This provides basic information about flaxseed and flaxseed oil—common names,
uses, potential side effects, and resources for more information. Flaxseed is the seed of the flax
plant, which is believed to have originated in Egypt. It grows throughout Canada and the northwestern
United States. Flaxseed oil comes from flaxseeds.
Flaxseed is also used for hot flashes and breast pain.
Flaxseed oil is used for different conditions than flaxseed, including arthritis.
Both flaxseed and flaxseed oil have been used for high cholesterol levels and in an effort
to prevent cancer.
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.:
Whole or crushed flaxseed can be mixed with water or juice and taken by mouth. Flaxseed is also
available in powder form. Flaxseed oil is available in liquid and capsule form. Flaxseed contains
lignans (phytoestrogens, or plant estrogens), while flaxseed oil preparations lack lignans.
Adults (over 18 years old)
Flaxseed oil is available in liquid and capsule form, flaxseed powder, flour, and soluble fiber.
10 to 250 grams have been taken by mouth.
Ground flaxseed: about 1/4 cup mixed with things like yogurt and fruit makes a wonderful breakfast.
Whole or bruised (not ground) flaxseed can be mixed with liquid and taken by mouth.
Generally, 1 tablespoon in this form is mixed with 6 to 12 ounces of liquid and taken
by mouth up to three times a day. Some studies use doses of soluble flaxseed mucilage/fiber
as high as 60 to 80 grams per kilogram (1 kilogram equals 2.2 pounds) of the person's weight.
These liquid forms of flaxseed should not be confused with preparations of flaxseed oil.
Anecdotally, 30-100 grams of flaxseed flour can be mixed with warm or hot water to form a moist
compress and applied to the skin up to three times a day. It is not clear how long a flaxseed
poultice should be used.
Children (under 18 years old)
Not enough information is available to advise use of flaxseed or flaxseed oil in children.
Flaxseed contains soluble fiber, like that found in oat bran, and is an effective laxative.
Studies of flaxseed preparations to lower cholesterol levels report mixed results.
Some studies suggest that alpha-linolenic acid (a substance found in flaxseed and flaxseed oil)
may benefit people with heart disease. But not enough reliable data are available to determine whether
flaxseed is effective for heart conditions.
Study results are mixed on whether flaxseed decreases hot flashes.
NCCAM is funding studies on flaxseed. Recent studies have looked at the effects of flaxseed
on high cholesterol levels, as well as its possible role in preventing conditions such as heart
disease and osteoporosis.
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.
Uses based on scientific evidence
Grade C: Unclear scientific evidence for this use
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). Based on one trial, alpha linolenic acid-rich nutritional supplementation in the form of flax oil may improve symptoms of ADHD. More research is needed to confirm these results.
C
Breast cancer (flaxseed, not flaxseed oil)
There is a lack of information from human studies that flaxseed is effective in preventing or treating breast cancer.
C
Diabetes (flaxseed, not flaxseed oil)
Human studies on the effect of flaxseed on blood sugar levels report mixed results. Flaxseed cannot be recommended as a treatment for diabetes at this time.
C
Dry eye syndrome
Taking flaxseed oil capsules by mouth may reduce dry eyes associated with Sjogren's syndrome patients.
C
Heart disease (flaxseed and flaxseed oil)
People who have had a heart attack are reported to benefit from diets rich in alpha-linolenic acid, which is found in flaxseed. Good studies that examine the effect of flaxseed on heart disease in humans are not available. It is unclear whether flaxseed supplementation alters the course of heart disease.
C
High blood pressure (flaxseed, not flaxseed oil)
In animals, diets high in flaxseed have mixed effects on blood pressure. One study in humans suggests that flaxseed might lower blood pressure. The evidence in this area is not clear, and more research is needed before a recommendation can be made.
C
High cholesterol or triglycerides (flaxseed and flaxseed oil)
In laboratory and animal studies, flaxseed and flaxseed oil are reported to lower blood cholesterol levels. Effects on blood triglyceride levels in animals are unclear, with increased levels in some research, and decreased levels in other research. Human studies in this area report mixed results, with decreased blood levels of total cholesterol and low-density lipoprotein ("bad cholesterol") in some studies, but no effect in other studies. Most human research has not been well-designed, and further research is needed before a recommendation can be made.
