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Research Findings

Rooibos Research Around the World

Rooibos Research Around the World


Research studies in vitro (in a controlled laboratory environment) and in vivo (in live animals) help to understand and verify the health promoting properties of Rooibos. Clinical trials are necessary to confirm these health benefits for people. After years of laboratory and animal work on Rooibos in South Africa and around the world, the first clinical Rooibos trials in adults got underway in 2007, in Cape Town.

In their laboratory and animal studies, researchers focus on demonstrating that Rooibos indeed delivers desired biological activity such as antioxidant activity, antimutagenic activity etc. They explore the precise mechanisms whereby the active ingredients in Rooibos work, the structure of these compounds and how these antioxidants behave in different environments. Many research groups around the world have published articles on Rooibos since the 1960’s.

Can Rooibos prevent heart disease? The first human clinical intervention trial with adults at risk of developing heart disease started in June 2007 at the Cape Peninsula University of Technology (CPUT), South Africa. The study is led by Dr Jeanine Marnewick, with collaborators at CPUT, University of Cape Town, University of Stellenbosch, North-West University and the Medical Research Council. The project is co-funded by the SA Rooibos Council as well as THRIP (Technology and Human Resouces for Industry Programme) of South Africa’s National Research Foundation.

Marnewick’s study focuses on the potential of Rooibos to protect against oxidative stress and inflammation associated with the development of heart disease. Oxidative stress is defined as an imbalance between oxidants and antioxidants, in favour of oxidants. An excess of these oxidants can damage important cellular components such as lipids, proteins and DNA, resulting in the development of several important degenerative diseases.

Men and women, aged 30 to 60, are included in the study. Each participant has one or more risk factors for heart disease, but not at a level requiring medication. Examples of the risk factors are raised serum cholesterol levels, pre-hypertension, overweight/obesity, inactive lifestyle or a family history of coronary heart disease. The food and drink intake, as well as blood test results, of the participants are closely monitored over a period of 14 weeks. During a key part of the study the participants will consume six cups of Rooibos per day, wherafter they will drink mainly water and no beverages with significant flavonoid content in order to compare the two different intervention periods. All participants will be given their results as a purpose of this study is to also bring awareness of possible health promoting properties of Rooibos to the public.

The research team working on Rooibos at the Medical Research Council has been investigating the effect of Rooibos on various kinds of cancer for several years. They are working with human cells in the laboratory as well as with live animals, mostly rats and mice. The Programme on Mycotoxins and Experimental Carcinogenesis (PROMEC) is lead by Dr Kareemah Gamieldien and Professor Wentzel Gelderblom. Professor Elizabeth Joubert of the Agricultural Research Council’s institute Infruitec-Nietvoorbij, Stellenbosch, is a key partner in most of these projects. The SA Rooibos Council as well as CANSA (The Cancer Association of South Africa) contributes to the research funding. Recent and ongoing studies at the MRC include:

Rooibos and skin cancer
Several studies showed that Rooibos effectively counteracts the development of skin cancer in mice by interfering with the process whereby the cancer develops. In a study of two groups of test mice with induced skin cancer, the one group’s skin was topically treated with Rooibos and honeybush extracts, while the other received no treatment. Those who were treated with these herbal extracts showed 70% fewer tumours. The tumours were also smaller and took longer to develop, compared to the untreated group. The antioxidant activity, as well as the anti-inflammatory properties of Rooibos, could be important in this case. The research team at the MRC is now investigating the possibilities of developing a “cosmeceutical” Rooibos product to treat skin cancers.

Rooibos and liver cancer
In a further study at the MRC rats that drank Rooibos (at a similar concentration that humans drink) had fewer and smaller pre-cancerous lesions in the liver than those who drank water. The inhibitory (slowing down) effects on the development and growth of cancer cells provided further proof that some ingredients in Rooibos could be important as agents to prevent cancer in people.

Effect of green Rooibos and other teas on oesophageal cancer in rats
This study showed that Rooibos significantly reduced the number and size of the cancerous papillomas in the oesophagus, probably as a result of its polyphenols (antioxidants) content.

Studies in human cancer cell lines
The study showed that green Rooibos significantly inhibited the growth of the cancer cells, but that traditional Rooibos also achieved this effect at a slightly lower rate. The research was done on cancer cells from human skin, liver, colon and oesophagus. Further research is looking at the mechanism whereby Rooibos inhibits the development of cancer, specifically the balance between cell growth and cell death.

Unknown cancer-fighting compounds in Rooibos
With this project researchers are trying to explain exactly how the different compounds in Rooibos are able to protect cells against oxidative stress and genetic damage caused by diseases. They have found an apparent unknown compound that seems to provide more or at least similar protection against DNA damage than the known antioxidants. They are busy with further sophisticated chemical and biological analysis of Rooibos’ compounds.

How Rooibos protects against cancer
Studies at the MRC shows that Rooibos reduces cancer-associated changes in animal cells by protecting cells against DNA damage, or mutagenesis. Cancer develops in several steps and mutagenesis is one of the first steps. During mutagenesis the genetic material (or DNA) of a cell is changed because of excessive exposure to mutagens. Mutagens are physical or chemical agents that can change the DNA in the cell. Mutagens are found in cigarette smoke, sunlight or chemical substances such as hydrogen peroxide. This change in the DNA is known to be a major cause of cancer. Rooibos offers protection (or chemo-prevention) against these mutagens in more than one way:

  • It is a potent antioxidant, which means that it ‘scavenges’ free radicals. These are highly reactive molecules that are also produced during normal processes in the human body. Free radicals can damage the DNA of cells, but antioxidants bind to the free radicals and inactivate them before they can cause any damage.
  • Rooibos also increases the antioxidant status of the liver.
  • Rooibos stimulates the liver enzymes that break down carcinogens in the body. Ongoing exposure to carcinogens such as certain kinds of toxins and cigarette smoke, will eventually lead to cancer.

