2-OHE and decreasing 16α-OHE.

Methods: Postmenopausal African American and European American women who resided in the standard metropolitan statistical area (SMSA) around the Columbia, South Carolina area were recruited between April 2002 and September 2003 for a nine-week dietary intervention. The women were randomized into one of two arms, intervention group or non-intervention (control group), during the first clinic. The women randomized to the intervention group were offered nine classes that were led by trained study dietitians over a three-week dietary intervention geared at increasing the consumption of Brassica vegetables daily at home; whereas, those in the control group were asked to maintain their usual dietary habits for the duration of the study period. The study population that was used for analysis consisted of 64 women who attended both clinic visits with complete urine, dietary data, and baseline information.

Results: Compared to baseline levels, Brassica vegetable intake significantly increased in the intervention group by 6-fold when compared to the control group during the intervention; whereas, post intervention, Brassica intake only increased in the intervention about 3.5-fold when compared to the control group. At post intervention, there were no statistically significant differences between the intervention and control groups in 2-OHE (10.6 ng/ml vs. 8.7 ng/ml, respectively, p=0.4), 16α-OHE (9.6 ng/ml vs. 8.6 ng/ml, respectively, p=0.6) and 2:16α-OHE (1.3 ng/ml vs. 1.3 ng/ml, respectively, p=0.7) levels. The effect of the intervention was determined separately for high and low Brassica vegetable consumers at baseline, stratified by race, and stratified by breast cancer survivorship status but these did not appear to modify the effect of the intervention on 2-OHE, 16α-OHE, or 2:16α-OHE levels after adjustment for covariates. Conslusion: These findings suggest that Brassica vegetables do not play a role in the modification of 2-OHE and 2:16α-OHE metabolite levels among postmenopausal women in a short, three-week intervention. These findings highlight the need for future research to further understand the biological mechanism between estrogen metabolites and Brassica vegetable consumption. Future research is needed to determine whether a larger increase in Brassica vegetables could affect estrogen metabolites and to examine whether genes may modify the effect of Brassica vegetables on estrogen metabolites.

Rights

© 2014, Kendrea Knight

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