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Other common
name(s): evening primrose oil, borage seed oil, black
currant oil, GLA
Scientific/medical
name(s): gamma linolenic acid
Description
Gamma linolenic acid (GLA) is an omega-6 unsaturated fatty
acid made in the human body from linoleic acid, an essential fatty acid
found in vegetable oils and egg yolks. The main supplemental sources of
GLA are oils of the seeds of evening primrose, borage, and black
currant plants. (For more information, see "Evening
Primrose".) Many companies sell these oils as good sources of
GLA. It is also found in human breast milk.
Overview
Some studies have shown that GLA can slow or stop the growth
of some types of cancer cells in tissue cultures in the laboratory and
may help some cancer drugs to work better. However, there is very
little evidence as yet that GLA supplements are effective in preventing
or treating cancer in humans. Human studies are under way to evaluate
the role of GLA and other essential fatty acids on the growth of cancer
cells.
How is it promoted for use?
Gamma linolenic acid is normally used by the body to make
prostaglandins (hormone-like substances). Prostaglandins are believed
to be involved in many processes in the body, including regulation of
the immune system.
Most GLA in the human body is taken in as linoleic acid and
then metabolized to GLA. Most people get plenty of linoleic acid in
their diets and can convert it to GLA. Some researchers have suggested
that some people (such as those with diabetes or skin allergies) do not
make enough GLA from linoleic acid and may therefore benefit from
taking GLA supplements.
It has been proposed that GLA supplements may stop or slow the
growth of cancer cells. GLA and GLA-rich supplements have also been
promoted to help people with breast pain, skin allergies, diabetes,
obesity, rheumatoid arthritis, heart disease, high blood pressure,
premenstrual syndrome, multiple sclerosis, attention deficit
hyperactivity disorder (ADHD), and neurological problems related to
diabetes.
What does it involve?
Gamma linolenic acid is available in liquid and capsule form,
usually as a natural ingredient in black currant oil, borage oil, or
evening primrose oil. The amount of GLA contained in the different
types of supplements varies (for example, evening primrose supplements
may contain about 10% GLA). Dosages of GLA as a supplement are
generally in the range of 500 milligrams to 3,000 milligrams per day.
An injectable form of GLA is being studied.
What is the history behind it?
Some of the plants whose seeds contain GLA have been used as
folk remedies for hundreds, if not thousands, of years. However, the
recognition of GLA and of these seed oils as a source of GLA is much
more recent.
Research in the 1980s found that hormone-like substances
called prostaglandins played a role in many biological processes. Since
GLA was known to be a building block for some prostaglandins, it was
reasoned that GLA might be helpful in treating human disease. While GLA
is widely touted for its health benefits, research on its effectiveness
in human diseases is still at an early stage.
What is the evidence?
Much of the research on GLA has been done using evening
primrose oil. This makes it hard to credit any effects specifically to
GLA, as the oil has many components, including linoleic acid and
vitamin E. Studies of the ability of evening primrose oil and GLA to
prevent or treat cancer in humans are still in the earliest stages.
Dietary GLA (most of which is consumed as linoleic acid)
contributes to making and regulating prostaglandins; however, the exact
role of the different prostaglandins in fighting cancer is still not
clear.
Some research in the laboratory has suggested that GLA may
prove to be helpful against certain cancers, but this research is still
early. In laboratory tests, gamma linolenic acid slowed the growth of
several types of human cancer cells. It has also been shown to make
certain anti-cancer drugs better at killing cancer cells in laboratory
studies.
There have been fewer clinical trials studying the effect of
GLA on tumors. In a small English study of about eighty breast cancer
patients, those who took GLA supplements in addition to tamoxifen
responded more quickly to treatment than those who took tamoxifen
alone. It is not clear if any longer term benefits were achieved.
