Flaxseed or linseed (Linum usitatissimum L.) comes from the flax plant, an annual herb. The ancient Egyptians used flaxseed as both food and medicine. They also used the fiber from the flax plant to make clothes, fishnets, and other products. Historically, flaxseed has been primarily used as a laxative. It is high in fiber and a gummy material called mucilage. These substances expand when they come in contact with water, so they add bulk to stool and help it move more quickly through the gastrointestinal tract.
The seeds and oil of the flax plant also contain substances that are healthy. Flaxseed and flaxseed oil are rich in alpha-linolenic acid (ALA), an omega-3 fatty acid that may be helpful for heart disease, inflammatory bowel disease, arthritis, and a variety of other health problems. Other plants that provide ALA include canola (rapeseed), soybean oil, walnuts, and pumpkin seed.
It is important to maintain a good balance of omega-3 and omega-6 -- another essential fatty acid -- in your diet, as these two substances work together to promote health. Mackerel, salmon, and walnuts are also good sources of omega-3 fatty acids. Other omega-3 fatty acids include those found in fish oil (docosahexaenoic acid or DHA, and eicosapentaenoic acid or EPA).
Flaxseed oil contains only ALA part of flaxseed, not the fiber or lignans in the seed. Studies suggest that flaxseed may play a role in the prevention and treatment of the following health conditions:
People who eat a Mediterranean diet tend to have higher HDL ("good") cholesterol levels. The Mediterranean diet has a healthy balance of omega-3, omega-6, and omega-9 (found in olive oil) fatty acids. It includes whole grains, root and green vegetables, fruits, fish and poultry, olive and canola oils, and ALA from flaxseed, flaxseed oil, and walnuts. It limits the amount of red meat, butter, and cream.
In lab tests and animal studies, flaxseed and flaxseed oil have been reported to lower cholesterol. Human studies have had mixed results. One human study found that people who added flaxseed to a low-cholesterol diet lowered their LDL ("bad") cholesterol and triglycerides (fats in the blood).
A diet rich in fruits, vegetables, whole grains, nuts or legumes, and ALA-rich foods may reduce the risk of heart attack and stroke, both as first-time events and after the first heart attack or stroke. One of the best ways to help prevent and treat heart disease is to eat a low-fat diet, avoiding foods rich in saturated and trans-fats and eating those are rich in monounsaturated and polyunsaturated fats, including omega-3 fatty acids from flaxseed. Evidence suggests that people who eat an ALA-rich diet are less likely to have a fatal heart attack.
Several human studies suggest that diets rich in omega-3 fatty acids (including ALA) may lower blood pressure in people with hypertension.
One small study compared flaxseed to hormone replacement therapy (HRT) in menopausal women and reported that 40 g of flaxseed worked as well as HRT for mild menopausal symptoms (hot flashes, mood disturbances, vaginal dryness). But the study was not well designed, and another, larger study found that flaxseed did not improve symptoms like hot flashes nor did it protect against bone loss.
Lignans from flaxseed
In addition to the important omega-3 fatty acid ALA, flaxseed -- not the oil -- also contains a group of chemicals called lignans that may help protect the body from cancer. Lignans are phytoestrogens -- plant compounds that act like the hormone estrogen.
Because of the estrogen-like activity of lignans in flaxseed, scientists aren' t sure whether flaxseed would be harmful or helpful for breast cancer. Laboratory studies have reported reduction in breast tumor growth and metastasis (spreading) in rats. There has been only one clinical study in humans, in which postmenopausal women who were newly diagnosed with breast cancer ate a muffin with flaxseed 25 grams dietary flaxseed every day for 40 days. The study found that adding flaxseed to the diet may have the potential to reduce tumor growth in women with breast cancer, but much more research is needed.
Animal studies show that lignans may slow the growth of colon tumor cells. Population studies suggest that flaxseed may reduce the number of abnormal cell growths, which are early markers of colon cancer. Clinical trials in people are needed, however.
Results from studies are confusing when it comes to prostate cancer and flaxseed. A few studies have seemed to show that ALA intake was associated with an increased risk for prostate cancer. But other studies have found that flaxseed may benefit men at risk for prostate cancer. In one study, men with a precancerous prostate condition called PIN had lower PSA levels (a marker of prostate cancer) when they ate 30 g of flaxseed daily along with a low-fat diet. In men who had prostate cancer, 30 g of flaxseed daily and a low-fat diet did not lower PSA levels, but it did appear to lower levels of testosterone and slow down the rate of tissue growth. More studies are needed to understand how flaxseed may affect prostate cancer.
