Flaxseed or linseed ( Linum usitatissimum L.) is derived from the flax plant, an annual herb believed to have originated in Egypt. The ancient Egyptians used flaxseed for nutritional and medicinal purposes. They also used the fiber contained in the flax plant to make clothes, fishnets, and other products. Throughout history, flaxseed has been primarily used as a laxative. It is high in fiber and a gummy material called mucilage. These substances expand when they come in contact with water, so they add bulk to stool and help it move more quickly through the gastrointestinal tract, thereby acting as a laxative for constipation.
The seeds and oil of the flax plant also contain substances that promote good health. Flaxseed and flaxseed oil are rich in alpha-linolenic acid (ALA), an essential fatty acid that appears to be beneficial for heart disease, inflammatory bowel disease, arthritis, and a variety of other health problems. Other plants that provide ALA include canola (rapeseed), soybean oil, walnuts, and pumpkin seed.
ALA belongs to a group of substances called omega-3 fatty acids. It is important to maintain an appropriate balance of omega-3 and omega-6 (another essential fatty acid) in the diet, as these two substances work together to promote health. Mackerel, salmon, and walnuts are also good sources of omega-3 fatty acids. Most omega-6 fatty acids tend to promote inflammation while omega-3 fatty acids help reduce inflammation. A healthy diet should consist of roughly 2 - 4 times more omega-6 fatty acids than omega-3 fatty acids. The typical American diet tends to contain 14 - 30 times more omega-6 fatty acids than omega-3 fatty acids, and many researchers believe this imbalance is a significant factor in the rising rate of inflammatory disorders in the United States, including heart disease, cancer, and arthritis. Other omega-3 fatty acids include those found in fish oil (docosahexaenoic acid or DHA, and eicosapentaenoic acid or EPA).
ALA can be converted to long-chain omega-3 fatty acids (DHA and EPA) and can therefore be substituted for fish oils. However, EPA and DHA (the fish oils) are more rapidly incorporated into plasma and membrane lipids and produce more rapid effects than does ALA. Only a small amount of ALA is converted to DHA or EPA in the body, so larger quantities of flaxseed oil need to be taken to get the same effects from fish oils. Larger quantities of flaxseed oil may increase the chances of diarrhea and may increase blood sugar levels. One advantage of the consumption of ALA over omega-3 fats from fish is that the problem of insufficient vitamin E intake does not exist with high intake of ALA from plant sources. Generally, if an individual wishes to supplement the diet with an omega-3 fatty acid, fish oil products would be preferred to flaxseed oil.
Studies suggest that flaxseed (both the ALA in the flaxseed oil and the lignans in the seed) may play a role in the prevention and treatment of the following health conditions:
People who follow a Mediterranean diet tend to have higher HDL ("good") cholesterol levels. The Mediterranean diet consists of a healthy balance between omega-3, omega-6, and omega-9 (found in olive oil) fatty acids. It emphasizes whole grains, root and green vegetables, daily intake of fruit, fish and poultry, olive and canola oils, and ALA (from flaxseed, flaxseed oil, and walnuts), along with discouragement of ingestion of red meat and not much use of butter and cream.
Flaxseed and flaxseed oil have been reported to possess cholesterol-lowering properties in laboratory studies. Human studies have used flaxseed products and measured effects on cholesterol, with mixed results. A human study found that dietary flaxseed significantly improved lipid (cholesterol) profile in patients with high cholesterol, and may favorably modify cardiovascular risk factors.
A diet rich in fruits, vegetables, whole grains, nuts or legumes, and ALA-rich foods may substantially reduce the recurrence of heart disease. One of the best ways to help prevent and treat heart disease is to eat a low-fat diet and to replace foods rich in saturated and trans-fat with those that are rich in monounsaturated and polyunsaturated fats (including omega-3 fatty acids from flaxseed). Evidence suggests that people who eat an ALA-rich diet are less likely to suffer a fatal heart attack.
- ALA may reduce heart disease risks through a variety of biological mechanisms, including platelet function (making them less "sticky"), inflammation, blood vessel health, and arrhythmia (irregular heart beat).
- Several human studies also suggest that diets rich in omega-3 fatty acids (including ALA) may lower blood pressure.
Flaxseed was compared to hormone replacement therapy (HRT) in menopausal women. 40 g of flaxseed was reported to be equally effective as HRT for mild menopausal symptoms (hot flashes, mood disturbances, vaginal dryness) and to lower blood sugar levels. However, a few studies report no benefits in reducing menopausal symptoms when using flaxseed oil. Flaxseed was also found to be beneficial in bone health, potentially decreasing the chances of developing osteoporosis.
Lignans from flaxseed
In addition to the important omega-3 fatty acid ALA, flaxseed (not the oil) also contains a group of chemicals called lignans that may protect the body from cancer. Lignans are plant compounds that mimic the action of the natural hormone estrogen. For this reason, lignans are considered phyto (plant) estrogens. Because of their estrogen-like activity, scientists aren't sure whether flaxseed would be harmful or helpful for breast cancer. Several laboratory studies support the use of flaxseed oil in preventing cancer development.
Laboratory studies have reported reduction in breast tumor growth and metastasis (spreading) in rats. A human study has examined the effects of dietary flaxseed in postmenopausal patients with newly diagnosed breast cancer. The authors found that dietary flaxseed may have the potential to reduce tumor growth in patients with breast cancer.
Laboratory studies show that lignans may slow the growth of colon tumor cells and some studies have found that flaxseed may significantly reduce the number of abnormal cell growths (early markers of colon cancer). More research is needed.
