IngredientsLinseed oil, also known as flaxseed oil or flax oil (in its edible form), is a colorless to yellowish oil obtained from the dried, ripened seeds of the flax plant (Linum usitatissimum). Flaxseed (linseed) is a cultivar of the spring flowering annual plant flax (Linum usitatissimum) from the Linaceae family. The terms flaxseed (Linum usitatissimum L.) and linseed are often used interchangeably.
Also known as flaxseed oil, linseed oil is golden yellow, amber, or brown drying oil with a peculiar odor and bland taste. Its chief constituents are glycerides of linolenic, oleic, linoleic, and saturated fatty acids. The drying property is due to the linoleic and linolenic groups. Derivation is from seeds of the flax plant Linum usitatissimum by expression or solvent extraction.
Linseed oil amounts to 40% of its seed weight and is an edible oil in demand as a dietary supplement owing to its several health benefits.
Regular flaxseed oil contains between 57% and 71% polyunsaturated fats (alpha-linolenic acid and linoleic acid). Plant breeders have developed flaxseed with both higher ALA (70%) and very low ALA content (<3%). The USFDA has granted generally recognized as safe (GRAS) status for high-alpha linolenic flaxseed oil.
Flax was first domesticated in approximately 8,000 B.C. in southwest Asia (Turkey, Iran, Jordan, and Syria) and is native to Algeria, Egypt, Tunisia, Greece, Italy, Spain, and Asia Minor. Originally from the Middle East and widespread throughout the Mediterranean basin where its cultures date back to Babylon in 3000 BC, flax (Linum usitatissimum), an annual herbaceous plant with large sky-blue flowers, was already known not only for its fabrics obtained from its fibers but also for the known beneficial properties of its seeds from which an oil is extracted, by cold pressing, for both food and cosmetic use.
Linseed oil has a rich history of medicinal use dating back thousands of years. Ancient civilizations, including the Egyptians and Greeks, recognized its therapeutic potential, utilizing it both as a food and as a remedy for various ailments. Historical texts suggest linseed oil was administered to soothe gastrointestinal discomfort, improve skin health, and alleviate respiratory issues. In traditional European herbal medicine, it was a common ingredient for treating constipation, owing to its gentle laxative effect.
Artists have traditionally used a diverse range of materials as binding media for their pigments. Oil painting was popular in northern Europe from before the 13th century, and analytical evidence suggests that linseed oil was favored, whilst in Italy, where oil painting was introduced in the 15th century, walnut oil was initially preferred. The oils most widely used in western European art are linseed, walnut, and poppy.
Iranian Traditional Medicine (ITM): Linseed oil is a well-known and frequently-used medicine in Iranian traditional medicine (ITM). According to the most famous and reliable ITM books, i.e. Avicenna's Canon of Medicine and Liber Continens of Rhazes, linseed oil can be used as an analgesic and anti-fibrosis drug.
In parts of Europe, linseed oil is traditionally eaten with potatoes and quark. Its emollient properties made it a favored remedy for dry, irritated skin and scalp conditions, often being applied topically or included in healing ointments.
It is primarily used for direct consumption or as a salad oil and as an ingredient in traditional medicine. Every part of the linseed plant is utilized commercially, either directly or after processing. The shell yields good quality fiber having high mechanical properties and low density; the seed provides oil rich in omega-3, digestible proteins, and lignans, and is also used to manufacture paints, varnishes, linoleum, oilcloths, printing inks, soaps, and numerous other products.
The seed oil of Linum usitatissimum is enriched in α-linolenic acid (ALA) (18:3cis∆9,12,15). Flaxseed oil contains a rich source of polyunsaturated fatty acids such as α-linolenic acid (ALA; ~50%), oleic acid (~20%), and linoleic acid (~15%). A typical fatty acid profile of cold-pressed oil includes the following: not less than 50% C18:3 alpha-linolenic acid, plus 3–8% C16:0 palmitic acid, 2–8% C18:0 stearic acid, 11–24% C18:1 oleic acid, and 11–24% C18:2 linoleic acid.
