Flaxseed Lignans
Authors
Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher
Read more Ms. Pole is an oncology clinical nurse specialist who has been providing integrative oncology clinical care, navigation, consultation and education services for more than 30 years. View profile.
Nancy Hepp, MS, BCCT Project Manager
Read more Ms. Hepp is a science researcher and communicator who has been writing and editing educational content on varied health topics for more than 20 years. View profile.
Last updated November 23, 2020.
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Key Points
- Before using this therapy, consult your oncology team about interactions with other treatments and therapies. Also make sure this therapy is safe for use with any other medical conditions you may have.
- Lignans are natural plant compounds concentrated in flaxseed but also found in several other plant foods.
- Clinical evidence suggests links with decreased mortality and overall survival, with additional anticancer effects for breast cancer.
- A metabolite of flaxseed is associated with reduced cancer risk, especially for breast, prostate, colon, gastric and lung cancers.
- Whole flaxseed, but not flaxseed oil and lignan extract, improved glycemic control and insulin levels and sensitivity when used 12 weeks or more.
- Used in several integrative programs and protocols and in traditional medical systems (Ayurveda and traditional Chinese medicine).
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Flaxseed contains many components beneficial to health: lignans, fiber, magnesium, thiamin and an omega-3 fatty acid. In this summary, we focus on the lignans, natural plant compounds concentrated in flaxseed but also found in several other plant foods.
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.
Treating the Cancer
Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action
Clinical Evidence
Enterolactone, a metabolite of flaxseed, is associated with decreased mortality rate and improved overall survival particularly in breast, prostate, colon, gastric and lung cancer.
Breast Cancer
- Anticancer effects among newly diagnosed breast cancer patients, including reduced tumor growth
- Increased cell death (apoptosis) and other tumor biological markers among women with postmenopausal breast cancer.
- Lower mortality among breast cancer patients in observational evidence
- Lower overall mortality in postmenopausal breast cancer patients who have high estimated enterolignan—a metabolite of flaxseed and other lignans—and dietary fiber, which is also abundant in flaxseed
Prostate Cancer
- In a randomized controlled trial looking at the effects of low-fat and/or flaxseed-supplemented diets on prostate cancer biology and biomarkers, flaxseed consumption was safe and associated with reduced proliferation rates, although no effect was seen on rate of cell death (apoptosis), PSA or IGF-I.
- A single study in 2004 suggested that men eating the highest amounts flaxseed oil had higher risk for prostate cancer progression, leading to speculation that dietary intake of α-linolenic acid (ALA)—found mainly in flaxseed and other foods—increases the risk of prostate cancer. However, authors of a subsequent meta-analysis “failed to confirm an association between dietary α-linolenic acid intake and prostate cancer risk.”
Lab and Animal Evidence
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- Flaxseed inhibited MCF-7 breast tumor growth in a dose-dependent manner and enhanced the inhibitory effect of tamoxifen in ovariectomized athymic mice. In other studies, flaxseed did not stimulate MCF-7 breast tumor growth and regressed tumor size when combined with tamoxifen.
- Both whole flaxseed and defatted flaxmeal (the lignan component) promoted cell death (apoptosis) in ovarian tumors in hens.
- Flax oil reduced cervical tumor volume and weight in mice.
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 data
- Some evidence shows flaxseed reduced the incidence or frequency of hot flashes in women not taking estrogen therapy and postmenopausal women with or without breast cancer. However, a review concluded that flaxseed was ineffective in reducing hot flashes in postmenopausal women, either with or without breast cancer.
Lab and Animal Evidence
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- Reduced radiation therapy-induced lung damage in cell and animal studies
Reducing Risk
Reducing the risk of developing cancer or the risk of recurrence
Clinical Evidence
- Flaxseed lignans are reported to reduce the risk of primary breast cancer in observational clinical data. In a survey of women's consumption of phytoestrogen-containing foods, lignan intake was associated with reduced breast cancer risk among pre-menopausal women, with stronger associations among overweight women (body mass index over 25).
- Flaxseed consumption is associated with reduced risk or occurrence of colorectal cancer.
