The medicinal parts are the stem as a sterile linen thread, the oil extracted from the seeds, the dry ripe seeds, the linseed cakes and the fresh flowering plant.
Flower and Fruit
The flowers are paniclelike loose cymes on long peduncles in the leaf axils of the upper part of the stem. They have 5 ovate, acuminate, finely ciliate sepals and 5 obovate petals, which are sky blue and longer than the sepals. There are 5 stamens fused at the base and 1 ovary. The fruit is an almost globular, 6- to 8-mm long capsule on an erect or slightly bent stem. The seeds are flat, brown, and glossy.
Leaves, Stem, and Root
The plant is an annual and grows from 20 to 150 cm high. The root is short, fusiform, and light yellow. The stem is unbranched, erect, or ascending in short curves. The leaves are smooth edged, gray-green, sessile, and almost awnlike acuminate.
The plant flowers only in the morning.
The plant is cultivated in temperate and tropical regions the world over.
Flaxseed consists of the dried, ripe seed of the collective variations of Linum usitatissimum as well as its preparations. The various cultivars of Linum usitatissimum are equally acceptable for the indications listed. The plant is cultivated. The ripe seeds are recovered from the capsules by threshing. The oil contained within the seeds is perishable. Processing of the seeds should take place by cold pressing at a temperature below 40º C.
Not to be Confused With
Lolium temulentum and weed seeds.
Flaxseed, Linseed, Lint Bells, Winterlien
Actions & Pharmacology
Mucilages (3-10%, in the epidermis, high swelling capacity): including arabinoxylans, galactans, rhamnogalacturonans
Cyanogenic glycosides (0.05-0.1%): linustatin and neolinustatin (yielding under optimal conditions 30-50 mg HCN per 100 gm)
Fatty oil (30-45%): chief fatty acids linolenic acid (40-70%), linoleic acid (10-25%), oleic acid (13-30%)
Phenylpropane derivatives: including among others, linusitamarine
Flaxseed oil is the richest known source of omega-3 fatty acids and lignans. Omega-3 fatty acids suppress the production of interleukin, tumor necrosis factor (TNF), and leukotriene B4 from monocytes and polymorphonuclear leukocytes. Flaxseed oil appears beneficial in certain aspects of an insulin-resistant metabolic syndrome (Nestel et al, 1997). Whether or not the composition of platelet lipids is changed with intake of flaxseed is controversial. Several studies have indicated that oral administration of flaxseed oil increases blood levels of alpha-linoleic acid (ALA) and eicosapentaenoic acid (Layne et al, 1996; Allman et al, 1995; Cunnane et al, 1993; Kelley et al, 1993).
Flaxseed has laxative effects arising from increased volume and consequent initiation of intestinal peristalsis from stimulation of stretch receptors (Bisset & Wichtl, 1994). Most studies demonstrate an increase in the omega-3 fatty acid eicosapentaenoic acid (EPA) following ingestion of ALA (Caughey et al, 1996). Flaxseed oil is relatively low in saturated fatty acids, comparable to corn, soy, and canola oils. Compared to canola and olive oils, flaxseed oil is low in oleic acid (Johnston, 1995).
Metabolites of ALA and linoleic acid (LA) act as substrates for the formation of the anti-inflammatory eicosanoids, comprising prostaglandins, thromboxanes, and leukotrienes (Gerster, 1998).
Flaxseed's lignans have shown antineoplastic effects based on in vitro and animal research. Regular consumption may reduce the risk of certain cancers. The antitumoral effect is attributed to the lignans (lignans are antimycotic, anti-oxidative and anti-estrogenic). Dietary supplementation of flaxseed reduced mammary tumor size and number in rats. Several studies have shown an inhibitory effect of dietary ALA on tumor growth and incidence in rodent mammary-tumor models, although one study showed no effect and not all evidence is free of inconsistency (Johnston, 1995). Fiber-rich foods in the human diet contain plant lignans, which promote bacterial synthesis of enterodiol and enterolactone (Shultz et al, 1991).
In studies, lowering of serum lipids was similar with ALA and fish-oil supplementation. Prostaglandin precursors did not or were only slightly augmented with ALA supplementation. Coagulation appeared to be inhibited during supplementation with flaxseed and vitamin E. Blood pressure was not affected by ALA.
Flaxseed regulates the digestive system by absorbing up to eight times its own weight in water and helping material to move through the intestines (Johnston & Johnston, 1990). High mucilage content protects mucous membranes. Flaxseed may bind to (theoretically) toxic metabolites produced during digestion and may also reduce bloat.
