Alfalfa is used as a diuretic, for kidney conditions, bladder and prostate conditions, asthma, arthritis, rheumatoid arthritis, diabetes, indigestion, and thrombocytopenic purpura. It is used for its trace elements and as a source of vitamins A, C, E, and K4; and minerals calcium, potassium, phosphorous, and iron.
The applicable parts of alfalfa are the above ground parts. The leaves and sprouts contain saponins. The saponins appear to decrease serum cholesterol, but not triglycerides, by binding cholesterol and decreasing its absorption.
Alfalfa seeds contain the amino acid L-canavanine. L-canavanine is metabolized to produce canaline and urea. Canaline seems to bind pyridoxine phosphate, a cofactor in the metabolism of amino acids, potentially decreasing amino acid enzyme activity.
L-canavanine is also thought to be responsible for the immunostimulatory effects of alfalfa, by decreasing T cell regulation of B cells or by directly binding B cells.
Alfalfa contains manganese which might be responsible for reported hypoglycemic effects. Alfalfa leaves also contain triterpene glycosides including medicagol, which appear to have antifungal and antibacterial activity. The isoflavonoids coumetrol, genistein, biochanin A, and daidzein have also been isolated and may be responsible for alfalfas reported estrogenic effects.