Medically reviewed: June 7, 2018
What is Flax?
The flax plant grows as a slender annual with branches tipped with 1 or 2 delicate blue flowers. Flax was introduced to North America from Europe, and it now grows widely in Canada and the northwestern United States. Additional members of the genus Linum are used throughout the world for their fiber and oil content.
Linum usitatissimum L.
Flax, flaxseed, linseed, lint bells, linum
What is it used for?
Flax has been used for more than 12,000 years as a source of fiber for producing linen. It was one of the earliest plants used for purposes other than food. Flax is prepared from the fibers in the stem of the plant. Flaxseed or linseed oil, derived from the flaxseed, has been used to smooth and soften the skin, and as a laxative, particularly for animals. Flaxseed oil also is used in paints and varnishes and as a waterproofing agent. Flaxseed cakes, the material left after oil has been extracted from the plant, have been used as cattle feed.
Traditional medicinal uses of the plant have been varied and, at times, unusual; one text notes that the seeds have been used to remove foreign material from the eye. A moistened seed would be placed under the closed eyelid for a few moments to allow the material to adhere to the seed, thereby facilitating removal. Other uses include the treatment of coughs and colds, constipation, and urinary tract infections. The related L. catharticum yields a purgative decoction.
Flaxseed and flaxseed oil contain essential fatty acids, particularly alpha linolenic acid, an omega-3 fatty acid and precursor to the longer and less saturated omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid. Flaxseed (but not flaxseed oil) also contains substantial amounts of fiber that may have health benefits similar to other high-fiber products and phytoestrogens that may exert weak estrogenic or antiestrogenic effects depending on biological levels of estradiol. Historically, linseed oil, derived from flaxseed, has been used to smooth and soften skin, as a laxative, and as a treatment for coughs, colds, and urinary tract infections. More recently, flaxseed has been investigated for protection against atherosclerotic heart disease, including reduction of serum cholesterol, platelet aggregation, and inflammatory markers; chemoprotection against some cancers; improvement of menopausal symptoms; improvement of attention deficit hyperactivity disorder symptoms; and renoprotection in patients with systemic lupus erythematosus. However, clinical trials are limited.
What is the recommended dosage?
Flaxseed has been given in clinical trials at dosages from 5 to 50 g per day. Flaxseed oil supplementation equivalent to 200 mg of ALA content has been given.
Contraindicated in patients with known hypersensitivity to flaxseed.
The use of flaxseed and flaxseed oil during pregnancy and lactation is not recommended.
None well documented.
Flaxseed and flaxseed oil appear to be well tolerated, with few adverse reactions reported except type 1 hypersensitivity.
Ingestion of large amounts of raw flax or flaxseed may be harmful because of cyanogenic glycosides. These glycosides have not been detected after flaxseed has been baked.
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