Flaxseed (Linum usitatissimum)

November 15, 2011

Flax, an annual plant believed to have originated in Egypt, is cultivated around internationally and is among the world’s oldest crops.

ALSO KNOWN AS: Flax, linseed, lint bells, linum.

BACKGROUND: Flax, an annual plant believed to have originated in Egypt, is cultivated around internationally and is among the world’s oldest crops. The seeds and oil are used in
traditional medicine to treat coughs, colds, acne, burns, constipation, and urinary tract infections, and to control menopausal symptoms.

Flaxseed is rich in omega-3 fatty acids that afford protection against heart disease and other health problems. It also contains phytoestrogens called lignans, which appear to have anticancer properties.

Despite lack of conclusive clinical evidence, flaxseed is promoted as an anticancer agent. It is available in the form of whole seeds, oil, capsule, powder, and as linseed cakes in many grocery and health food stores.

TAKE HOME POINTS

Traditionally used as a laxative because of its high fiber content, flaxseed is also a rich source of omega-3 fatty acids and lignans.
In vitro studies indicate anticancer effects of flaxseed; human data are limited.
Because flaxseed contains phytoestrogenic lignans, patients with estrogen receptor– positive breast cancer should use caution before taking flaxseed supplements.

For additional information, visit the Memorial Sloan-Kettering Cancer Center Integrative Medicine Service website, "About Herbs," at

http://www.mskcc.org/AboutHerbs

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RESEARCH: Studies in mice suggest that flaxseed inhibits the growth and metastasis of human breast cancer,[1] prostate cancer,[2] and melanoma[3]; it also reduces radiation therapy-induced lung damage and improves survival in mice.[4]

Flaxseed was shown to demonstrate chemo-[5] and renoprotective effects in patients with lupus nephritis.[6] It may improve mild menopausal symptoms[7] and benefit women with polycystic ovarian syndrome by reducing androgen levels.[8] A moderate reduction of estrogens and androgens, which may afford protection against breast cancer, was also seen in postmenopausal women.[9]

Flaxseed reduced tumor biomarkers in men with prostate cancer[10] and in patients with breast cancer,[11] but a flaxseed extract was ineffective in preventing oral infection after radiation treatment for head and neck cancer.[12] Further research is needed to determine the anticancer potential of flaxseed.

ADVERSE REACTIONS: Common reactions include increased bowel movements,[13] constipation, and flatulence.[14] Anaphylaxis was reported following ingestion of flax.[15] A case of flaxseeds mimicking polyposis coli, a significant risk factor for colorectal carcinoma, has been reported following flaxseed supplementation.[16]