- Enterolactone, a metabolite of flaxseed, is associated with reduced risk, particularly in breast, prostate, colon, gastric and lung cancer.
Optimizing Your Terrain
A 2018 review concluded that whole flaxseed, but not flaxseed oil and lignan extract, improved glycemic control and insulin levels and insulin sensitivity indexes when used 12 weeks or more.
Cautions
Do not heat flaxseed oil, as the heat will damage the oil and form dangerous compounds. Heating flaxseed also removes many beneficial micronutrients.
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.
Read more
The article then concludes: "Current evidence suggests that flax may be associated with decreased risk of breast cancer. Flax demonstrates antiproliferative effects in breast tissue of women at risk of breast cancer and may protect against primary breast cancer. Mortality risk may also be reduced among those living with breast cancer."
A 2014 review concluded that "more clinical trials are needed but current overall evidence indicates that FS [flaxseed] and its components are effective in the risk reduction and treatment of breast cancer and safe for consumption by breast cancer patients." The authors also report that "ten percent FS and equivalent lignans do not interfere with but rather increase the effectiveness of tamoxifen (80 mg/day) while the 4 percent FS oil increases trastuzumab/Herceptin (2.5 mg/kg) effectiveness."
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."
About Herbs also lists some adverse reactions in their summary, Flaxseed.
Livestrong provides an article on the dangers of taking high doses of flaxseed lignans such as high-lignan flaxseed oil:
- Weight gain
- An additive effect on blood thinners
- Interactions with medications for managing blood sugar
- Exclusive use as a source of omega-3s may lead to insufficient levels of DHA and EPA.
For more details, see the Livestrong summary, The Dangers of High Lignan Flax Seed Oil.
Access
Both dietary flaxseed and flaxseed extract are widely available.
Dosing
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:
- Alschuler LN, Gazella KA. The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing. Berkeley, California: Celestial Arts. 2010.
- Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Care. New York: Bantam Dell. 2009.
- McKinney N. Naturopathic Oncology, 3rd Edition. Victoria, BC, Canada: Liaison Press. 2016.
- Moss Reports (purchase required): Select from the list of cancers down the left side of the page for a report describing uses of conventional, complementary, alternative and integrative therapies related to that cancer. Ralph Moss is among the most knowledgeable and balanced researchers of integrative cancer therapies. The cost of his Moss Reports is not negligible, but many patients find them of considerable value. Moss is also available for consultations.
- Natural Medicines Database (requires purchase)
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.”
Integrative Programs, Protocols and Medical Systems
- Programs and protocols
- Traditional systems
- Deng GE, Frenkel M et al. Evidence-based clinical practice guidelines for integrative oncology: complementary therapies and botanicals. Journal of the Society for Integrative Oncology. 2009 Summer;7(3):85-120.
- Mali AV, Padhye SB, Anant S, Hegde MV, Kadam SS. Anticancer and antimetastatic potential of enterolactone: clinical, preclinical and mechanistic perspectives. European Journal of Pharmacology. 2019 Jun 5;852:107-124.
- Mason JK, Thompson LU. Flaxseed and its lignan and oil components: can they play a role in reducing the risk of and improving the treatment of breast cancer? Applied Physiology, Nutrition, and Metabolism. 2014 Jun;39(6):663-78.
- Thompson LU, Chen JM, Li T, Strasser-Weippl K, Goss PE. Dietary flaxseed alters tumor biological markers in postmenopausal breast cancer. Clinical Cancer Research. 2005 May 15;11(10):3828-35.
- Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92.
- Buck K, Zaineddin AK et al. Estimated enterolignans, lignan-rich foods, and fibre in relation to survival after postmenopausal breast cancer. British Journal of Cancer. 2011 Oct 11;105(8):1151-7.
- Demark-Wahnefried W, Polascik TJ et al. Flaxseed supplementation (not dietary fat restriction) reduces prostate cancer proliferation rates in men presurgery. Cancer Epidemiology, Biomarkers & Prevention. 2008 Dec;17(12):3577-87; Hackshaw-McGeagh LE, Perry RE et al. A systematic review of dietary, nutritional, and physical activity interventions for the prevention of prostate cancer progression and mortality. Cancer Causes and Control. 2015 Nov;26(11):1521-50.
