Flaxseed During Breast Cancer Treatment

Last Modified: September 14, 2008


Dear OncoLink "Ask The Experts,"
I have been treated for the last 8 months for an invasive breast cancer (mastectomy and chemo). I am now on Tamoxifen and have been having quite the time with hot flashes. I have been reading about using flaxseed in your diet to help combat the hot flashes. I have found articles that are both pro and con on using flaxseed when you have breast cancer. What is your opinion? Thanks for your time!


Kathleen Gallagher, RD, LDN, Oncology Dietitian at the Abramson Cancer Center of the University of Pennsylvania, responds:

In a study done by the Mayo Clinic on post-menopausal women without breast cancer or estrogen therapy, flaxseeds were shown to reduce the number of hot flashes but did not get rid of them altogether. The participants had 4 Tablespoons (TBSP) of ground flaxseed per day and showed a 50% decrease in the number of hot flashes and in their severity as well.

Flaxseeds eaten at these higher amounts can have a laxative effect. A serving size of 1-2 Tbsp would be more tolerable and appropriate, especially during Tamoxifen therapy. The whole flaxseeds must be ground to bring out the nutrients because our bodies cannot digest the tough outer shell. When eating the whole food as opposed to a flaxseed oil supplement, you also get the added benefit of fiber. Ground flaxseed can be mixed into yogurt, cereals, and baked products such as muffins and breads.

The Mayo Clinic is still researching the effect of flaxseeds for hot flashes in women taking Tamoxifen and no results are available at this time. The studies are being done to test if the weak form of estrogen contained in flaxseeds, called lignans, impedes the action of the Tamoxifen by blocking receptor sites on the cancer cells. So for the time being, it may be best to err on the side of caution and stick to the more tolerable serving size of 1-2 Tbsp of ground flaxseed a day.


Pruthi, S., et al. Pilot evaluation of flaxseed for the management of hot flashes. J Soc Integr Oncol. 2007 Summer; 5(3):106-12.


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