Latin Names—Linum usitatissimum
Flaxseed is the seed of the flax plant, which was one of the earliest cultivated plants in history. It was grown to make a food source in the form of flax meal, which the Roman army added to its bread.
Flaxseeds also provided a valuable oil and its fibers were used to make fabric. Major flaxseed growing countries today include Canada and the United States.
Flaxseeds are available whole or crushed. To release the nutrition from the seed, whole flaxseeds can be ground in a grinder. This should provide the most potent and freshest form of flaxseed nutrition.
Flaxseed is also available in powder form. Flaxseed oil is available in liquid and capsule form. Flaxseed contains lignans (phytoestrogens, or plant estrogens), while flaxseed oil preparations lack lignans.
Today flaxseed and flaxseed oil are used as an herbal remedy in the hope of improving concerns such as:
- hot flashes and breast pain,
- high cholesterol levels,
- and nutritional support to help prevent cancer.
Research on Benefits of Flaxseed and Flaxseed Oil
- Flaxseed contains soluble fiber, like that found in oat bran, and may have a laxative effect, but it can also worsen constipation. See side effects below.
- Studies of flaxseed preparations to lower cholesterol levels report mixed results. A 2009 review of the clinical research found that cholesterol-lowering effects were more apparent in postmenopausal women and in people with high initial cholesterol concentrations.
- Some studies suggest that alpha-linolenic acid (a substance found in flaxseed and flaxseed oil) may benefit people with heart disease. But not enough reliable data are available to determine whether flaxseed is effective for heart conditions.
- Study results are mixed on whether flaxseed decreases hot flashes.
- Although some population studies suggest that flaxseed might reduce the risk of certain cancers, there is not enough research to support a recommendation for this use.
- The National Center for Complementary and Alternative Medicine (NCCAM) is funding studies on flaxseed. Recent studies are looking at its potential role in preventing or treating atherosclerosis (hardening of the arteries), breast cancer, and ovarian cysts.
Side Effects and Cautions Summary
- Flaxseed, like any supplemental fiber source, should be taken with plenty of water; otherwise, it could worsen constipation or, in rare cases, even cause intestinal blockage. Both flaxseed and flaxseed oil can cause diarrhea.
- Flaxseed and flaxseed oil can cause pimples.
- The fiber in flaxseed may lower the body’s ability to absorb medications that are taken by mouth. Flaxseed should not be taken at the same time as any conventional oral medications or other dietary supplements.
- Tell your health care providers about any complementary and alternative practices you use. Give them a full picture of what you do to manage your health to help ensure coordinated and safe care. Complementary or alternative therapy should not be used in place of conventional medical care or to delay seeking that care.
- Flaxseed. In: Blumenthal M, Goldberg A, Brinckman J, eds. Herbal Medicine: Expanded Commission E Monographs. Newton, MA: Lippincott Williams & Wilkins; 2000:134–138.
- Flaxseed. Natural Medicines Comprehensive Database Web site. Accessed at www.naturaldatabase.com on July 10, 2009.
- Flaxseed and flaxseed oil (Linum usitatissimum). Natural Standard Database Web site. Accessed at www.naturalstandard.com on July 10, 2009.
- Flaxseed oil. Natural Medicines Comprehensive Database Web site. Accessed at www.naturaldatabase.com on July 10, 2009.
- Pan A, Yu D, Demark-Wahnefried W. Meta-analysis of the effects of flaxseed interventions on blood lipids. American Journal of Clinical Nutrition. 2009;90(2):288–297.
For More Information
The NCCAM Clearinghouse provides information on CAM and NCCAM, including publications and searches of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical advice, treatment recommendations, or referrals to practitioners.
Toll-free in the U.S.: 1-888-644-6226
TTY (for deaf and hard-of-hearing callers): 1-866-464-3615
Web site: nccam.nih.gov
NIH Office of Dietary Supplements
Web site: www.ods.od.nih.gov
NIH National Library of Medicine’s MedlinePlus
Flaxseed Listing: www.nlm.nih.gov/medlineplus/druginfo/natural/patient-flaxseed.html
Source: National Center for Complementary and Alternative Medicine, Flaxseed and Flaxseed Oil Fact Sheet, Created May 2006, Updated July 2010