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Flaxseed And Flaxseed Oil (Linum usitatissimum) Be aware that the U.S. Food and Drug Administration does not strictly regulate herbs and dietary supplements. There is no guarantee of strength, purity or safety of products containing or claiming to contain flaxseed. Decisions to use herbs or supplements should be carefully considered. Individuals using prescription drugs should discuss taking herbs or supplements with a pharmacist or health care professional before starting.
Scientists have studied flaxseed for the following health problems: Constipation | Flaxseed (not flaxseed oil) has been observed to have laxative effects in studies of flaxseed used to treat other medical conditions. There is only limited research in humans on using flaxseed to treat constipation specifically. However, because there is a scientific basis for flaxseed working as a laxative, this evidence, combined with the available limited research, appears to support the laxative effects of flaxseed. It is not clear what dose is safe or effective. | Cardiovascular disease, high cholesterol | Some studies suggest that flaxseed or flaxseed oil may be beneficial for treating disorders such as atherosclerosis (clogged arteries), high cholesterol and high blood pressure. However, these studies have been small, with flaws in their designs, and results of different studies have disagreed with each other. Therefore, it is unclear whether there is any benefit from flaxseed for these conditions. | Diabetes | Although there are several studies in this area, it is not clear what effects flaxseed has on blood sugar levels. | Cancer (general) | Flaxseed and flaxseed oil have been proposed as possible cancer therapies. Animal studies of flaxseed for breast cancer have had mixed results. Studies in humans have mostly looked at effects on hormone levels, and it is not clear if there are any benefits. | Cancer (prostate) | There is limited research of the effects of flaxseed or alpha-linolenic acid (which is in flaxseed) on the risk of developing prostate cancer. This area remains controversial. Some studies report that a low-fat diet supplemented with flaxseed can lower levels of the blood marker prostate-specific antigen (PSA), both in men with enlarged prostate glands and in those with prostate cancer. However, these effects may be due to the effects of fat reduction, and the role of flaxseed in these cases is not clear. Other research in large populations has looked at dietary habits and cancer risk and has suggested that higher levels of alpha-linolenic acid may be associated with an increased risk of developing prostate cancer. Overall, it remains unclear whether flax or flaxseed oil plays a role in the prevention or treatment of prostate cancer. | Kidney disease | Several studies suggest that flaxseed or flaxseed oil may help prevent or treat kidney disease. However, these studies have been small with flaws in their designs, and results of different studies have disagreed with each other. Therefore, it is unclear whether flaxseed has any benefit on kidney disease. | Menopause | There is evidence that flaxseed oil and its effects on hormone levels may help to decrease symptoms of mild menopause. However, studies are limited, and more research is needed to make a conclusion. The overall effects on bone mineral density and lipid profiles remain unclear. |
Flaxseed has been suggested for many other uses, based on tradition or on scientific theories. However, these uses have not been thoroughly studied in humans, and there is limited scientific evidence about safety or effectiveness. Some of these suggested uses are for conditions that are potentially very serious and even life-threatening. You should consult a health care professional before taking flaxseed for any unproven use. Acne
Allergic reactions
Antioxidant
Antiplatelet (blood thinner)
Bipolar disorder
Bladder irritation
Boils
Bowel irritation
Breast cancer
Bronchial irritation
Colon damage
Constipation
Cough
Depression
Diarrhea
Eczema
Emollient
Expectorant
Foreign object removal from eye — whole flaxseed
Gonorrhea
Headache
High blood pressure | HIV
Infections
Inflammation
Liver protection
Lupus
Malaria
Menstrual period disorders
Multiple sclerosis
Ovarian dysfunction
Prostate enlargement
Psoriasis
Respiratory tract infection
Rheumatoid arthritis
Skin inflammation or irritation
Sore throat
Stomach pain
Ulcerative colitis
Urinary tract infection
Vaginal irritation
Visual dysfunction
Weight loss |
Allergies People should avoid flaxseed if they have a known allergy to flaxseed, flaxseed oil or any member of the Linaceae or Linum plant families. Signs of allergy might include rash, itching or shortness of breath. Side Effects Flaxseed has been well tolerated in studies. Some people may experience stomach discomfort, including diarrhea and nausea. Rare side effects include watering eyes, difficulty breathing or rash. These adverse effects may be caused by flaxseed allergies. Other side effects may include symptoms of mania. If you have a history of a psychotic illness and are considering using flaxseed, discuss this with a health care professional. Flaxseed may also increase blood sugar levels. Caution is advised if you take prescription drugs to control your blood sugar levels. In theory, flaxseed may also increase the risk of bleeding. If you have diabetes or use anticoagulants (blood thinners) or antiplatelet drugs and are considering using flaxseed, discuss this with a health care professional. Pregnancy And Breast-Feeding Flaxseed cannot be recommended during pregnancy or breast-feeding because of the risk of birth defects and spontaneous abortion.
