Flaxseed has been used throughout the world for food, medicine, and fiber to make clothes, fishnets, and other products. The ancient Egyptians grew flax thousands of years ago, and it is now found throughout the world.

Flax is a rich source of dietary fiber that can help lower cholesterol levels. Flaxseed oil helps improve cardiovascular health. Long before people knew about the health benefits of flaxseed oil, they used whole and milled flax seeds as a laxative. The laxative effect comes from mucilage.

Flaxseed contains both omega-3 fatty acids and omega-6 fatty acids. Flaxseed is nature's richest storehouse of omega-3 fatty acids. Flaxseed contains more than twice as much omega-3 oil as fish oils, and it costs less than fish oils, ounce for ounce. Omega-3 oil has been shown to reduce the risk of arteriosclerosis. Flaxseed also contains plant nutrients like phytoestrogens. These are natural estrogen-like substances that can lessen the discomfort of menopause.

You can benefit from adding flaxseed to your diet if you have elevated cholesterol, heart disease, high blood pressure, menstrual pain, psoriasis, eczema, or rheumatoid arthritis. Flaxseed may also reduce the itching, swelling, and redness associated with certain skin disorders such as acne.

Flaxseed reduces LDL (low-density lipoprotein) cholesterol (the body's "bad cholesterol") and lowers triglyceride levels. Research shows that flaxseed oil gives much better protection against heart attacks than canola oil or olive oil.

Taking flaxseed may reduce cancer risk. This is because flaxseed contains the richest sources of lignan building blocks, which play a major role in preventing cardiovascular diseases and cancer. New research indicates that the lignans in flaxseed have both short-term and long-term protective effects against colon cancer.

Flax is an annual plant that thrives in deep moist soils rich in sand, silt, and clay. The seeds in the flax plant are filled with flaxseed oil, sometimes called linseed oil. (Note: Commercial-grade linseed oil commonly used in furniture restoration is not meant for human consumption.) The husks of the seeds are rich in mucilage. Both the seed oil and mucilage have many nutritional and therapeutic properties.

Flax products are made from the seeds found inside the fruits. The seeds contain fatty oils called alpha-linolenic acid (ALA) and linoleic acid. ALA is the omega-3 oil in flaxseed. Flax also contains other important substances like lignans, which may protect you against some types of cancer.

You can buy several types of products made from flaxseed. Ripe seeds, linseed cakes, powder, capsules, and flaxseed oil are all available at health food or grocery stores. Flaxseed oil can be purchased in liquid form (to use in preparing food) or as softgels that you can take as a dietary supplement.

Pediatric

• 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 to 12 years): 1 tsp daily of ground flaxseeds or 1 tsp of fresh flaxseed oil for constipation 

Adult

Recommended dose:

• Flaxseed: 1 tbsp whole or bruised seed with 150 mL liquid two to three times per day for gastritis and enteritis. 2 to 3 tbsp bulk seeds taken with 10 times the amount of water as a bulk laxative
• Poultice: 100 g soaked in boiling water for 10 to 15 minutes, strained, placed in cheesecloth and applied
• Decoction (liquid prepared by boiling down herb in water): 15 g of whole seed simmered in 1 cup water for 10 to 15 minutes
• Flaxseed oil: 1 tbsp oil daily, added to foods such as salad dressing

The best way to take flaxseed is to add it to foods like cereal, salads, or yogurt. You should not use flaxseed oil for cooking because heat destroys the healthful fatty acids. If you suffer from constipation, gastritis (stomach inflammation), or enteritis (inflammation of the small intestine), try adding flaxseed products to various dishes. Flaxseed is an excellent source of mucilage, which acts as a laxative. Be sure to always drink enough liquid, especially water, if you eat bruised, milled, or whole flaxseed.

Note: All forms of flax should be stored in a cool, dry place (e.g. refrigerator) once they are opened.

You shouldn't have any side effects if you take the recommended doses of flaxseed or linseed oil. But if you eat a large quantity of flaxseed and don't drink enough water, you might get intestinal upset. If you're pregnant or nursing, you can add flaxseed and flaxseed oil to your diet. But be sure to not take more than the recommended dose and discuss with your health care provider first.

Flaxseed may slow down the absorption of oral medications or other nutrients if taken at the same time; therefore, ingestion of flaxseed several hours before or after other medications may be warranted. Talk to your health care provider before taking flaxseed if you regularly take any prescription or over-the-counter medications.