Researchers are investigating whether omega-3 fatty acids may help protect against certain infections and in treating conditions including ulcers, migraine headaches, attention deficit/hyperactivity disorder, addiction, eating disorders, preterm labor, emphysema, psoriasis, glaucoma, Lyme disease, lupus, and panic attacks.
Flax is an annual plant that thrives in deep moist soils rich in sand, silt, and clay. The small, oval-shaped seeds of the flax plant contain oil, sometimes called linseed oil.
Flaxseed contains several plant chemicals that may be healthy, including:
Flaxseed acts as a laxative because of its fiber and mucilage content. Phytoestrogens, known as lignans, may help protect against some kinds of cancer. Other health benefits of flaxseed, such as protection from heart disease and arthritis, are probably due to a high concentration of the omega-3 fatty acid ALA.
Flaxseed oil should be refrigerated. Use whole flaxseeds within 24 hours of grinding, otherwise the ingredients lose their activity. Flaxseeds are also available ground in a special mylar package so that the components in the flaxseeds stay active. Ripe seeds, linseed cakes, powder, capsules, and flaxseed oil are all available at health food and grocery stores.
Flaxseed oil may be added to a child's diet to help balance fatty acids.
Children (2 - 12 years): Ask your doctor to help you determine the right dose. One example is using 1 teaspoonful (tsp) of ground flaxseeds, or 1 tsp of fresh flaxseed oil for constipation.
Flaxseed: Take 1 tablespoonful (tbsp), 2 - 3 times daily or 2 - 4 tbsp, 1 time daily. Grind before eating and take with lots of water.
Flaxseed oil: Take 1 - 2 tablespoonfuls daily, or 1 - 2 capsules daily. Flaxseed oil is often used in a liquid form, which contains approximately 7 g of ALA per 15 mL tbsp, and contains approximately 130 calories.
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.
Although studies have found that eating fish -- which includes omega-3 fatty acids -- regularly may reduce the risk of macular degeneration, a recent study of two large groups of men and women found that diets rich in ALA may increase the risk of macular degeneration. Ask your health care provider.
Do not eat raw or unripe flaxseeds -- they may be poisonous.
Women with breast, uterine, and ovarian cancer or endometriosis should ask their doctor before taking flaxseed, because of its potential to act like estrogen in the body.
Some researchers think flaxseed should not be taken if you are pregnant, because it may act like estrogen in the body. Ask your doctor before taking flaxseed if you are pregnant or breastfeeding.
Men with prostate cancer should ask their doctor before taking flaxseed, because of conflicting research about its effect on prostate cancer.
People with a bowel obstruction, inflamed bowel, or narrowed esophagus should not take flaxseed. It is high in fiber and could make the condition worse.
Flaxseed supplements may alter the effects of some prescription and nonprescription medications. If you are currently being treated with any of the following medications, you should not use flaxseed without first talking to your health care provider:
Blood-thinning medications -- Omega-3 fatty acids may increase the risk of bleeding, especially if you also take blood thinners such as warfarin (Coumadin) or aspirin. In some cases, the combination of aspirin and omega-3 fatty acids may be helpful, but they should not be taken together except under a doctor' s supervision.
Medications for diabetes -- Flaxseed may lower blood sugar levels. If you are taking medicines for diabetes, including insulin, you should use flaxseed (ALA) only under your doctor' s supervision.
Birth control pills or hormonal replacement therapy (HRT) -- Flaxseed may change hormonal levels and change the effects of oral contraceptives or HRT. If you are taking oral contraceptive or HRT, ask your doctor before taking flaxseed.
Linseed; Linum usitatissimum
Angerer P, von Schacky C. n-3 polyunsaturated fatty acids and the cardiovascular system. Curr Opin Lipidol. 2000;11(1):57-63.
Arnold LE, Kleykamp D, Votolato N, Gibson RA, Horrocks L. Potential link between dietary intake of fatty acid and behavior: pilot exploration of serum lipids in attention-deficit hyperactivity disorder. J Child Adolesc Psychopharmacol. 1994;4(3):171-182.
Boelsma E, Hendriks HF. Roza L. Nutritional skin care: health effects of micronutrients and fatty acids. Am J Clin Nutr. 2001;73(5):853-864.
