Flaxseed (also called linseed) comes from the flax plant (Linum usitatissimum), which belongs to the Linaceae plant family. The flax plant is a small, single-stemmed annual that grows to about 2 ft (0.6 m) tall and has grayish green leaves and sky-blue flowers. Historically, flax has been cultivated for thousands of years. Linen made from flax has been found in the tombs of Egyptian pharaohs and is referred to in the Bible and in Homer's Odyssey. The Roman naturalist Pliny wrote about the laxative and therapeutic powers of flax in the first century A.D., and many authorities believe it has been used as a folk remedy since ancient times. Flax is believed to be native to Egypt, but its origins are questionable since it has been used widely around the world. It is cultivated in many places, including Europe, South America, Asia, and parts of the United States. Only the seeds (flaxseed) and oil of the flax plant (flaxseed oil) are used medicinally. Linseed oil is the term usually used for the oil found in polishes, varnishes, and paints.
Flaxseed oil is derived from the flax plant's crushed seeds, which resemble common sesame seeds but are darker. The amber oil is very rich in a type of fat called alpha-linolenic acid (ALA), an omega-3 fatty acid that is good for the heart and found in certain plants. High amounts of omega-3 fatty acids are found in fish and smaller amounts are found in green leafy vegetables, soy-derived foods, and nuts. Many doctors consider these acids important for cardiovascular health. Studies suggest that they can lower triglyceride levels and reduce blood pressure. Omega-3 fatty acids may also decrease the risk of heart attacks and strokes by preventing the formation of dangerous blood clots within arteries. In high dosages, the fatty acids may help to alleviate arthritis, though flaxseed products have not yet been shown to be effective for this purpose.
In addition to omega-3 fatty acids, flaxseed products also contain potentially therapeutic chemicals called lignans. Lignans are believed to have antioxidant properties and may also act as phytoestrogens, very weak forms of estrogen found in fruits, vegetables, whole grains, and beans. Unlike human estrogen, phytoestrogens have dual properties: they can mimic the effects of the hormone in some parts of the body while blocking its effects in others. Many herbalists believe that phytoestrogens can be useful in the prevention or treatment of a variety of diseases, including cancer, cardiovascular disease, and osteoporosis. The estrogen-blocking effects of phytoestrogens may be particularly effective at combating certain cancers that depend on hormones, such as cancers of the breast or uterus. Women who consume large amounts of lignans appear to have lower rates of breast cancer. The fact that heart disease and certain cancers occur less frequently in Asian countries is sometimes attributed to a diet rich in plant foods containing phytoestrogens.
While not approved by the United States Food and Drug Administration (FDA), flaxseed products are reputed to have a number of beneficial effects. Flaxseed is sometimes referred to as a nutraceutical, a recently coined term that includes any food or food ingredient thought to confer health benefits, including preventing and treating disease. Several studies, some conducted in people, suggest that flaxseed products (or agents contained in them) may help to keep the heart and cardiovascular system healthy. Flaxseed products may lower cholesterol levels, help control blood pressure, and may reduce the buildup of plaque in arteries. Test tube and rat studies suggest that chemicals in flaxseed may help to prevent or shrink cancerous tumors. Due to its estrogen-like effects, some women use flaxseed oil to ease breast tenderness, alleviate symptoms of premenstrual syndrome (PMS), and help control menopausal symptoms. Flaxseed oil has also been recommended to treat skin conditions, inflammation, and arthritis. It is usually taken internally for all the purposes mentioned above. The oil may be used externally to help the healing of scalds and burns.
More recently, flaxseed has been shown to be beneficial for people suffering from digestive disorders. It is now recommended as an "effective herbal agent" for treating irritable bowel syndrome (IBS).
The link between flaxseed and heart disease has been examined in a number of published studies. One of these studies published in the journal Atherosclerosis in 1997, observed the effects of adding flaxseed to the diet of rabbits with atherosclerosis. Researchers found that flaxseed reduced the development of plaque build-up by almost 50%. The authors concluded that flaxseed may help to prevent heart attacks and strokes related to high cholesterol levels. A study involving several dozen men with mild high blood pressure, which was published in the Journal of Human Hypertension in 1990, suggests that flaxseed oil may slightly lower blood pressure.
