Sweet clover, long popular as food for grazing animals, is used medicinally as well. It contains various substances in the coumarin family. These chemicals are thought to help strengthen the walls of blood and lymph vessels. However there is no more than preliminary evidence that sweet clover is effective for any medical condition. In addition, use of sweet clover presents some safety concerns. (See Safety Issues for more information.)
The name Melilotus originates from the Greek word for honey, meli, and a term for clover-like plants, lotos. There are four common species in this genus of Eurasian origins: Melilotus alba, M. indica, M. officinalis, and M. altissimus.
The fresh or dried leaves and flowering stems of sweet clover were traditionally used as a diuretic.
Germany's Commission E has authorized use of sweet clover extract for symptoms of venous insufficiency (a condition closely related to varicose veins) as well as for the treatment of phlebitis and hemorrhoids.1 When used for this purpose, however, sweet clover is generally combined with bioflavonoids such as oxerutin. However, there is no meaningful evidence as ytet that sweet clover taken alone is effective for these conditions.
Sweet clover contains coumarins, substances related to the prescription blood-thinner warfarin. Most scientific study relevant to sweet clover involves prescription drugs that combine coumarins and bioflavonoids. These medications have also been used to treat venous insufficiency, as well as numerous other conditions, including elephantiasis, hemorrhoids, mild digestive disturbances and various forms of edema.2-7 However, it isn't clear whether sweet clover extracts containing coumarins would work in the same way as the coumarin portion of these pharmaceutical products.
Topical treatments made from sweet clover are sometimes recommended for the treatment of hemorrhoids and minor injuries,9 but as yet there is no real scientific evidence to support these proposed uses.
Sweet clover products are standardized to their coumarin content. For treating symptoms of venous insufficiency/ varicose veins, a daily dosage of a sweet clover preparation or extract providing 3 to 30 mg of coumarin is taken internally.8 (See "Safety Issues," below.)
The safety of any medicinal use of sweet clover has not been established in humans. Sweet clover contains various substances in the coumarin family. Many (but not all) of these substances thin the blood, and might cause excessive bleeding in some individuals. In particular, sweet clover should not be combined with blood-thinning drugs such as warfarin (Coumadin), heparin or drugs in the aspirin family.
Safety in pregnant or nursing women, young children, or individuals with severe liver or kidney disease has not been established.
1. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; 1999, P218-P219.
2. Bruneton J . Pharmacognosy, Phytochemistry, Medicinal Plants . 2nd Ed. Paris, France: Lavoisier Publishing; 1999,269-271.
3. Casley-Smith JR. Benzo-pyrones in the treatment of lymphoedema. Int Angiol. 1999;18:31-41.
4. Casley-Smith JR, Casley-Smith JR. Modern treatment of lymphoedema. II. The benzopyrones. Australas J. Dermatol. 1992;33:69-74.
5. Knight KR, Hurley JV, Hickey MI, et al. Combined coumarin and omental transfer treatments for canine proximal obstructive lymphoedema. Int J Exp Pathol. 1991;72:533-542.
6. Desprez-Curely JP, Cluzan R, Pecking A. Benzopyrones and post-mastectomy lymphedemas. Double-blind trial placebo versus sustained release coumarin with trioxyethylrutin (ter). In: Progress in Lymphology X: Proceedings of the Xth International Congress of Lymphology; 1985; Adelaide, South Australia.
7. Piller NB, Morgan RG, Casley-Smith JR. Double-blind trial of 5,6 benzo-[alpha]-pyrone in human lymphoedema. In: Progress in Lymphology X: Proceedings of the Xth International Congress of Lymphology; 1985; Adelaide, South Australia.
8. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; 1999, P218-P219.
9. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Austin, TX: American Botanical Council; 1999, P218-P219.
Last reviewed December 2015 by EBSCO CAM Review Board Last Updated: 12/15/2015