C
HIV/AIDS
There is a lack of strong evidence available in this area, and no recommendation can be made without further research.
C
Kidney disease/Lupus nephritis (flaxseed, not flaxseed oil)
There is a lack of strong evidence available in this area. More research is needed before a firm recommendation can be made.
C
Laxative (flaxseed, not flaxseed oil)
Early studies in humans suggest that flaxseed can be used as a laxative. However, more information is needed to compare effectiveness and dosing to more commonly used agents.
C
Menopausal symptoms
There is preliminary evidence from randomized controlled trials that flaxseed oil may help decrease mild menopausal symptoms. Additional research is necessary before a clear conclusion can be drawn and this remains an area of controversy. Patients should consult a doctor and pharmacist about treatment options before starting a new therapy. Overall effects on bone mineral density and lipid profiles remain unclear.
C
Menstrual breast pain (flaxseed, not flaxseed oil)
Early information from one study in women, the results of which have not been fully reported, suggests that flaxseed may reduce menstrual breast pain. However, further study is needed before a recommendation can be made.
C
Obesity
There is limited research on the effects of flaxseed flour and its effects in obese patients.
C
Pregnancy (spontaneous delivery)
It has been proposed that alpha-linolenic acid, provided as flax oil capsules, may delay the timing of spontaneous delivery, but the available evidence does not support this use.
C
Prostate cancer (flaxseed, not flaxseed oil)
There is limited high quality research of the effects of flaxseed or alpha-linolenic acid (which is in flaxseed) on the risk of developing prostate cancer. This area remains controversial as there is some data reporting possible increased risk of prostate cancer with alpha linolenic acid. Prostate cancer should be treated by a medical oncologist.
Flaxseed and flaxseed oil supplements seem to be well tolerated. Few side effects have been
reported.
Flaxseed, like any supplemental fiber source, should be taken with plenty of water; otherwise,
it could worsen constipation or, in rare cases, even cause intestinal blockage.
The fiber in flaxseed (not flaxseed oil)may lower the body's ability to absorb medications that
are taken by mouth. Flaxseed should not be taken at the same time as any conventional oral medications or
other dietary supplements. Drugs used by mouth should be taken one hour before or two hours after
flaxseed to prevent decreased absorption
Consumption of flaxseed (not flaxseed oil) may reduce the absorption of vitamins or supplements
taken by mouth at the same time. Therefore, vitamins and supplements should be taken an hour
before or two hours after a dose of flaxseed to prevent decreased absorption. Flaxseed may
alter the effects of psyllium and vitamin E in particular.
Tell your health care providers about any complementary and alternative practices you use.
Give them a full picture of what you do to manage your health. This will help ensure coordinated
and safe care.
People with diarrhea, irritable bowel syndrome, diverticulitis, or inflammatory bowel
disease (Crohn's disease or ulcerative colitis) should avoid flaxseed due to its possible
laxative effects
People with diabetes should use caution if taking flaxseed products by mouth, as the omega-3 fatty
acids in flaxseed and flaxseed oil may increase blood sugar levels.
The use of flaxseed or flaxseed oil during pregnancy and breastfeeding is not recommended.
Animal studies show possible harmful effects, and there is little information in humans.
Flaxseed may stimulate menstruation or have other hormonal effects and could be harmful to pregnancy.
unripe flaxseed pods are believed to be poisonous and should not be eaten.
Raw flaxseed or flaxseed plant may increase blood levels of cyanide, a toxic chemical
(this effect has not been reported when flaxseed supplements are taken at recommended doses).
Do not apply flaxseed or flaxseed oil to open wounds or broken skin.
The NCCAM Clearinghouse provides information on CAM and NCCAM, including publications and searches
of Federal databases of scientific and medical literature. The Clearinghouse does not provide medical
advice, treatment recommendations, or referrals to practitioners.
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