Interactions with drugs, supplements and other herbs have not been thoroughly studied. The interactions listed below have been reported in scientific publications. If you are taking prescription drugs, speak with a health care professional or pharmacist before using herbs or dietary supplements. Interactions With Drugs In general, prescription drugs should be taken one hour before flaxseed or two hours after flaxseed because flaxseed may reduce the effectiveness of many drugs, vitamins and minerals. Animal studies suggest that flaxseed may increase the effects of vitamin E, but this has not been studied in humans. In theory, flaxseed may increase the risk of bleeding when used with anticoagulants (blood thinners) or antiplatelet drugs. Examples include warfarin (Coumadin), heparin and clopidogrel (Plavix). Some pain relievers may increase the risk of bleeding if used with flaxseed. Examples include aspirin, ibuprofen (Motrin, Advil) and naproxen (Naprosyn, Aleve, Anaprox). In theory, flaxseed may also increase the effects of some laxatives and stool softeners, such as bisacodyl (Dulcolax) and docusate (Colace). Flaxseed could possibly increase psychotic episodes in patients taking drugs such as lithium (Lithobid) for manic depression. Hormonal drugs may be affected. Dietary flaxseed may increase the effects of tamoxifen, a medication used to treat cancer. Please do not start flaxseed before discussing with your oncologist and pharmacist. Interactions With Herbs And Dietary Supplements Flaxseed may have laxative properties. These effects may be increased if flaxseed is also used with other supplements that possess laxative properties, such as senna or psyllium. As a result of increased laxative effects, the effectiveness of other agents taken by mouth may be reduced. Flaxseed may possess mood-altering properties and, in theory, can interact with other mood-altering herbs or supplements, such as St. John's wort. In theory, flaxseed may increase the risk of bleeding when taken with products such as Ginkgo biloba and garlic ( Allium sativum). Hormonal herbs and supplements may be affected.
The doses listed below are based on scientific research, publications or traditional use. Because most herbs and supplements have not been thoroughly studied or monitored, safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients even within the same brand. Combination products often contain small amounts of each ingredient and may not be effective. Appropriate dosing should be discussed with a health care professional before starting therapy; always read the recommendations on a product's label. The dosing for unproven uses should be approached cautiously, because scientific information is limited in these areas. Safety of use beyond four months has not been studied. Adults (Aged 18 Or Older) Flaxseed liquid: There are no standard or well-studied doses of flaxseed, and many different doses are used traditionally. A dose of one tablespoon of bruised (not ground) flaxseed mixed in six to 12 ounces of liquid and taken by mouth three times daily has been used. Flaxseed powder/flour/soluble fiber: There are no standard or well-studied doses of flaxseed, and many different doses are used traditionally. Some research has used 50 grams per day of ground, raw flaxseed (which may be equivalent to 250 grams of flaxseed flour) for up to four weeks. A common dose for constipation is one to three tablespoons of bulk seed mixed in 10 times the amount of water. Drink daily when needed. Children (Younger Than 18) There is not enough scientific data to recommend flaxseed for use in children, and flaxseed is not recommended because of potential side effects.
Flaxseed and flaxseed oil have been suggested as treatments for many conditions. There is some research to support the use of flaxseed (not flaxseed oil) as a laxative, although it is not clear what dose is safe and effective. There is not enough scientific evidence to support the use of flaxseed or flaxseed oil for any other medical condition. Flaxseed should be avoided in pregnant or breast-feeding women and in children. Flaxseed may increase the risk of bleeding. Safety of use beyond four months has not been studied. Consult a health care professional immediately if you have any side effects. The information in this monograph was prepared by the professional staff at Natural Standard, based on thorough systematic review of scientific evidence. The material was reviewed by the Faculty of the Harvard Medical School with final editing approved by Natural Standard.
- Natural Standard: An organization that produces scientifically based reviews of complementary and alternative medicine (CAM) topics
- National Center for Complementary and Alternative Medicine (NCCAM): A division of the U.S. Department of Health & Human Services dedicated to research
Selected Scientific Studies: Flaxseed And Flaxseed Oil Natural Standard reviewed more than 135 articles to prepare the professional monograph from which this version was created. Some of the more recent studies are listed below: - Anonymous. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico. Lancet 1999;354(9177):447-455.