Bommareddy A, Arasada BL, Mathees DP, Dwivedi C. Chemopreventive effects of dietary flaxseed on colon tumor development. Nutr Cancer. 2006;54(2):216-22.
Bruinsma KA, Taren DL. Dieting, essential fatty acid intake, and depression. NutritionRev. 2000;58(4):98-108.
Caron MF, White CM. Evaluation of the antihyperlipidemic properties of dietary supplements. Pharmacotherapy. 2001;21(4):481-487.
Cellini M, Caramazzu N, Mangiafico P, Possati GL, Caramazza R. Fatty acid use in glaucomatous optic neuropathy treatment. Acta Ophthalmol Scand Suppl. 1998;227:41-42.
Cho E, Hung S, Willet WC, Spiegelman D, Rimm EB, Seddon JM, et al. Prospective study of dietary fat and the risk of age-related macular degeneration. Am J Clin Nutr. 2001;73(2):209-218.
Clark WF, Kortas C, Heidenheim AP, Garland J, Spanner E, Parbtani A. Flaxseed in lupus nephritis: a two–year nonplacebo-controlled crossover study. J Am Coll Nutr. 2001;20(2 Suppl):143-148.
Curtis CL, Hughes CE, Flannery CR, Little CB, Harwood JL, Caterson B. N-3 fatty acids specifically modulate catabolic factors involved in articular cartilage degradation. J Biol Chem. 2000;275(2):721-724.
Dahl WJ, Lockert EA, Cammer AL, Whiting SJ. Effects of flax fiber on laxation and glycemic response in healthy volunteers. J Med Food. 2005;8(4):508-11.
de Logeril M, Salen P, Martin JL, Monjaud I, Delaye J, Mamelle N. Mediterranean diet, traditional risk factors, and the rate of cardiovascular complications after myocardial infarction: final report of the Lyon Diet Heart Study. Circulation. 1999;99(6):779-785.
Demark-Wahnefried W, Price DT, Polascik TJ, et al. Pilot study of dietary fat restriction and flaxseed supplementation in men with prostate cancer before surgery: exploring the effects on hormonal levels, prostate-specific antigen, and histopathologic features. Urology. 2001;58(1):47-52.
Deutch B. Menstrual pain in Danish women correlated with low n-3 polyunsaturated fatty acid intake. Eur J Clin Nutr. 1995;49(7):508-516.
Dodin S et al. Flaxseed on cardiovascular disease markers in healthy menopausal women: a randomized, double-blind, placebo-controlled trial. Nutrition. 2008;24(1):23-30.
Dodin S, Lemay A, Jacques H, Legare F, Forest JC, Masse B. 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):1390-7.
Edwards R, Peet M, Shay J, Horrobin D. Omega-3 polyunsaturated fatty acid levels in the diet and in red blood cell membranes of depressed patients. J Affect Disord. 1998;48(2-3):149-155.
Freeman VL, Meydani M, Yong S, Pyle J, Flanigan RC, Waters WB, Wojcik EM. Prostatic levels of fatty acids and the histopathology of localized prostate cancer. J Urol. 2000;164(6):2168-2172.
Frieri G, Pimpo MT, Palombieri A, Melideo D, Marcheggiano A, Caprilli R, et al. Polyunsaturated fatty acid dietary supplementation: an adjuvant approach to treatment of Helicobacter pylori infection. Nut Res. 2000;20(7):907-916.
Geerling BJ, Badart-Smook A, van Deursen C, van Houwelingen AC, Russel MG, Stockbrugger RW, et al. Nutritional supplementation with N-3 fatty acids and antioxidants in patients iwth Crohn's disease in remission: effects on antioxidant status and fatty acid profile. IBD. 2000;6(2):77-84.
GISSI-Prevenzione Investigators. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Lancet. 1999;354:447-455.
Griel AE, Kris-Etherton PM, Hilpert KF, Zhao G, West SG, Corwin RL. An increase in dietary n-3 fatty acids decreases a marker of bone resorption in humans. Nutr J. 2007;6(1):2 [Epub ahead of print].
Hall C 3rd, Tulbek MC, Xu Y. Flaxseed. Adv Food Nutr Res. 2006;51:1-97.
Hallund J, Tetens I, Bugel S, Tholstrup T, Ferrari M, Teerlink T, Kjaer A, Wiinberg N. Daily consumption for six weeks of a lignan complex isolated from flaxseed does not affect endothelial function in healthy postmenopausal women. J Nutr. 2006;136(9):2314-8.