Rooibos research in progress at the MRC
Specific Rooibos studies currently underway at South Africa’s Medical Research Council include:

  • Interactions between toxins and Rooibos flavonoids in biological systems. Enquiries: Professor Wentzel Gelderblom.
  • Effect of Rooibos on colon cancer in vitro (cell lines in the laboratory) and in vivo (in animal models). Enquiries: Professor Wentzel Gelderblom.


Professor Elizabeth Joubert, a specialist researcher of the Agricultural Research Council’s institute at Infruitec-Nietvoorbij in Stellenbosch, is recognised around the world for her achievements and leadership in Rooibos research. She has pioneered this field in South Africa and has dedicated more than two decades to intensive investigations into processing of the plant, the product, its health benefits and commercial potential. Her groundbreaking work led to the successful market launch of several new Rooibos products, such as green and instant Rooibos. She is a world expert on antioxidants in Rooibos.

Another focus of Joubert and her research students is on the bio-availability of the unique antioxidant in Rooibos, namely aspalathin, to understand its potential beneficial value. For an antioxidant to benefit the human body, it must be absorbed by the body. It is therefore important to find out how effectively the body can use aspalathin. Joubert emphasises that laboratory-based research on the antioxidants in Rooibos can only measure the activity of these substances outside of the body. Only human clinical trials can tell us whether the specific antioxidants are absorbed, metabolised and effectively used inside the body. She hopes that future research will also make it possible for researchers to recommend how much Rooibos is needed to produce a measurable benefit.


Several research groups around the world have invested time and money in investigating the health benefits of Rooibos, resulting in a steady increase in the number of Rooibos research articles in the international scientific literature in the past 10 to 15 years.

The Japanese research fraternity has taken an especially keen interest in the health-boosting properties of Rooibos and published a number of research reports since 1990. More recently, some interesting findings have been reported from Pakistan and Slovakia.

The product’s reported antioxidant properties and medicinal value have given Rooibos a great deal of credibility and exposure in health-conscious markets abroad. Most of the studies to date have been done on laboratory animals, such as rats.

Key findings reported include:

Rooibos and brain tissue
Rats given free access to Rooibos from the age of 3 to 24 months had far less oxidative damage in brains compared to rats that drank plain water. This could possibly open the door for the treatment of Alzheimer’s with Rooibos.

Rooibos and immune systems
Researchers have shown that Rooibos promotes the production of antibodies when immune systems are challenged either in vitro or in vivo. This could also open up a new area of exploration regarding Rooibos.

Rooibos’ anti viral properties
Rooibos delays the recurrence of herpes simplex virus in humans. There is still a huge potential for future research into the anti-viral properties of Rooibos.

Rooibos skin deep
Some Rooibos studies have shown Rooibos inhibits (slows down) certain inflammatory skin diseases and makes the skin less sensitive to damage from the sun.

Rooibos and liver disease
A team of researchers in the Slovak Republic investigated the therapeutic value of Rooibos in an rat model concluded that the consumption of Rooibos as a rich source of natural antioxidants could be recommended as a readily available, safe and effective hepatoprotector (a substance to help protect the liver) in patients with liver diseases. Their findings were published in the Journal of Physiology Research in 2004.

Rooibos and cancer research abroad
Laboratory studies (in vitro) have shown that quercetin and luteolin, two of the flavonoids in Rooibos, are potent antioxidants that can cause cancer cells to “commit suicide” (a process referred to as apoptosis). Quercetin also slowed down tumour growth and prevented metastasis (spreading of the disease to other parts of the body) in study on cancer of the pancreas. Luteolin and quercetin slowed down the increase in thyroid and colon cancer cells, respectively. Although studies like these show quercetin and luteolin are strong antioxidants, they are only present in very low quantities in Rooibos. Researchers have not yet determined whether enough of either of these two flavonoids are present in Rooibos and absorbed by the body to have beneficial effects. Orientin, another abundant flavonoid in Rooibos, is a potent free radical scavenger. It halved the number of cancer-associated changes in human blood cells that have been exposed to radiation.

Medicinal use of Rooibos as bronchodilator, to lower blood pressure; and as agent to combat abdominal spasms and diarrhoea

In December 2006 researchers at the Aga Khan University Medical College in Kararachi, Pakistan published a study in the European Journal of Nutrition, concluding that there was a sound basis for the wide medicinal use of Rooibos. Their study focused on the possible effects of Rooibos to lower blood pressure, as well as its possible use as a bronchodilator and antispasmodic. The researchers worked on tissue preparations as well as animal models. In another research article, published in November 2006, researchers from the same university reported on the use of Rooibos to relieve abdominal spasms and diarrhoea. Based on animal models, they concluded that it was justified to use Rooibos to treat hyperactive gastrointestinal disorders.


“We are only beginning to uncover the chemopreventive properties of the unique South African herbal teas. Altough complex, it is an enticing research challenge for the future.”

Professor Wentzel Gelderblom

Medical Research Council

“I am very excited about the results obtained with Rooibos and our focus at the university will include substantiating anecdotal health claims of this herbal tea. Cumulative research results strongly suggest that the consumption of Rooibos may play an important role in the overall health of the South African population”

Dr Jeanine Marnewick
Cape Peninsula University of Technology

“Rooibos is just one of the products in the shopping basket containing antioxidants. It is, however, the only one containing aspalathin”.

Professor Elizabeth Joubert
Agricultural Research Council


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