Flax is a food and fiber crop that grows in Europe, Asia, and the Mediterranean. Flaxseeds are the golden yellow to reddish brown seeds of flax. These seeds contain phytoestrogens, which are similar to the hormone estrogen, as well as soluble fiber and oil. Flaxseed oil contains the essential omega-3 fatty acid alpha-linolenic acid (ALA). Flaxseed has been eaten as a food or used as a medicine since 5000 BC.
People use flaxseed by mouth for constipation, colon damage due to overuse of laxatives, diarrhea, inflammation of the lining of the large intestine (diverticulitis), irritable bowel syndrome (IBS) or irritable colon, sores in the lining of the large intestine (ulcerative colitis), inflammation of the lining of the stomach (gastritis), and inflammation of the small intestine (enteritis).
People also take flaxseed by mouth used for disorders of the heart and blood vessels, including heart disease, high triglyceride levels, high cholesterol, "hardening of the arteries" (atherosclerosis), high blood pressure, coronary artery disease, and metabolic syndrome.
Flaxseed is also taken by mouth for acne, attention deficit-hyperactivity disorder (ADHD), kidney problems in people with a disease called systemic lupus erythematosus (SLE), liver disease, symptoms of menopause, breast pain, diabetes, prediabetes, obesity and weight loss, HIV/AIDS, depression, malaria, rheumatoid arthritis, sore throat, upper respiratory tract infections (URTI), and cough, bladder inflammation, enlarged prostate, osteoporosis, and to protect against breast cancer, endometrial cancer, lung cancer, colon cancer, and prostate cancer. It is also taken by mouth to prevent problems associated with hemodialysis treatment.
Flaxseed is sometimes applied to the skin for acne, burns, boils, eczema, psoriasis, and to soothe inflammation.
Flaxseed is used in the eye to help remove debris from the eye.
Natural Medicines rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The effectiveness ratings for Flaxseed are as follows:
Possibly Ineffective for...
Insufficient Evidence to Rate Effectiveness for...
More evidence is needed to rate of flaxseed for these uses.
Flaxseed is a good source of dietary fiber and omega-3 fatty acids. The fiber in flaxseed is found primarily in the seed coat. Taken before a meal, flaxseed fiber seems to make people feel less hungry, so that they might eat less food. Researchers believe this fiber binds with cholesterol in the intestine and prevents it from being absorbed. Flaxseed also seems to make platelets, the blood cells involved in clotting, less sticky. Overall, flaxseed's effects on cholesterol and blood clotting may lower the risk of "hardening of the arteries" (atherosclerosis).
Flaxseed is sometimes tried for cancer because it is broken down by the body into chemicals called "lignans". Lignans are similar to the female hormone estrogen - so similar, in fact, that they compete with estrogen for a part in certain chemical reactions. As a result, natural estrogens seem to become less powerful in the body. Some researchers believe that lignans may be able to slow down the progress of certain breast cancers and other types of cancers that need estrogen to thrive.
For systemic lupus erythematosus (SLE), flaxseed is thought to improve kidney function by decreasing the thickness of blood, reducing cholesterol levels, and reducing swelling.
Flaxseed is LIKELY SAFE for most adults when taken by mouth appropriately. Adding flaxseed to the diet might increase the number of bowel movements each day. It might also cause gastrointestinal (GI) side effects such as bloating, gas, abdominal pain, constipation, diarrhea, stomachache, and nausea. Higher doses are likely to cause more GI side effects.
There is some concern that taking large amounts of flaxseed could block the intestines due to the bulk-forming laxative effects of flaxseed. Flaxseed should be taken with plenty of water to prevent this from happening.
Taking flaxseed extracts that contain lignans in concentrated form is POSSIBLY SAFE. Lignans are the chemicals in flaxseed that are thought to be responsible for many of the effects. Some clinical research shows that a specific flaxseed lignan extract (Flax Essence, Jarrow Formulas) can be safely used for up to 12 weeks. Other research shows that other flaxseed extracts can be used safely for up to 6 months.
Products that contain partially defatted flaxseed, which is flaxseed with less alpha-linolenic acid content, are available. Some men choose these products because they have heard that alpha-linolenic acid might raise their risk of getting prostate cancer. It's important to remember that the source of the alpha-linolenic acid is key. Alpha-linolenic acid from dairy and meat sources has been positively associated with prostate cancer. However, alpha-linolenic acid from plant sources, such as flaxseed, does not seem to affect prostate cancer risk. Men should not worry about getting alpha-linoleic acid from flaxseed. On the other hand, there is a concern that partially defatted flaxseed might raise triglyceride levels too much. Triglycerides are a type of blood fat.
Taking raw or unripe flaxseed by mouth is POSSIBLY UNSAFE. Flaxseed in these forms is thought to be poisonous.
Pregnancy and breast-feeding: Taking flaxseed by mouth during pregnancy is POSSIBLY UNSAFE. Flaxseed can act like the hormone estrogen. Some healthcare providers worry that this might harm the pregnancy, although to date there is no reliable clinical evidence about the effects of flaxseed on pregnancy outcomes. There is not enough reliable information about the safety of taking flaxseed if you are breast feeding. Stay on the safe side and avoid use.