Flaxseed oil provides alpha-linolenic acid (ALA), a plant-based omega-3 that converts inefficiently to EPA and DHA, offering a vegetarian alternative but with less robust clinical evidence than marine omega-3 sources. The primary omega-3 fatty acid in flaxseed oil is ALA, which typically comprises 50–60% of the oil's total fatty acid content. ALA is classified as an essential fatty acid, meaning the human body cannot synthesise it and must obtain it through dietary sources. Unlike marine-based omega-3 supplements that contain eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), flaxseed oil provides exclusively plant-based omega-3.
ALA is metabolized to eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) by desaturases and elongases in humans. The conversion of ALA to EPA and DHA is limited, and these long-chain n−3 polyunsaturated fatty acids (PUFAs) are mainly provided from dietary sources such as fish and seafood. Some estimates hold that only 5–10% and 2–5% of ALA in healthy adults is converted to EPA and DHA, respectively, while others suggest that humans convert less than 5% of ALA to EPA or DHA.
Concurrent administration of linoleic acid (LA) in the diet will reduce ALA accumulation because there is competition among the enzymes involved in the elongation and desaturation of LA and ALA. A ratio of LA to ALA of 4:1 or lower has been shown to be optimal for the elongation of 11 g ALA to 1 g long-chain ω-3 PUFA. The bioavailability of ALA is dependent on the type of flax ingested: ALA has greater bioavailability in oil than in milled seed, and has greater bioavailability in milled seed than in whole seed.
Flaxseed is particularly the richest known source of lignans (9–30 mg per g), with lignan production at 75–800 times that of other oil seeds, cereals, legumes, and fruit and vegetables. Secoisolariciresinol diglucoside (SDG, MW 686.7) is a phytochemical and antioxidant that acts as a precursor of mammalian lignans and a phytoestrogen.
The most prevalent lignan, SDG, is consumed with linseed and converted into mammalian lignans, enterodiol (END) and enterolactone (ENL), by the gut microbiota. SDG is known to have therapeutic properties including antioxidant, anticancerous, anti-inflammatory, modulation of gene expression, anti-diabetic, estrogenic, and anti-estrogenic activity. Despite a large number of bioactivities, strong evidence for the underlying mechanisms for most of these properties is still incomplete.
It is important to note that SDG is concentrated primarily in the seed meal rather than the expressed oil itself. Along with α-linolenic acid, lignans (mainly SDG) have made flaxseed derivatives (flax oil and lignan extracts) important sources of functional food or nutraceutical ingredients. The principal lignan precursor found in flaxseed is secoisolariciresinol diglucoside (SDG). Its average content in 100 g of flaxseed is 610–1300 mg.
Linusorbs included in the cyclolinopeptides are a component of flaxseed responsible for anti-inflammatory properties. Ratan et al. evaluated the effects of a linusorb mixture on inflammation. In their study, several in vitro and in vivo analyses with animal inflammation models were conducted. The authors observed that a linusorb mixture inhibited nitric oxide (NO) production, the cell shape changed, and the inflammatory gene was expressed in stimulated RAW264.7 cells through the direct targeting of Src and Syk in the NF-κB pathway. This evidence is currently limited to preclinical studies.
In addition to linolenic and linoleic acids, lignans, cyclic peptides, polysaccharides, alkaloids, cyanogenic glycosides, and cadmium are among the numerous physiologically active substances and elements that concentrate in flaxseed. Linseed is also high in lignans, soluble and insoluble fibres, cyclic peptides, and a variety of minerals. Among the phenolic compounds, extraction of flaxseed with aqueous alcohol yields a solution containing SDG in a polymer with phenylpropanoids and hydroxymethylglutaric acid, referred to as flaxseed lignan complex (FLC).
Linseed oil plays an anti-inflammatory role when used by different routes of administration in animal models. Its inhibition of prostaglandin E₂, leukotriene B₄, histamine, and bradykinin can make it a potent anti-inflammatory agent against distinct phases of inflammation, comparable with standard aspirin.
The analgesic activity of linseed oil appears to be peripherally mediated. Analgesic activity of linseed oil may be due to a combination of its inhibitory effects on prostaglandin, histamine, bradykinin, and acetylcholine.
ALA, as an omega-3 fatty acid, provides health benefits such as developing the brain and nervous system in infants, preventing cardiovascular diseases and immune response disorders, and reducing cholesterol levels. ALA also acts as the precursor of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for humans.
