The Effect of Soy Protein on Post- Breast Cancer Surgery Pain

Inclusion Criteria: * Women diagnosed with breast cancer and scheduled for elective breast cancer surgery (excluding breast biopsy) with axillary lymph node dissection (total and/or sentinel node excision). * Women who are 21 years or older. Exclusion Criteria: * History of significant heart, gastro-intestinal, liver or kidney disease. * Use of the anticoagulant, warfarin or Coumadin. * Malabsorption of any kind. * Diagnosed lactase deficiency. * Known allergy to any of the tested dietary products. * Basic daily consumption of soy protein in quantities exceeding 10 g/day. * Women who are strict vegetarians (i.e. no animal derived dietary sources). * The use of the following narcotics or adjuvant pharmacotherapy: opioids, anticonvulsants, antidepressants and steroids (except antidepressant use specifically for depression). * Tumour size (if known) \> 3cm(i.e. size before pre-operative chemotherapy, if administered). * Locally advanced breast cancer. * Inflammatory breast cancer. * Paget's disease of the breast with palpable mass. * Suspected metastasis. * Suspected micrometastasis. * Previous breast surgery of any kind (except needle biopsy). * The need for bilateral breast surgery. * The existence of other known cancer, including metastasis, either in the other breast or elsewhere. * Previous or current endocrine cancer therapy (e.g. selective estrogen receptor modulators, aromatase inhibitor). * Body mass index (BMI) \> 35.