Flaxseed Lignans

BCCT plans to write a summary on flaxseed lignans. While our summary is in development, you can visit these sites:

Clinical Practice Guidelines

According to the Society for Integrative Oncology’s 2009 clinical practice guidelines, there is insufficient evidence to rate the effectiveness of flaxseed lignans for helping quality of life or hot flashes.1

Treating the Cancer

Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action

Effects of flaxseed:

  • Anticancer effects among newly diagnosed breast cancer patients, including reduced tumor growth2
  • Lower mortality among breast cancer patients in observational evidence3
  • Promoted cell death (apoptosis) in ovarian tumors in hens, using both whole flaxseed and defatted flaxmeal (the lignan component)4

Managing Side Effects and Promoting Wellness

Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being

Clinical Evidence

  • Better mental health among breast cancer patients in observational data5
  • Ineffective in reducing hot flashes in postmenopausal women, either with or without breast cancer6

    Lab and Animal Evidence

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Reducing Risk

Reducing the risk of developing cancer or the risk of recurrence

Flaxseed lignans are reported to reduce the risk of some cancers, including primary breast cancer in observational clinical data.9


Do not heat flaxseed oil, as the heat will damage the oil and form dangerous compounds.10

About Herbs cautions that because flaxseed has phytoestrogenic effects, patients with estrogen receptor positive breast cancer should use flaxseed lignan with caution. However, their summary on flaxseed did not cite any studies to back up this caution. A 2013 review of studies of flaxseed and breast cancer findings:

In vitro, flaxseed metabolites such as ENL [enterolactone] have been shown to interact with estrogen receptors behaving as weak estrogen agonists. While this action may be of concern to women with breast cancer, flaxseed administration appears to have no significant effect on endogenous estrogen levels in the majority of human trials, either in women with cancer or in healthy women. Conversely, studies that do report significant changes cite decreases in serum estrogen levels, suggesting reduced exposure to endogenous estrogen over time with flaxseed consumption. Fabian et al assessed the effect of 50 mg of SDG [a flax lignon precursor] on breast density over a 12-month period. Mammographic assessment found no significant change from baseline in breast tissue density following this intervention. These results lend further support to the notion that flaxseed does not appear to have a significant estrogenic effect in vivo.11

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BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians, as contraindications, interactions and side effects must be evaluated.

Human studies are limited but suggest that if anything, including one to four tablespoons of flaxseed per day might reduce breast cancer risk, especially in post-menopausal women.

AICR consultant Karen Collins, MS, RDN, CDN, FAND

Dosage recommendations are available from these sources:

A blog post from the American Institute for Cancer Research advises: "Human studies are limited but suggest that if anything, including one to four tablespoons of flaxseed per day might reduce breast cancer risk, especially in post-menopausal women.”15

Integrative Programs, Protocols and Medical Systems

For more information about programs and protocols, see our Integrative Programs and Protocols page.
  • Programs and protocols
    • Elimination and detoxification
    • Immune enhancement
    • Reversing insulin resistance
    • Breast cancer
    • Colorectal cancer
    • Prostate cancer
    • Whole foods diet
    • Peripheral neuropathy
    • Chemo brain

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