Flax is probably best known as the raw material for linen. Since ancient times, fabric woven from this common plant fiber has been used for fine burial shrouds and daily clothing. After falling out of favor because of its tendency to wrinkle, linen is enjoying a fashion revival around the world. Now, flax is becoming an increasingly common alternative cash crop in the Midwest.1

But perhaps even more dramatic than that textile comeback has been the recent meteoric popularity of flaxseed for medicinal purposes. High in essential fatty acids, flaxseed—as well as meal and oil derived from it—are touted as effective agents to lower LDL and reduce cardiovascular (CV) risks.2 Well-established as bulk-forming laxatives, these products have also shown promise against mental and neurologic disorders.


Flax is native to the region extending from the eastern Mediterranean to India, and credit for its first cultivation lies in the Fertile Crescent, including ancient Egypt. Despite those distant roots, flax gave rise to the famed fine linens of the British Isles. The plant is the emblem of the Northern Ireland Assembly and was engraved on the reverse of the British £1 coin from 1986 to 1991.

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The flax plant grows to a height of more than five feet and has narrow green leaves. Flowers are pale blue with five petals each, and the fruit is a round, dry capsule containing the familiar glossy brown seeds also known as linseed.2

Flaxseed (Linum usitatissimum) has a long history in folk medicine. Dense in fibrous mucilage, whole seeds promote bowel function3 and were used in topical poultices.2 Though poulticing is no longer a common practice, the theoretic concept of using hyperosmolar compounds to extract toxins from a wound is still sound.

Modern analysis has determined that flaxseed and its oil are rich in antioxidants and polyunsaturated fats. As a result, its CV-protective properties have been vigorously researched. Flaxseed and its derivatives may also have estrogen receptor agonist/antagonist characteristics, making them an attractive subject for breast cancer research.3 

Evidence of effectiveness

The strongest evidence of flaxseed’s benefits confirms it as a bulk-forming laxative. Its role in the safe formation of fibrous bulk has been verified so effectively that the level of evidence has been rated B.3

Rigorous clinical trials are not yet available to test flaxseed’s impact on heart disease, hypertension, and hyperlipidemia, although a content analysis would seem to indicate that positive effects are likely. Without adequate human trials, evidence levels for these conditions drop to C.3

Perhaps even more exciting than the potential CV impact is the discovery that flaxseed oil may have mitigating effects on many mental and neurologic disorders. Multiple trials are under way, but some have already demonstrated improved mood and function in patients with bipolar disorder and schizophrenia.4,5 Though scientists are still a long way from stating that supplementation with high-content polyunsaturated oils (such as flaxseed) will cure these conditions, studies have supported reduced medication and improved overall well-being when supplementation was implemented.

Safety and side effects

People with any type of botanical allergies should proceed with caution, until they determine their tolerance of flax products. Only fully mature, ripe seeds should be consumed. Unripe seeds and/or pods can have a poisonous effect by boosting cyanide levels in the body. If a large quantity of bulk seed product is consumed without sufficient water intake, bowel obstruction can occur.3

Controversy remains about the possibility that the estrogen-receptor agonist action of flax products may increase the potential for prostate cancer. Until further studies clarify this risk, men who consume flax regularly should monitor their prostate-specific antigen levels and be conscientious about routine examinations.

Use of flax products during pregnancy or lactation is not recommended, again because of the anti-estrogenic properties. Women who consume significant quantities of flax daily may also notice a change in their menstrual pattern caused by the same effect.3

Dose, cost, and how supplied

The chief component and active ingredient in flax products is a-linolenic acid (ALA). All dosage routes are oral and should be standardized to contain 58%  ALA.6

In the case of flaxseed oil, remember that it does not contain the fiber found in the seed, but it is the main source of ALA and requires refrigeration.  The recommended oil dose is one to two tablespoons daily.6 The same amount of seeds, preferably ground, is considered a maintenance dose for general antioxidant effect, with the larger amount providing a fiber laxative effect.2

Because ground or whole flaxseeds are readily available and taste good, many people prefer eating them to taking supplements. Easy ways to add flaxseed to your diet include sprinkling ground seeds on cereal or salads and choosing flaxseed oil over other cooking oils. Vegans can avoid eggs in baked goods by substituting a paste made of ground flaxseed and water.2

Flaxseed and flaxseed oil are sold in health food stores, supermarkets, and many pharmacies. Prices vary according to the form the flaxseed product takes, but a one-pound package of whole flaxseed costs less than five dollars.


Whether as a daily supplement or as a food to increase fiber and nutrition in the diet, flaxseed is beneficial and, in most instances, safe. But, as with any dietary change or supplementation, you should tell your health-care provider that you are using flax so it becomes part of your overall health record.

1. Oplinger E, Oekle E, Doll J, et al. Flax. In Alternative Field Crops Manual. St. Paul, Minn.: University of Minnesota, 1989.
2. Fetrow CW, Avila JR. Professional’s Handbook of Complementary & Alternative Medicines. Springhouse, Pa.: Springhouse Corp., 1999:259.
3. Mayo Clinic. Flaxseed and flaxseed oil (Linum usitatissimum).
4. Stoll A, Severus WE, Freeman MP, et al. Omega-3 fatty acids in bipolar disorder: a preliminary double-blind, placebo-controlled trial. Arch Gen Psychiatry. 1999;56:407-412.
5. Arvindakshan M, Ghate M, Rajnekar P, et al. Supplementation with a combination of omega-3 fatty acids and antioxidants (vitamins E and C) improve the outcomes of schizophrenia. Schizophr Res. 2003;62:195-204.
6. Skidmore-Roth L. Mosby’s Handbook of Herbs & Natural Supplements. 3rd ed., St. Louis, Mo: Elsevier Mosby; 2006:450.

All electronic documents accessed November 7, 2008.