The science behind Rooibos

Four studies on the bioavailability and safety of Rooibos
Research studies from South Africa, Italy, the UK and Switzerland have confirmed the bioavailability and safety of the antioxidants in Rooibos for humans.

Rooibos antioxidants metabolised in the body
Using urine samples from 12 healthy men who had consumed Rooibos, researchers found that aspalathin and nothofagin, major Rooibos antioxidants, are metabolised in the body so that it is easier for the body to excrete the metabolites. This means that the compounds are available for use by the body (bioavailability) and are not simply excreted in the same form that they are ingested.

Breiter et al., 2011. Bioavailability and antioxidant potential of rooibos flavonoids in humans following the consumption of different rooibos formulations. Food Chemistry, 128(2), pp.338-347.

Rooibos antioxidants changed by liver enzymes
Joint research between the Agricultural Research Council and the Medical Research Council were able to show that two Rooibos antioxidants – aspalathin and nothofagin – are changed by liver enzymes in vitro.

Van der Merwe et al., 2010. In vitro hepatic biotransformation of aspalathin and nothofagin, dihydrochalcones of rooibos (Aspalathus linearis), and assessment of metabolite antioxidant activity. Journal of Agricultural and Food Chemistry, 58(4), pp.2214-20.

Bioavailability of Rooibos flavonoids
A study in Italy found flavonoid metabolites in the urine of ten human volunteers after they had drunk 500 ml of green and fermented Rooibos. Most metabolites were excreted within five hours of tea consumption.

Stalmach et al., 2009. Bioavailability of C-linked dihydrochalcone and flavanone glucosides in humans following ingestion of unfermented and fermented rooibos teas. Journal of Agricultural and Food Chemistry, 57(15), pp.7104-11.

The metabolism of aspalathin
The metabolism of aspalathin was confirmed in humans in a collaborative study by researchers in the UK and Switzerland. They found metabolites of aspalathin in the urine of the study participants.

Courts, F.L. & Williamson, G., 2009. The C-glycosyl flavonoid, aspalathin, is absorbed, methylated and glucuronidated intact in humans. Molecular Nutrition & Food Research, 53(9), pp.1104-11.