Q: A few of my patients have asked me about flaxseed to prevent hot flushes while they are on tamoxifen. Should I recommend it?
Flaxseed has multiple mechanisms of action, and may act as a phytoestrogen. It may antagonize tamoxifen or even stimulate breast cancer growth. Explain to your patients that this is a controversial area, with limited and conflicting evidence for both efficacy and safety. Because the safety is unknown, the current BC Cancer Agency (BCCA) recommendation is cautious. We advise against the use of any phytoestrogen supplements during chemotherapy or radiation treatments. This recommendation applies to flaxseed, as well as other supplements such as black cohosh, dong quai, evening primrose, red clover, soy and others. However, food sources of phytoestrogens generally do not need to be restricted during treatment. Recent evidence suggests that Flaxseed is safe when used in moderation (such as 1-2 Tablespoons ground flaxseed per day) and soy foods are safe for breast when eaten in amounts similar to typical Asian diets (two servings per day). Direct patients to our handout Natural Health Products and Breast Cancer for more information. Use our Tamoxifen Patient Handout to help start a discussion on non-pharmacologic management of hot flushes.
Revised May 5, 2014