- Leitzmann MF, Stampfer MJ et al. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. American Journal of Clinical Nutrition. 2004;80(1):204-16.
- Carleton AJ, Sievenpiper JL, de Souza R, McKeown-Eyssen G, Jenkins DJ. Case–control and prospective studies of dietary α-linolenic acid intake and prostate cancer risk: a meta-analysis. British Medical Journal Open. 2013 May 14;3(5). pii: e002280.
- Chen J, Power KA, Mann J, Cheng A, Thompson LU. Flaxseed alone or in combination with tamoxifen inhibits MCF-7 breast tumor growth in ovariectomized athymic mice with high circulating levels of estrogen. Experimental Biology and Medicine (Maywood). 2007 Sep;232(8):1071-80.
- Chen J, Power KA, Mann J, Cheng A, Thompson LU. Dietary flaxseed interaction with tamoxifen induced tumor regression in athymic mice with MCF-7 xenografts by downregulating the expression of estrogen related gene products and signal transduction pathways. Nutrition and Cancer. 2007;58(2):162-70; Chen J, Saggar JK, Corey P, Thompson LU. Flaxseed cotyledon fraction reduces tumour growth and sensitises tamoxifen treatment of human breast cancer xenograft (MCF-7) in athymic mice. British Journal of Nutrition. 2011 Feb;105(3):339-47; Saggar JK, Chen J, Corey P, Thompson LU. Dietary flaxseed lignan or oil combined with tamoxifen treatment affects MCF-7 tumor growth through estrogen receptor- and growth factor-signaling pathways. Molecular Nutrition & Food Research. 2010 Mar;54(3):415-25.
- Dikshit A, Hales K, Hales DB. Whole flaxseed diet alters estrogen metabolism to promote 2-methoxtestradiol-induced apoptosis in hen ovarian cancer. Journal of Nutritional Biochemistry. 2017 Apr;42:117-125.
- Deshpande R, Raina P et al. Flax seed oil reduced tumor growth, modulated immune responses and decreased HPV E6 and E7 oncoprotein expression in a murine model of ectopic cervical cancer. Prostaglandins & Other Lipid Mediators. 2019 Apr 5. pii: S1098-8823(18)30109-6.
- Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92.
- Pruthi S, Thompson SL et al. Pilot evaluation of flaxseed for the management of hot flashes. Journal of the Society for Integrative Oncology. 2007 Summer;5(3):106-12.
- Pruthi S, Qin R et al. A phase III, randomized, placebo-controlled, double-blind trial of flaxseed for the treatment of hot flashes: North Central Cancer Treatment Group N08C7. Menopause. 2012 Jan;19(1):48-53.
- Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92; Dew TP, Williamson G. Controlled flax interventions for the improvement of menopausal symptoms and postmenopausal bone health: a systematic review. Menopause. 2013 Nov;20(11):1207-15.
- Velalopoulou A, Tyagi S, Pietrofesa RA, Arguiri E, Christofidou-Solomidou M. The flaxseed-derived lignan phenolic secoisolariciresinol diglucoside (SDG) protects non-malignant lung cells from radiation damage. International Journal of Molecular Sciences. 2015 Dec 22;17(1). pii: E7.
- Pietrofesa R, Turowski J et al. Radiation mitigating properties of the lignan component in flaxseed. BMC Cancer. 2013 Apr 4;13:179.
- Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92.
- Cotterchio M, Boucher BA, Kreiger N, Mills CA, Thompson LU. Dietary phytoestrogen intake—lignans and isoflavones—and breast cancer risk (Canada). Cancer Causes & Control. 2008 Apr;19(3):259-72.
- DeLuca JAA, Garcia-Villatoro EL, Allred CD. Flaxseed bioactive compounds and colorectal cancer prevention. Current Oncology Reports. 2018 Jun 5;20(8):59.