Flaxseed is one of the richest sources of the plant-based ω-3 fatty acid, alpha-linolenic acid (ALA). Based on the results of clinical trials, epidemiological investigations, and experimental studies, ingestion of ALA has been suggested to have a positive impact on CVD. Because of its high ALA content, the use of flaxseed has been advocated to combat CVD.
Lipid profiles: Several clinical trials have investigated the effects of flaxseed and flaxseed-derived products (flaxseed oil or lignans) on blood lipids; however, the findings have been inconsistent. Overall, 1,539 subjects were randomly assigned in these trials, and 1,381 (89.7%) participants completed the studies. Flaxseed significantly reduced circulating total and LDL-cholesterol concentrations, but the changes were dependent on the type of intervention, sex, and initial lipid profiles of the subjects.
Lipoprotein(a): An elevated concentration of plasma lipoprotein(a) (Lp[a]) is a risk factor for CAD, cerebrovascular disease, atherosclerosis, thrombosis, and stroke. In a recent double-blinded, randomized, controlled clinical trial, Bloedon et al. demonstrated that 40 g/day of ground flaxseed reduced Lp(a) by 14% after 10 weeks of supplementation. Similarly, Arjmandi et al. reported that 38 g/day of whole flaxseed lowered Lp(a) by 7.4% in postmenopausal women after six weeks of treatment. These findings relate to ground whole flaxseed, not to the oil fraction alone.
ALA bioconversion and plasma EPA: Daily supplementation with 3 g of ALA was studied on the plasma concentration of long-chain (n-3) fatty acids in a predominantly African-American population with chronic illness. In a randomized, double-blind trial, 56 participants were given 3 g ALA/day from flaxseed oil capsules (n=31) or olive oil placebo capsules (n=25). Plasma EPA levels at 12 weeks in the flaxseed oil group increased by 60%; plasma docosapentaenoic acid (DPA) levels in the flaxseed oil group increased by 25%. Plasma DHA levels did not change in either group.
Vascular function: In a double-blind randomized, placebo-controlled parallel study, 59 overweight and obese adults with high-normal blood pressure or mild (stage I) hypertension consumed daily either 10 g of refined cold-pressed flaxseed oil (providing 4.7 g ALA) or 10 g of high-oleic sunflower (control) oil for 12 weeks. As compared with the control, intake of flaxseed oil did not change brachial artery flow-mediated vasodilation, carotid-to-femoral pulse wave velocity, retinal microvascular calibers, or plasma markers of microvascular endothelial function.
Blood pressure (meta-analytic evidence): A systematic review and meta-analysis of randomized clinical trials (RCTs) was conducted to elucidate the overall effects of flaxseed oil consumption on blood pressure in patients with metabolic syndrome and related disorders. PubMed, Scopus, Cochrane Library, and ISI Web of Science databases were systematically searched until March 31, 2020. Weighted mean difference was pooled using a random-effects model. Meta-analysis of five trials (6 arms) showed significant reductions in systolic blood pressure (WMD: −3.86 mmHg, 95% CI: −7.59 to −0.13, p = 0.04).
Evidence strength (cardiovascular): Several trials have examined the effect of ALA supplementation on blood lipids, inflammatory markers, and other indicators of cardiovascular health. Trials were mostly of relatively short duration (6–12 weeks) and ALA doses ranged from 1.2 to 3.6 g/d. There was one long-term trial (52 weeks) in which a high ALA dose of 8.8 g/d was given. Studies of ALA in relation to inflammatory markers and glucose metabolism yielded conflicting results. With regard to clinical cardiovascular outcomes, there is observational evidence for a protective effect against nonfatal myocardial infarction. Overall, the cardiovascular evidence for linseed oil specifically (as opposed to whole flaxseed) is promising but mixed, and constrained by study heterogeneity, short intervention durations, and the limited conversion of ALA to the longer-chain omega-3s that have more definitively demonstrated cardiovascular benefit.
Based on a comprehensive evaluation of evidence gradation demonstrating the anti-inflammatory efficacy of flaxseed oil, it can be inferred that flaxseed oil intervention can alleviate the progression of non-communicable chronic diseases or inhibit their development by reducing inflammatory markers. A systematic review with meta-analysis showed that consuming flaxseed products significantly reduced inflammatory cytokine IL-6 (rather than TNF-α) in dyslipidemia patients.