- Arjmandi BH, Khan DA, Juma S, et al. Whole flaxseed consumption lowers serum LDL-cholesterol and lipoprotein (a) concentrations in postmenopausal women. Nutrit Res 1998;18(7):1203-1214.
- Bloedon LT, Szapary PO. Flaxseed and cardiovascular risk. Nutr Rev 2004;Jan, 62(1):18-27.
- Brooks JD, Ward WE, Lewis JE, et al. Supplementation with flaxseed alters estrogen metabolism in postmenopausal women to a greater extent than does supplementation with an equal amount of soy. Am J Clin Nutr 2004;Feb, 79(2):318-325.
- Chen J, Hui E, Ip T, Thompson LU. Dietary flaxseed enhances the inhibitory effect of tamoxifen on the growth of estrogen-dependent human breast cancer (mcf-7) in nude mice. Clin Cancer Res 2004;Nov 15, 10(22):7703-7711.
- Dabrosin C, Chen J, Wang L, Thompson LU. Flaxseed inhibits metastasis and decreases extracellular vascular endothelial growth factor in human breast cancer xenografts. Cancer Lett 2002;Nov 8, 185(1):31-37.
- Dalais FS, Meliala A, Wattanapenpaiboon N, et al. Effects of a diet rich in phytoestrogens on prostate-specific antigen and sex hormones in men diagnosed with prostate cancer. Urology 2004;Sep, 64(3):510-515.
- 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.
- 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;Mar, 90(3):1390-1397.
- Gross PE, Li T, Theriault M, et al. Effects of dietary flaxseed in women with cyclic mastalgia. Breast Cancer Res Treat 2000;64:49.
- 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(5):890-897.
- Lemay A, Dodin S, Kadri N, et al. Flaxseed dietary supplement versus hormone replacement therapy in hypercholesterolemic menopausal women. Obstet Gynecol 2002;Sep, 100(3):495-504.
- Lin X, Gingrich JR, Bao W, et al. Effect of flaxseed supplementation on prostatic carcinoma in transgenic mice. Urology 2002;Nov, 60(5):919-924.
- Lord RS, Bongiovanni B, Bralley JA. Estrogen metabolism and the diet-cancer connection: rationale for assessing the ratio of urinary hydroxylated estrogen metabolites. Altern Med Rev 2002;Apr, 7(2):112-129.
- Lucas EA, Wild RD, Hammond LJ, et al. Flaxseed improves lipid profile without altering biomarkers of bone metabolism in postmenopausal women. J Clin Endocrinol Metab 2002;Apr, 87(4):1527-1532.
- Manthey FA, Lee RE, Hall CA 3rd.Processing and cooking effects on lipid content and stability of alpha-linolenic acid in spaghetti containing ground flaxseed. J Agric Food Chem 2002;Mar 13, 50(6):1668-1671.
- Newton M, Combest W, Kosier JH, Davis M. Selected herbal dietary supplements used to manage climacteric (menopausal-type) symptoms. Urol Nurs 2002;Aug, 22(4):267-272.
- Ogborn MR, Nitschmann E, Bankovic-Calic N, et al. Dietary flax oil reduces renal injury, oxidized LDL content, and tissue n-6/n-3 FA ratio in experimental polycystic kidney disease. Lipids 2002;Nov, 37(11):1059-1065.
- Oomen CM, Ocke MC, Feskens EJ, et al. Alpha-linolenic acid intake is not beneficially associated with 10-y risk of coronary artery disease incidence: the Zutphen Elderly Study. Am J Clin Nutr 2001;74(4):457-463.
- Prasad K, Mantha SV, Muir AD, et al. Reduction of hypercholesterolemic atherosclerosis by CDC-flaxseed with very low alpha-linolenic acid. Atherosclerosis 1998;136(2):367-375.
- Prasad K. Dietary flax seed in prevention of hypercholesterolemic atherosclerosis. Atherosclerosis 1997;132(1):69-76.
- 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.
- Tarpila S, Aro A, Salminen I, et al. The effect of flaxseed supplementation in processed foods on serum fatty acids and enterolactone. Eur J Clin Nutr 2002;Feb, 56(2):157-165.
- von Schacky C, Angerer P, Kothny W, et al. The effect of dietary omega-3 fatty acids on coronary atherosclerosis: a randomized, double-blind, placebo-controlled trial. Ann Intern Med 1999;130(7):554-562.
Last updated June 23, 2005
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