This food and dietary supplement may reduce prostate cancer spread, improve survival in breast cancer, and lower the risk of several cancers.

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This section does not replicate the other information on this topic but provides additional details or context most relevant to professionals.

Modes of action: lignans as phytoestrogens

Flaxseed is the richest dietary source of lignan precursors. Of several types of lignans produced in the colon from precursors, two are phytoestrogens. These plant estrogens are considered to have weak estrogenic activity—they bind to estrogen receptors and change the expression of genes that respond to estrogen. Although they can bind to estrogen receptors, their ability to influence estrogen responsive genes is weaker than endogenous estrogen. In fact, lignan phytoestrogens may actually “block or antagonize the effects of estrogen in some tissues.”1Drake VJ. Lignans. Linus Pauling Institute. Oregon State University. March 2021. Viewed October 12, 2021.  

Scientists are interested in the anti-estrogenic effect of lignans in reproductive tissue, as it may help reduce the risk of hormone-related cancers (breast, uterine, ovarian, and prostate). While concerns have been raised about lignan exposure and potential impacts for people with hormone-sensitive cancers, a 2013 review of studies of flaxseed and breast cancer concluded that most studies have found no change in levels of endogenous estrogen, and those that did find changes found decreases in serum estrogen levels, suggesting reduced exposure to endogenous estrogen over time with intake of flaxseed.2Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92.

In addition, American Institute for Cancer Research (AICR) consultant Karen Collins, MS, RDN, CDN, FAND, advises: “The evidence now really supports looking at compounds like the lignans in flaxseed as SERMS (receptor modulators). I encourage people to stop using the term ‘phytoestrogen’, since this correctly refers to similarities in chemical structure, but is easily misunderstood to suggest a consistent pro-estrogen effect in the body.”3Collins K. Email communication with Laura Pole. November 16, 2018.

Preclinical evidence

Notable preclinical evidence is listed here; clinical evidence is in How can flaxseed help you? What the research says ›

Improving treatment outcomes

  • Greater apoptosis in adenocarcinoma cells with exposure to flaxseed orbitides (peptides)4Zou X, Li J, et al. Orbitides isolated from flaxseed induce apoptosis against SGC-7901 adenocarcinoma cells. International Journal of Food Sciences and Nutrition. 2020 Dec;71(8):929-939.
Gynecological cancer, including ovarian cancer 

Optimizing your body terrain

Blood sugar and insulin resistance

Managing side effects and promoting wellness: preclinical evidence

Radiotherapy damage

Reducing cancer risk

Helpful links for professionals

KNOW Oncology ›

A subscription is required; access is free of charge for members of the Society for Integrative Oncology.

Kajla P, Sharma A, Sood DR. Flaxseed-a potential functional food source. Journal of Food Science and Technology. 2015 Apr;52(4):1857-71.

Keep reading about flaxseed


Maria Williams

Research and Communications Consultant
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Maria Williams is a research and communications consultant who brings over 15 years’ experience in research, consumer education, and science communication to CancerChoices. She has worked primarily in public health and environmental health.

Maria Williams Research and Communications Consultant

Nancy Hepp, MS

Lead Researcher
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Ms. Hepp is a researcher and communicator who has been writing and editing educational content on varied health topics for more than 20 years. She serves as lead researcher and writer for CancerChoices and also served as the first program manager. Her graduate work in research and cognitive psychology, her master’s degree in instructional design, and her certificate in web design have all guided her in writing and presenting information for a wide variety of audiences and uses. Nancy’s service as faculty development coordinator in the Department of Family Medicine at Wright State University also provided experience in medical research, plus insights into medical education and medical care from the professional’s perspective.

Nancy Hepp, MS Lead Researcher


Laura Pole, MSN, RN, OCNS

Senior Clinical Consultant
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Laura Pole is senior clinical consultant for CancerChoices. Laura is an oncology clinical nurse specialist who has been providing integrative oncology clinical care, navigation, consultation, and education services for over 40 years. She is the co-creator and co-coordinator of the Integrative Oncology Navigation Training at Smith Center for Healing and the Arts in Washington, DC. Laura also manages the “Media Watch Cancer News That You Can Use” listserv for Smith Center/Commonweal. In her role as a palliative care educator and consultant, Laura has served as statewide Respecting Choices Faculty for the Virginia POST (Physician Orders for Scope of Treatment) Collaborative as well as provided statewide professional education on palliative and end-of-life care for the Virginia Association for Hospices and Palliative Care.

For CancerChoices, Laura curates content and research, networks with clinical and organizational partners, brings awareness and education of integrative oncology at professional and patient conferences and programs, and translates research into information relevant to the patient experience as well as clinical practice.

Laura sees her work with CancerChoices as a perfect alignment of all her passions, knowledge and skills in integrative oncology care. She is honored to serve you.

Laura Pole, MSN, RN, OCNS Senior Clinical Consultant

Last update: December 11, 2023

Last full literature review: September 2021

CancerChoices provides information about integrative in cancer care, a patient-centered approach combining the best of conventional care, self care and evidence-informed complementary care in an integrated plan cancer care. We review complementaryin cancer care, complementary care involves the use of therapies intended to enhance or add to standard conventional treatments; examples include supplements, mind-body approaches such as yoga or psychosocial therapy, and acupuncture therapies and self-care lifestyle actions and behaviors that may impact cancer outcomes; examples include eating health-promoting foods, limiting alcohol, increasing physical activity, and managing stress practices to help patients and professionals explore and integrate the best combination of conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy and complementary therapies and practices for each person.

Our staff have no financial conflicts of interest to declare. We receive no funds from any manufacturers or retailers gaining financial profit by promoting or discouraging therapies mentioned on this site.

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