Abstracted by Susan Sweeny Johnson, PhD, Biochem., August 6, 2010, from Debora Villano, Monia Pecorari , Maria Francesca Testa , Anna Raguzzini , Angelique Stalmach , Alan Crozier , Claudio Tubili , Mauro Serafini. Unfermented and fermented rooibos teas (Aspalathus linearis) increase plasma total antioxidant capacity in healthy humans. Food Chemistry 123 (2010) 679–683. doi:10.1016/j.foodchem.2010.05.032.
Rooibos tea is an herbal tea produced from the leaves of the South African plant, Aspalathus linearis. Traditional rooibos tea is produced by fermentation of the leaves and stems to obtain a red-brown infusion. In contrast, the unfermented rooibos tea (green rooibos) keeps oxidation to a minimum, better preserving antioxidant properties (1). Rooibos tea is a good source of unusual polyphenolic compounds (2).
The fermented and unfermented rooibos tea drinks used in this study had about a third of the antioxidant capacity (TRAP) of that of green tea and half of that of black tea (Camellia sinensis).
In this new study, 15 healthy participants ingested a prepared 500 mL drink of either water, fermented (red) rooibos tea or unfermented green rooibos tea. Both teas were prepared from tea extract powders. The participants’ blood was drawn at 0, 0.5, 1, 2, and 5 hours after ingestion and the total radical-trapping antioxidant potential (TRAP) of each blood sample was measured. After a two week wash out period, the same 15 people were given a different one of the three drinks. This was repeated again until each participant received each drink. The participants’ diets were carefully monitored throughout so that they consumed very few foods rich in antioxidants.
In the two tea groups, the antioxidant capacity of blood plasma (TRAP) increased significantly after 30 minutes, peaked at one hour and had returned to baseline by 5 hours. In the water group, no change in TRAP was observed over time. The maximum increase in TRAP for fermented tea was 6.6%; p < 0.05* compared to both baseline and control after one hour. The maximum increase in TRAP for unfermented tea was 2.9%; p < 0.01 with respect to control after one hour.
No changes in triglycerides, cholesterol or uric acid were observed during this study. Blood glucose did rise significantly to a maximum of 118+4 mg/dL at 30 minutes after both rooibos tea consumptions due to the presence of natural sugars in these teas.
Further studies comparing different varieties of fresh brewed rooibos teas appear to be warranted.
*p value is a measure of significance, p<0.05 is considered significant.
2. Krafczy, N., & Glomb, M. A. (2008). Characterization of phenolic compounds in rooibos tea. Journal of Agricultural and Food Chemistry, 56(9), 3368–3376