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Other common
name(s): flaxseed oil, linseed, lint bells, linum
Scientific/medical
name(s): Linum
usitatissimum
Description
Flax is an annual plant cultivated for its fiber, which is
used in making linen. Flaxseed and its oil are used in herbal remedies.
Overview
Flaxseed and its oil have been promoted since the 1950s as a
dietary nutrient with anti-cancer properties. Most of the evidence of
its ability to prevent the growth or spread of cancer has come from a
few studies in animals. Only recently has there been some clinical
evidence suggesting that flaxseed supplements, along with a diet low in
fat, may be useful in men with early-stage prostate cancer. Controlled
clinical studies are needed to determine its usefulness in preventing
or treating cancer in humans.
How is it promoted for use?
Herbalists promote the use of flaxseed for constipation,
abdominal problems, breathing problems, sore throat, eczema, menstrual
problems, and arthritis. The oil extracted from flaxseeds is said to
lower cholesterol levels, boost the immune system, and prevent cancer.
Flaxseed oil is high in alpha-linolenic acid, an omega-3 fatty acid
that is thought to have beneficial effects against cancer when consumed
(see Omega-3 Fatty Acids).
Recently, attention has also focused on the flaxseed itself,
which is a rich source of lignans, compounds that can act as
anti-estrogens or as weak estrogens. It is thought that lignans may
play a role in preventing estrogen-dependent cancers, such as breast
cancer and other types of cancer. Lignans may also function as
antioxidants and, though mechanisms that are not yet fully understood,
may slow cell growth. When flaxseeds are consumed, the lignans are
activated by bacteria in the intestine.
What does it involve?
Flaxseed is available in flour, meal, and seed form. It may be
found in some multigrain breads, cereals, breakfast bars, and muffins.
The toasted seeds are sometimes mixed into bread dough or sprinkled
over salads, yogurt, or cereal. Flaxseed meal can be used in the same
way. Flaxseed oil is available in many health food stores in liquid
form and is sometimes mixed into cottage cheese or other foods. The oil
is also available in softgel capsules.
What is the history behind it?
Flaxseed was cultivated by the Babylonians in 3000 BC. A
German biochemist, Johanna Budwig, first brought attention to flaxseed
oil as a treatment in the 1950s through a diet she devised for cancer
patients. The diet was a strict regimen that avoided sugar, animal
fats, salad oil, meats, butter, and margarine. The patients were given
flaxseed oil, mixed with cottage cheese and milk, and meals high in
fruits, vegetables, and fiber. She claimed that within 3 months, some
patients on this diet had smaller tumors, some had no tumors left, and
all felt better.
What is the evidence?
Most of the evidence for an anti-cancer effect of flaxseed and
flaxseed oil comes from research using laboratory animals or cells
grown in laboratory dishes. In one cell culture study, flaxseed lignans
reduced stickiness and movement of breast cancer cells, both properties
related to the cancer's ability to spread or metastasize. Researchers
have also found that a diet supplemented with flaxseed may reduce the
formation, growth, or spread of prostate cancer, breast cancer, and
melanoma in mice. Flaxseed reduced formation of pre-cancerous colon
polyps in one study of rats, but in another study had no effect on the
formation of intestinal cancer in mice. In a 2007 report, flaxseed
reduced growth of breast cancer cells in mice and enhanced the
effectiveness of tamoxifen, a conventional drug for hormonal therapy.
There have been some small studies of the effects of flaxseed
in humans. A small study of 15 men found that a low-fat diet
supplemented with flaxseed lowered their blood prostate-specific
antigen (PSA) levels and slowed the growth of benign prostate cells,
suggesting that it might be useful in reducing risk of prostate cancer.
Another study of 25 men with prostate cancer found that a low-fat diet
along with ground flaxseed reduced serum testosterone, slowed the
growth rate of cancer cells, and increased the death rate of cancer
cells.
More research in humans is needed to determine the usefulness
of flaxseed in cancer treatment and prevention. While animal and
laboratory studies show promise, further studies are needed to
determine whether the results apply to humans.
Are there any possible problems or
complications?
This product is sold as a
dietary supplement in the United States. Unlike companies that produce
drugs (which must provide the FDA with results of detailed testing
showing their product is safe and effective before the drug is approved
for sale), the companies that make supplements do not have to show
evidence of safety or health benefits to the FDA before selling their
products. Supplement products without any reliable scientific evidence
of health benefits may still be sold as long as the companies selling
them do not claim the supplements can prevent, treat, or cure any
specific disease. Some such products may not contain the amount of the
herb or substance that is written on the label, and some may include
other substances (contaminants). Though the FDA has written new rules
to improve the quality of manufacturing processes for dietary
supplements and the accurate listing of supplement ingredients, these
rules do not take full effect until 2010. And, the new rules do not
address the safety of supplement ingredients or their effects on health
when proper manufacturing techniques are used.
Most such
supplements have not been tested to find out if they interact with
medicines, foods, or other herbs and supplements. Even though some
reports of interactions and harmful effects may be published, full
studies of interactions and effects are not often available. Because of
these limitations, any information on ill effects and interactions
below should be considered incomplete.