Subgroup analysis revealed that ALA supplementation at a dose of ≥3 g/d from flaxseed and flaxseed oil had a more prominent effect on improving CVD risk profiles.
The anti-inflammatory evidence is partly supported by in vitro and animal mechanistic data. Consumption of ALA-rich flaxseed oil is a possible way to supplement ω-3 polyunsaturated fatty acids, but the beneficial effects to cardiovascular systems are still controversial. Human RCTs showing reductions in circulating CRP or TNF-α have yielded inconsistent results, and this area of evidence must be characterized as preliminary to moderate.
A systematic review and meta-analysis was conducted to determine the impact of flaxseed supplementation in patients with type 2 diabetes (T2DM). Randomized controlled trials were systematically searched until 25 March 2022. A total of 13 studies were included, and the results showed that flaxseed supplementation significantly reduced hemoglobin A1c (HbA1c) in participants with T2DM compared with the control group. In contrast, it had no effects on body weight, body mass index, blood pressure, fasting blood glucose, homeostatic model assessment for insulin resistance, quantitative insulin sensitivity check index, and lipid parameters.
Numerous studies have been conducted on flaxseed, but the results have been inconsistent with respect to its effects on glycemic and lipid profiles, weight loss, and inflammatory markers. Some studies have found positive effects, while others have not. Effects on HbA1c are promising but the absence of significant changes in fasting blood glucose and insulin resistance metrics means this evidence is mixed and requires further investigation, particularly for flaxseed oil as an isolated preparation.
In addition to edible uses, linseed oil is known as an anti-inflammatory, antioxidant, and analgesic oil. Due to these beneficial properties, it is used in several studies on a variety of subjects such as arthritis, dermatologic complaints, breast cancer, and keratoconjunctivitis. The topical use of linseed oil has been approved for a variety of skin disorders. The Brazilian national pharmacopoeia has approved its topical administration in cases with pruritus and in patients with burns.
Two randomized trials have specifically examined linseed oil for carpal tunnel syndrome (CTS). In the first, a randomized clinical trial compared the therapeutic effect of flax seed oil topical gel and hand splint in the treatment of CTS. Forty-nine patients (96 hands) with mild to moderate idiopathic CTS were divided into two groups randomly. One group was treated by topical gel and the other group by hand splint. The intensity of symptoms and function before and after intervention was measured via the Boston Carpal Tunnel Questionnaire. After intervention, ANCOVA showed a significant difference between the symptom and function scores of the two groups. In both cases, recovery was higher in the gel group (P < .001).
In the second trial, a double-blind and randomized clinical study was conducted with 100 patients with 155 hands with carpal tunnel syndrome, conducted under a placebo-controlled design. Linseed oil could play an anti-inflammatory role when used by different routes of administration. Its inhibition of prostaglandin E₂, leukotriene B₄, histamine, and bradykinin can make it a potent anti-inflammatory agent. The topical CTS evidence is promising but preliminary — limited to two small single-centre trials, and findings need independent replication.
Linseed oil is known for its exceptional nutritional value due to the high content of ALA; its anticarcinogenic effect has been established in several experimental and epidemiological studies. As an adjuvant of chemotherapeutic agents, LO and other ALA-rich vegetable oils have been studied in only a handful of studies at the experimental level.
In an animal study, daily oral administration of linseed oil (1, 3, and 10 ml per kg) to rats with Pliss lymphosarcoma and mice with Lewis lung adenocarcinoma for 11–12 days had a statistically significant effect on the dynamics of tumor growth, reducing the intensity of tumor growth and increasing the frequency of complete tumor regressions compared with control. LO showed high antimetastatic activity in the LLC model.
With respect to lignans, although flaxseed possesses beneficial fatty acid composition and high fiber content, the phytoestrogenic, anticarcinogenic, and antiatherogenic effects have been attributed to its lignan content. Moreover, ingested SDG is converted into mammalian lignans, enterodiol (END) and enterolactone (ENL), by the gut microflora enzymes, and these mammalian lignans have been found to negatively correlate with the incidence of breast cancer.