Researchers are investigating whether lignans in flaxseed help prevent prostate cancer. In one study that compared 25 men with prostate cancer to the same number of men without the disease, researchers found that men who consumed a low-fat, flaxseed-supplemented diet for 1 month had slower tumor progression than those who did not consume the diet. However, a study of about 47,000 men found that ALA omega-3 fatty acids may stimulate the growth of prostate tumors in men with advanced prostate cancer. The researchers found that men who were suffering from advanced prostate cancer had higher quantities of ALA from nonanimal as well as meat and dairy sources.
Animal studies suggest that lignans from flaxseed may also offer some protection against skin cancer including, possibly, the prevention of metastatic spread of melanoma from the skin to the lungs.
Although further research is needed, preliminary evidence suggests that omega-3 fatty acids may help protect against certain infections and treating a variety of conditions, including ulcers, migraine headaches, attention deficit/hyperactivity disorder, addiction, eating disorders, preterm labor, emphysema, psoriasis, glaucoma, Lyme disease, lupus, and panic attacks.
Flax is an annual plant that thrives in deep moist soils rich in sand, silt, and clay. The small, oval-shaped seeds of the flax plant contain oil (sometimes called linseed oil).
What's It Made Of?
Flaxseed contains several phyto (plant) compounds that may be beneficial in humans, including:
- Fiber (including soluble and insoluble)
- Protein -- approximately 20%
- Essential fatty acids (ALA) -- flaxseed is approximately 35% oil, of which 55% is ALA.
The laxative effect of flaxseed is due to its fiber and mucilage content. As described earlier, phytoestrogens, known as lignans, appear to play a role in the cancer protective effects of this plant. Other health benefits of flaxseed (such as protection from heart disease and arthritis) are likely due to its high concentration of the omega-3 fatty acid ALA.
Flaxseed oil should be refrigerated. Use whole flaxseeds within 24 hours of grinding, otherwise the ingredients lose their activity. Flaxseeds are also available ground in a special mylar package so that the components in the flaxseeds stay active. Ripe seeds, linseed cakes, powder, capsules, and flaxseed oil are all available at health food and grocery stores.
How to Take It
Flaxseed oil may be added to a child's diet to help balance fatty acids. If an infant is breastfed, the mother may ingest oil or fresh ground seed to increase fat content in breast milk. See adult dosage below.
Children (2 - 12 years): 1 teaspoonful (tsp) daily of ground flaxseeds, or 1 tsp of fresh flaxseed oil for constipation.
Flaxseed: Take 1 tablespoonful (tbsp), 2 - 3 times daily or 2 - 4 tbsp, 1 time daily. Grind before eating and take with lots of water.
Flaxseed oil: Take 1 - 2 tablespoonfuls daily, or 1 - 2 capsules daily. Flaxseed oil is often used in a liquid form, which contains approximately 7 g of ALA per 15 mL tbsp, and contains approximately 130 calories.
As a substitute for fish oil, a dose of 7.2 grams of flaxseed is approximately equivalent to 1 gram of fish oil.
The use of herbs is a time-honored approach to strengthening the body and treating disease. Herbs, however, contain components that can trigger side effects and interact with other herbs, supplements, or medications. For these reasons, herbs should be taken with care, under the supervision of a health care provider qualified in the field of botanical medicine.
- Although studies have found that regular consumption of fish (which includes the omega-3 fatty acids EPA and DHA) may reduce the risk of macular degeneration, a recent study including two large groups of men and women found that diets rich in ALA may increase the risk of this disease. Ask your health care provider.
- Flaxseed may slow down the absorption of oral medications or other nutrients if taken at the same time. Therefore, flaxseed should be ingested several hours before, or after medicines or supplements. Talk to your health care provider before taking flaxseed if you regularly take any prescription or nonprescription medications, or dietary supplements.
- People with either diabetes or schizophrenia may lack the ability to convert ALA to EPA and DHA, the forms of omega-3 fatty acids that are generally made from ALA and are more readily used by the body. Therefore, people with these conditions should obtain their omega-3 fatty acids directly from dietary sources rich in EPA and DHA, such as cold water fish (including mackerel, salmon, or whitefish).
- Do not use flaxseed products or ALA if you have diabetes, prostate problems, breast cancer, or schizophrenia without the advice and supervision of a qualified health care provider.
Flaxseed supplements may alter the effects of some prescription and nonprescription medications. If you are currently being treated with any of the following medications, you should not use flaxseed without first talking to your health care provider:
Blood-Thinning Medications -- Omega-3 fatty acids may increase the effects of blood-thinning medications, including aspirin and warfarin. While the combination of aspirin and omega-3 fatty acids may be helpful under certain circumstances (such as heart disease), they should only be taken together under the guidance and supervision of a qualified health care provider.
Diabetic Medications -- If you are taking medicines for diabetes, including insulin, you should only use flaxseed (ALA) under the supervision of a qualified health care provider.
Oral Contraceptives or Hormonal replacement therapy (HRT) -- Flaxseed may alter hormonal levels and alter the effects of oral contraceptives or HRT. Only use flaxseed under the supervision of a qualified health care provider if you are taking hormonal altering medications such as oral contraceptives or HRT.
Other -- Avoid taking flaxseed at the same time of day as medications and other supplements, as it may slow down the absorption of oral medications or other nutrients if taken at the same time. Take the flaxseed either 1 hour before or 2 hours after taking any prescription or nonprescription medicine or dietary supplement.