Red clover is on the Food and Drug Adminstration'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. 1 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. 2 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 Isoflavones .
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 isoflavones 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.
Dosing depends on the indication and the source of product. Use red clover extract as directed by your health care professional. Red clover is now used mainly as a source of isoflavones. The usual dose is 40 to 80 mg/day of standardized isoflavones.
Studies on plants with known concentrations of isoflavones or chemically pure isoflavones suggest that these compounds both have positive and negative effects on disease progression and fertility. In some countries, phytoestrogenic plants have been long used the treatment of menstrual problems menopausal symptoms and for fertility problems. Isoflavones are said to work in an adaptogenic way, this means that when estrogen levels decline, isoflavones mimic some of the effects of estrogen.
The use of red clover have been tested in humans or animals, however, its safety and effectiveness have not always been proven. Results from clinical studies on use of red clover isoflavones in menopause have been mixed. However, the North American Menopause Society recommends that red clover may be considered as an option for the treatment of menopausal symptoms because it has a low incidence of adverse effects.
