This familiar plant is native to Europe, northern Africa, and central Asia, but red clover is also grown for pasturage and as a rotation crop in the Americas and Australia. (Nodules on the roots fix nitrogen, enhancing the soil.)
American children traditionally love hunting in a patch of red clover for a rare four-leaf specimen said to cause good luck, but it is the dried flowers that are used in herbal medicine.
Red clover blossoms are believed useful as an expectorant and for the treatment of bronchitis and asthma.
The herb has also been used topically to speed wound healing and treat psoriasis.
Current interest in red clover focuses on its use to relieve menopausal symptoms.
Cattle and sheep grazing too heavily on clover have fertility problems because of their phytoestrogen intake.
Red clover contains approximately 0.17 percent phytoestrogens. These include formononetin, genistein, daidzein, and biochanin A.
A volatile oil in the blossoms contains methyl salicylate, among other constituents. Some coumarin derivatives and cyanogenic glycosides have also been isolated.
The use of red clover extract as a supplement for menopausal women has gained attention through the marketing of an Australian product called Promensil. These pills, introduced in the United States in 1998, contain 40 mg each of isoflavones, in a standardized ratio.
Most of the research supporting red clover isoflavones has been conducted in Australia. The same firm markets a red clover supplement called Trinivin, also containing 40 mg standardized isoflavones, for men with healthy but enlarged prostates.
According to the studies conducted by the manufacturer, Novogen, red clover isoflavones are capable of suppressing hot flashes in perimenopausal women without leading to proliferation in uterine (endometrial) tissue.
A double-blind controlled trial published in the Journal of Clinical Endocrinology and Metabolism (March 1999) demonstrated that red clover isoflavones help keep large blood vessels pliable.
The usual daily dose contains 40 mg standardized red clover isoflavones. It may take four to six weeks to get the full benefit.
Pregnant women should not take red clover products until further tests determine whether this is safe. Isoflavones have estrogen-like effects, and estrogens are not recommended during pregnancy.
No adverse effects of trifolium isoflavones at the recommended dose have been reported. Blood biochemistry was monitored in some studies and showed no significant changes.
No interactions have been reported. It seems illogical, however, to mix Promensil with standard HRT regimens or oral contraceptives, and in theory these compounds could be incompatible.
A red clover extract containing coumarin derivatives might in theory interact with the anticoagulant Coumadin. Close monitoring of prothrombin time or INR is advisable.