Bloat occurs in animals grazing temperate legumes that contain saponins but not in livestock grazing tropical legumes or temperate legumes like birdsfoot trefoil that do not contain saponins. However, low-saponin cultivars of alfalfa can cause bloat. Humans generally do not suffer severe poisoning from saponins. Our cholesterin inactivates them so that only our mucus membranes are affected. Because of this, saponins have been used in sneezing powders, emetics, and cough syrups to facilitate expectoration.
Most saponins are also diuretic.
In humans, this effect disappears within a week following the neutralizing action of cholesterin. Alfalfa saponins may have potential in human health issues because they reduce serum cholesterol by preventing its reabsorption after it has been excreted in the bile. It is hypothesized that the saponins either bind with bile salts or cause the bile salts to bind to the polysaccharides in dietary fiber. Either way the bile salts are unavailable to bind with cholesterol.