Medical Chronicle, January 2009, Page 8
By Greer van Zyl
The health benefits of Rooibos have been proclaimed for a number of years. Now in the first scientifically validated work on Rooibos and heart disease, researchers in the Cape Peninsula have found that the herbal tea is particularly effective at reducing oxidative damage to lipids, thus helping to prevent or slow down atherosclerosis.
The clinical trial by Dr Jeanine Marnewick, and her team at the Oxidative Stress Research Centre at the Cape Peninsula University of Technology, also generated the first human safety data in a controlled clinical trial envi- ronment, scientifically showing that short-term consumption of Rooibos is safe for the liver and kidneys, while keeping blood pressure and cholesterol levels in a normal range. The researchers measured the effect of Rooibos by examining two markers which are indicators of oxidative lipid damage, namely conjugated dienes (CDs) and malondialdehydes (MDAs). They found a decrease of nearly 35% in CDs in the blood of the Rooibos-drinking participants and a 50% decrease in MDAs. Oxidative damage in lipids is regarded as an important step in the development of atherosclerosis. CDs are formed during the early stages of oxidation, while MDAs are oxidation end products of polyunsaturated fatty acids that cause defects in protein synthesis and enzyme inactivation in human cells.
Patients with coronary artery disease usually have a higher MDA level than normal. Forty men and women aged between 30 and 60 years, each with two or more risk factors for developing heart disease, participated in the study by drinking six cups of Rooibos per day for six weeks. (The six-cup amount was determined by a trial of green tea consumption in 2003, which increased the antioxidant capac- ity in the blood of human subjects.1) The tea was brewed for five minutes before drinking, with or without milk and/or sugar. The participants were required to remove other flavonoid-rich foods from their diets to ensure the health effects could be ascribed to Rooibos only. “We also monitored oxidative stress by measuring the ratio of oxidised vs reduced glutathione (GSH) in the blood. Our results show a significant improvement – and therefore decreased risk of heart disease – in the study participants,” explained Dr Marnewick.
She is preparing to submit the work to an international peer-reviewed journal, and will pursue the research by examining genetic dif- ferences between the study participants to as- to Rooibos. In the field of cancer research, she will investigate how the bio-active compounds in Rooibos prevent DNA damage, and how Rooibos impacts on stress levels by measuring changes in cortisol in the blood.
Mientjie Mouton, director of the SA Rooibos Council’s product research portfolio, hopes the results of the study will help increase the relevance of Rooibos as a safe and affordable way to reduce heart disease in SA. “We are committed to investing in world- class research in order to verify where and how Rooibos is most effective and how people can benefit from this unique South African product,” she said during the launch of the results at the Rooibos Science Café in Cape Town. Head of research of the Cancer Associa- tion of SA (CANSA), Dr Carl Albrecht, also presented 10 years of research done with the Medical Research Council on the anti-cancer properties of Rooibos which was funded by CANSA to the tune of R1m. “Indications are strong that Rooibos may also have anti-cancer properties due to the rais- ing of GSH which has been shown to protect against cancer. Rooibos doubled the GSH levels in the participants of the heart disease study,” he told Medical Chronicle. Funding for the heart disease study came from the Cape Peninsula University of Technology, the National Research Foundation, and the SA Rooibos Council.
1. Rietveld A, Wiseman S. Antioxidant effects of tea: evidence from human clinical trials.