Lignans can be beneficial for both men and women.
Lignans can act as antioxidants.
Lignans are phytoestrogens.
by Jocelyn Mathern, R.D.
Flaxseed has been around for
centuries but its popularity
with consumers has
increased greatly over the
past few years—and for
good reason. Flax is a healthy food containing
a mix of beneficial nutrients. It
is high in omega-3 fatty acids and
contains fair amounts of fiber, both soluble
and insoluble. Flax is also one of
the richest sources of lignans1—
compounds that are increasingly being
studied for their potential benefits to
health. This article will discuss flax lignans
in more detail and hopefully
answer your questions about what lignans
are and how they can be beneficial
for both men and women.
Lignans are phytoestrogens, or naturally
occurring plant estrogens that
can have a balancing effect on hormones.
Lignans can also act as antioxidants.
The main lignan in flaxseed is
secoisolariciresinol diglycoside or SDG.
When flaxseed is eaten, SDG is converted
by bacteria in the colon to mammalian
lignans: enterolactone and
enterodiol. This is important because
the mammalian lignans are the forms
of SDG that exert health effects in the
body. The amount of enterolactone
and enterodiol found in the blood and
urine of humans and animals is related
to the amount of plant lignans eaten. Large
intakes of flaxseed (and SDG) will result in
large amounts of enterodiol and enterolactone
excretion.
Lignans for Men’s Health
Lignans have many potential benefits for
men, specifically in areas related to prostate
health. A great deal of attention is being
focused on benign prostatic hyperplasia
(BPH) because it is a growing public health
problem. The American Urological
Association estimates that BPH affects 50
percent of men aged 50 to 60 and up to 90
percent of men over the age of 80. Simply
stated, BPH is a non-cancerous condition
where the prostate becomes enlarged. This
can be a problem because the urethra, the
tube carrying urine from the bladder to outside
the body, runs through the prostate (see
illustrations). A growing prostate can pinch
off the urethra and cause uncomfortable symptoms, like a frequent and overwhelming
urge to urinate, and painful
urination. The exact cause of BPH is
unknown, but male hormones seem to
play a role. Hormones also play a role in
another prostate condition—prostate
cancer, the second leading cause of cancer
death among men.
In the body, testosterone is converted
to a more potent form called dihydrotestosterone
or DHT. Normal, healthy
prostate cells require DHT for growth.
However, it is thought that too much of
this hormone can cause abnormal
growth—leading to BPH or causing
prostate cancer cells to divide. Therefore,
compounds that interfere with the conversion
of testosterone to DHT could
reduce a man’s chances of developing
these diseases.
Lignans have been shown to block the
action of the enzyme that converts testosterone
into DHT.2 Lignans may also
reduce the amount of testosterone available
for the body to use. In the average
male, only a small amount of testosterone
roams free in the blood. Most testosterone
is bound to a protein called SHBG
(sex hormone binding globulin). People
who consume large amounts of lignans
have been shown to have increased blood
levels of SHBG.3 An increase in SHBG
leaves less testosterone available to stimulate
prostate cell growth.
In other studies researchers have found
that lignan concentrations are higher in the
prostate fluid of men with a lower risk of
prostate cancer than those at increased risk.4
In a more recent study, 25 prostate cancer
patients were given a low-fat diet plus
flaxseed. At the end of the study, the men
had a reduction in testosterone levels, lower
rates of cancer cell growth and a trend
towards lower prostate specific antigen
(PSA ) levels.5 The study was done with whole
flaxseed, so the authors couldn’t determine
how much of the effect was due to lignans.
Therefore they conducted another study using
lignans derived from flaxseed. Results showed
that the lignans inhibited the growth of
human prostate cancer cells in a test tube.6
This supports the idea that lignans are protective
against prostate cancer.
While it is too early to say that eating flaxseed
and its lignans will reduce the risk of prostate
cancer and BPH, evidence is pointing in that
direction. By reducing male hormones that fuel
BPH and prostate cancer growth, lignans might
help reduce prostate size, alleviate symptoms of
BPH and protect against prostate cancer.
Lignans and Women’s Health
Lignans also have health benefits for women.
Because lignans are phytoestrogens, they have
the potential to help reduce symptoms of
menopause. There aren’t many studies yet that
have looked at lignans for menopause symptoms.
However, one study found a reduction
in mild menopause symptoms in women who
ate 40 grams of crushed flaxseed per day.7
Early research also suggests lignans may
protect against hormone related cancers in
women, such as breast cancer. Protective effects
have been shown in rats fed flaxseed8,9,10 or lignans
from flax.11 However, human studies are
more suggestive than conclusive at this point.
Observation studies have found that breast
cancer patients and people at high risk of breast
cancer excrete less mammalian lignans than
people with a lower risk of breast cancer.12 A
study in Finland found that women with high
enterolactone levels in their blood had a lower
risk of breast cancer.13 These studies suggest
that breast cancer may be more common in
people who eat fewer plant lignans.
A recent human clinical trial studied the effects of flaxseed on estrogen metabolism in
postmenopausal women. The women who ate
ground flaxseed had lower amounts of sex hormones
associated with breast cancer.14 Authors
of the study suggested that lignans played a
role, although it was not directly proven that
lignans were the only compounds producing
the beneficial effects.
However, lignans have
been shown to inhibit estrogen-stimulated
growth of breast cancer cells in a test tube,15
suggesting that lignans do play a significant
role in the anticancer activity of flaxseed. As
with prostate disease, the above studies are not
concrete proof that women who eat flaxseed
are less likely to get breast cancer. However,
evidence is accumulating.
Other potential health benefits
Lignans are also of interest in many other
health conditions besides those mentioned
above. To name a few, lignans are being
studied for potential benefits in heart health,
against colon cancer and surprisingly, even
hair loss. The same hormones that can cause
BPH are implicated in causing hair loss in men
and women. Therefore, lignans may have beneficial
properties against hair loss in the same way they may protect the prostate.
Although much larger and longer studies
need to be done to determine how much of the
effects are due to lignans or other components
in flaxseed, research indicates that lignans, in
combination with the other nutrients in flax,
may be a healthy addition to the daily diet.
How to select a lignan rich flax product.
Although flaxseed is the richest source of lignans,
consumers are not guaranteed that their
flax has a certain amount of lignans. Ground flaxseed contains lignans but flax oil is void of
lignans due to processing. There are some flax
oil products that claim to be high lignan but
rarely offer a standardized amount. A new generation
of flax products are appearing on the
market which are made from flax hulls, or the
outer portion of the flaxseed. Flax hulls naturally
contain up to 10 times more lignans than
regular ground flaxseed because the hull is
where most flax lignans are found. Dietary
supplement manufacturers are recognizing
this and are beginning to make products with
ingredients that are standardized sources of
flax lignans, such as LinumLifeTM, a natural
flax hull concentrate.
For more information on flax lignans visit www.linumlife.com and www.flaxcouncil.ca
Jocelyn Mathern, R.D.,
is technical specialist at
Acatris Inc, a distributor of
science-based, nutraceutical
ingredients. Jocelyn holds a
bachelor of science degree in
nutrition and corporate fitness
from North Dakota State
University. She is currently
pursuing her master’s degree
in nutrition at the University
of Minnesota. For more
information please contact
This e-mail address is being protected from spam bots, you need JavaScript enabled to view it
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- Adlercreutz, H., Fotsis, T., Heikkinen, R. et al. Lancet (1982). Vol. 2 (8311) pp. 1295–9.
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