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Other common
name(s): Evening primrose oil
Scientific/medical
name(s): Oenothera
biennis
Description
Evening primrose is a flowering plant originally native to
North America that now grows throughout much of Europe and parts of
Asia. It blooms every other year and its large, fragrant yellow flowers
open at dusk and remain open through the night. In Germany, the plant
is called night candle
for this reason. The oil extracted from the ripe seeds and the fresh
plant is used in herbal remedies.
Overview
Available scientific evidence does not support evening
primrose oil as an effective treatment for preventing or treating
cancer. Some studies suggest it may help with certain types of skin
rashes, such as eczema and atopic dermatitis, although further research
is needed to confirm this. While the essential fatty acids found in
evening primrose play a role in health and disease, larger clinical
studies are needed to find out whether they are useful in treating
cancer or other conditions.
How is it promoted for use?
Evening primrose is promoted as an herbal remedy for a very
broad range of conditions, including dermatitis, premenstrual syndrome,
menopausal symptoms, eczema, inflammation, hyperactivity in children,
high cholesterol, asthmatic cough, upset stomach, psoriasis, rheumatoid
arthritis, and diabetic nerve damage. Some proponents also believe the
plant has anti-cancer properties. Some claims of evening
primrose's health benefits are based on the fact that the oil
extracted from the seeds and plant contains gamma-linolenic acid (GLA),
an essential omega-6 fatty acid. GLA is thought to play a key role in
many biological processes. Omega-6 fatty acids are different from
omega-3 fatty acids (see Gamma
Linolenic Acid [GLA] and Omega-3 Fatty Acids).
What does it involve?
The oil can be purchased in capsules, gelcaps, and a less
commonly available liquid form, and the powdered plant can be purchased
and made into a tea. Daily doses of evening primrose oil have ranged
from 2 to 16 capsules of 500 milligrams in clinical trials, although in
one study up to 36 capsules per day were used.
What is the history behind it?
In folk medicine, evening primrose has been used to treat
asthma, gastrointestinal disorders, whooping cough, and symptoms
associated with premenstrual syndrome. The scientific name of the
plant, Oenothera biennis, comes from the two Greek words oinos ("wine")
and thera ("hunt"), because eating the roots was once believed to
increase a person's appetite for wine. Folklore also says that evening
primrose counters the effects of drinking too much wine. Use of evening
primrose as an herbal remedy is relatively recent. Scientific research
regarding its healing properties began in the 1980s.
What is the evidence?
Available scientific evidence does not support claims that
evening primrose oil has any effect on cancer. Most research has been
conducted in laboratory settings or involved small numbers of patients.
One laboratory study concluded that evening primrose oil might help
slow the growth of breast cancer cells. Other laboratory studies have
found that evening primrose oil slowed the growth of skin cancer cells,
and a diet enriched with evening primrose oil was thought to enhance
the body's ability to fight tumors. However, further studies are needed
to learn whether the results apply to humans.
Research into the use of evening primrose oil for other
conditions has been mixed. Some research evidence suggests that it may
help symptoms of rheumatoid arthritis over the long term, although more
information is needed. Studies that tested evening primrose oil taken
by mouth for the skin conditions atopic dermatitis and eczema showed
conflicting results. Results of studies of evening primrose oil for
treating premenstrual syndrome, menopause symptoms, breast pain, and
psoriasis have been either mixed or not favorable. Most research has
been conducted in laboratory settings or involved small numbers of
patients. In late 2002, the U.K. withdrew the prescription forms of
fatty acid that were made from evening primrose due to lack of evidence
of its effectiveness. A recent review concluded that evening primrose
is not effective as a treatment for menopausal symptoms. Large-scale
clinical trials involving humans are needed to find out the value of
evening primrose in treating any illness.
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.
No major health hazards have been identified with taking
evening primrose. Headaches, bloating, and indigestion are reported as
possible side effects. One article reported that the fatty acid in
primrose oil (GLA) might lower seizure thresholds, so it should not be
used in people who have seizures. It may also increase the seizure risk
in those who are taking medicines for schizophrenia.
There are also reports that GLA may slow the blood's ability
to clot. Evening primrose oil can cause problems if taken with herbs or
medicines that slow blood clotting (such as blood-thinning medications
like warfarin. In addition, the potential interactions between oil of
evening primrose 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. Women who are pregnant or
breast-feeding should not use this herb. 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
Belch JJ, Ansell D, Madhok R, O’Dowd A, Sturrock RD.
Effects of altering dietary essential fatty acids on requirements for
non-steroidal anti-inflammatory drugs in patients with rheumatoid
arthritis: a double blind placebo controlled study. Ann Rheum Dis.
1988;47:96-104.
Bown D. Encyclopedia of Herbs & Their Uses. New York,
NY: DK Publishing Inc; 1995. Cheema D, Coomarasamy A, El-Toukhy T.
Non-hormonal therapy of post-menopausal vasomotor symptoms: a
structured evidence-based review. Arch Gynecol Obstet.
2007;276:463-469.
Epogam and Efamast (gamolenic acid) withdrawal of marketing
authorisations. CMO’s Update: A communication to all doctors
from the Chief Medical Officer. 2002;34:2. Department of Health Web
site.
http://www.dh.gov.uk/en/Publicationsandstatistics/Lettersandcirculars/CMOupdate/DH_4003840.
Evening primrose. Drug Digest Web site.
http://www.drugdigest.org/DD/DVH/HerbsWho/0,3923,4010|Evening%20Primrose,00.html.
Accessed June 4, 2008.
Evening primrose oil. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69216.cfm. Accessed June 4, 2008.
Fetrow CW, Avila JR. Professional's
Handbook of Complementary & Alternative Medicines.
Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
Goyal A, Mansel RE; Efamast Study Group. A randomized
multicenter study of gamolenic acid (Efamast) with and without
antioxidant vitamins and minerals in the management of mastalgia. Breast J.
2005;11:41-47.
Gruenwald J. PDR
for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR;
2004.
Kleijnen J. Evening primrose oil. BMJ.
1994;309:824-825.
Miller LG. Herbal medicinals: selected clinical considerations
focusing on known or potential drug-herb interactions. Arch Intern Med.
1998;158:2200-2211.
Muñoz SE, Lopez CB, Valentich MA, Eynard AR.
Differential modulation by dietary n-6 or n-9 unsaturated fatty acids
on the development of two murine mammary gland tumors having different
metastatic capabilities. Cancer
Lett. 1998;126:149-155.
Muñoz SE, Piegari M, Guzmán CA, Eynard
AR. Differential effects of dietary Oenothera, Zizyphus mistol, and
corn oils, and essential fatty acid deficiency on the progression of a
murine mammary gland adenocarcinoma. Nutrition.
1999;15:208-212.
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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