- Mali AV, Padhye SB, Anant S, Hegde MV, Kadam SS. Anticancer and antimetastatic potential of enterolactone: clinical, preclinical and mechanistic perspectives. European Journal of Pharmacology. 2019 Jun 5;852:107-124.
- Mohammadi-Sartang M, Sohrabi Z, Barati-Boldaji R, Raeisi-Dehkordi H, Mazloom Z.Flaxseed supplementation on glucose control and insulin sensitivity: a systematic review and meta-analysis of 25 randomized, placebo-controlled trials. Nutrition Reviews. 2018 Feb 1;76(2):125-139.
- Lemole G, Mehta P, McKee D. After Cancer Care: The Definitive Self-Care Guide to Getting and Staying Well for Patients with Cancer. New York, New York: Rodale, Inc. 2015.
- Goyal A, Sharma V, Upadhyay N, Gill S, Sihag M. Flax and flaxseed oil: an ancient medicine & modern functional food. Journal of Food Science and Technology. 2014 Sep;51(9):1633-53.
- Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92.
- Flower G, Fritz H et al. Flax and breast cancer: a systematic review. Integrative Cancer Therapies. 2014 May;13(3):181-92.
- Mason JK, Thompson LU.Flaxseed and its lignan and oil components: can they play a role in reducing the risk of and improving the treatment of breast cancer? Applied Physiology, Nutrition, and Metabolism. 2014 Jun;39(6):663-78.
- Collins K. Email communication with Laura Pole. November 16, 2018.
- Stein N. The dangers of high lignan flax seed oil. Livestrong.com. Viewed May 17, 2019.
- Collins K. HealthTalk: Flaxseed and Breast Cancer. Our Blog.American Institute for Cancer Research.June 6, 2017. Viewed November 20, 2018.
- Alschuler LN, Gazella KA. The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing. Berkeley, California: Celestial Arts. 2010; Alschuler LN, Gazella KA. The Definitive Guide to Thriving after Cancer: A Five-Step Integrative Plan to Reduce the Risk of Recurrence and Build Lifelong Health. Berkeley, California: Ten Speed Press. 2013.
- Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Treatment. New York: Bantam Dell. 2009.
- Lemole G, Mehta P, McKee D. After Cancer Care: The Definitive Self-Care Guide to Getting and Staying Well for Patients with Cancer. New York, New York: Rodale, Inc. 2015.
- MacDonald B. The Breast Cancer Companion: A Complementary Care Manual: Third Edition. 2016.
- McKinney N. Naturopathic Oncology, 3rd Edition. Victoria, BC, Canada: Liaison Press. 2016.
View All References
More Information
- Ottawa Integrative Cancer Centre Evidence-Based Monographs, Flax for Breast Cancer:
- About Herbs: Flaxseed
- Livestrong: The Dangers of High Lignan Flax Oil
- American Institute for Cancer Research: Flaxseed and Cancer Survivorship
- De Silva SF, Alcorn J. Flaxseed lignans as important dietary polyphenols for cancer prevention and treatment: chemistry, pharmacokinetics, and molecular targets. Pharmaceuticals (Basel). 2019 May 5;12(2). pii: E68.
- Gurdev Parmar and Tina Kaczor: Textbook of Naturopathic Oncology
- Dawn Lemanne and Victoria Maizes: Advising Women Undergoing Treatment for Breast Cancer
- LifeExtension Nutritional Support: Integrative Interventions for Breast Cancer
- Donald I. Abrams, MD, and Andrew T. Weil, MD: Integrative Oncology, 2nd Edition
- Lise Alschuler, ND, FABNO, and Karolyn Gazella: The Definitive Guide to Cancer, 3rd Edition
- Keith I. Block, MD: Life over Cancer: The Block Center Program for Integrative Cancer Treatment
- Memorial Sloan Kettering Cancer Center: About Herbs, Botanicals and Other Products
- Therapeutic Research Center: Natural Medicines Database
- American Botanical Council: HerbMed
- Lone Star Medical Group: Natural Alternative Treatments
- ConsumerLab.com
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