Inhibition of Cytokines
Inhibition of the cytokine TNF-alpha and interleukin-1 beta (IL-1 beta) is one of the therapeutic goals in treating certain inflammatory disorders, such as rheumatoid arthritis (Caughey et al, 1996).
Metabolic Syndrome (Insulin Resistance Syndrome; Syndrome X)
Flaxseed showed effects on various aspects of this metabolic syndrome, which consists of obesity, dyslipidemia, insulin resistance, and/or hypertension (Nestel et al, 1997).
Omega-3 Fatty Acid Synthesis
Omega-3 fatty acids are essential for synthesis of components of specialized membranes, such as nervous tissues (Goodnight et al, 1982). ALA is a precursor to certain omega-3 fatty acids contained in marine fish oils and interest in its potential as a substrate for synthesis of these substances runs high.
Patients were randomly assigned to daily intake of either a 25 g flaxseed-containing muffin (n=19) or a control (placebo) muffin (n=13). The aim of this randomized, placebo-controlled, double-blind trial was to investigate the effects of dietary flaxseed on tumor biological markers and urinary lignan excretion in postmenopausal patients with newly diagnosed breast cancer. The results suggest that dietary flaxseed has the potential to reduce tumor growth (Thompson et al, 2005).
In a randomized double-blind clinical trial, 56 participants received 3 g/d of ALA (alpha-linolenic acid) derived from flaxseed oil in capsules (n=31) or olive oil containing placebo capsules (n=25) for 26 weeks. Changes in plasma HDL cholesterol, LDL cholesterol, and triglyceride concentrations did not differ between the two treatment groups. Particle size also was not affected. The results showed that ALA does not seem to decrease CVD risk by altering lipoprotein particle or plasma lipoprotein concentration (Harper et al, 2006).
Flaxseed reduced serum LDL cholesterol levels significantly (p< 0.02) compared with sunflower seeds in a double-blind, crossover trial. Both treatments lowered total cholesterol levels compared to baseline but there was no difference between the two; flaxseed alone reduced lipoprotein(a) levels compared to baseline but the difference from sunflower seeds was not significant. HDL cholesterol and triglyceride levels were unaffected by treatment. No weight gain was observed during the study despite an overall increase in caloric intake. Serum estradiol and follicle-stimulating hormone levels were also unaffected (Arjmandi et al, 1998).
Plasma total and LDL cholesterol levels declined significantly (p<0.05) compared to baseline in one double-blind, crossover study. Though total and LDL cholesterol levels were significantly lower (p<0.05) after 2 weeks of flaxseed consumption compared to controls, by 4 weeks the difference was no longer significant. HDL cholesterol and triglyceride levels were not affected. This study also found no effect of flaxseed on glucose tolerance or lipid peroxidation compared to controls (Cunnane et al, 1995).
In a crossover trial, 16 young male subjects consumed a diet supplemented with 4.3 g/d of flaxseed oil following stabilization on a basal diet. After 55 days of intervention the flaxseed-oil diet did not significantly alter serum triglycerides, cholesterol, LDL-C, HDL-C, apoprotein A-I, or apoprotein B compared with the basal diet of natural foods supplemented, as was the flaxseed-oil diet, with 100 IU of alpha-tocopherol twice weekly. (Kelley et al, 1993).
Coronary Heart Disease
Flaxseed oil as well as other plant sources such as canola oil and walnuts are rich sources of the major dietary (n-3) polyunsaturated fatty acid, Alpha-linolenic Acid (ALA). A 2005 review aimed to determine whether intake of ALA from plants is as effective as ingesting long-chain n-3 polyunsaturated fatty acids from seafood sources—which have been shown to reduce the risk of coronary heart disease through various biological mechanisms including reduction of inflammation and improved endothelial cell function. The authors found that evidence from observational, experimental, and clinical studies, including randomized clinical trials, do point to potential effectiveness in the primary and secondary prevention of coronary heart disease with the consumption of 2 to 3 g of ALA daily (Mozaffarian, 2005).
In one study, levels of TNF-alpha and IL-1 beta were decreased by 30% and 31%, respectively, after 4 weeks of use of flaxseed oil in domestic food preparation in healthy male subjects; levels of the eicosanoids thromboxane B(2) decreased by 29% and of prostaglandin E(2) by 30%. A parallel group of healthy males who ate a sunflower oil-based diet evidenced no change in production of TNF-alpha, IL-1 beta, thromboxane B(2), or prostaglandin E(2) (Caughey et al, 1996).