Bleeding disorders: Flaxseed might slow clotting. This raises the concern that it could increase the risk of bleeding in people with bleeding disorders. Don't use it, if you have a bleeding disorder.
Diabetes: There is some evidence that flaxseed can lower blood sugar levels and might increase the blood sugar-lowering effects of some medicines used for diabetes. There is a concern that blood sugar could drop too low. If you have diabetes and use flaxseed, monitor your blood sugar levels closely.
Gastrointestinal (GI) obstruction: People with a bowel obstruction, a narrowed esophagus (the tube between the throat and the stomach), or an inflamed (swollen) intestine should avoid flaxseed. The high fiber content of flaxseed might make the obstruction worse.
Hormone-sensitive cancers or conditions: Because flaxseed might act somewhat like the hormone estrogen, there is some concern that flaxseed might make hormone-sensitive conditions worse. Some of these conditions include breast, uterine, and ovarian cancer; endometriosis; and uterine fibroids. However, some early laboratory and animal research suggests that flaxseed might actually oppose estrogen and might be protective against hormone-dependent cancer. Still, until more is known, avoid excessive use of flaxseed if you have a hormone-sensitive condition.
High blood pressure (hypertension): Flaxseeds might lower diastolic blood pressure. Theoretically, taking flaxseeds might cause blood pressure to become too low in individuals with high blood pressure who are taking blood pressure-lowering medication.
High triglyceride levels (hypertriglyceridemia): Partially defatted flaxseed (flaxseed with less alpha linolenic acid content) might increase triglyceride levels. If your triglyceride levels are too high, don't take flaxseed.
Low blood pressure (hypotension): Flaxseeds might lower diastolic blood pressure. Theoretically, taking flaxseeds might cause blood pressure to become too low in individuals with low blood pressure.
Interaction Rating = Moderate Be cautious with this combination.
Talk with your health provider.
There is some evidence that flaxseed might interfere with the body's ability to take in and use acetaminophen. It's not known, though, whether this interaction is important.
Bacteria in the intestine convert some of the chemicals in flaxseed into lignans, which are thought to be responsible for many of the possible benefits of flaxseed. However, because antibiotics kill these bacteria, lignans might not be formed as usual. This might alter the effects of flaxseed.
Flaxseed can act like the female hormone estrogen. It can compete with estrogens that are included in birth control pills and hormone replacement treatments. Healthcare providers are concerned that flaxseed might make these estrogen-containing drugs less effective.
There is some evidence that flaxseed might interfere with the body's ability to take in and use furosemide. It's not known, though, whether this interaction is important.
There is some evidence that flaxseed might interfere with the body's ability to take in and use ketoprofen. It's not known, though, whether this interaction is important.
Some evidence suggests that flaxseed can lower blood sugar levels. Diabetes medications are also used to lower blood sugar. Taking flaxseed along with diabetes medications might cause your blood sugar to become too low. Monitor your blood sugar closely. The dose of your diabetes medication might need to be changed.
Some medications used for diabetes include glimepiride (Amaryl), glyburide (DiaBeta, Glynase PresTab, Micronase), insulin, metformin (Glucophage), pioglitazone (Actos), rosiglitazone (Avandia), chlorpropamide (Diabinese), glipizide (Glucotrol), tolbutamide (Orinase), and others.
Using flaxseed with drugs that lower blood pressure might increase the effects of these drugs and may lower blood pressure too much.
Some medications for high blood pressure include captopril (Capoten), enalapril (Vasotec), losartan (Cozaar), valsartan (Diovan), diltiazem (Cardizem), amlodipine (Norvasc), hydrochlorothiazide (HydroDIURIL), furosemide (Lasix), and many others.
Flaxseed can act like a laxative. There is some concern that it might interfere with the body's ability to absorb medications taken by mouth because it might sweep them out of the digestive tract too quickly. To avoid this problem, take medications an hour before or two hours after taking flaxseed.
Flaxseed might slow blood clotting. Taking flaxseed along with medications that also slow clotting might increase the chances of bruising and bleeding.
Some medications that slow blood clotting include aspirin, clopidogrel (Plavix), diclofenac (Voltaren, Cataflam, others), ibuprofen (Advil, Motrin, others), naproxen (Anaprox, Naprosyn, others), dalteparin (Fragmin), enoxaparin (Lovenox), heparin, ticlopidine (Ticlid), warfarin (Coumadin), and others.
There is some evidence that flaxseed might interfere with the body's ability to take in and use metoprolol. It's not known, though, if this interaction is important.
Flaxseed might lower blood sugar. If it is taken along with other herbs and supplements that might lower blood sugar, blood sugar might become too low in some people. Some herbs and supplements that might lower blood sugar include alpha-lipoic acid, bitter melon, chromium, devil's claw, fenugreek, garlic, guar gum, horse chestnut, Panax ginseng, psyllium, Siberian ginseng, and others.
Flaxseed can increase the amount of time it takes for blood to clot. Taking flaxseed along with other herbs and supplements that slow blood clotting might increase the risk of bleeding and bruising in some people. Some of these herbs include angelica, clove, danshen, garlic, ginger, ginkgo, Panax ginseng, and others.
There are no known interactions with foods.
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