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Other common
name(s): purple clover, trefoil, wild clover
Scientific/medical
name(s): Trifolium
pratense
Description
Red clover is a perennial plant that grows wild in the
Americas, Europe, Australia, Asia, and northern Africa. The flower
head, which ranges from pink to purple or red, is the part of the plant
used in herbal remedies.
Overview
Available clinical evidence does not show that red clover is
effective in treating or preventing cancer, menopausal symptoms, or any
other medical conditions. It may also increase the risk of excessive
bleeding in some people. Some of its extracts (isoflavones) are being
tested to determine whether they help symptoms of menopause or reduce
the level of bad cholesterol in the blood. So far, results are mixed.
Studies looking at the extracts' effectiveness against prostate
enlargement and prostate cancer have begun. Other researchers are
looking at whether it will help blood pressure and insulin resistance
in diabetics and osteoporosis in women. Early findings suggest it may
merit further testing.
How is it promoted for use?
Proponents claim that red clover is useful for relieving
menopausal symptoms because it contains chemicals that are similar to
the hormone estrogen. They also claim that the herb suppresses coughs
(particularly whooping cough) and slows blood clotting. According to
some practitioners, people who take prescription blood-thinning
medications, such as warfarin (Coumadin), may be able to reduce their
dosage by taking red clover supplements.
Other supporters claim that red clover is effective for
treating cancers of the breast, ovaries, and lymphatic system, although
available scientific evidence does not support this. A few claim that
the herb acts as an antibiotic, an appetite suppressant, and a
relaxant. Some believe that red clover preparations can be used to help
speed wound healing and ease chronic skin conditions such as psoriasis.
What does it involve?
Red clover supplements are available as tablets, capsules, or
in liquid extract form. Dried red clover can be brewed into a tea.
Practitioners generally use a daily dosage of about 4 grams of dried
red clover, or 1.5 to 3.0 milliliters of liquid extract. (Five
milliliters is equal to one teaspoon, so this would be around
¼ to ½ teaspoon of the liquid.) The liquid
extract can be rubbed directly on skin or applied with a compress.
Dried red clover can also be made into a tea and either drunk or used
as a wash. It also comes in cream, lotion, or ointment form for use on
the skin and is sometimes used in cosmetics and soaps.
What is the history behind it?
For centuries, red clover has been grown in pastures to feed
cattle and other grazing animals. The herb is an ingredient in the
Hoxsey formula, Jason Winters' tea, and Essiac tea, which are common
herbal remedies (see Hoxsey Herbal Treatment
and Essiac Tea).
What is the evidence?
Scientists have identified phytoestrogens (estrogen-like
substances from plants) called isoflavones, mainly biochanin and
formononetin, in red clover. These 2 are precursors of the isoflavones
daidzein and genistein, which are found in smaller amounts in red
clover and also in soy. Low levels of anti-coagulant, or
blood-thinning, chemicals called coumarins are also present in red
clover. These substances have been identified in the plant, however,
most of the claims made for the herb have not been verified in humans
through randomized clinical trials.
One group of Australian researchers gave red clover
isoflavonoids to 20 men with prostate cancer before they had
prostatectomies (surgery to remove the prostate). The men who had
received flavonoids appeared to have more cancer cells that were dying
in their surgically removed prostate tissue. This was a very small
study, without a placebo group, and it did not compare survival,
quality of life, or symptoms. How this might affect treatment is not
yet known. Further studies are needed.
Most studies suggest that long-term use (10 years or more) of
estrogen replacement therapy after menopause may increase the risk of
heart disease and breast and endometrial cancers. Scientists are
looking for estrogen alternatives that do not increase these risks, and
phytoestrogens from red clover have been targeted for research.
In a small clinical study, researchers concluded that a diet
supplemented with red clover sprouts and other plants that contain
phytoestrogens may reduce the severity of menopausal symptoms. However,
this needs to be confirmed in other studies before red clover can be
routinely recommended. Studies of commercial red clover isoflavone
supplements for relief of menopausal symptoms have shown conflicting
results, although most (including the largest study) found no reduction
of hot flashes and no improvement in relevant quality of life measures.
Several studies of isoflavone extracts from red clover have
since shown mixed results on heart disease risk factors such as
cholesterol and triglycerides. For example, in a 2005 study, sixty
post-menopausal women taking red clover isoflavones had slightly lower
triglyceride levels and fewer menopausal symptoms than those on
placebo. No significant difference in LDL, or "bad," cholesterol was
noted.
