Related Terms

• Alashi, alpha-linolenic acid, Barlean's Flax Oil, Barlean's Vita-Flax, brazen, common flax, DHA, docosahexaenoic acid, eicosapentaenoic acid, EPA, Flachssamen (German), flax, gamma-linolenic acid, graine de lin (French), hu-ma-esze (Chinese), keten (Turkish), Leinsamen (German), Linaceae (family), linen flax, Lini semen, lino (Spanish, Italian), lino usuale (Italian), linseed, linseed oil, lint bells, linum, Linum catharticum, Linum humile seeds, omega-3 fatty acid, phytoestrogen, prebiotic bread, sufulsi, tesi-mosina, Type I Flaxseed/Flaxseed (51-55% alpha-linolenic acid), Type II Flaxseed/CDC-flaxseed (2-3% alpha-linolenic acid), Winterlien (German).

Background

• Flaxseed and its derivative flaxseed oil (or linseed oil) are rich sources of the essential fatty acid alpha-linolenic acid (ALA), which is a biologic precursor to omega-3 fatty acids such as eicosapentaenoic acid. Although omega-3 fatty acids have been associated with improved cardiovascular outcomes, evidence from human trials is mixed regarding the efficacy of flaxseed products for coronary artery disease or hyperlipidemia (high lipid levels).

• The lignans of flaxseed (not flaxseed oil) possess in vitro antioxidant and estrogen-like properties, prompting theories about their efficacy for the treatment of breast cancer. However, there is not sufficient human evidence to make a strong conclusion. As a source of fiber, flaxseed (not flaxseed oil) taken by mouth possesses laxative properties. In large doses, or when taken with inadequate water, flaxseed may cause bowel obstruction. The effects of flaxseed on blood glucose levels are not clear, although hyperglycemic (increased blood sugar) effects have been reported with omega-3 fatty acids in general.

• Flaxseed oil contains only the ALA component of flaxseed and not the fiber or lignan components. Therefore, flaxseed oil may share the purported lipid-lowering properties of flaxseed but not its proposed laxative or anticancer abilities.

Scientific Evidence

Tradition/Theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious and should be evaluated by a qualified health care professional.

• Abdominal pain, acne, acute respiratory distress syndrome (ARDS), allergic reactions (delayed hypersensitivity reactions), anticoagulant (blood thinner), antioxidant, antiplatelet agent, bipolar disorder, bladder inflammation, boils, bowel irritation, bronchial irritation, burns (poultice), catarrh (inflammation of mucous membranes), colon cancer, cough suppressant, cystitis, depression, diabetic nephropathy, diarrhea, diverticulitis, dry skin, dysentery (severe diarrhea), eczema (skin rashes), enteritis (intestinal inflammation), expectorant, eye cleansing (debris in the eye), gastritis (stomach inflammation), glomerulonephritis (a type of kidney inflammation), gonorrhea, headache, infections, inflammation, interstitial nephritis (a type of kidney inflammation), irritable bowel syndrome, laxative-induced colon damage, liver protection, malaria, melanoma, menstrual luteal phase disorders, multiple sclerosis, ovarian disorders, pharyngitis, pimples, psoriasis, rheumatoid arthritis, skin infections, skin inflammation, skin irritation (emollient), sore throat, stomach pain, stomach upset, stroke, systemic lupus erythematosus (an autoimmune disorder), ulcerative colitis, upper respiratory tract infection, urinary tract infection, vaginitis (vaginal inflammation), vision improvement.

Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)

• Flaxseed oil is most often taken by mouth in a liquid form, which contains approximately seven grams of alpha-linolenic acid (ALA) and approximately 130 calories per 15-milliliter tablespoon.

• Flaxseed oil capsules (one or two grams) have been taken by mouth daily for 180 days.

• Flaxseed flour (30-100 grams) may be mixed with water to form a moist compress and applied to the skin three times daily.

• A single whole flaxseed has been placed under the eyelid to allow a foreign body or mucus to adhere to it, thereby facilitating removal from the eye. This process may be unsafe, and it is suggested that a healthcare professional be consulted for removal of foreign bodies from the eye.

• For benign prostatic hypertrophy (BPH), 300 and 600 milligrams of a flaxseed lignan extract have been taken by mouth daily for four months.

• For breast cancer, 5-25 grams daily has been taken by mouth for up to four months.

• For cyclic mastalgia, flax muffins or baked products, with flax contents of 25-50 grams, are commonly taken by mouth in clinical trials for up to six months.

• For diabetes, flax muffins or baked products, with flax contents of 25-50 grams, are commonly taken by mouth in clinical trials for up to six months.

• For gastritis or enteritis, one tablespoon of whole or bruised flaxseed mixed with 150 milliliters of liquid has been taken by mouth 2-3 times daily.

• For hyperlipidemia, flax muffins or baked products, with flax contents of 25-50 grams, are commonly taken by mouth in clinical trials for up to six months.