In a randomized study, 22 healthy postmenopausal women consumed a diet containing a muffin enriched with a plant compound (a lignan complex) isolated from Flaxseed— secoisolariciresinol diglucoside (SDG)—hypothesized to be protective to the heart in postmenopausal women as a result of the complex's structural similarity to estrogen. The low-fat muffin provided 500 mg/d of SGD. The 6-week trial was double-blind and placebo-controlled, and included a 6-week washout period followed by a crossover arm in which the participants consumed an identical muffin except for its absence of the contained plant lignan for the next 6 weeks (or vice-versa). Based on plasma and other laboratory tests, as well as ultrasound measurement of endothelial vessels, the authors concluded that daily consumption for 6 weeks of the muffin enriched with the lignan complex had no effect on endothelial function (the health of vessel linings) (Hallund 2006).
There are limitations to the body's ability to convert ALA to the cardioprotective elements eicosapentaenoic acid (EPA) and possibly docosahexaenoic acid (DHA). The results of a randomized, double-blind trial in 49 individuals (Flaxseed Oil to Reduce Intermediate Cardiac Endpoints [FORCE]) indicate that 3 g of Flaxseed oil daily versus placebo increases the level of cardioprotective plasma EPA levels at 12 weeks by 60%, and DPA levels by 25%. In contrast, neither EPA nor DPA levels changed in the placebo group. The participants were predominantly African-American and female, and had chronic illnesses such as hypertension and Type II diabetes. Additional clinical trials with ALA are worth pursuing, the authors conclude (Harper, 2006).
Results of earlier studies using supplementary flaxseed oil to affect changes in levels of long-chain fatty acids had mixed results, some of which may have arisen from differences in intervention time, nutritional status of subjects, and analysis methods (i.e., measurement of total lipids versus phospholipids). Although ALA can undergo desaturation and elongation to synthesize eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in vivo, most studies of dietary flaxseed supplementation demonstrate moderate increases in EPA and docosapentaenoic acid (DPA). No significant increases or decreases in DHA following supplementation with soy or flaxseed oil were noted while levels of ALA increased (Gerster, 1998; Nestel et al, 1997; Kelley et al, 1993).
Insulin Resistance Syndrome
Systemic arterial compliance (elasticity) increased with flaxseed oil supplementation in 12 overweight subjects showing one or more markers for insulin resistance syndrome (comprising obesity, low HDL cholesterol, raised triglyceride levels, hypertension, or glucose intolerance. Insulin response to flaxseed oil exceeded that of either control period (p=0.16) and of Sunola (nonsignificant). These higher plasma insulin values at 30 and 60 minutes with flaxseed indicate some deterioration in insulin sensitivity, which has also been reported with fish oil supplementation; the importance of this is uncertain (Nestel et al, 1997).
To assess the effects of flaxseed incorporation into the diet of healthy menopausal women, 199 women were randomly assigned to consume 40 g flaxseed /d (n=101) or wheat germ placebo (n=98) for 12 months. Dietary supplementation with flaxseed over one year showed favorable, but not clinically significant, effects on blood cholesterol and caused no significant change in bone mineral density or symptoms in healthy menopausal women (Dodin et al, 2005).
Ingestion of ALA produces changes in the composition of platelet lipids with increases in ALA, eicosapentaenoic acid (EPA), and docosapentaenoic acid (DPA), but not in docosahexaenoic acid (DHA). Long-chain n-3 fatty acids appear to inhibit platelet aggregation by decreasing production of the platelet prostaglandin thromboxane A(2), a potent aggregatory eicosanoid, thereby decreasing the tendency to thrombosis. EPA replaces arachidonic acid, disrupting the substrate for production of thromboxane. Ingestion of an ALA-rich, low-fat diet for 23 days by healthy young men more than doubled levels of EPA in subjects taking 40 g per day of flaxseed oil (p<0.05, n=5) while EPA remained unchanged in those taking sunflower seed oil (n=6). As a result, the EPA:arachidonic acid ratio increased in the flaxseed group. The aggregation response induced by collagen decreased in the flaxseed-oil group (p less than 0.05) (Allman et al, 1995).
