Trial Information

Effects of Soy on Estrogens in Breast Fluid and Urine

OBJECTIVES:

- Examine the effects of two daily servings of soy on estrogen levels in nipple aspirate
fluid (NAF) and serum.

- Investigate cytologic patterns of epithelial breast cells obtained from NAF as a
measure of proliferation in relation to soy intake.

- Explore the effect of two daily servings of soy on cytochrome alterations of estrogen
metabolism as expressed in the formation of urinary 2-, 16α-, and 4-hydroxy estrogen
metabolites.

- Compare estrogen levels in NAF and serum measured at the same time during the luteal
phase.

OUTLINE: This is a multicenter study. Participants are randomized to 1 of 2 intervention
arms.

- Arm I: Participants partake in a high soy diet consisting of 2 daily soy servings
(approximately 50mg isoflavones). The choice of soy foods will include ½ cup of tofu, ¾
cup of soy milk, or ¼ cup of soy nuts. Replacement of currently consumed foods with soy
foods will be encouraged.

- Arm II: Participants will be asked to keep their soy intake below 3 servings per week.
The participants will also receive general nutrition counseling.

In both arms, intervention continues for 6 months. After 6 months, participants undergo a
1-month washout period and then cross-over to the other intervention arm.

Nipple aspirate fluid, urine, and blood samples are collected periodically to measure
laboratory endpoints.