• As a laxative, 2-3 tablespoons of bulk flaxseed mixed in 10 times the amount of water have been taken by mouth; 45 grams daily has also been used.

• For menopausal symptoms, 5-25 grams has been taken by mouth daily for up to four months; 40 grams of flaxseed has also been taken by mouth daily.

• For lupus nephritis, 30 grams of flaxseed has been taken by mouth daily.

• For obesity, 30 grams of flaxseed flour has been taken by mouth daily for two weeks.

Children (under 18 years old)

• For attention-deficit hyperactivity disorder (ADHD), flax oil (200 milligrams of ALA content), along with 25 milligrams of vitamin C, has been taken by mouth twice daily for three months.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Allergies

• Avoid with a known allergy or hypersensitivity to flaxseed (Linum usitatissimum), flaxseed oil, its constituents, or any other members of the Linaceae plant family. Hypersensitivity reactions to flaxseed following occupational exposure have been reported. Diarrhea; intestinal and abdominal pain; itching, including itchy palms and soles and itchy, weeping eyes; hives; malaise; nasal obstruction; nausea; shortness of breath; sneezing; vomiting; and watery discharge have been reported.

Side Effects and Warnings

• Flaxseed may cause gastrointestinal symptoms, headache, "heart problems," hives, increased red blood cell counts, increased risk of prostate cancer, intestinal obstruction, mania or hypomania (in bipolar patients), prolonged luteal phases, rapid breathing, respiratory disease (in flax farmers), vomiting, and weight gain or weight loss. An overdose of flaxseed or flaxseed oil may result in weakness, unstable gait, paralysis, or seizures.

• Raw flaxseed or flaxseed plant may increase blood levels of cyanide, a toxic chemical.

• Flaxseed may cause low blood pressure. Caution is advised in patients with blood pressure disorders and those taking drugs, herbs, or supplements that affect blood pressure.

• Based on the available evidence, flaxseed, which contains alpha-linolenic acid (ALA), should be avoided in patients with prostate cancer or those at risk for prostate cancer.

• Use flaxseed and flaxseed oil cautiously in patients with elevated triglycerides, as these agents may raise or lower triglyceride levels.

• Flaxseed may increase the risk of bleeding and bleeding time. Caution is advised in patients with bleeding disorders or those taking drugs, herbs, or supplements that may increase the risk of bleeding. Dosing adjustments may be necessary.

• Flaxseed may lower blood sugar levels. Caution is advised in patients with diabetes or low blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

• Use cautiously in patients using laxatives, as flaxseed, particularly at higher doses (more than 30 grams daily), caused loose stools; theoretically, concurrent use may increase the risk of diarrhea.

• Use cautiously in patients using furosemide or ketoprofen, as flaxseed decreased the absorption of these drugs.

• Because flaxseed contains estrogen-like chemicals, the effects of other agents believed to have estrogen-like properties may be altered.

• Use flaxseed (not flaxseed oil) cautiously in women with hormone-sensitive conditions, due to its possible estrogenic properties.

• Avoid consumption of immature flaxseed seedpods, as they may be poisonous.

• Avoid topical flaxseed on open wounds or abraded surfaces.

• Avoid flaxseed (not flaxseed oil) in patients with esophageal stricture, ileus, gastrointestinal stricture, or bowel obstruction. Ingestion of flaxseed without adequate fluids may precipitate bowel obstruction.

• Avoid in patients with acute or chronic diarrhea, irritable bowel disease, diverticulitis (small, bulging sacs or pouches of the inner lining of the intestine that become inflamed or infected), or inflammatory bowel disease, due to the potential laxative effect of flaxseed.

• Some natural medicine textbooks advise caution in patients with hypothyroidism, although scant clinical data exist in this area.

• Avoid in pregnant or breastfeeding women, due to a lack of available scientific evidence and safety information.

• Avoid with a known allergy or hypersensitivity to flaxseed (Linum usitatissimum), flaxseed oil, their constituents, or any other members of the Linaceae plant family. Hypersensitivity reactions to flaxseed following occupational exposure have been reported. Diarrhea; intense general malaise; intestinal and abdominal pain; itching, including itchy palms and soles and itchy, weeping eyes; hives; nasal obstruction; nausea; shortness of breath; sneezing; vomiting; and watery discharge have been reported.

Pregnancy and Breastfeeding

• Avoid in pregnant or breastfeeding women, due to a lack of available scientific evidence and safety information.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

• Consumption of flaxseed (not flaxseed oil) may decrease the absorption of coadministered medications, vitamins, or minerals taken by mouth. These agents should be taken one hour before or two hours after flaxseed to prevent decreased absorption.

• Flaxseed may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin®) or heparin, antiplatelet drugs such as clopidogrel (Plavix®), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

• Flaxseed may cause low blood pressure. Caution is advised in patients with blood pressure disorders and those taking drugs, herbs, or supplements that affect blood pressure.

