Flaxseed Oil by NSI - Nutraceutical Sciences Institute

POSSIBLY INEFFECTIVE

• Bipolar disorder. Oral flaxseed oil does not seem to reduce symptoms of bipolar disorder in children. Details: Clinical research in children ages 6-17 years with bipolar disorder shows that taking flaxseed oil, titrated to provide up to 6.5 grams of the flaxseed oil constituent alpha-linolenic acid, daily for 16 weeks does not improve symptoms of mania or depression when compared with placebo (66044).
• Hyperlipidemia. Oral flaxseed oil does not seem to reduce cholesterol levels. Details: Although some evidence from preliminary, low-quality clinical studies disagrees (21698,26466,76696), most clinical research shows that taking flaxseed oil does not reduce cholesterol or triglyceride levels in patients with or without hypercholesterolemia or hypertriglyceridemia (2317,16791,16794,21693,21694,21696,21697,22177,72228,101947)(101954,101956,111062). A meta-analysis of clinical studies evaluating various flaxseed formulations suggests that flaxseed oil consumption may reduce apolipoprotein A levels, but not apolipoprotein B levels, when compared with control groups (108046). A subgroup analysis from another meta-analysis suggests that flaxseed oil may modestly improve levels of high-density lipoprotein cholesterol (108044). It should be noted that most research suggests that flaxseed, the source of flaxseed oil, can improve lipid levels in adults with hyperlipidemia. This difference may be due to lipid lowering components such as lignans, phytic acid, and polyphenols, that are found in flaxseed, but not flaxseed oil. See the Flaxseed monograph for more information.
• Obesity. Oral flaxseed oil does not seem to improve weight loss. Details: A meta-analysis of clinical research in overweight adults shows that flaxseed oil consumption does not reduce body weight, body mass index, or waist circumference when compared with control (96427). This is in contrast to research suggesting that flaxseed, the source of flaxseed oil, can improve weight loss in obese and overweight adults. See the Flaxseed monograph for more information.
• Rheumatoid arthritis (RA). Oral flaxseed oil does not seem to improve symptoms of RA. Details: A small clinical study in patients with RA shows that taking flaxseed oil daily for 3 months does not seem to improve symptoms of pain and stiffness, and has no effect on laboratory measures of RA, such as C-reactive protein and erythrocyte sedimentation rate (ESR), when compared with control (5898).