Haggans CJ, Hutchins AM, Olson BA, Thomas W, Martini MC, Slavin JL. Effect of flaxseed consumption on urinary estrogen metabolites in postmenopausal women. Nutr Canc. 1999;33(2):188-195.
Harper CR, Edwards MJ, DeFilipis AP, Jacobson TA. Flaxseed oil increases the plasma concentrations of cardioprotective (n-3) fatty acids in humans. J Nutr. 2006;136(1):83-7.
Harris WS. N-3 fatty acids and serum lipoproteins: human studies. Am J Clin Nutr. 1997;65(5):1645S (10).
Hibbeln JR, Salem N, Jr. Dietary polyunsaturated fatty acids and depression: when cholesterol does not satisfy. Am J Clin Nut. 1995;62(1):1-9.
Holman RT, Adams CE, Nelson RA, Grater SJ, Jaskiewicz JA, Johnson SB, et al. Patients with anorexia nervosa demonstrate deficiencies of selected essential fatty acids, compensatory changes in nonessential fatty acids and decreased fluidity of plasma lipids. J Nutr 1995;125:901-907.
Hu FB, Stampfer MJ, Manson JE et al. Dietary intake of alpha-linolenic acid and risk of fatal ischemic heart disease among women. Am J Clin Nutr. 1999;69:890-897.
Hutchins AM, Martini MC, Olson BA, Thomas W, Slavin JL. Flaxseed consumption influences endogenous hormone concentrations in postmenopausal women. Nutr Cancer. 2001;39(1):58-65.
Jenab M, Thompson LU. The influence of flaxseed and lignans on colon carcinogenesis and ß-glucuronidase activity. Carcinogenesis. 1996;17(6):1343-1348.
Klurfeld DM, Bull AW. Fatty acids and colon cancer in experimental models. Am J Clin Nut. 1997;66(6 Suppl):1530S-1538S.
Kremer JM. N-3 fatty acid supplements in rheumatoid arthritis. Am J Clin Nutr. 2000;(suppl 1):349S-351S.
Kris-Etherton P, Eckel RH, Howard BV, St. Jeor S, Bazzare TL. AHA Science Advisory: Lyon Diet Heart Study. Benefits of a Mediterranean-style, National Cholesterol Education Program/American Heart Association Step I Dietary Pattern on Cardiovascular Disease. Circulation. 2001;103:1823
Kurzer MS, Xu X. Dietary phytoestrogens. Ann Rev Nutr. 1997;17:353-381.
Laugharne JD, Mellor JE, Peet M. Fatty acids and schizophrenia. Lipids. 1996;31(Suppl):S-163-165.
Leitzmann MF, Stampfer MJ, Michaud DS, Augustsson K, Colditz GC, Willett WC, Giovannucci EL. Dietary intake of n-3 and n-6 fatty acids and the risk of prostate cancer. Am J Clin Nutr. 2004;80(1):204-16.
Lewis JE, Nickell LA, Thompson LU, Szalai JP, Kiss A, Hilditch JR. 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):631-42.
Lockwood K, Moesgaard S, Hanioka T, Folkers K. Apparent partial remission of breast cancer in 'high risk' patients supplemented with nutritional antioxidants, essential fatty acids, and coenzyme Q10. Mol Aspects Med. 1994;15Suppl:s231-s240.
Lorenz-Meyer H, Bauer P, Nicolay C, Schulz B, Purrmann J, Fleig WE, et al. Omega-3 fatty acids and low carbohydrate diet for maintenance of remission in Crohn's disease. A randomized controlled multicenter trial. Study Group Members (German Crohn's Disease Study Group). Scan J Gastroenterol. 1996;31(8):778-785.
Lucas EA, Wild RD, Hammond LJ, Khalil DA, Juma S, Daggy BP, Stoecker BJ, Arjmandi BH. Flaxseed improves lipid profile without altering biomarkers of bone metabolism in postmenopausal women. J Clin Endocrinol Metab. 2002;87(4):1527-32.
Mandasescu S, Mocanu V, Dascalita AM, Haliga R, Nestian I, Stitt PA, Luca V. Flaxseed supplementation in hyperlipidemic patients. Rev Med Chir Soc Med Nat Iasi. 2005;109(3):502-6.