An injectable form of GLA was studied in a clinical trial of
48 patients with pancreatic cancer. Those who received the highest
doses of GLA were reported to live longer. However, a larger study of
278 patients did not find that those receiving GLA (either by mouth or
injected into a vein) lived longer than expected. Some researchers have
proposed that the injectable form of GLA may only be effective if
injected directly into the tumor. Future studies may look at GLA
combined with chemotherapy drugs.
Some studies have looked at the use of maglumine GLA (which is
chemically different from the form sold in dietary supplements) against
bladder cancer by infusing it directly into the bladder through a
catheter. One small study found that about 43% of people with
early-stage bladder cancer had their tumors shrink or completely
disappear with this therapy. Clearly, more research is needed to learn
which method of giving GLA is most effective, and whether GLA is useful
in treating cancer, either alone or with standard treatments.
Neither GLA nor other GLA-rich supplements (such as evening
primrose oil) have been convincingly shown to be useful in preventing
or treating any other health conditions.
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.
Gamma linolenic acid does not appear to be toxic. However, it
has been reported to aggravate a type of epilepsy and should not be
used by people who take anti-seizure medicines. Long-term use of GLA
may lead to inflammation, blood clots, or lowered immune system
functioning.
Borage oil, which is sometimes used as a source of GLA, may
contain substances that can harm the liver or possibly cause cancer. If
you take borage oil, be sure it is certified as free of unsaturated
pyrrolizidine alkaloids (UPAs), and do not take more than the
recommended dose.
Women who are pregnant or breastfeeding should speak with
their doctor before using this treatment. 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
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Reynolds PD, Tuffnell Q. An open-label phase I/II dose escalation study
of the treatment of pancreatic cancer using lithium gammalinolenate. Anticancer Res.
1996 Mar-Apr;16(2):867-874.
Fetrow CW, Avila JR. Professional’s
Handbook of Complementary and Alternative Medicines.
Springhouse, Pa: Springhouse Corp; 1999.
Harris NM, Crook TJ, Dyer JP, Solomon LZ, Bass P, Cooper AJ,
Birch BR. Intravesical meglumine gamma-linolenic acid in superficial
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Horrobin DF. Essential fatty acid metabolism and its
modification in atopic eczema. Am
J Clin Nutr. 2000;71:367S-372S.
Johnson CD, Puntis M, Davidson N, Todd S, Bryce R. Randomized,
dose-finding phase III study of lithium gamolenate in patients with
advanced pancreatic adenocarcinoma. Br J Surg. 2001
May;88(5):662-668.
Kenny FS, Pinder SE, Ellis IO, Gee JM, Nicholson RI, Bryce RP,
Robertson JF. Gamma linolenic acid with tamoxifen as primary therapy in
breast cancer. Intl J
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Memorial Sloan Kettering Cancer Center. Borage. Accessed at:
http://www.mskcc.org/mskcc/html/69148.cfm on June 11, 2008.
Menendez JA. Ropero S. Lupu R. Colomer R. Omega-6
polyunsaturated fatty acid gamma-linolenic acid (18:3n-6) enhances
docetaxel (Taxotere) cytotoxicity in human breast carcinoma cells:
Relationship to lipid peroxidation and HER-2/neu expression. Oncology Reports.
11(6):1241-52, 2004.
Medline Plus; (Oenothera biennis L.). Evening primrose oil;
Accessed at:
http://www.nlm.nih.gov/medlineplus/druginfo/natural/patient-primrose.html
on September 8, 2008.
Menendez JA. Vellon L. Colomer R. Lupu R. Effect of
gamma-linolenic acid on the transcriptional activity of the Her-2/neu
(erbB-2) oncogene JNCI.
97(21):1611-5, 2005
Phinney S. Potential risk of prolonged gamma-linolenic acid
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Whitehouse PA, Cooper AJ, Johnson CD. Synergistic activity of
gamma-linolenic acid and cytotoxic drugs against pancreatic
adenocarcinoma cell lines. Pancreatology. 2003;3(5):367-373.
Williams HC. Evening primrose oil for atopic dermatitis. BMJ.
2003;327:1358-1359.
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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