INSUFFICIENT RELIABLE EVIDENCE to RATE

• Atherosclerosis. Small clinical trials show that taking flaxseed oil has modest benefit on metabolic risk factors in patients with plaque in the coronary artery. Details: Observational research in White adults has found that high dietary intake of linolenic acid, a flaxseed oil constituent, is associated with reduced calcified atherosclerotic plaque in the coronary arteries (12990). However, clinical research has not confirmed this finding. A small clinical trial in patients with coronary artery disease shows that taking flaxseed oil 5 grams in milk containing 1.5% fat reduces triglyceride levels by 14% when compared with the milk alone. However, there was no effect on systolic blood pressure, high-density lipoprotein (HDL) cholesterol, or low-density lipoprotein (LDL) cholesterol (101954). Additionally, another small study in a similar patient population shows that taking flaxseed oil 2 grams daily for 12 weeks has no effect on lipid levels when compared with placebo (101956).
• Attention deficit-hyperactivity disorder (ADHD). Oral flaxseed oil has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: A small clinical trial in children with ADHD shows that taking flaxseed oil, providing 200 mg of alpha-linolenic acid, in combination with vitamin C 25 mg, twice daily can improve measures of attention, impulsivity, restlessness, and self-control when compared to baseline (14443). This finding is limited by the lack of a control group. Furthermore, it is unclear if the benefit is due to flaxseed oil, vitamin C, or the combination.
• Breast cancer. It is unclear if oral flaxseed oil reduces the risk of breast cancer. Details: Population research has found that females with higher levels of the flaxseed oil constituent, alpha-linolenic acid (ALA), in breast adipose tissue have a lower risk of breast cancer. Fatty acid composition of adipose tissue is thought to reflect past dietary intake, so researchers think high intake of ALA might have a cancer protective effect (7168,21689). Flaxseed oil is one source of ALA; it is unclear what effect, if any, flaxseed oil has on breast cancer risk.
• Burns. It is unclear if oral flaxseed oil improves wound healing and health in people with burns. Details: A small clinical trial in patients with mild to moderate burns shows that eating cookies containing flaxseed oil 30 grams and isolated soy protein (ISP) 50 grams daily for 3 weeks improves the rate of wound healing when compared with control cookies. It seems to take at least 3 weeks before this difference is observed. However, there is no significant difference in the rate of wound healing when compared with cookies containing ISP with corn oil (99401). It is possible that the study was underpowered to detect a difference between these two groups.
• Cardiovascular disease (CVD). It is unclear if oral flaxseed oil reduces the risk of CVD. Details: Flaxseed oil is a source of alpha-linolenic acid (ALA). A meta-analysis of observational studies has found that, overall, increasing dietary intake of ALA by 1.2 grams daily is associated with a 20% reduced risk of fatal coronary heart disease in people with existing heart disease (12978). Some research suggests that ALA has a greater impact on coronary heart disease when intake of fish oils is low (12989). It is unknown if flaxseed oil supplements have these same effects. Additionally, it is difficult to separate effects of dietary ALA in these studies from those of other dietary, lifestyle, or drug interventions (12917).
• Carpal tunnel syndrome. It is unclear if topical flaxseed oil reduces carpal tunnel pain. Details: Preliminary clinical research in patients with carpal tunnel syndrome who wear a wrist splint at night shows that applying flaxseed oil 5 drops topically on the palmar wrist twice daily for 4 weeks improves subjective symptom scores by 30%, function scores by 17%, and sensory nerve conduction velocity of the median nerve by about 7% when compared to baseline. Compared to the changes observed for patients in the placebo group, these improvements were significant (25691). It is unclear if this benefit persists long-term or how topical flaxseed oil compares to other standard treatments for carpal tunnel syndrome.
• Chronic kidney disease (CKD). Although there is interest in using oral flaxseed oil for CKD, there is insufficient reliable information about the clinical effects of flaxseed for this condition.
• Cognitive function. It is unclear if oral flaxseed oil improves cognitive function in healthy adults. Details: Clinical research in healthy older Japanese adults with normal cognitive function shows that taking flaxseed oil 3.7 grams daily for 12 weeks modestly improves verbal fluency when compared with taking placebo. However, there was no effect on other measures of cognitive function, including attention, concentration, and memory (111060).
