Scientists have identified that cancer development is a multi-step process and that damage to genetic material (DNA) is likely to be a major cause of cancer and other chronic diseases. Rooibos haS been shown, in studies done at PROMEC Unit, to prevent DNA damage. Rooibos showed protective effects against chemical-induced mutagenicity in vitro as well as in vivo. The activity of two drug detoxifying enzymes, glutathione-S transferase (GST-) and UDP-glucuronosyltransferase (UDP-GT) were significantly induced in the liver of rats consuming Rooibos at concentrations of 2% customarily used for tea making purposes in South Africa.

 Several mechanisms involved in this ex vivo protection can be suggested: 1) the phase II detoxifying enzyme, GST-, catalyse conjugation of glutathione (GSH) to a variety of electrophillic compounds (e.g. chemical carcinogens) thus mediating a protective effect against carcinogenesis or mutagenesis. The ratio of reduced (GSH) and oxidised (GSSG) glutathione in the livers of rats consuming Rooibos were 5-6 fold higher. Reduced glutathione is a powerful intracellular antioxidant and the ratio of reduced to oxidised glutathione serves as a marker of the antioxidative capacity of the cell.

The increased ratio may be indicative of a reduced oxidative stress in the liver as compared to control rats drinking water, 2) the increased glucuronidation capacity of the liver also contributes to the deactivation of mutagens/metabolites that may serve as precursors for the ultimate carcinogen and 3) the presence of tea phenols in the liver cytosol may also interfere with the metabolic activation of carcinogens, thus contributing to the protective effect. Rooibos had no effect on the level of the Phase I activating enzymes in the liver.