Magnesium Oxide in Treating Postmenopausal Women With Hot Flashes and a History of Breast Cancer

DISEASE CHARACTERISTICS: * Women with a history of breast cancer (currently without malignant disease) * Bothersome hot flashes (defined by their occurrence ≥ 28 times per week and of sufficient severity to make the patient desire therapeutic intervention) * Presence of hot flashes for ≥ 30 days prior to study registration * Willingness to provide the biologic specimens as required by the protocol * Hormone receptor status not specified PATIENT CHARACTERISTICS: * Women who are postmenopausal as defined by absence of a period in the past 12 months or bilateral oophorectomy * Women with at least one ovary but without a uterus should be deemed postmenopausal by either age over 55 or a combination of estrogen within a postmenopausal range (per local lab) and FSH over 40 mIU/mL * No women of childbearing potential or who are premenopausal * Creatinine clearance \> 30 mL/min * Ability to complete questionnaire(s) by themselves or with assistance * ECOG performance status 0 or 1 * No history of allergic or other adverse reaction to magnesium * No diabetes * No patients with conditions that are implicated in decreased absorption of magnesium (e.g., Crohn disease, ETOH abuse) * No patients who have diarrhea where magnesium might make it worse (per provider discretion) PRIOR CONCURRENT THERAPY: * None of the following current (≤ 28 days prior to registration) or planned therapies (tamoxifen, raloxifene, or aromatase inhibitors are allowed, but the patient must have been on a constant dose for ≥ 28 days and must not be expected to stop the medication during the study period): * Antineoplastic chemotherapy (trastuzumab or lapatinib are allowed) * Androgens * Estrogens (any delivery route) * Progestational agents * No prior use of magnesium for hot flashes * No current or planned use of gabapentin (for any reasons) or antidepressants (for any reasons) or other agents for treating hot flashes (except stable dose of vitamin E is allowed as long as it was started \> 30 days prior to study registration and are to be continued through the study period; soy is allowed, if it is planned to be continued at the same dose during the study period) * No current use of magnesium for any indication (except one standard multiple vitamin dose is allowed per day) * Not taking diuretics, corticosteroids, bile acid sequestrants, and other prescription and over-the-counter medications that may affect magnesium levels * No current (≤ 7 days prior to registration) or planned use of other non-drug therapies for managing hot flashes, such as acupuncture or yoga (use of these therapies for other reasons is allowed)