Flaxseed and Flaxseed Oil (Linum usitatissimum)
  
Flaxseed and Flaxseed Oil (Linum usitatissimum)
Background
Flaxseed and its derivative flaxseed oil/linseed oil are rich sources of the essential fatty acid alpha-linolenic acid, 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.
The lignan constituents of flaxseed (not flaxseed oil) possesses in vitro anti-oxidant and possible estrogen receptor agonist/antagonist properties, prompting theories of efficacy for the treatment of breast cancer. However, there is not sufficient human evidence to make a recommendation. As a source of fiber mucilage, oral flaxseed (not flaxseed oil) may possess laxative properties, although only one human trial has been conducted for this indication. In large doses, or when taken with inadequate water, flaxseed may precipitate bowel obstruction via a mass effect. The effects of flaxseed on blood glucose levels are not clear, although hyperglycemic effects have been reported in one case series.
Flaxseed oil contains only the alpha-linolenic acid component of flaxseed, and not the fiber or lignan components. Therefore, flaxseed oil may share the purported lipid-lowering properties of flaxseed, but not the proposed laxative or anti-cancer abilities.
Preliminary evidence suggests that alpha-linolenic acid may be associated with an increased risk of prostate cancer.
Synonyms
Alashi, alpha-linolenic acid, Barlean's Flax Oil, Barlean's Vita-Flax, brazen, common flax, eicosapentaenoic acid, flachssamen, flax, gamma-linolenic acid, Graine de Lin, leinsamen, hu-ma-esze, Linaceae, linen flax, lini semen, lino, lino usuale, linseed, linseed oil, lint bells, linum, Linum catharticum , Linum humile seeds, keten, omega-3 fatty acid, phytoestrogen, sufulsi, tesi-mosina, Type I Flaxseed/Flaxseed (51-55% alpha-linolenic acid), Type II Flaxseed/CDC-flaxseed (2-3% alpha-linolenic acid), winterlien.
Evidence
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Uses based on scientific evidenceGrade*Laxative (flaxseed, not flaxseed oil)
Early studies in humans suggest that flaxseed can be used as a laxative. However, more information is needed to compare effectiveness and dosing to more commonly used agents.
B
High cholesterol or triglycerides (flaxseed and flaxseed oil)
In laboratory and animal studies, flaxseed and flaxseed oil are reported to lower blood cholesterol levels. Effects on blood triglyceride levels in animals are unclear, with increased levels in some research, and decreased levels in other research. Human studies in this area report mixed results, with decreased blood levels of total cholesterol and low-density lipoprotein ("bad cholesterol") in some studies, but no effect in other studies. Most human research has not been well-designed, and further research is needed before a recommendation can be made.
C
Heart disease (flaxseed and flaxseed oil)
People who have had a heart attack are reported to benefit from diets rich in alpha-linolenic acid, which is found in flaxseed. Good studies that examine the effect of flaxseed on heart disease in humans are not available. It is unclear whether flaxseed supplementation alters the course of heart disease.
C
Breast cancer (flaxseed, not flaxseed oil)
There is currently no information from human studies that flaxseed is effective in preventing or treating breast cancer.
C
Menstrual breast pain (flaxseed, not flaxseed oil)
Early information from one study in women, the results of which have not been fully reported, suggests that flaxseed may reduce menstrual breast pain. However, further study is needed before a recommendation can be made.
C
Menopausal symptoms
There is preliminary evidence from randomized controlled trials that flaxseed oil may help decrease mild menopausal symptoms. Additional research is necessary before a clear conclusion can be drawn and this remains an area of controversy. Patients should consult a doctor and pharmacist about treatment options before starting a new therapy.
C
Diabetes (flaxseed, not flaxseed oil)
Human studies on the effect of flaxseed on blood sugar levels report mixed results. Flaxseed cannot be recommended as a treatment for diabetes at this time.
C
High blood pressure (flaxseed, not flaxseed oil)
In animals, diets high in flaxseed have mixed effects on blood pressure. One study in humans suggests that flaxseed might lower blood pressure. The evidence in this area is not clear, and more research is needed before a recommendation can be made.
C
Kidney disease/Lupus nephritis (flaxseed, not flaxseed oil)
No strong evidence is available in this area. More research is needed before a recommendation can be made.
C
HIV/AIDS
No strong evidence is available in this area, and no recommendation can be made without further research.
C
Prostate cancer (flaxseed, not flaxseed oil)
Several studies in humans suggest an increased risk of prostate cancer with increased intake of alpha-linolenic acid (which is present in flaxseed). Based on the available research, men with prostate cancer or at risk for prostate cancer should avoid flaxseed and alpha-linolenic acid supplements.
D
* Key to grades
A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use (it may not work);
F: Strong scientific evidence against this use (it likely does not work).
Uses based on tradition or 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 healthcare provider.
