The discovery is the result of a joint study conducted by the Diabetes Discovery Platform from South Africa’s Medical Research Council (MRC) and the Agricultural Research Council’s (ARC) Infruitec-Nietvoorbij Institute.
Researchers found that an aspalathin-enriched extract of green rooibos is able to lower raised glucose levels in the blood of diabetic rats. Aspalathin is a unique antioxidant found in nature only in the rooibos plant (Aspalathus linearis). When combined with rutin, another key compound in rooibos tea, the glucose-lowering action was further enhanced.
Working with diabetic rats, the researchers were able to show that the rooibos extract could achieve a glucose-lowering effect comparable to existing diabetic drugs.
“Our work confirms the constituents present in rooibos could prove beneficial in the fight against diabetes,” says Doctor Johan Louw of the MRC who led the study. “We believe that rooibos can provide a basis to develop a standardised anti-diabetic product. In a country like South Africa, where a large section of the population relies on herbal medicines, such a product could be of huge value.”
'New and exciting possibilities'
“We have also confirmed that the polyphenols in complex mixtures, such as rooibos tea, work synergistically to achieve favourable health effects,” Louw explains. “This points to the value of drinking the ‘whole’ tea containing the required amount of these beneficial constituents, rather than a tablet containing just one of the compounds.”
“Our rooibos research to date focused mostly on the antioxidant activity of rooibos, but this evidence of its ability to lower blood glucose levels opens up new and exciting possibilities for this unique South African herb,” says Prof Lizette Joubert of the ARC who collaborated on this project. “We now need to dig deeper to determine the optimal combination and ratio of the active compounds such as aspalathin and rutin in controlling blood glucose levels, and also to understand the exact mechanisms involved.”
Follow-up studies indicated that other compounds are also important.
The study has been published online on 19 October 2012 in the Journal of Phytomedicine.
(This rooibos and diabetes study was funded jointly by the National Research Foundation of South Africa, the Medical Research Council and the Agricultural Research Council, with contributions to post-doctoral fellowships from the Department of Science and Technology. Prof Stephen Fey from the University of Southern Denmark also collaborated on the study.)
SA Rooibos Council press release
Rooibos: why it's good for you