The immature pods of flaxseed are poisonous and should never
be used. Flaxseeds and flaxseed oil can spoil if they are not kept
refrigerated. They should be protected from light, heat, air, and
moisture.
Some possible side effects include diarrhea, gas, and nausea.
Flaxseed oil should not be used with other laxatives or stool
softeners. People who have inflammatory disease or narrowing of the
intestine, esophagus, or stomach should avoid flaxseed. Flaxseed is
also not recommended by some doctors for people with diabetes.
Some medicines and supplements may not be absorbed properly if
they are taken at the same time as flaxseed. For this reason, some
doctors recommend taking medications 1 or 2 hours before or after
taking flaxseed.
Flaxseed may also interfere with x-rays taken after a barium
enema, and some doctors recommend avoiding taking flaxseed before
undergoing this test. In addition, the potential interactions between
flaxseed and other drugs and herbs should be considered. Some of these
combinations may be dangerous. Always tell your doctor and pharmacist
about any herbs you are taking.
A few severe allergic reactions to flaxseed have been
reported. Those allergic to other plants may be more likely to be
allergic to flax. Relying on this type of treatment alone and avoiding
or delaying conventional medical care for cancer may have serious
health consequences.
Additional Resources
More information from your American Cancer
Society
The following information on complementary and alternative
therapies may also be helpful to you. These materials may be found on
our Web site (www.cancer.org)
or ordered from our toll-free number (1-800-ACS-2345).
References
Basch E, Bent S, Collins J, Dacey C, Hammerness P, Harrison M,
Smith M, Szapary P, Ulbricht C, Vora M, Weissner W. Natural Standard
Resource Collaboration. Flax and flaxseed oil (Linum usitatissimum): a
review by the Natural Standard Research Collaboration. J Soc Integr Oncol.
2007;5:92-105.
Bergman Jungestrom M, Thompson LU, Dabrosin C. Flaxseed and
its lignans inhibit estradiol-induced growth, angiogenesis, and
secretion of vascular endothelial growth factor in human breast cancer
xenografts in vivo. Clin
Cancer Res. 2007;13:1061-1067.
Chen J, Hui E, Ip T, Thompson LU. Dietary flaxseed enhances
the inhibitory effect of tamoxifen on the growth of estrogen-dependent
human breast cancer (mcf-7) in nude mice. Clin Cancer Res.
2004;10:7703-7711.
Chen J, Power KA, Mann J, Cheng A, Thompson LU. Flaxseed alone
or in combination with tamoxifen inhibits MCF-7 breast tumor growth in
ovariectomized athymic mice with high circulating levels of estrogen. Exp Biol Med.
2007;232:1071-1080.
Chen J, Stavro PM, Thompson LU. Dietary flaxseed inhibits
human breast cancer growth and metastasis and downregulates expression
of insulin-like growth factor and epidermal growth factor receptor. Nutr Cancer.
2002;43:187-192.
Chen J, Wang L, Thompson LU. Flaxseed and its components
reduce metastasis after surgical excision of solid human breast tumor
in nude mice. Cancer
Lett. 2006;234:168-175.
Demark-Wahnefried W, Price DT, Polascik TJ, Robertson CN,
Anderson EE, Paulson DF, Walther PJ, Gannon M, Vollmer RT. Pilot study
of dietary fat restriction and flaxseed supplementation in men with
prostate cancer before surgery: exploring the effects on hormonal
levels, prostate-specific antigen, and histopathologic features. Urology.
2001;58:47-52.
Demark-Wahnefried W, Robertson CN, Walther PJ, Polascik TJ,
Paulson DF, Vollmer RT. Pilot study to explore effects of low-fat,
flaxseed-supplemented diet on proliferation of benign prostatic
epithelium and prostate-specific antigen. Urology.
2004;63:900-904.
Flaxseed. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69220.cfm. Accessed June 4, 2008.
Haggans CJ, Hutchins AM, Olson BA, Thomas W, Martini MC,
Slavin JL. Effect of flaxseed consumption on urinary estrogen
metabolites in postmenopausal women. Nutr Cancer.
1999;33:188-195.
Lin X, Gingrich JR, Bao W, Li J, Haroon ZA, Demark-Wahnefried
W. Effect of flaxseed supplementation on prostatic carcinoma in
transgenic mice. Urology.
2002;60:919-924.
Natural Standard. Herbal/plant therapies: flaxseed and
flaxseed oil (linum usitatissimum). Complementary/Integrative Medicine
Education Resources, The University of Texas M.D. Anderson Cancer
Center Web site.
http://www.mdanderson.org/departments/cimer/display.cfm?id=0D86E843-44DF-4766-9D743BA1FE8B9877&method=displayFull.
Accessed June 4, 2008.
Yan L, Yee JA, Li D, McGuire MH, Thompson LU. Dietary flaxseed
supplementation and experimental metastasis of melanoma cells in mice. Cancer Lett.
1998;124:181-186.
Note:
This
information may not cover all possible claims, uses, actions,
precautions, side effects or interactions. It is not intended as
medical advice, and should not be relied upon as a substitute for
consultation with your doctor, who is familiar with your medical
situation.
Last Medical Review: 11/01/2008
Last Revised: 11/01/2008
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