• Flaxseed may lower blood sugar levels. Caution is advised when using medications that may also lower blood sugar. Patients taking insulin or drugs for diabetes by mouth should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.

• Because flaxseed contains estrogen-like chemicals, the effects of other agents believed to have estrogen-like properties may be altered.

• Flaxseed may interact with anticancer agents, anti-inflammatories (such as ketoprofen), antiobesity agents, diuretics (loop, such as furosemide), laxatives, lipid-lowering agents, stool softeners, or tamoxifen.

Interactions with Herbs and Dietary Supplements

• Consumption of flaxseed (not flaxseed oil) may decrease the absorption of coadministered medications, vitamins, or minerals that are taken by mouth. These agents should be taken by mouth one hour before or two hours after flaxseed to prevent decreased absorption.

• Flaxseed may increase the risk of bleeding when taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba, and fewer cases with garlic and saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases.

• Flaxseed may cause low blood pressure. Caution is advised in patients taking herbs or supplements that lower blood pressure.

• Flaxseed may lower blood sugar levels. Caution is advised when using herbs or supplements that may also lower blood sugar. Blood glucose levels may require monitoring, and doses may need adjustment.

• Because flaxseed contains estrogen-like chemicals, the effects of other agents believed to have estrogen-like properties may be altered.

• Flaxseed may interact with anticancer agents, anti-inflammatories, antiobesity agents, antioxidants, diuretics, laxatives, lipid-lowering agents, processing or cooking, psyllium, soy, stool softeners, or vitamin E.

Author Information

• This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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2. Barre DE, Mizier-Barre KA, Griscti O, et al. High dose flaxseed oil supplementation may affect fasting blood serum glucose management in human type 2 diabetics. J Oleo Sci 2008;57(5):269-273. View Abstract

3. Basch E, Bent S, Collins J, et al. Flax and flaxseed oil (Linum usitatissimum): a review by the Natural Standard Research Collaboration. J Soc Integr Oncol 2007;5(3):92-105. View Abstract

4. Bloedon LT, Balikai S, Chittams J, et al. Flaxseed and cardiovascular risk factors: results from a double blind, randomized, controlled clinical trial. J Am Coll Nutr 2008;27(1):65-74. View Abstract

5. Dodin S, Lemay A, Jacques H, et al. The effects of flaxseed dietary supplement on lipid profile, bone mineral density, and symptoms in menopausal women: a randomized, double-blind, wheat germ placebo-controlled clinical trial. J Clin Endocrinol Metab 2005;90(3):1390-1397. View Abstract

6. Harper CR, Edwards MJ, DeFilippis AP, et al. Flaxseed oil increases the plasma concentrations of cardioprotective (n-3) fatty acids in humans. J Nutr 2006;136(1):83-87. View Abstract

7. Jenkins DJ, Kendall CW, Vidgen E, et al. Health aspects of partially defatted flaxseed, including effects on serum lipids, oxidative measures, and ex vivo androgen and progestin activity: a controlled crossover trial. Am J Clin Nutr 1999;69(3):395-402. View Abstract

8. Kaul N, Kreml R, Austria JA, et al. A comparison of fish oil, flaxseed oil and hempseed oil supplementation on selected parameters of cardiovascular health in healthy volunteers. J Am Coll Nutr 2008;27(1):51-58. View Abstract

9. Knudsen VK, Hansen HS, Osterdal ML, et al. Fish oil in various doses or flax oil in pregnancy and timing of spontaneous delivery: a randomised controlled trial. BJOG 2006;113(5):536-543. View Abstract

10. Legrand P, Schmitt B, Mourot J, et al. The consumption of food products from linseed-fed animals maintains erythrocyte omega-3 fatty acids in obese humans. Lipids 2010;45(1):11-9. View Abstract

11. Lewis JE, Nickell LA, Thompson LU, et al. A randomized controlled trial of the effect of dietary soy and flaxseed muffins on quality of life and hot flashes during menopause. Menopause 2006;13(4):631-642. View Abstract

12. Makrides M, Neumann MA, Jeffrey B, et al. A randomized trial of different ratios of linoleic to alpha-linolenic acid in the diet of term infants: effects on visual function and growth. Am J Clin Nutr 2000;71(1):120-129. View Abstract

13. Nordstrom DC, Honkanen VE, Nasu Y, et al. Alpha-linolenic acid in the treatment of rheumatoid arthritis. A double- blind, placebo-controlled and randomized study: flaxseed vs. safflower seed. Rheumatol Int 1995;14(6):231-234. View Abstract

14. Stoll AL, Severus WE, Freeman MP, et al. Omega 3 fatty acids in bipolar disorder: a preliminary double-blind, placebo-controlled trial. Arch Gen Psychiatry 1999;56(5):407-412. View Abstract

15. Stuglin C, Prasad K. Effect of flaxseed consumption on blood pressure, serum lipids, hemopoietic system and liver and kidney enzymes in healthy humans. J Cardiovasc Pharmacol Ther 2005;10(1):23-27. View Abstract