Research also suggests that flaxseed products may have potential as cancer fighters. One study, published in Cancer Letters in 1998, investigated how dietary flaxseed affects the development of cancer. Mice were fed a diet supplemented with 2.5%, 5%, or 10% flaxseed for several weeks before and after being injected with cancerous cells. The more flaxseed the mice received,
While the cancer-inhibiting effects of flaxseed have not been thoroughly studied in people, some practitioners of alternative medicine are already recommending the herb as a potential anticancer agent. Prominent herbalists maintain that the lignans found in flaxseed may help to control cancer of the breast or uterus. Some also recommend the herb for the prevention and treatment of endometriosis.
The therapeutic effects of flaxseed are not limited to people, according to some authorities. It is sometimes used as a purgative in horses and sheep. In addition, flaxseed is included in a rapidly expanding list of nutraceutical products for dogs, cats, and other domestic pets.
Flaxseed products are commercially available as whole or ground seeds, gelatin capsules, and oil. Some herbalists recommend adding the ground or whole seeds to the diet to get the maximum benefit from the herb. Whole seeds can be stored in a cool, dry place for up to one year. Crushed seeds should be used immediately or frozen for future use. No standard guidelines have been established on how much of these forms should be consumed. Research subjects have been given as much as 1/4 cup of ground flaxseed per day, but a Canadian nutrition expert suggests that 1–2 tablespoons per day is enough for most adults.
Several nutraceutical companies are marketing a flaxseed ingredient as of 2002. The flaxseed ingredient is a fine-milled flour with 5% lignan content, intended for addition to commercial baked goods, snack foods, cereals, dry pet foods, and similar products.
Capsules can be taken according to package directions. Some herbalists feel that the capsules available are highly processed, contain fewer beneficial properties, and may be an expensive alternative to flaxseed oil.
The optimum daily dosage of flaxseed oil has not been established. Usually, 1 tablespoon daily of the oil can be taken for general health. As a remedy, 1-3 tablespoons may be taken daily based on the person's weight and health needs. Some people consume the oil as an ingredient in salad dressing. The oil is often combined with limewater when used to treat burns and scalds.
Flaxseed products are not known to be harmful when taken in recommended dosages, though it is important to remember that the long-term effects of taking flax-derived remedies (in any amount) have not been studied. Due to lack of sufficient medical study, flaxseed products should be used with caution in children, women who are pregnant or breast-feeding, and people with liver or kidney disease.
Because flaxseed oil tends to become rancid relatively quickly, it should be kept in the refrigerator. While the oil may be added to cooked food, it should not be used during cooking because heat can destroy the effectiveness of the oil.
Persons who are adding ground flaxseed to their diet for its fiber content are advised to start off with small amounts and increase them gradually, and to drink plenty of water. Otherwise the high fiber content of flaxseed can produce intestinal cramping and diarrhea.
Consumers should read the labels of all flaxseed products to insure that the product is for medicinal or nutritional purposes.
When taken in recommended dosages, flaxseed products are not associated with any significant side effects.
Consumers should consult their healthcare professional for information on flaxseed products and interactions with medications and other remedies. More specifically, the omega-3 fatty acids in flaxseed may increase the blood-thinning effects of such medications as aspirin or warfarin. Flaxseed may help a group of medications known as statins (lovastatin, simvastatin, etc.), which are given to lower blood cholesterol, to work more effectively.
Flaxseed appears to reduce the risk of ulcers from high doses of NSAIDs.
In general, flaxseed oil should not be taken at the same time of day as prescription medications or other dietary
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United States Food and Drug Administration (FDA), Center for Food Safety and Applied Nutrition. 5100 Paint Branch Parkway, College Park, MD 20740. (888) SAFEFOOD. <www.cfsan.fda.gov>.
Rebecca J. Frey, PhD