The cancer-related evidence is currently largely preclinical (animal models and cell culture). The lignan associations with reduced cancer risk are based primarily on observational and epidemiological data. No large-scale human RCTs for linseed oil specifically in cancer prevention or treatment have been completed, and no clinical conclusions can be drawn from the current evidence.
The Brazilian national pharmacopoeia has approved its topical administration in cases with pruritus and in patients with burns. Some studies examined the topical usage of this compound in animal models of skin wound healing and in the prevention of peri-ileostomy skin excoriation. No toxicity was reported in such studies.
Some preliminary evidence has emerged for cognitive benefits. Ogawa et al. found that supplementation with flaxseed oil rich in alpha-linolenic acid improves verbal fluency in healthy older adults (Nutrients, 2023;15(6):1499). This is a single study and, while interesting, this evidence must be considered preliminary and requiring replication.
Feeding 10.7 g/d of ALA from flaxseed oil for 4 weeks failed to increase low DHA levels in breast milk of lactating women. Supplementation with ALA or ALA-rich oils leads to an increase in EPA levels and has no consistent effect on DHA or the omega-3 index. This finding has implications for groups whose needs include DHA—such as pregnant and lactating women and developing infants—where marine-sourced omega-3s are considered more effective.
The following dosages are reported from cited studies only and reflect doses used in those specific investigations, not general recommendations:
Stability and storage consideration: The oil extracted from flaxseed is the most sensitive to oxidation. The important thing is to choose unrefined flaxseed oil, which exhibits a longer shelf life due to the presence of antioxidants such as tocopherols and phenolic compounds. Flaxseed oil should be stored refrigerated in an opaque glass container, which prolongs its shelf life for up to 6 months. Flaxseed oil can oxidize even within a week at room temperature and is then unsuitable for consumption.
Raw cold-pressed linseed oil is easily oxidized and rapidly becomes rancid with an unpleasant odor unless refrigerated. Linseed oil is not generally recommended for use in cooking.
Limited amounts of flaxseed (especially flaxseed lignan extract or mucilage) or oral flaxseed oil supplements may be safe for use in the short-term (up to 6 months). Higher doses of flaxseed or flaxseed oil supplements may cause uncomfortable digestive symptoms like bloating, fullness, and diarrhea.
Cyanogenic glycosides are present in linseed. Raw or unripe flaxseeds should not be eaten as they may contain potentially toxic compounds. For some foods, the approach to the cyanogenic risk may be overly conservative due to the delayed and/or incomplete release of cyanide from the cyanogenic glycosides, as was demonstrated for linseed. The expressed oil itself contains negligible levels of cyanogenic glycosides compared with raw seeds, though appropriate processing and avoidance of raw or unripe seed consumption is established guidance.
There are theoretical reasons to suspect that flaxseed or flaxseed oil might interact with other drugs, such as anticoagulant or antiplatelet drugs. Flaxseed oil may have additive effects with anticoagulant medications such as warfarin or DOACs. This concern is plausible given ALA's mild effect on platelet function observed in experimental studies, but definitive human pharmacokinetic interaction data for linseed oil and anticoagulants are currently limited.
The mucilaginous fiber component of whole flaxseed (distinct from the pure expressed oil) has been noted in the literature to potentially slow the absorption of co-administered oral drugs by forming a viscous gel in the gastrointestinal tract. This effect applies primarily to whole seed or ground meal preparations; food-grade oil preparations are less likely to carry the same risk, but separation of linseed oil supplement doses from other oral medications by at least two hours is a commonly practiced precaution.
Some studies examined the topical usage of linseed oil in animal models of skin wound healing and in the prevention of peri-ileostomy skin excoriation. No toxicity was reported in such studies.
The USFDA has granted generally recognized as safe (GRAS) status for high-alpha linolenic flaxseed oil. Currently, flaxseed is cultivated in more than 50 countries, including Canada, the United States, Brazil, India, China, and Ethiopia. Canada is the leading producer and exporter of oil-type flaxseed, producing on average 1,260,000 tons of flaxseed for oil, meal, and fiber, representing 43% of world production.
Health conditions that Linseed oil may help support.
Body systems that Linseed oil may help support.
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