Meydani M. Omega-3 fatty acids alter soluble markers of endothelial function in coronary heart disease patients. Nutr Rev. 2000;58(2 pt 1):56-59.
Moyad M. Soy, disease prevention, and prostate cancer. Sem Urol Oncol. 1999;17(2):97-102.
Mozaffarian D. Does alpha-linolenic acid intake reduce the risk of coronary heart disease? A review of the evidence.Altern Ther Health Med. 2005;11(3):24-30; quiz 31, 79.
Newcomer LM, King IB, Wicklund KG, Stanford JL. The association of fatty acids with prostate cancer risk. Prostate. 2001;47(4):262-268.
Peet M, Laugharne JD, Mellor J, et al. Essential fatty acid deficiency in erythrocyte membranes from chronic schizophrenic patients, and the clinical effects of dietary supplementation. Prostaglandins Leukot Essent Fatty Acids. 1996;55(1-2):71-75.
Prasad K. Flaxseed and cardiovascular health. J Cardiovasc Pharmacol. 2009 Nov;54(5):369-77. Review.
Prasad K. Dietary flaxseed in prevention of hypercholesterolemic atherosclerosis. Atherosclerosis. 1997;132(1):69–76.
Prisco D, Paniccia R, Bandinelli B, et al. Effect of medium term supplementation with a moderate dose of n-3 polyunsaturated fatty acid on blood pressure in mild hypertensive patients. Thromb Res. 1998;91:105-112.
Pruthi S et al. Pilot evaluation of flaxseed for the management of hot flashes. J Soc Integr Oncol. 2007;5(3):106-12.\
Rodriguez-Leyva D, Dupasquier CM, McCullough R, Pierce GN. The cardiovascular effects of flaxseed and its omega-3 fatty acid, alpha-linolenic acid. Can J Cardiol. 2010 Nov;26(9):489-96. Review.
Rose DP, Connolly JM, Coleman M. Effect of omega-3 fatty acids on the progression of metastases after the surgical excision of human breast cancer cell solid tumors growing in nude mice. Clin Can Res. 1996;2:1751-1756.
Schwab US, C Callaway J, Erkkila AT, Gynther J, Uusitupa MI, Jarvinen T. Effects of hempseed and flaxseed oils on the profile of serum lipids, serum total and lipoprotein lipid concentrations and haemostatic factors. Eur J Nutr. 006;45(8):470-7.
Seddon JM, Rosner B, Sperduto RD, Yannuzzi L, Haller JA, Blair NP, Willett W. Dietary fat and risk for advanced age-related macular degeneration. Arch Opthalmol. 2001;119(8):1191-1199.
Serraino M, Thompson LY. Flaxseed supplementation and early markers of colon carcinogenesis. Cancer Lett. 1992;63(2):159-165.
Simopoulos AP. Essential fatty acids in health and chronic disease. Am J Clin Nutr. 1999;70(30 Suppl):560S-569S.
Simopoulos AP. Human requirement for N-3 polyunsaturated fatty acids. Poult Sci. 2000;79(7):961-970.
Soyland E, Funk J, Rajka G, Sandberg M, Thune P, Ruistad L, et al. Effect of dietary supplementation with very-long chain n-3 fatty acids in patients with psoriasis. NEJM. 1993;328(25):1812-1816.
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):23-7.
Sung MK, Lautens M, Thompson LU. Mammalian lignans inhibit growth of estrogen-independent human colon tumor cells. Anticancer Research. 1998;18(3A):1405-1408.
von Schacky C, Angere P, Kothny W, Theisen K, Mudra H. The effect of dietary omega-3 fatty acids on coronary atherosclerosis: a randomized, double-blind, placebo-controlled trial. Ann Intern Med. 1999;130:554-562.
Voskuil DW, Feskens EJM, Katan MB, Kromhout D. Intake and sources of alpha-linolenic acid in Dutch elderly men. Euro J Clin Nutr. 1996;50(12):784-787.
Yan L. Dietary flaxseed supplementation and experimental metastasis of melanoma cells in mice. Cancer Letters. 1998;124:181-186.
Zambón D, Sabate J, Munoz S, et al. Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women. Ann Intern Med. 2000;132:538-546.
Zhang W, Wang X, Liu Y, Tian H, Flickinger B, Empie MW, Sun SZ. Dietary flaxseed lignan extract lowers plasma cholesterol and glucose concentration in hypercholesterolaemic subjects. Br J Nutr. 2008;99(6):1301-9.