Flaxseed and flaxseed oil (Linum usitatissimum)

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Evidence

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Constipation
It has been suggested that flaxseed (not flaxseed oil) produces laxative effects. However, further evidence is needed to establish efficacy and dosing. Notably, in large doses, or when taken with inadequate water, flaxseed may precipitate bowel obstruction. 		B
Atherosclerosis
It has been suggested that flaxseed and its lignans may exert a beneficial effect on atherosclerotic plaque formation or cardiovascular outcomes, based on their purported antioxidant and lipid-lowering properties. Despite this evidence, it remains unclear if flaxseed supplementation improves human cardiovascular endpoints, and dosing regimens are lacking. 		C
Attention-deficit hyperactivity disorder (ADHD)
Preliminary evidence supports the idea that deficiencies or imbalances in certain highly unsaturated fatty acids may contribute to attention-deficit hyperactivity disorder (ADHD). According to one trial, alpha-linolenic acid (ALA)-rich nutritional supplementation in the form of flax oil may improve symptoms of ADHD. More research is needed to confirm these results. 		C
Benign prostatic hypertrophy (BPH)
Limited research suggests that flaxseed lignan extract may alleviate lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH). Additional well-designed trials are needed before a conclusion can be drawn. 		C
Breast cancer
It has been proposed that the lignan components of flaxseed may offer protection against hormone-sensitive cancers. Although organic flaxseed oil is used by many women to prevent breast cancer, and some herbal textbooks also support this claim, there is a lack of available research for or against the use of flaxseed oil, or organic flaxseed oil, for the prevention of cancer. Additional research is needed in this area. 		C
Cyclic mastalgia
It has been hypothesized that the hormonal effects of flaxseed may improve the symptoms of cyclic mastalgia, a condition characterized by breast pain and tenderness in women. Preliminary evidence suggests that flaxseed may reduce these symptoms. However, further research is warranted before a conclusion can be drawn. 		C
HIV/AIDS (weight gain)
Limited research suggests that ingestion of flax-derived alpha-linolenic acid (ALA), in combination with arginine and yeast RNA, was associated with weight gain in HIV patients. Further research is warranted before a conclusion may be drawn. 		C
Hyperglycemia/diabetes
Preliminary studies have reported mixed effects of oral flaxseed on serum glucose levels. Flaxseed cannot be suggested as a treatment for hyperglycemia (high blood sugar) or diabetes at this time. Further research is required before conclusions may be drawn. 		C
Hyperlipidemia
Flaxseed and flaxseed oil have been reported to possess lipid-lowering properties. Preliminary studies have examined the effects of flaxseed products on lipids, with mixed results. Additional research is needed at this time. 		C
Hypertension (high blood pressure)
Preliminary research suggests that two weeks of flaxseed supplementation may lower blood pressure. However, at this time there are insufficient data to recommend for or against this use of flaxseed. 		C
Keratoconjunctivitis sicca (dry eye syndrome)
Based on popular use, manufacturer studies, and case reports, flaxseed oil has been proposed as a possible treatment for dry eye syndrome. Limited research suggests that flaxseed oil capsules daily may be useful in the treatment of dry eye syndrome. Additional research is needed in this area. 		C
Lupus nephritis
Limited research suggests possible improvements in glomerular filtration rate (GFR) and serum creatinine levels in patients treated daily with flaxseed. Further research is warranted before a conclusion may be drawn. 		C
Menopausal symptoms
Preliminary research has examined the effects of flaxseed on menopausal symptoms, such as decreases in bone mineral density and cholesterol levels in menopausal women. Additional research is necessary before a clear conclusion may be drawn, and this remains an area of controversy. 		C
Obesity
There is limited research on the effects of flaxseed flour in obese patients. Limited early research has not shown evidence of benefit for weight loss or the reduction of the body mass index of obese patients. However, there may be a role for flax in treating inflammation associated with obesity. Additional research is needed in this area. 		C
Pregnancy
It has been proposed that alpha-linolenic acid (ALA), provided as flax oil capsules, may delay the timing of spontaneous delivery, but evidence supporting this use is lacking. 		C
Prostate cancer
Recent research suggests that flax may be useful in the treatment of prostate cancer. Additional high-quality human research is needed in this area. 		C

Key to grades
A Strong scientific evidence for this use
B Good scientific evidence for this use
C Unclear scientific evidence for this use
D Fair scientific evidence against this use (it may not work)
F Strong scientific evidence against this use (it likely does not work)

Grading rationale

Uses based on tradition or theory

The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Abdominal pain, acne, acute respiratory distress syndrome (ARDS), allergic reactions (delayed hypersensitivity reactions), anticoagulant (blood thinner), antioxidant, antiplatelet agent, bipolar disorder, bladder inflammation, boils, bowel irritation, bronchial irritation, burns (poultice), catarrh (inflammation of mucous membranes), colon cancer, cough suppressant, cystitis, depression, diabetic nephropathy, diarrhea, diverticulitis, dry skin, dysentery (severe diarrhea), eczema (skin rashes), enteritis (intestinal inflammation), expectorant, eye cleansing (debris in the eye), gastritis (stomach inflammation), glomerulonephritis (a type of kidney inflammation), gonorrhea, headache, infections, inflammation, interstitial nephritis (a type of kidney inflammation), irritable bowel syndrome, laxative-induced colon damage, liver protection, malaria, melanoma, menstrual luteal phase disorders, multiple sclerosis, ovarian disorders, pharyngitis, pimples, psoriasis, rheumatoid arthritis, skin infections, skin inflammation, skin irritation (emollient), sore throat, stomach pain, stomach upset, stroke, systemic lupus erythematosus (an autoimmune disorder), ulcerative colitis, upper respiratory tract infection, urinary tract infection, vaginitis (vaginal inflammation), vision improvement.

Dosing Related terms
NS_patient-flaxseed Portions of this document last updated: Sept. 1, 2012

THIS EVIDENCE-BASED MONOGRAPH WAS PREPARED BY
THE NATURAL STANDARD RESEARCH COLLABORATION
(www.naturalstandard.com)

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