An Australian study looked at both men and women taking
enriched red clover isoflavones. One supplement was enriched with the
phytoestrogens formononetin and the other with biochanin. These were
compared with placebo for six weeks. The men receiving the
biochanin-enriched supplement had somewhat lower levels of LDL
cholesterol, but the women did not.
Preliminary studies have looked at the use of isoflavones from
red clover to control blood pressure in diabetic patients and to treat
insulin resistance, osteoporosis, and benign prostatic hypertrophy
(enlarged prostate). Most of these studies were small and did not last
very long, and no conclusions can be reached about red clover
isoflavones' possible effectiveness for these conditions. Further
studies are needed. It is also important to note that the extracts are
not the same as the whole herb, and study results would not be likely
to show the same effects.
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.
Red clover is categorized as "generally recognized as safe" by
the U.S. Food and Drug Administration (FDA), and small amounts are
included in some teas and "health drinks." Patients with bleeding
problems or who take anticoagulant medications, including aspirin, may
want to avoid red clover because of the slight chance it could increase
the risk of serious bleeding. In addition, since the amount of the
blood-thinning chemical coumarin in red clover varies, it cannot be
relied on to produce the same effect even when the same dose is taken.
Additional potential interactions between red clover and other drugs
and herbs should be considered. Always tell your doctor and pharmacist
about any herbs you are taking.
Women who have had estrogen receptor-positive cancers or who
are pregnant or breastfeeding should not use this herb. No reports of
toxicity or overdose from red clover were found in the available
medical literature, although those who are allergic to clover should
avoid it. 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
Bown D. New
Encyclopedia of Herbs & Their Uses. New York, NY:
DK Publishing Inc; 2001.
Fetrow CW, Avila JR. Professional's
Handbook of Complementary & Alternative Medicines.
Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
Gruenwald J. PDR
for Herbal Medicines. 3rd ed. Montvale, NJ: Thomson PDR;
2004.
Howes JB, Bray K, Lorenz L, Smerdely P, Howes LG. The effects
of dietary supplementation with isoflavones from red clover on
cognitive function in postmenopausal women. Climacteric.
2004;7:70-77.
Howes JB, Tran D, Brillante D, Howes LG. Effects of dietary
supplementation with isoflavones from red clover on ambulatory blood
pressure and endothelial function in postmenopausal type 2 diabetes. Diabetes Obes Metab.
2003;5:325-332.
Jarred RA, Keikha M, Dowling C, McPherson SJ, Clare AM,
Husband AJ, Pedersen JS, Frydenberg M, Risbridger GP. Induction of
apoptosis in low to moderate-grade human prostate carcinoma by red
clover-derived dietary isoflavones.
Cancer Epidemiol Biomarkers Prev. 2002;11:1689-1696.
Knight DC, Howes JB, Eden JA. The effect of Promensil, an
isoflavone extract, on menopausal symptoms. Climacteric.
1999;2:79-84.
Nestel P, Cehun M, Chronopoulos A, DaSilva L, Teede H, McGrath
B. A biochanin-enriched isoflavone from red clover lowers LDL
cholesterol in men. Eur
J Clin Nutr. 2004;58:403-408.
Red clover. Drug Digest Web site.
http://www.drugdigest.org/DD/DVH/HerbsWho/0,3923,552774|Red%2BClover,00.html.
Accessed June 6, 2008.
Red clover. Memorial Sloan-Kettering Cancer Center Web site.
http://www.mskcc.org/mskcc/html/69350.cfm. Updated November 21, 2007.
Accessed June 6, 2008.
Tice JA, Ettinger B, Ensrud K, Wallace R, Blackwell T,
Cummings SR. Phytoestrogen supplements for the treatment of hot
flashes: the Isoflavone Clover Extract (ICE) Study: a randomized
controlled trial.[see comment]. JAMA.
2003;290:207-214.
Comment in:
ACP J Club.
2004;140:47.
J Fam Pract.
2003;52:846-847.
US Food and Drug Administration. Department of Health and
Human Services. Code of Federal Regulations, Food and Drugs (21), vol
3, Section 182. April 1, 2005.
van de Weijer PH, Barentsen R. Isoflavones from red clover
(Promensil) significantly reduce menopausal hot flush symptoms compared
with placebo. Maturitas.
2002;42:187-193.
Wilcox G, Wahlqvist ML, Burger HG, Medley G. Oestrogenic
effects of plant foods in postmenopausal women. BMJ.
1990;301:905-906.
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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