Flaxseed and Flaxseed Oil

© Steven Foster

This fact sheet provides basic information about flaxseed and flaxseed 

oil—common names, what the science says, potential side effects and 

cautions, and resources for more information.

Common Names—flaxseed, linseed

Latin Name—Linum usitatissimum

Flaxseed is the seed of the flax plant, which is believed to have 

originated in Egypt. It grows throughout Canada and Northwestern 

United States. Flaxseed oil comes from flaxseeds. The most common 

folk or traditional use of flaxseed is as a laxative; it is also used for hot 

flashes and breast pain. Flaxseed oil has different folk or traditional 

uses, including arthritis. Both flaxseed and flaxseed oil have been used 

for high cholesterol levels and in an effort to prevent cancer.

Whole or crushed flaxseed can be mixed with water or juice and taken by 

mouth. Flaxseed is also available in powder form. Flaxseed oil is available 

in liquid and capsule forms. Flaxseed contains lignans (phytoestrogens, 

or plant estrogens), while flaxseed oil preparations lack lignans.

What the Science Says 

• Flaxseed contains soluble fiber, like that found in oat bran, and may 

have a laxative effect.

• 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.

• 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 

• Flaxseed and flaxseed oil supplements seem to be well tolerated. Few side effects have been reported.

• 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.

• 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 all your health care providers about any complementary health practices you use. Give them a 

full picture of what you do to manage your health. This will help ensure coordinated and safe care. 

For tips about talking with your health care providers about complementary and alternative 

medicine, see NCCAM’s Time to Talk campaign at nccam.nih.gov/timetotalk/. 

Sources

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

Visit the NCCAM Web site at nccam.nih.gov and view Using Dietary Supplements Wisely

(nccam.nih.gov/health/supplements/wiseuse.htm).

NCCAM Clearinghouse

Toll-free in the U.S.: 1-888-644-6226

TTY (for deaf and hard-of-hearing callers): 1-866-464-3615

E-mail: info@nccam.nih.gov

PubMed®

Web site: www.ncbi.nlm.nih.gov/sites/entrez

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/991.html

This publication is not copyrighted and is in the public domain. Duplication is encouraged.

NCCAM has provided this material for your information. It is not intended to substitute for the medical expertise and advice of your 

primary health care provider. We encourage you to discuss any decisions about treatment or care with your health care provider. 

The mention of any product, service, or therapy is not an endorsement by NCCAM.

National Institutes of Health

♦♦♦

U.S. Department of Health and Human Services

D313

Created May 2006

Updated April 2012