General Description
Flax (Linum usitatissimum) has been cultivated throughout the course
of history and is still a major farm crop in Russia, Canada, and
the northern plains of the United States. The flax plant has an
erect stem that branches outward at the top, with pale green, spearhead-shaped
leaves. Flax grows to a height of 20 inches and flowers from June
through August, bearing small, light-blue flowers that wither quickly
after opening in the morning. The mature plant produces a spherical
pod that contains ten brown seeds, each approximately 1/4 inch long.
The fibers of the plant are used to make linen. The seeds are pressed
to extract flaxseed oil (also known as linseed oil), which is used
to make linoleum and oil-based paints and is also consumed for health
purposes. The health benefits of flaxseed oil are primarily attributed
to its fatty acid profile. Flaxseed oil not only contains linoleic
acid (an omega-6 essential fatty acid found in most vegetable oils),
it is also a rich source of alpha linolenic acid, an omega-3 oil
with many useful functions in the body. In addition to its essential
fatty acid content, flaxseed oil contains unique compounds known
as lignans. The two primary lignans in flaxseed are matairesinol
and secoisolariciresinol-diglycoside. These compounds are converted
by intestinal bacteria into the mammalian lignans enterodiol (from
secoisolariciresinol-diglycoside) and enterolactone (from matairesinol).
These lignans have weakly estrogenic and antiestrogenic activities
and may play a role in estrogen-related health concerns such as
menopause, PMS, and certain cancers.
Health applications
Primary functions
In the body, alpha-linolenic acid is converted into eicosapentaenoic
acid (EPA) and docosahexaenoic acid (DHA). These omega-3 oils
are vital components of cellular membranes and are required for
the production of many hormones and neurotransmitters. They are
also involved in the production of compounds called prostaglandins,
hormone-like substances that help regulate allergic reactions,
inflammation, pain, swelling, blood pressure, and the functioning
of the heart, the kidneys, and the digestive system. Prostaglandins
are also important for blood clotting and the making of other
hormones. Linoleic acid, the omega-6 fatty acid found in flaxseed
oil, can be converted into three different fatty acids: gamma
linolenic acid (GLA), dihomo-linoleic acid, and arachidonic acid.
These fatty acids also play crucial roles in prostaglandin production.
Cardiovascular
health
Flaxseed oil is gaining popularity as a natural way to promote
cardiovascular health, and research indicates it may be beneficial
in this area. Studies have shown that flaxseed oil can help lower
total cholesterol and LDL cholesterol levels while improving HDL/LDL
ratios.1-4 High total cholesterol and LDL
levels are associated with increased risk for heart disease. Other
studies indicate that flaxseed oil may help protect cardiovascular
health by reducing the tendency of blood platelets to clump together,
thereby promoting healthier blood flow.5
Inflammation
Because essential fatty acids are important for prostaglandin
production, researchers have been investigating their involvement
in inflammatory conditions. Different fatty acids are used to
form different prostaglandins, some of which are inflammatory,
some anti-inflammatory. Arachidonic acid is used to form inflammatory
prostaglandins while DHA and EPA are involved in the formation
anti-inflammatory compounds. Low levels of omega-3 oils have been
observed in patients with inflammatory skin disorders like psoriasis6
and atopic eczema.7-8 High arachidonic acid
levels are common in sufferers of rheumatic arthritis and other
inflammatory disorders.9,10 Some research
indicates that omega-3 fatty acids may play a role in the prevention11
and treatment12 of rheumatoid arthritis. However,
most studies in this area have used fish oil, and the benefits
of flaxseed oil in this area have not been established.
Cancer
Some preliminary studies have been conducted to investigate the
potential of flax oil in cancer prevention. Low alpha-linolenic
acid levels have been shown to contribute to the spread (metastasis)
of breast cancer 13 and flaxseed oil has been
shown to slow the growth and metastasis of cancers in laboratory
animals.14,15 Research suggests that both
the alpha-linolenic acid and lignan portions of flaxseed oil may
exert anticancer activity at different stages of tumor development,15
however these effects have not been demonstrated in human subjects.
Dosage/toxicity
The amount of omega-3 oils needed in the body depends on the intake
of other fats. The typical "Western" diet is high in omega-6 fatty
acids and low in omega-3 oils. Many nutrition experts recommend
one tablespoon of flaxseed oil per day, which can be added to
salads or vegetables. The oil is also sold in softgel form, and
many people find this form most convenient. Flaxseed oil should
not be used in cooking because heat destroys alpha-linolenic acid.
Flaxseed oil is very well tolerated, and no toxicity has been
reported. |