• Diabetes. Oral flaxseed oil may not improve glycemic control in patients with type 2 diabetes. However, there may be some benefit in patients with gestational diabetes. Details: Most clinical research in patients with type 2 diabetes shows that taking flaxseed oil, providing about 1-16 grams of alpha-linolenic acid, daily for up to 6 months does not improve fasting blood glucose, glycated hemoglobin (HbA1C), or insulin resistance when compared with placebo (16792,66065,96428,96431,101956,111062). While taking flaxseed oil does not seem to be beneficial for type 2 diabetes, it might improve outcomes in gestational diabetes. A small clinical study in pregnant patients (24-28 weeks gestation) with gestational diabetes shows that taking flaxseed oil 1 gram twice daily for 6 weeks reduces fasting levels of glucose and insulin and improves insulin resistance when compared with placebo (101957). Another small clinical study in patients with gestational diabetes shows that taking flaxseed oil 1 gram, containing 400 mg of alpha-linolenic acid, along with vitamin E 400 IU daily for 6 weeks reduces blood glucose levels, insulin levels, and insulin resistance and improves beta-cell function when compared with placebo (96432). It is unclear if the findings from this latter study are due to flaxseed oil, vitamin E, or the combination.
• Diabetic foot ulcers. It is unclear if oral flaxseed oil improves the healing of diabetic foot ulcers. Details: One small clinical trial in adults with grade 3 diabetic foot ulcers shows that taking flaxseed oil 1 gram twice daily for 12 weeks in conjunction with intravenous antibiotics for the first 3 weeks reduces ulcer size when compared with placebo (96431).
• Dry eye. Flaxseed oil, both orally and as an eye drop, has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in patients with dry eye shows that taking a specific combination product (TheraTears Nutrition, Advanced Vision Research) containing eicosapentaenoic acid 450 mg, docosahexaenoic acid 300 mg, and flaxseed oil 1000 mg daily for 90 days reduces subjective symptoms of dry eye and might increase tear production when compared with placebo. However, it did not improve meibomian gland secretions or tear evaporation rate when compared with placebo (17523). Eye drops with flaxseed oil have also been tried for dry eye. A clinical study shows that using a specific product (Refresh Optive MEGA-3 Preservative-Free Lubricant Eye Drops, Allergan plc) which contains flaxseed oil and trehalose in addition to other ingredients such as carboxymethylcellulose (CMC) and castor oil twice daily for 90 days improves dry eye symptoms when compared to baseline, but not when compared with the same eye drops formulated without flaxseed oil and trehalose (101953).
• Dry skin. There is conflicting evidence regarding the use of flaxseed oil for dry skin. Details: Some clinical research suggests that taking flaxseed oil 2.2 grams orally in combination with alpha-tocopherol 10 mg daily for 12 weeks does not improve skin hydration when compared with placebo or borage oil in females with dry skin, although the combination seems to improve the sensitivity of dry skin (21908). Other clinical research suggests that taking flaxseed oil 2.2 grams daily for 12 weeks improves skin hydration and roughness when compared with safflower oil (21909).
• Endometrial hyperplasia. It is unclear if oral flaxseed oil reduces endometrial hyperplasia. Details: A small clinical trial in adults with endometrial hyperplasia shows that taking flaxseed oil 1 gram twice daily for 12 weeks does not induce endometrial regression or reduce cholesterol levels when compared with placebo. However, there appears to be a small benefit on fasting plasma glucose and insulin levels (101955).
• Hypertension. Small studies suggest that flaxseed oil may modestly lower blood pressure in some patients. Details: Epidemiological research has found that high dietary intake of linolenic acid, a flaxseed oil constituent, is associated with a reduced risk of developing hypertension (12991). Meta-analyses of small clinical studies in patients with and without hypertension show that receiving flaxseed oil 1.2-30 grams daily for 4-24 weeks reduces systolic and diastolic blood pressure by 0.5 mmHg to 4 mmHg, when compared with control (96426,111063). One meta-analysis limited to small clinical trials in patients with metabolic syndrome, hypercholesterolemia, or hypertension, shows that taking flaxseed oil 25 mL or 2.2 to 9.2 grams daily for 7-12 weeks reduces systolic blood pressure by about 3.9 mmHg; however, there is no effect on diastolic blood pressure (111067). The small size and heterogeneity of the studies included in these meta-analysis limit the validity of these findings. Also, the effect of taking flaxseed oil in patients specifically with hypertension is unclear from this available research. Flaxseed oil has also been evaluated in combination with other oils and dietary interventions, with mixed evidence of benefit. Flaxseed oil 19 grams, providing 10.5 grams of alpha-linolenic acid, seems to reduce blood pressure when combined with walnuts and walnut oil daily for 6 weeks (21905). However, consuming 60 grams of a combination of flaxseed and safflower oils in a 6:4 ratio daily for 4 weeks does not seem to affect blood pressure when compared with baseline (26466).
