Flaxseed and Flaxseed Oil
Also indexed as: Lignan, Linseed Oil, Linum
Flaxseed, called linseed in some countries, is a good source of dietary fiber,
omega-3 fatty acids, and lignans. Each of these components may contribute to the health
effects of eating flaxseed, but flaxseed oil contains no fiber and very little lignan.
Where is it found?
In addition to its presence in flaxseed oil, small amounts of ALA are also found in canola,
soy, black currant, and walnut oils. Small
amounts of lignans are present in a wide variety of foods of plant origin.
Flaxseed and flaxseed oil
has been used in connection with the following conditions (refer to
the individual health concern for complete information):
Who is likely to be deficient?
ALA deficiencies are possible but believed to be rare, except in infants who are fed
formula that is omega-3 deficient. Lignan is not an essential nutrient, so deficiencies are
How much is usually taken?
For promoting bowel regularlity, 1 tablespoon (15 ml) of whole or ground flaxseed is taken
one or two times per day, accompanied by a full glass of water. When used to treat other
health conditions, it is used in amounts of 30 to 35 grams (1 to 2 ounces) per day.
Although it is not suitable for cooking, flaxseed oil (unlike fish oil) can be used in salads. Some doctors
recommend that people use 1 tablespoon (15 ml) of flaxseed oil per day as a supplement in
salads or on vegetables to ensure a supply of
essential fatty acids. Some conversion of ALA to EPA does occur,1 and this
conversion can be increased by restricting the intake of other vegetable oils.2
For those who wish to replace fish oil with flaxseed oil, research suggests taking up to
ten times as much ALA as EPA.3 Typically, this means 7.2 grams of flaxseed oil
equals 1 gram of fish oil. However, even if taken in such high amounts, flaxseed oil may not
have the same effects as fish oil. But, flaxseed oil will not cause a fishy-smelling burp (a
possible side effect of fish oil).
Are there any side effects or interactions?
Flaxseed oil toxicity has not been reported. However, there is conflicting information
about the effect of flaxseed oil and one of its major constituents, ALA, on cancer risk.
While most test tube and animal studies suggest a possible protective role for ALA against
breast cancer,4 5
6 7 8 one animal study9 and a preliminary human
study10 suggested increased breast cancer risk from high dietary ALA. Another
preliminary human study reported that higher breast tissue levels of ALA are associated with
less advanced breast cancer at the time of diagnosis.11 For prostate cancer, a test tube study reported ALA
promoted cancer cell growth,12 but preliminary human studies have shown ALA to be
associated with either an increased13 14 or decreased risk,15
or no change16 at all.
Advocates of flaxseed oil speculate that a potential association between ALA and cancer may
be due to the fact that meat contains ALA,
thus implicating ALA when the real culprits are probably other components of meat. In some
studies, however, saturated fat (and therefore probably meat) were taken into consideration,
and ALA still correlated with increased risk. The associations between ALA and cancer might
eventually be shown to be caused by substances found in foods rich in ALA rather than by ALA
itself. However, ALA has been reported to become mutagenic (able to cause precancerous
changes) when heated,17 which concerns some doctors.
The effect of ALA as an isolated substance, and of flaxseed oil on the risk of cancer in
humans remains unclear, with most animal and test tube studies suggesting protection, and some
preliminary human trials suggesting cause for concern. It is premature to suggest that ALA and
flaxseed oil will either cause or protect against human cancer at this time.
Flaxseed oil is not suitable for cooking and should be stored in an opaque, airtight
container in the refrigerator or freezer. If the oil has a noticeable odor it is probably
rancid and should be discarded.
As with any source of fiber, flaxseed should not be taken if there is possibility that the
intestines are obstructed. People with scleroderma (systemic sclerosis) should consult a
doctor before using flaxseed. Although a gradual introduction of fiber in the diet may improve
bowel symptoms in some cases, there have been several reports of people with scleroderma
developing severe constipation and even bowel obstruction requiring hospitalization after
Animal research suggests that large amounts of flaxseed or lignans consumed during
pregnancy might adversely affect the development of the reproductive system.19 No
studies have attempted to investigate whether this could be a problem in humans.
Allergic reactions to flaxseed have occasionally been reported, but are considered very
At the time of writing, there were no well-known drug interactions
with flaxseed oil.
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