Flaxseed

Flaxseed is the seed from the plant Linum usitatissimum. The seed or the seed oil is used to make medicine. The information on this page concerns medicine made from the SEED only. There is a separate listing for flaxseed OIL.

People use flaxseed for many conditions related to the gastrointestinal (GI) tract, including ongoing 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).

Flaxseed is also used for disorders of the heart and blood vessels, including high cholesterol, “hardening of the arteries” (atherosclerosis), high blood pressure (hypertension), and coronary artery disease.

Flaxseed is also used for acne, attention deficit-hyperactivity disorder (ADHD), kidney problems in people with a disease called systemic lupus erythematosus (SLE), symptoms of menopause, and breast pain. It is also used for diabetes, obesity and weight loss, HIV/AIDS, depression, bladder infections, malaria, and rheumatoid arthritis.

Other uses include treatment of sore throat, upper respiratory tract infections (URTI), and cough.

Some people use flaxseed to lower their risk of getting weak bones (osteoporosis) and to protect against breast cancer, lung cancer, colon cancer, and prostate cancer.

Flaxseed is sometimes applied to the skin for acne, burns, boils, eczema, psoriasis, and to soothe inflammation.

Natural Medicines Comprehensive Database 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:

• Lowering hemoglobin A1c, a measure of average blood sugar level over three months, in people with type 2 diabetes. However, flaxseed doesn’t seem to lower fasting blood sugar, insulin levels, or blood fats in these people.
• Lowering cholesterol levels in people with high cholesterol. Various flaxseed preparations - including ground flaxseed, partially defatted flaxseed, and flaxseed bread and muffins - seem to significantly reduce total cholesterol and the “bad cholesterol,” low-density lipoprotein (LDL) cholesterol, in people with normal cholesterol levels and in men and pre-menopausal women with high cholesterol. But flaxseed doesn’t have much effect on “good cholesterol,” high-density lipoprotein (HDL) cholesterol. Most flaxseed preparations don’t affect triglyceride levels either, but unfortunately partially defatted flaxseed (flaxseed without as much alpha-linolenic acid content) can increase triglycerides by approximately 10%.
• Improving kidney function in people with systemic lupus erythematosus (SLE).
• Relieving mild menopausal symptoms. Taking flaxseed by mouth seems to improve mild menopausal symptoms. But dose is important. Taking 40 mg of flaxseed daily seems to reduce hot flashes and night sweats in women with mild symptoms, but a lower dose of 25 grams per day doesn’t seem to work.

• Breast pain (mastalgia). In one study, eating a flaxseed muffin each day for 3 months significantly reduced breast pain associated with the start of the menstrual cycle. The muffins each contained 25 grams of flaxseed.
• Constipation. Flaxseed is a good source of dietary fiber and this leads people to think that it would be a good laxative. But so far, there hasn’t been any research to test this assumption.
• Prostate cancer. Early research suggests that taking flaxseed and following a low-fat diet can lower prostate-specific antigen (PSA), a marker for prostate cancer, in men who have a precancerous prostate condition. However, in men who have prostate cancer, adding flaxseed to the diet does not lower PSA, but it does seem to lower levels of the hormone testosterone and slow the rate at which cancer cells multiply. More studies are needed.
• Cardiovascular disease.
• Cancer of the colon or rectum.
• Diverticulitis.
• Irritable bowel syndrome (IBS).
• Stomach upset.
• Bladder inflammation.
• Lung cancer.
• Breast cancer.
• Skin irritation.
• Attention deficit-hyperactivity disorder (ADHD).
• Other conditions.

More evidence is needed to rate the effectiveness 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. 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 people. 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.

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.

Don’t eat raw or unripe flaxseed. Flaxseed in these forms is thought to be poisonous.

Special precautions & warnings:

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. The effect of flaxseed on breast-fed infants is unknown at this time. Stay on the safe side, and don’t use flaxseed if you are pregnant or breast-feeding.

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 triglycerides: 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.

Moderate

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.

The following doses have been studied in scientific research:

BY MOUTH:

• For type 2 diabetes: 600 mg of a specific flaxseed lignan extract (Flax Essence, Jarrow Formulas) three times daily, providing 320 mg lignans, for 12 weeks.
• For high cholesterol: Baked goods such as muffins or bread containing flaxseed and ground flaxseed to provide a daily dose of 40-50 grams of flaxseed.
• For improving kidney function in people with systemic lupus erythematosus (SLE): 15 grams of ground flaxseed twice daily with cereal, or tomato or orange juice.
• For improving mild menopausal symptoms: 40 grams of crushed flaxseed or flaxseed in bread daily.
• For lowering hemoglobin A1c in type 2 diabetes: 600 mg of a specific standardized flaxseed lignan extract (Flax Essence, Jarrow Formulas) daily for 12 weeks.

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To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.methodology (http://www.nlm.nih.gov/medlineplus/druginfo/natural/methodology.html).

To see all references for the Flaxseed page, please go to http://www.nlm.nih.gov/medlineplus/druginfo/natural/991.html.

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Page last updated: 27 September 2012