Red clover has been cultivated since ancient times, primarily to provide a favorite grazing food for animals. But, like many other herbs, red clover was also a valued medicine. Although it has been used for many purposes worldwide, the one condition most consistently associated with red clover is cancer. Chinese physicians and Russian folk healers also used it to treat respiratory problems.
In the nineteenth century, red clover became popular among herbalists as an "alternative" or "blood purifier." This medical term, long since defunct, refers to an ancient belief that toxins in the blood are the root cause of many illnesses. Cancer, eczema, and the eruptions of venereal disease were all seen as manifestations of toxic buildup.
Red clover was considered one of the best herbs to "purify" the blood. For this reason, it is included in many of the famous treatments for cancer, including Jason Winter's cancer-cure tea.
Recently, special red clover extracts high in substances called
have arrived on the market. These isoflavones produce effects in the body somewhat similar to those of estrogen, and for this reason they are called phytoestrogens ("phyto" indicates a plant source). The major isoflavones in red clover include genistein and daidzen, also found in soy, as well as formononetin and biochanin.
Evidence is inconsistent on whether red clover isoflavones are helpful for
menopausal hot flashes
with the largest trial failing to find benefits.
A small and poorly reported
study provides weak evidence that red clover isoflavones might be helpful for
Although soy and, possibly, soy isoflavones
have been found to reduce cholesterol levels, two trials enrolling a total of more than 100 women failed to find red clover isoflavones helpful for this purpose.
However, in a double-blind, placebo-controlled comparative study of 80 people (both men and women), a red clover extract modified to be rich in biochanin did reduce LDL (“bad”) cholesterol, while one enriched in formononetin did not.
One very small double-blind study found hints that red clover isoflavones might slightly improve
in post-menopausal women with diabetes.
Preliminary evidence suggests that red clover isoflavones may help prevent or treat
In a 6-month, double-blind study, use of red clover isoflavones failed to enhance or harm
There is no evidence that red clover can help treat cancer. However, its usage in many parts of the world as a traditional cancer remedy has prompted scientists to take a close look at the herb. It turns out that the isoflavones in red clover may possess anti-tumor activity in the test tube.
However, such preliminary research does not prove that red clover can treat cancer.
Red clover is sometimes recommended for the treatment of
, and other skin diseases.
In a 12-week, double-blind, placebo-controlled trial of 30 post-menopausal women, use of red clover isoflavones at a dose of 80 mg daily significantly reduced
hot flash symptoms
as compared to placebo.
Benefits were also seen in a 90-day study of 60 post-menopausal women given placebo or 80 mg of red clover isoflavones.
However, a much larger study (252 participants) failed to find benefit with 82 or 57 mg of red clover isoflavones daily.
Two other studies also failed to find benefit. One, a 28-week, double-blind, placebo-controlled crossover study of 51 post-menopausal women, found no reduction in hot flashes among those given 40 mg of red clover isoflavones daily.
No benefits were seen in another double-blind, placebo-controlled trial, which involved 37 women given isoflavones from red clover at a dose of either 40 or 160 mg daily.
A typical dosage of red clover extract provides 40 to 160 mg of isoflavones daily. In the positive study described above, 80 mg daily were sufficient to reduce menopausal hot flashes.
Red clover is on the Food and Drug Administration's Generally Recognized as Safe (GRAS) list and is included in many beverage teas. However, detailed safety studies have not been performed.
Because of its blood-thinning and estrogen-like constituents, red clover should not be used by pregnant or nursing women, or women who have had breast or uterine cancer. A study investigating the safety of red clover in women with a family history of breast cancer found no changes in breast density or thickness of the uterine lining over a three-year period, which is somewhat reassuring.
However, the study was much too short to determine red clover's long-term effect on cancer risk. Safety in young children or those with severe liver or kidney disease has also not been established.
Based on their constituents, red clover extracts may conceivably interfere with hormone treatments and anticoagulant drugs (see the next section for specific drugs).
One double-blind study of post-menopausal women found the use of red clover isoflavones at a dose of 80 mg daily for 90 days resulted in increased levels of testosterone.
The potential significance of this is unclear. The same study found that red clover isoflavones reduced the thickness of the uterine lining, a finding that suggests low possibility for endometrial cancer.
For other potential risks due to the isoflavones in red clover (especially in concentrated isoflavone-rich extracts of red clover), see the full article on
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Last reviewed September 2014 by EBSCO CAM Review Board
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