{"entity":{"id":"flaxseed-supplements","kind":"technology","name":"Flaxseed and flaxseed lignans","aka":["Linseed","Linum usitatissimum","Secoisolariciresinol diglucoside"],"tldr":"Ground flaxseed is a high-fibre food that can help constipation. As a cancer treatment it has only small studies of tumour growth markers in prostate and breast cancer, and in a trial it did not reduce hot flushes in women with or without breast cancer. It has weak oestrogen-like effects, so people with hormone-sensitive breast cancer should ask their team before taking supplement doses.","summary":"Flaxseed contains omega-3 fatty acids and lignans that act as weak phytoestrogens. Memorial Sloan Kettering's About Herbs entry reports that flaxseed may lower tumour biomarkers and proliferation in small studies of men with prostate cancer and women with breast cancer, but it was ineffective at reducing hot flushes in postmenopausal women with or without breast cancer, a flaxseed extract did not prevent oral infection after head and neck radiotherapy, a lignan supplement did not reduce proliferation in breast tissue of premenopausal women at increased risk, and poor tolerability prevented any conclusion in a study of radiation lung protection. Laboratory and animal studies show inhibition of breast and prostate cancer growth and reduced chemotherapy cardiotoxicity. Outside cancer it has evidence for constipation, blood pressure and some metabolic measures. MSK advises people with oestrogen receptor-positive breast cancer to consult their physicians because of its phytoestrogen content. Side effects are mostly digestive; case reports include anaphylaxis and gynaecomastia with flaxseed oil.","status":"phase-2","asOf":"2026-11-04","links":[{"label":"MSK About Herbs: Flaxseed (page last updated 27 July 2026)","url":"https://www.mskcc.org/cancer-care/integrative-medicine/herbs/flaxseed"}],"tags":["complementary","supportive-care","evidence:insufficient"],"related":["red-clover-isoflavones","quercetin-supplements"],"cancers":["breast-hr-positive","prostate"],"sections":["supportive-care","nutrition-lifestyle","hormonal"],"technologies":["integrative-oncology","dietary-supplements-treatment-interactions","soy-breast-cancer","acupuncture-hot-flushes"],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":["b-toxicity-qol"],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"principle":"Lignans are converted by gut bacteria to enterolactone and enterodiol, weak oestrogen-receptor ligands that also alter oestrogen metabolism; the seed's fibre acts as a bulk laxative.","strengths":["Useful fibre for constipation","Small biomarker studies in prostate and breast cancer"],"limitations":["Did not reduce hot flushes in a trial","No outcome trials in cancer","Phytoestrogen caution in oestrogen receptor-positive breast cancer"]},"route":"/technologies/flaxseed-supplements/","neighbours":{"technology":[{"id":"acupuncture-hot-flushes","kind":"technology","name":"Acupuncture for hot flushes on endocrine therapy","route":"/technologies/acupuncture-hot-flushes/"},{"id":"dietary-supplements-treatment-interactions","kind":"technology","name":"Dietary supplements during cancer treatment: interactions and harms","route":"/technologies/dietary-supplements-treatment-interactions/"},{"id":"integrative-oncology","kind":"technology","name":"Evidence-based integrative oncology","route":"/technologies/integrative-oncology/"},{"id":"pomegranate-extract","kind":"technology","name":"Pomegranate juice and extract","route":"/technologies/pomegranate-extract/"},{"id":"quercetin-supplements","kind":"technology","name":"Quercetin supplements","route":"/technologies/quercetin-supplements/"},{"id":"red-clover-isoflavones","kind":"technology","name":"Red clover isoflavones","route":"/technologies/red-clover-isoflavones/"},{"id":"soy-breast-cancer","kind":"technology","name":"Soy foods and breast cancer","route":"/technologies/soy-breast-cancer/"}],"cancer":[{"id":"breast-hr-positive","kind":"cancer","name":"HR-positive / HER2-negative breast cancer","route":"/cancers/breast-hr-positive/"},{"id":"prostate","kind":"cancer","name":"Prostate cancer","route":"/cancers/prostate/"}],"section":[{"id":"nutrition-lifestyle","kind":"section","name":"Diet, Exercise & Lifestyle","route":"/fronts/nutrition-lifestyle/"},{"id":"hormonal","kind":"section","name":"Hormonal Therapy","route":"/fronts/hormonal/"},{"id":"supportive-care","kind":"section","name":"Supportive Care & Survivorship","route":"/fronts/supportive-care/"}],"bottleneck":[{"id":"b-toxicity-qol","kind":"bottleneck","name":"Toxicity and quality of life are undervalued","route":"/bottlenecks/b-toxicity-qol/"}]}}