18 November 2008

When: Wednesday 26 November 2008, 10:00 for 10:30
Where: MTN ScienCentre, Canal Walk Mall, Cape Town

At the Rooibos Science Café on 26 November 2008, the preliminary findings of a clinical trial designed to determine whether Rooibos reduces the risk of heart disease development will be announced.

The trial (entitled “Modulation of blood oxidative stress markers by Rooibos in volunteers at risk for coronary heart disease”) was conducted by Dr Jeanine Marnewick, senior researcher at the Oxidative Stress Research Centre at Cape Peninsula University of Technology in Cape Town South Africa.

Forty men and women between 30 and 60 years old participated in the study. Each participant had two or more of the following cardiovascular disease risk factors: raised cholesterol, raised blood pressure, smoking, increased body mass index (BMI 20 – 35) and/or family history but did not need any oral medication for these conditions. The actual risk of each participant was determined using a calculation based on the well-known multi-year Framingham heart disease trial based on the patient’s age, gender, smoking status, blood pressure, triglycerides and HDL cholesterol (so-called “good cholesterol”). A person with two major risk factors has a risk of heart disease or stroke six times as great as a person with no risk factors. With three factors, the risk of cardiovascular disease is 20 times as great.

Participants had to drink six cups of Rooibos per day for six weeks, with the six cups spread across the day. In order to maintain a high degree of consistency, the preparation was standardized as 2% weight of dried Rooibos to volume of water. Each cup consisted of 200 ml boiling water added to one Rooibos tea bag, brewed for five minutes before drinking. Subjects drank the Rooibos with or without milk and/or sugar, as previous research on green and black teas (from the tea plant, Camellia sinensis) have demonstrated that milk does not eliminate the increase in plasma antioxidant activity in humans. 1 (The class of beneficial antioxidant chemicals found in Rooibos, black and green tea, and chocolate are called flavonoids; the flavonoids in Rooibos are different from those in tea and chocolate.) The six-cup amount of Rooibos consumed by participants in this trial was based on a human trial published in 2003 where the consumption of 6 cups of green tea increased the antioxidant capacity in the blood of human subjects.2

In a study of this type, it is important to modify the diet of participants in order to remove the consumption of other flavonoid-rich foods which may confuse the study results. To do this, the participants were requested to omit flavonoid-rich beverages (red wine, black or green tea and/or herbal teas, coffee, fruit juices, etc.) and to restrict flavonoid-rich foods (grape products, citrus fruits and their juices, berries and their juices, apples, onions, broccoli, etc.) from their diet for two
weeks before initiation of the intervention study. (Analysis of participants’ fasted blood samples taken after this period served as a baseline standard to help determine the extent of participant compliance with the study guidelines.)

Funding for this study came from the Cape Peninsula University of Technology, National Research Foundation (Technology and Human Resources for Industry – THRIP – project), and the South African Rooibos Council.

The results of this clinical trial will now be submitted for publication in a peer-reviewed journal. Also on the menu at the Rooibos Science Café is a presentation by Dr Carl Albrecht of CANSA on ten years of research on the anti-cancer properties of Rooibos, as well as a honeybush overview by Professor Lizette Joubert of the Agricultural Research Council.

Issued by the SA Rooibos Council

RSVP & enquiries: Marina Joubert, 083409 4254;

1. Leenen R, Roodenburg AJ, Tijburg LB, Wiseman SA. A single dose of tea with or without milk increases plasma antioxidant activity in humans. Eur J Clin Nutr. 2000;54(1):87-92.
2. Rietveld A, Wiseman S. Antioxidant effects of tea: evidence from human clinical trials. J Nutr. 2003;133(10):3285S-3292S

Issued by:
South African Rooibos Council
Enquiries: Soekie Snyman; 082-6497077; Email:
Interviews: Dr Jeanine L Marnewick, CPUT
Tel: 021-460 8314; Fax: 021-460 3193; Mobile: 082-8979352; Email:

Background information on Rooibos science and industry:

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