RATIONALE: Estrogen can cause the growth of breast cancer cells. Studying samples of blood and urine in the laboratory from participants receiving freeze-dried table grape powder may help doctors understand the effect of this drug on blood estrogen levels. PURPOSE: This clinical trial is studying the effect of freeze-dried table grape powder on blood estrogen levels in postmenopausal women.
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DISEASE CHARACTERISTICS: * Participant in the Mayo Mammography Health Study * Has consented to provide baseline mammogram for digitization PATIENT CHARACTERISTICS: * ECOG performance status 0-1 * Female * Postmenopausal (defined as women who have had both ovaries removed or no menstrual period for at least 12 consecutive months) * Able to give informed consent and complete food records alone or with assistance * Willing to provide research blood and urine samples * Must be a non-smoker * Willing to maintain current weight * No history of breast ductal carcinoma in situ or any other cancer, except basal cell or squamous cell skin cancer or lobular carcinoma in situ * No history of allergic or other adverse reaction to grapes * No history of diabetes or glucose intolerance PRIOR CONCURRENT THERAPY: * No concurrent hormone therapy, including estradiol, estrone, or progestins