Neither flaxseed nor safflower oil improved symptoms of rheumatoid arthritis in a double-blind comparison of the nutrients. Patients (n=22) were randomized to receive either 30 g of flaxseed oil (containing 32 ALA) or 30 g of safflower oil (containing 33% LA), each in the form of powder, for 3 months. Despite increases in ALA in the flaxseed oil group, levels of the long-chain metabolites eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) did not increase. The authors cite low serum levels of zinc, as well as a low ALA:LA ratio, in the treatment group as possible reason for absence of change (Nordstrom et al, 1995).
Indications & Usage
Approved by Commission E:
- Inflammation of the skin
Internally, Flax is used for constipation, irritable colon, diverticulitis, colons damaged by laxative abuse, and as mucilage for gastritis and enteritis. A decoction is used for bladder catarrh and inflammation, gastritis.
Externally, Flaxseed is used for removing foreign bodies from the eye. A single Flaxseed is moistened and placed under the eyelid, the foreign body should stick to the mucous secretion of the seed. Flaxseed is also used as a cataplasm for local skin inflammation, and for chronic prostatitis (Green, 1991) and mild rectal inflammation.
Flax is used in India as a tea for coughs, bronchial conditions, urethritis, diarrhea and gonorrhea; externally for skin infections. The seeds are also used in Indian veterinary medicine.
Flaxseed is contraindicated in the presence of ileus (intestinal obstruction) of any origin; stricture of the esophagus and in the gastrointestinal area; acute inflammatory illnesses of the intestine, esophagus, and stomach entrance.
Precautions & Adverse Reactions
No health hazards or side effects are known in conjunction with the proper administration of designated therapeutic dosages and with concomitant administration of sufficient liquid (1:10).
It is recommended that if flaxseed is taken for inflammatory bowel conditions, that the flaxseed be preswollen before use (Bisset & Wichtl, 1994).
Oil contained within the seed is perishable and must be protected not only during processing but also during handling and storing (Johnston & Johnston, 1990). The oil should be kept out of direct light and in refrigeration to preserve it. The oil should never be heated as it becomes mutagenic (Shields et al, 1995).
Due to the considerable caloric content (470 kilocalories per 100 G), overweight people should only use the whole seeds, which, except for swelling of mucilage in the testa, remain intact in the bowel without releasing the fixed oil. Flaxseed differs from other vegetable oils in its high level (45-50%) of ALA.
There is a discussion on the toxic effect of the cyanogenic glycosides in the drug, which may cause prussic acid poisoning in humans. However, neither high single doses nor chronic intake of linseed have caused any signs of poisoning in humans.
Flaxseed contains mucilage and cellulose; therefore, the absorption of other drugs taken simultaneously may be delayed.
The use of large quantities of the drug as a laxative with too little fluid intake can lead to ileus.
Mode of Administration
Internally, the cracked or coarsely ground seed, in which only the cuticle and mucilage epidermis are damaged is used. Linseed gruel and other galenic preparations are also available for internal use. Externally, as linseed meal or linseed expellant.
The absorption of Flaxseed oil is facilitated when taken with food. A 2005 randomized cross-over study in 12 healthy individuals found that diets supplemented with flaxseeds that had been crushed or milled, as opposed to simply left whole, substantially improved the bioavailability of the seeds' healthful enterolignans (Kuijsten, 2005).
- Capsules – 1000 mg, 1300 mg
- Seeds (whole or crushed)
To prepare a demulcent for use in gastritis and enteritis, allow 5 to 10 g of whole seeds to stand in cold water for 20 to 30 minutes, then pour off the liquid (Bisset & Wichtl, 1994).
Constipation – 1 dessertspoon of whole or bruised (not ground) seed with at least 150 mL of liquid 2 to 3 times daily.
Lower Cholesterol – 35 to 50 g daily of the crushed seeds as a fiber supplement. May be incorporated into muffins or breads (Arjmandi et al, 1998).
Decrease platelet aggregation – 1 to 2 tablespoonfuls flaxseed oil daily (Allman et al, 1995).
Gastritis and enteritis – 2 to 4 tablespoons of milled linseed prepared as recommended above (the seeds should not be taken in the dry state, should be pre-hydrated.)
Topical – 30 to 50 g Flaxseed flour for a hot moist cataplasm or compress.
Flaxseed oil must be processed and stored properly. Flaxseed meal is less vulnerable to rancidity when exposed to light and heat than the processed oil. The seeds should be protected from light and stored in a sealed container. The oil should also be protected from light and should be refrigerated.