• Mastalgia. It is unclear if oral flaxseed oil is beneficial in patients with mastalgia. Details: A clinical study in adults with fibrocystic breasts and mastalgia shows that taking flaxseed oil 1000 mg containing 350 mg alpha-linolenic acid twice daily for 2 months reduces pain when compared with baseline, but is no different than taking vitamin E 200 IU daily (105477).
• Metabolic syndrome. It is unclear if oral flaxseed oil is beneficial in patients with metabolic syndrome. Details: A small clinical study in patients with metabolic syndrome shows that taking flaxseed oil 20 mL daily for 7 weeks does not improve coagulation scores based on prothrombin time, partial thromboplastin time, and the international normalized ratio (INR) when compared with sunflower oil (101951).
• Nonalcoholic fatty liver disease (NAFLD). It is unclear if oral flaxseed oil is beneficial in patients with NAFLD. Details: Clinical research in overweight or obese patients with NAFLD shows that taking flaxseed oil 20 grams daily for 12 weeks as part of a hypocaloric diet improves the grade of fatty liver by 41%, compared with 18% in patients taking sunflower oil. There was also a small effect on body mass index, although there was no effect on liver enzymes, glycemic control, or body composition (101952).
• Parkinson disease. Oral flaxseed oil has only been evaluated in combination with other ingredients; its effect when used alone is unclear. Details: One small clinical study in patients with Parkinson disease shows that taking flaxseed oil 1 gram daily plus vitamin E 400 IU daily for 12 weeks improves the Unified Parkinson Disease Rating Scale (UPDRS) total score by 3.3 points, compared to a 4.4-point worsening in the placebo group (96430). However, it is unclear if this change is clinically meaningful. The minimal clinically important improvement in UPDRS total score is 4.3 points, while a moderate improvement ranges from 9 to 17 points (95686). Also, it is not clear if these findings are due to flaxseed oil, vitamin E, or the combination.
• Physical performance. It is unclear if oral flaxseed oil improves physical performance in older adults. Details: A small clinical study in elderly adults without previous exercise training suggests that flaxseed oil containing alpha-linolenic acid does not improve muscle strength when compared with placebo (65937).
• Pneumonia. It is unclear if oral flaxseed oil helps to prevent pneumonia. Details: Epidemiological research has found that increasing dietary alpha-linolenic acid, which occurs in flaxseed oil, is associated with a reduced risk of community-acquired pneumonia (13760). However, this research did not specifically assess the effect of flaxseed oil intake on pneumonia.
• Polycystic ovary syndrome (PCOS). Small clinical studies suggest that oral flaxseed oil might help to improve some markers of PCOS. Details: A small clinical study in patients with PCOS shows that taking flaxseed oil, providing 545 mg of alpha-linolenic acid, for 6 weeks lowers triglycerides but does not affect weight, hormone levels, glycemic control, or cholesterol levels when compared to baseline (21906). This finding is limited by the lack of a control group. Another small clinical study in patients with PCOS shows that taking flaxseed oil, providing 1 gram of omega-3 fatty acids, twice daily in addition to metformin for 12 weeks decreases triglyceride and insulin levels, but does not affect fasting blood glucose, testosterone levels, free androgen index, or total cholesterol when compared with placebo (99402).
• Prostate cancer. Oral flaxseed oil does not seem to be linked to prostate cancer risk. Details: Although some epidemiologic research has found that high dietary intake of alpha-linolenic acid, a constituent of flaxseed oil, is associated with an increased risk for prostate cancer (1334,1337,2558,7823,7147,12978,12961), other research has found no association (12961,15736). Furthermore, it appears that alpha-linolenic acid from plant sources, such as flaxseed or flaxseed oil, does not increase prostate cancer risk (12909).
• Ulcerative colitis. It is unclear if oral flaxseed oil is beneficial in patients with ulcerative colitis. Details: A small open-label clinical study in patients with ulcerative colitis shows that taking flaxseed oil 10 grams daily for 12 weeks seems to modestly reduce inflammatory markers and disease severity and improve quality of life when compared with control (101941). More evidence is needed to rate flaxseed oil for these uses.