No noteworthy interactions (positive or negative) between flaxseed and conventional medications are known to have been reported in the literature to date. Please refer to the monograph on alpha-linolenic acid (ALA) for additional information regarding that active ingredient.

Allman MA, Pena MM, Pang D. Supplementation with flaxseed oil versus sunflowerseed oil in healthy young men consuming a low fat diet: effects on platelet composition and function. Eur J Clin Nutr. 1995;49:169–178.

Bierenbuam ML, Reichstein R, Watkins TR. Reducing atherogenic risk in hyperlipemic humans with flax seed supplementation: a preliminary report. J Am Coll Nutr. 1993;12:501–504.

Blumenthal M, ed. The Complete German Commission E Monographs. Therapeutic Guide to Herbal Medicines. Boston, Mass: Integrative Medicine Communications; 1998:47,132.

Brinker F. Herb Contraindications and Drug Interactions. 2nd ed. Sandy, Ore: Eclectic Medical; 1998:71-72.

British Herbal Pharmacopoeia. 4th ed. Dorset, England: British Herbal Medicine Association; 1996.

Clark WF, et al. Flaxseed: a potential treatment of lupus nephritis. Kidney International. 1995;48:475–480.

Cunnane SC, et al. High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans. Br J Nutr. 1993;69:443–453.

Cunnane SC. Nutritional attributes of traditional flaxseed in healthy-young adults. Am J Clin Nutr. 1995;61:62–68.

De Smet P. Adverse Effects of Herbal Drugs. New York, NY: Springer-Verlag; 1997.

De Smet PAGM, et al, eds. Adverse Effects of Herb Drugs 2. Berlin, Germany: Springer-Verlag, 1993.

Denis L, Morton MS, Griffiths K. Diet and its preventive role in prostatic disease. Eur Urol. 1999;35(5–6):377–387.

Grieve M. A Modern Herbal. New York, NY: Dover; 1971:1:309–310.

Gruenwald J. Brendler T, Christof J. PDR for Herbal Medicines. Montvale, NJ: Medical Economics Company; 1998:940–941.

Haggans CJ, Hutchins AM, Olson BA, et al. Effect of flaxseed consumption on urinary estrogen metabolites in postmenopausal women. Nutr Cancer. 1999;33(2):188–195.

McGuffin M, Hobbs C, Upton R, et al, eds. Botanical Safety Handbook. Boca Raton, Fla: CRC Press; 1997.

Prasad K, Mantha S, Muir A, Westcott N. Reduction of hypercholesterolemic arteriosclerosis by CDC-flaxseed with very low alpha-linolenic acid. Arteriosclerosis. 1998;434:367–375.

Prasad K. Dietary flaxseed in prevention of hypercholesterolemic atherosclerosis. Atherosclerosis. 1997;132(1):69–76.

Rozanova IA, Pogozheva AV, Miagkova MA. Effect of antiatherosclerotic diet with polyunsaturated fatty acids omega-3 from linseed oil on dynamics of natural antibodies to bradykinin and angiotensin II in blood serum of patients with cardiovascular diseases [in Russia]. Savitskaia IuA Vopr Pitan. 1998;2:32–34.

Serraino M, Thompson L. The effect of flaxseed supplementation on the initiation and promotional stages of mammary tumorigenesis. Nutr Cancer. 1992;25:153–159.

Sung M, Lautens M, Thompson L. Mammalian lignans inhibit the growth of estrogen-independent human colon tumor cells. Anticancer Research. 1998;1346:1405–1408.

Talom RT, Judd SA, McIntosh DD, et al. High flaxseed (linseed) diet restores endothelial function in the mesenteric arterial bed of spontaneously hypertensive rats. Life Sci. 1999;16:1415–1425.

Thompson L, Richard S, Orcheson L, Seidl M. Flaxseed and its lignan and oil components reduce mammary tumor growth at a late stage of carcinogenesis. Carcinogenesis. 1996;434:1373–1376.

White L, Mavor S. Kids, Herbs, Health. Loveland, Colo: Interweave Press; 1998:31.

Wichtl M, ed. Herbal Drugs and Phytopharmaceuticals. Boca Raton, Fla: CRC Press; 1994.

Yan L, Yee J, Li D, McGuire M, Thompson L. Dietary flaxseed supplementation and experimental metastasis of melanoma cells in mice. Cancer Lett. 1998;61:181–186.