Formal research on the anti-diabetic effects of Rooibos

From the Phytomedicine journal:
Using a cell model (muscle cells) researchers have confirmed that unfermented Rooibos extract is able to alleviate the development of insulin resistance and to improve the cells' uptake of glucose. This means that Rooibos could play a key role in the prevention of diabetes.

Mazibukoa et al. 2013. Amelioration of palmitate-induced insulin resistance in C2C12 muscle cells by Rooibos (Aspalathus linearis). Phytomedicine, 20(10), pp. 813-819. Available here.

From the Phytomedicine journal:
Researchers found that aspalathin-enriched "green" Rooibos extract and aspalathin decreased blood glucose levels. They used in vitro and in vivo methods to obtain their results. Aspalathin, in combination with rutin, another Rooibos polyphenol, performed even better. This suggests that the polyphenols might interact to create a greater hypoglycaemic effect.

Muller et al. 2012. Acute assessment of an aspalathin-enriched green Rooibos (Aspalathus linearis) extract with hypoglycaemic potential. Phytomedicine, 20(1), pp. 32-9. Available here.

From the European Journal of Nutrition:
The results of this study strongly suggest that aspalathin, a major polyphenol in Rooibos, has anti-diabetic potential. The authors found that the compound affects the cellular signalling pathways involved in glucose metabolism, and that it reduces the expression of certain genes that code for liver enzymes involved in glucose and fat production. Mice were used as a model of Type 2 diabetes, along with cell lines.

Son et al. 2012. Aspalathin improves hyperglycemia and glucose intolerance in obese diabetic ob/ob mice. European Journal of Nutrition. Available here.

From the Phytomedicine journal:
According to this study, aspalathin helped to improve the glucose uptake of muscle cells (and thereby helped to maintain normal blood sugar levels) in mice with type 2 diabetes. Aspalathin also stimulates pancreatic beta-cells to secrete insulin and helps to improve impaired glucose tolerance in these animals.

Kawano et al. 2009. Hypoglycemic effect of aspalathin, a Rooibos tea component from Aspalathus linearis, in type 2 diabetic model db/db mice. Phytomedicine, 16(5), pp. 437-43. Available here.