Abdominal pain, acute respiratory distress syndrome (ARDS), allergic reactions, bladder inflammation, blood thinner, bipolar disorder, boils, bronchial irritation, burns (poultice), colon cancer, cough (suppression or loosening of mucus), debris in the eye, depression, diarrhea, diverticulitis, dry skin, eczema, enlarged prostate, gonorrhea, irritable bowel syndrome, laxative-induced colon damage, liver protection, melanoma, menstrual disorders, ovarian disorders, pimples, psoriasis, rheumatoid arthritis, skin infections, sore throat, ulcerative colitis, upper respiratory tract infection, skin inflammation, stomach upset, urinary tract infection, vision improvement, vaginitis, weight loss.
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.
Standardization
Standardization involves measuring the amount of certain chemicals in products to try to make different preparations similar to each other. It is not always known if the chemicals being measured are the "active" ingredients. In general, flaxseed products are not standardized based on specific chemical components, although products are often evaluated by manufacturers using a number of chemical tests.
Adults (18 years and older)
Flaxseed oil should be kept refrigerated in an opaque (non-transparent) bottle, since its chemical parts may break down if exposed to light, oxygen, or heat. Whole flaxseed can be stored for up to one year in a dry location. Ground flaxseed can be kept in a refrigerator for three months or in a freezer for six months. Flaxseed oil and powder/flour will break down at high temperatures, such as in cooking.
Flaxseed Oil (Liquid Form) : Flaxseed oil contains only the alpha-linolenic acid (ALA) component of flax, not the fiber found in flaxseed. Flaxseed oil is most often used in a liquid form, which contains approximately 7 grams of ALA per 15-milliliter tablespoon and may contain approximately 130 calories.
Flaxseed Oil (Capsule Form) : Flaxseed oil is available in a capsule form, which often contains 500 milligrams alpha-linolenic acid per 1000-milligram capsule (10 calories).
Flaxseed Powder/Flour/Soluble Fiber : Several studies report adults taking ground, raw flaxseeds by mouth in doses up to 50 grams daily for up to four weeks. For shorter periods of time (less than 2 weeks), studies use doses of 10 to 60 grams by mouth daily. A dose of 50 grams of flaxseeds may be equal to 250 grams of flaxseed flour. A dose of flaxseed that has been used for stomach or abdominal discomfort is 1 tablespoon of whole or bruised seed mixed with 150 milliliters (about 2/3 cup) of liquid, taken by mouth 2-3 times a day. As a laxative, 2-3 tablespoons of bulk seed mixed in 10 times the amount of water has been used. Human studies report that doses of 45 grams daily have laxative effects. For lupus nephritis, 30 grams of flaxseed daily has been studied. For menopausal symptoms, 40 grams of flaxseed daily has been studied.
Flaxseed Liquid : Whole or bruised (not ground) flaxseed can be mixed with liquid and taken by mouth. Generally, one tablespoon in this form is mixed with 6 to 12 ounces of liquid and taken by mouth up to three times a day. Some studies use doses of soluble flaxseed mucilage/fiber as high as 60 to 80 grams per kilogram (1 kilogram equals 2.2 pounds) of the person's weight. These liquid forms of flaxseed should not be confused with preparations of flaxseed oil.
Leaf : There is not enough scientific information to recommend the use of flaxseed leaves for any medical condition.
In Foods : At high temperatures, for example when cooking, flaxseed oil and powder/flour will break down. Reports show that eating four eggs per day from chickens fed flaxseed can increase the levels of total omega-3 fatty acids in the blood. Long-term effects are not clear.
Applied to the skin (flaxseed poultice) : Anecdotally, 30 to 100 grams of flaxseed flour can be mixed with warm or hot water to form a moist compress and can be used up to three times a day. It is not clear how long a flaxseed poultice should be used.
Applied to the eye (flaxseed) : Flaxseeds are historically used for removing debris from the eye. A single whole flaxseed is placed under the eyelid, allowing the debris and mucus to collect around it and thereby to allow removal. This process may be unsafe. Seek the help of a healthcare professional for removal of eye debris.
Children (younger than 18 years)
Not enough information is available to advise use of flaxseed or flaxseed oil in children.
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
People with known allergy to flaxseed, flaxseed oil, or any other members of the Linaceae plant family or Linum genus plant family should avoid flaxseed products. Workers are reported to have developed allergy-like reactions after inhaling flaxseed powder. Two reports describe adults with possible allergic reactions, whose symptoms include itching, hives, eye watering, nasal congestion, sneezing, nausea, abdominal pain, diarrhea, and mild shortness of breath. In these reports, multiple symptoms developed within minutes of taking a spoonful of linseed oil (from flaxseed) by mouth or eating multigrain bread. Allergy tests show that both people were allergic to flaxseed.
Side Effects and Warnings
There are few studies of flaxseed safety in humans. Flaxseed and flaxseed oil supplements do appear to be well tolerated in the available research, and there is long-standing historical use of flaxseed products without many reports of side effects. However, unripe flaxseed pods are believed to be poisonous and should not be eaten. Raw flaxseed or flaxseed plant may increase blood levels of cyanide, a toxic chemical (this effect has not been reported when flaxseed supplements are taken at recommended doses). Do not apply flaxseed or flaxseed oil to open wounds or broken skin.
