THE NUTRITIONAL AND BIOLOGICAL SIGNIFICANCE OF SAPONINS

The association between saponin intake and cholesterol metabolism is reviewed in this article. Consumption of foods with high saponin concentrations by humans and its potential danger, is also discussed. Saponins have been shown to demonstrate hemolytic action towards red blood cells, and can be toxic if given intravenously but not orally. The majority of saponins form insoluble complexes with 3-beta-hydroxysteroids and are known to interact with and form large ixed micelles with bile acids and cholesterol. Thus in rats, saponin intake has been correlated with a hypocholesterolaemic effect by some authors, whilst others have disputed this claim. Saponins are also known to form insoluble saponin-mineral complexes, with iron, zinc and calcium. The beneficial effects on plasma cholesterol may be somewhat speculative in humans. Intakes up to 500 mg/day have not had particularly marked effects on plasma cholesterol although alteration to the enterohepatic circulation of bile acids and neutral sterol excretion may be of benefit. Part of the reasons for these minimal effects may be the lack of accurate characterisation of ''saponins'' from various sources. The potential hazards related to mineral complexing is an under-researched area and with the recent development of a synthetic saponin for use as an oral hypocholesterolaemic agent the risk/benefits need to be carefully analysed. Research needs to be undertaken to characterise dietary sources so that their potential usefulness can be better determined.