(Read more about FLAXSEED OIL)

LIKELY SAFE ...when used orally and appropriately for medicinal purposes, short-term. Flaxseed oil has been used safely in doses up to 2 grams daily for up to 6 months. Higher doses of up to 24 grams daily has been safely used for up to 7 weeks (845,3912,5898,14443,16789,16791,16794,16795,17523,101951,101952,101955).

POSSIBLY SAFE ...when used topically for medicinal purposes, short-term. Flaxseed oil has been used safely on the wrist for up to 4 weeks (25691). ...when used in eye drops twice daily for up to 90 days (101953).

CHILDREN: POSSIBLY SAFE
when used orally and appropriately, short-term. Some evidence suggests that flaxseed oil, providing 200 mg of alpha-linolenic acid, can be safely used in children for up to 3 months (14443).

PREGNANCY: POSSIBLY SAFE
when used orally and appropriately for medicinal purposes, short-term. Although flaxseed oil has been used with apparent safety in clinical research in doses of 1-2 grams daily for up to 6 weeks (96432,101957), some population research has found that consuming flaxseed oil during the second and third trimesters of pregnancy is associated with a four-fold increased risk of premature birth (16797).

LACTATION:
Insufficient reliable information available; avoid using.

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ANTICOAGULANT/ANTIPLATELET DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = High •  Occurrence = Possible •  Level of Evidence = D Theoretically, using flaxseed oil in combination with anticoagulant or antiplatelet drugs might have additive effects and increase the risk of bleeding.  Details Small clinical studies show that consuming flaxseed oil might decrease platelet aggregation and increase bleeding time (5898,21912).

ANTIHYPERTENSIVE DRUGS Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Possible •  Level of Evidence = D Theoretically, combining flaxseed oil with other antihypertensive drugs might have additive effects and increase the risk of hypotension.  Details Some clinical evidence suggests that long-term consumption of flaxseed oil can modestly lower systolic and diastolic blood pressure, while other clinical research shows no effect (16793,96426,101941,101954,111063,111067).

EZETIMIBE (Zetia) Interaction Rating = Moderate Be cautious with this combination. Severity = Moderate •  Occurrence = Probable •  Level of Evidence = B Concomitant use of flaxseed oil and ezetimibe reduces the absorption of alpha-linolenic acid from flaxseed oil.  Details In one clinical study, concomitant consumption of ezetimibe 10 mg daily with flaxseed oil 2 grams providing 1 gram of alpha-linolenic acid daily blocked the absorption of alpha-linolenic acid, resulting in an overall reduction in alpha-linolenic plasma levels from baseline (96433).

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General ...Orally, flaxseed oil is generally well tolerated. Topically, flaxseed oil seems to be well-tolerated.
Most Common Adverse Effects:
Topically: Itching, redness.
Serious Adverse Effects (Rare):
Orally: Severe allergic reactions such as anaphylaxis.

Endocrine ...Orally, flaxseed oil might cause gynecomastia. In a case report, a 70-year-old male developed gynecomastia after taking flaxseed oil daily for 3 months. Discontinuing flaxseed oil lead to resolution of gynecomastia (105478).

Gastrointestinal ...Orally, flaxseed oil may cause a change in bowel habits, dry mouth, and dyspepsia when taken at a dose of about 5 grams daily. However, these effects have been reported by only a small number of patients (approximately 3%) (16794). High doses of flaxseed oil (30 grams per day and higher) have been associated with loose stools and diarrhea (5898,11025).

Immunologic ...Severe allergic reactions such as anaphylaxis have been reported with flaxseed oil ingestion and also in workers processing flaxseed products (6809).

Ocular/Otic ...Topically, eye drops containing flaxseed oil may cause redness and itching (101953).

Oncologic ...Flaxseed oil has not been linked to increased prostate cancer risk. Although epidemiologic research has found that high dietary intake of alpha-linolenic acid (ALA) is associated with increased prostate cancer risk (1337,2558,7147,7823,12978), this risk does not seem to apply to ALA from plant sources, like flaxseed (12909).

(Read more about FLAXSEED OIL)