Based on animal studies, overdose of flaxseed may cause shortness of breath, rapid breathing, weakness, or difficulty walking, and may cause seizures or paralysis. Theoretically, flaxseed ( not flaxseed oil) may increase the risk of cell damage from a reaction called oxidative stress. Studies report conflicting results in this area. Based on one study, flaxseed or flaxseed oil taken by mouth may cause mania or hypomania in people with bipolar disorder. In theory, the laxative effects of flaxseed ( not flaxseed oil) may cause diarrhea, increased number of bowel movements, and abdominal discomfort. Laxative effects are reported in several studies of people taking flaxseed or omega-3 acids. Large amounts of flaxseed by mouth may cause the intestines to stop moving (ileus). People with diarrhea, irritable bowel syndrome, diverticulitis, or inflammatory bowel disease (Crohn's disease or ulcerative colitis) should avoid flaxseed due to its possible laxative effects. Nausea, vomiting, and abdominal pain are reported in two individuals shortly after taking flaxseed products by mouth; these reactions may have been caused by allergy.
Taking a large amount of flaxseed ( not flaxseed oil) by mouth may cause obstruction of the intestines, especially when flaxseed is taken with too little fluid. It is recommended that the amount of seed be taken with ten times that amount of water or other liquid. People with narrowing of the esophagus or intestine, ileus, or bowel obstruction should avoid flaxseed ( not flaxseed oil). Individuals with high blood triglycerides should avoid flaxseed and flaxseed oil due to unclear effects on triglyceride levels in animal research. People with diabetes should use caution if taking flaxseed products by mouth, as the omega-3 fatty acids in flaxseed and flaxseed oil may increase blood sugar levels. This increase is reported in one study of adults with type 2 diabetes who were treated with omega-3 fatty acids for one month, but the effect is not reported in another study of people taking flaxseed (50 grams) by mouth.
One study reports that the menstrual period may be altered in women who take 10 grams of flaxseed powder by mouth daily. Due to the possible estrogen-like effects of flaxseed ( not flaxseed oil), it should be used cautiously in women with hormone sensitive conditions such as endometriosis, polycystic ovary syndrome, uterine fibroids, or cancer of the breast, uterus, or ovary. Some natural medicine textbooks advise caution in patients with hypothyroidism, although little scientific information is available in this area. Flaxseed and flaxseed oil may increase the risk of bleeding, based on early studies that show decreased clotting of blood. In human studies, people taking alpha-linolenic acid, a substance present in flaxseed, have bled longer in laboratory tests, but dangerous bleeding problems have not been reported in the available scientific literature. Caution is advised in patients with bleeding disorders, in people taking drugs that increase the risk of bleeding, and in people planning to undergo medical, surgical, or dental procedures. Dosing of blood-thinning medications may need to be adjusted. In animal studies, flaxseed has increased the number of red blood cells.
Several studies in humans report an increased risk of prostate cancer in men taking alpha-linolenic acid (which is present in flaxseed) by mouth. One small study of men with prostate cancer reports that flaxseed supplements do not increase prostate specific antigen (PSA) levels. Until more information is available, men with prostate cancer or at risk for prostate cancer should avoided flaxseed and alpha-linolenic acid supplements.
Pregnancy & Breastfeeding
The use of flaxseed or flaxseed oil during pregnancy and breastfeeding is not recommended. Animal studies show possible harmful effects, and there is little information in humans. Flaxseed may stimulate menstruation or have other hormonal effects and could be harmful to pregnancy.
References
1. 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.
2. 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.
3. Dabrosin C, Chen J, Wang L, et al. Flaxseed inhibits metastasis and decreases extracellular vascular endothelial growth factor in human breast cancer xenografts. Cancer Lett 2002;185(1):31-37.
4. 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.
5. Endoh D, Okui T, Ozawa S, et al. Protective effect of a lignan-containing flaxseed extract against CCl(4)-induced hepatic injury. J Vet Med Sci 2002;64(9):761-765.
6. Gross PE, Li T, Theriault M, et al. Effects of dietary flaxseed in women with cyclic mastalgia. Breast Cancer Res Treat 2000;64:49.
7. 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.
8. Lemay A, Dodin S, Kadri N, et al. Flaxseed dietary supplement versus hormone replacement therapy in hypercholesterolemic menopausal women. Obstet Gynecol 2002;100(3):495-504.
9. Lin X, Gingrich JR, Bao W, et al. Effect of flaxseed supplementation on prostatic carcinoma in transgenic mice. Urology 2002;60(5):919-924.
10. 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;7(2):112-129.
11. 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):1527-1532.
12. 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;50(6):1668-1671.
13. Newton M, Combest W, Kosier JH, et al. Selected herbal dietary supplements used to manage climacteric (menopausal-type) symptoms. Urol Nurs 2002;22(4):267-272.
14. 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;37(11):1059-1065.
15. 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.
16. 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.
17. Prasad K. Dietary flax seed in prevention of hypercholesterolemic atherosclerosis. Atherosclerosis 1997;132(1):69-76.
18. 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.
19. 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;56(2):157-165.
20. 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.
January 01, 2004 
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