12 November 2007
The first clinical trial to determine the potential health benefits of Rooibos in adults at risk of heart disease was announced in Cape Town on Friday 9 November 2007. More than 150 guests, including several science journalists and health writers, attended South Africa’s first ever Rooibos Science Café at the MTN ScienCentre in Canal Walk Mall. The event was hosted by the South African Rooibos Council, a co-funder of some of the research projects.
The clinical trial on Rooibos is run by Dr Jeanine Marnewick, a senior researcher in the Antioxidant Research Group at the Cape Peninsula University of Technology. A panel of researchers joined Dr Marnewick to present their findings on Rooibos health research, based on work done in the laboratory. The presentations were followed by a lively discussion with the audience about Rooibos and health.
Dr Marnewick emphasised the following health benefits, already known and proven for Rooibos.
– It is naturally caffeine free;
– It has a low tannin content;
– It has a unique mix of antioxidants;
– It has powerful antioxidant and cancer-fighting properties;
– It protects living cells against oxidative stress;
– It can slow down the development of skin cancer.
To date Rooibos health research focused on laboratory work and animal studies. The challenge now is to verify these health benefits in people.
Dr Marnewick and her team decided to focus on the potential benefit of Rooibos in heart disease, because it is one of the top five causes of death in South Africa. She outlined the clinical trial in which 41 adults are participating (including herself). This pioneering study focuses on the potential of Rooibos to protect against oxidative stress and inflammation associated with the development of heart disease in people. Each participant in the trial has one or more risk factors for developing heart disease, but not at a level requiring medication. Examples of these risk factors include raised serum cholesterol levels, pre-hypertension, overweight/obesity, inactive lifestyle or a family history of coronary heart disease.
During a 16-week period participants had to follow a restricted diet to exclude other antioxidants as far as possible. Their food and drink intake, as well as blood test results, were closely monitored during the trial. During a key part of the study the participants drank six cups of Rooibos per day. At other times they drank mainly water and beverages without significant antioxidant content. The researchers will now compare their test results for these different periods. Results are expected by mid 2008.
Rooibos health research at the MRC
In her presentation on research about the antimutagenic (cancer-fighting) properties of Rooibos, Dr Kareemah Gamieldien of the Medical Research Council (MRC) also elaborated on the extensive range of anecdotal evidence about the health benefits of Rooibos. These include that Rooibos is an effective antidote for vomiting, stomach cramps, lack of appetite and chronic restlessness. Many people also believe in the anti-ageing, anti-viral, anti-inflammatory and anti-allergic properties of Rooibos. She told the audience how she bathes her own baby daughter in Rooibos tea, because she found that it helped to soothe and relieve skin conditions, including eczema, but this local knowledge must still be proven in the lab.
MRC researchers already have evidence confirming that Rooibos protects against DNA damage and oxidative damage in living cells, and that Rooibos can significantly reduce the number and size of skin tumours. Their current research focuses on the ability of Rooibos to slow down and possibly treat skin cancer and cancer of the oesophagus. So far they have confirmed that traditional and green Rooibos can significantly reduce the number and size of papillomas (cancerous growths) in laboratory rats. They also grow human skin and oesophageal cancer cells in the laboratory and have found that that Rooibos inhibits cancer by interfering with the energy production in cancer cells, thereby slowing down the growth of these cells. The overall results show that green Rooibos is an even more powerful anti-cancer agent than traditional Rooibos. Based on these encouraging results, the team is now working on a Rooibos-based skin product to treat skin cancer.
What happens to Rooibos in the body?
Debora van der Merwe, a doctoral student in Food Science at Stellenbosch University, presented her research on what happens to the active ingredients of Rooibos in the body and why it is important to know?
She explained that increasingly sophisticated consumers and international markets require the anecdotal evidence about the health benefits of Rooibos to be backed up by scientific evidence. They are therefore focusing on finding out whether the antioxidants in Rooibos are absorbed, and whether they are metabolised (or changed) in the body. Metabolism can make these active compounds more effective or less effective as antioxidants, depending on the changes that take place. If the antioxidants are not absorbed, they cannot contribute to antioxidant activity in the body.
Rooibos contains a rare phenolic compound, called aspalathin. To date, aspalathin has only been found in Rooibos, contributing to its uniqueness. Aspalathin is a potent antioxidant in test tube studies, but the team is now looking for evidence of its antioxidant activity in the body. Her research to date already showed that aspalathin can be metabolised by the liver. This research will form the basis of future trials investigating the importance of aspalathin as a health promoting compound.
The science café concluded with a session where the audience could engage with the researchers and debate some questions around the health benefits of Rooibos. For this session, two senior researchers with years of Rooibos research to their credit joined the panel. They were Professor Wentzel Gelderblom of the MRC and Professor Lizette Joubert of the Agricultural Research Council. Some of the key points from the Q&A session:
– While the antioxidant activity of Rooibos may be lower than that of black tea, Rooibos has the significant health advantage of being naturally caffeine free.
– Because Rooibos is low in tannin compared to black tea, it does not bind iron to the same extent as black tea. Some more research is needed to determine the extent to which the polyphenols in Rooibos may also bind iron.
– Research abroad showed that Rooibos can protect the liver and is recommended for people with chronic liver problems. More research is needed on its possible anti-inflammatory and anti-viral properties.
– There is no conclusive evidence yet about whether adding milk to Rooibos tea will affect its antioxidant activity in the body. Researchers investigating this issue for black tea found varying results.
The Rooibos Science Café is an initiative of the South African Rooibos Council to make research on the health benefits of Rooibos widely accessible. The Council co-funds some of the research on behalf of its industry members. Funding also comes from CANSA, the Medical Research Council, the Agricultural Research Council and the National Research Foundation in South Africa.
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South African Rooibos Council
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